胃癌细胞中AP-1活性与RARα介导的相关性

为确定全反式视黄酸 ( ATRA)抑制胃癌细胞 AP- 1活性过程中 RARα介导的作用机理 ,利用 Northern印迹和 Western印迹测定 RARα基因和 c Jun、c Fos蛋白表达水平 ;氯霉素乙酰转移酶活性 ( CAT)分析 AP- 1活性 ;以及 MTT法检测细胞生长速率 .结果表明 ,ATRA能够诱导 RARα表达 ,抑制 c Jun和 c Fos蛋白表达和 AP- 1活性 ,由此导致胃癌细胞生长抑制 .结果证实 ,ATRA抑制胃癌细胞 AP- 1活性是抑制细胞生长的重要途径之一 ,并与 RARα介导密切相关 .     

胃癌细胞中视黄酸受体抑制AP-1活性的不同方式

 研究胃癌细胞中视黄酸受体RARα和RARβ抑制活化蛋白 1(activatorprotein 1,AP 1)活性的不同方式及其与全反式视黄酸 (ATRA)作用的相关性 .瞬时转染RARβ表达载体到MKN 4 5细胞后 ,佛波脂 (TPA)诱导的AP 1活性受到明显抑制 ,且与RARβ浓度正相关 ,与ATRA存在与否无关 ;相反 ,RARα转染细胞后 ,对TPA诱导的AP 1活性的抑制不仅与RARα的浓度相关 ,而且依赖于AT RA .凝胶阻抑测定表明 ,TPA可以显著加强AP 1结合活性 ,当ATRA处理不表达RARβ和低表达RARα的MKN 4 5细胞后 ,AP 1结合活性不受影响 ;然而 ,表达RARα和RARβ的BGC 82 3细胞经AT RA处理后 ,TPA诱导的AP 1结合活性则受到抑制 .另外 ,分析与抗AP 1活性相关的RARβ功能区表明 ,DNA结合区的缺失导致RARβ抑制AP 1活性作用的丧失 ,而配体结合区对于RARβ抑制AP 1活性则是非必需的 .以上结果证实 ,有胃癌细胞中 ,RARβ可能是AP 1活性的抑制因子 ,RARα则可能是ATRA作用的靶向 .尽管它们的作用方式有所不同 ,但最终都可以通过抑制AP 1活性来抑制胃癌细胞生长     

Aromatase expression and its localization in human breast cancer

Aromatization or in situ estrogen production by aromatase has been considered to play an important role in the development of human breast carcinoma. In the human breast, aromatase overexpression is observed in the stromal or interstitial cells of the carcinoma, especially at the sites of frank invasion and/or adipose tissue. Transplantation experiments in the nude mouse employing MCF-7 and/or SF-TY human fibroblast cell lines revealed that aromatase activity and expression were much higher in the tumour with MCF-7 and SF-TY than that with MCF-7 alone. Aromatase overexpression in human breast carcinoma tissue is considered to occur as a result of carcinomastromal cell interactions, i.e. paracrine communication between stromal and carcinoma cells. Aromatase overexpression is correlated with the malignant phenotype in the human breast, but not with stage, age, clinical stages, clinical course, or proliferative activity of breast carcinoma. Aromatase overexpression may be correlated with development, rather than the biological behaviour of breast malignancy. Aromatase overexpression is not necessarily correlated with expression of 17β-hydroxysteroid dehydrogenase type 1, which converts estrone to estradiol and estrogen receptor. Different mechanisms may be involved in the regulation of expression of these two important estrogen-metabolizing enzymes and estrogen receptor in human breast cancer. Aromatase overexpression in intratumoral stromal cells was much more frequently detected in male breast cancer than in female counterparts, which confers a growth advantage on cancer cells in a male hormonal environment with low serum estrogen levels.     

Unregulated expression of c-Jun or c-Fos proteins but not Jun D inhibits oestrogen receptor activity in human breast cancer derived cells.

We present evidence that oestrogen receptor activity in human MCF-7 breast cancer cells is reduced by over-expression of c-Jun or c-Fos proteins and to a lesser extent by Jun B overexpression. In contrast, overexpression of Jun D protein does not affect the activity of the oestrogen receptor. A region of c-Jun found to be required for repression of oestrogen receptor activity is located outside the DNA binding domain and is not conserved among the three Jun proteins. Finally, we suggest that c-Jun and c-Fos act independently to inactivate the oestrogen receptor.     

Cripto-1 overexpression leads to enhanced invasiveness and resistance to anoikis in human MCF-7 breast cancer cells

Cripto-1 (CR-1) is an epidermal growth factor (EGF)-CFC protein that has been shown to signal through nodal/Alk-4, PI3K/Akt, and/or ras/raf/MEK/MAPK pathways in mammalian cells, and that is frequently expressed in human primary breast carcinomas. In the present study, the human estrogen receptor positive, MCF-7 breast cancer cell line, that expresses low levels of endogenous CR-1, was transfected with a CR-1 expression vector. MCF-7 CR-1 cells expressed high levels of a 25 kDa recombinant CR-1 protein that was not detected in MCF-7 cells transfected with a control vector (MCF-7 neo). Overexpression of CR-1 did not induce an estrogen independent phenotype in MCF-7 cells. In fact, MCF-7 CR-1 cells showed a response to exogenous estrogens that was similar to MCF-7 neo cells, and failed to grow in immunosuppressed mice in absence of estrogen stimulation. However, MCF-7 CR-1 cells showed a rate of proliferation in serum free conditions, and an ability to form colonies in soft-agar that were higher as compared with MCF-7 neo cells. More importantly, overexpression of CR-1 enhanced the resistance to anoikis and the invasion ability of MCF-7 cells. MCF-7 CR-1 cells showed levels of activation of both Akt and Smad-2 that were significantly higher as compared with MCF-7 neo. These findings suggest that CR-1 overexpression might be associated with the progression towards a more aggressive phenotype in breast carcinoma, through the activation of both Akt and Smad-2 signalling pathways.