维甲酸对HeLa细胞间隙连接蛋白基因cx43表达的调节作用

目的：探讨分化诱导剂维甲对肿瘤抑制基因－细胞间隙连接蛋白基因cx４３在人子宫颈癌细胞系ＨeＬa中表达的调节作用。方法：应用核酸原位杂交、流式细胞仪、Ｗesten blot及Ｌucifer Ｙellow划痕标记荧光传输技术,研究维甲酸作用对ＨeＬa细胞cx４３mＲＮＡ及其蛋白表达,以及对ＨeＬa细胞生长和通迅功能找调节作用。结果：ＨeＬa细胞经维甲酸处理后,原位杂交显示,ＨeＬa细胞cx４３ mＲＮＡ水平上调;流式细胞仪分析,Ｃx４３蛋白     

Aberrant expression of gap junction gene in primary human hepatocellular carcinomas: increased expression of cardiac-type gap junction gene connexin 43

The expression of connexin 32 (the major liver gap junction protein) and connexin 43 (the major cardiac gap junction protein) was examined in six surgically removed human hepatocellular carcinoma tissues and the surrounding nontumorous livers using specific rat connexin probes. No decrease in connexin 32 mRNA expression was found in carcinomas compared with the surrounding nontumorous tissue. Morphometrical analysis also showed that in most of the carcinomas the number of gap junction spots stained with connexin 32 antibody was not less than that in the surrounding livers. These results are in striking contrast to the significant reductions in connexin 32 mRNA and protein expression observed in rat primary liver tumors induced by chemicals. On the other hand, all of the six human hepatocellular carcinomas exhibited elevated levels of connexin 43 mRNA, which was expressed at a very low level in the surrounding nontumorous livers. These carcinomas exhibited no detectable amplification of the connexin 43 gene. The present study suggests that gap junctional intercellular communication is altered in human hepatocellular carcinomas by molecular mechanisms different from those in rat hepatocarcinogenesis.     

Aberrant expression and localization of connexin43 and connexin30 in a rat glioma cell line

Gap junctions are cellular structures which permit direct exchanges of small molecules from cytoplasm to cytoplasm in most of the cells of metazoan organisms. For four decades, it has been observed that the inhibition of this type of intercellular communication is often associated with tumorigenesis. The assumption that loss of homeostasis which characterizes tumor growth could be a consequence of a lack of gap junctional intercellular communication (GJIC) has been reinforced by strategies able to reinduce both GJIC and normalization of the phenotype. So far, no molecular data may explain clearly how gap junctions can regulate cell proliferation. It has been argued that the gap-junction tumor suppressive effect may depend specifically on the connexin type which is expressed. For instance, the transfection of connexin30 (Cx30), a gap junction protein, has been previously associated with a slower growth of rat glioma cells (9L cells). Here, we show that these cells do communicate less compared to the Cx43-expressing parental cells even if the Cx30-transfected cells do express more Cx43. This result was related to the cytoplasmic distribution of Cx43 and a nuclear localization of both the Cx30 and a 20-kDa fragment corresponding to a Cx43 signal. According to these data, it seems that cell growth regulation may depend more on the behavior of connexins than the simple establishment of GJIC.     

肝细胞癌中间隙连接蛋白Cx43和E-钙粘附素的表达

目的 研究间隙连接蛋白(connexin43 Cx43)和E-钙粘附素(E-cadherin)在肝细胞癌(hepatocelluar carcinoma, HCC)中的表达及其关系,探讨它们在HCC发生和发展中的作用.方法采用免疫组化技术检测47例HCC中间隙连接蛋白Cx43、E-cadherin的表达.结果 Cx43、E-cadherin阳性率分别为42.55%、46.81%.随着疾病进展(TNM分期),Cx43阳性率降低.肝硬化组Cx43阳性率明显低于无肝硬化组(χ2＝4.7135,P＝0.03).肝内血管瘤栓组E-cadherin的阳性率明显高于无肝内血管瘤栓组(P＝0.028).Cx43、E-cadherin的阳性率在肿瘤大小、癌组织分化程度组无显著差异(P＞0.05).Spearman相关分析未发现Cx43与E-cadherin存在显著相关.结论 Cx43、E-cadherin蛋白的异常表达可能在HCC的发生、进展和肝内转移中发挥作用.检测二者的表达有助于综合判断HCC的生物学行为.     

Gap junction proteins connexin32 and connexin43 partially acquire growth-suppressive function in HeLa cells by deletion of their C-terminal tails.

Our laboratory has previously reported that transfection of a connexin26 (Cx26) gene, but not connexin40 nor connexin43 (Cx43), into HeLa cells expressing no detectable level of connexins suppressed the tumorigenic phenotype of the HeLa cells both in vitro and in vivo, although all of these connexins induced gap junctional intercellular communication in HeLa cells to a similar extent. The most remarkable structural difference between connexin proteins is the length of the C-terminal cytoplasmic tail, Cx26 having almost no tail, while Cx43 and connexin32 (Cx32) have long and intermediate ones, respectively. When Cx32 and Cx43 lose their C-terminal tails, they seem to resemble Cx26 in structure. To examine whether such truncated connexins become tumor suppressive in HeLa cells, we introduced a stop codon into each of the Cx32 and Cx43 cDNAs to remove their C-terminal tails and transfected these constructs (DeltaCx) into HeLa cells. Both DeltaCx cDNAs induced GJIC as efficiently as the wild-type counterparts. Although none of the truncated connexins affected proliferation rate, the truncated Cx32 and Cx43 proteins suppressed anchorage-independent cell growth in soft agar. Furthermore, when the transfectants were injected into the backs of nude mice, tumor appearance was delayed by 7 days in animals given cells expressing truncated connexins, i.e. tumors became detectable on days 11 and 18 after injection of vector and DeltaCx transfectants, respectively. Although throughout these experiments the truncated connexins did not completely eliminate the tumorigenicity of HeLa cells, as Cx26 did, it was evident that deletion of the C-terminal tails gave both Cx32 and Cx43 a capacity for negative growth control, suggesting that the C-terminal tails of these two connexins function as a regulatory region for connexin-mediated growth control in HeLa cells.     

Connexin 43和E-cadherin在非小细胞肺癌中表达及相关性研究

背景与目的由连接蛋白(connexin，Cx)构成的细胞间隙连接(gapjunmion)对细胞的增殖和分化起着重要的调控作用，Cx表达下降将导致细胞恶化。上皮钙粘蛋白(E-cadherin)为上皮细胞与细胞之间及细咆与细胞外基质粘附的跨膜糖蛋白分子，其功能抑制或表达下降可使细胞间粘附能力下降，细胞易于分离。本研究旨在探讨连接蛋白43(Connexin 43，Cx43)和E—cadherin在非小细胞肺癌中的表达及两者的相互关系。方法采用免疫组织化学S—P法检测85例原发性非小细胞肺癌组织的Cx43和E—cadherin蛋白表达，并进行两者的相关性分析。结果Cx43和E—cadherin蛋白在非小细胞肺癌中表达显著下降．其下降程度与肺癌的细胞分化程度、pTNM分期和有无淋巴结转移均有密切关系，而与组织学分型无明显关系。Cx43和E—cadherin蛋白表达之间存在明显的相关性。结论Cx43和E—cadherin蛋白在非小细胞肺癌中表达显著下降，且两者存在着明显的相关性，可能是肺癌发生和发展过程中的共同事件。     

全反式维甲酸对激素非依赖性前列腺癌连接蛋白43表达的影响

目的:探讨全反式维甲酸(all-trans retinoic acid,ATRA)对激素非依赖性前列腺癌连接蛋白43(Cx43)表达的影响及其临床价值。方法:应用激素非依赖性前列腺癌细胞PC-3细胞建立荷前列腺癌裸鼠模型,分为ATRA治疗组(n=9)和对照组(n=9),半定量逆转录聚合酶链式反应(RT-PCR)和免疫组织化学法分别检测肿瘤组织中Cx43的表达,并动态观察肿瘤生长抑制情况。结果:与对照组比较,ATRA可以显著抑制肿瘤生长(P＜0．05)。RT-PCR检测结果提示,治疗组中Cx43 mRNA表达量为2．03±0．85,明显高于对照组的0．99±0．23(P＜0．05)。免疫组织化学法显示对照组肿瘤组织中Cx43蛋白表达微弱;而治疗组中表达量明显升高,以细胞膜上表达为主。结论:激素非依赖性前列腺癌组织中Cx43表达低下,ATRA可以提高其表达而抑制肿瘤的生长。     

Phosphorylation of connexin43 in cells containing mutant src oncogenes.

Disruption of gap junctional communication (measured by intercellular dye transfer) in cultured fibroblasts by pp60v-src is correlated with phosphorylation of the gap junction protein, connexin43 (cx43), on tyrosine. In this report, we examine the functional relevance of these observations by studying cx43 phosphorylation in cells containing kinase-active, non-myristylated pp60(2A527F) or pp60v-src temperature sensitive (ts) for transformation. Non-transformed cells expressing pp60(2A527F) transferred fluorescent dye at high levels and contained cx43 that was phosphorylated predominately on serine. In contrast, cells transformed by kinase-active, myristylated pp60(527F) did not transfer dye and contained cx43 proteins which were phosphorylated on serine and tyrosine. Additionally, activation of ts pp60v-src tyrosine kinase activity upon shift of cells to the permissive temperature was correlated with a rapid increase in the phosphorylated tyrosine content of cx43 proteins and loss of gap junctional communication. These combined results suggested that cx43 is a substrate of pp60v-src whose phosphorylation on tyrosine may be involved in the disruption of gap junctional communication observed in Rous sarcoma virus (RSV)-transformed cells.     

Increased susceptibility to urethane-induced lung tumors in mice with decreased expression of connexin43

Gap junction intercellular communication capacity and connexin expression are reportedly decreased in human lung cancer. The mechanisms by which connexins, the gap junction proteins, act as tumor suppressors are unclear. In order to understand the involvement of connexins in tumorigenesis, we analyzed the effect of the heterologous deletion of Gja1 [the connexin43 (Cx43) gene] on the development of lung adenomas in mice. Heterozygous (Cx43(+/-)) and wild-type mice (Cx43(+/+)) were treated or not with single doses of urethane at 15 and 17 days after birth. Twenty-five weeks later, both the number and size of nodules were increased in Cx43(+/-) mice as compared with Cx43(+/+) mice. Moreover, the lesions were histologically more aggressive in the heterozygous mice. However, no increase in spontaneous lesions was observed in the lungs of untreated Cx43(+/-) mice. Heterozygous mice effectively presented lower expression of Cx43 genes and decreased amounts of Cx43. In conclusion, our results indicate that deletion of one allele of the Cx43 gene clearly favors the carcinogenic effect of urethane administration and results in a higher susceptibility to lung adenoma formation in mice.     

Upregulation of gap junctional communication and connexin43 gene expression by carotenoids in human dermal fibroblasts but not in human keratinocytes

Consumption of dietary carotenoids has been statistically associated with decreased risk of cancer at several anatomic sites. In a model murine system of carcinogenesis (the 10T1/2 assay), we have previously shown that carotenoids can inhibit chemically and physically induced neoplastic transformation. This action is strongly correlated with the ability of carotenoids to increase gap-junctional communication (GJC) by induction of connexin43 (Cx43) gene expression. Here we extend these studies to human foreskin-derived dermal fibroblasts and keratinocytes. In fibroblasts, β-carotene and canthaxanthin at concentrations between 10^?5 and 3 × 10^?6 M were found to strongly enhance GJC in a dose- and time-dependent manner. This was accompanied by an increase in the number of immunofluorescent junctional plaques recognized by an anti-Cx43 antibody and by an increase in Cx43 protein level as determined by western blot analysis. No decrease in proliferation rates was detected by [H³]thymidine labeling. Human keratinocytes grown in monolayer culture did not respond to carotenoids in terms of GJC as measured by dye transfer, immunofluorescent analysis of Cx43 distribution, or Cx43 levels as measured by western blotting. Both cell types accumulated high levels of carotenoids. Because canthaxanthin, which has no known provitamin A activity in mammals, is as active in fibroblasts as is β-carotene, the carotenoid with the highest provitamin A activity, the induction of GJC and Cx43 expression by carotenoids in human dermal fibroblasts seems unrelated to their provitamin A status. The lack of response of keratinocytes suggests differences in regulation of Cx43 expression or in carotenoid processing. © 1995 Wiley-Liss Inc.     

Non-viral delivery of the connexin 43 gene with histone deacetylase inhibitor to human nasopharyngeal tumor cells enhances gene expression and inhibits in vivo tumor growth

Dysregulation of connexin expression is believed to have a role in carcinogenesis, because levels of connexin are reduced in various tumors. We examined the role of connexin 43 (Cx43) alone and combined with a histone deactylase (HDAC) inhibitor in tumor growth inhibition. The transfection of Cx43 plasmid DNA (pCMV-Cx43) into human nasopharyngeal cancer KB cells using folate-linked nanoparticles induced inhibition of cell growth. Cx43 induced a tumor suppressive effect via a gap junctional intercellular communication-independent mechanism. The transfection of pCMV- Cx43 along with an HDAC inhibitor, 4-phenylbutyrate (4-PB), enhanced Cx43 expression greatly in vitro, and inhibited significantly the tumor growth of KB cells and xenografts compared with that of pCMV-Cx43 alone. 4-PB induced increased expression of genes of DNA damage checkpoints and of apoptosis via the down-regulation of anti-apoptotic bcl-2 mRNA expression and up-regulation of the activity of the apoptosis-associated enzyme caspase-3/7. Thus, the amplified Cx43 expression by an antitumor agent, an HDAC inhibitor, may have great potential as a growth inhibitor for nasopharyngeal tumors.     

连接蛋白基因Cx43抑制胶质瘤细胞增殖及其机理的初步探讨

目的 探讨连接蛋白基因Cx43对胶质瘤细胞增殖的抑制及其可能的机理。方法 将含Cx43cDNA的质粒以脂质体介导转染Cx43表达缺失的人和鼠的恶性胶质瘤细胞,通过Northem杂交、原位杂交及免疫组化染色检测Cx43mRNA及蛋白表达;MTT法测定细胞增殖率;核仁组成区嗜银蛋白染色检测细胞增殖活性;TUNEL法检测细胞凋亡;划痕标记荧光染料示踪技术检测细胞间隙连接通讯(GJIC);Western杂交及免疫组化染色检测bFGF、PDGF、EGFR、IGF-I和IGFBP3的表达。结果 转染Cx43基因的胶质瘤细胞增殖下降,GJIC恢复,同时伴有bFGF、PDGF、IGF-I和IGFBP3表达下降,而EGFR表达和细胞凋亡则无改变。结论 Cx43基因可能通过恢复GJIC功能及抑制某些重要生长因子的自分泌,实现对胶质瘤细胞增殖的抑制。     

急性白血病患者骨髓间隙连接蛋白43的表达及其与耐药的相关性研究

 【摘要】　目的　探讨急性白血病（AL）患者骨髓细胞中间隙连接蛋白43（Cx43）、P-糖蛋白（P-gp）及环氧合酶2（COX-2）基因表达水平及其与AL病程、预后和耐药的关系。方法　77例不同病期AL患者,其中初治36例,完全缓解20例,复发20例,同时以20例异体造血干细胞移植供体及非血液系统恶性病患者为对照。采用SYBR Green实时定量反转录聚合酶链反应（SYBR-RT-PCR）技术,检测骨髓单个核细胞中Cx43、P-gp、COX-2 mRNA的表达,并对37例初治患者进行动态随访。结果　AL初治组Cx43、P-gp、COX-2 mRNA的表达分别为0.52±0.57、1.42±1.06、1.14±0.95,复发组分别为0.20±0.40、2.29±1.11、1.69±0.81,完全缓解组分别为0.95±0.37、0.93±0.73、0.79±0.58,对照组分别为1.16±0.67、0.86±0.63、0.61±0.57。初治、复发AL患者Cx43 mRNA表达水平较对照组及完全缓解组低,差异均有统计学意义（初治组分别P＝0.001、0.005;复发组均P<0.001）;完全缓解组Cx43 mRNA表水平与对照组相比,差异无统计学意义（P＝0.185）。AL患者骨髓细胞液中Cx43 mRNA与P-gp和COX-2 mRNA表达呈负相关,且初治组、完全缓解组及复发组表达均呈负相关（与P-gp r值分别为-0.471、-0.362、-0.526;与COX-2 r值分别为-0.479、-0.344、-0.471）。36例AL初治患者随访4个月,死亡8例,生存28例,死亡患者Cx43 mRNA表达低于生存患者,差异有统计学意义（t＝2.16,P＝0.042）。结论　初治、复发难治AL患者骨髓中Cx43 mRNA的表达下调,同时多药耐药基因P-gp、COX-2 mRNA的表达上调;Cx43过度表达是预后良好因素,Cx43与AL的疗效、预后及化疗耐药密切相关。     

Cx43基因启动子去甲基化与乳腺癌MDA-MB231细胞上皮间质转换的相关性研究

目的:探讨乳腺癌细胞中连接蛋白43(Cx43)基因启动子甲基化与乳腺癌上皮间质转化(EMT)的关系.方法:甲基化PCR检测Cx43启动子甲基化的频度;5-氮杂脱氧胞苷(5-Aza-Dc)培养乳腺癌MD-MBA-231细胞后,反转录PCR(RT-PCR) 乳腺癌细胞中Cx43 Mrna,免疫荧光、蛋白质印迹法检测E-cadherin、波蛋白(vimentin)及Cx43蛋白表达,甲基化PCR检测启动子甲基化的变化.结果:在应用5-Aza-Dc处理前,MD-MBA-231Cx43基因呈甲基化状态,将4.0 μmol/L的5-Aza-Dc作用48 h后,乳腺癌细胞Cx43基因甲基化逆转;Cx43 Mrna表达水平增加,为对照组的6.5倍.蛋白质印迹检测结果显示,Cx43蛋白相对灰度值为4.3±0.2,明显高于对照组.处理组细胞E-cadherin表达增加,vimentin表达下调.结论:5-Aza-Dc能逆转乳腺癌细胞MD-MBA-231的Cx43基因异常甲基化,促进Cx43基因的再表达,在一定程度上逆转乳腺癌MDA-MB231细胞EMT.     

Suberoylanilide hydroxamic acid enhances gap junctional intercellular communication via acetylation of histone containing connexin 43 gene locus

A histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), induces apoptosis in neoplastic cells, but its effect on gap junctional intercellular communication in relation to apoptosis was unclear. Therefore, we carried out a comparative study of the effects of two HDAC inhibitors, SAHA and trichostatin-A, on gap junctional intercellular communication in nonmalignant human peritoneal mesothelial cells (HPMC) and tumorigenic ras oncogene-transformed rat liver epithelial cells (WB-ras) that showed a significantly lower level of gap junctional intercellular communication than did HPMC. Gap junctional intercellular communication was assessed by recovery rate of fluorescence recovery after photobleaching. Treatment of HPMC with SAHA at nanomolar concentrations caused a dose-dependent increase of recovery rate without inducing apoptosis. This effect was accompanied by enhanced connexin 43 (Cx43) mRNA and protein expression and increased presence of Cx43 protein on cell membrane. Trichostatin-A induced apoptosis in HPMC but was less potent than SAHA in enhancing the recovery rate. In contrast, treatment of WB-ras cells with SAHA or trichostatin-A induced apoptosis at low concentrations, in spite of smaller increases in recovery rate, Cx43 mRNA, and protein than in HPMC. Chromatin immunoprecipitation analysis revealed that SAHA enhanced acetylated histones H3 and H4 in the chromatin fragments associated with Cx43 gene in HPMC. These results indicate that SAHA at low concentrations selectively up-regulates Cx43 expression in normal human cells without induction of apoptosis, as a result of histone acetylation in selective chromatin fragments, in contrast to the apoptotic effect observed in tumorigenic WB-ras cells. These results support a cancer therapeutic and preventive role for specific HDAC inhibitors.     

In vivo growth of C6 glioma cells transfected with connexin43 cDNA.

In order to examine the possible role of intercellular communication via gap junctions in the control of tumor growth, we have transfected C6 glioma cells with connexin43 cDNA. We obtained several clones with variable expression of connexin43. The growth rate of these clones in culture was inversely related to the degree of expression of the transfected cDNA. To examine the growth of these transfected cells in vivo, cells were grown in spinner culture flasks to form spheroids 250-300 microns in diameter. Spheroids of nontransfected C6 cells produced large gliomas. Immunohistochemical and in situ hybridization analyses revealed relatively high levels of connexin43 protein and mRNA in the host tissue, while little of this protein was detected in the glioma. In contrast, spheroids of connexin43-transfected cells grew more slowly and exhibited elevated levels of connexin43 protein and mRNA. These findings suggest that the expression of connexin43 may be associated with the control of brain tumor growth in vivo.