MT2A Promotes Oxaliplatin Resistance in Colorectal Cancer Cells

We aimed to understand the molecular mechanism underlying the incidence of Oxaliplatin resistance in colorectal cancer. The Oxaliplatin-resistant (OR) HT29 colorectal cell line was established by long-term exposure to Oxaliplatin. Cell viability and proliferation were determined by the 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide and direct counting assays, respectively. Transcript level of metallothionein 2A (MT2A) was measured by real-time polymerase chain reaction. Protein levels of MT2A, BRCA1-associated RING domain 1 (BARD1), BRCA1, and β-actin were quantified by immunoblotting. Direct interaction between MT2A with BARD1 and BRCA1 was analyzed by co-immunoprecipitation. Colocalization between of MT2A and BARD1 was determined by immunofluorescence. MT2A was upregulated in OR cells at both transcript and protein levels. Knockdown of MT2A in HT29 OR cells improved sensitivity to Oxaliplatin, while ectopic overexpression of MT2A conferred HT29 cells relative resistance to Oxaliplatin. We further demonstrated that MT2A interacted with and positively regulated BARD1/BRCA1 in colorectal cancer cells. BARD1 overexpression partially restored the compromised Oxaliplatin resistance elicited by MT2A deficiency in terms of both cell proliferation and viability. Our data highlighted the critical contributions of MT2A-BARD1/BRCA1 in Oxaliplatin resistance in colorectal cancer cells.