Molecular and Cellular Pharmacology Graduate Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
Cancer Biology Graduate Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
PLoS Genet. 2024 Oct 7;20(10):e1011437. doi: 10.1371/journal.pgen.1011437. eCollection 2024 Oct.
Mitotic Arrest Deficient 1 (gene name MAD1L1), an essential component of the mitotic spindle assembly checkpoint, is frequently overexpressed in colon cancer, which correlates with poor disease-free survival. MAD1 upregulation induces two phenotypes associated with tumor promotion in tissue culture cells-low rates of chromosomal instability (CIN) and destabilization of the tumor suppressor p53. Using CRISPR/Cas9 gene editing, we generated a novel mouse model by inserting a doxycycline (dox)-inducible promoter and HA tag into the endogenous mouse Mad1l1 gene, enabling inducible expression of HA-MAD1 following exposure to dox in the presence of the reverse tet transactivator (rtTA). A modest 2-fold overexpression of MAD1 in murine colon resulted in decreased p53 expression and increased mitotic defects consistent with CIN. After exposure to the colon-specific inflammatory agent dextran sulfate sodium (DSS), 31% of mice developed colon lesions, including a mucinous adenocarcinoma, while none formed in control animals. Lesion incidence was particularly high in male mice, 57% of which developed at least one hyperplastic polyp, adenoma or adenocarcinoma in the colon. Notably, mice expressing HA-MAD1 also developed lesions in tissues in which DSS is not expected to induce inflammation. These findings demonstrate that MAD1 upregulation is sufficient to promote colon tumorigenesis in the context of inflammation in immune-competent mice.
有丝分裂阻滞缺陷 1（基因名称 MAD1L1）是有丝分裂纺锤体组装检查点的必需组成部分，在结肠癌中经常过表达，与不良无病生存率相关。MAD1 的上调诱导了与组织培养细胞中的肿瘤促进相关的两种表型-染色体不稳定（CIN）的低发生率和肿瘤抑制因子 p53 的不稳定。我们使用 CRISPR/Cas9 基因编辑，通过将一个强力霉素（dox）诱导启动子和 HA 标签插入内源性小鼠 Mad1l1 基因中，生成了一种新型小鼠模型，使得在存在反向 tet 转录激活剂（rtTA）的情况下，HA-MAD1 可以在 dox 暴露后诱导表达。在小鼠结肠中适度过表达 MAD1 导致 p53 表达降低和有丝分裂缺陷增加，与 CIN 一致。在暴露于结肠特异性炎症剂葡聚糖硫酸钠（DSS）后，31%的小鼠发展出结肠病变，包括粘液性腺癌，而对照组动物无一例发生。雄性小鼠的病变发生率特别高，其中 57%的小鼠在结肠中至少形成了一个增生性息肉、腺瘤或腺癌。值得注意的是，表达 HA-MAD1 的小鼠也在 DSS 预计不会引起炎症的组织中发展出病变。这些发现表明，MAD1 的上调足以在免疫功能正常的小鼠的炎症背景下促进结肠肿瘤发生。
