Multi-omics profiling of upper-tract urothelial carcinomas.

Abstract

4560 Background: Upper-tract urothelial carcinomas (UTUC) may harbor similar genetic profile as compared to bladder cancer, although frequencies of mutated genes have been shown to differ between them. However, to the best of our knowledge, the epigenetic landscapes of UTUC and their association with genetic alterations and clinico-pathological tumor features remain unknown. Methods: We collected 40 UTUC samples (20 non-muscle invasive (NMI) and 20 muscle-invasive (MI) and carried out whole-exome sequencing (n = 30), DNA methylation using Infinium EPIC arrays (n = 35) and RNA sequencing (n = 20). Validation was performed on TCGA bladder cancer dataset. Results: We identified 3232 putative somatic mutations with an average of 2.1+/-2.6 mutations per megabase. Significantly mutated genes were FGFR3 (50%), KDM6A (27%), MLL2 (27%) and ARID1A/B (23%). No difference in term of genetic alterations were identified between MI- and NMI- UTUC. Unsupervised hierarchical clustering using most variable DNA methylation probes uncovered two robust DNA methylation epi-clusters. Epi-cluster C1 (n = 23; 65.7%) displayed markedly higher DNA methylation relative to Epi-cluster C2 (n = 12; 34.3%). Notably, all muscle-invasive samples were enriched in C1 (16/17, 94.1%); conversely, C2 was enriched with non-muscle-invasive samples (p = 0.0009). Overall, 14.209 probes were significantly hypermethylated in C1 as compared to C2 epi-cluster; Gene Set Enrichment Analysis (GSEA) demonstrated that those were enriched for PRC2 targets (p = 6x10-65). Integrative analysis with tumor genetic landscape showed that C1 epi-cluster was enriched for mutations in SWI/SNF complex as compared to C2 (p = 0.02). We then applied our epi-signature to bladder TCGA cohort and obtained two similar epi-clusters associated with patients overall survival (p = 0.035). Conclusions: Our study demonstrate for the first time that difference between MI- and NM- invasive UTUC might be related to epigenetic rather than genetic alterations. This might pave the way for testing epigenetic therapies in non-muscle invasive tumors with the aim to prevent recurrence and distant metastasis.