STAT3 expression, activity and functional consequences of STAT3 inhibition in esophageal squamous cell carcinomas and Barretts adenocarcinomas

Signal transducer and activator of transcription 3 (STAT3) is altered in several epithelial cancers and represents a potential therapeutic target. Here, STAT3 expression, activity and cellular functions were examined in two main histotypes of esophageal carcinomas. In situ, immunohistochemistry for STAT3 and STAT3-Tyr705 phosphorylation (P-STAT3) in esophageal squamous cell carcinomas (ESCC) and Barretts adenocarcinomas (BAC) revealed similar STAT3 expression in ESCCs and BACs, but preferentially activated P-STAT3 in ESCCs. In vitro, strong STAT3 activation was seen by EGF-stimulation in OE21 (ESCC) cells, whilst OE33 (BAC) cells showed constitutive weak STAT3 activation. STAT3 knockdown significantly reduced cell proliferation of OE21 and OE33 cells and reduced cell migration in OE33, but not in OE21 cells. Transcriptome analysis identified STAT3-knockdown associated down-regulation of cell cycle processes and the selective down-regulation of cyclins and cyclin dependent kinaes associated genes in both OE21 and OE33 cells. Moreover, the transcriptome response showed changes in cell migration/invasion related genes that correlated with the associated phenotype measurements. This study demonstrates the importance of STAT3 expression and activation in esophageal carcinomas, whereby the extent differs between ESCCs and BACs. STAT3 knockdown significantly reduces cell proliferation in both types of esophageal cancer cells and inhibits migration in BAC cells. Thus, STAT3 may be further exploited as potential novel therapeutic target for esophageal cancers.

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Timme S, Ihde S, Fichter CD, Waehle V, Bogatyreva L, Atanasov K, Kohler I, Schöpflin A, Geddert H, Faller G, Klimstra D, Tang L, Reinheckel T, Hauschke D, Busch H, Boerries M, Werner M, Lassmann S