Molecular mechanism of endometrial cancer and its application to gene diagnosis

1. 子宫内膜癌抑制基因位点的鉴定：位于染色体1q的基因具有诱导子宫内膜癌细胞衰老的能力。通过将一条发生间质缺失约63 cM的del 1q染色体或来自1q的亚染色体可转移片段引入子宫内膜癌细胞，我们确定了1q31-ter内靶基因的定位。此外，我们利用60例子宫内膜癌样本分析了1q上的LOH，缩小了1q42.2的定位范围。ER对Ras介导转化的贡献。突变的K-ras蛋白具有诱导转录因子ER蛋白（3倍）表达的能力。内质网活性增强的重组细胞具有致瘤性，而内质网活性降低的重组细胞无致瘤性。抑制内质网活性导致突变k-ras转化的细胞失去致瘤性。子宫内膜癌中DPC4和DOC基因均被18q LOH靶向。18qLOH在子宫内膜癌中很常见。通过绘制18q上的详细缺失图谱，我们发现缺失同时针对DPC4和DOC基因。剩余等位基因中DPC4启动子区域的突变导致DPC4基因活性的抑制。反过来，转染DOC cDNA可抑制子宫内膜癌细胞的致瘤性或诱导细胞凋亡。DOC基因通过诱导子宫内膜细胞凋亡发挥抑癌基因的作用。p53依赖性cyclin G的功能：Dox处理诱导p53积累、p21和cyclin G转录，导致细胞G2/M阻滞。反过来，NaB诱导p53积累和p21转录，但不诱导cyclin G转录，导致细胞G1阻滞。抑制cyclin G的表达与细胞从G2/M中释放相对应。过表达cyclin G可使细胞恢复凋亡易感。

1. Identification of an endometrial cancer suppressor gene locus : The gene located chromosome 1q has an ability to induce senescence in endometrial cancer cells. By introducing a del 1q chromosome that has incurred an interstitial deletion of approximately 63 cM or subchromosomal transferable fragments derived from the 1q into the endometrial cancer cells, we identified the localization of a target gene within 1q31-ter. In addition, we analyzed LOH on 1q using 60 sample of endometrial cancers and narrowed down the localization with 1q42.2. Contribution of ER to Ras mediated transformation. Mutant K-ras protein had an ability to induce expression of ER protein (3-fold) that functioned as a transcription factor. Reconstituted cells that had enhanced ER activities were tumorigenic but the cells with lower ER activities were nontumorigenic. Suppression of ER activities resulted in the loss of tumorigenicity in the cells transformed by mutant k-ras.3. Both DPC4 and DOC genes targeted by 18q LOH in endometrial cancers. : 18qLOH is frequent in endometrial cancers. By making a detailed deletions map on 18q, we found that deletions targeted both DPC4 and DOC genes. Mutations of the DPC4 promoter regions in the remaining allele resulted in the suppression of DPC4 gene activities. In turn, transfection of DOC cDNA resulted in the suppression of tumorigenicity or the induction of apoptosis in endometrial cancer cells. A DOC gene functions as a tumor suppressor gene by inducing apoptosis of endometrial cells.4. Function of p53-dependent cyclin G : Dox treatment induced p53 accumulation, p21 and cyclin G transcription, that resulted in G2/M arrest of cells. In turn, NaB induced p53 accumulation and p21 transcription but not cyclin G transcription, that resulted in G1 arrest of cells. Suppression of cyclin G expression corresponded to the release of cells from G2/M. Overexpression of cyclin G reverted the cell susceptible to apoptosis.