B2M and breast carcinoma: To further validate the results from the two types of breast cancer cell lines, the expression of β2M and signaling molecules such as HER2, HIF-1α, p-CREB, VEGF, p-ERK, p-SGK1, and Bcl-2 in the two types of HER2− breast cancer tissues were examined by real-time PCR and IHC.