IGF1R and breast cancer: AR expression in the primary breast cancers correlated with expression of p-HER2, EGFR, p-EGFR, p-IGFR, and p-ERK in patients who did not benefit from letrozole plus dasatinib (PFS ≤ 6 months), suggesting a potential interaction between AR and HER family receptors in letrozole/dasatinib resistance.