Integrative analysis of sarcomatoid clear-cell renal cell carcinomas reveals an immune subgroup.

Abstract

4571 Background: Integrative analysis of clear-cell renal cell carcinomas (ccRCC) has revealed four transcriptomic subgroups associated with distinct patients outcomes. Integrative analysis of sarcomatoid ccRCC which represent the most agressive forms of ccRCC remains unknown. Methods: We performed integrative analysis of sarcomatoid (n = 28) and Fuhrman grade IV ccRCC (n = 9) using whole-exome sequencing (n = 37), RNA-sequencing (n = 32), and DNA methylation profiling by Infinium 450K arrays (n = 31). Correlation with clinico-pathlogical tumor features and patients outcomes were performed. Results: The most frequent somatic mutations in sarcomatoid ccRCC were VHL (71%), PBRM1 (50%), SETD2 (21%), BAP1 (11%), and TP53 (11%). Hierarchical unsupervised clustering of gene expression revealed two transcriptomic subgroups C1 and C2 which do not differ in term of clinical features, presence of sarcomatoid dedifferentiation and patients outcomes. Furthermore, these clusters do not differ according to their genomic features ( VHL, PBRM1 and SETD2 mutations) or their mutational loads. Strikingly, C1 cluster was highly enriched for genes related to T cell receptor signaling pathway (p = 2.6x10-6) and adapative immunity (p = 8.5x10-5); in addition, the C1 « immune » subgroup was characterized by up-regulation of genes related to cell cycle. Conversely, C2 cluster revealed down-regulation of metabolic pathways (p = 7. 5x10-5). At the epigenetic level, methylome clustering revealed two distinct epi-clusters, epi-C1 (n = 10) and epi-C2 (n = 21); patients with tumors belonging to C2 epi-cluster displayed 9p loss and harbored inferior progression-free survival as compared to those in C1 epi-cluster (11 months versus NR ; P = 0.02); of note, this was independent of clinico-pathological tumor features and transcriptomic classification. Conclusions: Our data suggest that genetic and epigenetic landscapes of sarcomatoid ccRCC might not differ from grade IV ccRCC. In addition, we discovered an immune sarcomatoid ccRCC cluster. This finding provides a rationale for use of immune checkpoint inhibitors in sarcomatoid ccRCC.