Figure 7: miR-424(322) enhances the efficacy of chemotherapy by activating cytotoxic T cells and reducing regulatory cytokine secretions in ID8 tumours.

ID8 cells with stable overexpression of miR-424(322) were injected into syngeneic C57BL/7 mice, followed by cisplatin or vehicle (Veh) treatment. The T cells were harvested from regressing tumours and stained with various markers. (a,b) IFN-γ+/CD8+ T cells from tumour of ID8 tumour-bearing mice were isolated and counted. Cisplatin treatment significantly increased the number of IFN-γ+/CD8+ T cells in the C57BL/7 mice with miR-424(322) overexpressing tumours. t-test, *P≤0.05, **P≤0.01. Bar graphs are shown as the mean±s.e.m. (n=12 mice per group). (c–g) Relative expression levels of PD-1, PD-L1, CD80 and IFN-γ from tumour of ID8 tumour-bearing mice were determined via qRT-PCR assay. Cisplatin treatment significantly repressed the mRNA levels of PD-L1 and CD80 and increased the mRNA levels of CD8, TNF-α and IFN−γ in the C57BL/7 mice with miR-424(322)-overexpressing tumours. t-test, *P≤0.05, **P≤0.01, ***P≤0.001. Bar graphs are shown as the mean±s.e.m. (n=12 mice per group). (h–k) Circulating serum from C57BL/7 mice was assayed for IL-10, TNF-α, IFN-γ and TGF-β using a cytokine ELISA assay. Cisplatin treatment significantly inhibited the secretion of IL-10 and promoted the secretion of TNF-α and IFN-γ in the C57BL/7 mice with miR-424(322)-overexpressing tumours. t-test, *P≤0.05, **P≤0.01. Bar graphs are shown as the mean±s.e.m. (n=12 mice per group). (l) Schematic representation of the biological and functional interactions between PD-L1 and chemoresistance through the miR-424(322) regulatory cascade.