UCLA School of Dentistry Researchers Discover Natural Tumor-Suppressive Function of RNA-Building Protein

Posted on: Monday, 05/15/2006

UCLA School of Dentistry researchers studying a basic human protein essential in processing and metabolizing RNA have discovered it works as a natural tumor suppressor effective against head and neck cancer.

These findings are reported in the May 15 issue of Clinical Cancer Research, one of the leading peer‑reviewed journals of the American Association for Cancer Research.

The protein, heterogeneous nuclear ribonucleoprotein G (hnRNP G), was until now perhaps the least investigated of a class of 30 ribonucleic acid-binding proteins with diverse biological functions.

While the researchers readily detect hnRNP G in healthy skin tissue, they report they do not find the protein in the vast majority of precancerous and cancerous tissues. Moreover, the UCLA scientists present evidence that hnRNP G injected into human oral squamous cell carcinoma (HOSCC) cells is effective in inhibiting the proliferation and tumor-forming capacity of HOSCC in test tubes and in an animal model.

While the scientists acknowledge that hnRNP G's particular mechanisms of action require further investigation, these findings suggest the protein's value in the development of new ways to diagnose and treat HOSCC.

According to the National Cancer Institute, most head and neck cancers can be attributed to this type of cancer, which begins in the squamous cells that line the mucosal surfaces in the head and neck. It is estimated that nearly 40,000 people will develop a form of head and neck cancer this year.

"If we know that hnRNP G is present in healthy cells, but absent in precancerous and cancerous cells, then we should be able to design a test to diagnose HOSCC by measuring the level of this protein present in a tissue sample," said Dr. No-Hee Park, professor of diagnostic and surgical sciences, dean of the UCLA School of Dentistry, and a member of UCLA's Jonsson Cancer Center. "Our examination of the unique biological properties and functions of hnRNP G represents one small step toward a better understanding of carcinogenesis as well as improved methods of early diagnosis and treatment."

The technology transfer office at UCLA is actively filing for intellectual property protection of the discovery of hnRNP G's tumor-suppressive ability and is in the process of speaking with potential commercial partners concerning possible clinical applications.

"HOSCC is associated with both high morbidity and high mortality with a survival rate of only 50 percent," said Dr. Earl Weinstein, who handles life sciences business development and licensing for UCLA's Office of Intellectual Property Administration. "We are therefore excited by the potential to develop these findings into a new diagnostic marker and, longer term, into a new therapeutic approach to this unmet medical need."

In the meantime, Park and his colleagues plan to continue studying hnRNP G. In particular, they are interested in determining whether the protein's ability to inhibit the growth of tumors is as effective against other types of cancers as it is against HOSCC. The hope is that their initial discovery will have wide implications for future cancer research.

"The findings reported by No-Hee Park's lab may lead scientists at UCLA and elsewhere to look for ways to use this protein to diagnose and treat not only HOSCC, but also other cancers such as breast and prostate cancer," said Dr. Judith C. Gasson, director of UCLA's Jonsson Cancer Center and a professor of medicine and biological chemistry.

In addition to Park, the paper's authors include Ki-Hyuk Shin, Mo K. Kang, Reuben H. Kim and Russell Christensen.

The hnRNP G research project was supported in part by grants funded by the National Institute of Dental and Craniofacial Research.

The UCLA School of Dentistry is dedicated to improving the oral health of the people ofCalifornia, the nation and the world, and has established an international reputation for its teaching, research, patient care and public service initiatives. The school provides education and training programs that develop leaders in dental education, research, the profession and the community; conducts research programs that generate new knowledge, promote oral health and investigate the cause, prevention, diagnosis and treatment of oral disease; and delivers patient‑centered oral health care to the community and state.