H3K4 methylation of CALB2 facilitates immune evasion and chemoradiotherapy resistance in cholangiocarcinoma through KRT7-mediated PD-L1 upregulation

This study elucidates how H3K4 methylation-driven upregulation of Calbindin 2 (CALB2) promotes immune evasion and chemoradioresistance in cholangiocarcinoma (CCA). Integrated bioinformatics analyses identified CALB2 as a hub gene linked to an immunosuppressive microenvironment. In vitro, CALB2 knockdown suppressed tumor cell proliferation, migration, invasion, and calcium signaling—evidenced by reduced phosphorylation of CaMKII, PKC, and NF-κB—while increasing apoptosis. Mechanistically, CALB2-activated NF-κB transcriptionally upregulated Keratin 7 (KRT7), which subsequently induced PD-L1 expression. This CALB2/KRT7/PD-L1 axis impaired T cell activation, reducing CD69 and IFN-γ expression. In vivo, CALB2 silencing inhibited tumor growth, downregulated PD-L1 and Ki-67, and enhanced apoptosis. Notably, CALB2 knockdown significantly sensitized CCA tumors to gemcitabine plus radiotherapy, an effect attenuated by KRT7 overexpression. These findings define a novel H3K4 methylation/CALB2/calcium/NF-κB/KRT7/PD-L1 signaling axis that drives immune suppression and therapy resistance in CCA, highlighting its potential as a multi-target strategy for combined immunotherapy and chemoradiotherapy.