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.
This document is about soft tissue sarcomas in adults. Sarcomas occurring in bone, such as osteosarcomas and Ewing Family of Tumors are discussed in separate documents. Rhabdomyosarcoma, the most common type of soft tissue sarcoma seen in children, is also discussed in another document.
“These treatments suppressed tumor growth and caused the cancer cells to undergo apoptosis, or cell death. This is why BRD4 inhibition is exquisitely effective against MPNSTs and may represent a paradigm shift in therapy for these patients,” Dr. Le said.
The same class of drug used in the experiments is currently being evaluated in phase 1 and 2 trials for treatment of leukemia and a subtype of lung cancer. Meanwhile, UT Southwestern is working with a pharmaceutical company to develop a similar BRD4-inhibiting drug to launch a clinical trial for MPNST patients.
New drugs are desperately needed to treat MPNST and provide hope to NF1 patients at highest risk for this cancer, said Dr. Le, who also serves as Co-director of UT Southwestern’s Comprehensive Neurofibromatosis Clinic. The clinic offers neurofibromatosis patients access to the latest clinical trials and treatments. Co-directed by Dr. Laura Klesse, Assistant Professor of Pediatrics, the clinic is part of the Harold C. Simmons Comprehensive Cancer Center and serves patients with all three types of hereditary neurofibromatosis, including the dominant NF1 type and rarer NF2 and Schwannomatosis forms.
Soft Tissue Sarcoma
Your soft tissues connect, support, or surround other tissues. Examples include your muscles, tendons, fat, and blood vessels. Soft tissue sarcoma is a cancer of these soft tissues. There are many kinds, based on the type of tissue they started in. They may cause a lump or swelling in the soft tissue. Sometimes they spread and can press on nerves and organs, causing problems such as pain or trouble breathing.
No one knows exactly what causes these cancers. They are not common, but you have a higher risk if you have been exposed to certain chemicals, have had radiation therapy, or have certain genetic diseases.
Doctors diagnose soft tissue sarcomas with a biopsy. Treatments include surgery to remove the tumor, radiation therapy, chemotherapy, or a combination.
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NIH: National Cancer Institute
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Other UT Southwestern researchers involved in the study, all in Dermatology, were first author and graduate student Amish Patel; postdoctoral researchers Drs. Chung-Ping Liao and Zhiguo Chen; and research assistants Chiachi Liu and Yong Wang. The study was funded by UT Southwestern’s Disease-Oriented Clinical Scholars Program, the Dermatology Foundation, the Children’s Tumor Foundation, the National Cancer Institute, and the U.S. Department of Defense.
About UT Southwestern Medical Center
UT Southwestern, one of the premier academic medical centers in the nation, integrates pioneering biomedical research with exceptional clinical care and education. The institution’s faculty includes many distinguished members, including five who have been awarded Nobel Prizes since 1985. Numbering more than 2,700, the faculty is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide medical care in 40 specialties to nearly 91,000 hospitalized patients and oversee more than 2 million outpatient visits a year.
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Debbie Bolles
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