Cancer and Blood Diseases Institute

Using a method that starts with virtual computer modeling, Cincinnati Children's researcher Yi Zheng, PhD, and his co-workers design lead drugs that block overactive cancer-causing proteins and help chase cancer cells out of their hiding places in the body. "Our lab figures out which proteins are signalling too much, and what we can do to return them to normal," said Zheng. "Turns out, if you can return the signalling to normal, you can freeze transformation (switching from a regular to cancerous cell) and make the cancer cells less invasive."

One drug candidate that Zheng has already licensed to a pharmaceutical company blocks a protein called Rac, that can malfunction and send too many chemical signals to other proteins in the cell. The drug candidate is called NSC23766, and it is considered a "lead" drug because it works against leukemia, lymphoma, prostate cancer and lung cancer in mice — killing a significant percentage of cancer cells and delaying cancer onset — but it still needs to be tested in humans.

Other drugs that Zheng is developing might be able to chase cancer cells out of hiding places in the body called niches, and this could be the key to making cancer curable. A niche harbors a particular type of cancer cell, and the conditions in that niche protect the cancer cell from being killed by traditional methods. For example, chemotherapy might not get to leukemia cells hiding in the bone marrow. "The hypothesis is that cells hiding in their niche repopulate after chemotherapy and cause the cancer again," he said. "That's why instead of a cure, people often talk about two-year, five-year, or ten-year survival."

Zheng hopes to solve the niche problem by blocking Rac and its relatives (which are all part of what's called the "Rho-GTPase" family). They play a large role not only in cell signalling, they also regulate cell adhesion. If Zheng's drugs can prevent cells from sticking to other cells, he might be able push cancer cells out of their niche. "By targeting Rho-GTPase, the cells loosen up, blood moves, the leukemia cells might be pushed out of the bone marrow," he said. Once a cell leaves its niche, conventional chemotherapy can kill it and eradicate the cancer for good. There could be a chance to cure the cancer rather than just stave it off.

To target Rho-GTPases, Zheng starts by modeling millions of molecules on the computer to see if the shapes fit into the target he hopes to block, like puzzle pieces. "We know the structure of our target molecule, and how it is activated," he said. "Then we use computer-based virtual screening to match millions of compounds to see if any fit. If one molecule fits into the right spot, like a glove, then it goes on the short list."

The short list of about 50 molecules is then tested physically in the lab to see if they bind in real life like they did on the computer screen. "We try to reveal so-called crystal structures with X-ray crystallography (a method for viewing the real 3-D shape of the molecule locked into the protein)." Based on the structure, the lead drug can be modified to look more like a real drug. Zheng also tests the efficacy of the molecule in a real cell, and then in an animal. "Here you also need luck, because not all compounds will be able to enter the cell and act as they do in a test tube," he said.

In addition to NSC23766, which has already passed these tests, Zheng and his colleagues are currently working to achieve a crystal structure for a Rho inhibitor that looks promising based on cellular tests. "We carry out the pre-clinical work in my lab," he said. "After that, we hope to collaborate with pharmaceutical companies and clinical researchers to develop it into trials in humans."

By inhibiting a certain enzyme, researchers might be able to dramatically improve results and decrease the side effects of radiation therapy for cancer treatment. The enzyme, called telomerase, is found in 85 percent of cancerous cells but is not found in normal mature cells.

“Telomerase allows cancer cells to continue to replicate indefinitely. By inhibiting it, we could make radiation treatment more effective in lower doses," said Rachid Drissi, PhD, a researcher in the Division of Hematology / Oncology at Cincinnati Children’s Hospital Medical Center.

Normal cells stop multiplying when the ends of their chromosomes get too short — these end pieces, called telomeres, act like a cap on the DNA. Think of tape on a shoelace that keeps the threads from unraveling. “Usually, as telomeres get to a certain critically short length, the cell will stop dividing,” said Drissi. “This is a natural process of cellular aging.” But when telomerase is present, it allows the cell to continue to divide beyond this natural stopping point by maintaining telomere length.

A telomerase inhibitor combined with radiation therapy works like a one-two punch, because radiation therapy damages the DNA enough to make it stop replicating. The telomerase inhibitor makes cells stop replicating when their telomeres are worn down. Also, cells with short telomeres become much more sensitive to radiation.

Ongoing clinical trials in adults use a telomerase inhibitor to treat breast cancer and multiple myeloma in adults. Now Drissi is working with clinical researcher Maryam Fouladi, MD, MSc, and others in the Division of Hematology / Oncology to develop a pediatric clinical trial using telomerase inhibitors. As a first step to test the efficacy of these inhibitors, Drissi is also assessing telomere length and telomerase levels in tumors and blood from children with an aggressive form of brain tumor. The goal is to determine the role of telomerase in predicting patient outcome and response to therapy in this vulnerable patient population.

“Brain tumors are difficult to treat, and these patients face tough choices between curing the cancer and living with the effects of radiation,” said Drissi. “Working in a research institution that is part of a hospital gives you a sense of how important the lab work really is.”

Over the last four decades, the cure rate for acute lymphocytic leukemia has improved remarkably: it’s gone from 4 percent to 80 percent in the first world. Still, the disease claims about 10,000 young lives each year. Cincinnati Children’s researcher Jose Cancelas, MD, PhD, is working to close that gap, and he says that a specific protein is responsible for most cases that have a darker prognosis. "Most childhood acute lymphocytic leukemia can be cured, except for in kids that have this protein," he said. The protein is called p190 BCR-ABL, and Cancelas is working out a multiple-pronged attack on it.

Cancelas is not the first researcher to look at p190 BCR-ABL. In fact, Novartis and Bristol-Myers have developed drugs that block p190 BCR-ABL, increasing survival for patients with the protein from 10 percent to 30 percent. "But this is not good enough," said Cancelas. "The problem is that the protein is very big and complex, and these drugs only block part of it."

When drugs target a specific site, the protein can adapt to the new drug and work around it, much in the way that bacteria become resistant to antibiotics. "The cells responsible for the initiation of leukemia divide quickly, and mutations occur all the time," said Cancelas. "Cells with mutations that enable the protein to get around the drug survive, and pretty soon all of the remaining cells are resistant."

To prevent resistance, Cancelas works to block not only the p190 BCR-ABL protein, but also a cascade of other proteins that it activates to make the leukemia grow. This would be much harder for the leukemia cells to resist, since a single mutation couldn’t get around a variety of roadblocks at once. "If you target only one signalling pathway, it’s not useful because of mutations or other forms of resistance," said Cancelas, "if you target other parts you have the ability to eradicate the disease."

Already, Cancelas’ colleague, Yi Zheng, PhD has developed a drug that blocks one of the proteins much farther along in that cascade. This protein is called RAC. "When you block RAC, you can see that you can block leukemia formation," said Cancelas. "We’ve seen that in vitro [test tubes] and in vivo [mice]. It worked very well."

But Cancelas and Zheng are still working to target proteins a bit farther up in the cascade — somewhere between P190 BCR-ABL and RAC — so that the drug will have fewer toxic effects. "RAC is found in every cell, and it plays a role in a variety of processes — not just leukemia," said Cancelas. "If we can target more specific proteins higher up in the cascade, we might be more specific and therefore less toxic."

Cancelas and his team are in a good position to develop more targeted drugs because they have genetically engineered mice to elucidate the pathway, and they have an efficient drug to knock out RAC, which will be of great help in revealing other aspects of the cascade. "We suspect a group of proteins that activate RAC," said Cancelas. "We are now trying to elucidate which ones are most important so we can target them too."

By targeting a couple of small, key pieces of genetic material, researchers have discovered a way to block the activity of the cancerous cell that generates some forms of acute myeloid leukemia. This could lead to better treatments that have fewer side effects. “It seems we have found the Achilles’ heel of this form of cancer,” said H. Leighton Grimes, PhD, who works in the Division of Immunobiology at Cincinnati Children’s. “We were very surprised that by targeting these very small things, we could halt the leukemia.”

The discovery began in a roundabout way. Last year, Grimes developed the first mouse model for a disease called severe congenital neutropenia. A curious aspect of the disease is that 20 percent of patients also develop acute myeloid leukemia. Although attempts to reproduce the disease in mice had failed in the past, Grimes’s lab was successful when they mutated a gene called GFI1. “GFI1 represses other genes, so it’s like a light switch and it turns off the expression of the other genes,” he said.

With this new GFI1-deficient mouse model, a pathway to acute myeloid leukemia unfolded. Grimes found that GFI1 normally blocked the signals from other pieces of genetic material, called microRNAs. In certain types of acute myeloid leukemia, cancer formation seemed to hinge on the messages that two specific microRNAs were sending. “GFI1 is actively fighting to suppress these microRNAs,” said Grimes. “If we over-express GFI1 in cancerous cells, it suppresses the microRNAs and it suppresses transformation [from regular cells to cancerous cells].”

Even better, stopping the microRNAs stopped the cancer, even without forcing GFI1 expression. “We’ve developed small-molecule inhibitors of these microRNAs. What’s really interesting is that in mouse models of leukemia, in which each in vitro colony has the capacity to initiate leukemia in a recipient, the number of colonies is dramatically lower by getting rid of these microRNAs,” he said. “And the translation of that is if you treat the kids with these small-molecule inhibitors, you could eradicate the disease.”

Chemotherapy today targets both healthy and cancerous cells, causing a variety of side effects. But Grimes’s mice have not shown side effects from the microRNA inhibitors. “Taking our findings from the laboratory to the clinic will require years of testing,” said Grimes. “But we are excited by the prospect directly targeting the cancer in patients.”

When the herpes simplex virus contains a certain gene, it becomes very good at fighting cancer. That's according to a recent study done in part by researcher Timothy Cripe, MD, PhD, at Cincinnati Children's Hospital Medical Center. The study, published in the February 15 issue of Cancer Research, tested the herpes virus's ability to kill notoriously difficult tumors — neuroblastoma and peripheral nerve sheath tumors. When the virus was given an extra gene called "TIMP3," it killed a great deal of the cancer in human tissue samples and prolonged the lives of mice.

"This is not the first time that the herpes simplex virus has been used to kill cancer cells," said Cripe. "But by adding the TIMP3 gene, we were able to completely halt the growth of some tumors and in other cases make them shrink and even disappear."

Viruses are good vehicles for getting cancer-fighting genes into cells because they naturally insert their own genes into a cell after they enter the human body. Scientists can remove the disease-causing genes from a virus and add cancer-fighting genes, like the TIMP3 gene.

The TIMP3 gene works against tumors by reducing the tumor's ability to make new blood vessels (which tumors use to steal nutrients from the body), and by helping the virus to stay in the tumor longer. TIMP 3 also inhibits enzymes called "matrix metalloproteinases," known as MMPs. "MMPs are important in tumor growth because they degrade the tissue in between cancer cells, allowing the cancer to migrate and spread farther," said Cripe. "Also, they generate other proteins that help the cancer cells to grow."

Pharmaceutical companies have recently tested drugs that inhibit MMPs, but the results were not impressive, probably because the inhibitors were not able to concentrate enough in the tumor tissue to have any real effect. However, when genes in the cell are able to manufacture the inhibitor from the inside out, like in this trial, things seem to change. The mice with the TIMP3 gene-carrying virus lived almost four times longer than untreated mice, and more than twice as long as mice that got the virus without the gene.

The results are encouraging, but it will be some time before doctors can use this breed of virus to treat people. "It takes a long time to develop this kind of research into clinical trials," said Cripe. "And during that time, we may find something even better."

HPV and Cervical Cancer

Cervical cancer is the second most common cancer in women: it kills 230,000 people each year. That’s why Cincinnati Children’s researcher Susanne Wells, PhD is working to understand all of the factors that lead to it. "We know that cervical cancer is caused by a sexually transmitted virus, called human papillomavirus," said Wells. "There’s a vaccine to prevent infection, but it is not helpful once infection has occurred."

Though the HPV vaccine is now available to girls as young as 9 years of age, Wells hopes that her research will help provide better treatment for women who already have the virus, or who do not have access to the vaccine before it is too late. Fifty percent of people who are of reproductive age are estimated to have been exposed to HPV, and over 6.2 million new cases of HPV occur each year. Of the millions who get infected, most will not develop cancer. The trick is to pinpoint what causes certain women to be at risk.

"We do not understand exactly what makes a very small proportion of infected women progress to cancer over time," said Wells. "It is hard to make connections because it often takes decades for the cancer to appear." Wells studies the genetics of cervical cancer to better understand factors that determine the outcome of HPV infection. Human genes that influence the process could help diagnose the cancer early, or could even be targets for treatment.

The virus is also more likely to lead to cancer when it produces large amounts of two viral proteins called E6 and E7. "E6 and E7 are absolutely necessary for carcinogenesis," said Wells. "If you look carefully, the cancer will almost always express E6 and E7, and if you suppress those, the cancer will die." Using tissue samples in the lab, Wells studies how E6 and E7 contribute to cancer growth and viral amplification. "They block tumor suppressing genes which are normally needed to keep cell growth under control and prevent cancer," she said. "Suppressing E6 and E7 has not been easy as a clinical approach, but is promising as a cure."

One out of every 3,000 people has neurofibromatosis type 1. The disease can be disfiguring, cause learning disorders, and lead to tumors or leukemia that can be fatal. But in spite of its frequency and seriousness, the disease has not gotten the attention it deserves until recently. “The incidence of the disease is on par with cystic fibrosis and even Parkinson’s disease, which people hear about all the time,” said Cincinnati Children’s researcher Nancy Ratner, PhD. “And yet very few people, comparatively, work on this disorder. I think that for many years, so little was known about it that there was no way to make inroads.”

But that is beginning to change. Scientists already know that the disease is caused by problems with a gene called NF1. Ratner studies how the malfunctioning of this gene leads to one of the most dangerous symptoms of the disease: the formation of tumors, called neurofibromas, in the nerve tissue. These tumors can cause lumps under the skin, neurological problems, and can press on internal organs and become fatal. Because the tumors mingle with vital nerve tissue, they are often impossible to remove.

Ratner’s lab recently discovered that the timing of the NF1 gene mutation determines whether neurofibroma tumors will form. This discovery could help lead to future treatments. In a study published in the February issue of Cancer Cell, Ratner and her colleagues reported that if the NF1 gene mutated on day 12.5 of a mouse’s embryonic development, neurofibroma tumors formed. If the gene mutated at other times during development, tumors did not form. “If you know what the timing is of the mutation, you can identify the correct progenitor cell population, pull it out, and try to identify what’s wrong with it and therefore open treatment avenues,” said Ratner.

The discovery was made using the first successful neurofibromatosis 1 mouse model, a mouse that Ratner’s team genetically altered to mimic the disease that occurs in humans. She also leads an international microarray project, which is a collection of 200 samples from diseased human and mouse tumors and cells. Her team uses the samples to identify targets for new drugs that can be tested in the mouse model. “We are asking what pathways we can see that are abnormal, and then testing new drug candidates derived from those systems,” she said.

The Neurofibromatosis Center at Cincinnati Children’s recently received funding of $1 million per year from the National Institutes of Health, and another Cincinnati Children’s researcher, Timothy Cripe, MD, is currently running a pre-clinical therapeutics testing effort at the hospital funded by the Children’s Tumor Foundation. “People at Children’s – and internationally — really pull together,” said Ratner. “Right now there is no drug to treat this disease, but we are proposing ideas that could be turned into therapeutics in the future.” 

Over 80 percent of children diagnosed with cancer today will survive, but many of the life-saving methods used to treat the disease — such as radiation, surgery, and chemotherapy — may create new health problems of their own. That’s why researcher Stella M. Davies, MBBS, PhD, MRCP, at Cincinnati Children’s Hospital Medical Center, is working to understand unique health issues that affect the growing population of childhood cancer survivors, which has reached 250,000 in the United States alone. “It’s important that we study not just the immediate outcomes," said Davies, “but also the effect of treatment on the risk of later cancers, and on the function of important organs and overall health.”

Davies is director of the biological repository for the National Cancer Institute’s Childhood Cancer Survivor Study (CCSS). As the nation’s largest long-term effects program, CCSS collects a combination of medical records and biological data from 14,000 survivors originally diagnosed at 27 different medical institutions between 1970 and 1986. “We have collected almost 10,000 samples of DNA,” said Davies, who has been a member of the CCSS steering committee for 10 years. “We use the samples to study the role of certain genes in making patients more susceptible to late complications of cancer treatment.”

Childhood Cancer Survivor Study data has already been used in variety of research investigating late effects. Behavioral and social outcomes, stroke and premature menopause are just a few of the survivor issues that the data has helped to elucidate. Davies says that one clear result of the data is that cancer survivors have an increased risk of secondary cancer later in life. “CCSS data have been extraordinarily valuable in showing us that the most important side-effect of being treated for cancer is actually getting cancer at another site,” she said. By understanding the most common late effects of treatments, modern therapy can avoid some of the most severe problems and patients can take control over their health as they grow older.

Davies' own research also draws from the CCSS; she has used the data to investigate how certain genes contribute to secondary cancers correlated with obesity, particularly in girls who survive leukemia. Research shows that obesity is a major risk factor in developing secondary cancers, and many female leukemia survivors who received radiation in the brain struggle with weight gain. Davies is also looking at how genes play a role in the possibility of heart-related side-effects of treatment. “By looking at genetic factors, these studies allow us to start to consider the possibility of personalizing therapy to move ahead,” said Davies. “Survivors have benefited from this study because they now have a better knowledge of the screening that they need to protect themselves as they age.”

To keep pace with rapidly changing treatment plans, the CCSS team is currently generating a cohort of children treated in more recently. “The first CCSS cohort included people treated from 1970 to 1986, so we have survivors entering their mid-to-late fifties, thirty years after their treatment,” said Davies. “The new cohort will consist of people treated between 1986 and 1996, so we can look at the consequences of more modern regimens designed to reduce the side-effects.” 

Lung cancer causes one in every three cancer-related deaths. More than 400 people die of the disease every day, which is more than breast, prostate, melanoma, colon, liver and kidney cancers combined. Lung cancer is difficult to treat because it can silently progress for decades before symptoms develop. “One of the biggest problems is that patients only get symptoms when the cancer is at an advanced stage” said Cincinnati Children’s researcher Dr. Vrushank Davé. “In terms of treatment, it becomes very hard to target a specific molecule or a pathway, because it has gone on for so long by the time it is detected that myriad pathways are already involved.”

Davé wants to understand the initial change in a cell that causes lung cancer. By getting at the root of the cancer, his lab can develop methods for early detection. He can also develop better treatments.

Davé is especially interested in a protein called PTEN. “PTEN serves as a brake on cell growth and suppresses tumor growth,” said Davé. PTEN is responsible for keeping a cell survival molecule called a PI3 Kinase under control. When PTEN is missing, PI3 Kinase can run rampant, causing uncontrolled cell growth and cancer. Davé believes that the mutation of PTEN may be the molecular switch that causes lung cancer in many patients—and this mutation might occur up to 30 years before a patient is diagnosed. “Our research indicates that the mutation could occur in the teenage years, but the obvious symptoms of the cancer might not appear until the patient is much older and the cancer has progressed to advanced stages,” said Davé. He hopes that in the future, an annual bronchial swab could check to make sure that young predisposed patients — due to genetics or smoking — have not had this mutation. If it is found, researchers might be able to head off the cancer before it develops further and becomes impossible to cure.

By mutating PTEN in mice, Davé can create lung cancer within a few months. Not only does this lend credence to the idea that PTEN mutations are involved in lung cancer initiation in humans, it also gives him a tool for other avenues of research. His mutated mice develop lung cancer much faster than standard lab mice, which are usually exposed to carcinogenic chemicals in order to develop cancer over a much longer period of time.

Davé’s more efficient mouse models have allowed him to expand his research to learn more about cancer stem cells. Even after the cancer seems to be destroyed in a patient, quiescent populations of cancer stem cells can become active and cause the cancer to come back. “Removing most of the cancer without getting the stem cells is like removing weeds without removing the roots,” said Davé. A better understanding of cancer stem cells might allow researchers to treat cancer in the later stages and make it go away for good. “One of the major hallmarks of cancer stem cells is that they divide very slowly compared to normal cancer cells, and since they divide slowly they are resistant to treatment,” said Davé. Current treatments target cancer cells that are dividing.

There is currently no method for targeting a cancer stem cell in the lungs, but Davé and his colleague Yi Zheng have been trying to identify the cancer stem cells by meticulously noting unique characteristics from cells in mouse tumor tissue, and then returning them to a healthy mouse. If these re-introduced cells cause lung cancer in healthy mice, they know they have characterized true cancer stem cells.

Since PTEN is important in regulating the normal stem cell population required for tissue maintenance, Davé thinks there is a good chance that PTEN modulates cancer stem cells. “Gene profiling of lung cancer cells carrying the PTEN mutation has given us a good handle on identifying critical molecules that can be targeted for cancer therapy” said Davé. “If we are able to target lung cancer stem cells in patients, then even lung cancers in the late stages can be treated. We can design drugs to target the cancer stem cells, which will reduce the chance of cancer remission and significantly increase survival."

An ancient enzyme found in almost all life forms may hold the key to better treatments for brain tumors. The enzyme, called AMPK is found in organisms ranging from plants to worms to humans. It helps healthy cells survive stressful situations. But according to Cincinnati Children’s researcher Biplab Dasgupta, PhD, MS,, cancer cells also use the enzyme to survive inside dense tumors with little oxygen, and to weather the stresses of chemotherapy and radiation. He believes that understanding how cancer cells manipulate AMPK may lead to better brain tumor treatments.

“If we can prevent the cancer cells from recruiting AMPK, we might be able to break the cancer cells’ resistance to therapy,” said Dasgupta. Brain tumor treatment usually starts with surgery to remove as much of the tumor as possible, followed by radiation and some kind of toxic agent to kill the left over tumor cells. “Unfortunately, the cancer usually comes back after these treatments, because some of the cancer stem cells are able to survive these assaults,” said Dasgupta. He hopes that reducing the AMPK may make the tumor cells more vulnerable to attack.

Healthy cells activate AMPK when they undergo some kind of stress, such as increase of metabolic activity during exercise. The mechanism is complicated, but it has to do with the ratio of an energy-creating molecule called ATP to another molecule called AMP. “When the ATP to AMP ratio declines below the normal point, the AMP binds to the AMPK and makes it active,” said Dasgupta.

But in cancer cells, says Dasgupta, the mechanism is different. Cells can also activate AMPK by releasing hormones and growth factors. Cancer cells seem to favor this mechanism, and can use it to manipulate the AMPK to their advantage. “Mechanisms involving hormone or growth factor-mediated AMPK activation have little to do with the AMP to ATP ratio and most likely do not involve AMP binding,” said Dasgupta. Though there is one AMPK inhibitor currently available, it may not work against cancer because it only attacks the AMP-bound active enzyme. “We want to know more about hormone and growth factor-mediated AMPK activation in cells, and especially in cancer cells, so we can knock it out specifically,” he said.

Dasgupta has individually knocked out some of the different building blocks, or subunits, of AMPK in animal models. He is able to see what effect that has on the animal, and learn about the role of each subunit in the overall activity of the enzyme. This gives him leads for possible drug targets. It also teaches him about possible side effects of reducing the enzyme not only in cancer tissue, but also in healthy tissue. “We found that when we inhibit AMPK in slowly dividing cells, they are less affected, but highly proliferating cells are more affected, as are neural [brain] stem cells,” he said. “Also, certain regions of the brain are more affected when we knock out specific subunits of the enzyme. This led us to believe that the different subunits are differentially expressed in different organs and tissues and during different stages of our development form the embryo to the adult.”

Because AMPK is important for a variety of tissues in the body, further testing may indicate that any inhibitor Dasgupta eventually develops should be delivered directly to the tumor. He envisions a future combination therapy, perhaps with the inhibitor being administered by a pump or a wafer that is surgically inserted at the right time and place to make tumor cells more vulnerable to chemotherapy and radiation. “Our research has elucidated the importance of AMPK in healthy tissues, and it is clear that there would be side effects to inhibiting it,” said Dasgupta. “But gliomas are extremely tenacious and deadly tumors, and we hope that developing an inhibitor could help finally knock them out.”

People often have a hard time remembering to take their medications. This can lead to big problems for patients with leukemia, who often have to continue taking complicated pill regimens at home for up to 2 1/2 years after they finish their most intensive treatment at the hospital. “One common reason patients give for not taking their pills is that they have busy lifestyles and they forget,” said Dennis Drotar, PhD, director of the Center for Adherence Promotion and Self-Management at Cincinnati Children’s.

Drotar is currently leading a study that looks at treatment adherence in adolescents with acute lymphoblastic leukemia (ALL). The intervention comprises five hour-long sessions. “In the sessions, the family identifies what the major barriers are, and then brainstorms solutions with a therapist. The goal is to develop collaboration between the patient and the family,” said Drotar. Patients develop a written plan to help remember to take the medications. An electronically tagged pill bottle tells the researchers how frequently patients take their medications over the course of maintenance therapy, providing data on the usefulness of the intervention strategies.

Previous studies have shown that treatment adherence is tough for adolescents with ALL. In one of Drotar’s pilot studies of adolescents with ALL, a full 20-30 percent of patients did not show any metabolites in their blood from one of the primary drugs they were supposed to be taking. “We were amazed by that pilot study, because you would think that with a disease like this, 100 percent of patients would take medication,” said Drotar. “But in some ways, it could be that life takes over and you don’t think of yourself as a sick person.” Still, Drotar notes, forgetting to take medications for leukemia could be dangerous, and might lead to relapse. “The problem is that teenagers often think of themselves as less vulnerable than they really are,” he said. “There is often a mismatch between a parent’s perception of a child’s vulnerability and a child’s own perception of it. And that sometimes comes up in the sessions when the parents say they feel like they are nagging their child to take medication.”

Common strategies that come up in brainstorming sessions include building the medications into a daily routine, using pill boxes separated into days of the week, keeping track in writing and having written reminders, and anticipating some of the issues that will get in the way ahead of time so patients can avoid them. “One of the most important things is opening the line of communication between the parents and the child,” said Drotar.

The NIH-funded multi-site study began in 2008 and is expected to last for five years. Co-principal investigators include John Perentesis, MD, FAAP, director of the Oncology Program, and Alexander Vinks, PharmD, PhD, FCP, director of the Clinical Pharmacology Research Unit at Cincinnati Children’s.

Researchers at Cincinnati Children's Hospital Medical Center have found that the unique conditions that exist inside a person’s body may play a significant role in whether that person will develop one type of leukemia over another. The findings, published in the June 9 issue of Cancer Cell, focused on a particularly deadly form of leukemia caused by a gene mutation called a “mixed lineage leukemia translocation.” The researchers also discovered that certain compounds, called Rac inhibitors, specifically target leukemias caused by this MLL translocation and might be promising as a treatment.

MLL translocations happen when a fragment of chromosome 11 detaches and re-attaches to another chromosome. MLL translocations don’t always lead to the same type of leukemia: they cause about seven percent of all acute lymphoid leukemia cases, and about nine percent of all acute myeloid leukemia cases. In the past, researchers suspected that the type of leukemia that developed from MLL translocations just depended on where in the chromosome the translocation re-attached. “But in this paper, we use the translocation partner that usually causes myeloid leukemia in people, yet we can get exclusively lymphoid [leukemia] or exclusively myeloid leukemia, depending on what environment we expose the cells to,” said Cincinnati Children’s researcher James Mulloy, PhD.

For the study, Mulloy’s team inserted the cancer-causing MLL translocated genes into human cells and grafted these cells into a mouse. “You cannot make lymphoid leukemia in the mouse cells with these same gene fusions. But in this human cell background we can do it, and actually it’s much more biased toward lymphoid, which is interesting,” he said. Mulloy thinks that timing, and where the cell is in the normal cycle of blood cell formation, may play a larger role than previously thought. “Now we will be able to come to an understanding of how important the maturation of the cell is during the formation of MLL-related leukemia,” said Mulloy, “and if that’s playing a major role, it could impact therapy.” Targeting cells at crucial stages during leukemia cell maturation could make chemotherapy more successful and less toxic.

Mulloy’s team also used their mouse model grafted with human cells to test a type of drug called a “Rac inhibitor.” Rac is a protein that sends survival signals to cells, and it seems to play a crucial role in MLL-related leukemia. “MLL fusion proteins use a whole different signalling pathway to get to their end result of leukemia,” said Mulloy. “And the MLL’s really depend on Rac, they are really addicted to these signals.”

Rac signals are also important for normal cell functions, but Mulloy says that non-cancerous cells can often work around certain signals, while cancer cells cannot. “It’s strange, and we don’t know exactly why that is,” said Mulloy. “Probably, the cancer cells become really hardwired, really addicted to these signals and normal cells have much more flexibility. They can get around this stuff and use other pathways, but the cancer cells are stuck.” Rac inhibitors dramatically killed the cancer cells in a culture dish but had little effect on normal blood stem cells. The group is now testing the compound in the mouse model.

The Rac inhibitor looks promising, but Mulloy says he is most excited about the new human-grafted mouse model used in this study, because it will teach him more about what happens when certain genes mutate in humans. “Data that we have in the paper shows we are pretty close to the patient samples in terms of faithfulness to gene signalling pathways and gene signatures,” he said. “We are in the cell that is probably really targeted in people by this chromosomal translocation. So you have some exposure to a chemical, or whatever causes these translocations to happen, and we can duplicate that in the lab and learn about the precise signalling pathways. The model really works.”