cyclin G2表达载体的构建及其对人胃癌细胞生长的作用

目的:构建包含人cyclinG2基因的真核表达载体,并探讨其对人胃癌细胞体外生长的作用。方法:从POE4细胞总RNA反转录产物中扩增出cyc-linG2cDNA,亚克隆至双顺反子真核表达载体pIRESneo中获得pIRES-G2重组质粒,基因转染SGC-7901细胞,G418筛选阳性克隆,免疫蛋白印迹杂交方法检测cyclinG2蛋白表达情况,平板克隆形成能力和四甲基噻唑蓝(MTT)比色法对转染后细胞的增殖活性进行分析。结果:成功构建包含cyclinG2基因真核重组表达载体pIRES-G2;转染pIRES-G2的SGC-7901细胞克隆的增殖活性明显下降。结论:cyclinG2基因转染后SGC-7901细胞体外增殖能力下降。     

Defects in G1-S cell cycle control in head and neck cancer: a review

Tumors gradually develop as a result of a multistep acquisition of genetic alterations and ultimately emerge as selfish, intruding and metastatic cells. The genetic defects associated with the process of tumor progression affect control of proliferation, programmed cell death, cell aging, angiogenesis, escape from immune control and metastasis. Fundamental cancer research over the last thirty years has revealed a multitude of genetic alterations which specify more or less separate steps in tumor development and which are collectively responsible for the process of tumor progression. The genes affected play in normal cells a crucial role in control over cell duplication and the interaction between cells, and between cells and their direct surrounding. This is illustrated on control during the G1/S phase of the cell cycle by its ultimate regulators: cyclins and cyclin dependent kinases. These proteins not only control the transition through the G1/S phase of the cell cycle, but also serve as mediators of the interaction between cells, and between cells and their surrounding. Defaults in the regulation of these proteins are associated with tumor progression, and, therefore, serve as targets for therapy. Defaults in those genes are found in various tumor types, although some of those prevail in particular tumor types. In this review emphasis is given to the defaults that occur in head and neck cancer.     

Expression of G1 phase cyclins in human gastric cancer and gastric mucosa of first-degree relatives

The aim of this study was to investigate the expression of D-type cyclins and cyclin E in gastric cancer patients (N = 34), in healthy first-degree relatives of gastric cancer patients (N = 29), and in control subjects (N = 18). Expression of cyclins D1, D2, D3, and E was determined by RT-PCR. Localization of cyclin expression was determined by immunohistochemistry. Expression of cyclins D2, D3, and E was more frequently detected in tumor tissue compared with tumor-free gastric mucosa (P < 0.05) and was associated with the presence of intestinal metaplasia. In contrast, cyclin D1 was frequently expressed in both tumor- and tumor-free tissue. Cyclin D3 expression was more frequently detected in the antrum mucosa of first-degree relatives compared to controls (P < 0.01) and was associated with the presence of Helicobacter pylori. Our data suggest that deregulation of G₁ phase cyclins may play a role in gastric carcinogenesis, and may point to the presence of molecular alterations in individuals at an increased risk for gastric cancer.     

G1‐S transition defects occur in most breast cancers and predict outcome

Cell cycle deregulation is frequently observed in tumors and has moreover been proposed to be a requirement for tumor development. By analyzing the expression of p27 by immunohistochemistry in 100 primary breast tumors and combining the analyses with our earlier characterization of cyclin E, D1, p16, and the retinoblastoma protein (pRB), we have been able to cover the majority of potential G1–S transition defects and observed that 90% of the tumors had alterations in one or several cell cycle regulatory proteins. Considerable variations in protein levels were found among tumors, with low p16 expression as the most common alteration followed by cyclin E or cyclin D1 overexpression, low p27 expression or pRB inactivation in decreasing prevalence. Tumors were grouped according to observed combinations of defects and the proliferative capacity was determined for each group by analyzing Ki–67 labeling index. Low proliferation was observed in tumors with: low p16; high cyclin Dl with normal or high p16 expression; and in tumors without cell cycle defects. Tumors with high cyclin E/low p27 or pRB defects showed higher proliferation. The survival differed noticeably for patients with various combinations of cell cycle defects, and four distinctive clusters were identified showing significantly different breast cancer specific survival (p<0.0001) for both node-positive (p=0.0006) and node-negative patients (p<0.0001). In summary, we have shown that G1-S transition defects are nearly obligatory in breast tumors and that the specific type of cell cycle defect influences the clinical behavior of the tumor.     

Apelin-13促大鼠血管平滑肌细胞增殖的PKC-ERK1/2信号通路研究

目的研究G蛋白偶联受体APJ(血管紧张素受体样受体或称血管紧张素受体AT1相关的受体蛋白,putativere-ceptor protein related to the angiotensin receptor AT1)的内源性配体apelin-13通过PKC-ERK1/2-Cyclins信号通路促进大鼠血管平滑肌细胞(vascular smooth muscle cells,VSMCs)增殖的影响。方法培养SD大鼠胸主动脉VSMCs,Western blot检测p-ERK1/2、ERK1/2、细胞周期蛋白CyclinD1和CyclinE的表达,四噻唑蓝比色法观察PKC阻断剂GF109203X对apelin-13促大鼠VSMCs增殖的影响。结果Apelin-13剂量依赖性和时间依赖性地促进大鼠VSMCsp-ERK1/2表达增加,对ERK1/2表达没有明显影响,GF109203X可明显抑制apelin-13诱导的细胞增殖及p-ERK1/2、CyclinD1和CyclinE的表达。结论Apelin-13促进大鼠VSMCs增殖可能与ape-lin-APJ-PKC-ERK1/2-Cyclins信号通路有关。     

Frequent Amplification of the Cyclin E Gene in Human Gastric Carcinomas

We searched for genetic alterations of the cyclin D1 and cyclin E genes in 45 human gastric carcinoma tissues. Expression of cyclin E mRNA and protein was also analyzed in eight of them by Northern and Western blots and immunohistochemical staining. The cyclin E gene was amplified 3–10 fold in seven gastric cancer tissues (15.6%), of which six were advanced gastric cancers. All of the cases with the cyclin E gene amplification displayed lymph node metastasis. Moreover, the case with the gene amplification overexpressed the cyclin E mRNA and protein. One of eight gastric cancer cell lines, MKN-7, shared the cyclin E gene amplification, and all of the gastric cancer cell lines expressed high levels of the cyclin E mRNA and protein even without gene amplification. Amplification of the cyclin D1 gene was not observed in any of the gastric carcinoma tissues or gastric carcinoma cell lines. These results suggest that the gene amplification and overexpression of cyclin E play an important role in the abnormal growth and progression of gastric carcinoma.     

Antiestrogen regulation of cell cycle progression and cyclin D1 gene expression in MCF-7 human breast cancer cells

The molecular mechanisms by which antiestrogens inhibit breast cancer cell proliferation are not well understood. Using cultured breast cancer cell lines, we studied the effects of antiestrogens on proliferation and cell cycle progression and used this information to select candidate cell cycle regulatory genes that are potential targets for antiestrogens. Under estrogen- and serum-free conditions antiestrogens inhibited proliferation of MCF-7 cells stimulated with insulin. Cells were blocked at a point in G₁ phase. These effects are comparable with those in serum- and estrogen-containing medium and were also seen to a lesser degree in nude mice bearing MCF-7 tumors. Similar observations with other peptide mitogens suggest that the process inhibited by antiestrogens is common to estrogen and growth factor activated pathways. Other studies have identified G₁ cyclins as potential targets for growth factor and steroid hormone/steroid antagonist regulation of breast epithelial cell proliferation. In MCF-7 cells growing in the presence of fetal calf serum, cyclin D1 mRNA was rapidly down-regulated by steroidal and nonsteroidal antiestrogens by an apparently estrogen receptor mediated mechanism. Cyclin D1 gene expression was maximally inhibited before effects on entry into S phase and inhibition was therefore not merely a consequence of changes in cell cycle progression. Together with data on the effects of antiestrogens in serum-free conditions [1], these results suggest down-regulation of cyclin D1 by antiestrogens may be a general phenomenon in estrogen receptor-positive breast cancer cells, independent of culture conditions and class of antiestrogen. These observations are compatible with the hypothesis that reductions in cyclin D1 levels may mediate in part the action of antiestrogens in blocking entry of cells into S phase.     

Prognostic significance of p27Kip1 expression in colorectal cancer: a clinico-pathological characterization

This study has evaluated the expression of the cyclin-dependent kinase inhibitor p27^Kip1 in 89 colorectal cancers (CRCs) using immunohistochemistry and has related p27 levels to clinico-pathological characteristics, tumour cell proliferation, and the expression of other G1–S transition regulatory proteins. Low levels of p27 were common in CRCs; 11 per cent of the tumours expressed very low levels and 44 per cent had p27 labelling indices (LIs) below 50 per cent. Except for depth of tumour invasion, no significant correlation was found between p27 expression and Dukes' stage, differentiation, growth pattern, tumour type or lymphocytic infiltration. Interestingly, tumours expressing low or very low p27 LIs were predominantly found in the right colon (p=0·026). Expression of p27 was a strong predictor of survival, both in univariate and in multivariate survival analyses; patients with tumours of p27 LI less than 50 per cent had an impaired prognosis (p=0·0069). p27 expression did not correlate with tumour cell proliferation, or with expression of cyclin D1 or the retinoblastoma protein (pRb). These findings support the view that p27 not merely controls cell cycle progression, but might be associated with other mechanisms responsible for aggressive tumour behaviour in colorectal cancer. Copyright © 1999 John Wiley & Sons, Ltd.     

D-type cyclins in adult human testis and testicular cancer: relation to cell type,proliferation, differentiation,and malignancy

D-type cyclins are proto-oncogenic components of the ‘RB pathway’, a G1/S regulatory mechanism centred around the retinoblastoma tumour suppressor (pRB) implicated in key cellular decisions that control cell proliferation, cell-cycle arrest, quiescence, and differentiation. This study focused on immunohistochemical and immunochemical analysis of human adult testis and 32 testicular tumours to examine the differential expression and abundance of cyclins D1, D2, and D3 in relation to cell type, proliferation, differentiation, and malignancy. In normal testis, the cell type-restricted expression patterns were dominated by high levels of cyclin D3 in quiescent Leydig cells and the lack of any D-type cyclin in the germ cells, the latter possibly representing the only example of normal mammalian cells proliferating in the absence of these cyclins. Most carcinoma-in-situ lesions appeared to gain expression of cyclin D2 but not D1 or D3, while the invasive testicular tumours showed variable positivity for cyclins D2 and D3, but rarely D1. An unexpected correlation with differentiation rather than proliferation was found particularly for cyclin D3 in teratomas, a conceptually significant observation confirmed by massive up-regulation of cyclin D3 in the human teratocarcinoma cell line NTera2/D1 induced to differentiate along the neuronal lineage. These results suggest a possible involvement of cyclin D2 in the early stages of testicular oncogenesis and the striking examples of proliferation-independent expression point to potential dual or multiple roles of the D-type cyclins, particularly of cyclin D3. These findings extend current concepts of the biology of the cyclin D subfamily, as well as of the biology and oncopathology of the human adult testis. Apart from practical implications for the assessment of proliferation and oncogenic aberrations in human tissues and tumours, this study may inspire further research into the emerging role of the cyclin D proteins in the establishment and/or maintenance of the differentiated phenotypes. Copyright © 1999 John Wiley & Sons, Ltd.