Abstract 814: Gene-based analysis of the IGF signaling pathway and risk of breast cancer in African American women: The AMBER consortium
Authors: Ruiz-Narvaez Edward A. , Lunetta Kathryn L. , Hong Chi-Chen , Haddad Stephen A. , Yao Song , Cheng Ting-Yuan D. , Bensen Jeannette T. , Bandera Elisa V. , Haiman Christopher A. , Olshan Andrew F. , Ambrosone Christine B. , Rosenberg Lynn , Palmer Julie R. 
Published: July 2016

Abstract
Dysregulation of the IGF (insulin-like growth factor) signaling pathway plays a key role in cancer development. It is still unclear whether germline variation in genes in the IGF pathway may affect risk of breast cancer. We conducted a gene-based analysis of 184 genes in the IGF signaling pathway to identify genes carrying genetic variation affecting risk of breast cancer and the specific estrogen receptor (ER) subtypes. Tagging single nucleotide polymorphisms (SNPs) for each gene were selected and genotyped on a customized Illumina Exome Array. Imputation was carried out using 1000 Genomes haplotypes. The analysis included 91,627 SNPs in 3,663 breast cancer cases (including 1,983 ER positive,1,098 ER-negative) and 4,687 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium, a collaborative project of four large studies of breast cancer in African American women (Carolina Breast Cancer Study, Black Women's Health Study, Women's Circle of Health Study, and Multiethnic Cohort). We used a multi-locus adaptive joint (AdaJoint) test to determine the association of each gene in the IGF signaling pathway with overall breast cancer and ER subtypes. None of the 184 tested genes, including IGF, IGF binding protein (IGFBP), and IGF receptor (IGFR) genes were associated with disease after adjustment for multiple testing. At the nominal level of P≤0.01, BAIAP2 (P = 0.003), and CALM2 (P = 0.009) genes were associated with overall breast cancer; BAIAP2 (P = 0.001), and CSNK2A1 (P = 0.01) with ER+ breast cancer; and BRAF (P = 0.003), BAD (P = 0.005), and MAPK3 (P = 0.009) with ER- breast cancer. The intronic rs9913477 SNP in the BAIPA2 gene was significantly associated with overall (P = 3.2×10−7) and ER+ (P = 4.4×10−7) breast cancer at the pathway-wide level after adjusting for the total number of tested SNPs. Odds ratios and 95% confidence intervals of the risk G-allele were 1.44 (1.25, 1.66), and 1.53 (1.30, 1.81) for overall and ER+ breast cancer, respectively. BAIAP2 codes an adaptor protein, IRSp53, which functions as a substrate of the insulin receptor and IGF-1 receptor tyrosine kinases and links Rho-family small GTPases such as Rac. In vitro studies have shown that activation of Rac promotes metastatic behavior of breast cancer cells. In conclusion, we identified a SNP in BAIAP2 associated with overall and ER+ breast cancer.
These results highlight the importance of the IGF signaling pathway in the pathogenesis of breast cancer.
Citation Format: Edward A. Ruiz-Narvaez, Kathryn L. Lunetta, Chi-Chen Hong, Stephen A. Haddad, Song Yao, Ting-Yuan D. Cheng, Jeannette T. Bensen, Elisa V. Bandera, Christopher A. Haiman, Andrew F. Olshan, Christine B. Ambrosone, Lynn Rosenberg, Julie R. Palmer. Gene-based analysis of the IGF signaling pathway and risk of breast cancer in African American women: The AMBER consortium. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 814.