BioProject

The aim of this study was to investigate the effect of VEGF targeted therapy (sunitinib) on intratumoral heterogeneity (ITH) in metastatic clear cell renal cancer (mRCC). To explore ITH in detail, multiple tumor samples were taken from the primary renal tumors of mRCC patients who were sunitinib treated (n=23) or untreated (n=23). ITH of pathological grade, DNA (using array-based comparative genomic hybridisation), RNA (Illumina Beadarray) and protein (reverse phase protein array) were evaluated. Tumor grade heterogeneity was greater in treated compared to untreated tumors (P=0.002). Unsupervised and supervised analysis, for renal cancer driver, hypoxia and stromal gene signatures, was then performed. In untreated patient tumor samples, significant ITH occurred in chromosomal aberrations, RNA and protein expression, with clustering of DNA and RNA correlating for individual patients. In unsupervised analysis sunitinib therapy was not associated with increased ITH in DNA or RNA. However there was an increase in ITH for the driver mutation and hypoxia gene signatures (DNA and RNA) as well as increasing variability of protein expression with treatment (p<0.05). Despite this variability, significant chromosomal and RNA changes to targets of sunitinib, such as VHL, PBRM1 and CAIX, occurred in the treated samples. Together these findings suggest that sunitinib treatment has significant effects on the expression and ITH of key tumor and treatment specific genes. The results do not support the hypothesis that resistant clones are selected and predominate after initiation of targeted therapy; instead it appears that an initial clonal diversification occurs, supporting the hypothesis of polyclonal drug resistance. Overall design: 128 samples from patients with clear cell renal cell carcinoma, including biological replicates of nephrectomy samples. Source of samples includes both biopsy and nephrectomy. DNA extracted from FFPE and fresh frozen tissue samples.