窖蛋白-1与肿瘤

窖蛋白是胞膜窖结构中的特征性结构蛋白。窖蛋白在细胞内吞、胆固醇运输、细胞膜组装、调节信号转导和肿瘤生成、转移等生命活动中扮演了重要角色。窖蛋白基因家族中的窖蛋白-1(Cav-1)可能参与肿瘤生成和转移的病理机制,以及与多药耐药等密切相关。窖蛋白-1参与调节细胞周期与信号转导,在细胞凋亡程序中发挥重要作用,具有抗血管新生,负性调节生长因子,参与肿瘤细胞侵袭和转移的作用。

Overexpression and mutations of tumor suppressor gene p53 in hepatocellular carcinoma

AIMS To examine the prevalance of p53 mutations in hepatocellular carcinoma (HCC) from Chongqing area and the relationship between the p53 mutations and clinicopathological features of HCC,as well as the risk factors. METHODS The overexpression and point mutations of tumor suppressor gene p53 in 38 cases of HCC were detected by a sensitive antigen retrieval fluid (ARF) immunohistochemical method and polymerase chain re- action(PCR)-restriction fragment length polymorphism (RFLP),and single strand conformation polymorphism (SSCP)-silver staining analysis. RESULTS The results showed that 16 of 38 HCCs had positive p53 protein (42.1%),7 HCCs had p53 mutation at 249 (18.4 % ) and 2 HCCS had point muta- tion within exon 7 other than 249. Among 9 cases of HCC with mutations,8 cases demonstrated positive p53 protein,its coincidental rate was 88.9%. The overexpression and mutations of p53 were significantly related to the differentiation and metastasis of HCCs. The frequency of p53 mutations was consistent with high prevalence of HBV and a moderate aflatoxin B1 (AFB1) exposure in our area. CONCLUSIONS The results suggest that AFB1 acts synergistically with HBV in the generation of p53 mutations. Furthermore,dietary exposure to AFB1 may mainly contribute to the tumor specific mutation at codon 249,while HBV may account for other scattered mutations in HCC.

Expression of cellular FLICE-inhibitory protein and its association with p53 mutation in colon cancer

AIM: To investigate the expression of cellular FLICE (Fas associated death domain-like IL-lbeta-converting enzyme)-inhibitory protein (c-FLIP) and its association with p53 mutation in colon cancer. METHODS: Immunohistochemical staining of c-FLIP and mutant p53 by using specific antibodies was performed by the standard streptavidin-peroxidase technique for 45 colon cancer tissue samples with matched normal tissues. Semi-quantitative reverse transcriptional (RT)-PCR was used to measure c-FLIP mRNA levels, t-test statistical method was used in data analyses. RESULTS: c-FLIP mRNA was expressed in all colon cancer tissues and its level (0.63±0.12) was significantly higher than that in normal tissues (0.38±0.10, P<0.01). Immuno-histochemically, c-FLIP protein was also expressed in all colon cancers (45/45) and 71.1% (32/45) showed an intense immunostaining, in contrast, 93.3% (42/45) of normal colonic mucosa showed positive staining and none of them immunostained intensely. The quantity of c-FLIP protein was significantly higher in cancer tissues than in normal mucosa (7.04±1.20 vs 5.21±0.86, P<0.01). Positive staining of mutant p53 protein was found in 60% (27/45) colon cancers. c-FLIP mRNA level was decreased in p53 positive group compared with p53 negative cancer tissues (0.59±0.13 vs0.69±0.14, P<0.01), but c-FLIP protein had a significantly higher level in p53 positive cancer tissues than in negative ones (7.57±1.30 vs6.25±1.27, P<0.01). CONCLUSION: c-FLIP is specially overexpressed in colon cancers and it might contribute to carcinogenesis of normal colonic mucosa. p53 may exert transcriptional upregulation effects on c-FLI P gene and more potent effects on promoting the degradation of c-FLIP protein.

53BP1与DNA双链断裂损伤修复

DNA的精确复制和遗传对维持基因组稳定性有重要作用。DNA双链断裂损伤可能诱导细胞凋亡和染色质重排,在肿瘤的发生发展过程中发挥作用。53BP1是DNA双链断裂修复中的重要调节蛋白质之一,对调控损伤修复平衡和维持基因组稳定性起着重要作用。本文主要对53BP1的结构、生物学功能、信号通路、分子机制和翻译后修饰做一浅显的总结和展望,希望能为53BP1的深入研究提供一些理论基础。

Modulation of the MAP kinase signaling cascade by Raf kinase inhibitory protein

Proteins like Raf kinase inhibitory protein (RKIP) that serve as modulators of signaling pathways, either by promoting or inhibiting the formation of productive signaling complexes through protein-protein interactions, have been demon- strated to play an increasingly important role in a number of cell types and organisms. These proteins have been implicated in development as well as the progression of cancer. RKIP is a particularly interesting regulator, as it is a highly conserved, ubiquitously expressed protein that has been shown to play a role in growth and differentiation in a number of organisms and can regulate multiple signaling pathways. RKIP is also the first MAP kinase signaling modulator to be identified as playing a role in cancer metastasis, and identification of the mechanism by which it regulates Raf-1 activation provides new targets for therapeutic intervention.

Tumor suppressor protein C53 antagonizes checkpoint kinases to promote cyclin-dependent kinase 1 activation

Cyclin-dependent kinase 1 （Cdkl）/cyclin B1 complex is the driving force for mitotic entry, and its activation is tightly regulated by the G2/M checkpoint. We originally reported that a novel protein C53 （also known as Cdk5rap3 and LZAP） potentiates DNA damage-induced cell death by modulating the G2/M checkpoint. More recently, Wang et al. （2007） found that C53/LZAP may function as a tumor suppressor by way of inhibiting NF-kB signaling. We re- port here the identification of C53 protein as a novel regulator of Cdkl activation. We found that knockdown of C53 protein causes delayed Cdkl activation and mitotic entry. During DNA damage response, activation of checkpoint kinase 1 and 2 （Chkl and Chk2） is partially inhibited by C53 overexpression. Intriguingly, we found that C53 inter- acts with Chkl and antagonizes its function. Moreover, a portion of C53 protein is localized at the centrosome, and centrosome-targeting C53 potently promotes local Cdkl activation. Taken together, our results strongly suggest that C53 is a novel negative regulator of checkpoint response. By counteracting Chkl, C53 promotes Cdkl activation and mitotic entry in both unperturbed cell-cycle progression and DNA damage response.

Expression of a novel apoptosis inhibitor-survivin in colorectal carcinoma

AIM： To investigate the role of survivin expression in the pathogenesis of colorectal carcinoma. METHODS： Immunohistochemistry S-P method and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNE） were used to detect the expression of survivin and apoptotic cell in situ in colorectal cancerous tissues, para-cancerous tissues and normal tissues of 48 cases of colorectal carcinoma. RESULTS： The survivin positive unit （PU） was higher in cancerous tissues （38.76±5.14） than in para-cancerous （25.17±7.26） or normal tissues （0.57±0.03） （P〈0.05）. The apoptosis index （AI） of para-cancerous tissues was （7.51±2.63%） higher than cancerous tissues （4.65±1.76%）. The expression of survivin was associated with pathological grade, lymph node metastasis and Dukes stage of colorectal carcinoma. CONCLUSION： Survivin expression may play an important role in carcinogenesis of colorectal carcinoma and may be associated with malignant biological behaviors of colorectal carcinoma.

DNA methylation in hepatocellular carcinoma

As for many other tumors,development of hepatocellular carcinoma(HCC)must be understood as a multistep process with accumulation of genetic and epigenetic alterations in regulatory genes,leading to activation of oncogenes and inactivation or loss of tumor suppressor genes(TSG).In the last decades,in addition to genetic alterations,epigenetic inactivation of(tumor suppressor) genes by promoter hypermet hylation has been recognized as an important and alternative mechanism in tumorigenesis.In HCC,aberrant methylation of promoter sequences occurs not only in advanced tumors, it has been also observed in premalignant conditions just as chronic viral hepatitis B or C and cirrhotic liver. This review discusses the epigenetic alterations in hepatocellular carcinoma focusing DNA methylation.

p53-independent pRB degradation contributes to a drug-induced apoptosis in AGS cells

The retinoblastoma (RB) tumor suppressor protein, pRB, plays an important role in the regulation of mammalian cell cycle. Furthermore, several lines of evidence suggest that pRB also involves in the regulation of apoptosis. In the present study, the degradation of pRB was observed in apoptotic gastric tumor cells treated with a new potent anti-tumor component, tripchlorolide (TC). The inhibition of pRB degradation by a general cysteine protease inhibitor IDAM resulted in the reduction of the apoptotic cells. Furthermore, the survival of the gastric tumor cells under the TC treatment was enhanced by an over-expression of exogenous pRB. These results suggest that the pRB degradation of the gastric tumor cells under the TC treatment involves in the apoptotic progression. In addition, the same extent of TC- induced pRB-degradation was detected in the gastric tumor cells containing a p53 dominant-negative construct, indicat- ing that this kind of pRB degradation is p53-independent.

The Inhibitory Effects of Arresten Protein on Tumor Formation

Objective To examine the inhibitory effects of recombinant purified arresten on tumor formation. Methods Purified arresten protein was incubated with human umbilical vein endothelial cells (HUVECs) and HeLa cells in vitro. The effect on proliferation of HUVECs and HeLa cells was examined using 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide assay, and apoptosis of these cells monitored by flow cytometry. The effect on migration of HUVECs and HeLa cells was examined by Boyden chamber. Twenty colon carcinoma-bearing C67BL/6 mice were used to investigate the antitumor effects of arresten protein. The mice were randomly divided into arresten treatment group (n=10) and control group (n=10). The microvessel densities of the tumors were measured by immunohistochemical staining with anti-CD31 monoclonal antibody. Results Arresten inhibited the proliferation and migration of HUVECs in a dose-dependent manner while promoting apoptosis. However, arresten had no significant effects on the proliferation and apoptosis of HeLa cells. The migration of HeLa cells was modestly inhibited by arresten. The arresten treatment group of mice showed no weight loss or unusual behavior during the course of treatment, and the tumor growth was significantly decreased; in contrast, the control group of mice exhibited rapidly growing tumors and cachexia. A dramatically decreased microvessel density in tumor tissues was found in arresten-treated mice compared with that in the control mice. Conclusion Arresten can inhibit tumor growth through inhibition of tumor angiogenesis.

Simian virus 40 large tumor antigen forms specific complexes with p53 and pRb in human brain tumors

目的 探讨SV4 0早期区域基因编码产物大T抗原 (Tag)的表达及其与抑癌蛋白p53、pRb的相互作用在人脑肿瘤发生、发展中的意义。方法 采用免疫共沉淀结合银染色及Western印迹法检测 6 5例人脑肿瘤及 8例正常人脑组织中Tag的表达 ,并对 18例和 15例Tag阳性瘤组织分别检测Tag p53和Tag pRb复合物的形成。结果 Tag在 8例室管膜瘤及 2例脉络丛乳头状瘤中全部表达 ,垂体腺瘤Tag阳性率为 90 % (9/ 10 ) ,星形细胞瘤为 73% (11/ 15) ,脑膜瘤为 70 % (7/ 10 ) ,多形性胶质母细胞瘤为 50 % (4 / 8) ,髓母细胞瘤为 33% (2 / 6 ) ;5例少枝胶质细胞瘤、1例松果体细胞瘤及 8例正常人脑组织无Tag表达 ;检测 18例和 15例Tag阳性瘤组织 ,均发现Tag可与p53、pRb形成特异性复合物。结论 在人脑肿瘤组织中Tag不仅可以表达 ,而且还可与p53、pRb形成特异性复合物。Tag p53及Tag pRb特异性复合物的形成导致p53和pRb失活 ,这可能是SV4 0导致人脑肿瘤发生的一个重要机理。

Study of the prodrugs of peptide aldehydes as proteasome inhibitors

To improve the stability of peptide aldehyde proteasome inhibitors, four peptide cycloacetal derivatives and two peptide heterocycle compounds were designed and synthesized. Their proteasome inhibition and in vitro anticancer activities were evaluated. The four peptide cycloacetal derivatives did not showed any activities, which demonstrated that this kind of cycloacetal derivatives might be suitable as prodrugs. The two peptide heterocycle compounds were found to show obvious activities at both enzyme and cell levels. These results provide us a new clue for the modification of peptide aldehyde proteasome inhibitors.