Supplementary Material for: Association Between Hypoxia-Inducible Factor-2α (HIF-2α) Expression and Colorectal Cancer and Its Prognostic Role: a Systematic Analysis

Background/Aims: Although some studies showed that HIF-2α expression was correlated with an unfavorable prognosis in colorectal cancer (CRC), the prognostic results remain conflicting in CRC. The present study was performed to evaluate the association between HIF-2α expression and the clinicopathological features of this disease and to examine the potential prognostic role of HIF-2α expression in CRC. Methods: Pooled odds ratios (ORs) or hazard ratios (HRs) were calculated from available publications, The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) datasets. Trial sequential analysis (TSA) was used to estimate the required sample information. Results: HIF-2α protein expression was more frequent in CRC than in normal colonic tissues (OR = 150.49, P < 0.001), higher in male than female CRC patients (OR = 1.47, P = 0.008), and lower in high-grade than low-grade CRC (OR = 0.49, P = 0.029). TSA verified the reliability of the above results. HIF-2α expression was not linked to the prognosis of CRC in overall survival (OS), disease-specific survival (DSS), metastasis-free survival, and relapse-free survival, and no significant correlation was found between HIF-2α alteration and OS or disease-free survival (DFS) of CRC. Expression of both HIF-2α and vascular endothelial growth factor (VEGFA, VEGFB, or VEGFC) was associated with a poor metastasis-free survival of CRC (HR = 6.95, HR = 113.51, and HR = 8.11, respectively). No association was observed between HIF-2α expression and DFS in other cancers, but HIF-2α expression was correlated with a worse DFS of CRC (HR = 1.23, P = 0.037). Moreover, HIF-2α expression was linked to a good survival benefit in some cancers (B-cell lymphoma and lung adenocarcinoma: OS, multiple myeloma: DSS, breast cancer: distant metastasis-free survival, liposarcoma: distant recurrence-free survival) (all HRs < 1, Ps < 0.05). Conclusions: HIF-2α expression may be associated with the carcinogenesis of CRC, which is higher in males than in females, negatively linked to tumor differentiation, and correlated with a worse DFS of CRC. Additional prospective studies are needed.

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