Collagen VI sustains cell stemness and chemotherapy resistance in glioblastoma.

Microenvironmental factors are known fundamentals regulators of the phenotype and aggressiveness of glioblastoma (GBM), the most lethal brain tumor, characterized by fast progression and marked resistance to treatments. In this context, the extracellular matrix (ECM) is known to heavily influence the behavior of cancer cells from several origins, contributing to stem cell niches, influencing tumor invasiveness and response to chemotherapy, mediating survival signaling cascades, and modulating inflammatory cell recruitment. Here we show that collagen VI (COL6), an ECM protein widely expressed in both normal and pathological tissues, has a distinctive distribution within the GBM mass, strongly correlating with the most aggressive and phenotypically immature cells. Our data demonstrate that COL6 sustains the stem-like properties of GBM cells and supports the maintenance of an aggressive transcriptional program promoting cancer cell proliferation and survival. In particular, we identified a specific subset of COL6-transcriptionally regulated genes, required for the response of cells to replicative stress and DNA damage, supporting the concept that COL6 is an essential stimulus for the activation of GBM cell response and resistance to chemotherapy, through the ATM/ATR axis. Altogether, these findings indicate that COL6 plays a pivotal role in GBM tumor biology, exerting a pleiotropic action across different GBM hallmarks, including phenotypic identity and gene transcription, as well as response to treatments, thus providing valuable information for the understanding of the complex microenvironmental cues underlying GBM malignancy. Collagen VI is over-expressed in the cancer stem cell niche in glioblastoma and protects them from differentiation stimuli and chemotherapy exposure. Gene expression was measured using Affymetrix platform in primary GBM cells transfected with a Negative Control siRNA or two different siRNAs against COL6A1.