A new study presented at the 2011 Era of Hope breast cancer conference has reported that type 2 diabetes and obesity significantly reduce cancer-specific survival in a mouse model of HER2 overexpressing breast cancer. Type 2 diabetes is a significant risk factor for cancer development and death from cancer, according to population studies. The authors previously demonstrated that an increase in insulin and glucose concentrations (similar to the high circulating insulin and glucose levels of people with type 2 diabetes) can stimulate the growth of cancer cells in the laboratory. In the current experiments, the authors successfully developed an animal model of HER2+ breast cancer and type 2 diabetes. Diabetic leptin receptor db/db mice (which become obese) were bred with MMTV-ErbB2 (neu) transgenic mice (which spontaneously develop HER2+ mammary tumors) to generate "obese-HER2+" mice that are morbidly obese and consistently develop HER2+ mammary tumors.

The cancer-specific survival of the obese-HER2+ mice was compared with that of their lean littermates (with leptin receptor db/+ or +/+) and was found to be significantly worse, according to preliminary results presented at the conference. Pathological review of tumors harvested after the animals were sacrificed demonstrated that the obese-HER2+ mice produced the same types of HER2+ tumors as the nondiabetic littermates. Carcinoma cells were seen within mammary tissue, as were solid nodules of adenocarcinomas, cystic papillary carcinomas, and intraductal carcinoma in situ. Thus, the authors have for the first time successfully developed a mouse model of type 2 diabetes and HER2-overexpressing breast cancer. The authors comment that, in addition to using this model to evaluate the impact of type 2 diabetes on cancer and the impact of antidiabetic medications on cancer-specific survival, this model can also be used to examine of the impact of type 2 diabetes on HER2+ breast cancer and the interaction of metformin and other oral anti-diabetic drugs with HER2 receptor signaling.

Please see our articles on type 2 diabetes and breast cancer and HER2 prognosis for more information.