Hsp70-肿瘤抗原肽复合物防治小鼠黑色素瘤B16肺转移的作用

目的:探讨热休克蛋白70-肿瘤抗原肽复合物(Hsp70-antigen peptide complexes)对小鼠黑色素瘤B16转移的防治作用.方法:分别从小鼠腿部接种的B16实体瘤及小鼠肺B16转移灶提取混合抗原肽,体外与Hsp70结合制得复合物,此复合物免疫小鼠后用于预防或治疗经尾静脉接种转移至肺的B16黑色素瘤,观察其对肿瘤转移的防治作用.结果:Hsp70-肿瘤抗原肽复合物免疫后肺转移灶节结数显著减少(P＜0.01),体外脾细胞表现出对B16较高的杀伤率(P＜0.01);并对肺转移灶有显著的治疗作用(P＜0.01),而从B16实体瘤提取的混合抗原肽制得的复合物比从肺转移灶提取的混合抗原肽制得复合物有更好的治疗效果(P＜0.01),表现出体外脾细胞对B16更高的杀伤率(0.01＜P＜0.05).结论:Hsp70-肿瘤抗原肽复合物对肿瘤的转移有明显的防治作用,而从实体瘤提取的混合抗原肽比从转移灶提取的混合抗原肽更为有效.     

其它（051124～051144）

多次小剂量pEgr-IFN-γ基因-放射治疗的抑瘤效应及其机制的研究；Hsp70-肿瘤抗原肽复合物防治小鼠黑色素瘤B16肺转移的作用；CA72-4在10种恶性肿瘤患者血清中的临床界值；肿瘤库(用于分子生物学研究)的建立及管理；围手术期营养支持对外科病人预后的影响；     

转导B7-1基因消除IFN-γ对黑色素瘤转移潜力的增强作用

γ干扰素(IFN-γ)可通过增加MHCⅠ类分子或其它机制增强多种肿瘤的转移能力,而将T细胞共刺激分子B7基因导入肿瘤细胞能增强机体免疫系统对肿瘤的攻击。本文以Lipofectamine转染法将小鼠B7-1(mB7-1)基因导入B16黑色素瘤低转移株,导入空载体(只含neo基因)的B16细胞作对照。亲本B16细胞和基因转导细胞(B16-B7-1和B16-neo)经100U/ml IFN-γ预处理36小时后进行实验性肺转移试验,同时流式细胞分析细胞表面MHCⅠ类和Ⅱ类分子的表达。结果发现,IFN-γ预处理明显增强B16和B16-neo细胞的肺转移能力,而经IFN-γ预处理的B16-B7-1细胞转移能力并不增强,其实验性肺转移结节数与未经处理的对照组无差别。流式细胞分析显示IFN-γ预处理使B16、B16-neo和B16-B7-1三种细胞的MHCⅠ类(H-2K~b和H-2D~b)分子均明显增高,但IFN-γ增加B16-B7-1细胞MHCⅡ类分子I-A~b表达程度显著高于其它两种细胞。结果表明,转导B7-1基因可降低IFN-γ诱导的B16细胞转移能力,MHCⅡ类分子表达增高可能在其中起一定作用。     

重组人血管内皮抑素联合顺铂治疗小鼠肺转移癌实验研究

目的:探讨重组人血管内皮抑素(恩度)联合顺铂抑制小鼠肺转移癌的作用和机制。方法:取H22肝癌细胞株腹水瘤反复从小鼠尾静脉注入,建立高肺转移小鼠模型,随机分为4组:生理盐水、顺铂、恩度和顺铂与恩度联合治疗组,10只/组。从尾静脉接种后第7天腹腔内给药,1次/d,连用14 d,第21天处死,解剖出小鼠肺脏,称质量,计数肺转移结节数,并对肺转移瘤组织进行免疫组化染色,检测血管内皮生长因子(VEGF)表达,计数微血管密度。结果:生理盐水组、恩度组、顺铂组和联合治疗组肺转移率分别为100%、70%、60%和40%,肺转移结节数分别为(28.6±10.2)、(20.7±5.6)、(14.3±6.4)和(8.9±3.8)个,微血管密度计数为(31.4±3.1)、(24.6±5.9)、(21.2±4.7)和(15.2±3.1),各治疗组结果与生理盐水组比较差异均有统计学意义(P<0.05),联合组与顺铂组或恩度组比较也具有差异(P<0.05)。生理盐水组肺转移瘤组织的VEGF表达明显高于各治疗组(P<0.05)。结论:恩度单用或联合顺铂均能显著抑制H22肝癌肺转移组织的血管生成,降低了肺转移。     

低水平X线全身照射的抗肿瘤转移作用

我们利用血道转移模型及Lewis（LLC）肺癌自发转移模型研究了剂量率为12．5mGy／min，照射剂量为0、25、50、75、100mGyX线单次照射对肿瘤转移的影响。现将实验结果报告如下：将原代培养处于对数生长期的B16黑色素瘤细胞1×105／0．1ml经C57，BL／6／小鼠眼球后静脉于照后24hr注入，接种癌细胞后第18天处死小鼠，取肺计数肺表面黑色素瘤转移结节。单次X线照射0、25、50、75、100mGy小鼠肺转移结节数分别为102.68±61.45、69．29±38．00、45．38±33．11、36．26±27．28及46．85±41．13。结果显示，照射组小鼠的肺转移结节明显低于…     

Hsp70-H22肿瘤抗原肽复合物激活树突状细胞诱导抗肿瘤免疫的研究

目的　探讨通过树突状细胞 (DC)提呈途径降低肿瘤抗原肽用量的可行性 ,了解热休克蛋白 70 (Hsp70 )和抗原肽修饰DC作用的特点。方法　以Hsp70于体外结合抗原肽 ,并于体外修饰DC ,检测修饰后DC的代谢活性及分泌的细胞因子 ;比较修饰后DC和Hsp70 H2 2肽对淋巴细胞的激活作用 ;检测激活的淋巴细胞对H2 2瘤细胞的细胞毒作用以及注射DC和Hsp70 H2 2肽对小鼠肿瘤的抑制作用。结果　Hsp70结合 0 .15 μgH2 2肽可使 2× 10 5DC成熟 ,4× 10 3 成熟DC可激活 2× 10 6淋巴细胞 ;Hsp70结合 0 .0 0 3μg肽修饰的DC或Hsp70结合 0 .15 μg肽直接刺激 ,可激活相同数量的淋巴细胞 ,产生同样的杀瘤效果。激活DC后再回输的治疗方式与直接注射Hsp70 肽复合物的治疗方式相比 ,抗原肽的用量可以降低 5 0倍。正常肝组织来源的混合肽结合Hsp70后 ,不能使DC成熟 ,亦不能通过DC途径活化脾淋巴细胞。结论　DC提呈抗原肽激活淋巴细胞的途径能够有效降低Hsp70 肿瘤抗原肽复合物使用剂量。正常细胞的混合肽不能通过Hsp70和DC提呈激活淋巴细胞 ,其诱发自身免疫应答的可能性极低     

槲皮素联合苏拉明对肺腺癌小鼠移植瘤HIF-1α和P-选择素表达的影响

目的研究槲皮素联合苏拉明对小鼠肺腺癌移植瘤内缺氧诱导因子-1α(hypoxiainduciblefactor-1α,HIF-1α)和P-选择素(P-Selectin)表达的影响,及其抑制肿瘤生长和转移的作用机制。方法复制肺腺癌LA795细胞的T739小鼠移植瘤模型,将40只小鼠按随机数字表法分成对照组(A)、顺铂组(B)、槲皮素组(C)、苏拉明组(D)和槲皮素 苏拉明组(E)。实验3周后,处死全部小鼠,计算抑瘤率和肺转移发生率,计数各组小鼠肺表面转移结节数及肺表面结节转移抑制率。免疫组化和图象分析系统检测皮下移植瘤中HIF-1α和P-选择素表达并定量分析。结果B、C、D和E组肿瘤抑制率分别为23·03%、39·77%、34·40%和54·7%,A、B、C、D和E组肺表面转移结节数分别为11·00±1·927、8·75±1·642、6·00±1·600、3·00±2·000和1·37±1·187,HIF-1α灰度值分别为85·1±3·72、86·9±4·31、96·1±4·78、97·9±5·02和111·9±5·48,P-选择素灰度值分别为77·20±4·37、80·20±4·74、96·10±5·23、111·90±5·04和127·40±5·96。D组中肺表面转移结节数、皮下肿瘤内HIF-1α和P-选择素表达与A组相比明显下降,相反B组对此则无明显影响,E组则显著抑制肿瘤的生长和肺表面转移结节数,且具有协同作用。结论槲皮素和苏拉明对LA795肺腺癌移植瘤的生长和肺结节转移具有协同抑制作用,其机制与其抑制肿瘤内HIF-1α和P-选择素表达相关。     

B7-1基因转染小鼠EL-4淋巴瘤诱导带瘤宿主抗瘤效应的体内研究

本文研究了IL-2、IL-4、IL-6基因转染后B16黑色素瘤细胞表面MHCⅠ类抗原及ICAM-1的表达水平,并探讨了其在CTL诱导过程中的作用.结果表明,IL-2、IL-4、IL-6基因转染的B16黑色素瘤细胞表面MHCⅠ类抗原及ICAM-1表达均高于野生型B16黑色素瘤细胞及转染对照质粒的B16黑色素瘤细胞.体内接种后,小鼠脾脏CTL活性明显增强,CTL培养体系中IFN-γ、TNF-α的分泌水平也增高.在CTL诱导体系中加入抗ICAM-1单抗可以抑制CTL的活化,加入抗MHCⅠ类分子单抗后可使CTL的活化完全阻断.这提示细胞因子基因转染可能通过使肿瘤细胞表面MHCⅠ类抗原、ICAM-1的表达增加,从而增强瘤苗的免疫原性.     

共刺激分子4-1BBL和B7-1在人脑胶质瘤细胞中的表达

背景与目的：4-1BBL和B7-1为诱导和维持T细胞活化提供了重要的共刺激信号,目前被认为是提高抗肿瘤免疫的治疗靶点。本研究探讨4-1BBL和B7-1在7株胶质瘤细胞系表面的表达情况。方法：用流式细胞仪检测7株胶质瘤细胞株表面的共刺激分子4-1BBL和B7-1的表达,同时用MTT法分析胶质瘤细胞系对抗癌药物长春新碱（VCR）敏感性,并分析4-1BBL的表达与耐药性的相关性。结果：发现在所检测的胶质瘤细胞表面有不同程度的表达4-1BBL,但均不表达B7-1。其中T98G和MGR1细胞表面的4-1BBL表达〉30％,对VCR不敏感。UW28、SKMG1、MGR2、SF767、SKMG4细胞表面的4-1BBL表达〈10％。对VCR敏感。结论：本研究所检测的胶质瘤细胞均不表达共刺激分子B7-1。但有不同程度的表达4-1BBL,并且4-1BBL高表达的胶质瘤细胞对长春新碱敏感性差。     

烟曲霉醇联合环磷酰胺对小鼠LA795肺腺癌转移的抑制作用

背景与目的:血管生成抑制剂联合化疗药物治疗肿瘤成为目前研究热点之一。本研究旨在观察烟曲霉醇(fumagillol,TNP-470)联合环磷酰胺(cyclophosphamide,CTX)对肺腺癌小鼠异体移植转移的协同抑制作用,并初步探讨TNP-470抑制肿瘤转移的相关机制。方法:将40只接种高转移性LA795肺腺癌细胞的T739裸小鼠随机分成5组:对照组、溶剂组、TNP-470组(30mg/kg)、CTX组(40mg/kg)、联合组(TNP-47030mg/kg CTX40mg/kg)。实验3周后,处死全部小鼠。剥离皮下肿瘤称瘤重并计算抑瘤率;取出双肺观察表面肿瘤转移情况,计算肿瘤肺转移发生率,计数各组小鼠肺表面转移结节数及计算出肺表面结节转移抑制率。免疫组化和图像分析系统检测皮下移植瘤中微血管密度(microvesseldensity,MVD)、P-选择素表达并定量分析。结果:联合组抑瘤率(81.5%)明显高于其他各组(P<0.01),Q值等于1.21,说明两药合用具有协同作用。与对照组(12.13±4.02)相比,联合组(1.75±1.71)、TNP-470组(4.75±3.34)、CTX组(8.50±2.67)肺表面转移结节数明显下降;同时TNP-470组和联合用药组皮下肿瘤内MVD、P-选择素表达与对照组相比均下降,差异有显著性(P<0.01),而CTX组对此则无明显影响。结论:TNP-470与CTX对LA795肺腺癌的肺结节转移具有协同抑制作用;TNP-470抑制LA795肺腺癌转移与其抑制肿瘤内P-选择素表达有关。     

Effects of DL-alpha-difluoromethylornithine on the growth and metastasis of B16 melanoma in vivo

The effects of DL-alpha-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase, on the growth of experimental mouse B16-F10 melanoma cells were investigated. DFMO (3%) in drinking water was administered to B16-F10 melanoma-bearing mice. At 24 days, B16-F10 melanomas in DFMO-fed mice weighed 75% less than those in control mice (p less than 0.001). DFMO reduced putrescine and spermidine levels in B16-F10 melanoma by 98% and 84%, respectively, and prolonged the mean survival time from 25.9 +/- 1.2 to 35.7 +/- 2.2 days (p less than 0.001). The effects of DFMO on experimental metastasis were also investigated. DFMO treatment resulted in a significant decrease in pulmonary metastasis induced by i.v. injection of B16-F10 melanoma cells.     

Expression of co-stimulatory 4-1BB ligand induces significant tumor regression and protective immunity

Co-stimulatory molecules play an important role in initiating antitumor immune responses. Engineered tumor cells expressing co-stimulatory molecules have been used as cancer vaccines in both experimental tumor models and clinical trials. In this study, we cloned a cDNA gene coding for the mouse co-stimulatory molecule 4-1BBL by RTPCR. The expression vector pCI-4-1BBL was constructed by DNA recombinant technology and further transfected into a moderately immunogenic EL4 and a poorly immunogenic BL6-10 tumor cell line. Expression of the co-stimulatory molecule 4-1BBL is able to induce tumor regression of EL4/4-1BBL but not BL6-10/4-1BBL tumor cell line in syngeneic BALB/c mice. The tumor regression which is mainly mediated by CD8+ T cells further leads to protective immunity against the parental EL4 tumor. Our results thus indicate the potential utility of engineered tumor cells expressing co-stimulatory molecule 4-1BBL, especially in combination with other co-stimulatory molecules such as B7-1 in cancer vaccine.     

Theophylline administration markedly reduces hepatic and pulmonary implantation of B16-F10 melanoma cells in mice

Theophylline-treated B16-F10 melanoma cells show a lower experimental metastatic potential in vivo. To identify the possible mechanism(s) involved and on the basis of previous reports, we tested the induction of apoptosis in B16-F10 cells. Fluorescence activated cell sorter (FACS) analysis and p53 overexpression in theophylline-treated B16-F10 melanoma cells appeared to suggest enhanced cell death by apoptosis. The in vivo effects of orally administered theophylline in mice were investigated using different treatment schedules in mice that had undergone hepatic or pulmonary colonization with tumour cells. Mice received theophylline in their drinking water according to different protocols: (i) from 3 days before tumour cell inoculation until animal sacrifice ('early treatment'); (ii) from 3 days before until 3 days after tumour cell inoculation ('short treatment'); or (iii) from 3 days after tumour cell inoculation until animal sacrifice ('late treatment'). In the 'early treatment' group, the number of melanoma foci was reduced by 92.3% in the liver and 81.4% in the lung compared with control animals (P < 0.001). In the 'short treatment' group, there was an 80.2% and 72.2% reduction in liver and lung metastases, respectively (P < 0.001). In the 'late treatment' group, the inhibition of metastasis was 59.7% for liver and 45.3% for lung (P < 0.005). Survival studies showed that 50% of the 'early' theophylline-treated animals died 33.2 +/- 2.0 days after intrasplenic injection (control group: 23.1 1.8 days; P < 0.001) and 33.9 +/- 2.5 days after tail vein injection (control group: 24.1 +/- 1.4 days; P < 0.001). Taken together, these observations provide useful information for the potential clinical application of theophylline as a chemotherapeutic agent against malignant melanoma.     

NK and CD8+ T cell-mediated eradication of poorly immunogenic B16-F10 melanoma by the combined action of IL-12 gene therapy and 4-1BB costimulation

In previous reports, systemic administration of a stimulatory monoclonal antibody directed against the 4-1BB receptor had no effect on survival or tumor burden in mice inoculated with the poorly immunogenic B16-F10 melanoma. We combined IL-12 gene transfer with 4-1BB costimulation to explore a previously noted cooperative anti-tumor effect against this model tumor. We hypothesize that the innate immune response mediated by IL-12-activated natural killer (NK) cells initiates the activation of the immune system, leading to the priming of T cells, whereas 4-1BB costimulation enhances the function of primed tumor-specific T cells. The effect of the combination therapy on the growth of subcutaneous (s.c.) tumors and pulmonary metastasis was examined. The combination therapy significantly retarded the growth of subcutaneously-inoculated tumors, and 50% of tumor-bearing mice survived with complete tumor regression. In contrast, neither IL-12 gene transfer nor anti-4-1BB antibody administration alone was as effective. Enhanced CTL activity against both B16-F10 tumor cells and TRP-2-pulsed EL4 syngeneic tumor cells was observed in tumor-bearing animals treated with the combination therapy 2 weeks after treatment and, in long-term survivors from this combination therapy, at >120 days. In a pulmonary metastatic model, only the combination therapy generated significant protection against metastasis. In vivo depletion of NK or CD8(+) but not CD4(+) subsets eliminated the protective immunity. Furthermore, NK cell depletion significantly reduced both tumor-specific CTL activity and the number of tumor-specific IFN-gamma-producing cells, suggesting that this synergistic effect requires the participation of both NK and CD8(+) T cells.     

Expression of CXC chemokine receptor-4 enhances the pulmonary metastatic potential of murine B16 melanoma cells

The chemokine receptors CC chemokine receptor (CCR) 7 and CXC chemokine receptor (CXCR) 4 have been implicated in cancer metastasis. To evaluate whether CXCR4 is sufficient to increase tumor metastasis in an organ-specific manner, we transduced murine B16 melanoma cells with CXCR4 (CXCR4-B16) and followed the metastatic fate of the transduced cells in both i.v. and s.c. inoculation models of metastasis. CXCR4-B16 cells demonstrated marked increases (>10-fold) in pulmonary metastasis compared with vector (pLNCX2)-B16 after i.v. and s.c. inoculation of tumor cells. The increase in metastasis could be completely inhibited by T22, a small peptide antagonist of CXCR4. As early as 24 and 48 h after i.v. injection, CXCR4-B16 cells were significantly increased in the lung compared with control B16 cells by 5- and 10-fold (P < 0.05), respectively. CXCR4-B16 cells adhered better to both dermal and pulmonary microvascular endothelial cells relative to control B16 cells. Moreover, CXCL12 promoted the growth of CXCR4-B16 cells in vitro. Whereas expression of CXCR4 in B16 cells dramatically enhanced pulmonary metastasis, metastasis to the lymph nodes, liver, and kidney was rare. Immunohistochemical staining of both primary human cutaneous melanoma and pulmonary metastases revealed CXCR4 expression. Thus, CXCR4 plays a potentially important role in promoting organ-selective metastasis, possibly by stimulating tumor adhesion to microvascular endothelial cells and by enhancing the growth of tumor cells under stress.     

Antimetastatic and antitumor effects of benzoquinonoid AC7-1 from Ardisia crispa

An antimetastatic and cytostatic substance, termed AC7-1, was isolated from Ardisia crispa and identified as a benzoquinonoid compound, 2-methoxy-6-tridecyl-1,4-benzoquinone. It was originally characterized as the potent PAF (platelet-activating factor) receptor-binding antagonist with nonspecific antiplatelet effects on platelet aggregation induced by various agonists including PAF, ADP, thrombin and collagen. The nonspecific antiaggregatory properties of AC7-1 drew our interest given its possible relationship in integrin receptor-binding antagonistic activity. The integrin receptor plays an important role in metastasis and thrombosis as the cell surface transmembrane protein. Based on the aforementioned facts, the antimetastatic activities of AC7-1 were examined using various in vitro and in vivo metastasis assays. AC7-1 strongly blocked B16-F10 melanoma cell adhesion to extracellular matrix (ECM) and B16-F10 melanoma cell invasion. AC7-1 also remarkably inhibited pulmonary metastasis and tumor growth in vivo. AC7-1 inhibited B16-F10 melanoma cell adhesion to only specific synthetic peptides including RGDS. These findings suggest that antimetastatic activities of AC7-1 can be caused by blocking integrin-mediated adherence. We found AC7-1 to be a potential candidate for the development of a new antimetastatic drug.     

Constitutive Expression of the α4 Integrin Correlates with Tumorigenicity and Lymph Node Metastasis of the B16 Murine Melanoma

The lymphatic system plays a critical role in melanoma metastasis, and yet, virtually no information exists regarding the cellular and molecular mechanisms that take place between melanoma cells and the lymphatic vasculature. Here, we generated B16-F1 melanoma cells that expressed high (B16α₄+) and negligible (B16α₄-) levels of α₄ integrin to determine how the expression of α₄ integrins affects tumor cell interactions with lymphatic endothelial cells in vitro and how it impacts lymphatic metastasis in vivo. We found a direct correlation between α₄ integrin expression on B16-F1 melanoma cells and their ability to form adhesive interactions with monolayers of lymphatic endothelial cells. Adhesion of B16-F1 melanoma cells to lymphatic endothelial cells was mediated by the melanoma cell α₄ integrin binding to its counterreceptor, vascular cell adhesion molecule 1 (VCAM-1), that was constitutively expressed on the lymphatic endothelial cells. VCAM-1 was also expressed on the tumor-associated lymphatic vessels of B16-F1 and B16α₄+ tumors growing in the subcutaneous space of C57BL/6J mice. B16-F1 tumors metastasized to lymph nodes in 30% of mice, whereas B16α₄+ tumors generated lymph node metastases in 80% of mice. B16-F1 melanoma cells that were deficient in α₄ integrins (B16α₄-) were nontumorigenic. Collectively, these data show that the α₄ integrin expressed by melanoma cells contributes to tumorigenesis and may also facilitate metastasis to regional lymph nodes by promoting stable adhesion of melanoma cells to the lymphatic vasculature.     

Inhibitory effect of murine recombinant interferon (beta) on the pulmonary metastasis of B-16 melanoma

The antitumor effect of murine recombinant interferon (beta) [Mu-rIFN(beta)] was examined on artificial metastasis of B-16 melanoma in C57BL/6 mice. The numbers of pulmonary nodules were significantly decreased to 16.7 +/- 4.7 (P less than 0.01), 9.5 +/- 4.2 (P less than 0.01), 7.1 +/- 5.6 (P less than 0.01) in mice given 20,000 units of Mu-rIFN(beta) intraperitoneally (ip) 24, 6, and 3 hr before intravenous tumor inoculation, respectively, compared with the control group of mice (57.1 +/- 1.4), if B-16 melanoma cells (5 X 10(5] were intravenously injected 28 days before the experiment. In mice given 20,000 units of Mu-rIFN(beta) ip 24, 6, and 3 hr before the experiment, the natural killer (NK) activities of spleen cells against YAC-1 cells were elevated to 45.5 +/- 6.1%, 53.7 +/- 3.4%, 43.2 +/- 6.5%, respectively, compared with NK activities in control mice (20.3 +/- 3.1%). Similarly, NK activities against B-16 melanoma cells were also elevated in mice given Mu-rIFN(beta). Pretreatment with anti-asialo GM1 antibody and carrageenan reduced the inhibitory effect of Mu-rIFN(beta) on the pulmonary metastasis. In vitro colony inhibition of more than 50% was not observed even if B-16 melanoma cells were incubated with 100,000 units/ml of Mu-rIFN(beta). From these results, it can be concluded that the inhibition of pulmonary metastasis by Mu-rIFN(beta) is mediated via host defense mechanisms and that NK cells and macrophages are both important for the inhibition.     

Effect of splenectomy upon the growth of B16-F10 melanoma and its relation to the interferon system

The influence of splenectomy upon the growth of B16-F10 malignant melanoma and changes in interferon-synthesizing ability in mice were studied. Surgical stress alone temporarily diminished the ability of mice to respond to interferon induction by poly rIrC. Two weeks following the surgery, mock-splenectomized mice fully regained their interferon synthesis ability. However, this was not true in the case of splenectomized mice. They remained refractory to interferon induction. The removal of the spleen had no obvious effect on the rate of pulmonary metastasis in mice injected with B16-F10 malignant melanoma in relation to the mock-splenectomized or control mice. Mice that were splenectomized and inoculated with B16-F10 melanoma also remained refractory to interferon induction.     

Identification of an active site on the laminin alpha5 chain globular domain that binds to CD44 and inhibits malignancy

The laminin alpha5 chain is a component of laminin-10 (alpha5beta1gamma1) and -11 (alpha5beta2gamma1). In this study, we have screened 113 overlapping synthetic peptides from the laminin alpha5 globular domain (G-domain) for cell attachment activity with B16-F10 cells using peptide-coated dishes. Eleven attachment-active peptides were identified. In vivo experimental B16-F10 pulmonary metastasis and primary tumor growth assays found that 4 of the 11 peptides inhibited tumor metastasis and growth and increased apoptosis. These four peptides also blocked tumor cell migration, invasion, and angiogenesis. Two of the peptides were highly homologous and showed significant similarity to sequences in collagens. We sought to identify the B16-F10 cell surface receptors for each of the four active peptides using peptide affinity chromatography. Only one peptide recognized a cell surface protein. Peptide A5G27 (RLVSYNGIIFFLK, residues 2892-2904) bound a diffuse M(r) approximately 120,000-180,000 band that eluted with 2 m NaCl. Glycosidase digestion of the 2 m eluate yielded protein bands of M(r) 90,000 and 60,000 that reacted in Western blot analysis with antibodies to CD44. Immunoprecipitation of the A5G27-bound membrane proteins with various cell surface proteoglycan antibodies confirmed CD44 as the surface receptor for A5G27. Finally, attachment assays to A5G27 in the presence of soluble glycosaminoglycans (GAGs) identified the GAGs of CD44 as the binding sites for A5G27. Our results suggest that A5G27 binds to the CD44 receptor of B16-F10 melanoma cells via the GAGs on CD44 and, thus, inhibits tumor cell migration, invasion, and angiogenesis in a dominant-negative manner.