Abstract
Background
CD248, also called endosialin or tumor endothelial marker-1 (TEM1), is markedly upregulated in almost all cancers, including colon cancers. Changes in microRNA (miRNA) profiles are one of the direct causes of cancer development and progression. In this study, we investigated whether a change in CD248 expression in colon cancer cells could induce drug resistance after chemotherapy, and we explored the relationship between miR-125b-5p levels and CD248 expression in Toll-like receptor (TLR)-modified chemoresistant colon cancer cells.
Methods
We identified the one of the downregulated miRNAs in drug-resistant HCT8 cells using Affymetrix Genechip miRNA 4.0 array process and validated the expressional change of chemoresistant HCT-116 and HT-29 cells. Interaction between Sp1 and miR-125b-5p was confirmed by miScript target protector assay. To characterize the underlying mechanisms involved in CD248 expression, we adapted the several biological analysis techniques, including RNA-binding Protein Immunoprecipitation (RIP), migration analysis, real-Time PCR, western blot analysis, and gene silencing using siRNA.
Results
TLR2/6 and TLR5 upregulation in drug-resistant colon cancer cells contributed to miR-125b-5p downregulation and Sp1-mediated CD248 upregulation via NF-κB activation. Exposure to specific TLR2/6 or TLR5 ligands enhanced the expression of mesenchymal markers as well as the migratory activity of oxaliplatin (Ox)- or 5-fluorouracil (5-Fu)-resistant colon cancer cells. The transfection of a synthetic miR-125b-5p mimic into chemoresistant cells prevented Sp1 and CD248 activation and significantly impaired invasive activity. Furthermore, Sp1 or CD248 gene silencing as well as miR-125b-5p overexpression markedly reversed drug resistance and inhibited epithelial-mesenchymal transition (EMT) in colon cancer cells.
Conclusions
Taken together, these results suggest that changes in miR-125b-5p levels play an important role in Sp1-mediated CD248 expression and the development of drug resistance in TLR-mutated colon cancer cells.
Vitamin C in combination with inhibition of mutant IDH1 synergistically activates TET enzymes and epigenetically modulates gene silencing in colon cancer cells
