Researchers at City of Hope and beyond increasingly believe that cancer is not a single, united enemy to fight. Instead, the tumor cells that are felled and killed by chemotherapy and radiation are just the easier targets — the more vulnerable components of cancer. Behind them, quiet and ready to grow back after treatment, remain the hardy survivors.

Many scientists call them cancer stem cells.

FOREVER YOUNG
Normal, healthy stem cells are key to the cellular renewal humans need to stay alive and thrive.

After blood donation or blood loss from an accident, the body must replenish its blood cells. After a sunburn, damaged skin cells must be replaced. Even daily living eventually wears out most cells, which are swept away and swapped for more vigorous ones. Stem cells spur this rejuvenation.

Two types of stem cells have received considerable attention: embryonic stem cells and adult stem cells.

Embryonic stem cells are like blank slates: They can divide and produce any and all of the more than 200 different cell types in the human body. The inner mass of a five-day-old human embryo contains about 30 to 40 of these cells, which are the ancestors of all the human body’s cells in the years to come.

But stem cells are not just for embryos. Adults and children have stem cells, too. These are called adult stem cells, and they are more specialized than embryonic stem cells. Most of these cells can differentiate into a variety of cells within a certain family. For example, certain stem cells can give rise only to the types of cells that make up blood; others can only create nerve cells.

Because of the way stem cells divide, they not only create specialized cells, but they also create exact copies of themselves. That means they can truly renew themselves and create cells that are forever young.

This constant self-renewal is great for healthy cells and a healthy body, but self-renewal strays into dangerous territory if the seemingly immortal cell is cancerous. And that possibility is exactly what scientists grapple with today.

LURKING BEHIND LEUKEMIA
Ravi Bhatia, M.D., chief of the Division of Hematopoietic Stem Cell and Leukemia Research, has seen leukemia strike many patients. Although modern treatments beat back the disease, it frequently returns. He believes leukemia stem cells are to blame.

“Within leukemia, there is a certain population of cells that give rise to other leukemia cells,” Bhatia said. These are defective, abnormal stem cells that not only appear to produce cancerous cells, but also duplicate themselves, becoming cancer factories.

Scientists raised the possibility of a leukemia stem cell about 20 years ago, and despite doubts, research by Canadian scientist John Dick, Ph.D., in the 1990s finally verified it, Bhatia said. First came Dick’s discovery of a cancerous stem cell in a patient with acute myeloid leukemia; then came discoveries of stem cells in other leukemias, as well as breast, pancreatic, head and neck, and other cancers.

As Bhatia explained, leukemia happens when the blood cell creation process breaks down. Production of abnormal “leukemic” blood cells outpaces the creation of healthy blood cells. The overabundance of leukemia cells can crowd the bone marrow, allowing no space for healthy blood cells to grow or pump out defective white blood cells, which can render the immune system ineffective against infection.

Leukemia, Bhatia said, may very well depend on leukemia stem cells to keep itself going, even though only one in every 10,000 leukemia cells is believed to be a leukemia stem cell.

“There is the possibility that if there were no leukemia stem cells, then any spontaneous production of leukemic cells could not be sustained or grow and develop into full-blown leukemia,” said Bhatia, because cancer stem cells fuel the process.

Cancer stem cells also explain the incomplete success of chemotherapy. Chemotherapy battles cancer because it seizes on a central characteristic of the disease: Cancer cells divide, grow and proliferate — quickly.

Traditional chemotherapies specifically target and kill fast-growing cells, which is why chemotherapies can shrink tumors and kill spreading cells. It is also why chemotherapy kills other healthy cells that happen to grow quickly such as those in hair follicles and the intestinal lining, causing the familiar side effects of cancer treatment.

But many cancers return after chemotherapy, and they may return more aggressively.

“It’s the average cancer cell that divides very fast. Leukemia stem cells are usually quiescent, which means that they are not very active,” said Takahiro Maeda, M.D., Ph.D., assistant professor in the Division of Hematopoietic Stem Cell and Leukemia Research. “They can sit around not doing anything until they get a signal that they need to produce more cells.”

That means leukemia stem cells may survive chemotherapy unscathed and remain ready to produce more leukemia cells. The ability to evade chemotherapy by lying dormant makes leukemia stem cells an important area for research.

“Current standard treatment for hematological malignancies like leukemia and lymphoma can eradicate most cancer cells, but they do not target the cancer stem cells that can give rise to new cancer cells and eventual recurrence of the malignancy,” Maeda said.

STEMMING THE TIDE
Researchers at City of Hope are taking many different approaches to understanding cancer stem cells.  Bhatia’s investigations focus on specific receptors in cancer cells that help them divide and grow.

His studies show that the cancer drug Gleevec works against chronic myelogenous leukemia, or CML, by blocking a specific protein receptor that many of those cancer cells use to function. Although Gleevec kills mature CML cells, leukemia stem cells survive.  Often, when they develop into mature leukemia cells, they become resistant to Gleevec.

Bhatia found, though, that adding another new type of drug to the mix seems to cause the leukemia stem cells to self-destruct.

“Our studies so far are encouraging, and we have identified multiple targets that play a role in leukemia stem cell survival and replication,” said Bhatia. “The challenge is to find out which targets are more relevant to controlling or eliminating those stem cells.”

Bhatia and colleagues opened a phase I clinical trial in June to study their new strategy.

Even with more than 20 years of research data that support the existence of leukemia stem cells, scientific debate still continues about the role cancer stem cells actually play in cancer development — and even whether stem cells exist in all types of cancer.

And some scientists ask: What makes a cancer stem cell a cancer stem cell, rather than just a cancer cell that is resistant to chemotherapy? Researcher Margarita Gutova, M.D., Ph.D., has some answers.

“Cancer stem cells in different tumors will have similar qualities.

They will be resistant to chemotherapy, they will demonstrate stem cell-like properties of replication and they will be only a very small population of cells within the tumor,” said Gutova, senior research fellow in the Department of Hematology & Hematopoietic Cell Transplantation. “But they will have differences as well: different genes that are crucial to their functioning, different methods of operation and different behaviors.”

Gutova is researching possible lung cancer stem cells and breast cancer stem cells. She found that the most aggressive form of lung cancer, which is resistant to most chemotherapies, shows high activity of a gene named uPAR. She found a similar set of cells in breast cancer.

“This high level of uPAR activity is similar across many types of tumors,” said Gutova.

“Finding a way to target uPAR may help in multiple cancers, but each type of tumor may have a more effective target that is specific to that tumor.”

Similarities to healthy stem cells also raise more basic questions about the origin of cancer stem cells.

Are they healthy stem cells that somehow get their genetic wires crossed and begin generating cancer cells instead of healthy cells? Or do they start out as normal cancer cells, but then are somehow transformed into immortal cells that produce other cancer cells and refuse to die off? Which comes first, the cancer or the cancer stem cell?

Researchers are still looking for answers.

FROM ALL DIRECTIONS
In the meantime, Maeda knows patients with blood cancers cannot wait, so he is pushing to unlock some of the secrets of these stem cells in his lab.

Maeda’s research focuses on lymphoma and acute leukemia, both of which affect white blood cells. He is investigating a gene that helps in the production of a specific white blood cell important to a healthy immune system. Called leukemia/lymphoma-related factor, or LRF, the same gene is also highly active in lymphoma, which makes it an oncogene, a gene that can be tied directly to the development of cancer.

“We are currently looking to understand how LRF works in a normal, healthy hematopoietic [blood] stem cell,” said Maeda.  “If we can understand the difference between healthy expression and oncogene expression, perhaps we can find a target to help us either turn off the cancer stem cell or even turn it back into a healthy, functioning stem cell.”

Yanhong Shi, Ph.D., assistant professor of neurosciences, is conducting similar research into neural stem cells and a protein called TLX that blocks these cells from differentiating into specialized neuron cells. Neurons are cells of the brain and nervous system.

That same TLX protein is found in a small population of brain tumor (glioma) cells that, not surprisingly, demonstrate stem cell-like qualities and are presumably resistant to chemotherapy, as well.

“We are trying to characterize the impact of TLX in glioma cells,” said Shi. “We would like to determine whether TLX is an important target that we can develop new brain tumor therapies around.”

Shi is not alone at City of Hope in investigating stem cells’ role in brain and nervous system cancers. Qiang Lu, Ph.D., assistant professor of neurosciences, studies ephrin, a receptor molecule found in brain tumors, as well as pancreatic, colon and breast cancer, among others. Ephrin helps signal cells to move to specific locations and grow blood vessels; scientists suspect it also helps tumor cells to break off and spread to other areas in the body.

“We study how neural stem cells maintain themselves as stem cells. We found that ephrin is required, and its absence makes those stem cells differentiate into neurons,” said Lu. “Since it is also expressed in gliomas, targeting ephrin may help in treating the cancer. We are currently actively exploring this possibility.”

In another laboratory, Ya-Huei Kuo, Ph.D., assistant professor in the Division of Hematopoietic Stem Cell and Leukemia Research, studies how functions of leukemia stem cells are regulated and sees potential in research into RNA interference. In that strategy, scientists engineer short fragments of genetic code to switch specific genes on or off to treat cancer. Whatever the strategy, Kuo and her colleagues all share a single desire: weeding out the seeds of cancer and finding better treatments for the disease.

“My ultimate goal is to find a cure, and the best way to do that is to understand how cancer develops, understand the role of cancer stem cells, and use that knowledge to design a better treatment,” said Kuo. “Much of my work so far has been about seeing how we get cancer. I would also like to see if we can go back and maybe change the cancer stem cell.  Hopefully, we can.”

ILLUSTRATIONS: MARCO MARELLA

Key to stopping this trend are those who are supporting critical advances against the disease. The Leslie and Susan Gonda (Goldschmied) Foundation has provided a $20 million gift to support construction of an expansion of the 41,000-square-foot Leslie & Susan Gonda (Goldschmied) Diabetes & Genetic Research Center, which houses City of Hope’s comprehensive diabetes research and treatment programs. The new, four-story addition will house areas for programs that integrate research into diabetes, metabolic disease and other related conditions.

“City of Hope has played a seminal role in the research and treatment of diabetes, a disease that affects millions of Americans,” said Michael A. Friedman, M.D., president and chief executive officer of City of Hope. “This visionary gift from the Leslie and Susan Gonda (Goldschmied) Foundation will accelerate City of Hope’s efforts to advance diabetes treatment through innovative clinical and basic science research and explore promising scientific approaches that could potentially lead to a cure.”

About 20.8 million children and adults in the United States, or 7 percent of the population, have diabetes, according to the American Diabetes Association. While about 14.6 million of those have been diagnosed, another 6.2 million people are unaware that they have the disease.

Leslie and Susan Gonda

“We are deeply grateful to the Leslie and Susan Gonda (Goldschmied) Foundation for its generous and longstanding support of the diabetes program at City of Hope,” said Fouad R. Kandeel, M.D., Ph.D., director of the Department of Diabetes, Endocrinology & Metabolism at City of Hope. “Establishment of the islet transplant program would not have been possible without the initial support provided by Leslie and Susan Gonda.

“This most recent contribution from the Gonda (Goldschmied) Foundation will provide a critical clean-room facility and laboratory space needed to speed the translation of islet and stem cell research advances from the lab to the patient,” he added. “This gift is certain to have a significant impact on the future of diabetes care.”

City of Hope scientists have made profound strides in diabetes research and treatment. In the 1940s, the late Rachmiel Levine, Ph.D., described insulin’s role in stimulating the movement of glucose into cells and discovered that type 2 diabetes is related to a defect in this mechanism, a condition called ”insulin resistance.” In the late 1960s, Samuel Rahbar, M.D., Ph.D., recognized the usefulness of hemoglobin-A1c measurement as a marker for blood glucose control in those with diabetes. In 1995, Barry Forman, M.D., Ph.D., discovered how certain molecules can regulate receptors involved in glucose metabolism, leading to the development of important drugs that are now Food and Drug Administration approved to treat type 2 diabetes. And, perhaps most significantly, in 1978, Arthur Riggs, Ph.D., and Keiichi Itakura, Ph.D., genetically engineered bacteria to effectively produce unlimited quantities of synthetic human insulin, which today is used by millions worldwide with diabetes.

Riggs, professor of biology and director emeritus of Beckman Research Institute, believes City of Hope will continue making discoveries that will influence diabetes care. “This gift will help us maintain momentum toward becoming the top center in Southern California and among the national leaders for research in diabetes and metabolic disease,” he said.

Today, City of Hope researchers are investigating islet cell transplantation, a treatment in which insulin-producing cells called islet cells are transplanted from a donor pancreas into patients with diabetes to produce insulin. City of Hope is one of only seven islet cell resource centers funded by the National Institutes of Health. The institution hosts the Southern California Islet Cell Consortium, an integrated effort of multiple academic and transplant institutions that coordinate efforts in islet cell transplantation. In 2006, City of Hope was designated as a Juvenile Diabetes Research Foundation islet cell transplant center.

Since 2004, City of Hope has performed 27 islet cell transplants. In fact, in 2004 and 2005, City of Hope performed the most islet cell transplants in the nation.

“City of Hope’s diabetes research program is an outstanding example of visionary work in a truly collaborative atmosphere,” said Leslie Gonda. “I consider this an investment for future generations to benefit from this terrible disease that so many people suffer from.”

SUPPORT THAT PROVIDES SECOND CHANCES AT LIFE

Shelly Stevens’ new islet cells, transplanted at City of Hope, gave her a new lease on life.

Since the 41-year-old Chula Vista, Calif., resident was diagnosed with type 1 diabetes at age 2, she has faced many challenges. Because her body lacked “diabetic awareness,” she could not tell if her blood sugar was soaring or plunging. “The first time I’d know it was low was when I’d be on the floor having convulsions,” she said. At 21, she lost most of her vision due to diabetes complications.

Shelly Stevens

She shared her struggles with her older sister, Kim, who also had diabetes and died at age 35. “She had all the horror stories,” Stevens said. “Strokes, amputation.”

After a friend told her about the institution’s islet cell transplant program, supported through the Leslie and Susan Gonda (Goldschmied) Foundation, Stevens could not wait to sign up. “I came out of convulsions one day and literally crawled to the phone. My husband said, ‘What on earth are you doing?’ I said, ‘I’m calling City of Hope.’”

“I was desperate to get in,” she recalled. “Fortunately, they said I was perfect for the program.”

In February 2006, Stevens received her final transplant of donated cells, and four months later, she gave herself her last insulin injection. Since then, the woman who used to require 14 shots a day has not needed insulin at all.

“This is the miracle I’ve always dreamed of,” she said.

Now, Stevens tells everyone she meets with diabetes about City of Hope, including her brother, Matthew, who recently was diagnosed with the disease. “Everyone knows someone who has diabetes,” she said. “That’s why I’m so excited about this research.”

Once, there were only enforcers on the cancer scene. These heavy hitters still do most of the work in eradicating cancer: Chemotherapy treatments kill cells, radiation therapy weakens and destroys cancer, and surgery removes tumors. Many tumors get around enforcers, eventually claiming lives. Fortunately, secret agents emerging from a field of biology known as epigenetics are now on the scene. Using a different approach, these drugs coax cells into revitalizing their own defenses against cancer.

Where it all began

Epigenetics-based drugs are now routinely tested as cancer therapies at City of Hope, which is only appropriate. The modern science of epigenetics was practically founded there.

In 1975, a young City of Hope scientist named Arthur Riggs, Ph.D., published a historic study proposing that a chemical process called methylation switched genes on and off. That idea stimulated three decades of research culminating in cancer-fighting treatments in the pipeline today.

“Epigenetics” sounds complex, but the idea is simple. Genes are the body’s cookbook — bits of DNA that hold the recipes for proteins that make the body work. Genes can be inactivated by proteins that literally sit on them. (“Epi” comes from the Greek word for “on”).

Complex organisms like humans need strategies to muffle genes. All cells contain pretty much the same DNA, whether they are nerve cells or liver cells, for example. A nerve cell, though, does not need to use certain genes that a liver cell does; nor does a liver cell need certain genes critical to nerve cells. So cells often pack away useless DNA, first by tagging it with a small chemical called a methyl group and then wrapping it into a dormant form.

But sometimes, the wrong genes get stored away. “Good genes” known as tumor suppressors — which survey cells for DNA damage and control unruly cell division — can mistakenly get methylated and silenced. That happens in almost all cancer cells. Researchers hope that drugs based in epigenetics — the new class of secret-agent drugs — can cajole cells into unpacking and reactivating these dormant genes.

Stopping the silence

Jump-starting mistakenly silenced genes in a cancer cell is certainly possible. Unlike irreversible DNA damage caused by radiation or chemicals, epigenetically silenced genes are not usually damaged. Hidden away often lies a perfectly intact tumor suppressor gene that could fight cancer. One way that investigational epigenetic drugs may get tumor suppressors to resume their protective activity is to clear away the molecules smothering the gene.

The epigenetic drug vorinostat (or Zolinza) blocks enzymes called histone deacetylases (HDACs), which pack DNA into a tight, inactive coil, like a Slinky toy. Then, with HDACs out of the picture, coiled DNA can relax and open, allowing tumor suppressor genes to express themselves again. This approach has proven effective: Vorinostat has won Food and Drug Administration approval to treat cutaneous T-cell lymphoma.

Encouraged by that success, Mark Kirschbaum, M.D., director of new drug development for the Division of Hematology & Hematopoietic Cell Transplantation, is leading clinical trials of epigenetics-based drugs against blood cancers, including a phase II trial pitting vorinostat against non-Hodgkin’s lymphoma and a phase I trial teaming it with a DNA methylation-blocking drug to treat acute myelogenous leukemia.

He also is joining with other investigators to test these drugs’ effects on other types of cancer.

“The progress made by patients in our phase I and II trials is evidence that reversing the epigenetic silencing trick that tumors use to keep themselves growing may assist, or even replace, chemotherapy in many different tumors, especially blood cancers,” said Kirschbaum. “We are certainly seeing happy patients as a result.”

He and other investigators also recently published a study of the remarkable effect of the drug valproic acid, which works similarly to vorinostat, in treating a 64-year-old patient with
large B–cell lymphoma. Her disease, which had resisted other chemotherapies, went into complete remission a few months after she began valproic acid treatment, and it has remained in remission for more than a year.

Kirschbaum finds epigenetics-based therapies promising for older patients whose disease resists traditional chemotherapy. “These less toxic, and perhaps more effective, drugs are filling a need in the older population,” Kirschbaum said.

An epigenetic master switch

Among enforcer drugs, some highly effective chemotherapies shut off a single damaged, or mutant, gene that causes cancer. In contrast, epigenetics-based drugs switch on genes, often several at a time.

“In many cancers, DNA methylation is totally dysregulated,” or faulty, said Thehang Luu, M.D., a City of Hope medical oncologist specializing in breast cancer. In cancer cells, areas of DNA that control gene expression tend to be tagged with too many methyl groups, which can silence tumor suppression genes and activate cancer genes. “We are trying to establish therapies to upregulate, or remove layers from, silenced and methylated genes,” said Luu.

Given the success of epigenetics-based therapies in other cancers, Luu is testing the effects of vorinostat on breast cancer. She was principal investigator of a study in which disease stabilized in about a third of the patients treated with vorinostat. Stabilized disease means cancer is neither growing nor shrinking. “That is encouraging, because we saw minimal side effects,” she explained. “Now, we will combine this drug with other types of chemotherapy to see if we get a better result.”

Edward Newman, Ph.D., associate professor in molecular medicine, is evaluating an epigenetics-based drug that blocks DNA methylation in a phase I clinical trial. He
agrees that epigenetics-based therapies work in a unique way. “You might think of switching cancer genes off and on, like you turn on one light switch,” he said, “but what we are doing with epigenetics-based drugs right now is throwing the master breaker for the whole house.”

”Lighting up” so many genes at the same time may sound risky, but it could be what makes these drugs effective partners for traditional chemotherapy. One phase II clinical trial at City of Hope draws on this idea. That trial pairs vorinostat with cell-killing chemotherapies against non–small cell lung cancer, which accounts for 80 percent of all lung cancers. In the trial, led by Marianna Koczywas, M.D., assistant professor in the Division of Medical Oncology & Therapeutics Research and the Thoracic/Lung Cancer Program, patients will start vorinostat alone for a few days before beginning cell-killing chemotherapy. For some reason, vorinostat may make cancer cells more vulnerable to eradication through chemotherapy.

This represents a badly needed new battle plan against lung tumors, the most deadly cancer. “In lung cancer, the standard of care is not acceptable — most patients are diagnosed with advanced disease, and the five–year survival rate is only about 15 percent,” said Karen Reckamp, M.D., assistant professor in the Thoracic/Lung Cancer Program. “What we were doing was not good enough.”

Double-teaming leukemia

Other City of Hope investigators will treat leukemia with similar combination therapies.Wen Yong Chen, Ph.D., assistant professor in the Division of Biology, is partnering with Ravi Bhatia, M.D., who directs the Department of Hemotopoietic Stem Cell and Leukemia Research, to try to reverse the effects of epigenetic silencing of tumor suppressor genes in chronic myelogenous leukemia (CML). The V Foundation recently awarded the pair a $600,000 three-year grant to support the work.

Their project ties into another much-touted drug called Gleevec, also called imatinib. Gleevec is a major cancer success story that works by blocking an enzyme that makes cells turn cancerous and multiply. Unfortunately, some patients stop responding to Gleevec after a while. When this happens, their disease progresses.

Chen and Bhatia believe that epigenetics plays a key role in resistance to Gleevec, through a protein that interferes with tumor suppressors. “If we find that this protein isa factor during imatinib treatment, we could possibly devise strategies to block it,” said Chen.

Bhatia will see whether a drug that blocks that protein can kill CML stem cells in the lab. If adding that drug to Gleevec packs more punch against CML stem cells than does Gleevec alone, it would support using that drug in a clinical trial, he said.

Other targets

Today, the most prominent target of epigenetics-based drugs is cancer. However, epigenetic changes also occur in type II diabetes. A study of Swedish families suggests that those changes may be passed down through generations. It reported that people whose grandfathers overate as children tended to show higher incidence of diabetes, while those whose grandfathers ate less had a decreased risk of cardiovascular disease.

How can an ancestor’s lifestyle affect disease risk in family members in later generations? Epigenetics may help explain it.

A grandpa may have lingered too long at the smorgasbord as a boy, and his overeating possibly influenced how his diabetes-related genes were methylated — and how active they were. The grandpa’s children and grandchildren not only inherited his DNA (his genetics) but also his DNA methylation pattern (his epigenetics).

While grandpa’s eating habits were appropriate for his active lifestyle, they do not fit today’s more sedentary one. So two generations later, his grandchildren may be overweight and predisposed to diabetes.

This implies that cells have a memory for the dietary habits of one’s ancestors, which has serious consequences on one’s health. Even though this idea in theory relieves people somewhat from responsibility for their own welfare, it remains to be proven.

A person’s diet certainly affects the packaging and expression of their own genes. One City of Hope researcher investigating how this happens in diabetes is Rama Natarajan, Ph.D., professor in the Department of Diabetes, Endocrinology & Metabolism. She carefully analyzed inflammatory and immune cells grown in high-glucose conditions (like those seen in diabetes) and found epigenetic changes in some diabetes-related genes. And she has seen similar changes in cells from diabetic patients.

Researchers also know that DNA methylation changes can be passed on when a cell divides — another idea proposed by Riggs in 1975. But whether epigenetic changes associated with diabetes can be inherited across generations is not known.

These inherited changes may explain why obesity seems to run in families, but this needs to be confirmed, Natarajan said. “The field of epigenetics in diabetes is in its infancy,” she said. “But it is a research area of growing interest, since — especially in the case of type 2 diabetes — there are several similarities with cancer, particularly with respect to the effects of environment and heredity on disease.”

The right place at the right time

Scientific rewards are a long time coming. For the epigenetic research his pioneering hypothesis stimulated starting in the 1970s, Riggs, professor of biology and emeritus director of City of Hope’s Beckman Research Institute, was elected in 2006 to the National Academy of Sciences, one of the highest honors an American scientist can receive..

Since his revolutionary 1975 paper, Riggs has published about 150 more, most analyzing how DNA methylation occurs in normal cells. He worked with Gerd Pfeifer, Ph.D., chair of the Division of Biology, who analyzes DNA methylation associated with lung cancer. Their studies could lead not only to more effective cancer treatments, but also to lung cancer markers offering much-needed early detection methods.

To Riggs, the emergence of epigenetic drugs from laboratories at City of Hope is simply logical. “The basic science I did at City of Hope in the early years of modern epigenetics was conducted in the right biomedical setting. It is gratifying, but not surprising, to see that epigenetics now is being used to detect and treat cancer,” he said. “In the right place, knowledge-based research done to discover and understand new things often leads to exciting practical applications.”

For cancer patients, those practical applications may mean many more years of life.

Facing the deadly plans of an evil villain, comic-book characters rarely defend the planet as everyday humans. Instead, they call on special powers that turn them into hardnosed crime-fighters.

As it is when the body must defend against disease. Sometimes the immune system simply lacks the brawn to fight illness on its own. That is when physicians draw on the power of vaccines — injections that can give the immune system a much-needed boost.

The goal of a vaccine — whether it aims to prevent an infectious disease such as polio or means to stop cancer — is to motivate cells of the immune system into getting so mad that they rise up and drive out harmful intruders.

Fortunately, cells usually do a pretty good job without prompting by an inoculation. Most of the time, when immune cells such as B-cells or T-cells spot an unwanted invader like a flu virus or a tumor cell, they mount a toxic response and neutralize it.

But every now and then — either because invaders are overpowering or because disease or therapy weakens the immune system — people need the backup boost of a vaccine.

Researchers worldwide are on a quest to harness the power of vaccines, and City of Hope scientists are advancing the movement on two fronts: vaccines against cancer and against diseases related to cancer treatment. They also are taking lessons learned from such research and applying them to other diseases, extending the reach of their work.

From friend to foe

The word “vaccine” often conjures up childhood memories of jabs in the arm against measles, smallpox and other infectious diseases, and for good reason. Vaccines began as protective measures, stoking the immune system to be ready to mount an offensive if exposed to specific infectious attackers.

Today, two approved vaccines related to cancer do just that. Meant for healthy people, a hepatitis B vaccine defends against a virus that can cause liver cancer, and another new vaccine called Gardisil protects against certain viruses that can cause cancer of the cervix, throat and other areas.

But a newer, developing area in cancer vaccine research targets people who already have cancer. Called therapeutic vaccines, these injections aim to strengthen the body’s defenses against existing tumors, keep tumors from returning or eliminate cancer cells that remain after other cancer treatments.

City of Hope surgical oncologist Joshua Ellenhorn, M.D., has his eye on one such therapeutic vaccine.

A surgeon also trained in immunology, Ellenhorn is developing a vaccine to target cells that express high levels of a protein known as p53.

Normally, p53 plays a protective role as a tumor suppressor gene and actually blocks the out-of-control growth seen in many cancers.

But a mutation or damage to p53, which occurs in numerous cancers, deals cells a double-whammy: Not only do the cells lose cancer protection normally offered by the gene, but the defective p53 protein actually promotes tumor cell growth.

“Mutations in p53 that disable its ability to function as a tumor suppressor result in accumulation of this protein within cells,” said Ellenhorn. “About 40 to 50 percent of all malignancies overexpress mutant p53. In breast cancers, it is seen in approximately 40 percent of all malignancies — same with colon, prostate and pancreatic cancers.”

Ellenhorn has created a vaccine he hopes will eradicate human tumors that express high levels of mutant forms of p53. Interestingly, it is based on the prototype cowpox or “vaccinia” virus that English physician Edward Jenner famously pioneered 200 years ago as a vaccination against smallpox.

Together with Don Diamond, Ph.D., director of City of Hope’s Laboratory of Vaccine Research, Ellenhorn has used a similar technique for a potential p53 vaccine — but with a few modern twists.

Just like Jenner, the City of Hope researchers are using cowpox virus to fire up the immune system. But in today’s modern version, the scientists tweaked the cowpox virus’ genetic code and plugged a copy of the p53 gene into it.

Then they injected that special vaccine — along with other therapies that also rev up immune response — into mice that had cancerous tumors. The result: Most of the tumors grew smaller or disappeared altogether.

Because the engineered cowpox virus is foreign, it gets the attention of the immune system, Ellenhorn explained. “This then stimulates T- and B-cells, which are redirected toward disintegrating and attacking tumors that overexpress p53.”

These findings show the vaccine can kill tumors in mice. In a next step, the researchers successfully created and tested a human form of the vaccine in mice, and tests in human cells in the lab have shown promise, too.

Ellenhorn is confident that the vaccine will soon reach clinical trials. “Initially, the phase I trial will be in patients with advanced disease,” he said. “If the results are positive, we would take it to a group of patients in an earlier stage of the disease.”

The donor gives twice

Sometimes, the very therapies that help a patient fight cancer are so potent that they themselves are life threatening. Treatment with immunosuppressant drugs after bone marrow or organ transplant, for example, leaves transplant patients vulnerable to ordinary germs that lie dormant in healthy adults.

Several City of Hope researchers are devising vaccine therapies to encourage immune cells to fight these germs.

One such danger comes in the form of a herpes virus called cytomegalovirus, or CMV. About 50 to 80 percent of adults in the United States have been exposed to CMV, but it causes few symptoms in healthy individuals. In transplant patients with compromised immune systems, however, activated CMV may cause life-threatening pneumonia.

A team of City of Hope scientists led by Diamond has developed a vaccine to address that threat. But interestingly, care providers would administer the vaccine to the organ or bone marrow donor, not the recipient. They aim to transfer lifesaving CMV immunity — in addition to transplanted tissues — to the recipient.

According to Diamond, when the bone marrow transplantation program began at City of Hope in the 1970s, CMV infection was the main cause of most patient deaths. And although physicians have provided antiviral drugs with moderate success, the treatment sometimes can be difficult to deal with.

“The antiviral itself causes such adverse events, it probably is less positive than we first imagined,” said Diamond. “If we could prevent those, we would really be getting to a treatment that is head and shoulders above anything out there for cancer transplant.”

The result: saved lives.

Much like the p53 vaccine, Diamond’s group designed the CMV vaccine as an altered form of the cowpox virus — but with genetic code from the CMV virus attached. When introduced into the body, the vaccine launches a chain of events that activates the donor’s immune system against CMV.

Results from lab research suggest the immunity would stay elevated after transplant, protecting the recipient.

The U.S. Food and Drug Administration recently approved the first human trial of the CMV vaccine developed by Diamond’s group. That trial began with the inoculation of the first volunteer, a City of Hope employee, in May of 2007. Volunteers’ overall health and responses to the inoculation will be monitored to evaluate vaccine safety.

John A. Zaia, M.D., professor and chair of the Division of Virology, is the principal investigator of the CMV phase I clinical trial. “This is the first vaccine developed at City of Hope that has been brought to clinical trial,” he said. “Hopefully, this signifies a new era in vaccine development here.”

Stephen J. Forman, M.D., Francis and Kathleen McNamara Distinguished Chair in Hematology and Hematopoietic Cell Transplantation, credits City of Hope for creating a research climate where basic researchers like Diamond and clinicians interact.

“We are the institute that understands this virus,” said Forman, clinical director of City of Hope’s Division of Cancer Immunotherapeutics & Tumor Immunology. “The original work identifying the signature viral immune proteins was done here in Don Diamond’s lab. That is the reason this work has been successful.”

Establishing garden-variety immunity

Viruses aren’t the only threats to immunocompromised patients. An innocent walk in a garden may expose them to spores of an ordinary, soil-dwelling fungus called Aspergillus fumigatus and cause a potentially fatal lung disease known as aspergillosis. Like CMV infection, Aspergillosis is no small threat.

According to City of Hope investigator James Ito, M.D., director of the Department of Infectious Diseases, the development of better antiviral drugs targeting other types of infection has left Aspergillus with an infamous distinction. “By default, the most devastating infections are now fungal infections,” he said. “They’ve always been around, but have moved up into first place now. In fact, Aspergillus is now the most deadly of all fungal infections.”

The gravity of the fungal threat is echoed by Markus Kalkum, Ph.D., Ito’s collaborator in developing an Aspergillus vaccine. “We all inhale several hundred Aspergillus spores a day, usually without any negative impact on our health,” said Kalkum. “However, inhalation of spores can prove fatal to bone marrow or organ transplant patients taking immunosuppressive drugs.”

In 2002, Ito and Joseph Lyons, Ph.D., a scientist in the Department of Infectious Diseases, took the first steps to create a vaccine when they inoculated mice with a
mix of pulverized Aspergillus proteins, treated the mice with immunosuppressants to mimic conditions of transplant patients, and then exposed mice to a lethal dose of fungal spores. The results were dramatic. “A hundred percent of the mice died if we didn’t vaccinate them,” reported Ito, “but a significant number of them survived if we did.”

Now, with Kalkum joining the team, the researchers have zeroed in on the specific protein in that fungal vaccine “soup” that stimulates the immune response. When they vaccinated mice with just that protein, it, like the mix, protected mice against the infectious Aspergillus.

The investigators’ next goal is to establish antifungal immunity in immunodeficient humans. Currently, they are identifying antibodies that humans make to mold proteins to determine which fungal proteins stimulate that response. Although several years away, once a vaccine is developed, it will likely be administered like the CMV vaccine to the bone marrow donor and not the recipient.

From idea to reality

Moving from an idea to a therapy is a long haul, one that is appreciated by Simon Lacey, Ph.D., associate research scientist in the Division of Virology. Lacey, who also worked on the CMV project, is conducting experiments to determine whether a vaccine might work against another virus reactivated in immunosuppressed patients: BK virus, or BKV for short.

More than 80 percent of American adults are infected with BKV, making it even more prevalent than CMV. Like those with CMV, few with BKV show overt signs of disease. However, reactivation of the virus in immunocompromised patients following organ transplant may cause an irritation of the lining of the bladder known as cystitis, even to the point of bleeding.

After a kidney transplant, potent immunosuppressants required to block rejection of the new kidney may activate the BKV — sometimes with serious consequences. “Approximately 30 percent of transplant patients show signs of elevated virus levels, 5 percent develop signs of kidney disease, and about half of those people then lose the kidney,” explained Lacey.

When viral levels rise, a physician’s only choice is to drop patients’ doses of immunosuppressive drugs. “It’s a constant balancing act,” said Lacey. “The only approach is aggressively monitoring the virus in the blood.”

Together with transplant surgeon Jennifer Singer, M.D., of the Department of Urology at UCLA, Lacey is now tracking blood and urine samples from kidney transplant patients. If they can better understand how certain patients’ immune systems successfully fight BKV infection, they might be able to create ways to predict which patients are likely to develop the disease. Their studies also could lay the groundwork for vaccine development.

So far, Lacey has shown that vaccination with a portion of BKV can get immune cells to react in mice. The first steps in humans are promising, as well. But he cautions that results are preliminary. “The logical next step is to either develop a good drug conveying a type of immunotherapy, or to develop a vaccine to protect people,” said Lacey. “But you can’t do any of those without a better idea of what you are facing.”

Poised for the long haul

Vaccine development is clearly not for quitters. Devising strategies that encourage the immune system to take a stand against invaders is long, hard work. Gardisil, the much-publicized vaccine against cervical cancer that targets human papillomavirus, took more than 20 years of development before becoming available last year.

But City of Hope excels in translational research, a process that moves laboratory science into new modes of prevention, diagnosis and treatment — and then takes lessons learned from patients back into the lab. This gives the institution a nimble advantage in areas such as successful vaccine development, according to Diamond. “City of Hope is unique among American research centers in that its philosophy is to encourage cooperation among basic scientists and physicians that leads to something tangible,” he said.

Forman echoes that optimism. “We have all the right people collected at City of Hope — the patients, the lab expertise and the doctors,” he said. “There are few other places like this anywhere.”

Yet just as people inherit their parents’ physical features, they also inherit their less-noticeable genetic characteristics. Human DNA preserves the blueprints for astounding capabilities developed over hundreds of generations, such as sight, walking upright and higher reasoning. However, those inherited genes may also include some that are not so helpful — and some that may be downright harmful — including genes that increase the risk of cancer and other diseases.

Today, researchers at City of Hope are investigating just how these not-so-obvious genes increase cancer risk. They also seek ways to identify who is at increased risk of disease so they can take steps to prevent it or catch it early. Some also look beyond the genetic make-up of individuals — looking instead at bigger groups — to learn how cultural, genetic and social differences may contribute to risk and survival among various ethnic populations.

What links within

Each cell in the human body contains 25,000 to 35,000 genes. Genes line up in structures called chromosomes. The nucleus of human cells contains 23 pairs of chromosomes — half inherited from the mother, the other half from the father.

When genes are altered or mutated, they may cause disease. Sometimes parents pass along altered forms of genes to their children. Sickle cell anemia, for example, arises in children due to genetic mutations inherited from their parents.

Other mutations in genes come not from parents, but from genetic hiccups that can happen during the course of a lifetime. Genes can become altered due to exposures to toxins in the environment, such as asbestos, chemicals and second-hand smoke, for example. Personal lifestyle habits and other factors, including sun exposure, lack of exercise and a poor diet, also may contribute.

Possessing an inherited mutation is like a baseball player starting out with one strike against him before he even steps up to the plate. Sometimes it does not take many more mutations to advance a cell to a cancerous stage. More than 100 known genes are thought to increase a person’s risk of cancer or other diseases, including breast, ovarian and colon cancer and endocrine disorders, said Theodore Krontiris, M.D., Ph.D., executive vice president of Medical and Scientific Affairs, director of City of Hope Comprehensive Cancer Center and professor of Molecular Medicine.

Mutations can lead to cancer in a few ways. They can prevent the repair of DNA damage, which can then lead to a buildup of defects, some of which overstimulate cell growth. Some turn off controls for cell maturation, while others keep damaged cells from preventively self-destructing before they go awry. Each cancer has its own combination of mutations that give rise to it and keep it going — even cancers that are found in the same tissue type.

Krontiris and his colleagues have studied genes associated with an increased risk of prostate cancer by looking at the DNA from men with prostate cancer whose brothers also had the disease. They identified a new mutation that appears to only increase the risk of prostate cancer when a man inherits the mutation from both parents. The finding could eventually lead to new tests for prostate cancer risk.

That mutation may illuminate the significance of introns, small sections of DNA that were thought to be extra, unused genetic bits — a sort of filler in the genetic code. Krontiris and his colleagues are studying introns to understand how they affect the function of active genes around them. They are finding that introns act indirectly and might contribute to cancer, diabetes, hypertension and neurodegenerative disorders.

“It’s still too early to understand how they work,” Krontiris said. “While we think we know what the genes do, we’re not sure how gene variations cause elevated risks of cancer.”

Most people who develop cancer do not have an inherited genetic mutation. Instead, they accumulate mutations from environmental exposures, lifestyle and the passing of years. But for the 5 to 10 percent of people who have genes known to increase cancer risk, the odds can loom particularly large.

“While the risk of getting cancer from having inherited cancer genes for the total population is small, the risk for people who carry these genes is much higher,” said Jeffrey Weitzel, M.D., director of the Department of Clinical Cancer Genetics and associate professor in the Division of Medical Oncology & Therapeutics Research. For example, women without a genetic predisposition for breast cancer have about a 2 percent risk of developing cancer by age 50. But, women who carry a mutation in one of the BRCA genes — mutations known to be linked to breast and ovarian malignancy — have a 20 percent risk of developing breast cancer by age 40. That rises to a 50 percent chance by age 50, and as much as an 85 percent risk over their entire lifetimes.

“That points out the need to identify who is carrying the genes, so they may be screened and consider preventive therapies to help reduce their risk,” Weitzel added.

The family tree

Genetic screening is not for everyone, noted Weitzel. Experts say prime candidates for the testing include those who have several close relatives with a certain type of cancer, as well as women or men who develop a gender-specific cancer but who do not have enough relatives of that gender to determine if the disease runs in the family.

Testing even after cancer diagnosis can help patients prevent future cancers, Weitzel said. In a study published in 2003, he and his colleagues found that when women newly diagnosed with breast cancer underwent genetic testing to determine their inherited risk, they were more likely to select treatment that reflected that risk. The seven women in the study whose tests indicated they had a high risk of recurrence all chose to have bilateral mastectomies rather than more conservative treatment.

“If a woman is a BRCA carrier, the chance she’ll develop another cancer in the next 10 years is 40 percent, and most women have no desire to go through surgery, radiation and chemotherapy again. It gives them a chance to practice both therapy and prevention,” Weitzel said. And if women who know their genetic risk share that information with family members, they can encourage family members who also may be at higher risk to be vigilant about getting screened, he added.

Recent research indicates that mutations in more than 500 genes may be involved in human cancers, and about 120 of them actually drive cancer development. According to cancer genome researchers, mutations in 1 percent of all human genes are linked to cancer. Of these, about 20 percent can be inherited, while the rest can be acquired through environmental or other exposures. (About 10 percent can either be inherited or acquired.) As researchers comb through the human genome, the list of known cancer-linked genes will continue to grow.

Garry Larson, Ph.D., associate research scientist in the Division of Molecular Medicine, Weitzel and others at City of Hope are working to develop tests for such gene mutations in breast cancer. By comparing genetic material from tumors from sisters with breast cancer, they hope to find more inherited breast cancer gene mutations.
These discoveries change lives.

When 45-year-old City of Hope breast cancer patient Merry Rogers was diagnosed with the disease, she did not believe family history could be to blame. Since her mother did not develop breast cancer, she thought, genetics could not be playing a role.

But Rogers later learned that her father’s mother and several other relatives

Most people who develop cancer do not have an inherited genetic mutation. Instead, they accumulate mutations from environmental exposures, lifestyle and the passing of years.
on her father’s side had died of breast cancer. She got tested for BRCA genes.

When results confirmed she had the BRCA1 gene mutation, she felt relieved.

“It sounds silly, but I was really happy to know that I had the gene, because then I could explain to myself why I got cancer,” Rogers said. She shared the results with her two sisters and brother, and encouraged them to be tested, as well.

“I’m happy because I think I’m leaving a legacy for my nephews, so that three or four generations from now, they can be more aware of the risk,” Rogers said.

Based on the results, she decided to have a more radical surgery to nearly eliminate her risk of breast cancer.
“I used to think that I’d die of cancer — that it would eventually come back,” she said. “Now I think I’d be really surprised if I got it again. I think I’ll live to be 90.”

Extended families

While parents contribute their offspring’s genetic traits, their race and ethnicity tie their children to those larger groups, too. Those ancestral histories can influence risk, as researchers have found that certain cancers occur more often or are more lethal in certain groups. Gene mutations that occurred early in the history of certain races and ethnic groups are passed on, so many members of those populations now carry them. 

For instance, studies show descendents of Ashkenazi Jews are more likely to carry BRCA gene mutations, which increase the risk of breast cancer in both women and men. Ashkenazi Jews trace their heritage to the medieval Jewish communities that lived near the Rhine river in Germany.
Weitzel’s lab also has found a previously unrecognized gene linked to people of Mexican descent that is a variation on the Jewish genes. He suspects its origins may stretch back to Jewish people who fled to Mexico during the Spanish Inquisition.

This finding may explain in part why certain Latinas are at higher risk of breast cancer, despite Latinas’ overall lower risk compared to whites.
Researchers found that 31 percent of Latinas with breast cancer who were screened between 1998 and 2004 at City of Hope had genetic mutations that increased their risk of breast cancer. Other races and ethnicities have different mutations that similarly increase the risk of breast cancer. 

Race and ethnicity also influence survival rates in patients with life-threatening diseases. Smita Bhatia, chair of the Division of Population Sciences and associate director of the Cancer Control and Population Sciences Program, is researching the influence of race and ethnicity, as well as socioeconomic status, on the survival of children treated for leukemia.
Eighty percent of children diagnosed with acute lymphoblastic leukemia — the most common form of childhood leukemia — live at least five years after treatment, depending on the severity of their disease. However, children in certain ethnic groups appear to have a better chance of surviving and avoiding recurrence than others. Children of Asian descent had the highest rates of survival at five years, with no relapse in 75 percent of those studied, followed by whites and Latinos. Blacks had the lowest rates of survival without relapse, at about 62 percent.

The difference, Bhatia said, might be genetic or physiologic. Social factors also come into play. Possible reasons include differences in the way children of different ethnicities respond to drugs, varying levels of access to health care that could lead to later-stage diagnoses, or differences in how well the children and their parents are able to comply with taking medication and receiving care. Researchers must perform rigorous studies to separate true genetic factors from environmental and social ones.

Bhatia recently began a five-year study to determine which of those factors influence survival. She will analyze blood drawn from children and young adults up to age 22 to see how well their bodies metabolize therapeutic drugs. In addition, researchers will survey children’s pill-taking habits and provide “smart” pill bottles that record each time they are opened to record compliance.

“It’s important for the children to take their drugs as prescribed. If they don’t, it really increases their chance of recurrence,” Bhatia said. “But if they’re taking them, and it’s not helping them as much, this will help us to understand what is going on physically to create that difference.”

Understanding those connections between social, family and genetic predispositions to cancer and other diseases is the first step in finding better ways of treating them, and eventually preventing them.