Effects of Wnt signaling pathway on tertiary lymphoid structure in the immune microenvironment of colorectal cancer with different MMR subtypes

Tertiary lymphoid structure (TLS) and tumor-resident memory T cells (TRM), as the important components of tumor microenvironment, play key roles in the anti-tumor immunity and therapy functions in cancer patients. However, the TRM and TLS distribution in colorectal cancer (CRC) patients with different mismatch repair (MMR) subtypes and Wnt pathway activation, as well as their relationship, remain underexplored. In this study, we evaluated the MMR subtypes and Wnt/β-catenin using immunohistochemical staining and analyzed their relationship in a sample of 117 cases. We detected TLS distribution, quantity, and maturity in CRC samples of different MMR subtypes by multiple immunofluorescence staining and analyzed its correlation with Wnt/β-catenin pathway. We then detected TRM expression inside and outside the TLS and tumor tissues in 34 CRC samples by means of multiple immunofluorescence staining and analyzed its correlation with Wnt/β-catenin pathway. Our study showed that the proportion of β-catenin in MMR-proficient (pMMR) CRC was significantly higher than that in MMR-deficient (dMMR) CRC. The peritumoral and intratumoral TLS quantity in dMMR group was obviously higher than that in high and low pMMR-β-catenin expression groups. The intratumoral TLS quantity negatively correlated with β-catenin expression in dMMR group and low pMMR-β-catenin group, respectively. In addition, the positive rate and density of CD8+TRM in the TLS were significantly higher than that outside. The positive rate and density of CD8+TRM of tumor tissues in dMMR CRC were higher than those in pMMR CRC. Furthermore, the positive rate of CD8+TRM in tumor tissues of CRC patients in the low β-catenin expression group was higher than that in the high β-catenin expression group. Taken together, TLS and TRM cells in CRC with different Wnt classical pathway activation states and MMR subtypes could serve as a potential biomarker for the prediction of the efficacy of immunotherapy in CRC patients.