Integrating role of T antigen, Rb2/p130, CTCF and BORIS in mediating non-canonical endoplasmic reticulum-dependent death pathways triggered by ER-chronic stress in mouse medulloblastoma

Distinct molecular pathways could be constitutively active in mouse T antigen-positive and T antigen-negative medulloblastoma cell lines, contributing to their phenotypic differences as well as to cellular responses, cell cycle progression, cell death and survival. The diversity of these responses may be due, at least in part, to distinct activities of Rb2/p130, CTCF and BORIS proteins in response to an altered network of signaling evoked by the T-Ag presence. Here, we provided evidence supporting a role for the T antigen in causing chronic endoplasmic reticulum ( ER) stress and aberrant Caspase-12 expression and activation, subsequently driving to both massive cell death and, perhaps, selection of cells with a higher malignant phenotype. Furthermore, we observed that the endoplasmic stress, either chronically caused by T-Ag or transiently induced by glucose deprivation, is accompanied by the formation of complexes between the retinoblastoma-related protein Rb2/p130 and the chromatin insulator CCCTC binding factor CTCF or the CTCF paralog BORIS. Our study represents the first evidence supporting a role of T antigen in inducing/maintaining chronic ER stress as well as indicating a role of Rb2/p130, CTCF and BORIS as potential mediators of non-canonical ER-dependent death pathway in mouse medulloblastoma.