Phosphohistidine signaling promotes FAK-RB1 interaction and growth factor-independent proliferation of esophageal squamous cell carcinoma

Abstract Current clinical therapies targeting receptor tyrosine kinases including focal adhesion kinase (FAK) have had limited or no effect on esophageal squamous cell carcinoma (ESCC). Unlike esophageal adenocarcinomas, ESCC acquire glucose in excess of their anabolic need. We recently reported that glucose-induced growth factor-independent proliferation requires the phosphorylation of FAKHis58. Here, we confirm His58 phosphorylation in FAK immunoprecipitates of glucose-stimulated, serum-starved ESCC cells using antibodies specific for 3-phosphohistidine and mass spectrometry. We also confirm a role for the histidine kinase, NME1, in glucose-induced FAKpoHis58 and ESCC cell proliferation, correlating with increased levels of NME1 in ESCC tumors versus normal esophageal tissues. Unbiased screening identified glucose-induced RB1 binding to FAK, mediated through a “LxCxE” RB1-binding motif in FAK’s FERM domain. Importantly, in the absence of growth factors, glucose increased FAK scaffolding of RB1 in the cytoplasm, correlating with increased ESCC G1àS phase transition. Our data strongly suggest that this glucose-mediated mitogenic pathway represents a unique targetable opportunity in ESCC.