Genetic and Pharmacogenetic Modifiers of Cancer Risk and Intervention Outcomes

Division Of Cancer Epidemiology And Genetics

Investigators

Linked publications & trials

Abstract

The first of these studies - Genetic Modifiers of Tamoxifen-Related Breast Cancer Risk: NSABP P1G3 [CAS 7220]- was a case/case analysis of 39 SNPs in 19 different genes among 249 women with invasive breast cancer (84 exposed to tamoxifen;165 placebo). This was a null study by single SNP association and haplotype analysis. However, the constellation of alleles characterizing cases emerging in the presence of tamoxifen (resistant genotypes) was distinct from that in the unexposed (placebo) cases. This pathway analysis approach generated an allelic signature that may have potential as a predictive biomarker of tamoxifen resistance. These results have just been published..Utilizing the resources of the Prostate, Lung, Colon and Ovarian (PLCO) Cancer screening trial, we have been investigating the relationship between the Insulin-Like Growth Factor (IGF) Signaling Pathway and Risk of Advanced Colorectal Adenoma [CAS 7300], prompted by data suggesting that IGFs may represent potentially modifiable cancer risk factors. We have analyzed 800 participants found to have an advanced colorectal adenoma at the time of baseline screen, and 800 matched non-adenoma subjects. Genotyping has been completed on 37 SNPs in 7 IGF-related genes (IGF1, IGF-BP3, ALS, IGF-1R, IGF-BP5, IGF2 and GH), and circulating levels of IGF-1, IGF-2 and IGFBP-3 have been measured. The latter documented a 1.7-fold increase in adenoma risk (95% C.I. 1.2-2.5) in highest vs. lowest quartiles of IGF-1, controlled for IGF-2, IGF-BP3 and numerous other covariates. The evaluation of genetic variants as primary risk factors for advance adenoma was null, although we confirmed the previously-observed strong relationship between IGF-BP3-01 (rs2854744), and a new association between IGF-BP3-07 (rs6413441) and circulating levels of IGF-BP3 among controls. These two SNPs decrease IGF-BP-3 levels by 222 and 148 units per minor allele (mean IGF-BP3 level 4,000 units). This study has been expanded by adding additional genotyping data from the DCEG Rare Cancers iSELECT study which, serendipitously, analyzed the same set of DNA samples. These data provide a more comprehensive interrogation of IGF signaling pathway genes: 1,338 advanced colorectal adenoma cases and 1,503 matched controls were studied, and data generated for 570 single nucleotide polymorphisms (SNPs) in 28 IGF pathway genes. Two SNP associations remained statistically significant after a gene-based correction for multiple testing. The G allele of rs12305513, which is located in an intron of the oncogene, KRAS, was associated an increased risk of adenoma (ORper allele=1.36, 95% CI =1.13-1.63, P=0.001). The G allele of rs180531, located in the serine/threonine kinase gene, RPS6KB1, was associated with a reduced risk of adenoma (ORper allele=0.83, 95% CI=0.73-0.95, P=0.006). We have developed a portfolio of projects evaluating Genetic Risk Factors for Osteogenic Sarcoma [CAS10375]. Osteogenic sarcoma (OS), the most common malignant primary bone tumor, occurs most commonly during the adolescent growth spurt. As part of a prospective case-control study of OS initiated in 1995 with the NCI and Harvard Dental School, we studied genetic variation in many genes/pathways implicated in the cellular regulation of growth. We identified a small haplotype block that was associated with risk of OS in the IGF2R gene. This genomic region (near exon 16) consists of CpG islands, and functional analysis of the SNPs in this block suggested that a specific SNP associated with OS risk resulted in differential methylation at that SNP site. Because OS is one of the syndrome-defining malignancies in patients with germ-line TP53 mutations (i.e., the Li-Fraumeni Syndrome), we investigated the role of germ-line genetic variants in TP53 as OS risk factors. These data did not indicate a strong link between variation in TP53 and OS risk, although they did provide preliminary evidence of an increased risk of OS associated with TP53 variants IVS2+38 and Pro72Arg. We recently updated the descriptive epidemiology of OS in two separate publications: one based on US data from NCIs SEER program, and the other based on multiple international cancer epidemiology databases. A meta-analysis is currently under review;it was aimed at clarifying height and birth weight as OS risk factors. The data confirm that height is a significant risk factor for OS. The evidence related to birth weight was not definitive. Finally, we have launched an international collaborative project which will support a genome-wide association study (GWAS) aimed at identifying genetic risk factors for OS. Collaborators include the Childrens Oncology Group, and multiple investigators in Europe and Australia. The GWAS will consist of approximately 2000 OS cases;controls will be derived from existing NCI studies.