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Doctor discusses cancer-related gene

Nov. 19, 1998

BY JULIA MCKENZIE

Reporter

Julia_McKenzie@baylor.edu

Now that researchers have isolated early onset breast cancer genes, some hope hereditary breast cancer may be caused by a mutation in one single gene, a Dallas doctor said in a speech Wednesday.

'Will there be one gene that can cause cancer? Well, I don't think it's that simple,' said Dr. Anne Bowcock, from UT Southwestern Medical Center in Dallas.

Sponsored by Alpha Chi Honor Society and the Baylor Biology Department, Bowcock spoke on 'The Molecular Basis of Hereditary Breast Cancer' in Sid Richardson Science Building.

Bowcock, associate professor in the Department of Internal Medicine and Pediatrics at the Eugene McDermott Center for Human Growth and Development at UT Southwestern Medical Center, is a member of several noted scientific and medical committees and has highlighted her genetic research in more than 100 articles.

It is important to remember that only five percent of all breast cancer is heritable, with the remaining 95 percent sporadic, Bowcock said.

However, researchers do know that most of the heritable cancers correspond to alterations in BRCA1 and BRCA2, early onset breast cancer genes.

According to statistics Bowcock presented from the American Journal of Human Genetics, a 40-year-old woman with a mutation in BRCA1 has an 18 percent chance of having breast cancer, while a woman of the same age without the mutation has a two percent chance.

The risk rises to 86 percent for an 80-year-old woman with the mutation, but it is only 12 percent if BRCA1 is normal.

Mutations in BRCA1 are also linked to cases of familial ovarian cancer, Bowcock said. In fact, nearly 10 percent of patients with heritable ovarian cancer show mutations in the gene, but BRCA1 is normal in all patients with sporadic ovarian cancer.

Bowcock said the normal BRCA1 gene probably assists in DNA repair, and is essential for a special type called transcription-coupled repair. Therefore, in the case of a damaged BRCA1 gene, mistakes made during DNA replication could go undetected, leading to higher mutation rates and eventually cellular malfunction.

Bowcock's presentation was one of the two seminars that Alpha Chi Honor Society sponsors a year. Dr. Wendy E. Sera, assistant biology professor, said.

Hilscher said she became familiar with Bowcock's work this summer.

'I worked for her this during an internship I did at the UT Southwestern Medical Center,' she said.

Bowcock earned her Bachelor's degree in genetics and her Ph.D. in human genetics in Johannesburg, South Africa, and then completed a post-doctoral fellowship at Stanford University, according to Hilscher.

Most breast cancer experts have concluded that BRCA1 codes for a nuclear protein and may also be a type of 'transcriptional activator,' which makes possible the production of other proteins.

Also, Bowcock said the normal BRCA1 gene probably assists in

DNA repair, and is essential for a special type called transcription-coupled repair. Therefore, in the case of a damaged BRCA1 gene, mistakes made during DNA replication could go undetected, leading to higher mutation rates and eventually cellular malfunction.

'So, unfortunately, we're finding that altering this gene probably will not eliminate breast cancer, but it may provide an effective therapy,' Bowcock said.Researchers are aiming much of their research at understanding how the interactions of BRCA1 and BRCA2 with other intracellular factors contribute to heritable breast cancer.

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