Immune microenvironmental heterogeneity according to tumor DNA methylation phenotypes in microsatellite instability-high colorectal cancers.

The detailed association between tumor DNA methylation, including CpG island methylation, and tumor immunity is poorly understood. CpG island methylator phenotype (CIMP) is observed typically in sporadic colorectal cancers (CRCs) with microsatellite instability-high (MSI-H). Here, we investigated the differential features of the tumor immune microenvironment according to CIMP status in MSI-H CRCs. CIMP-high (CIMP-H) or CIMP-low/negative (CIMP-L/0) status was determined using MethyLight assay in 133 MSI-H CRCs. All MSI-H CRCs were subjected to digital pathology-based quantification of CD3 + /CD8 + /CD4 + /FoxP3 + /CD68 + /CD204 + /CD177 + tumor-infiltrating immune cells using whole-slide immunohistochemistry. Programmed death-ligand 1 (PD-L1) immunohistochemistry was evaluated using the tumor proportion score (TPS) and combined positive score (CPS). Representative cases were analyzed using whole-exome and RNA-sequencing. In 133 MSI-H CRCs, significantly higher densities of CD8 + tumor-infiltrating lymphocytes (TILs) were observed in CIMP-H tumors compared with CIMP-L/0 tumors. PD-L1 TPS and CPS in CIMP-H tumors were higher than in CIMP-L/0 tumors. Next-generation sequencing revealed that, compared with CIMP-L/0 tumors, CIMP-H tumors had higher fractions of CD8 + T cells/cytotoxic lymphocytes, higher cytolytic activity scores, and activated immune-mediated cell killing pathways. In contrast to CIMP-L/0 tumors, most CIMP-H tumors were identified as consensus molecular subtype 1, an immunogenic transcriptomic subtype of CRC. However, there were no differences in tumor mutational burden (TMB) between CIMP-H and CIMP-L/0 tumors in MSI-H CRCs. In conclusion, CIMP-H is associated with abundant cytotoxic CD8 + TILs and PD-L1 overexpression independent of TMB in MSI-H CRCs, suggesting that CIMP-H tumors represent a typical immune-hot subtype and are optimal candidates for immunotherapy in MSI-H tumors.

Kim JH ，Hong J ，Lee JA ，Jung M ，Choi E ，Cho NY ，Kang GH ，Kim S ... -  《-》

Clinical significance of programmed cell death-ligand 1 expression and the immune microenvironment at the invasive front of colorectal cancers with high microsatellite instability.

Immunotherapy is reportedly effective in colorectal cancers (CRCs) with high microsatellite instability (MSI-H); however, the specific cell types that respond to immune checkpoint therapy are unclear. Herein, we aimed to examine the expression of programmed cell death-ligand 1 (PD-L1) and related proteins in MSI-H and microsatellite-stable (MSS) CRCs to investigate the immune microenvironment at the tumor's invasive front. The MSI status was retrospectively assessed in 499 patients undergoing surgical resection of primary CRC; of these, 48 were classified as MSI-H. Propensity score matching was performed, and tissues from 36 and 37 patients with MSI-H and MSS CRCs, respectively, were immunohistochemically evaluated for PD-L1, PD-1, CD8 and CD68. PD-L1 expression was evaluated separately for tumor cells (PD-L1 [T]) and tumor-infiltrating myeloid cells in the stroma (PD-L1 [I]). PD-L1 (T) was positive in only 5.4% and 36.1% of MSS and MSI-H CRCs, while PD-L1 (I) was positive in 27% and 72.2% of these CRCs, respectively. The PD-L1 (T) and PD-L1 (I) expression levels in MSI-H CRCs significantly correlated with poor differentiation, lymphatic invasion and vascular invasion (p < 0.05), and with early-stage adenocarcinoma and high budding grade (p < 0.05), respectively. Significantly more PD-L1 (I), CD8-positive cells and CD68-positive macrophages were present at the invasive front than in the central tumor in MSI-H CRCs (p < 0.005). PD-L1 was expressed on both tumor cells and CD68/CD163-positive (M2) macrophages at the invasive front of MSI-H CRCs. In conclusion, PD-L1-positive tumor cells and M2-type tumor-associated macrophages may contribute to tumor invasion and immune escape at the invasive front.

Korehisa S ，Oki E ，Iimori M ，Nakaji Y ，Shimokawa M ，Saeki H ，Okano S ，Oda Y ，Maehara Y ... -  《-》

Differential clinicopathological features in microsatellite instability-positive colorectal cancers depending on CIMP status.

Bae JM ，Kim MJ ，Kim JH ，Koh JM ，Cho NY ，Kim TY ，Kang GH ... -  《-》

Characterisation of PD-L1-positive subsets of microsatellite-unstable colorectal cancers.

Kim JH ，Park HE ，Cho NY ，Lee HS ，Kang GH ... -  《-》

The CpG island methylator phenotype and chromosomal instability are inversely correlated in sporadic colorectal cancer.

Goel A ，Nagasaka T ，Arnold CN ，Inoue T ，Hamilton C ，Niedzwiecki D ，Compton C ，Mayer RJ ，Goldberg R ，Bertagnolli MM ，Boland CR ... -  《GASTROENTEROLOGY》