Abstract LB-051: Integrative, targeted deep sequencing of bladder tumors reveals novel associations between cancer gene mutations and mutational signatures with major risk factors
Authors: Koutros Stella , Rao Nina , Moore Lee E. , Nickerson Michael L. , Lee Donghyuk , Zhu Bin , Pardo Larissa , Baris Dalsu , Schwenn Molly , Johnson Alison , Jones Kristine , Garcia-Closas Montserrat , Prokunina-Olsson Ludmila , Silverman Debra T. , Rothman Nathaniel , Dean Michael 
Published: August 2019

Abstract
Exome and whole-genome sequencing of muscle-invasive (MI) bladder cancer has revealed important insights into the molecular landscape; however, there are few studies of non-muscle invasive (NMI) bladder cancer with detailed information on bladder cancer risk factors. We used deep, targeted amplicon sequencing of the coding regions of 44 genes frequently mutated in bladder cancer (average 630x coverage for tumor and 350x for germline DNA) to characterize somatic mutations and the mutational spectrum in 307 formalin fixed paraffin embedded bladder tumors (n=260 NMI and n=47 MI) from a population-based case-control study with detailed information on smoking and other risk factors. Variants identified by mutation calling pipelines were validated by manual review of aligned sequences. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) to evaluate somatic mutations and risk factors. We used SignatureEstimation to extract the four known single base substitution mutational signatures (COSMIC: Sig1, Sig2, Sig13, ERCC2-Signature) and Poisson regression to calculate risk ratios (RRs) and 95%CIs to evaluate signatures and risk factors. The most frequently mutated gene in NMI tumors was FGFR3 (52% mutated) and in MI tumors was TP53 (51% mutated). FGFR3 (89%), STAG2 (81%), and PIK3CA (78%) mutations were significantly higher in Ta tumors compared to T1 or MI tumors. Mutations in histone/chromatin regulating genes (KDM6A, KMT2D, KMT2C, CREBBP, ARID1A, and EP300) were present at a high frequency in low grade Ta tumors. Non-silent KDM6Amutations were significantly more common in females compared to males (OR=1.79,95%CI:1.03-3.11); in females these mutations largely occurred in Ta tumors (86%). There was striking heterogeneity in the relationship between smoking status (current, former, never) and the established signatures: only current smoking was associated with greater ERCC2-Signature variants compared to both former smoking (p-value=0.015) and never smoking (p-value=0.023); only former smoking was associated with APOBEC-Sig13 variants (RR=1.83,95%CI: 1.10-3.04,p-value=0.019); and only never smoking was associated with the APOBEC-Sig2 variants (RR=1.52,95%CI: 1.15-2.01,p-value=0.003). Further, there was significant evidence that smoking duration, the component of smoking most strongly associated with bladder cancer risk, was associated with ERCC2-Signature variants and APOBEC-Sig13 variants among current (p-trend=0.013) and former smokers (p=0.002), respectively. Exploration of insertion/deletions revealed that both status and duration of smoking was significantly associated with presence of any 1bp deletions (p-trend=0.007); these were enriched for deletions in KDM6A (p=0.0003). In conclusion, these data quantify the contribution of bladder cancer risk factors to mutational burden in a population-based series of tumors and reveal distinct signature contributions among never, former and current smokers.
Citation Format: Stella Koutros, Nina Rao, Lee E. Moore, Michael L. Nickerson, Donghyuk Lee, Bin Zhu, Larissa Pardo, Dalsu Baris, Molly Schwenn, Alison Johnson, Kristine Jones, Montserrat Garcia-Closas, Ludmila Prokunina-Olsson, Debra T. Silverman, Nathaniel Rothman, Michael Dean. Integrative, targeted deep sequencing of bladder tumors reveals novel associations between cancer gene mutations and mutational signatures with major risk factors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-051.