A novel mouse colon cancer model and chemoprevention

描述（由申请方提供）：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正确附着到有丝分裂纺锤体上。检查点功能受损通常会导致基因组不稳定性，从而使细胞易于发生恶性转化。为了了解这种监视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）在维持基因组稳定性和抑制肿瘤发生中的作用。Pi的小组已经产生了BubRl+/-小鼠以及BubRl+/-ApcMin/+复合突变小鼠。BubRl+/-小鼠在氧化偶氮甲烷处理后以加速的速率发展肠腺癌。ApcMin/+小鼠通常在小肠内发展许多腺瘤性息肉，而BubRl+/-ApcMin/+化合物突变小鼠比ApcMin/+小鼠发展显著更多的自发性结肠肿瘤。BubRl+/-ApcMin/+小鼠中的结肠肿瘤在临床上比在ApcMin/+小鼠中观察到的结肠肿瘤更晚期。此外，化学预防化合物如舒林酸硫化物和S-烯丙基巯基半胱氨酸能够诱导HT-29和SW-480结肠肿瘤细胞的凋亡; BubRl缺陷型细胞对这些化合物诱导的凋亡更具抗性。鉴于BubRl和Ape都参与正常细胞中基因组稳定性的调节，我们假设BubRl+/-ApcMin+/-小鼠将是用于评估靶向结肠的各种化学预防化合物的抗肿瘤活性的功效和理解纺锤体检查点组分在维持基因组稳定性中的体内作用的极好的啮齿动物模型。为了验证这一假设，Pi的实验室将（i）验证和测试舒林酸和S-烯丙基巯基半胱氨酸的化学预防作用，（或其衍生物）直接靶向微管或有丝分裂纺锤体，抑制BubR 1 +/- ApcMin/+复合突变小鼠中自发性肠肿瘤发生，和（ii）通过研究（a）BubR 1缺陷的细胞的基因组不稳定性和自发转化率，和/或（b）BubR 1缺陷的细胞的基因组不稳定性和自发转化率，研究这些突变小鼠中肠癌发生的分子基础。或Ape，（B）舒林酸和S-烯丙基巯基半胱氨酸的抗增殖作用对纺锤体检查点完整性的依赖性，和（c）在BubR 1缺陷遗传背景下ApcMin/+小鼠肿瘤负荷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.