Sun, Haiming

Abstract Background: Lung cancer kills more people than any other cancer in the United States. In addition to environmental factors, lung cancer has genetic risk factors as well, though the genetic etiology is still not well understood. We have performed whole exome sequencing on 262 individuals from 28 extended families with a family history of lung cancer. Methods: Parametric genetic linkage analysis was performed on these samples using two distinct analyses—the lung cancer only (LCO) analysis, where only patients with lung cancer were coded as affected, and the all aggregated cancers (AAC) analysis, where other cancers seen in the pedigree were coded as affected. Results: The AAC analysis yielded a genome-wide significant result at rs61943670 in POLR3B at 12q23.3. POLR3B has been implicated somatically in lung cancer, but this germline finding is novel and is a significant expression quantitative trait locus in lung tissue. Interesting genome-wide suggestive haplotypes were also found within individual families, particularly near SSPO at 7p36.1 in one family and a large linked haplotype spanning 4q21.3-28.3 in a different family. The 4q haplotype contains potential causal rare variants in DSPP at 4q22.1 and PTPN13 at 4q21.3. Conclusions: Regions on 12q, 7p, and 4q are linked to increased cancer risk in highly aggregated lung cancer families, 12q across families and 7p and 4q within a single family. POLR3B, SSPO, DSPP, and PTPN13 are currently the best candidate genes. Impact: Functional work on these genes is planned for future studies and if confirmed would lead to potential biomarkers for risk in cancer.

Abstract Lung cancer is the deadliest cancer in the United States, contributing approximately 25% of all cancer deaths. Lung cancer risk is well-documented to increase in response to environmental factors, particularly tobacco smoking. As one might expect for a complex trait, there is also a significant genetic risk component in lung cancer, though it is not very well studied. We obtained whole exome sequencing (WES) genotype data from Washington University on 204 subjects from 25 extended families. These individuals were recruited from families with a history of lung cancer and previous analyses showed these 25 families be informative. The purpose of this study is to identify potential risk variants for lung cancer by performing genetic linkage analysis. Quality control was performed on the sequence data, filtering on parameters such as depth (less than 10), genotype quality (less than 10), missingness, and Mendelian inconsistencies. Identity-by-descent (IBD) values were also calculated to verify correct familial relationships. Quality control procedures left approximately 500,000 SNVs and indels for analysis. We performed two-point parametric linkage analysis assuming an autosomal dominant mode of inheritance with a disease allele frequency of 1%, a 10% penetrance for carriers and a 1% penetrance for non-carriers. Two discrete sets of linkage analyses were performed. One was a variant-based analysis, which evaluated linkage between the phenotype and individual SNVs or indels. The second was gene-based analysis, which created a multi-allelic pseudomarker corresponding to a gene from haplotypes of rare variants (minor allele frequency <= 0.01) located within that particular gene. Two-point linkage analysis was then performed on the pseudomarkers. While the variant-based analysis did not identify any genome-wide significant results, several were identified by the gene-based analysis. The highest HLOD scores were both greater than the genome-wide significance level of HLOD = 3.3 and were located on two regions of chromosome 1q: 1q42.13-43 and 1q21.2-21.1. In both regions, the significant HLOD scores clustered around known cancer genes. At the 1q42.13-43 region, signals centered on the cancer-implicated genes OBSCN and RYR2 (also a known mesothelioma gene), while at 1q21.2-21.1 the signals centered on five genes in the neuroblastoma breakpoint family (NBPF) genes, a cluster of recently duplicated genes. NBPF genes have previously been implicated in a variety of different cancers including lung cancer. We are currently performing additional analyses to corroborate the significant results, as well as examining the individual families to determine which families are driving the significant signals. Citation Format: Anthony M. Musolf, Haiming Sun, Bilal A. Moiz, Diptasri Mandal, Mariza de Andrade, Colette Gaba, Ping Yang, Yafang Li, Ming You, Elena Y. Kupert, Marshall W. Anderson, Ann G. Schwartz, Susan M. Pinney, Christopher I. Amos, Joan E. Bailey-Wilson. Whole exome sequencing identifies significantly linked regions on multiple chromosomes in families with a history of lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3276.