Abstract
The signal transducer and activator of transcription 3 (STAT3) oncogene is a transcription factor with a central role in head and neck cancer. Hypopharyngeal cells (HCs) exposed to acidic bile present aberrant activation of STAT3, possibly contributing to its oncogenic effect. We hypothesized that STAT3 contributes substantially to the bile reflux-induced molecular oncogenic profile, which can be suppressed by STAT3 silencing or pharmacological inhibition. To explore our hypothesis, we targeted the STAT3 pathway, by knocking down STAT3 (STAT3 siRNA), and inhibiting STAT3 phosphorylation (Nifuroxazide) or dimerization (SI3-201; STA-21), in acidic bile (pH 4.0)-exposed human HCs. Immunofluorescence, luciferase assay, Western blot, enzyme-linked immunosorbent assay and qPCR analyses revealed that STAT3 knockdown or pharmacologic inhibition significantly suppressed acidic bile-induced STAT3 activation and its transcriptional activity, Bcl-2 overexpression, transcriptional activation of IL6, TNF-α, BCL2, EGFR, STAT3, RELA(p65), REL and WNT5A, and cell survival. Our novel findings document the important role of STAT3 in bile reflux-related molecular oncogenic events, which can be dramatically prevented by STAT3 silencing. STA-21, SI3-201 or Nifuroxazide effectively inhibited STAT3 and cancer-related inflammatory phenotype, encouraging their single or combined application in preventive or therapeutic strategies of bile reflux-related hypopharyngeal carcinogenesis.