Genome-Wide CRISPR Screen Identifies a microRNA Orchestrating Pleiotropic Resistance to Targeted Therapy and T Cell Immunity in Melanoma.

Acquired resistance to both targeted therapies and immunotherapies in cancer presents major clinical challenges, yet the molecular mechanisms underlying cross-resistance remain poorly understood. We hypothesized that loss of specific microRNAs (miRNAs) could potentiate melanoma resistance to both targeted drugs and CD8+ T cell-mediated cytotoxicity. Through genome-wide miRNA CRISPR knockout screening integrated with cellular models, longitudinal clinical samples, and in vivo experiments, we identified miR-18a as a pivotal upstream regulator of pleiotropic resistance in melanoma. We show that miR-18a deficiency drives resistance through two distinct mechanisms: derepressing AJUBA-regulated Hippo signaling during MAPK inhibition, and enhancing THBS1-CD47 interactions that impair the immunological synapse between tumor cells and CD8+ T cells. Furthermore, hnRNP A1 plays an essential role in modulating miR-18a expression, thereby mediating cross-resistance. These findings suggest that targeting non-coding RNA vulnerabilities may represent a promising therapeutic strategy to overcome complex resistance mechanisms and improve clinical outcomes in melanoma.