PURPOSE: To identify biomarkers within the breast cancer genome that may predict chemosensitivity in breast cancer EXPERIMENTAL DESIGN: We conducted an RNAi screen within the breast cancer genome for genes whose loss-of-function enhanced docetaxel chemosensitivity in an estrogen receptor negative, progesterone receptor negative, and Her2 negative (ER- PR- Her2-) breast cancer cell line, MDA-MB-231. Top candidates were tested for their ability to modulate chemosensitivity in 8 breast cancer cell lines and to demonstrate in vivo chemosensitivity in a mouse xenograft model. RESULTS: From ranking chemosensitivity of 328 short-hairpin RNA (shRNA) MDA-MB-231 cell lines (targeting 133 genes with known somatic mutations in breast cancer), we focused on the top two genes, kinesin family member 14 (KIF14) and talin 1 (TLN1). KIF14 and TLN1 loss-of-function significantly enhanced chemosensitivity in 4 triple-negative breast cancer cell lines (MDA-MB-231, HCC38, HCC1937, and Hs478T) but not in 3 hormone-receptor-positive cell lines (MCF7, T47D, and HCC1428) or normal human mammary epithelial cells (HMECs). Decreased expression of KIF14, but not TLN1, also enhanced docetaxel sensitivity in a Her2-amplified breast cancer cell line, SUM190PT. Higher KIF14 and TLN1 expressions are found in triple negative breast cancers compared to the other clinical subtypes. Mammary fat pad xenografts of KIF14- and TLN1- deficient MDA-MB-231 cells revealed reduced tumor mass compared to control MDA-MB-231 cells after chemotherapy. KIF14 expression is also prognostic of relapse-free and overall survival in representative breast cancer expression arrays. CONCLUSION: KIF14 and TLN1 are modulators of response to docetaxel and potential therapeutic targets in triple negative breast cancer.