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Researchers Find New Gene Associated with Breast Cancer (dateline August 31, 2003)

Researchers have identified a possible new gene involved with breast cancer, according to a study that was scheduled to be presented at the annual meeting of the American Association for Cancer Research. The gene, called C35, was found in overabundance in more than 60% of breast cancer cases in the study. The gene is closely linked with a previously identified breast cancer gene, HER2 (also spelled HER2/neu). The researchers believe the finding could spark investigations into novel types of treatment which target the C35 gene.

HER2 (human epidermal growth factor receptor 2) is a gene found on the surface of cells that, when functioning normally, has been found to be a key component in regulating cell growth. However, when the HER2 gene is altered, extra HER2 receptors may be produced. This over-expression of HER2 causes increased cell growth and reproduction, often resulting in more aggressive breast cancer cells. Recently, researchers have found that the HER2 gene is over-expressed in approximately 30% of breast cancer cases.

Similar to the HER2 gene, researchers have found that another gene, C35, appears to be over-expressed in many breast cancer cases. The C35 gene is located on chromosome 17 and is adjacent to the protein that encodes HER2, according to researcher Deepak M. Sahasrabudhe, M.D., Director of the Hematology-Oncology Fellowship Program and Professor of Medicine and Oncology at the University of Rochester School of Medicine and Dentistry, New York.

In their study, Dr. Sahasrabudhe and colleagues found that the protein that encodes C35 was overabundant in 65% of breast cancer cases, compared with the HER2, which is over-expressed in approximately 30% of cases. HER2 has been found to be associated with high grade tumors, which tend to be more aggressive (i.e., grade II and grade III breast cancer tumors). In the study, 34% of breast cancer patients were found to have an overabundance of both C35 and HER2, while 31% tested positive for C35 and negative for HER2. Interestingly, all of the breast cancer patients who over-expressed HER2 also over-expressed C35.

"While large scale clinical studies have not yet been completed to confirm the prevalence of C35 in breast cancer patients, we are excited about these results and hope that C35 may eventually become a target of therapy and predictor of prognosis in breast cancer," said Dr. Sahasrabudhe, in an American Association for Cancer Research news release.

Researchers have already developed an exciting new treatment that targets the over-expression of the HER2 gene. The drug Herceptin works by attaching itself to the HER2 protein receptors on the surface of breast cancer cells. By binding to the cells, Herceptin slows the growth and spread of tumors. Many experts believe that Herceptin represents the future direction of breast cancer drugs in that it targets a particular protein of the cancer cell and prevents it from carrying out its action, similar to the leukemia drug, Gleevec.

It is hoped, if future studies confirm that many breast cancer cases are indeed associated with the over-expression of the C35 gene, that a similar therapy could be developed to target this gene. "We believe that future treatment of C35 positive breast cancer will be a two-pronged approach," said Dr. Sahasrabudhe, in an American Association for Cancer Research news release. "It may entail an agent targeting C35, together with standard radio- or chemotherapy to induce further tumor cell death. A vaccine therapy to prevent the growth of C35-expressing tumor cells might also be a treatment approach."

Additional Resources and References

  • The study discussed in this article is published in the 2003 edition of Proceedings by the American Association for Cancer Research.
  • The April 8, 2003 American Association for Cancer Research news release, "Researchers Identify New Gene Associated with Breast Cancer: C35 Gene May Be Effective Immunotherapy Target," is available at
  • To learn more about the HER2 gene and Herceptin, please visit