As-Cd-Pb Mixture Induces Cellular Transformation via Post-Transcriptional Regulation of Rad51c by miR-222.

BACKGROUND/AIMS: Exposure to heavy metals is today a threat to society. The understanding of the molecular processes related to diseases related to exposure to metals mixture involve changes in the expression of microRNAs. Changes on microRNAs expression may alter several cellular processes, among them, DNA repair inhibition has been described as an essential event leading to the initiation of metal-induced carcinogenesis. METHODS: We evaluate the miR-222 expression in the two-stage transformation Balb/c 3T3 cell assay treated with As-Cd-Pb mixture. RESULTS: We could appreciate that up-regulation of miR-222 reduces the expression both gene and as a protein expression of Rad51c by RT-PCR and immunoblot, respectively. CONCLUSION: Here, we demonstrate that the mixture of As-Cd-Pb at epidemiologically relevant concentrations induces miR-222 up-regulation, which directly negatively regulates Rad51c expression and impairs homologous recombination of DNA during the initiation stage of cell transformation. This inhibition triggers morphological transformation in a murine two-stage Balb/c 3T3 cell assay, suggesting that this small RNA acts as an initiator of the carcinogenesis process.