Expression of the Insulin Receptor Substrate 1 in primary tumors and lymph node metastases in breast cancer: correlations with Bcl-xL and Bax proteins.

In our previous investigation Insulin Receptor Substrate 1 (IRS-1) correlated with proliferation marker Ki-67 in human breast cancer. The aim of the present study was to assess relationships between IRS-1 expression and anti-apoptotic Bcl-xL as well as proapoptotic Bax proteins, assessed by immunohistochemistry, in primary tumors and lymph node metastases of breast cancer. IRS-1 is positively associated with both Bcl-xL and Bax in primary and metastatic tumors. Thus, our results could suggest that IRS-1 might affect turnover of cancer cells and breast cancer progression through activation of mitogenesis and participation in the regulation of the balance between anti- and proapoptotic pathways.