Smad4/Smad7 balance: A role of tumorigenesis in gastric cancer

Smad signaling pathway plays an important role in tumorigenesis and progression in cancer (Halder, S.K., Rachakonda, G., Deane, N.G., Datta, P.K., 2008. Smad7 induces hepatic metastasis in colorectal cancer. Br. J. Cancer 99, 957-965). The protein level of Smad is associated with growth, inhibition, and metastasis in different cancers. It is unclear if the differentiation, metastasis and apoptosis are reduced by Smad expression pattern in gastric cancer. To determine the effect of Smad on gastric cancer cells, we investigated the relationship of Smad4/Smad7 expression, and differentiation, metastasis, and apoptosis in different gastric cancer. The results show that Smad4 expression in the gastric cancer tissue was dramatically lower than that in the peritumoral tissue. A lower expression of Samd4 was significantly lower in the poorly differentiated tissue than that in the well and middle differentiated tissues (P < 0.01). In contrast, Smad7 expression in gastric cancer tissues was significantly higher than that in the peritumoral tissue. Smad7 was overexpressed in poorly differentiated tissue, also higher than those in the middle, and well differentiated tissues (P < 0.05). The Smad4 or Smad7 expression obviously related with the lymphatic metastasis in gastric cancer. There were 45 cases with lymphatic metastasis in all 78 patients. Smad4 expression in the cases with lymphatic metastasis was lower than the cases without metastasis (P < 0.01), whereas Smad7 expression in the cases with lymphatic metastasis was much higher than the case without metastasis (P < 0.01). To better understand the mechanisms involved in tumorigenesis of gastric cancer, we established SGC7901 gastric cancer cell lines transduced with Smad4 or Smad7 plasmid DNA. Apoptosis and survival of cancer cells was induced after Smad4 and Smad7 transduction. This effect is concentration and time dependent. Thus, this study provides a mechanism by which a balance between Smad4 and Smad7 in human gastric cancer is critical for differentiation, metastasis, and apoptosis of tumor cells.     

Smad7而非Smad6基因可抑制TGF-β诱导肾小管上皮-间充质转分化

目的:观察Smad6和Smad7基因能否抑制TGF-β诱导肾小管上皮-间充质转分化.方法:构建产生表达Smad6和Smad7基因的无辅毒腺相关病毒载体, 再将病毒颗粒分别转染入人肾小管上皮细胞(HKC), 细胞随机分为正常对照、 TGF-β1组、 Smad7 组、 LacZ组、 TGF-β1 Smad7或Smad6组、 TGF-β1 LacZ组.10 μg/L TGF-β1添加入培养液孵育15、 30、 60、 120 min和3 d.Western blot测定TGF-β1和Smad6或Smad7基因转染对细胞p-Smad2、 E-cadherin、α-smooth muscle actin(α-SMA)表达的影响, ELISA法测定培养上清羟脯氨酸的含量的变化, 倒置显微镜观察细胞形态变化.结果:与未加TGF-β1细胞相比, 添加TGF-β1后15、 30、 60、 120 min胞内Smad2磷酸化水平明显增加, 30 min时表现最大.10 μg/L TGF-β1与HKC孵育72 h后, 细胞α-SMA和羟脯氨酸量合成增加, E-cadherin表达减少;细胞形态变长, 呈纺锤状细胞, 失去鹅卵石样的形状.Smad7基因转染可抑制TGF-β1诱导Smad2磷酸化, 抑制细胞α-SMA和羟脯氨酸合成, 增加E-cadherin表达, 维持培养细胞的上皮样形态, 相反, Smad6没有这样的作用.结论:Smad7而不是Smad6基因转染能抑制TGF-β1诱导肾小管上皮-间充质转分化, 这些作用可能与Smad7阻断Smad2磷酸化有关.     

人Smad7腺病毒表达载体的构建及体外表达

用DNA直接克隆连接的方法,构建人Smad7腺病毒重组质粒,再用293细胞包装。重组腺病毒经扩增、纯化后,感染体外培养的瘢痕疙瘩成纤维细胞,用RT-PCR方法检测细胞中人Smad7mRNA的转录。经酶切和PCR鉴定证实了人Smad7重组腺病毒质粒构建成功,RT-PCR证实瘢痕疙瘩细胞中有腺病毒载体介导的Smad7mRNA的过度表达。结果证实构建的人Smad7腺病毒表达载体可在体外细胞中表达,并可进一步应用于瘢痕疙瘩基因治疗方面的研究。     

泛素蛋白酶体途径对高糖刺激的肾系膜细胞Smad7表达的影响

目的:观察不同浓度高糖刺激后大鼠肾系膜细胞胞内Smad泛素化调节因子－Smurf2和Smad7 的表达,并以蛋白酶体特异性抑制剂MG132作为阻断剂,探讨泛素化降解在Smad信号中的作用。方法：将体外培养的大鼠肾小球系膜细胞分别设正常对照组（葡萄糖浓度5.6 mmol/L）、20 mmol/L高糖组、30 mmol/L高糖组、30 mmol/L高糖加蛋白酶体抑制剂MG132组等。用细胞免疫荧光染色法及激光共聚焦显微镜检测各组细胞泛素连接酶Smurf2及Smad7的表达。结果：(1)正常组细胞Smurf2蛋白表达较弱（25.93±3.35）,Smad7蛋白表达较强（64.09±7.43）。(2)高糖组Smurf2表达较正常组增强(P<0.05),呈浓度依赖性,荧光灰度值分别为20 mmol/L高糖组（56.99±7.00）、30 mmol/L高糖组（96.36±9.19）;Smad7表达减弱(P<0.05),呈浓度依赖性,分别为20 mmol/L高糖组（45.33±6.67）、30 mmol/L高糖组（30.20±4.41）。（3）30 mmol/L高糖组加入MG132后,Smurf2表达减弱、Smad7表达增强。结论：（1）高糖可诱导肾系膜细胞Smurf2表达增强,Smad7表达减弱。(2)MG132可阻止高糖所导致的上述变化。提示泛素－蛋白酶体途径参与了糖尿病肾病Smad通路的信号调节。     

上调表达Smad7显著抑制TGF-β介导的大鼠腹膜间皮细胞Smad2的表达

目的： 探讨外源性转入并上调表达抑制性信号蛋白Smad7对TGF-β₁作用下大鼠腹膜间皮细胞Smad2表达的影响。 方法： 通过脂质体介导的方法，将表达Smad7的重组质粒（PCDNA3-Smad7）转染培养的大鼠腹膜间皮细胞，分别培养于不同浓度TGF-β₁培养液(0、1.25、2.5和10 μg/L)，用RT-PCR及Western blotting的方法检测不同时间（0、5、15、30、60和120 min）Smad2、Smad7表达的水平。 结果： 正常间皮细胞Smad2 mRNA和蛋白在TGF-β₁刺激后5 min开始表达，呈时间依赖性，在30 min达到高峰，而后逐渐减弱；Smad7 mRNA和蛋白也在TGF-β₁刺激后5 min可见表达，但此后逐渐减弱，30 min达到最低，60 min又开始逐渐增强。Smad2 和Smad7 mRNA和蛋白，随TGF-β₁浓度的增高而表达增强。转染后大鼠腹膜间皮细胞可见Smad7 mRNA和蛋白表达显著上调，并可持续高表达。转染后的腹膜间皮细胞在TGF-β₁刺激下，Smad2 mRNA及蛋白的表达均低下，刺激0、5、15、30、60 和120 min后Smad2 mRNA表达分别低33%、56%、67%、71%、63%和57%（P<0.05）。Smad2蛋白表达分别低78%、89%、89%、88%和76%（P<0.05）。 结论： 上调表达抑制性信号蛋白Smad7可显著抑制腹膜间皮细胞中受体调控信号蛋白Smad2的表达和活性，提示Smad7可能对TGF-β₁起反向调控作用。     

Smad2/3与Smad7在大鼠化疗性卵巢早衰卵泡中的表达和意义

目的 探讨顺铂对大鼠卵巢结构和功能损伤的影响及其可能的分子机制。方法 3月龄SD 雌性大鼠随机分为对照组（C组,5只）和化疗组（H组,5只）。H组给予每只大鼠腹腔注射顺铂2 mg/（kg.d）,C组给予腹腔注射等体积生理盐水,连续注射7 d后检测大鼠卵巢指数（卵巢湿重/体重）;酶联免疫吸附法检测血清雌二醇（E₂）和促卵泡刺激素（FSH）水平;苏木素-伊红染色观察卵泡发育并计数各级卵泡;免疫组织化学和Real-time PCR法检测各组Smad2、磷酸化Smad2（p-Smad2）、Smad3、磷酸化Smad3（p-Smad3）、Smad4和Smad7的蛋白和mRNA表达。结果 与C组相比,H组大鼠卵巢体积减小,生长卵泡数明显减少（P<0.05）,大鼠卵巢指数下降（P<0.05）,血清中E2水平降低和FSH水平上升（P<0.05）。免疫组织化学和Real-time PCR结果显示,Smad2（p-Smad2）、Smad3（p-Smad3）、Smad4和Smad7蛋白在卵巢各级卵泡均有表达,H组Smad2蛋白和mRNA表达增加（P<0.05）,Smad2磷酸化水平（p-Smad2）表达增高（P<0.05）;Smad3、Smad4和Smad7蛋白和mRNA表达减少（P<0.05）,p-Smad3 表达降低（P<0.05）。结论 顺铂诱导大鼠卵泡损伤并促进卵巢早衰,引起卵泡细胞内Smad2表达增加,Smad3、Smad7表达降低,Smad细胞内信号通路参与了化疗性卵巢损伤的过程。     

Smad3基因敲除小鼠肾Smad2和p-Smad2表达的变化

目的:观察Smad3基因敲除小鼠肾Smad2和p-Smad2表达的变化,探讨Smad3基因敲除小鼠肾是否有Smad2和p-Smad2代偿性增加.方法:4只Smad3基因敲除小鼠,10只野生型小鼠,应用免疫组织化学显色技术,检测Smad2和p-Smad2蛋白的定位和表达情况,并用Motic病理图像分析系统对图像进行半定量分析.结果:野生型小鼠肾Smad2蛋白在肾远端小管和肾集合管细胞胞质中有广泛弱表达,p-Smad2蛋白在肾远端小管和肾集合管细胞胞质、胞核中也有弱表达,而Smad3基因敲除小鼠的Smad2和p-Smad2的表达比野生型小鼠有显著升高.结论:Smad3基因敲除能引起小鼠肾Smad2和p-Smad2表达的代偿性增加.     

胰岛素控制血糖对糖尿病大鼠肾组织Smad7表达及纤维化病变的影响

 目的：观察胰岛素控制糖尿病大鼠血糖后是否能上调肾组织Smad7的表达,减轻或延缓糖尿病肾病(DN)肾纤维化病变的发生发展。方法：链脲菌素复制大鼠糖尿病模型,随机分为糖尿病组(DM组) 和胰岛素治疗组(INS组) (n=8);INS组于成模13周起用胰岛素将血糖控制在4~7 mmol/L;同时设正常对照组(NC组)(n=8)。17周处死大鼠,检测相应生化指标,观察胰腺和肾组织病理学改变,免疫组化和Western blotting检测各组大鼠肾组织组织转化生长因子β1 (transforming growth factor β1, TGF-β1)、Smad泛素化调节因子2(Smad ubiquitin regulatory factor 2, Smurf2)、Smad7、 E-钙黏蛋白(E-cadherin)、α-平滑肌肌动蛋白(α-smooth muscle actin, α-SMA)、层连蛋白(fibronectin, FN)和胶原蛋白Ⅰ(collagenⅠ)的蛋白表达。结果：与NC组比较,DM组大鼠体重显著减轻,24 h尿蛋白、血糖和甘油三酯显著升高(P<0.05),病理检查显示胰岛被破坏,肾组织TGF-β1、Smurf2、α-SMA、FN和collagenⅠ蛋白的表达均显著增加(P<0.05),并伴有肾小管Smad7和E-cadherin的表达减少(P<0.05);而经胰岛素控制血糖后,INS组大鼠较DM组体重逐渐增加,24 h尿蛋白和血糖均显著降低 (P<0.05),肾纤维化病变明显改善,TGF-β1、Smurf2、α-SMA、FN和collagenⅠ蛋白的表达均显著减少(P< 0.05),Smad7和E-cadherin的表达显著上调(P<0.05)。结论：控制血糖能恢复糖尿病大鼠肾组织Smad7蛋白表达水平,减少细胞外基质的沉积,延缓DN的纤维化进展,其机制可能与肾组织中TGF-β1和Smurf2表达降低、Smad7蛋白的泛素化降解减少有关。     

Small hepatocellular carcinoma: Its relationship to multistep hepatocarcinogenesis

Recent advances In imagfng techniques have led to the discovery of small hepatocellular carcinomas (HCC). The small HCC most often exhibit low-grade malignant (LGM) or extremely well differentiated features, which are different from those of advanced, full-blown HCC. The LGM-HCC present a serious diagnostic challenge to pathologists and must be differentiated from benign (reactive) and atypical (borderline) hyperplastic nodules. Analysis of small HCC revealed that hepatocarcinogenesis frequently occurs step-wise from atypical hyperplasia to LGM-HCC and subsequently to advanced HCC. The HCC arise in irregular regeneration in chronic liver disease and in the essentially normal liver after steroid administration. Although the tumor suppressor gene, p53, is revealed to be often mutated in advanced HCC, the genetic events corresponding to each stage of multistep hepatocarcinogenesis are not clarified at all.     

Smad7和组蛋白去乙酰化酶1在小鼠马兜铃酸肾病中的表达

目的 探讨Smad7、组蛋白去乙酰化酶1(HDAC1)在小鼠马兜铃酸肾病(AAN)中的表达及两者在马兜铃酸肾病发生、发展中的作用.方法 将32只体重(20±2)g 的SPF(无菌)雄性昆明小鼠随机分为4组,其中3组为实验组,灌胃给予不同剂量的马兜铃酸(AA)Ⅰ,分别为4 mg/(kg·d)、8 mg/(kg·d)、16mg/(kg·d).另设对照组,PBS灌胃.应用免疫组织化学、免疫印迹法及RT-PCR技术,检测AAN小鼠和正常对照组中Smad7和HDAC1的表达情况.结果 HDAC1阳性着色主要分布于细胞核上,且在AAN中的表达强度明显高于正常对照组.免疫印迹法检测和RT-PCR提示,Smad7在AAN中的表达低于对照组,而HDAC1的表达显著高于对照组.结论 在AAN中Smad7低表达以及HDAC1高表达,提示Smad7和HDAC1可能在AAN的发生、发展中起重要作用.     

Smad2和Smad4在家猫睾丸发育和精子发生中的表达与定位

目的 研究转化生长因子β(TGF-β)超家族的下游信号转导分子Smad2和Smad4蛋白,在不同发育阶段家猫睾丸中的表达和定位,探索Smad2和Smad4蛋白与家猫睾丸发育和精子发生的关系. 方法 应用免疫组织化学技术,研究Smad2和Smad4蛋白在幼年(n=3)、青春期(n=3)和性成熟(n=18)睾丸中的定位,并通过Western blotting技术对免疫组织化学中所用抗体的特异性进行了检测. 结果 免疫组织化学结果显示,Smad2和Smad4蛋白定位于各发育阶段家猫睾丸的生殖细胞、支持细胞和间质细胞的胞质中;Western blotting结果显示,多克隆兔抗Smad2和Smad4抗体与家猫睾丸蛋白提取物中分子量约为58kD、66kD的蛋白条带发生免疫阳性反应. 结论 Smad2和Smad4蛋白在家猫睾丸发育和精子发生的各个阶段均有表达,提示其参与睾丸发育和精子发生的调节.     

Expression and localization of Smad2 and Smad4 proteins in the porcine ovary

The objective of the present study was to investigate the temporal and spatial expression of Smad2 and Smad4 proteins, the downstream signaling molecules of the transforming growth factor beta (TGF-β) superfamily, in the porcine ovary. Cellular localization of Smad2 and Smad4 proteins was examined using immunohistochemistry. The specificity of the antibodies was examined using Western blot assay. Western blot analyses demonstrated that 52 kDa Smad2 and 60 kDa Smad4 proteins were expressed in the porcine ovary. Immunohistochemistry revealed that Smad2 and Smad4 were widely expressed in the porcine ovary, mainly localized in the oocyte, granulosa and thecal cells at different stages of folliculogenesis. Within the primordial and primary follicles, Smad2 and Smad4 showed strong staining in oocytes and follicular cells. In the antral follicle, strong staining was observed in oocytes, granulosa and theca cells. These findings suggest that Smad2 and Smad4 may be a key regulator of follicular development and growth of oocytes in the porcine ovary.     

Smad7过度表达抑制3T3细胞增殖和TGF-β1基因表达

研究Smad7过度表达对TGF β1基因表达的调控和对 3T3细胞增殖的影响。实验将Smad7质粒 ,通过脂质体介导转染NIH3T3细胞 ,应用RT PCR方法鉴定转染结果和检测TGF β1mRNA的表达 ,以及用免疫细胞化学检测TGF β1蛋白的表达情况 ,并观察基因转染对细胞增殖的影响。结果显示转染Smad7后 ,NIH3T3细胞中TGF β1mRNA的表达显著减少 (P <0 0 5 ) ,TGF β1蛋白的表达下降 ,细胞增殖明显减缓 (P <0 0 5 )。提示Smad7过度表达能够抑制 3T3细胞的增殖和TGF β1基因的表达 ,可以通过阻断TGF β细胞内信号传导来调控TGF β1的生物学行为。     

Reduced CRYL1 expression in hepatocellular carcinoma confers cell growth advantages and correlates with adverse patient prognosis

Homozygous deletion screening has been widely utilized to define tumour suppressor genes (TSGs) in cancers. Although these biallelic deletions are infrequent, their identification has facilitated the discovery of many important TSGs. We have systematically examined the genome of hepatocellular carcinoma (HCC), a highly malignant tumour that is rapidly fatal, for the presence of homozygous deletions. Array‐CGH analysis on early passage of HCC cultures and cell lines led us to identify six homozygous deleted (HD) regions. A high concordance between array‐CGH and expression of HD genes was demonstrated, where crystallin Lambda1 (CRYL1; located on chromosome 13q12.11) displayed the most frequent down‐regulation. We found that reduced mRNA expression of CRYL1 was common in HCC tumours when compared with their adjacent non‐tumoural liver (p = 0 . 0097). Significant associations could also be drawn between repressed CRYL1 and advanced tumour staging, increased tumour size, and shorter disease‐free survival of patients (p < 0 . 037). Moreover, homozygous deletions on CRYL1 could be detected in 36% of HCC cases, where recurrent HDs were identified on exons 1, 5, and 8. Examination of other causal events suggested histone deacetylation and promoter hypermethylation to be likely inactivating mechanisms as well. Re‐expression of CRYL1 in the SK‐Hep1 cell line, where biallelic loss of CRYL1 was found, induced profound inhibition of cellular proliferation and cell growth (p < 0 . 0015). By Annexin V staining, CRYL1 restoration readily increased pro‐apoptotic cells with an induction of PARP cleavage. Flow cytometry further revealed that CRYL1 could prolong the G₂–M phase, possibly through interruption of the Cdc2/cyclin B pathway. Given that regional chromosome 13q12–q14 loss is a causal genomic event in HCC tumourigenesis, our finding may have implications for identifying a novel TSG CRYL1 within this important locus. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

奥曲肽联合腺相关病毒介导的黑色素瘤分化相关基因7对肝癌的抑制作用

目的 观察不同剂量的奥曲肽联合PEG启动子调控的黑色素瘤分化相关基因7表达重组腺相关病毒系统(rAAV-PEG-MDA-7)对非肥胖糖尿病-重症联合免疫缺陷(NOD-SCID)小鼠肝癌移植瘤的抑制作用.方法 构建rAAV-PEG-MDA-7表达系统并建立肝癌细胞株HepG2的NOD-SCID小鼠皮下移植瘤模型,以尾静脉注射rAAV-PEG空载体+肿瘤周边皮下注射生理盐水为对照,按照尾静脉注分射不同病毒量的rAAV-PEG-MDA-7及肿瘤周边皮下注射不同剂量的奥曲肽组合为8个实验组.注射药物后21d处死小鼠,比较各组小鼠移植瘤质量.结果 单独应用rAAV-PEG-MDA-7或奥曲肽均能抑制小鼠移植瘤的生长.不同剂量的奥曲肽(5μg/kg、30 μg/kg)与低剂量MDA-7(1×1011 particles)联用时,可以增加MDA-7的抑制肿瘤作用[(1.14±0.24)g,(0.98±0.11)g比(1.71±0.26)g,均P＜0.05];不同剂量奥曲肽(5 μg/kg、30 μg/kg)与高剂量MDA-7(5×1011 particles)联用时,亦可增加MDA-7的抑制肿瘤作用[(1.05±0.21)g、(0.90±0.18)g比(1.41±0.20)g,均P＜O.05].不同剂量MDA-7(1×1011 particles、5×1011particles)与低剂量奥曲肽(5μg/kg)联用时,可以增加奥曲肽的抑制肿瘤作用[(1.14±0.24)g、(1.05±0.21)g比(1.68±0.18)g,均P＜0.05];不同剂量MDA-7(1×1011 particles、5×1011particles)与高剂量奥曲肽(30 μg/kg)联用时,亦可增加奥曲肽的抑制肿瘤作用[(0.98±0.11)g、(0.90±0.18)g比(1.34±0.12)g,均P＜O.05].结论 MDA-7与奥曲肽联合应用可以增强对小鼠肝癌移植瘤的抑制作用.     

Reduced Siglec-7 expression on NK cells predicts NK cell dysfunction in primary hepatocellular carcinoma

Major histocompatibility complex class I (MHC-I)-dependent inhibitory receptors on natural killer (NK) cells have been found to contribute to NK cell dysfunction in hepatocellular carcinoma (HCC). However, the roles of MHC-I-independent inhibitory receptors on NK cells in HCC remain poorly defined. In this study, we analyzed the expression of the MHC-I-independent inhibitory receptors sialic acid-binding immunoglobulin-like lectin (Siglec)-7 and Siglec-9 on NK cells by analyzing the peripheral blood of 35 HCC patients and 63 healthy donors. We observed that HCC patients had lower frequencies and total numbers of NK cells in the peripheral blood. Importantly, both the expression levels of Siglec-7 on NK cells and the frequencies of Siglec-7⁺ NK cells were significantly reduced in HCC patients, which was accompanied by a decrease in activating receptor and an increase in inhibitory receptor expression on NK cells. Moreover, Siglec-7⁺ NK cells expressed higher levels of activating receptors and displayed stronger effector functions, compared with Siglec-7⁻ NK cells. Our findings demonstrate for the first time that reduced Siglec-7 expression predicts NK cell dysfunction in HCC patients, suggesting that Siglec-7 may be a potential marker of functional NK cell subset in HCC patients.