Discovery of Small Molecule Lethal to Myeloma Cells
Novel Technique Paves the Way for More Effective Cancer Therapies
Multiple myeloma remains the second most common hematologic malignancy. Although treatment options have improved in the last decade, cure is exceedingly rare. The most effective treatments cause a variety of sometimes debilitating—even life-threatening—side effects and, ultimately, stop working.
For these reasons, the potential of epigenetic research conducted by Cleveland Clinic hematologist/oncologist Frederic J. Reu, MD, is all the more exciting. Dr. Reu and his laboratory partner, Sergei Vatolin, PhD, have developed a high-throughput screening method that identifies molecules that reactivate or silence specific genes. The technique has allowed them to turn off interferon regulatory factor 4 (IRF4), a protein required for myeloma cell survival. The results are no less than spectacular.
Manipulating DNA to fight cancer
Intrigued by how cancer cells exploit the innate ability of stem cells to activate or shut down genes expressed at various times in their development, Dr. Reu sought a technique that would identify molecules that modify specific, critical genes to activate tumor suppressor genes or shut down oncogenes.
“Available epigenetic drugs can only activate tumor suppressor genes, and they are difficult to use due to metabolic differences among patients and off-target side effects. I wanted to find a system that would allow the identification of oncogene silencers and lead to drugs with fewer side effects,” he explains.
The key lay in developing a method to analyze chromatin conformation in whole cells. Chromatin is a structure containing primarily DNA and proteins. Drs. Reu and Vatolin exploited the fact that silenced gene regions and specific regions of very active genes require higher temperatures and/or salt concentrations for proteins to dissociate from DNA. Once DNA is liberated, it can be amplified and visualized using polymerase chain reaction (PCR) and DNA-specific dyes. The researchers developed a method of accomplishing this in a single pipetting step, which allowed thousands of different small molecules to be tested in a 3-hour period. By targeting an IRF4 site in myeloma cells, they were able to identify small molecules that interfered with expression of this myeloma survival factor.
“We confirmed which molecules completely shut off IRF4 within hours. They killed the myeloma cells, without significantly affecting other cells. This is very exciting, because no myeloma drug inhibits IRF4 at a comparable rate, and small molecules are easily made into oral therapies,” says Dr. Reu. “Furthermore, the technique can be used for any gene found to be important for myeloma or any other cancer.
A complete explanation of the project can be found in the September 12, 2012 online issue of PLOS ONE.
The next phase of this project involves testing the compounds in mice to determine their ability to kill myeloma cells in an organism through IRF4 inhibition, to ascertain how well they are tolerated, and to measure how well they are absorbed. The researchers will work with human myeloma cell lines containing a firefly gene that expresses light for in vivo efficacy measurements, cells from refractory multiple myeloma patients grown in immunodeficient mice, and mouse myeloma cells grown in immunocompetent mice. The ultimate goal of course is to develop these drugs into improved therapies for myeloma patients.
Cleveland Clinic Conducts The First Phase 2 Clinical Trial Of TRC105
TRC105 is a new antiangiogenic drug that targets CD 105 or endoglin, in glioblastoma (GBM), the most common type of malignant adult brain tumor.
Cleveland Clinic is conducting the first Phase 2 clinical trial of TRC105, a new antiangiogenic drug that targets CD 105 or endoglin, in glioblastoma (GBM), the most common type of malignant adult brain tumor. Patients with GBM have a poor prognosis and usually survive approximately 15 months following diagnosis.
The current standard of care for GBM is maximum possible resection followed by chemotherapy and radiation. The most effective chemotherapy for GBM is temozolomide, which attacks the DNA of tumor cells. Patients who don’t respond to treatment or have a recurrence are treated with bevacizumab (Avastin), an antibody that inhibits vascular endothelial growth factor (VEGF). Avastin leads to improvement in progression-free survival and offers some clinical benefit, including reduced swelling that arises from the tumor. “Overall, patients with recurrent GBM respond to Avastin for six to nine months. However, when Avastin stops working, there are no good established treatment options and those patients generally survive less than six months” says Manmeet Ahluwalia, MD, Section Head of NeuroOncology Outcomes in the Rose Ella Burkhardt Brain Tumor and Neuro-Oncology Center of the Neurological Institute of Cleveland and a neuro-oncologist at the Taussig Cancer Institute, Cleveland Clinic.
The Clinic trial is studyingTRC105 in Avastin refractory patients. After treatment with a VEGF inhibitor, some tumors in laboratory experiments have shown an upregulation of CD105, (endoglin), an endothelial cell receptor that is essential for angiogenesis, as the cancer cell looks for other ways to form new blood vessels. Developed by Tracon Pharmaceuticals, TRC105 is an IgG1 monoclonal antibody to CD105 and is one of a new generation of antiangiogenic drugs that are targeting factors other than VEGF that are involved in blood vessel formation.
In a Phase 1 study of advanced solid tumors, TRC105 therapy caused a global reduction in angiogenic biomarkers and reduced tumor burden at doses that were well-tolerated. If this trial shows that TRC105 is safe and effective for use with glioblastoma, it has the potential to complement VEGF inhibitors. “We are hoping TRC105 is effective as we desperately need better treatment options for glioblastoma patients,” says Dr. Ahluwalia.
There are other trials that will be studying TRC105 in Avastin naïve GBM patients: one trial will evaluate the effectiveness of the combination of TRC105 and Avastin, and a National Cancer Institute trial will look at TRC105 as a single agent.
Taussig Cancer Institute Clinical Trials
Taussig Cancer Institute provides world-class care to patients with cancer and is at the forefront of new and emerging clinical, translational and basic cancer research. Taussig annually enrolls over 1300 patients in over 240 clinical trials.
Please read more about our featured trials this month: