17aα-D-高炔雌二醇-3-乙酯联合化疗抗肿瘤作用研究

目的:观察17aα-D-高炔雌二醇-3-乙酯及其联合化疗对EC901食管癌的抑制作用。方法:将接种EC901瘤细胞的裸鼠分为对照组、17aα-D-高炔雌二醇-3-乙酯组、5-氟尿嘧啶(5-Fu)组、17aα-D-高炔雌二醇-3-乙酯联合5-Fu组,连续给药9d,分别检测肿瘤抑制率、外周血常规、骨髓有核细胞计数、肿瘤病理等指标。结果:17aα-D-高炔雌二醇-3-乙酯治疗组瘤重明显小于对照组,联合5-Fu组肿瘤生长分别低于5-Fu组和照射组。结论:17aα-D-高炔雌二醇-3-乙酯联合5-Fu对EC901食管癌的抑制具有增效作用。

Aberrant Methylation in CpG Islands of pl5 and pl6 Tumor Suppressor Genes in Pancreatic Cancer Tissue

Objective： To detect the aberrant methylation patterns in the CpG islands of p16 and p15 tumor suppressor genes, and to analyze its correlation with pancreatic carcinogenesis and with clinicopathological characteristics of patients with pancreatic cancer （PC）. Methods： The methylation-specific polymerase chain reaction （MSP） method was used to monitor methylation patterns in the CpG islands of p15 and p16 genes from 29 cases of PC and 3 cases of chronic pancreatitis （CP） paraffin-embedded tissue, as well as 2 cases of normal liver tissues and 12 cases of normal blood samples. Results： p15 and p16 genes were detected to show unmethylation patterns and no amplification using methylation-specific primers in control group. The aberrant methylation rates of p16 in carcinoma tissue and adjacent noncarcinoma tissue were 37.9% （11 of 29 cases） and 34.5% （10 of 29 cases） respectively. Of the 11 aberrant methylated samples, 5 showed complete methylation and 6 hemimethylation. The methylation rates of p15 gene in carcinoma tissue and adjacent noncarcinoma tissue were 27.5% （8/29） and 24.4% （7/29） respectively. Of the 8 aberrant methylated samples, 3 showed complete methylation and 5 hemimethylation. In 6 PC samples, aberrant methylation in CpG islands of both p15 and p16 genes existed simultaneously. The aberrant methylation patterns in CpG islands of p15 and p16 genes had no close correlation with the clinicopathological characteristics （age, sex, smoking, volume of primary tumor, differentiation, clinical stage and histological classification） of the patients with PC （P〉0.05）. Conclusion： The aberrant methylation in CpG islands of p15 and p16 genes could be regarded as an early molecular event in PC and had no close correlation with the clinicopathological characteristics of the patients with PC.

The Relationship between Methylation and Expression Defect of Tumor Suppressor Gene p16INK4A in Epithelial Ovarian Cancer

Objective： To evaluate the expression of p16INK4A gene in ovarian cancer and analyze the relation between this alteration and the promoter methylation of p16INK4A DNA. Methods： Seven ovarian cancer cell lines and eighteen ovarian cancer specimens were selected for the study. Genomic DNA and RNA were extracted from fresh tissues and cell lines, DNA was treated with sodium bisulfite and then analyzed with methylation-specific PCR （MSP） to detect p16INK4A methylation. The expression of p16INK4A mRNA was detected by reverse transcription-polymerase chain reaction （RT-PCR）. In addition, the proliferation of methylated cell lines before and after treatment of demethylating agent 5-Aza-2＇-deoxycytidine （5-ADC） was examined with 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyltetrazolium bromide （MTT） assay in vivo. Results： Compared with the control, the expression of p16INK4A mRNA decreased significantly or absolutely defaulted in 10 of 18 （55.56%） ovarian cancer specimens and 71.4% （5/7） ovarian cancer cell lines （P〈0.05）, and the expression of p16INK4A protein also decreased （P〈0.05）. The decrease of p16INK4A was due, in part, to p16INK4A methylation, which was found in the first exon of three cell lines and six ovarian cancer specimens and the rate was 42.86% and 33.33% in ovarian cancer cell lines and specimens respectively. All the methylated cells and tissues showed expression defect of p16INK4A, but the treatment of 5-ADC reactivated the expression of p16INK4A in methylated cells and decreased the proliferation of tumor cells in vitro and in vivo. Conclusion： The expression defect of p16INK4A gene possibly has an important role in the development of ovarian cancer, and this alteration is due, in part, to the methylation of the first exon in p16INK4A.

Cloning and Expression Analysis of a Human Putative Tumor Suppressor Gene Homologue from Rice

A gene homologous to the human Putative tumor suppressor gone QM, designated OSQM1, was isolated from rice (Oryza sativa L.) genomic DNA library using through homology screening. It contained 4 exons and 3 introns, encoding a protein of 219 amino acids with 46 basic amino acids, leading to a high isoelectric point of 11.02. Homology search showed that this gene existed in eukaryotes and highly conserved throughout eukaryotes, suggesting an essential role of this gene. Northern Not analysis showed that it was expressed in various rice organs, but at lower level in developing flower and callus tissue than in other vegetative organs. Its expression levels in roots and leaves were influenced by different environmental factors.

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.

Roles of TGFβ in metastasis

The TGFβ signaling pathway is conserved from flies to humans and has been shown to regulate such diverse pro- cesses as cell proliferation, differentiation, motility, adhesion, organization, and programmed cell death. Both in vitro and in vivo experiments suggest that TGF[~ can utilize these varied programs to promote cancer metastasis through its effects on the tumor microenvironment, enhanced invasive properties, and inhibition of immune cell function. Recent clinical evidence demonstrating a link between TGFβ signaling and cancer progression is fostering interest in this signaling pathway as a therapeutic target. Anti-TGFβ therapies are currently being developed and tested in pre- clinical studies. However, targeting TGFβ carries a substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. Additionally, clinical and experimental results show that TGFβ has diverse and often conflicting roles in tumor progression even within the same tumor types. The development of TGFβ inhibitors for clinical use will require a deeper understanding of TGFβ signaling, its consequences, and the contexts in which it acts.

Suppression of cell growth and invasion by miR-205 in breast cancer

MicroRNAs （miRNAs） are endogenous, small, non-coding RNAs, which are capable of silencing gene expression at the post-transcriptional level. In this study, we report that miR-205 is significantly underexpressed in breast tumor compared to the matched normal breast tissue. Similarly, breast cancer cell lines, including MCF-7 and MDA-MB- 231, express a lower level miR-205 than the non-malignant MCF-10A cells. Of interest, ectopic expression of miR-205 significantly inhibits cell proliferation and anchorage independent growth, as well as cell invasion. Furthermore, miR- 205 was shown to suppress lung metastasis in an animal model. Finally, western blot combined with the luciferase reporter assays demonstrate that ErbB3 and vascular endothelial growth factor A （VEGF-A） are direct targets for miR-205, and this miR-205-mediated suppression is likely through the direct interaction with the putative miR-205 binding site in the 3＇-untranslated region （3＇-UTR） of ErbB3 and VEGF-A. Together, these results suggest that miR- 205 is a tumor suppressor in breast cancer.

Loss of heterozygosity on 10q23.3 and mutation of tumor suppressor gene PTEN in gastric cancer and precancerous lesions

AIM: To investigate the loss of heterozygosity (LOH) and mutation of tumor suppressor gene PTEN in gastric cancer and precancerous lesions. METHODS: Thirty cases of normal gastric mucosa, advanced and early stage gastric cancer, intestinal metaplasia, atrophic gastritis, and atypical hyperplasia were analyzed for PTEN LOH and mutations within the entire coding region of PTEN gene by PCR-SSCP denaturing PAGE gel electrophoresis, and PTEN mutation was detected by PCR-SSCP sequencing followed by silver staining. RESULTS: LOH rate found in respectively atrophic gastritis was 10% (3/30), intestinal metaplasia 10% (3/30), atypical hyperplasia 13.3% (4/30), early stage gastric cancer 20% (6/30), and advanced stage gastric cancer 33.3% (9/30), None of the precancerous lesions and early stage gastric cancer showed PTEN mutations, but 10% (3/30) of the advanced stage gastric cancers, which were all positive for LOH, showed PTEN mutation. CONCLUSION: LOH of PTEN gene appears in precancerous lesions, and PTEN mutations are restricted to advanced gastric cancer, LOH and mutation of PTEN gene are closely related to the infiltration and metastasis of gastric cancer.

Analysis of metastasis suppressing function of E-cadherin in gastric cancer cells by RNAi

AIM: To study the effect of inhibited E-cadherin expression on invasion of cancer cells.METHODS: We designed the nucleotide sequence of siRNA corresponding to 5' non-coding and coding sequence of E-cadherin. 21-nucleotide dssiRNA was synthesized by in vitro transcription with Ambion Silencer TM siRNA Construction Kit. siRNA was transfected into gastric cancer MKN45 using TransMessenger transfection Kit. RT-PCR and immunofluorescent assay were used to investigate the inhibition of the expression of mutated Ecadherin. Invasive ability of cancer cells was determined by Transwell assay.RESULTS: The synthesis of E-cadherin mRNA rather than protein expression was suppressed dramatically 7 d after interference. Decreased protein expression was observed on d 10 after interference. On d 11, invasion ability was enhanced significantly.CONCLUSION: siRNA targeted at non-coding and coding sequence of E-cadherin showed significant inhibition on mRNA and protein expression. Inhibited E-cadherin expression results in increased invasion ability of cancer cells.

Inactivation of RASSF1A, the tumor suppressor gene at 3p21.3 in extrahepatic cholangiocarcinoma

AIM: To evaluate the genetic and epigenetic inactivation mechanism of the RASSF1A tumor suppressor gene at 3p21.3 in extrahepatic cholangiocarcinoma. METHODS: RT-PCR was used to investigate the transcriptional expressing and re-expression of RASSFIA. RASSFIA mutation was analyzed with SSCP and selective sequencing. PCR was performed to detect the loss of heterozygosity (LOH) at the region of chromosome 3p21.3. Genomic DNA were modificated bisulfite and the frequency of methylation of CpG islands in RASSFIA promoter were evaluated by methylation specific PCR (MS-PCR). RESULTS: In all 48 samples and one cell lines of extrahepatic cholangiocarcinoma, the RASSFIA mutation is rare (6.12%, 3/49), 33 samples (68.75%) and QBC-939 cell lines (X2= 14.270, P= 0.001<0.01) showed RASSFIA express inactivation with LOH at microsatellite loci D3S4604. Among these 33 samples and QBC-939, 28 of 33 (84.85%) tumor samples and 1 cell lines were methylated for majority of 16 CpGs, the average frequency is 73.42%. CONCLUSION: The data we present suggest that RASSFIA which we have been searching for at 3p21.3 may be one of the key tumor suppressor gene and play an important role in the pathogenesis of extrahepatic cholangiocarcinoma, and the promoter methylation and allelic loss are the major mechanism for inactivation of RASSFIA.

Genetic and epigenetic changes associated with cholangiocarcinoma:From DNA methylation to microRNAs

Cholangiocarcinomas are malignant epithelial liver tumors arising from the intra- and extra-hepatic bile ducts. Little is known about the molecular development of this disease, and very few effective treatment options are available. Thus, prognosis is poor. Genetic and epigenetic changes play an integral role in the neoplastic transformation of human cells to their malignant counterparts. This review summarizes some of the more prevalent genetic alterations （by microRNA expression） and epigenetic changes （hypermethylation of specific gene promoters） that are thought to contribute to the carcinogenic process in cholancliocarcinoma.

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.

Inhibitory effect of tumor suppressor p33^(ING1b) and its synergy with p53 gene in hepatocellular carcinoma

AIM: To investigate the inhibitory effect of tumor suppressor p33ING1b and its synergy with p53 gene in hepatocellular carcinoma (HCC).METHODS: Recombinant sense and antisense p33ING1b plasmids were transfected into hepatoma cell line HepG2 with lipofectamine. Apoptosis, G0/G1 arrest, cell growth rate and cloning efficiency in soft agar of HepG2 were analyzed after transfection. In three hepatoma cell lineswith different endogenous p53 gene expressions, the synergistic effect of p33ING1b with p53 was analyzed by flow cytometry and luciferase assay was performed to detect the activation of p53 downstream gene p21WAF1/CIP1. In addition, the expression and mutation rates of p33ING1b in HCC tissues were measured by immunohistochemistry and polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP).RESULTS: Overexpression of p33ING1b inhibited cell growth of HepG2, induced more apoptosis and protected cells from growth in soft agar. Combined transfer of p33ING1b and p53 gene promoted hepatoma cell apoptosis, G0/G1 arrest and elevated expression of p21WAF1/CIP1. Immunostaining results showed co-localized P33ING1b with P53 protein in HCC tissues and there was a significant relation between protein expression rates of these two genes (P＜0.01).Among 28 HCC samples, p33ING1b presented a low gene mutation rate (7.1%).CONCLUSION: p33ING1b collaborates with p53 in cell growth inhibition, cell cycle arrest and apoptosis in HCC. Loss or inactivation of p33ING1b normal function may be an important mechanism for the development of HCC retaining wildtype p53.

Tumor suppressor and hepatocellular carcinoma

A few signaling pathways are driving the growth of hepatocellular carcinoma.Each of these pathways possesses negative regulators.These enzymes,which normally suppress unchecked cell proliferation,are circumvented in the oncogenic process,either the overactivity of oncogenes is sufficient to annihilate the activity of tumor suppressors or tumor suppressors have been rendered ineffective.The loss of several key tumor suppressors has been described in hepatocellular carcinoma.Here,we systematically review the evidence implicating tumor suppressors in the development of hepatocellular carcinoma.

Expression of von Hippel-Lindau tumor suppressor and tumor-associated carbonic anhydrases IX and XII in normal and neoplastic colorectal mucosa

AIM:To analyze possible relationships between CA IX/ CA XII and pVHL expression in normal and neoplastic colorectal mucosa. METHODS: Immunohistochemical staining of 42 tissue specimens obtained from 17 cancer patients was performed to evaluate the distribution and semi-quantitatively assess the levels of CA IX, CA XII and pVHL. VHL mRNAs from 14 fresh-frozen tumors was amplified by RT-PCR and subjected to sequencing. CA9 and G412mRNA levels were analyzed by semi-quantitative RT-PCR in comparison with VEGFas an indicator of hypoxia that uncouples the pVHL control. RESULTS: Tumor tissues were associated with a borderline increase of CA IX staining signal and slight but significant decrease of CA XII immunoreactivity, whereas no association was found for pVHL. Sequence analysis of RT-PCR-amplified VHL mRNAs revealed no deletions/ mutations, suggesting that they were VHL-competent. We did not observe any correlation between pVHL and CA IX/CA XII proteins as well as between MEGFand CA9 mRNAs, but the tumor-associated changes in mRNA levels of VEGFand CA12 showed a significant inverse relationship. CONCLUSION: Our results indicate that CA9and CA12 are regulated by different intratumoral factors and that lack of apparent relationship between the levels of CA IX/CA XII and pVHL cannot be fully assigned to uncoupling of negative regulatory function of pVHL by tumor hypoxia signified by induced VEGF transcription. The interplay between the functional pVHL and CA IX/CA XII in colorectal tumors seems rather complex and is not evident merely at the expression levels.

Science Letters:IGFBP7 plays a potential tumor suppressor role against colorectal carcinogenesis with its expression associated with DNA hypomethylation of exon 1

Insulin-like growth factor binding-protein-7 （IGFBP7） was obtained from our previous colonic adenocarcinoma （CRC） and normal mucosa suppression subtraction hybridization （SSH） cDNA libraries. By RT-PCR and immunohistochemistry, we found that IGFBP7 was overexpressed in CRC tissue compared to normal tissue. However, our in vitro experiments performed in 10 CRC cell lines showed that IGFBP7 expressed only in SW480 and Caco2 cell lines, which implied an underlying reversible regulatory mechanism. Using methylation-specific PCR （MSP） and bisulfite sodium PCR （BSP）, we found that its expression was associated with DNA hypomethylation of exonl. This was further supported by the in vitro study which showed restored IGFBP7 expression after demethylation agent 5-aza-2＇-deoxycytidine treatment. Correlation analysis between IGFBP7 expression and prognosis indicated that overexpression of IGFBP7 in CRC tissue correlated with favourable survival. Investigation of the functional role of IGFBP7 through transfection studies showed that IGFBP7 protein could inhibit growth rate, decrease colony formation activity, and induce apoptosis in RKO and SW620 cells, suggesting it a potential tumor suppressor protein in colorectal carcinogenesis. In conclusion, our study clearly demonstrated that IGFBP7 plays a potential tumor suppressor role against colorectal carcinogenesis and its expression is associated with DNA hypomethylation of exon 1.

PTEN： a default gate-keeping tumor suppressor with a versatile tail

The tumor suppressor PTEN controls a variety of biological processes including cell proliferation, growth, migration, and death. As a master cellular regulator, PTEN itself is also subjected to deliberated regulation to ensure its proper function. Defects in PTEN regulation have a profound impact on carcinogenesis. In this review, we briefly discuss recent advances concerning PTEN regulation and how such knowledge facilitates our understanding and further exploration of PTEN biology. The carboxyl-tail of PTEN, which appears to be associated with multiple types of posttranslational regulation, will be under detailed scrutiny. Further, a comparative analysis of PTEN and p53 suggests while p53 needs to be activated to suppress tumorigenesis （a dormant gatekeeper）, PTEN is probably a constitutive surveillant against cancer development, thus a default gatekeeper.

Serrated polyposis syndrome:Molecular,pathological and clinical aspects

Hyperplastic polyps have traditionally been considered not to have malignant potential.New pathological classification of serrated polyps and recent discoveries about the serrated pathway of carcinogenesis have revolutionized the concepts and revitalized the research in this area.Until recently,it has been thought that most colorectal cancers arise from conventional adenomas via the traditional tumor suppressor pathway initiated by a mutation of the APC gene,but it has been found thatthis pathway accounts for only approximately 70%-80% of colorectal cancer(CRC)cases.The majority of the remaining colorectal cancer cases follow an alternative pathway leading to CpG island methylator phenotype carcinoma with BRAF mutation and with or without microsatellite instability.The mechanism of carcinomas arising from this alternative pathway seems to begin with an activating mutation of the BRAF oncogene.Serrated polyposis syndrome is a relatively rare condition characterized by multiple and/or large serrated polyps of the colon.Clinical characteristics,etiology and relationship of serrated polyposis syndrome to CRC have not been clarified yet.Patients with this syndrome show a high risk of CRC and both sporadic and hereditary cases have been described.Clinical criteria have been used for diagnosis and frequent colonoscopy surveillance should be performed in order to prevent colorectal cancer.In this review,we try to gather new insights into the molecular pathogenesis of serrated polyps in order to understand their possible clinical implications and to make an approach to the management of this syndrome.

Mouse models of pancreatic cancer

Pancreatic cancer is one of the most lethal of human malignancies ranking 4th among cancer-related death in the western world and in the United States,and potent therapeutic options are lacking.Although during the last few years there have been important advances in the understanding of the molecular events responsible for the development of pancreatic cancer,currently specific mechanisms of treatment resistance remain poorly understood and new effective systemic drugs need to be developed and probed.In vivo models to study pancreatic cancer and approach this issue remain limited and present different molecular features that must be considered in the studies depending on the purpose to fit special research themes.In the last few years,several genetically engineered mouse models of pancreatic exocrine neoplasia have been developed.These models mimic the disease as they reproduce genetic alterations implicated in the progression of pancreatic cancer.Genetic alterations such as activating mutations in KRas,or TGFb and/or inactivation of tumoral suppressors such as p53,INK4A/ARF BRCA2 and Smad4 are the most common drivers to pancreatic carcinogenesis and have been used to create transgenic mice.These mouse models have a spectrum of pathologic changes,from pancreatic intraepithelial neoplasia to lesions that progress histologically culminating in fully invasive and metastatic disease and represent the most useful preclinical model system.These models can characterize the cellular and molecular pathology of pancreatic neoplasia and cancer and constitute the best tool to investigate new therapeutic approaches,chemopreventive and/or anticancer treatments.Here,we review and update the current mouse models that reproduce different stages of human pancreatic ductal adenocarcinoma and will have clinical relevance in future pancreatic cancer developments.

New insights into p53 activation

The tumor suppressor p53 is a multifunctional, highly regulated, and promoter-specific transcriptional factor that is uniquely sensitive to DNA damage and cellular stress signaling. The mechanisms by which p53 directs a damaged cell down either a cell growth arrest or an apoptotic pathway remain poorly understood. Evidence suggests that the in vivo functions of p53 seem to balance the cell-fate choice with the type and severity of damage that occurs. The concept of antirepression, or inhibition of factors that normally keep p53 at bay, may help explain the physiological mechanisms for p53 activation. These factors also provide novel chemotherapeutic targets for the reactivation of p53 in tumors harboring a wild-type copy of the gene.