In breast cancer tissues, the phospho-p90RSK expression was highly correlated with phospho-c-Raf (p = 0.012), phospho-MEK (p = 0.003), phospho-ERK (p = 0.009), and its downstream molecule phospho-ELK (p = 0.079), suggesting that the expression of phospho-p90RSK may reflect the whole Raf/MEK/ERK pathway and thereby mediating chemotherapy response. This evidence concerns the gene RPS6KA1 and breast carcinoma.