RESUMO
Tumour hypoxia status provides prognostic information and predicts response to hypoxiamodifying treatments. A previous study by our group derived a 24gene signature to assess hypoxia in bladder cancer. The objectives of the present study were to compare platforms for generating signature scores, identify cutoff values for prospective studies, assess intratumour heterogeneity and confirm hypoxia relevance. Briefly, RNA was extracted from prospectively collected diagnostic biopsies of muscle invasive bladder cancer (51 patients), and gene expression was measured using customised Taqman Low Density Array (TLDA) cards, NanoString and Clariom S arrays. Crossplatform transferability of the gene signature was assessed using regression and concordance analysis. The cutoff values were the cohort median expression values. Intra and intertumour variability were determined in a retrospective patient cohort (n=51) with multiple blocks (218) from the same tumour. To demonstrate relevance, bladder cancer cell lines were exposed to hypoxia (0.1% oxygen, 24 h), and extracted RNA was run on custom TLDA cards. Hypoxia scores (HS) values showed good agreement between platforms: Clariom S vs. TLDA (r=0.72, P<0.0001; concordance 73%); Clariom S vs. NanoString (r=0.84, P<0.0001; 78%); TLDA vs. NanoString (r=0.80, P<0.0001; 78%). Cutoff values were 0.047 (TLDA), 7.328 (NanoString) and 6.667 (Clariom S). Intratumour heterogeneity in gene expression and HS (coefficient of variation 3.9%) was less than intertumour (7.9%) variability. HS values were higher in bladder cancer cells exposed to hypoxia compared with normoxia (P<0.02). In conclusion, the present study revealed that application of the 24gene bladder cancer hypoxia signature was platform agnostic, cutoff values determined prospectively can be used in a clinical trial, intratumour heterogeneity was low and the signature was sensitive to changes in oxygen levels in vitro.