COL6A1 and glioblastoma: Conversely, the expression of COL6A1 and its highly positively correlated genes (r ≥ 0.4; n = 12) increased progressively with tumor grade/malignancy (Fig. 5B), suggesting once again that COL6, possibly through a coordinated action with a series of strictly correlated genes, may have a critical role in sustaining GBM severity.