Inhibition of c-FLIPL expression by miRNA-708 increases the sensitivity of renal cancer cells to anti-cancer drugs

Abstract

Dysregulation of the anti-apoptotic protein, cellular FLICE-like inhibitory protein (c-FLIP), has been associated with tumorigenesis and chemoresistance in various human cancers. Therefore, c-FLIP is an excellent target for therapeutic intervention. MicroRNAs (miRNAs) are small non-coding RNAs that are involved in tumorigenesis, tumor suppression, and resistance or sensitivity to anti-cancer drugs. However, whether miRNAs can suppress c-FLIPL expression in cancer cells is unclear. The aim of this study was to identify miRNAs that could inhibit the growth of renal cancer cells and induce cell death by inhibiting c-FLIPL expression. We found that MiRNA-708 and c-FLIPL expression were inversely correlated. While c-FLIPL expression was upregulated, miRNA-708 was rarely expressed in renal cancer cells. Luciferase reporter assays demonstrated that miRNA-708 negatively regulated c-FLIPL expression by binding to the miRNA-708 binding site in the 3′ untranslated region (3′UTR) of c-FLIPL. Ectopic expression of miRNA-708 increased the accumulation of sub-G1 populations and cleavage of procaspase-3 and PARP, which could be prevented by pretreatment with the pan-caspase inhibitor, Z-VAD. Ectopic expression of miRNA-708 also increased the sensitivity to various apoptotic stimuli such as tumor necrosis factor-related apoptosis-inducing ligand, doxorubicin (Dox), and thapsigargin in Caki cells. Interestingly, miRNA-708 specifically repressed c-FLIPL without any change in c-FLIPs expression. In contrast, inhibition of endogenous miRNA-708 using antago-miRNAs resulted in an increase in c-FLIPL protein expression. The expression of c-FLIPL was upregulated in renal cell carcinoma (RCC) tissues compared to normal tissues. In contrast, miRNA-708 expression was reduced in RCC tissues. Finally, miRNA-708 enhanced the tumor-suppressive effect of Dox in a xenograft model of human RCC. In conclusion, miRNA-708 acts as a tumor suppressor because it negatively regulates the anti-apoptotic protein c-FLIPL and regulates the sensitivity of renal cancer cells to various apoptotic stimuli.

Restoration of microRNA‐708 sensitizes ovarian cancer cells to cisplatin via IGF2BP1/Akt pathway

“…We found that reexpression of miR‐708 significantly reduced the IC 50 values for cisplatin in parental and cisplatin‐resistant ovarian cancer cell lines. In line with our findings, it was reported that ectopic expression of miRNA‐708 increased the sensitivity of renal cancer cells to anti‐cancer drugs (Kim et al, ). Taken together, our data suggest that miR‐708 downregulation contributes to the acquisition of cisplatin resistance in ovarian cancer cells.…”

Cis-regulatory mutations associate with transcriptional and post-transcriptional deregulation of the gene regulatory program in cancers

“…We did not observe a correlation between the number of potential target genes for a miRNA and the number of cohorts where it is predicted ( Figure S20). All these miRNAs are derived from precursors of already established oncomiRs or tumor suppressor miRNAs, or known to be involved in immune response or inflammation [50][51][52][53][54][55][56][57][58][59][60][61]. Note that hsa-miR-17-3p, hsa-miR-17-5p, hsa-miR-18a-3p, hsa-miR-18a-3p, hsa-miR-20a-3p, hsa-miR-20a-5p, and hsa-miR-92a-1-5p are part of a single miRNA cluster on chromosome 13 and this polycistronic cluster (known as miR-17-92) is well known to be composed of oncomiRs involved in proliferation and tumor angiogenesis, and reducing apoptosis of cancer cells [50].…”

miR-708-5p: a microRNA with emerging roles in cancer

“…In renal cell carcinoma (RCC), miR-708-5p suppresses tumorigenicity by targeting multiple pro-survival genes [ 175 , 176 ]. It was revealed that miR-708-5p has reduced expression in RCC tumor samples, and low expression is associated with advanced tumors [ 175 ].…”

“…It was revealed that miR-708-5p has reduced expression in RCC tumor samples, and low expression is associated with advanced tumors [ 175 ]. miR-708-5p restoration resulted in decreased cell viability, migration, invasion, and proliferation while also inducing apoptosis in RCC cell lines [ 175 , 176 ]. miR-708-5p treatment in xenograft rodent models reduced tumor burden and synergistically suppressed tumor growth when used in combination with the chemotherapeutic doxorubicin [ 175 , 176 ].…”

“…Although BMI1 suppression helps explain the anti-proliferative properties of miR-708-5p, the ability of miR-708-5p to induce apoptosis independent of doxorubicin suggests alternative pro-survival targets. In fact, miR-708-5p targets two anti-apoptotic genes, baculoviral inhibitor of apoptosis repeat-containing 5 ( survivin ), and cellular FLICE-like inhibitory protein ( cFLIP ) [ 175 , 176 ]. Survivin is a member of the inhibitor of apoptosis (IAP) family of proteins that impede caspase-mediated cell death [ 179 ].…”