TGF-beta pathway polymorphisms and colon cancer risk

我们先前已经鉴定了TGFBR 1 *6A，这是TGFBR 1基因的一种常见变体，并表明它传递TGF-α生长抑制信号的效率低于TGFBR 1。我们最近的荟萃分析显示，与非携带者相比，TGFBR 1 *6A携带者患结肠癌、乳腺癌和卵巢癌的风险显著增加。总的来说，杂合子中癌症风险增加了19%，纯合子中增加了70%，这是一种等位基因剂量效应的模式。我们还发现TGFBR 1 *6A可能与遗传性结直肠癌有关。超过八分之一的健康个体和六分之一的癌症患者是TGFBR 1 *6A携带者，这确立了TGFBR 1 *6A作为第一个高频低突变候选肿瘤易感等位基因。相反，在动物模型中，增加的TGF-α循环水平与降低的癌症风险相关。在人TGF-α 1（TGFB 1）基因内的第10个氨基酸位置变体处的常见亮氨酸至脯氨酸取代导致体外细胞外TGFB 1分泌更高。TGFB 1 *CC基因型携带者体内TGFB 1循环水平高于TGFB 1 *TT基因型携带者。TGFBR 1和TGFB 1变体可能对结直肠癌风险具有相反或协同作用。我们的中心假设是，两种功能相关的TGF-α途径信号传导变体的组合评估将比单独的每种变体更准确地预测结直肠癌风险。NCI发起的家族性结直肠癌登记是检验这一假设的理想资源。使用同胞配对病例对照设计，我们将对总共4，208个完全同胞病例对照对进行基因分型，首先：评估TGFBR 1 *6A与结直肠癌之间的关联。第二个：评估TGFB 1与结直肠癌之间的关联，并进行TGFB 1基因的单倍型分析;第三，分析TGFB 1和TGFB 1之间的基因-基因相互作用。这将探索两种功能性TGF-α途径多态性与结直肠癌风险之间的关系，并确定这两种变体预测的TGF-α信号传导是否与结直肠癌风险相关;第四：研究TGF-α途径多态性与肿瘤微卫星不稳定性之间的关系。

We have previously identified TGFBR1*6A, a common variant of the TGFBR1 gene, and shown that it transmits TGF-a growth inhibitory signals less effectively than TGFBR1. Our recent meta-analyses show that TGFBR1*6A carriers have a significantly increased risk of colon, breast and ovarian cancer as compared with non-carriers. Overall, cancer risk is increased by 19% among heterozygotes and 70% among homozygotes, a pattern indicative of an allelic dosing effect. We have also shown that TGFBR1*6A may contribute to hereditary colorectal cancer. More than one in eight healthy individuals and one in six patients with cancer is a TGFBR1*6A carrier, which establishes TGFBR1*6A as the first high-frequency low-penetrance candidate tumor susceptibility allele. In contrast, increased TGF-a circulating levels have been associated with a decreased cancer risk in animal models. A common Leucine to Proline substitution at the 10th amino acid position variant within the human TGF- a1 (TGFB1) gene results in higher in vitro extracellular TGFB1 secretion. Carriers of the TGFB1*CC genotype have higher in vivo TGFB1 circulating levels than carriers of the TGFB1*TT genotype. TGFBR1 and TGFB1 variants my have opposite or synergistic effects on colorectal cancer risk. Our central hypothesis is that a combined assessment of the two functionally-relevant TGF- a pathway signaling variants will predict colorectal cancer risk more accurately than each variant alone. The NCI-sponsored familial colorectal cancer registry is an ideal resource in which to test this hypothesis. Using a sibling-matched case-control design we will genotype a total of 4,208 full sibling case-control pairs and First: assess the association between TGFBR1*6A and colorectal cancer. Second: assess the association between TGFB1 and colorectal cancer and perform haplotype analysis of the TGFB1 gene; Third: analyze gene-gene interactions between TGFBR1 and TGFB1. This will explore the relationships between the two functional TGF-a pathway polymorphisms and colorectal risk and determine whether TGF- a signaling, as predicted by these two variants, is associated with colorectal cancer risk; and, Fourth: investigate the relationship between TGF-a pathway polymorphisms and tumor microsatellite instability.