Abstract 1743: miR-1307-5p reverses cisplatin resistance in oral squamous cell carcinomas (OSCC) by targeting EHF, a modulator of stemness genes
Authors: Patel Aditi , Patel Shanaya , Lotia Shreya , Tanavde Vivek 
Published: April 2023

Abstract
Background: We have previously identified miR-1307-5p is exclusively expressed in OSCC tumors and is significantly upregulated in chemo-resistant patients. In this study, we investigate the mechanism of miR-1307-5p in conferring therapeutic refractoriness and demonstrate reversal of cisplatin induced chemoresistance. This study provides a potentially new therapeutic target for treating recurrent oral carcinomas.
Methods: Expression of miR-1307-5p was validated in OSCC patients (n=86), OECM1 cell line and cisplatin resistant CD44+ subpopulation. miR-1307-5p was knocked down in OECM1 and CD44+ cells and its effect on cell proliferation, apoptosis, cell cycle, migration, invasion and sphere forming abilities was measured. We examined the transcriptome of these patients (n=30) and combined this data with The Cancer Genome Atlas (TCGA) dataset for target prediction (TargetScan) and network analysis (Ingenuity Pathway Analysis). The hub genes were considered to be potential targets of miR-1307-5p and were validated by luciferase assay and Western Blotting.
Results: Sequencing analysis revealed exclusive expression of miR-1307-5p in the OSCC patient cohort with significant upregulation in chemo-resistant cases (FC:4.82 ± 2.38, p-value:0.01). miR-1307-5p upregulation separated the chemoresistant and remission cohorts (p&lt;0.05). Transfection-mediated silencing of miR-1307-5p in OECM1(FC:0.009 ± 1.5, p:0.01) and CD44+ (FC:0.06 ± 2.3, p:0.01) cells restrained the cell proliferation rates (p&lt;0.01) and revealed a significant sub G0 population of OECM1 (20±5%) and CD44+(18.7±3%) cells, indicating early apoptosis. A significant Annexin V+/PI- population (OECM1: 40%±3.36%; CD44+: 23%±3.36%) confirmed induction of apoptosis, post-silencing. A 2 fold reduction in the sphere-forming ability and invasive potentials of CD44+ cells observed post-knockdown (p&gt;0.05). Combinatorial treatment of cisplatin and miR-1307-5p inhibitor reduced the proliferation rate of CD44+ cells by 66.23% in comparison to standalone treatment of the inhibitor (p:0.034). Thus, indicating role of miR-1307-5p in reversal of chemo-resistance. Gene target identification revealed miR-1307-5p could promote therapeutic refractoriness by suppressing the expression of EHF, which regulates cancer stem cell renewal by targeting Sox-2, Oct-4 and Nanog. Dual-luciferase gene reporter assay revealed direct suppression of EHF by miR-1307-5p. Further, knockdown of miR-1307-5p increased endogenous EHF mRNA and protein expression in cancer cells.
Conclusion: miR1307-5p downregulates EHF which is an inhibitor of many stemness genes like Sox-2, Oct-4 and Nanog. Knockdown of miR-1307-5p reverses Cisplatin resistance by upregulating EHF thus suppressing the emergence of cancer stem cells in OSCC.
Citation Format: Aditi Patel, Shanaya Patel, Shreya Lotia, Vivek Tanavde. miR-1307-5p reverses cisplatin resistance in oral squamous cell carcinomas (OSCC) by targeting EHF, a modulator of stemness genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1743.