Hedgehog Signaling Promotes Multidrug Resistance by Regulation of ABC Transporters in Oral Squamous Cell Carcinoma.

BACKGROUND Multidrug resistance (MDR) is one of the reasons for treatment failure in oral squamous cancer patients, however, the MDR mechanisms remain elusive. METHODS Two human oral squamous cell carcinoma (OSCC) cell lines, CAL27 and SCC9 were analyzed by stepwise selection upon exposure to 5-fluorouracil (5-FU) and cisplatin (CDDP) for MDR cell line establishment, and cell viability was analyzed by CCK8 assays. Transcriptomes of the CAL27 and CAL27-MDR cells were analyzed by RNA-seq assay. The molecules in SHH signal pathway and MDR related pathway were selected for validation by qRT-PCR and western blotting. Human OSCC tissues were applied for immunohistochemical and clinicopathological analysis. RESULTS The OSCC-MDR cell lines with resistance to 5-FU and CDDP were successfully established. Protein expression levels of ATP-binding cassette (ABC) transporter ABCC1 and ABCG2 were increased 1.6-fold and 2.1-flod respectively in OSCC specimen from the patients with chemotherapy. The RNA-seq assay speculated the activation of Hedgehog (Hh) signaling with the up-regulation of SHH, PTCH1, and SMO in OSCC-MDR cells as compared with OSCC cells. Furthermore, immunohistochemical studies confirmed that the high expression of SHH, PTCH1 and SMO in OSCC patients were significantly associated with chemotherapy. Overexpression of SHH increased the chemoresistance in OSCC cells, while the mRNA expression levels of PTCH1 and ABCG2 were increased in OSCC cells upon stimulation with recombinant SHH protein. CONCLUSIONS These results revealed that the activation of Hh signaling pathway regulating ABC transporters is associated MDR in OSCC.