A trip through the signaling pathways of melanoma

Many cellular signaling pathways are involved in the development of cancer. Depending on the tumor entity, the nature as well as the mode of activation can differ. Some signaling pathways frequently show changes as all tumor cells have to fulfill some basic requirements such as independence from growth factors or insensitivity against apoptosis. In this review, the possibilities of a tumor to manipulate signaling pathways to reach these goals are exemplified based on an archetypical melanoma cell. In addition, new therapeutic options based on the knowledge of signaling pathways will be discussed.     

原发性肝癌治疗前后血清可溶性上皮钙粘蛋白水平变化的研究

目的：探讨原发性肝癌（HCC）患者治疗前,后的血清可溶性上皮钙粘蛋白（SE－Cadherin)水平变化,方法：用酶联免疫吸附双抗体夹心法检测26例HCC患者治疗前,后的血清SE－Cadherin水平及21例正常健康人血清SE－Cadherin水平。结果：原发性肝癌患者治疗前血清SE-Cadherin水平明显高于治疗后,其差异有显著性意义（P＜0．01）,而正常健康人血清SE－Cadherin水平不高,结论：血清SE－Cadherin 水平的测定可作为原发性肝癌的诊断及疗效观察指标,并有可能成为预后评判和复发指标。     

三阴性乳腺癌细胞脂肪非典型钙黏蛋白4表达下调的生物学作用及机制

背景与目的 三阴性乳腺癌（TNBC）容易发生侵袭转移,恶性程度极高。笔者团队前期研究发现脂肪非典型钙黏蛋白4（FAT4）在TNBC组织中呈低表达且与预后相关,进而本研究进一步探讨FAT4对TNBC细胞生物学行为的影响,及其相关机制。方法 用qRT-PCR及Western blot检测正常人乳腺上皮细胞系（MCF-10A）及不同TNBC细胞系（BT-549、MDA-MB-231、MDA-MB-468、MDA-MB-436）中FAT4的表达水平。选择其中合适的TNBC细胞系,分别转染FAT4-shRNA（FAT4敲低组）、阴性对照序列（阴性对照组）,以未处理的TNBC细胞为空白对照组,分别采用CCK-8实验、流式细胞术、Transwell小室实验检测细胞增殖能力、凋亡率、侵袭与转移能力的变化,并用Western blot检细胞中Hippo信号通路下游靶点YAP及上皮间质转化（EMT）相关蛋白的变化。结果 与正常人乳腺上皮细胞比较,各TNBC细胞系中FAT4的mRNA与蛋白表达量均不同程度的降低（均P<0.05）。功能实验选用BT-549细胞和MDA-MB-436细胞。无论在BT-549细胞或MDA-MB-436细胞中,与空白对照组比较,FAT4敲低组在转染后24、48、72 h的增殖能力均明显升高、凋亡率明显降低、侵袭与转移能力明显增强（均P<0.05）;YAP蛋白表达量无明显变化（P>0.05）,但磷酸化YAP（p-YAP）表达量明显降低,上皮标志物E-cadherin水平明显降低,而间质标志物N-cadherin水平明显升高（均P<0.05）;阴性对照组与空白对照组间以上指标差异均无统计学意义（均P>0.05）。结论 FAT4表达水平在TNBC细胞中普遍降低,FAT4表达的降低能增强TNBC细胞增殖和侵袭迁移能力、减少TNBC细胞凋亡,其机制可能与FAT4降低后Hippo信号通路下游的YAP蛋白磷酸化减少,从而促进EMT进程有关。     

Mir-7上调增强肺腺癌对吉非替尼敏感性的机制研究

目的:探索上调Mir-7的表达使肺腺癌A549细胞增强吉非替尼的敏感性及其机制。方法:用lipo-fectamine2000携带Mir-7对A549细胞进行瞬时转染。将A549细胞分为对照组、转染组、吉非替尼组与联合组。MTT法测各组细胞增殖率变化,Transwell检测细胞侵袭性,Real time PCR检测E-Cadherin及N-Cad-herin的mRNA表达的变化,Western blot检测他们的蛋白表达的变化。结果:上调A549细胞中Mir-7的表达与吉非替尼共同作用较单独吉非替尼作用有更显著的抑制作用。用Mir-7转染后,肺腺癌A549细胞的侵袭力下降。转染与吉非替尼联合组E-Cadherin的信使RNA及蛋白的表达变化不大,但N-Cadherin表达下降。结论:上调Mir-7的表达可以增强肺腺癌细胞对吉非替尼的敏感性,其机制可能是过量表达的Mir-7抑制了IGF-1R信号通路及肿瘤上皮细胞间质化。     

人脐静脉内皮细胞损伤后迁移能力的变化与血管内皮钙黏蛋白和连环蛋白p120的关系

目的初步探讨人脐静脉内皮细胞(HUVEC)损伤之后迁移能力的变化与血管内皮钙黏蛋白(VE-cad)和连环蛋白p120(p120ctn)的关系。方法 DMEM培养基培养HUVEC,将HUVEC分为对照组和损伤组。Transwell实验检测HUVEC迁移能力的变化。Western blot测定p120ctn与VE-cad蛋白表达水平。免疫荧光实验检测VEcad的定位表达变化。免疫共沉淀法检测p120ctn与VE-cad的相互结合。结果 Transwell实验发现HUVEC经损伤刺激6、8 h后迁移能力最强(P0.05)。Western blot结果显示HUVEC损伤6、8 h后p120ctn及VE-cad表达水平明显上调。免疫荧光实验显示HUVEC经损伤刺激后,VE-cad的定位由细胞膜转到细胞浆。免疫共沉淀证实p120ctn可以与VE-cad相互结合。结论 HUVEC损伤刺激后迁移能力增强,其机制可能与升高的p120ctn将VEcad由细胞膜携带入细胞浆导致VE-cad膜表达缺失有关。     

Skeletal muscle stem cells do not transdifferentiate into cardiomyocytes after cardiac grafting

Skeletal muscle cell-derived grafts in the heart may benefit myocardial performance after infarction. Several studies have suggested that skeletal muscle stem cells (satellite cells) from adult muscle undergo transdifferentiation into cardiomyocytes after grafting into the heart, but expression of cardiac markers in graft cells has not been rigorously confirmed. To determine the fate of satellite cell-derived grafts in the heart, adult rat satellite cells were tagged in vitro with bromodeoxyuridine (BrdU) and grafted into normal hearts of syngeneic rats. At 4 and 12 weeks the graft cells formed multinucleated, cross-striated myofibers that expressed fast skeletal myosin heavy chain (MHC), thus indicating a mature skeletal muscle phenotype. Double staining for the BrdU tag and cardiac-specific markers was employed to identify transdifferentiation. Aside from four questionable cells, none of the 11 grafts examined expressed alpha-MHC, cardiac troponin I, or atrial natriuretic peptide. At 4 weeks, grafts expressed beta -MHC, a hallmark of slow twitch myofibers. By 12 weeks, however, the myofibers had atrophied and downregulated beta-MHC. Grafts never expressed the intercalated disk proteins N-cadherin or connexin43, hence electromechanical coupling did not occur. In conclusion, satellite cells differentiate into mature skeletal muscle and do not express cardiac-specific genes after grafting into the heart. Thus, transdifferentiation into cardiomyocytes did not occur.     

N-cadherin haploinsufficiency affects cardiac gap junctions and arrhythmic susceptibility

Cardiac-specific deletion of the murine gene (Cdh2) encoding the cell adhesion molecule, N-cadherin, results in disassembly of the intercalated disc (ICD) structure and sudden arrhythmic death. Connexin 43 (Cx43)-containing gap junctions are significantly reduced in the heart after depleting N-cadherin, therefore we hypothesized that animals expressing half the normal levels of N-cadherin would exhibit an intermediate phenotype. We examined the effect of N-cadherin haploinsufficiency on Cx43 expression and susceptibility to induced arrhythmias in mice either wild-type or heterozygous for the Cx43 (Gja1)-null allele. An increase in hypophosphorylated Cx43 accompanied by a modest decrease in total Cx43 protein levels was observed in the N-cadherin heterozygous mice. Consistent with these findings N-cadherin heterozygotes exhibited increased susceptibility to ventricular arrhythmias compared to wild-type mice. Quantitative immunofluorescence microscopy revealed a reduction in size of large Cx43-containing plaques in the N-cadherin heterozygous animals compared to wild-type. Gap junctions were further decreased in number and size in the N-cad/Cx43 compound heterozygous mice with increased arrhythmic susceptibility compared to the single mutants. The scaffold protein, ZO-1, was reduced at the ICD in N-cadherin heterozygous cardiomyocytes providing a possible explanation for the reduction in Cx43 plaque size. These data provide further support for the intimate relationship between N-cadherin and Cx43 in the heart, and suggest that germline mutations in the human N-cadherin (Cdh2) gene may predispose patients to increased risk of cardiac arrhythmias.     

Knockdown of liver-intestine cadherin decreases BGC823 cell invasiveness and metastasis in vivo

AIM: To assess BGC823 gastric cancer (GC) cell metastasis after knockdown of liver-intestine cadherin (CDH17) and the therapeutic value of CDH17-RNAi-lentivirus in vivo.METHODS: We evaluated primary tumor growth and assessed local infiltration and systemic tumor dissemination using an orthotopic implantation technique. The therapeutic value of CDH17 knockdown was examined by intratumoral administration of CDH17-RNA interference (RNAi)-lentivirus in an established GC tumor xenograft mouse model. Furthermore, a comparative proteomic approach was utilized to identify differentially expressed proteins in BGC823 and lenti-CDH17-miR-neg cells following CDH17 knockdown.RESULTS: Metastases in the liver and lung appeared earlier and more frequently in animals with tumors derived from BGC823 or lenti-CDH17-miR-neg cells than in tumors derived from lenti-CDH17-miR-B cells. Average tumor weight and volume in the CDH17-RNAi-lentivirus-treated group were significantly lower than those in the control group (tumor volume: 0.89 ± 0.04 cm³ vs 1.16 ± 0.06 cm³, P < 0.05; tumor weight: 1.15 ± 0.58 g vs 2.09 ± 0.08 g, P < 0.05). Fifteen differentially expressed proteins were identified after CDH17 silencing in BGC823 cells, including a variety of cytoskeletal and chaperone proteins as well as proteins involved in metabolism, immunity/defense, cell proliferation and differentiation, cell cycle, and signal transduction.CONCLUSION: Our data establish a foundation for future studies of the comprehensive protein expression patterns and effects of CDH17 in GC.     

蛋白酪氨酸磷酸酶参与促发的细胞移动过程

 目的　探讨蛋白酪氨酸磷酸酶SHP-2在IL-1β所促发的细胞移动中的作用。方法　构建重组质粒SHP-2-GFP以及SHP-2C>S-GFP 并分别转入MCF-7乳腺癌细胞中，建立SHP-2-GFP- MCF-7和SHP-2C>S-MCF-7细胞株。采用荧光显微镜技术观察细胞移动情况；RT-PCR、免疫印迹法检测钙黏蛋白和金属蛋白酶的变化情况，确定蛋白磷酸酶SHP-2在细胞移动中的作用。结果　E-钙黏蛋白在IL-1β刺激的SHP-2转染的乳腺癌细胞株中的表达量是最低的，而金属蛋白酶MMP-9的表达量最高。结论　SHP-2参与IL-1β促发的细胞移动，并且通过减少E-钙黏蛋白的表达以及增强金属蛋白酶MMP-9的分泌来发挥作用的。