UTSW study identifies potential therapeutic target for incurable, rare type of soft-tissue cancer

A deadly, rare type of soft-tissue cancer may be completely eradicated simply by inhibiting a key protein involved in its growth, UT Southwestern Medical Center researchers report.

In the study, published online today in Cell Reports, scientists found that inhibiting the action of a protein called BRD4 caused cancer cells to die in a mouse model of malignant peripheral nerve sheath tumors (MPNSTs).

"This study identifies a potential new therapeutic target to combat MPNST, an incurable type of cancer that is typically fatal," said Dr. Lu Le, Assistant Professor of Dermatology at UT Southwestern and senior author of the study. "The findings also provide important insight into what causes these tumors to develop."

MPNSTs are highly aggressive sarcomas that form around nerves. These tumors can develop sporadically, but about half of cases are in patients with a genetic disorder called neurofibromatosis type 1 (NF1) that affects 1 in 3,500 people. About 10 percent of NF1 patients will develop MPNST, which usually evolves from a benign but often large and disfiguring tumor called a plexiform neurofibroma.

Up to now, the preferred treatment for MPNST has been surgical removal, but that oftentimes is difficult or impossible due to the tumor's location around nerves. Radiation and chemotherapy are other options, but their effectiveness is limited. The five-year survival rate for MPNST patients is about 50 percent.

By studying changes in cells as they evolved into cancerous MPNSTs, researchers in Dr. Le's laboratory were able to determine that BRD4, a bromodomain protein that binds to DNA to regulate gene activation, is expressed at an unusually high level in MPNST cancer cells. This action caused another protein called BCL-2 to keep cancer cells from dying. Alternately, when researchers inhibited BRD4 either genetically in the mice or pharmacologically by administering a compound called JQ1, the tumors shrank.

What is a soft tissue sarcoma?

A sarcoma is a type of cancer that develops from certain tissues, like bone or muscle. There are 2 main types of sarcoma: bone sarcomas and soft tissue sarcomas. Soft tissue sarcomas can develop from soft tissues like fat, muscle, nerves, fibrous tissues, blood vessels, or deep skin tissues. They can be found in any part of the body. Most of them develop in the arms or legs. They can also be found in the trunk, head and neck area, internal organs, and the area in back of the abdominal cavity (known as the retroperitoneum). Sarcomas are not common tumors, and most cancers are the type of tumors called carcinomas.

There are many types of soft tissue tumors, and not all of them are cancerous. When a tumor is not cancerous, it is called benign. When the term sarcoma is part of the name of a disease, it means the tumor is malignant (cancer). There are about 50 different types of soft tissue sarcomas.