GDC-0575, a CHK1 Inhibitor, Impairs the Development of Colitis and Colitis-Associated Cancer by Inhibiting CCR2(+) Macrophage Infiltration in Mice

BACKGROUND: Checkpoint kinase 1 (CHK1) plays an important role in DNA damage response and cell cycle progression. Thus, targeting CHK1 is an efficient strategy for cancer therapy. PURPOSE: The present study aimed to investigate the potential therapeutic effects of GDC-0575, a CHK1-specific inhibitor, in colitis-associated cancer (CAC) and colitis. METHODS: We established a DSS-induced acute colitis model and an azoxymethane/dextran sodium sulfate (DSS)-induced CAC model using mice and tested the effect of GDC-0575 on them. Flow cytometry and immunofluorescence were employed to investigate the infiltration of immune cells, and inflammatory cytokine expression in the colon of mice with CAC or colitis was investigated using ELISA and qPCR. We also investigated the correlation between CHK1 and CCL2/CCR2 in human colorectal cancer (CRC) tissues. RESULTS: Administration of GDC-0575 significantly inhibited CHK1 expression in the colon and dramatically impaired the development of CAC and colitis in mice. Moreover, the inhibition of CHK1 expression resulted in efficient inhibition of infiltration by iNOS-positive macrophages, but had no significant effect on CD4 T cells, CD8 T cells, and myeloid-derived suppressor cells (MDSCs). Significant downregulation of TNF-α, IL-6, and IL-1β and dramatic upregulation of IL-10 were observed in the colons of both mice with CAC and colitis treated with GDC-0575. CCL2 expression was also downregulated by GDC-0575 in both mice with CAC and colitis; this was followed by the inhibition of CCR2(+) macrophage infiltration in the colon. Furthermore, we report a positive correlation between CHK1 expression and CCL2/CCR2 expression in the malignant tissues of patients with CRC. CONCLUSION: Taken together, we infer that GDC-0575 impairs the development of CAC and colitis by regulating cytokine expression and inhibiting CCR2(+) macrophage infiltration in mice colon.