Molecular Genetic Epidemiology of Primary Hepatocellular

大多数癌症表现为复杂的表型，并通过基因-基因和/或基因-环境相互作用表现出来。研究人类复杂癌症表型的理想范例是原发性肝细胞癌（HCC）。肿瘤遗传改变的分子研究已经确定p53是HCC中常见的肿瘤抑制基因。流行病学研究已经确定慢性乙型肝炎病毒感染（HBV）和黄曲霉毒素B1 （AFB1）暴露作为环境危险因素的作用。然而，大多数暴露于HBV和AFB1的个体不会发展为HCC。

The majority of cancer presents as a complex phenotype and is manifest through gene-gene, and/or gene-environment interactions. An ideal paradigm for the investigation of complex cancer phenotypes in humans is primary hepatocellular carcinoma (HCC). Molecular studies of genetic alterations in tumors have identified p53 as a tumor suppressor gene commonly altered in HCC. Epidemiologic studies have firmly established the role of chronic hepatitis B virus infection (HBV) and aflatoxin B1 (AFB1) exposure as environmental risk factors. However, the majority of individuals exposed to HBV and AFB1 do not develop HCC. Genetic analysis is being used to assess the role of genes in well-described pathways in determining disease. This approach merges gene mapping and candidate locus studies by including as candidates all the members of a pathway. Each gene of interest is "tagged" with multiple polymorphic sites, in or near it, to identify genetic factors modulating the risk of developing HCC among populations exposed to AFB1. The individual members of each family (GSTA1, GSTM1, GSTM3, GSTP, GSTT1, GST12, EPHX1, EPHX2, GSTA4, GSTT2, GSTZ1, STP, COMT, ESD, DTD, CYP, MGST1) have been tagged with new or published polymorphisms, and their role in HCC risk examined, in a nested case-control population. The loci GSTM1, GSTP, GSTT1, EPHX1 showed significant association with HCC risk while the EPHX2 locus was associated with age of onset. When results were stratified by the HBV status of the case, GSTM1 and GSTT1 were associated only in the HBV(+) cases, while GSTP was associated in the HBV(-) cases. These results indicate that these genes are candidates for more detailed functional and genetic analysis. Genetic information important in complex trait analysis may be accessible from the joint study of heritable variation and somatic tissue (tumor) variation in cancer. HCC tumor/normal pairs were examined using a collection of genome-wide simple tandem repeat polymorphism markers, and candidate loci. More recently the search for genetic modulators has been expanded to include the 1,300 SNPs available on the Affymetrix HuSNP chip. This data will be used to identify regions of loss of heterozygosity (LOH). In addition the information will be correlated with gene expression data, collected for the same samples using the Affymetrix HG-U95A chip containing 12,000 known or characterized genes. To assess the expression of tumor suppressor and mitotic checkpoint genes that might be altered in the regions showing LOH, rtPCR assays have been developed. The pattern of expression and presence of aberrant products is currently being analyzed by hierarchical clustering and self-organizing maps.