Hsu Hsi-Hsien, Cheng Sue-Fei, Chen Li-Mien, Liu Jer-Yu, Chu Chun-Hsien, Weng Yi-Jiun, Li Zih-Ying, Lin Chung-Sheng, Lee Shin-Da, Kuo Wei-Wen, Huang Chih-Yang
Division of Colorectal Surgery, Mackay Memorial Hospital, Taipei, Taiwan.
Mol Cell Biochem. 2006 Sep;289(1-2):101-9. doi: 10.1007/s11010-006-9153-3. Epub 2006 Apr 21.
Epidemiologic studies reported that the prevalence of hereditary non-polyposis colon cancer (HNPCC) in male is about 1.5-fold higher than that in female. Decreases in circulatory estrogen (E(2)) have been reported to downregulate the expression of E(2) receptor (ER) and significantly increase the risk of colorectal cancer. Patients that received E(2) replacement therapy were found to have a reduction in the incidence of colon adenoma and carcinoma. Furthermore, significant decreases in the expression of ER have been found in colorectal cancer specimens. Evidences strongly suggest the protective roles of E(2) and ER against colorectal cancer. However, the mechanisms of ERalpha effects on colorectal cancer cells remained un-clear. LoVo cells were transient transfected to overexpress ERalpha, DNA fragmentation and the activated caspases measurements were performed to evaluate apoptotic effects. Western blotting was used to evaluate protein levels, and luciferase activity assay to measure the Htnf-a promoter activity. The results clearly demonstrated that overexpressed ERalpha with or without E(2) (10(-8) M) treatment could activate caspase -8, -9, and 3 and induce DNA fragmentation in LoVo cell. At the same time, overexpressed ERalpha plus E(2) significantly increases the expression and promoter activity of hTNF-alpha, and the DNA fragmentation effect induced by E(2) plus ERalpha were reduced by the addition of hTNF antibody (0.1 ng(ml). In addition, E(2) plus ERalpha significantly upregulated p21 and p27 levels and downregulated the beta-catenin and its target genes, cyclin D1 and Rb, which regulate the cell cycle and cell proliferation. The results indicate that E(2) plus overexpressed ERalpha induce LoVo cell apoptosis might mediate through the increase of hTNF-alpha gene expression, which in turn activate caspase-8, -9 and caspase-3 and lead to the DNA fragmentation and apoptosis. E(2) plus ERalpha also showed the downregulation of beta-catenin signalings implicating the suppression of proliferation and metastasis of colorectal cells. Efforts aiming at enhancing ERalpha expression and(or activity may be proved to be an alternative therapy against colorectal cancer.
流行病学研究报告称，遗传性非息肉病性结直肠癌（HNPCC）在男性中的患病率比女性高约1.5倍。据报道，循环雌激素（E₂）水平降低会下调E₂受体（ER）的表达，并显著增加患结直肠癌的风险。接受E₂替代疗法的患者结肠腺瘤和癌的发病率有所降低。此外，在结直肠癌标本中发现ER的表达显著降低。有充分证据表明E₂和ER对结直肠癌具有保护作用。然而，ERα对结直肠癌细胞的作用机制仍不清楚。将LoVo细胞瞬时转染以过表达ERα，进行DNA片段化和活化半胱天冬酶检测以评估凋亡效应。使用蛋白质印迹法评估蛋白质水平，使用荧光素酶活性测定法测量Htnf-α启动子活性。结果清楚地表明，无论有无E₂（10⁻⁸ M）处理，过表达的ERα均可激活半胱天冬酶-8、-9和-3，并诱导LoVo细胞中的DNA片段化。同时，过表达的ERα加E₂显著增加hTNF-α的表达和启动子活性，并且添加hTNF抗体（0.1 ng/ml）可降低E₂加ERα诱导的DNA片段化效应。此外，E₂加ERα显著上调p21和p27水平，并下调β-连环蛋白及其调控细胞周期和细胞增殖的靶基因细胞周期蛋白D1和Rb。结果表明，E₂加过表达的ERα诱导LoVo细胞凋亡可能是通过增加hTNF-α基因表达来介导，并进而激活半胱天冬酶-8、-9和半胱天冬酶-3，导致DNA片段化和凋亡发生。E₂加ERα还显示出β-连环蛋白信号通路下调，这意味着结直肠细胞的增殖和转移受到抑制。旨在增强ERα表达和（或）活性的努力可能被证明是一种治疗结直肠癌的替代疗法。
