Tracking The Genetic Relationship Between First And Late-Onset Second Urothelial Cancers By Mutational Signature Analysis

Exposure to aristolochic acid (AA, IARC Group 1 carcinogen) present in some traditional herbal medicines leads to aristolochic acid nephropathy (AAN), often complicated by development of multiple urothelial carcinomas of sequential onset. We used genome-scale mutational signature analysis of multiple urinary tract tumors of AAN cases from a unique patient group to determine the relationships of the patients’ late-onset second cancers to the AA exposure as well as to the first cancers. Aristolactam-DNA adduct-positive AAN patients (n=4) who developed cancer within 8 years following the initial exposure to AA were chosen for analysis of their first cancers (upper tract urothelial carcinomas, UTUC) and second cancers of delayed onset (1-9 years after first-cancer diagnosis, involving the bladder or ureteral meatus). All patients had received a kidney transplant before developing the second cancers and had a functional renal graft prior to prophylactic nephroureterectomy. Genomic DNAs were isolated from FFPE sections of the renal cortex and from the upper and lower tract tumors of each patient using laser capture micro-dissection or macro-dissection of the tumor areas. Low-coverage (~15x) exome 100-bp paired-end sequencing was performed using Illumina HiSeq2500. Customized variant calling identified somatic variants absent in non-tumor tissues. Non-negative matrix factorization was applied to extract mutational signatures in the tumor tissues. In all cases, we established the mutational signature of AA (the COSMIC signature 22) in the first UTUC as well as second cancers involving the bladder or lower ureter (meatus). Additionally, the first and second cancers harbored considerable overlaps in exposure-specific (A>T) somatic mutations. This finding provides evidence that the delayed onset of bladder urothelial carcinomas in AAN patients is likely due to distal seeding of cancer cells originating from the primary UTUC tumors. Our first-of-its-kind study addresses the risk as well as mechanistic factors leading to the second, late-onset bladder urothelial carcinomas following kidney transplantation and primary UTUC development. Our results underline the importance of long-term bladder follow-up in high-risk populations with established or suspected AA exposure. Funding: IARC; NYU Genome Technology Center is partially supported by the NIH/NCI (P30CA016087) grant. Citation Format: Xavier Castells, Maude Ardin, Sandrine Rorive, Nilufer Broeders, Yan Song, Stephanie Villar, Christine Carreira, Pierre-Paul Bringuier, Adriana Heguy, Thierry Quackels, Thierry Roumeguere, Joelle Nortier, Jiri Zavadil. Tracking the genetic relationship between first and late-onset second urothelial cancers by mutational signature analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5738. doi:10.1158/1538-7445.AM2017-5738