重组人内皮抑素的纯化及抗肿瘤活性研究

[目的]从高效表达的基因工程菌中纯化重组人内皮抑素,对其抗肿瘤活性进行研究.[方法]经异丙基硫代-β-D-半乳糖苷(IPTG)诱导,重组人内皮抑素在大肠杆菌基因工程菌中以包涵体形式高效表达.通过凝胶层析纯化重组内皮抑素蛋白.应用鸡胚绒毛尿囊膜实验(CAM),肺癌细胞MTT试验及细胞迁移抑制实验,裸鼠皮下移植喉癌抑瘤实验、病理组织切片、免疫组化指标的测定等检测研究重组人内皮抑素的抗肿瘤活性.[结果]重组内皮抑素的复性率可达40%.重组内皮抑素在体外直接抑制肺癌细胞的增殖及迁移.用药21天,对裸鼠皮下移植喉癌的抑瘤率达到40.66%,HE染色、免疫组化及CAM实验表明其对肿瘤组织新生血管的生成有较强的抑制作用.[结论]重组人内皮抑素具有抑制肿瘤组织新生血管生成和直接抑制肿瘤细胞生长和迁移的双重抗肿瘤活性.     

癌-睾丸抗原GAGE-1基因的重组、表达及纯化

目的 为进一步研究临床应用癌-睾丸抗原GAGE-1诱导特异性抗肿瘤免疫反应,对GAGE-1基因进行克隆、体外原核重组表达及蛋白分离纯化。方法 运用RT-PCR技术从人QGY-7701肝癌细胞株中扩增GAGE-1基因片段,插入原核表达载体pGEX-6p-1中,构建重组表达质粒pGEX-6p-1-GAGE-1,并导入大肠杆菌BL21,IPTG诱导目的蛋白表达;经包涵体透析复性及GST柱亲和层析纯化目的蛋白,SDS-PAGE电泳分析鉴定。结果 扩增得到GAGE-1基因5’端251 bp片段,与GeneBank公布的序列一致,构建的PGEX-6p-1-GAGE-1原核表达质粒经IPTG诱导,在大肠杆菌中表达分子量约35.7 kD的GST-GAGE-1融合蛋白,纯化后蛋白纯度为90%以上。结论 成功构建PGEX-6p-1-GAGE-1重组表达质粒,并成功表达纯化了GST-GAGE-1融合蛋白,为进一步深入研究GAGE蛋白奠定了基础。     

肿瘤-睾丸抗原LAGE-1基因的原核表达纯化和抗血清制备

目的:构建人肿瘤-睾丸抗原LAGE-1的原核表达质粒,表达、纯化LAGE-1融合蛋白并制备GST-LAGE-1多克隆抗体。方法:逆转录聚合酶链反应(RT-PCR)方法扩增人肝癌组织LAGE-1基因3′端片段,连入原核表达载体pGEX-4T-1( ),构建原核表达质粒pGEX-LAGE-1并测序。将该质粒转化大肠埃希菌BL21(DE3)进行诱导表达,经包涵体透析复性和谷胱甘肽巯基转移酶纯化系统分离纯化目的蛋白。用纯化的融合蛋白GST-LAGE-1免疫新西兰大白兔,间接ELISA法测定抗体效价,饱和硫酸铵沉淀法纯化抗体,并采用Western blot检测GST-LAGE-1多克隆抗体特异性。结果:RT-PCR扩增得到LAGE-1基因3′端264bp片段,测序结果与GenBank公布序列一致;成功构建pGEX-LAGE-1原核表达质粒,含有该质粒的大肠埃希菌经IPTG诱导后表达相对分子质量约为36×103的蛋白,经包涵体复性和GST融合蛋白纯化系统纯化,得到重组蛋白GST-LAGE-1,纯度达90%;制备兔抗GST-LAGE-1抗体,纯化的抗体经Western blot证实可与目的蛋白特异性结合。结论:获得了纯化的肿瘤-睾丸抗原LAGE-1重组蛋白及其特异性多克隆抗体,为进一步研究LAGE-1抗原在肿瘤免疫治疗中的作用奠定基础。     

抗人膀胱癌单链抗体在大肠杆菌中表达及复性研究

抗人膀胱癌单链抗体的构建及表达成功为高特异性诊断和治疗膀胱癌带来了新的途径.本研究对其进行表达和复性研究,为其进入中试和临床应用奠定了基础.具体过程和方法如下.采用本室克隆的抗人膀胱癌抗体重轻链可变区基因以及构建的适于单链抗体表达的谷胱甘肽流基转移酶(GST)融合表达载体pROH80,在大肠杆菌XL1-blue中经1mM IPTG,37℃诱导表达抗人膀胱癌单链抗体.SDS-PAGE和Westem印迹分析表明,融合型单链抗体以包涵体形式存在于超声沉淀中,其表达量可达细菌总蛋白量的30%,而空载体表达GST主要以可溶形式存在于超声上清中.降低诱导强度(0.1mM OPTG,28℃)表达并未影响包涵体形式表达.此外,更换其它培养基,如SB2和M9CAA,也未见明显效果.于是,我们对包涵体进行了一系列复性研究.     

重组Prohibitin融合蛋白包涵体的纯化

[目的]获得高纯度具有免疫活性的Prohibitin融合蛋白.[方法]异丙基-β-D硫代半乳糖苷(IPTG)诱导重组大肠杆菌BL21(pET30a( )-prohibitin)表达,其融合蛋白包涵体经过洗涤、变性、复性后,用Ni-NTA Agarose亲和层析柱分离纯化.通过12%SDS-PAGE胶和Bradford法检测其纯度和目的蛋白含量,用ELISA对纯化后的蛋白进行鉴定.[结果]从融合蛋白包涵体中纯化到具有免疫活性的目的蛋白,其纯度达90%以上,含量约0.3mg/ml.[结论]建立了有效纯化融合蛋白包涵体的方法,为对Prohibitin进一步的结构和功能研究奠定基础.     

小鼠成纤维细胞激活蛋白α二肽基肽酶核心序列原核表达与纯化及复性

表达质粒,通过对转化该质粒后的感受态细菌进行菌液PCR鉴定以及对该质粒进行BamH I和Xho I双酶切鉴定,鉴定结果与预期结果完全一致;实现了对该质粒编码的融合蛋白His6-FAPαc的表达,表达后的融合蛋白主要以包涵体的形式存在,表达产量占菌体总蛋白＞70%;纯化了该融合蛋白,纯化后的蛋白纯度通过灰度分析＞99%;对该融合蛋白进行了复性,复性后该融合蛋白由不溶的包涵体状态变为可溶的水溶状态.结论:成功表达、纯化和复性了FAPα二肽酶催化核心区域FAPαc,为深入开展FAPα的研究奠定基础.     

MDM2/4-p53双靶点抑制蛋白原核表达载体的构建与蛋白制备

目的:采用分子克隆技术和大肠杆菌原核表达系统制备具备生物学活性MDM2/4-p53双靶点抑制蛋白.方法:首先应用PCR合成大肠杆菌硫氧还蛋白(thioredoxin,Trx)A的cDNA序列,将其插入到大肠杆菌原核表达载体pET40b中,将人工合成的人免疫缺陷病毒(human immuno-deficiency virus,HIV-1)反式激活蛋白(transactivator,TAT)的蛋白转导结构域(protein transduction domain,PTD)和MDM2/4双抑制肽pDI(peptide double inhibition)的cDNA序列分别插入到Trx序列的C端和核心位点,从而构建出可表达MDM2/4-p53双靶点抑制蛋白的原核表达载体pET-TAT-TrxA-pDI.然后将pET-TAT-TrxA-pDI原核表达载体转化大肠杆菌表达菌种BL21感受态细胞,应用异丙基-β-D-硫代半乳糖苷(isopropyl β-D-1-thiogalactopyranoside,IPTG)诱导蛋白表达,筛选最优表达的单克隆菌种,分析重组蛋白的表达部位,并了解不同IPTG浓度(0.1 mmol/L、0.4mmol/L、0.7mmol/L、1.0mmol/L)、温度(16℃、25℃、37℃)、表达诱导时间(1h、2h、3h、4h、5h、6h、7h)对MDM2/4-p53双靶点抑制蛋白表达的影响,以获得最优的蛋白表达条件.最终利用MDM2/4-p53双靶点抑制蛋白携带的His标签,采用能够特异性结合His标签的蛋白纯化柱进行蛋白纯化,并应用梯度透析法和氧化还原法进行MDM2/4-p53双靶点抑制蛋白的体外折叠.结果:成功构建可以表达MDM2/4-p53双靶点抑制蛋白的原核表达载体pET-TAT-TrxA-pDI,并实现MDM2/4-p53双靶点抑制蛋白在大肠杆菌表达菌种BL21(DE3)中的高效表达,表达量占总蛋白表达量的60％以上,并且主要存在于包涵体中.蛋白表达条件优化结果发现,温度对重组蛋白表达无明显影响,而应用0.4mmol/L的IPTG浓度和3h的诱导时间即可获得重组蛋白的高效表达.经过蛋白纯化后获得纯度99.99％的重组蛋白,将纯化的MDM2/MDM4双靶点抑制蛋白溶液用梯度透析复性和氧化还原复性法最终成功获得包涵体蛋白的体外正确折叠,复性效率约为80％.结论:成功实现MDM2/4-p53双靶点抑制蛋白在大肠杆菌原核表达系统中的高效表达、纯化以及体外的正确折叠,最终获得高纯度并具有生物学活性的MDM2/4-p53双靶点抑制蛋白,从而为进一步MDM2/4-p53双靶点抑制蛋白抗肿瘤活性与机制的研究奠定了基础.     

牛蛙核糖核酸酶的表达和鉴定及功能检测

目的:在大肠埃希菌中高效表达牛蛙核糖核酸酶(ranacatesbeianaribonuclease,RCRNase),并对其纯化产物进行噻唑蓝(tetrazoliumblue,MTT)实验,观察对肝癌细胞的抑制效果。方法:用异丙基硫代D半乳糖苷(isopropylthioDgalactoride,IPTG)诱导原核表达质粒PET32aRCRNase在大肠埃希菌E.coliBl21(DE3)plysS中表达。菌体经超声、离心后,用NiNTAAgarose亲和层析法对包涵体进行纯化。采用MTT法检测纯化的目的蛋白对体外培养的肝癌细胞的杀伤活性。结果:纯化的目的蛋白经十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodiumdodecylsulphatepolyacrylamidegeleletrophoresis,SDSPAGE)蛋白电泳表明,RCRNase在大肠埃希菌中是以包涵体的形式表达。用MTT法的结果中可以看出,纯化的目的蛋白对体外培养的肝癌细胞具有一定的抑制效果,其IC50值(半抑制浓度)是22.44μg/mL。结论:牛蛙核糖核酸酶在大肠埃希菌中得到大量表达,为进一步研究其生物学特性以及功能打下了良好的基础。     

FasL基因构建蛋白表达及其对胃癌细胞株BGC823和MGC803生长的影响

目的:构建适于原核表达的重组蛋白FasL表达载体,并进行重组蛋白的表达纯化及抗肿瘤活性分析.方法:获得人FasL cDNA全序列,将其分段设计引物,通过重叠PCR获得FasL基因.构建pGEX-5X-1/FasL表达载体.转化大肠杆菌BL21(DE3),IPTG诱导表达,GST柱纯化.采用MTT比色法、流式细胞法检测融合蛋白对胃癌细胞的作用.结果:通过重叠PCR获得了编码正确氨基酸序列的目的基因.表达的目的蛋白表达量占菌体总蛋白的30%以上.纯化后,蛋白纯度达95%rX上.MTT比色法与流式细胞技术均表明纯化的融合蛋白能抑制胃癌细胞株BGC823和MGC803的生长,诱导其调亡增加.结论:重组蛋白FasL表达载体的成功构建、表达、纯化及活性分析,为进一步的抗肿瘤功能研究奠定了基础.     

GST-hDaxx蛋白的构建及其原核表达产物的鉴定

 目的　构建GST hDaxx蛋白并在原核细胞中诱导表达GST hDaxx融合蛋白 ,并研究其与 p5 3的结合能力。方法　构建GST hDaxx融合蛋白原核细胞表达载体pGEX 4T/hDaxx ,在大肠杆菌 (E .col i)中用异丙基 β D 硫代半乳糖苷 (IPTG)诱导表达。表达产物用亲和层析柱加以纯化后 ,Westernblot鉴定表达产物与纯化物。通过共免疫沉淀反应与Westernblot观察hDaxx与p5 3的结合反应。结果　在原核细胞中成功表达了GST hDaxx融合蛋白 ,hDaxx与 p5 3可发生共免疫沉淀反应。 结论　 1.GST hDaxx融合蛋白成功表达 ;2 .hDaxx和 p5 3的相互结合提示它们可能与肿瘤的发生有关。     

Enforced effect of tk-MCP-1 fusion gene in ovarian cancer

ABSTRACT: OBJECTIVE: The efficiency of HSV-tk/GCV system is not high because of insufficient gene transfer and incompletely initiative of host antineoplastic potency. The present study was designed to assess the antitumor efficacy of tk-MCP-1 on ovarian cancer in vitro and vivo. METHODS: A novel bicistronic expression system can help to improve the expression level of a gene in a stable manner. pLXSN/tk-MCP-1 co-expressing tk and MCP-1 genes was constructed using a pLXSN retroviral vector and an internal ribosome entry site sequence by restriction enzyme. Western blot were performed to determine tk and MCP-1 expression in the infected SKOV3. The GCV-sensitively tumoricidal activities of SKOV3/tk-MCP-1 with or without monocytes were comparable to those of SKOV3 expressing HSV-tk or MCP-1. We investigated the growth of subcutaneous tumors in SCID mice immuno-reconstituted, and evaluated the antitumor effect of MCP-1 in conjunction with suicide gene. RESULTS: The significant GCV-sensitively tumoricidal activity of pLXSN/tk-MCP-1 was observed when compared with those of pLXSN/tk, pLXSN/MCP-1 and pLXSN/neo, especially when monocytes were added. The growth of subcutaneous tumors in SCID mice immuno-reconstituted was markedly suppressed by co-delivery of HSV-tk and MCP-1 genes, and the enhanced antitumor effect was associated with the recruitment of monocytes. CONCLUSION: These results demonstrated pLXSN/tk-MCP-1 presented an enhanced antitumor effects on ovarian cancer by orchestration of immune responses.     

Monocyte chemoattractant protein-1 gene delivery enhances antitumor effects of herpes simplex virus thymidine kinase/ganciclovir system in a model of colon cancer

Suicide gene therapy using the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system is a well-characterized tool for cancer gene therapy; however, it does not yet exhibit sufficient efficacy to cure patients of malignancies. We have reported that adenovirally delivered monocyte chemoattractant protein (MCP)-1 augmented the antitumor effects of the HSV-tk/GCV system in an athymic nude mouse model. The current study, which uses an immunocompetent mouse model of colon cancer, was designed to evaluate the antitumor effects of MCP-1 gene delivery in conjunction with this suicide gene therapy system. Subcutaneous tumor foci were directly transduced with both recombinant adenoviruses (rAds) expressing an HSV-tk gene and either of the MCP-1, CD80 and LacZ genes, followed by GCV administration. The growth of tumors was markedly suppressed by codelivery of HSV-tk and MCP-1 genes, which was exclusively associated with the recruitment of monocytes/macrophages, T helper 1 (Th1) cytokine gene expression and cytotoxic activity of the splenocytes. Furthermore, the antitumor effects were more efficient than that obtained by the combination of HSV-tk and CD80 genes. These results suggest an immunomodulatory effect of MCP-1 in the context of suicide gene therapy of colon cancer via orchestration of innate and acquired immune responses.     

Enhanced anti-tumor effects of herpes simplex virus thymidine kinase/ganciclovir system by codelivering monocyte chemoattractant protein-1 in hepatocellular carcinoma.

The therapeutic efficacy of herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system in many types of tumors is unsatisfactory due to the insufficient spread of gene transfer and insufficient cell killing. In the current study, we investigated whether adenovirally delivered monocyte chemoattractant protein (MCP)-1 potentiates the antitumor effects of the HSV-tk/GCV system in hepatocellular carcinoma (HCC) cells. Subcutaneous tumor foci of the human HCC cell line, HuH7, established in athymic mice were directly transduced with a recombinant adenovirus (rAd) harboring an HSV-tk gene driven by a human alpha-fetoprotein promoter, followed by GCV administration. Subsequently, another rAd expressing MCP-1 under the universal CAG promoter was injected. The growth of tumors was markedly suppressed by codelivering HSV-tk and MCP-1 genes compared to that by either HSV-tk/GCV or MCP-1 delivery. In the tumor tissues, monocyte/macrophage infiltration was detected immunohistochemically. The antitumor effects of the rAd expressing MCP-1 were markedly reduced by the administration of carrageenan, a compound known to inactivate macrophage. These results indicate that adenovirally delivered MCP-1 enhanced the antitumor effects of the HSV-tk/GCV system synergistically by recruitment/activation of macrophages in tumor tissues, suggesting an effective immunotherapy for HCC and other lineages of tumors when used adjuvantly with a suicide gene.     

Membrane-bound form of monocyte chemoattractant protein-1 enhances antitumor effects of suicide gene therapy in a model of hepatocellular carcinoma

Suicide gene therapy using the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system combined with monocyte chemoattractant protein-1 (MCP-1) provides significant antitumor efficacy. The current study was designed to evaluate the antitumor immunity of a newly developed membrane-bound form of MCP-1 (mMCP-1) in an immunocompetent mouse model of hepatocellular carcinoma (HCC). A recombinant adenovirus vector (rAd) harboring the human MCP-1 gene and the membrane-spanning domain of the CX3CL1 gene was used. Large amounts of MCP-1 protein were expressed and accumulated on the tumor cell surface. The growth of subcutaneous tumors was markedly suppressed when tumors were treated with mMCP-1, as compared with soluble MCP-1, in combination with the HSV-tk/GCV system (P<0.01). The numbers of Mac-1-, CD4- and CD8a-positive cells were significantly higher in tumor tissues (P<0.05), and tumor necrosis factor (TNF) mRNA expression levels with mMCP-1 were almost five-fold higher than those with soluble MCP-1. These results indicate that the delivery of the mMCP-1 gene greatly enhanced antitumor effects following the apoptotic stimuli by promoting the recruitment and activation of macrophages and T lymphocytes, suggesting a novel strategy of immune-based gene therapy in the treatment of patients with HCC.     

Activation of antitumor immunity by intratumor injection of biological preparations

The antitumor effects of biological response modifiers (BRMs) in an experimental mouse model using a double grafted tumor system were analyzed. Some BRMs prevented metastases by utilizing the anti-tumor immunological cascade reactions, which activate macrophages in the body. The following BRMs were analyzed: PSK was a hot water extract of cultured mycelia from Coliolus versicolor and a protein bound beta-glucan. Lentinan was purified from fruit bodies of Lentinus erodes and is a beta-glucan. The agaricus preparation was extracted from fruit bodies of Agaricus blazei and a protein-bound alpha-, beta-glucan. The M2 fraction was extracted from mycelia of Tricholoma matsutake and was a protein bound alpha-glucan. M1 fraction was purified from mycelia of T. matsutake and was an alpha-glucan. PSK cured both primary and metastatic tumors in the double grafted tumor system. Lentinan did not inhibit the growth of either primary or metastatic tumors. Agaricus preparation cured a primary tumor and inhibited the growth of a metastatic tumor. The M2 fraction prepared from Matsutake inhibited the growth of both primary and metastatic tumors. The M1 fraction did not inhibit either primary or metastatic tumors. Immunosuppressive acidic protein (IAP) is produced by activated macrophages. The PSK, Agaricus preparation and M2 fraction of the Matsutake preparation induced IAP but the lentinan and M1 fraction did not.     

重组金葡菌肠毒素A的抗癌效应研究

目的: 金黄色葡萄球菌肠毒素A作为一种超抗原,其抑瘤活性一直受到关注,其直接应用于肿瘤治疗的报道较少,本研究对其抑瘤活性进行了分析.方法: 利用亲和层析纯化出重组SEA,注射接种了黑色素瘤的小鼠,观察其抑瘤效应.结果: 各组剂量的重组SEA均能有效抑制肿瘤的生长,其高、中、低剂量重组SEA的抑瘤率分别为79.3%、75.6%和73.8%,而原位注射(中剂量)的抑瘤率为90.6%.治疗小鼠的肿瘤组织出现大量的T细胞浸润;此外,SEA以免疫的形式刺激动物,能明显产生特异性抗体,并在一定程度上增强小鼠对肿瘤转移的抵抗力.结论: 重组SEA对小鼠黑色素瘤的能产生明显的抑制效应,尤其是原位注射,这为SEA的靶向治疗肿瘤奠定了基础.     

Enhanced antitumor effects of a bicistronic adenovirus vector expressing both herpes simplex virus thymidine kinase and monocyte chemoattractant protein-1 against hepatocellular carcinoma

The efficacy of the suicide gene therapy using the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system for the treatment of cancer is limited because of the insufficient gene transfer and the low killing activity. To enhance the antitumor activity, we determined whether recombinant adenovirus vector (rAd)s expressing both HSV-tk and monocyte chemoattractant protein-1 (MCP-1) genes could potentiate the destruction of hepatocellular carcinoma (HCC). The rAd Ad-tk-MCP1 harboring HSV-tk and MCP-1 genes in sequence under the universal CAG promoter was constructed with a bicistronic unit including the encephalomyocarditis virus-internal ribosomal entry site. The levels of HSV-tk expression and GCV-sensitive tumoricidal activity of Ad-tk-MCP1 were comparable to those of rAd expressing HSV-tk alone. The growth of subcutaneous tumors in athymic nude mice was markedly suppressed when tumors were treated with Ad-tk-MCP1 as opposed to another bicistronic vector Ad-MCP1-tk, rAd expressing either HSV-tk or MCP-1, or both of these vectors. The antitumor effects of Ad-tkMCP1 may be dependent on the activation of macrophages, since the recruitment of macrophages was observed tumor necrosis factor-alpha production was enhanced in the tumor tissue. Furthermore, the enhanced antitumor effect was abolished by inactivating macrophages with carrageenan treatment. These results demonstrated that a bicistronic rAd harboring both suicide and chemokine genes in sequence exerted the enhanced, macrophage-dependent, antitumor effects in a model of HCC and support the use of this strategy for the treatment of HCC.     

Antitumor effect of sFlt-1 gene therapy system mediated by Bifidobacterium Infantis on Lewis lung cancer in mice

Soluble fms-like tyrosine kinase receptor (sFlt-1) is a soluble form of extramembrane part of vascular endothelial growth factor receptor-1 (VEGFR-1) that has antitumor effects. Bifidobacterium Infantis is a kind of non-pathogenic and anaerobic bacteria that may have specific targeting property of hypoxic environment inside of solid tumors. The aim of this study was to construct Bifidobacterium Infantis-mediated sFlt-1 gene transferring system and investigate its antitumor effect on Lewis lung cancer (LLC) in mice. Our results demonstrated that the Bifidobacterium Infantis-mediated sFlt-1 gene transferring system was constructed successfully and the system could express sFlt-1 at the levels of gene and protein. This system could not only significantly inhibit growth of human umbilical vein endothelial cells induced by VEGF in vitro, but also inhibit the tumor growth and prolong survival time of LLC C57BL/6 mice safely. These data suggest that Bifidobacterium Infantis-mediated sFlt-1 gene transferring system presents a promising therapeutic approach for the treatment of cancer.     

Both the epitope specificity and isotype are important in the antitumor effect of monoclonal antibodies against Her-2/neu antigen

The Her-2/neu oncogene, which encodes a growth factor receptor, was implicated in the malignancy of human adenocarcinomas. Antibodies directed to this molecule have been previously shown to have an antitumor effect in vivo. In an attempt to understand the mechanisms of the antitumor activity, we generated 2 monoclonal antibodies (mAbs), HRO G1 and HRT G1, that recognize different epitopes on Her-2/neu. Both of the mAbs bound HER2/neu on the tumor surface, resulting in phosphorylation of HER2/neu. We also generated IgG2a and IgG2b mAbs from these 2 mAbs, respectively. The results of in vitro studies showed that these anti-Her-2/neu mAbs could not inhibit the growth of the tumor cells that express Her-2/neu molecules by themselves. However, in an antibody-dependent cellular cytotoxicity study using mouse splenocytes as effector cells, HRT mAbs had antitumor activities superior to those of HRO mAbs, indicating that the epitope specificity may also partake in antibody-dependent cellular cytotoxicity with antibody isotype. In a complement-dependent cytotoxicity study, the IgG2a and IgG2b mAbs showed stronger effects than IgG1 isotype mAbs irrespective of the epitope specificities. The results of in vivo studies also showed that HRT mAbs had superior antitumor activity to those of HRO mAbs. The antitumor activity was most prominent in the HRT G2b isotype among HRT mAbs. HRT G1 also showed a moderate antitumor effect, while HRT G2a showed only slight inhibition effect. These data indicate that both the epitope specificity and the differences in Fc region of mAbs could play important roles in the antitumor activities.