Role of the cGAS-STING pathway in regulating the tumor-immune microenvironment in dMMR/MSI colorectal cancer

• DOI: 10.1007/s00262-022-03200-w
• Publication Date: 2022-04-16T11:11:21Z
• Authors: Akinao Kaneta; Shotaro Nakajima; Hirokazu Okayama; Takuro Matsumoto; Katsuharu Saito; Tomohiro Kikuchi; Eisei Endo; Misato Ito; Kosaku Mimura; Yasuyuki Kanke; Motonobu Saito; Zenichiro Saze; Shotaro Fujita; Wataru Sakamoto; Hisashi Onozawa; Tomoyuki Momma; Shinji Ohki; Koji Kono
• Keywords: 0301 basic medicine; Chemotactic Factors; Membrane Proteins; DNA Mismatch Repair; Nucleotidyltransferases; 3. Good health; 03 medical and health sciences; 617; Tumor Microenvironment; Humans; Microsatellite Instability; Interferons; Colorectal Neoplasms

Deficient mismatch repair (dMMR)/microsatellite instability (MSI) colorectal cancer (CRC) has high immunogenicity and better prognosis compared with proficient MMR (pMMR)/microsatellite stable (MSS) CRC. Although the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has been considered to contribute to the high number of CD8+ TILs, its role in dMMR/MSI CRC is largely unknown. In this study, to examine the role of the cGAS-STING pathway on the recruitment of CD8+ TILs in dMMR/MSI CRC, we used public datasets and clinical tissue samples in our cohorts to evaluate the expression of cGAS, STING, and CD8+ TILs in pMMR/MSS and dMMR/MSI CRCs. According to the analysis of public datasets, the expression of cGAS-STING, CD8 effector gene signature, and CXCL10-CCL5, chemoattractants for CD8+ TILs which regulated by the cGAS-STING pathway, was significantly upregulated in dMMR/MSI CRC, and the expression of cGAS-STING was significantly associated with the expression of CD8 effector gene signature. Immunohistochemistry staining of the clinical tissue samples (n = 283) revealed that cGAS-STING was highly expressed in tumor cells of dMMR CRC, and higher expression of cGAS-STING in tumor cells was significantly associated with the increased number of CD8+ TILs. Moreover, we demonstrated that the downregulation of MMR gene in human CRC cell lines enhanced the activation of the cGAS-STING pathway. Taken together, for the first time, we found that dMMR/MSI CRC has maintained a high level of cGAS-STING expression in tumor cells, which might contribute to abundant CD8+ TILs and immune-active TME.