MOLECULAR PATHOGENESIS OF CANCER OF MUTATOR PHENOTYPE

具有微卫星突变体表型（MMP）的胃肠道癌在基因型和表型上与不具有MMP的肿瘤不同。APC、p53和K-ras癌基因通常在MMP-肿瘤中突变，而TGF β RII和BAX的突变失活基本上限于MMP+癌。我们提出，MMP通路的存在和独特的功能，肿瘤的遗传性非息肉病性结直肠癌（HNPCC）综合征和约15%的散发性胃肠道癌的特征，最终取决于在一些癌症基因的序列的MMP目标的存在。在具体目标1中，我们将测试癌症存在MMP依赖性途径的假设。我们建议研究有或没有MMP的肿瘤之间的基因型差异。我们将完成MMP+和MMP-结肠肿瘤中APC抑制基因突变的筛选（1a）;确定MMP+和MMP-胃肠道肿瘤之间基因型的差异是否也延伸到我们在结肠癌、乳腺癌和前列腺癌中观察到的DNA甲基化的广泛体细胞变化，特别是在同源异型盒基因家族中（1b）;并利用MMP癌症的独特表型特征来开发MMP（1c）的遗传性和散发性癌症的诊断测定。在具体目标2中，我们将检验MMP通过多个增变基因的突变失活而逐渐展开的假设。我们建议研究“mutator，mutates另一个mutator”的模型。我们将完成对结直肠和胃MMP+腺癌的DNA错配修复（MMR）基因家族已知成员突变的筛查（2a）;对单个MMR增变基因突变及其组合在肿瘤细胞突变谱中的作用进行功能分析（2b）;并确定这些发现对MMP癌症的预后价值（2c）。在具体的目标3中，我们将检验这样的假设，即逃避凋亡是MMP肿瘤发生中的关键事件。 我们建议研究BAX突变失活导致MMP肿瘤细胞逃避凋亡和致瘤的机制。我们将完成MMP+和MMP-肿瘤中BAX突变的筛选（3a）;通过体内和体外试验对MMP癌症中BAX基因失活的作用进行功能分析（3b）;并研究BAX体细胞突变失活对MMP癌症的预后价值。

Gastrointestinal cancers of the microsatellite mutator phenotype (MMP) differ in genotype and phenotype from tumors without the MMP. APC, p53 and K-ras cancer genes are commonly mutated in MMP- tumors while mutational inactivation of TGFbetaRII and BAX is essentially restricted to MMP+ cancers. We propose that the existence and distinctive features of the MMP pathway for cancer, characteristic of tumors of the Hereditary Non-Polyposis Colorectal Cancer (HNPCC) syndrome and about 15% of sporadic gastrointestinal cancers, ultimately depends on the presence in some cancer genes of sequences target for the MMP. In specific aim 1 we will test the hypothesis of the existence of a MMP-dependent pathway for cancer. We propose to investigate the differences in genotype between tumors with or without the MMP. We will complete the screening of mutations in the APC suppressor gene in MMP+ and MMP- colon tumors (1a); determine whether the differences in genotype between MMP+ and MMP- gastrointestinal tumors also extend to widespread somatic changes in DNA methylation that we have observed in colon, breast and prostate cancer, specifically in the homeobox gene family (1b); and exploit the peculiar phenotypic features of MMP cancer to develop diagnostic assays for hereditary and sporadic cancer of the MMP (1c). In specific aim 2 we will test the hypothesis that the MMP unfolds gradually by the mutational inactivation of multiple mutator genes. We propose to investigate the model of the "mutator that mutates another mutator". We will complete the screening of colorectal and gastric MMP+ adenocarcinomas for mutations in the known members of the DNA mismatch repair (MMR) gene family (2a); perform a functional analysis of the effect of mutations in individual MMR mutator genes and their combinations in the spectra of mutations in the tumor cells (2b); and establish the prognostic value of these findings for cancer of the MMP (2c). In specific aim 3 we will test the hypothesis that the escape from apoptosis is a critical event in tumorigenesis of the MMP. We propose to investigate the mechanisms by which BAX mutational inactivation contributes to the escape from apoptosis and to tumorigenesis of tumors cells of the MMP. We will complete the screening of MMP+ and MMP- tumors for mutations in BAX (3a); perform a functional analysis of the role of BAX gene inactivation in cancer of the MMP by in vivo and in vitro assays (3b); and investigate the prognostic value of BAX somatic mutational inactivation for cancer of the MMP.