Novel mouse colon cancer models and chemoprevention

描述(申请人提供)：纺锤体检查点延迟从中期到后期的进程，直到所有浓缩的染色体都正确地附着在有丝分裂纺锤体上。检查点功能受损通常会导致基因组不稳定，从而使细胞易于恶性转化。为了了解这种监督机制在人类癌症发展中功能失活的分子基础，PI的实验室专注于BubRl，一种关键的纺锤体检查点激酶，在维持基因组稳定和抑制肿瘤发生方面的作用。Pi的团队已经产生了BubRl+/-小鼠以及BubRl+/-ApcMin/+复合突变小鼠。在偶氮甲烷治疗后，BubRl+/-小鼠发生肠腺癌的速度加快。虽然ApcMin/+小鼠通常在小肠内发生许多腺瘤性息肉，但BubRl+/-ApcMin/+复合突变小鼠比ApcMin/+小鼠发生更多的自发性结肠肿瘤。BubRl+/-ApcMin/+小鼠的结肠肿瘤在临床上比ApcMin/+小鼠更晚期。此外，化学预防化合物如舒林酸硫化物和S-烯丙基硫代半胱氨酸能够诱导HT-29和SW-480结肠癌细胞凋亡，BubR1缺陷细胞对这些化合物诱导的凋亡更具抵抗力。鉴于BubRl和Ape都参与了正常细胞基因组稳定性的调节，我们假设BubRl+/-ApcMin+/-小鼠将是一个很好的啮齿动物模型，可以评估各种针对结肠的化学预防化合物的抗肿瘤活性，并了解纺锤体检查点组件在维持基因组稳定性方面的体内作用。为了验证这一假说，Pi的实验室将(I)验证和测试直接靶向微管或有丝分裂纺锤体的舒林酸和S-烯丙基硫代半胱氨酸(或其衍生物)对BubRl+/-ApcMin/+复合突变小鼠自发性肠道肿瘤发生的抑制作用；(Ii)通过研究(A)BubRl和/或APE缺陷细胞的基因组不稳定性和自发转化率，(B)舒林酸和S-烯丙基硫代半胱氨酸的抗增殖作用对纺锤体检查点完整性的依赖，来研究这些突变小鼠的肠癌发生的分子基础。以及(C)在BubRl缺乏的遗传背景下，ApcMin/+小鼠将肿瘤负担从小肠转移到结肠的机制。该项目的长期目标是阐明细胞周期检查点和Wnt信号通路调节细胞增殖和分化以及基因组稳定性的机制。

DESCRIPTION (provided by applicant): The spindle checkpoint delays the progression from metaphase to anaphase until all condensed chromosomes are properly attached to mitotic spindles. An impaired checkpoint function often results in genomic instability, which predisposes cells to malignant transformation. To understand the molecular basis of functional inactivation of this surveillance mechanism in human cancer development, the Pi's laboratory has focused on the role of BubRl, a key spindle checkpoint kinase, in the maintenance of genomic stability and suppression of tumorigenesis. The Pi's group has generated BubRl+/- mice as well as BubRl+/-ApcMin/+ compound mutant mice. BubRl+/- mice develop intestinal adenocarcinomas at an accelerated rate after azoxymethane treatment. Whereas ApcMin/+ mice develop many adenomatous polyps generally within the small intestine, BubRl+/-ApcMin/+ compound mutant mice develop significantly more spontaneous colonic tumors than ApcMin/+ mice. The colon tumors in BubRl+/-ApcMin/+ mice are clinically more advanced than those observed in ApcMin/+ mice. Moreover, chemopreventive compounds such as sulindac sulfide and S-allylmercaptocysteine are capable of inducing apoptosis in HT-29 and SW-480 colon tumor cells; BubRl - deficient cells are more resistant to apoptosis induced by these compounds. Given that both BubRl and Ape are involved in the regulation of genomic stability in normal cells, we hypothesize that BubRl+/-ApcMin+/- mice would be an excellent rodent model for evaluating the efficacy of anti-tumor activities of various chemopreventive compounds that target colon and understanding the in vivo role of spindle checkpoint components in the maintenance of genomic stability. To test this hypothesis, the Pi's lab will (i) validate and test the chemopreventive effect of sulindac and S-allylmercaptocysteine, which (or the derivative of which) directly target microtubules or mitotic spindles, on suppression of spontaneous intestinal tumorigenesis in BubRl+/- ApcMin/+ compound mutant mice, and (ii) investigate the molecular basis of intestinal carcinogenesis in these mutant mice by studying (a) the genomic instability and the rate of spontaneous transformation of cells deficient in BubRl and/or Ape, (b) the dependence of anti-proliferative effect of sulindac and S-allylmercaptocysteine on the integrity of the spindle checkpoint, and (c) the mechanism by which ApcMin/+ mice shift in tumor burden from the small intestine to colon in the BubRl-deficient genetic background. The long-term goal of this project is to elucidate the mechanism by which cell cycle checkpoints and the Wnt signaling pathway regulate cell proliferation and differentiation as well as genomic stability.