CXCL8, overexpressed in colorectal cancer, enhances the resistance of colorectal cancer cells to anoikis

Abstract

Anoikis is a form of apoptosis which occurs when anchorage-dependent cells either show loss of adhesion or inappropriate adhesion. Only a few cancer cells that detach from the primary site of the tumor acquire the ability to resist anoikis and form metastasis. The mechanism underlying the resistance of colorectal cancer (CRC) cells to anoikis remains unclear. Interleukin-8 (alternatively known as CXCL8) is associated with CRC angiogenesis and progression. Here, we found that a high abundance of CXCL8 or TOPK strongly correlated with poor overall and disease-free survival of 186 patients with CRC. A combination of high CXCL8 and high TOPK expressions had the worst prognosis. We showed that CXCL8 expression was negatively correlated with anoikis in CRC cells. CXCL8 treatment enhanced the resistance of CRC cells to apoptosis, which was accompanied by the increase of TOPK, and the activation of AKT and ERK. Moreover, we demonstrated that the inhibition of either ERK or AKT by specific chemical inhibitors attenuated the CXCL8-mediated resistance to anoikis. Treatment with AKT inhibitor abolished the effects of CXCL8 on TOPK expression, suggesting that TOPK was downstream of AKT in the process of anoikis. Taken together, we demonstrated that CXCL8 is strongly implicated in the resistance of CRC cells to anoikis, and that the AKT, TOPK and ERK pathway may be a potential therapeutic target for CRC.