Research on immune therapy for cancer turned a corner a few years ago, activating the field and resulting in treatment strategies that show real promise
BY DARRELL E. WARD
For more than 100 years doctors and researchers have poked, prodded and worked to coax the immune system into eliminating cancer. Then, in the last few years, scientists gained insights into the mechanisms of immune suppression. It was a breakthrough. It brought true clinical successes and energized the field. Today, immune therapy is one of the hottest areas of cancer research.
Clinically evident tumors must have avoided an effective immune response to have survived. But initial attempts to generate a therapeutic immune response to treat those tumors were not very successful because they attempted to induce immunity to cancer, says Mikhail Dikov, PhD, associate professor of Medical Oncology at Ohio State and member of the Translational Therapeutics Program at Ohio State’s Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James). “Then scientists discovered that, in addition to overactive mechanisms of immune induction, there are mechanisms that suppress the immune system in cancer patients.”
Therapies that reverse that suppression have been fruitful. “Patients with cancers that have been refractory to everything that’s been tried, such as non-small-cell lung cancer, are responding to these agents, which is unheard of,” says Gregory Lesinski, PhD, MPH, associate professor of Medical Oncology at Ohio State and a member of the OSUCCC – James Molecular Carcinogenesis and Chemoprevention Program. “The field is expanding rapidly.”
These suppressive modulators include the programmed cell death protein 1 (PD1), a T-cell receptor that inactivates T cells. Another is CTLA4 (cytotoxic T-lymphocyte-associated protein 4), a receptor on T cells that downregulates the immune system.
“New classes of drugs have been developed that inhibit both PD1 and CTLA4,” says William Carson III, MD, professor of Surgery at Ohio State and associate director for clinical research at the OSUCCC – James. “The success of these agents has given immune therapy a tremendous boost.
“Simply by giving a drug that stops one negative pathway on T cells, we’re seeing impressive shrinkage of tumors in melanoma and other cancers. The thinking is that those cases can also be treated with immune therapy,” Carson says.
A number of OSUCCC – James researchers are working to improve immune therapy for both solid tumors and hematologic malignancies. Some are investigating mechanisms of immune suppression and how to inhibit them. Others are developing peptide vaccines and inhibitors that generate anticancer antibody responses and induce immune memory to prevent recurrent disease. One of the vaccines is in clinical testing.
Cancer Versus the Immune System
Studies by Lesinski and his lab focus on how cancer alters the immune system and how to reverse immune suppression. He collaborates with OSUCCC – James clinical researchers studying immune therapies in clinical trials, and he leads translational mechanistic studies that could lead to new treatments.
One long-standing interest is the STAT3 protein. It is almost always turned on in cancer cells, where it promotes survival and inhibits death by apoptosis, Lesinski says. They’re learning it’s also important for the generation of myeloid-derived suppressor cells (MDSCs), a class of immune cells that curtail immune responses in cancer patients.
“Our evidence suggests that STAT3 promotes both tumor-cell survival and the downregulation of anticancer immune responses we see in patients with advanced cancer,” Lesinski says.
“We’re investigating whether inhibiting the STAT3 pathway might be a novel way to enhance immune therapy against cancer. We think that targeting STAT3 might have a dual effect, one on tumor cells and another that restores a degree of immune function that is lost with cancer.”
STAT3 inhibitors are themselves immunotherapy because immune cells rely on the STAT3 pathway, he notes. “We think that those inhibitors may have an underappreciated effect on the immune system.”
Similarly, his lab is exploring other pathways that are targeted in cancer cells and also used by immune cells. “Some of these inhibitors might in reality work by acting on immune cells rather than on tumor cells. We’re exploring that in-depth for several inhibitors.”
Dietary Immune Modulators
Lesinski’s lab is also investigating dietary and natural products as a novel means to reverse immune suppression or to prevent inflammatory immune changes that can produce smoldering chronic inflammation and then cancer.
One line of an NCI-supported study (CA169363) examines whether dietary soy might change the immune-cell profile in patients with prostate cancer. “We’ve learned that isolated soy components and diets enriched with soy can lead to immunologic changes,” Lesinski says. “Now we’re addressing whether a simple dietary intervention might alter the immune response in a way that favors anticancer immunity.”
In 2014, the researchers published findings from a study of black raspberry extracts and metabolites. It showed that these compounds might downregulate suppressive immune cells, in part through targeting STAT3.
“They block the ability of proinflammatory cytokines to expand the population of immune suppressive cells that are upregulated in cancer,” Lesinski says. The findings suggest that black raspberries might be a source of compounds for drugs that influence immune function or inhibit STAT3 pathways.
PD-1 is a receptor present on activated T cells and a potent mechanism of immune suppression. When tumor cells express one of PD-L’s two ligands—PD-L1 or PD-L2—tumor cells can shut down attacking T cells in the tumor microenvironment.
“Expression of PD-L1 on tumor cells is associated with poor prognosis in non-small-cell lung cancer and other tumor types,” says David P. Carbone, MD, PhD, professor of Medical Oncology and Barbara J. Bonner Chair in Lung Cancer Research at Ohio State. “But tumors expressing these ligands respond better to the new antibodies that target this pathway.”
Carbone chairs the steering committee for a 120-site, global phase III trial for the drug nivolumab, an anti-PD-1 monoclonal antibody. The trial (NCT02041533) compares this immune therapy with chemotherapy as first-line treatment for lung cancer.
“Anti-PD1 therapy by itself is proving to be extremely important,” Carbone says. “For decades, the paradigm in metastatic lung cancer has been platinum-based chemotherapy first line, with experimental treatments later on.
“But anti-PD1 immunotherapy has generated so much excitement and evidence of clinical benefit that it’s now being tested as first-line therapy, as the sole therapy. This raises the possibility that some lung cancer patients may have durable remissions for metastatic disease that last a long time with minimal toxicity and without ever having had chemotherapy. This large randomized trial compares nivolumab alone head to head with platinum-based doublet chemotherapy for patients with newly diagnosed metastatic lung cancer.
“This is fantastic by itself,” Carbone says, “but it also tells us that immunotherapy can work. Now we need to look at the science and figure out all the other processes that are involved in suppressing the immune response to develop new therapies and new combinations that might be even more effective or work in more people.”
Carbone and collaborator Mikhail Dikov are also investigating mechanism of immune suppression very different from PD-1. It involves an interesting pathway called Notch.
Notch is key for the development and differentiation of T cells and other immune cells, and for immune responses. When certain ligands bind with Notch receptors on T cells, it activates the cells and induces differentiation and immune responses.
Carbone and Dikov have shown that Notch signaling through a molecule called DLL1 is reduced in bone-marrow immune precursor cells both in patients and tumor-bearing animal models.
“We believe that activating the Notch signaling pathway offers a novel strategy for overcoming cancer-induced immune suppression,” Dikov says.
That conclusion is based on the findings of a 2011 study led by Carbone showing that tumor growth can inactivate the Notch pathway and turn off T cells. This immune suppression protects tumor cells from destruction by cytotoxic T cells.
The researchers found that Notch is inactivated by high levels of circulating vascular endothelial growth factor (VEGF). The high levels of VEGF inhibit the expression of two Notch ligands called DLL1 and DLL4 by endothelial and other cells into the bloodstream. Low levels of those ligands shut down the Notch pathway in “use it or lose it” fashion.
They also showed that boosting Notch signaling with a drug they developed in an animal model reversed the tumor-associated T-cell changes and dramatically slowed tumor growth. “We believe that if we can develop a drug that works in humans to increase Notch signaling, it will have a similar effect in patients,” Carbone says.
Carbone and Dikov are working to develop this new drug for clinical use. “To be active, it will need to consist of a multivalent form of DLL1,” Carbone says. “The idea is to express multimers of the DDL1 binding domain for optimal signaling.”
The researchers are developing the complex agent in collaboration with Ohio State biochemist Thomas Magliery, PhD, associate professor of Chemistry and Biochemistry, and a member of Ohio State’s Drug Development Institute.
“This exciting partnership is taking our findings in an animal model and using them to develop an agent we hope to use in the clinic,” Carbone says.
Studies under way by Carbone and Dikov will provide a deeper understanding of Notch, DLL1 and other Notch ligands in antitumor immunity and will help evaluate their therapeutic and prognostic potential. The work is supported by an NCI grant, “Notch Ligands in Regulation of Anti-Cancer Immunity” (CA175370). The findings will contribute to the development of the therapeutic DLL1 agent and possible prognostic assays.
Enhancing Antibody Therapies
The clinical and translational research of William Carson III, MD, focuses on strategies for inhibiting immune suppressor cells, which act to restrain the immune system. He and his lab are investigating how myeloid-derived suppressor cells, or MDSCs, affect antibody therapy (NCI grant CA095426). “We want to inhibit the cells that are braking the immune system,” Carson says. “It’s like cutting the brake line—things should go a lot faster and the cancers should shrink more.
“In many cancers, we can get a general idea of how well patients will do based on whether immune cells are infiltrating the tumor,” he adds. “That suggests that the immune system is working to eliminate these cancers, and that it’s involved in the response to treatments like radiation and chemotherapy. This idea is also supported by the effectiveness of anti-CTLA4 and anti-PD1 immune boosters.”
Carson has long had an interest in investigating the use of immune hormones to enhance the effectiveness of monoclonalantibody-based drugs.
He is principal investigator on a phase I/II trial (NCT01468896) that combines the antibody-based drug cetuximab with an immune hormone called interleukin-12 (IL-12) in patients with head andneck cancer. The drug binds to EGFR receptors on the surface of malignant tumor cells. Patients are then given an injection of IL-12. “Our thought is that immune cells like natural killer (NK) cells will attack the antibody-coated cancer cells, and that interleukin-12 will provide an extra boost to the NK cells and help them kill tumor cells more effectively,” Carson says. “It works in the test tube, it works in mice, and now we will learn if it works in humans.” (For more about this clinical trial, see page 29.)
A previous phase I trial conducted by Carson evaluated the combination of IL-12 and trastuzumab (Herceptin) in patients with breast and gastrointestinal cancers. The study accrued 21 patients with metastatic HER2-positive tumors. The findings, published in the journal Molecular Cancer Therapy, showed that IL-12 in combination with trastuzumab and paclitaxel is safe and has activity in patients with HER2-overexpressing cancers.
Anticancer Peptide Vaccines
OSUCCC – James researcher Pravin Kaumaya, PhD, professor and director of the Division of Vaccine Development in Ohio State’s Department of Obstetrics and Gynecology, is leading the development of five anticancer peptide vaccines and related peptide inhibitors.
The vaccines and inhibitors target EGFR, HER-2, HER-3, VEGF and IGF-1R receptors. The molecules play key roles in cancer-cell growth, proliferation and survival, and they are often overexpressed in breast cancer, including triple-negative breast cancer, and in pancreatic, esophageal and colon cancers. HER-2 overexpression, for example, occurs in 15-25 percent of breast cancers and is associated with aggressive tumor behavior. Kaumaya’s peptide vaccines are designed to provoke an antibody response to the target molecules on tumor cells and to generate memory that will enable the immune system to respond quickly should the cancer recur.
The peptide inhibitors target the same set of cell-surface receptors. They bind with and inactivate the target molecule, leading to programmed cell death, or apoptosis.
The agents have completed preclinical testing; the HER-2 vaccine is in phase I testing (NCT01376505) in patients with metastatic solid tumors.
“Innovative immune-based therapies that target these receptors are particularly important,” Kaumaya says, “because they might offer long-term control in several tumor types without the toxicities associated with current FDA-approved regimens.
“HER-2-positive patients are treated with humanized monoclonal antibodies such as trastuzumab,” he adds, “but they often develop resistance within a year, rendering the drug ineffective. Prolonged treatment can also lead to serious side effects, and the drugs are very expensive.”
A standard one-year course of treatment with trastuzumab, for example, can cost $70,000, he notes.
“We believe our new peptide immune-based therapies and strategies will overcome these problems,” he says, noting that the many advantages of peptides over monoclonal antibodies include lower cost, high specificity and potency, ability to penetrate the cell membrane, low immunogenicity and greater overall safety.
Furthermore, preclinical studies conducted by Kaumaya and his collaborators suggest that combining two peptide vaccines, two inhibitors, one of each or combined with chemotherapy might further improve the agents’ effectiveness.
“We believe that strategies that selectively target both IGF-1R and HER-3 hold great promise for overcoming mechanisms of resistance to HER-1- and HER-2-targeted agents and facilitating tumor regression in a range of tumor types,” Kaumaya says.
“More broadly, we believe our novel immune-stimulatory strategies using peptide vaccines and inhibitors hold the promise of durable clinical benefit for high-risk, recurrent, refractory and metastatic cancers,” he adds.
Immune therapy is a long-term focus of the OSUCCC – James Leukemia Research Program. “Our goal is to develop immune therapies for hematologic malignancies as one component of a move away from chemotherapy altogether,” says Jeffrey Jones, MD, MPH, section head for CLL/Hairy Cell Leukemia.
It’s an attainable target made possible, he says, by recent advances in technology that enable new treatment strategies. He notes three approaches to immune therapy for hematologic malignancies:
• Monoclonal-antibodies and other agents that stimulate both the adaptive and innate immune response;
• Monoclonal antibodies tagged with a toxin or a radioactive isotope that kills targeted cells;
• Engineered T cells, or chimeric antigen receptor (CAR) T cells.
Early examples of the first strategy included native immune stimulants like IL-2 and INF-alpha. But the most notable successes have been the drug rituximab, a monoclonal antibody that targets CD20 on B cells first approved for clinical use in 1997, and next generation “engineered” CD20-targeted antibodies like obinutuzumab. Binding of the antibody on cancer cells attracts natural killer (NK) cells and other innate immune system elements that kill the cells through antibody-dependent cell-mediated cytotoxicity (ADCC) and the complement system.
Ongoing studies at the OSUCCC – James are now exploring antibodies directed at new targets, such as B-cell markers CD19 and CD37, as well as checkpoint inhibitors like nivolumab and pembrolizumab recently approved for solid tumor indications but with preliminary data suggesting efficacy in blood cancers, too.
According to Jones, “Combinations of antibodies targeting different markers on the cancer cell surface may better rally the patient’s own immune system to engage their cancer.” Also promising is the potential for combining monoclonal antibody therapy with targeted agents, like the recently approved kinase inhibitors ibrutinib and idelalisib. Jones says the OSUCCC – James Leukemia Research Program will lead several such studies for CLL expected to open later in 2015.
The second approach uses immunoconjugates, antibodies linked to a toxic agent. Two clinical trials under way at the OSUCCC – James are good examples. Kami Maddox, MD, an OSUCCC – James B-cell malignancy specialist, leads a phase I trial (NCT01534715) evaluating the immunoconjugate IMGN529 in patients with relapsed or refractory non-Hodgkin’s lymphoma. The toxin, once released into target cells, blocks mitosis and the cells die by apoptosis.
Jones is the local principal investigator on the second trial. The phase III study (NCT01829711) for patients with relapsed or refractory hairy cell leukemia evaluates an anti-CD22 antibody linked to a pseudomonas toxin. CD22 is a molecule present on essentially all hairy cell leukemia cells, Jones says. The trial evaluates the effectiveness of moxetumomab pasudotox in killing hairy cell leukemia cells and in producing lasting complete remissions.
CAR T Cells
CAR T cells are T cells that are genetically altered to generate a disease-specific immune response. “Success with this novel technology is one of the most exciting developments in hematologic malignancies during the last 10 years,” Jones says. “It tricks the patient’s own T cells to zero in on a new target.”
It is a form of adaptive immune therapy, he notes. This strategy begins by isolating T cells from a patient’s blood, manipulating them genetically to target the patient’s cancer subtype, then infusing the cells back into the patient, where they expand and wage an immune response against leukemia cells.
“Ohio State is one of the designated sites for a multicenter trial that will use CAR T cells to treat acute lymphoblastic leukemia,” Jones says.
“The next step is to combine these new immune therapies with targeted inhibitors,” he adds. “That’s the direction the field is going. Cancer immunotherapy is a very fertile area of investigation.”
Immune therapy today includes not only the cytokines that were used in the 1980s and ‘90s, but also the monoclonal antibodies developed in the 2000s, Carson says. “We also have the newer immune boosters such as anti-PD1 and anti-CTLA4, along with promising cancer vaccines and CAR T cells from the 2010s. We have trickier ways to stimulate the immune system than giving high levels of immune hormones.”
And there’s more to come, Carson says. “We have new technologies, new ideas, new targets and a renewed realization that the immune system is a powerful tool we must incorporate as new treatment options for cancer patients. Cancer immune therapy is an exciting field full of possibilities.”
To refer a patient, please call The James Line New-Patient Referral Center toll-free: 1-800- 293-5066.
CAR T Cells Show Precinical Promises as Multiple Myeloma Therapy
A recent study by OSUCCC – James researchers provided evidence that genetically modified immune cells might effectively treat multiple myeloma, a disease that remains incurable and accounted for an estimated 24,000 new cases and 11,100 deaths in 2014.
The researchers modified T lymphocytes, or T cells, to target a molecule called CS1, which is found on more than 95 percent of myeloma cells. The modified cells—technically called chimeric antigen receptor (CAR) T cells—were able to identify myeloma cells and kill them.
The researchers grew the modified T cells in the lab to increase their numbers and then injected them into an animal model where they again killed human myeloma cells.
The findings were published in the journal Clinical Cancer Research.
“Despite current drugs and use of bone marrow transplantation, multiple myeloma remains incurable, and almost all patients eventually relapse,” says co-principal investigator and multiple myeloma specialist Craig Hofmeister, MD, MPH, assistant professor of medicine and a member of the OSUCCC – James Leukemia Research Program.
“This study presents a novel strategy for treating multiple myeloma, and we hope to bring it to patients as part of a phase I clinical trial as soon as possible,” Hofmeister says.
“In particular, our study shows that we can modify T lymphocytes to target CS1, and that these cells efficiently destroy human multiple myeloma cells,” says principal investigator Jianhua Yu, PhD, assistant professor of medicine and a member of the OSUCCC – James Molecular Carcinogenesis and Chemoprevention Program.
“An important possible advantage to this approach is that these therapeutic T cells have the potential to replicate in the body. Therefore, they might suppress tumor growth and prevent relapse for a prolonged period,” Yu says.
Yu, Hofmeister and their colleagues used cell lines and fresh myeloma cells from patients to produce genetically engineered T cells with a receptor that targets CS1. The researchers then tested the capacity of the modified cells to kill human multiple myeloma cells in laboratory studies and an animal model.
Funding from the National Institutes of Health (CA155521, OD018403), Multiple Myeloma Opportunities for Research and Education, the National Blood Foundation, and an OSUCCC – James Pelotonia Idea Grant supported this research.