RT Journal Article SR Electronic T1 The Expression of Immune Checkpoint Receptors and Ligands in the Colorectal Cancer Tumor Microenvironment JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 4895 OP 4905 DO 10.21873/anticanres.15303 VO 41 IS 10 A1 PRAJWAL NEUPANE A1 KOSAKU MIMURA A1 SHOTARO NAKAJIMA A1 HIROKAZU OKAYAMA A1 MISATO ITO A1 AUNG KYI THAR MIN A1 KATSUHARU SAITO A1 HISASHI ONOZAWA A1 SHOTARO FUJITA A1 WATARU SAKAMOTO A1 MOTONOBU SAITO A1 ZENICHIRO SAZE A1 TOMOYUKI MOMMA A1 KOJI KONO YR 2021 UL http://ar.iiarjournals.org/content/41/10/4895.abstract AB Background/Aim: The limited efficacy of immune checkpoint inhibitors in colorectal cancer (CRC) is likely due to immunosuppressive mechanisms including T cell exhaustion caused by inhibitory immune checkpoints in the tumor microenvironment. Materials and Methods: We investigated the expression status of the inhibitory immune checkpoint receptors on tumor-infiltrating T cells and their ligands on tumor cells by flow cytometry and immunohistochemistry, using surgically-resected specimens of CRC. Results: Flow cytometry analysis indicated that TIM-3, TIGIT, and PD-1 were expressed on tumor-infiltrating CD4+ (8.3%, 56.0%, 26.1%) and CD8+ T cells (8.2%, 51.6%, 23.5%), and CRC cells abundantly expressed PD-L1, CEACAM-1, and CD155 (2.2%, 77.0%, 46.8%). Immunohistochemical analysis revealed that the tumor proportional score of PD-L1, CEACAM-1, and CD155 was 42.4%, 54.2%, and 52.1%, respectively. Conclusion: PD-1, TIM-3, and TIGIT axes may reduce T cell function in the CRC tumor microenvironment.