Purpose: Colorectal cancer (CRC) is a common malignancy associated with high morbidity and mortality. Heat shock 70 kDa protein 4 (HSPA4) has been shown to exert regulatory roles during tumor progression in different cancer types. Here, we investigated the expression and cellular functions of HSPA4 in CRC.
Materials and Methods: Expression of HSPA4 in CRC tissues and paracancerous tissues was analyzed by RT-qPCR and immunohistochemistry IHC staining. The functional roles of HSPA4 were explored using shRNA-mediated knockdown in HCT116 and RKO CRC cell lines, both in vitro and in tumor xenograft studies.
Results: HSPA4 expression was significantly increased at the RNA and protein levels in CRC tissues compared with noncancerous tissues. Moreover, HSPA4 expression was positively associated with tumor stage and its high expression of HSPA4 indicated poor patient prognosis. In vitro studies established that HSPA4 knockdown inhibited proliferation and migration, causing arrest in the G2-phase of the cell cycle along with increased levels of apoptosis. This phenotype was recapitulated in vivo where HSPA4 knockdown suppressed xenograft growth. Mechanistic investigations showed silencing of HSPA4 reduced activation of the PI3K, Akt signaling axis while also downregulating the cell cycle progression markers, CCND1 and CDK6. Similarly, there was altered expression of apoptosis-related proteins consistent with the increase in apoptosis.
Conclusion: Our findings demonstrate clinical significance for HSPA4 in CRC, further showing that HSPA4 contributes to CRC tumorigenesis through effects on proliferation, migration and survival. Thus, HSPA4 represents a novel prognostic indicator as well as a promising therapeutic target in CRC.
Keywords: CRC, HSPA4, proliferation, apoptosis, migration