Therapeutic potential for reversing miR-634-mediated cytoprotective processes to improve the efficacy of chemotherapy against oral squamous cell carcinoma

For advanced oral squamous cell carcinoma (OSCC), increasing sensitivity to chemotherapy is a major challenge in improving treatment outcomes, and targeting cytoprotective processes that lead to the chemotherapy resistance of cancer cells may be therapeutically promising. Tumor-suppressive microRNAs (miRs) can target multiple cancer-promoting genes concurrently, and are thus expected to be useful seeds for cancer therapeutics. We revealed that miR-634-meditated targeting of multiple cytoprotective process-related genes, including cellular inhibitor of apoptosis proteins 1 (cIAP1), can effectively increase cisplatin (CDDP)-induced cytotoxicity and overcome CDDP resistance in OSCC cells. The combination of topical treatment with miR-634 ointment and administration of CDDP was synergistically effective against OSCC-tumor growth in a xenograft mouse model. Furthermore, the expression of miR-634 target genes is frequently upregulated in primary OSCC tumors. Our study suggests that reversing miR-634-mediated cytoprotective processes activated in cancer cells is a potentially useful strategy to improve CDDP efficacy against advanced OSCC. We identified transcripts enriched in RNP immunoprecipitation (RIP) assays using an antibody against AGO2 in cells overexpressing miR-634 in SAS cells by microarray analysis (RIP-chip analysis). Cells were transfected with 10 nM miR-NC or miR-634 and then lysed after 24 h. The lysates were precleared and incubated with AGO2 antibody-immobilized beads or normal rabbit IgG antibody-immobilized beads for RIP. Each bead complex was washed, and RNA was isolated. RNA from AGO2-RIP (RIP) and total RNA (input) were labelled and hybridized on the Agilent 8 × 60K array. Each experiment was performed in duplicate. In both miR-NC-overexpressing cells and miR-634-overexpressing cells, the enrichment (RIP/Input) was calculated. Then, the fold change of enrichment (miR-634/miR-NC) was calculated.