Synovial Sarcoma Treatment Strategies

OREF grant recipient investigates molecular targets
Synovial sarcoma is a rare soft-tissue cancer that most often affects children and young adults. Synovial sarcoma is aggressive and difficult to treat, and it presents a significant risk of metastasis, particularly to the lungs. Treatment generally employs multimodal therapies that include surgery, chemotherapy, and radiation.

One strategy for improving outcomes is to develop a drug that could disable a key molecule—one link in a chain of molecular events—that enables the survival and proliferation of synovial sarcoma cells.

"We have a much better understanding today of the molecular biology of how cancer works," stated Patrick Andrew Holt, MD, PhD, orthopaedic surgery resident at the University of Utah in Salt Lake City.

"What we want to do now is develop highly specific, targeted therapies that disrupt these molecular processes," he added.


With funding from OREF, Dr. Holt used computer modeling to screen for potential selective inhibitors of Bcl-2.

Dr. Holt's research in this field was funded in part by a 2013 Orthopaedic Research and Education Foundation (OREF) Young Investigator Grant (now called the OREF New Investigator Grant). This 1-year grant provides up to $50,000 to advance the scientific training of clinician scientists who are currently completing orthopaedic surgical training, are enrolled in advanced surgical training, or have completed training within the last four years. Funding for Dr. Holt's grant was made possible by Zimmer Holdings, Inc.

The biology of anti-apoptosis
The molecular target of Dr. Holt's research is B-Cell Lymphoma-2 (Bcl-2), one of several related molecules that regulate programmed cell death (apoptosis). Some members of this family carry out pro-apoptotic functions, while others are anti-apoptotic.

When a normal cell undergoes a stress signal, one of the pro-apoptotic molecules, called BH-3, sends a "death message" that sets in motion the signaling pathway leading to cell death. Bcl-2, one of the anti-apoptotic molecules, can intercept this message by binding to BH-3.

Synovial sarcoma tumor cells—along with some other cancer cells— overexpress Bcl-2. The abundance of Bcl-2 shuts down programmed cell death and thereby facilitates the cellular proliferation.

Several research studies have shown the promise of Bcl-2–inhibiting drugs, but many of these drugs have side effects, including possible blood platelet deficiencies. These side effects may be due to the drugs nonspecifically binding on other, unintended molecules. Dr. Holt's goal is to identify potential specific Bcl-2 inhibitors that do not have an affinity for other molecules in the family of apoptotic regulators.

Virtually screening for new treatment candidates
Dr. Holt's OREF-funded research was three-fold: using computer modeling to screen for potential inhibitors, characterizing the binding properties of promising candidate inhibitors, and testing these molecules in vitrowith established lines of synovial sarcoma cells.

The first phase was a large-scale virtual screening of commercially available chemical compounds for their structural and chemical affinity to Bcl-2. This work was done in collaboration with the University of Louisville in Kentucky and under the direction of John O. Trent, PhD, with whom Dr. Holt completed his MD and PhD studies.

He explained, "The University of Louisville has one of the largest dedicated computer grids for virtual screening in the country, with more than 14,000 computers. During the day these computers are used by children in Kentucky schools for educational pursuits, and at night we can harness their computational power to screen millions of chemical compounds."

With this virtual screening system, the researchers input a high-resolution model of the Bcl-2 binding site. The screening software enabled them to search for compounds that would selectively bind to unique structural features of that site. Similarly, the system screened for compounds that are chemically similar to the currently available Bcl-2–inhibiting drug, but with novel properties that may alter selectivity. Additionally, the databases were configured to filter compounds for their drug-like properties that would be more likely to translate into viable treatment options.

After identifying the 200 most promising candidates in the virtual computer screen, the researchers purchased these commercially available molecules for further analysis. They then conducted a series of biophysical tests to characterize the binding properties of each of the candidate molecules.

Based on that analysis, the researchers identified compounds with properties most selective for binding to Bcl-2. This work has been carried out under the direction of R. Lor Randall, MD, FACS, director of Sarcoma Services at the Huntsman Cancer Center in Salt Lake City. They tested each candidate in vitrofor itspotency in suppressing tumor growth with established synovial sarcoma cell lines at the University of Utah. At the time of this writing, the researchers have discovered several novel compounds that significantly inhibit synovial sarcoma cell proliferation in vitro.

The ultimate goal is to test these promising new compounds in preclinical and clinical trials to assess the viability of a highly selective Bcl-2 inhibitor to shrink tumors prior to surgery, increase the vulnerability of tumors to chemotherapy, or suppress metastatic disease.

Funding research, advancing careers
Dr. Holt stated that one of the greatest challenges for residents—or other clinicians in training who want to pursue a career in research—is balancing the demands of a real hypothesis-driven investigation with clinical training. He stated, "One of the beauties of the OREF grant portfolio is that the organization takes into account where you are in your career and supports your research efforts."

He observed that OREF not only nurtures new ideas in research but also a clinician's progress in academic medicine. He added, "While I am grateful for the OREF grant funding our research project, I did not anticipate how profound an influence it would have on career decisions. I think there is a very small window in a career when you can be influenced to pursue a surgeon-scientist track. OREF plays an invaluable role in fostering our growth at this critical juncture."

Jay D. Lenn is a contributing writer for OREF. He can be reached at communications@oref.org