(773) Modulation of the immunogenic landscape in colorectal cancer by mitochondrial DNAJC15 protein

Introduction/Rationale: The tumor microenvironment (TME) plays a pivotal role in cancer progression by orchestrating interactions between cancer cells and surrounding immune and non-immune cells through metabolic reprogramming. Methylation-controlled J protein (MCJ, or DNAJC15) is a negative regulator of mitochondrial respiration, but its role in tumor metabolism remains unclear.

Methods: MCJ-deficient cancer cell lines were established using siRNA and compared to parental MCJ-expressing cells. Transcriptomic profiling was used to analyze alterations in metabolic and immune-related gene expression. Cellular metabolic activity and ATP production were determined by Seahorse analysis. Cell growth was evaluated in vitro and in vivo using immunocompetent mice and T-cell-deficient athymic mice. Alterations in TME and immune cell infiltration were assessed by flowcytometry and immunohistochemistry. Bioinformatic analysis was used to validate the results in human colorectal cancer.

Results: MCJ deficiency led to enhanced mitochondrial respiration and ATP production. Despite normal growth in vitro, MCJ-deficient tumor cells exhibited curtailed growth in immunocompetent mice. However, these cells grew comparably to controls in T-cell-deficient athymic mice. Tumors lacking MCJ exhibited increased immune cell infiltration and immunogenicity. Transcriptomic analysis revealed a metabolic shift from glycolysis-dominant and hypoxic conditions to a state favoring oxidative phosphorylation, which correlated with upregulation of immune-related pathways and enhanced anti-tumor immune responses. Bioinformatic analysis in human colorectal cancer patients revealed that low MCJ expression correlated with increased tumor mutational burden, microsatellite instability, and immune cell infiltration, demonstrating the clinical relevance of MCJ expression in the context of colon adenocarcinoma.

Conclusion: These findings suggest MCJ as a promising target for metabolic immunotherapy in cancer.