XBP1 and ovarian cancer: To validate our findings in an independent patient cohort, we retrieved normalized expression data on DDIT3, HSPA5 and HSP90B1, as well as on transcripts encoding the ER stress-relevant proteins activating transcription factor 6 (ATF6) and X-box binding protein 1 (XBP1) for 302 patients with primary ovarian cancer from the TCGA database, and analyzed their correlation with CALR abundance.