UC Riverside

Radiotherapy constitutes a major therapeutic modality for early management of breast cancer. Despite the high efficacy in treating breast cancer (BC), radiation resistance and tumor recurrence are major hurdles in breast cancer radiotherapy. Herein, stable isotope labeling by amino acids in cell culture (SILAC) was employed, along with the parallel-reaction monitoring (PRM)-based targeted quantitative proteomic method, to examine the differences in kinase protein expression in MCF-7 and MDA-MB-231 breast cancer cells and their corresponding radioresistant C6 and C5 clones. We quantified the relative protein expression levels of 300 and 281 kinases in C5/MDA-MB-231 and C6/MCF-7 pairs of breast cancer cells, respectively. We also showed that TAF9, which was one of the differentially expressed kinases, enhances radiation resistance in breast cancer cells. Moreover, a correlation analysis of gene expression suggested TAF9s role in upregulating the expression of genes involved with radioresistance. Overall, our study uncovered a large number of differentially expressed kinases accompanied with the acquisition of radioresistance and revealed a role of TAF9 in promoting radioresistance in breast cancer.