Confirmatory evidence that miR-15a and miR-16 regulate BCL2 at the post-transcriptional level

The microRNAs miR-15a and miR-16 are key regulators of the anti-apoptotic oncogene BCL2, playing a significant role in tumorigenesis. These miRNAs function as tumor suppressors by directly targeting BCL2, whose overexpression contributes to cell survival and resistance to therapy in multiple malignancies, including chronic lymphocytic leukemia (CLL). The downregulation or deletion miR-15a/miR-16-1 cluster located on chromosome 13q occurs in about 50% of CLL patients and leads to the overexpression of the oncogenic BCL2, contributing to the survival and proliferation of cancer cells. In this confirmatory study, we provide additional evidence supporting the mechanism by which these miRNAs mediate the inhibition of BCL2 translation, leading to reduced levels of BCL2 protein with no significant effect on BCL2 mRNA degradation. This mechanism has been previously established as a critical pathway in the regulation of apoptosis, particularly in cancer cells where BCL2 overexpression is often associated with resistance to cell death. Our findings reinforce the notion that miRNAs, such as miR-15 and miR-16, bind to the 3-UTR of BCL2 messenger RNA (mRNA), specifically repressing its translation without inducing mRNA degradation. The results from our study align with previous research, confirming that the miRNA-mediated inhibition of BCL2 translation serves as a precise regulatory mechanism that targets protein synthesis rather than mRNA stability. These findings highlight the role of miRNAs in fine-tuning post-transcriptional gene regulation, offering a targeted approach to downregulate oncogenic proteins like BCL2 without disrupting the underlying mRNA, which could be leveraged for more refined therapeutic strategies.