HIF-pathway genes prognostic for progression-free and overall survival in metastatic clear cell renal cell carcinoma (mccRCC).

Abstract

370 Background: Clear cell renal cell carcinoma (ccRCC) is characterized by defects in the Von Hippel-Lindau/hypoxia-inducible factor (VHL/HIF) pathway. Several FDA-approved RCC therapies target the products of HIF-response genes. HIF2A is a promising new target and drugs targeting HIF2A are undergoing clinical testing. A better understanding of HIF-related genes may reveal useful biomarkers and drug targets. Methods: Gene expression was determined from 324 archival pretreatment nephrectomy specimens available from the Cancer and Leukemia Group B (CALGB) 90206, a phase III trial of patients treated with INF-α vs. INF-α plus bevacizumab. TaqMan RT-qPCR was performed on the OpenArray platform using RNA extracted from tumor tissue macrodissected based on review of H&E staining by a genitourinary pathologist. HIF pathway genes were assessed across both treatment arms, utilizing the proportional hazards model as predictors of OS and PFS, with time from randomization to death or disease progression as endpoints. Results: A total of 28 HIF-related genes (involved either in canonical or non-canonical HIF regulation) were assessed in univariate PH. Nine of these genes were associated with OS (i.e., HIF2A , VEGFC, VEGFD, TGFA, VHL, CCND1, EGFR, EGLN3 and HSP90AA1); and 6 of them were also associated with PFS (i.e., HIF2A , TGFA, VHL, CCND1 and EGLN3, and HSP90AA1). The HIF isotypes HIF1A and HIF3A were not prognostic, likewise VEGFA and VEGFB. Prolyl hydroxylase domain (PHD) proteins efficiently hydroxylate HIFα in normoxic conditions. PHD isotypes EGLN (1-3) were evaluated and only EGLN3 was associated with OS and PFS. HIF is also regulated by non-canonical pathways that function independent of oxygen concentration. HSP90AA1 was the only non-canonical pathway gene that was prognostic, and it predicted both OS and PFS. When the 9 genes that were prognostic in univariate analysis were used in a backward stepwise multivariate cox regression, VEGFD, TGFA and EGLN3 predicted OS while HIF2A, VHL and TGFA predicted PFS. Conclusions: VHL, HIF2A (but not HIF1A and HIF3A), EGLN3 (but not EGLN1 and EGLN2) and some of the HIF-response genes were prognostic of both OS and PFS. HSP90AA1 was prognostic for OS and PFS, suggesting that the non-canonical HIF pathway also plays a role in disease progression. Future studies should consider these HIF pathway genes as potential drug targets, and as predictors of response to treatments targeting the hypoxia pathway and angiogenesis.[Table: see text]