TNNC2 is a Microsatellite Instability-Related Gene for Response to Immune Checkpoint Blocking Therapy in Colorectal Cancer and Contributes to Tumor Progression

Abstract

Background: Microsatellite instability (MSI) status may alter the tumor microenvironment (TME) and can affect the effectiveness of immune checkpoint blocking (ICB) immunotherapy in colorectal cancer (CRC) patients. This study aimed to determine the MSI-related genes as biomarkers for response to ICB therapy in CRC. Methods: The role and signature of MSI-related genes in CRC were analyzed through the data acquirement (LinkedOmics database), copy number alteration (CNA) assay (cBioPortal database), Association immune cells and Troponin C2 (TNNC2) levels analysis (Immune Cell Abundance Identifier (immuCellAI)), Tumor Immune Estimation Resource (TIMER) and Gene Expression Profiling Interactive Analysis (GEPIA). Silencing of TNNC2 was constructed in vitro and used for cell count kit 8 (CCK-8). CCK-8 was used to detect cell growth after relevant treatments. The cell apoptosis was assessed using the Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) apoptosis detection kit. The wound healing assay was used to determine cell migration. The enrichment of the TNNC2 pathways was performed using Gene Set Enrichment Analysis (GSEA). Results: The results showed that a total of 15 MSI-related genes were identified, including TNNC2 and ACSL6. Then, TNNC2 high-frequency amplification was found in the CRC. The expression of TNNC2 was lower in MSI-high group than MSI-low or microsatellite stability (MSS) group (p < 0.05). Compared to the high expression of TNNC2, the low expression of TNNC2 is more conducive to ICB response (p < 0.05). Additionally, TNNC2 regulated immune cell infiltration and ICB immunotherapy-related genes. Furthermore, TNNC2 was upregulated in CRC tissues and cell lines (p < 0.05). Cellular function assays showed that silence of TNNC2 decreased cell proliferation and migration, and induced apoptosis in CRC cells. Biological analysis also showed that TNNC2 plays a critical role in the activation of Wnt/β-catenin and PPAR in CRC. Conclusion: Hence, it can be concluded that TNNC2 is an MSI-related gene in response to ICB therapy in colorectal cancer. This study provided a better understanding of potential biomarker of ICB response and underlying mechanism in CRC, which is beneficial for CRC diagnosis and treatment research.