miR-424(322)503 impairs colon cancer progression driven by PTEN deficiency.

Colorectal cancer (CRC) is a leading cause of cancer-related morbidity and mortality worldwide, with molecular subtypes and signaling pathways playing critical roles in its progression. The miR-424(322)503 cluster, comprising miR-424 and miR-503, has been implicated in various malignancies, exhibiting dual roles as tumor suppressors or oncogenes depending on the context. However, its function in CRC remains poorly understood. This study investigates the role of the miR-424(322)503 cluster in CRC driven by PTEN deficiency using genetically modified mouse models. Our findings reveal that the loss of miR-424(322)503 significantly exacerbates CRC progression in PTEN-deficient mice. Double knockout (dKO) mice lacking both PTEN and miR-424(322)503 exhibited a higher number and larger size of colorectal lesions compared to PTEN-deficient counterparts. Histological analysis demonstrated increased severity of dysplasia and adenocarcinoma development in dKO mice. Mechanistically, while Wnt/β-catenin signaling remained unaltered, transcriptomic analyses highlighted dysregulation of MAPK and TGFβ pathways, alongside epithelial-to-mesenchymal transition (EMT)-related gene signatures. Protein-level validation confirmed hyperactivation of MAPK (ERK1/2 and p38) and TGFβ signaling, as well as elevated cyclin D1 expression in dKO colonic tissues. These results underscore the tumor-suppressive role of the miR-424(322)503 cluster in CRC by modulating key oncogenic pathways such as MAPK and TGFβ. Our study provides novel insights into the interplay between PTEN loss and miRNA regulation in CRC pathogenesis.