Investigating the potential role of miR-451a as a tumor suppressor in immunogenic cell death induction and dendritic cell maturation in colorectal cancer cell lines.

Background: Colorectal cancer (CRC) remains a leading cause of cancer-related mortality, as conventional therapies are frequently hampered by treatment resistance and the presence of an immunosuppressive tumor microenvironment (TME). Immunotherapy, particularly strategies based on immunogenic cell death (ICD) induction can activate the TME by enhancing tumor immunogenicity and promoting T cell infiltration, potentially improving the efficacy of cancer immunotherapies in CRC. This study investigates the potential of miR-451a as a tumor suppressor in the release of ICD associated damage-associated molecular patterns in CRC cell lines and maturation of dendritic cells (DCs).

Methods: Human CRC cell lines (SW48, SW1116, SW480, and Caco-2) were treated with oxaliplatin alone or transfected with the hsa-miR-451a mimic, scrambled miRNA, or a combination of the hsa-miR-451a mimic and oxaliplatin for 48 h. Cell viability was measured using MTT assays, and apoptosis was assessed through annexin V and PI staining. Flow cytometry was employed to evaluate calreticulin (CRT) levels on the cell surface and to analyze the percentages of CD11c + CD86 + CD80 + mature DCs. Additionally, ATP levels were quantified using a luminescence assay, and HMGB1 levels were measured by ELISA.

Results: Our results demonstrated that the overexpression of miR-451a significantly increased apoptosis and CRT surface exposure in all four CRC cell lines, like the effects observed with oxaliplatin, when compared to both the control and scrambled miRNA groups (P < 0.05, P < 0.01, P < 0.001, and P < 0.0001). However, the combination of miR-451a with oxaliplatin did not yield synergistic effects across all cell lines. Additionally, the ability of miR-451a to increase extracellular ATP and HMGB1 levels, as well as its effect on DC maturation, varied among cell lines.

Conclusions: The findings of this study presents novel insights into the potential role of miR-451a as a tumor-suppressive agent in CRC. By examining its effect on ICD across four different CRC cell lines, we provide a comprehensive analysis of its impact on both tumor cells and the immune system. Our results suggest that miR-451a induce certain characteristics of the ICD response, which vary depending on the cellular context.