Amplification of LAPTM4B and YWHAZ contributes to chemotherapy resistance and recurrence of breast cancer

Post-surgery adjuvant chemotherapy for breast cancer has effectively reduced metastatic recurrence rates1. However, a significant proportion of women suffer recurrent cancer at distant metastatic sites despite adjuvant treatment. Identification of the genes critical for tumor response to specific chemotherapy drugs is a challenge, but necessary to improve outcomes2. Using integrated genomics, we identified a small number of over-expressed and amplified genes from chromosome 8q22 significantly associated with early disease recurrence despite anthracycline-based adjuvant chemotherapy. The association was confirmed in an analysis of multiple independent cohorts. Two of these genes, the anti-apoptotic gene YWHAZ, and LAPTM4B, a novel lysosomal gene, sensitized tumor cells to anthracyclines when either was depleted by siRNA knockdown and induced drug resistance when either was over-expressed. Over-expression of LAPTM4B resulted in sequestration of drug, delaying its appearance in the nucleus. Over-expression of these two genes was associated with poor tumor response to anthracycline treatment in a neo-adjuvant chemotherapy trial in women with primary breast cancer. Our results suggest that 8q22 amplification and over-expression of LAPTM4B and YWHAZ contribute to de novo chemoresistance to anthracyclines, and are permissive for metastatic recurrence. These two genes may predict anthracycline resistance and influence selection of chemotherapy.