PKIB expression strongly correlated with phosphorylated Akt expression in breast cancers and also with triple-negative breast cancer subtype.

The cAMP-dependent protein kinase inhibitor-β (PKIB) is presumed to be one of the regulatory factors controlling the cAMP-dependent protein kinase A signaling pathway. The aim of this study was to investigate the frequency and patterns of PKIB overexpression in human breast cancer. We also examined the relationship between PKIB and phosphorylated Akt (pAkt) expression in the tumors. Using immunohistochemical techniques, we examined the expression of PKIB, ER, PR, HER2, and pAkt in 148 primary human breast carcinomas. We then analyzed the relationships between PKIB expression and that of pAkt, ER, PR, and HER2, as well as between PKIB expression and various clinicopathological characteristics. We assessed 64 and 27 cases, respectively, as positive for either PKIB or pAkt expression; 20 cases were positive for both PKIB and pAkt. We observed a significant positive correlation between the expression of PKIB and that of pAkt (P = 0.006). We showed by immunohistochemical analyses that PKIB expression was positively correlated with triple-negative breast cancers (P = 0.0004). These findings provide evidence for PKIB overexpression associated with pAkt expression. Furthermore, PKIB expression was strongly correlated with triple-negative breast cancer, suggesting that PKIB expression might contribute to the tumor behavior and development of breast cancer.