MiR-34a Suppresses p53-Mediated Tumorigenesis and Epithelial-Mesenchymal Transition in Non-Small Cell Lung Cancer

Ariane Kubena

Introduction. Lung cancer is the leading cause of cancer-related deaths worldwide, and 85% of cases are diagnosed as Non-Small Cell Lung Cancer (NSCLC). 70% of NSCLC diagnoses present at an advanced stage with a 15% 5-year survival rate and chemotherapeutic resistance9. Research has shown that miR-34a is downregulated in NSCLC, affecting its standard pro-apoptic and anti-metastatic activity6. The proposed mechanism of miR-34a includes feedback loops with both the p53 inhibitor, HDM41, and the EMT-inducing factor, ZNF2812. This level of post-transcriptional regulation of cancer pathways offers potential for RNAi combination therapy in the targeting of known pathway mutations in NSCLC patients3. Methods. To determine the mechanism by which HDM4 evades miR-34a regulation in NSCLC, a luciferase assay was performed on HCT 116 cancer cells following transfection with miR-34a. RNA sequencing data and PCR analysis was obtained from lung adenocarcinoma samples1. To determine if ZNF281 downregulation via SNAIL was dependent on p53 directly or on p53-induced miR-34a, western blot analysis was performed on HCT 116 cancer cells treated with anti-miRNA oligonucleotide—antagomir2. The combination RNAi therapy design was comprised of cisplatin-containing liposomes attached to siKRAS and miR-34a RNA films, a poly L-arginine polycation, and a hyaluronic acid coat. The experiment involved weekly tail vein injections of Cisplatin alone and RNAi combination therapy over the course of four weeks. Mice lung tissue was excised to analyze miR-34a expression via PCR3. Results. The shorter isoform of HDM4 showed a deficiency of miR-34a binding sites in its 3’ UTR. Data from lung adenocarcinoma samples demonstrated an inverse correlation between full-length HDM4 and miR-34a1. MiR-34a-specific antagomirs showed reduced ZNF281 downregulation in p53-induced cells2. Mice survival was increased from median survival of 39.5 days with treatment of Cisplatin only to 48.5 days with RNAi combination therapy3. Conclusion. Studies show that miR-34a is an important mediator in the regulation of NSCLC pathogenesis. Its suppressive effects are supported by its capacity to repress p53 inhibitors and downregulate EMT-inducing factors, which may contribute to therapeutic efficacy in the treatment of NSCLC.

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