双歧杆菌脂磷壁酸对B16荷瘤小鼠NK细胞受体NKG2D及其配体的影响

目的探讨双歧杆菌脂磷壁酸（LTA）对黑色素瘤B16荷瘤小鼠NK细胞受体NKG2D及其配体的影响。方法将黑色素瘤B16细胞接种于C57BL／6小鼠皮下,待触及肿块后于荷瘤小鼠皮下注射双歧杆菌LTA。采用MTT、流式细胞术（FCM）、RT-PCR方法分别检测经双歧杆菌LTA处理后B16荷瘤小鼠NK细胞杀伤活性、NK细胞NKG2D受体蛋白表达以及肿瘤组织内Rae-1、H60 mRNA表达的变化。结果与对照组相比,经双歧杆菌LTA处理后,B16荷瘤小鼠的NK细胞杀伤活性增强（P〈0．05）,NK细胞受体NKG2D表达明显增加（P〈0．05）,肿瘤组织Rae-1、H60 mRNA表达上升（P〈0．05）,并具有浓度依赖性。结论双歧杆菌LTA能够增强B16荷瘤小鼠NK细胞的杀伤活性,其机制可能与上调NK细胞受体NKG2D的蛋白表达和肿瘤组织Rae-1、H60 mRNA的表达有关。     

敲低肿瘤细胞来源的颗粒体蛋白前体抑制C57BL/6J小鼠黑色素移植瘤的生长

颗粒体蛋白前体 (progranulin, PGRN)在多种肿瘤中过表达。但PGRN在黑色素瘤发生发展中的作用尚无报道。为探究PGRN在黑色素肿瘤中的作用,本研究采用CRISPR-Cas9基因编辑技术建立了稳定敲低PGRN的小鼠黑色素瘤B16细胞株B16-PGRNlow。MTS法和BrdU掺入结合流式细胞（计量）术分析证明,敲低PGRN不影响B16细胞的细胞周期和增殖。将B16-ctrl（对照）和B16-PGRNlow细胞分别皮下接种野生型（WT）和PGRN敲除（KO）的C57BL/6J小鼠,比较观察黑色素移植瘤体积大小。移植瘤形成20 d后,与B16-ctrl细胞接种的移植瘤比较,无论在WT还是在KO荷瘤小鼠,B16-PGRNlow形成的移植瘤体积明显减小（WT鼠：P<0.05;KO鼠：P<0.01）。然而,比较B16-PGRNlow或B16-ctrl在WT鼠与KO鼠形成的移植瘤体积大小,并无显著差异,提示B16肿瘤细胞PGRN而非宿主PGRN影响移植瘤的生长。流式细胞术分析显示,在荷B16-PGRNlow移植瘤的WT型小鼠脾和淋巴结中,CD4+、CD8+T细胞数（百分比）比荷B16-ctrl移植瘤的WT鼠脾和淋巴结的CD4+、CD8+T细胞数明显增多（P<0.05,P<0.01）,而在KO鼠却未见明显差异。上述结果证明,敲低肿瘤细胞PGRN可抑制黑色素移植瘤的生长。上述结果还提示,抑制PGRN在黑色瘤的表达可引起脾和淋巴结CD4+和CD8+T细胞增加,提高宿主的细胞免疫能力。其机制尚待进一步研究。本文的发现为PGRN作为黑色素瘤治疗的潜在靶点提供了新证据。     

乳腺癌中癌胚抗原（CEA）与p53、nm23—H1蛋白表达和部分病理指标的相关性研究

利用免疫组织化学方法检测了乳腺癌CEA与p53和nm23－H1蛋白的表达,对其相关性进行了研究,同时与其它病理指标亦进行了比较。结果：82 例乳腺癌中,CEA阳性67例（82％）,与p53蛋白的表达呈显的负相关（P＜0.05）,而与nm23-H1蛋白的表达则呈显的正相关（P＜0.05）;同时,CEA的表达与肿瘤的病理分级和体积显相关（P＜0.05）,即分级越高或肿瘤越大,CEA阳性表达率越低;而与患年龄、淋巴结转移和肿瘤坏死程度无关（P＞0.05）。综合分析推测：CEA可能是乳腺癌一种高分化肿瘤标志,并与肿瘤的浸润转移潜能有一定的关系,与其它指标联合应用在判断乳腺癌预后有一定的价值。     

过表达核糖核酸酶抑制因子通过调节ILK/PI3K/AKT信号途径抑制小鼠黑色素瘤B16-F10细胞体内外生长

核糖核酸酶抑制因子（ribonuclease inhibitor,RI）是胞浆内的一种酸性蛋白质.已有研究证明,RI与核糖核酸酶A（RNaseA）和血管生成素（angiogenin,ANG）结合可抑制其活性.本室前期实验证实,RI可有效抑制某些肿瘤的生长和转移. 然而,RI抑制肿瘤的分子机制尚不清楚. 本研究探讨RI对小鼠黑色素瘤B16-F10细胞生长和凋亡的影响及其机制. MTT法结合流式细胞术分析结果证明,RI基因稳定转染导致B16+F10黑色素瘤细胞S期阻滞,抑制B16-F10黑色素瘤细胞增殖. Annexin V/PI结合流式细胞术结果显示,RI过表达引起细胞凋亡.与此相一致,蛋白质印迹分析显示,过表达RI引起抗凋亡分子Bcl-2表达下调,而Bax上调,同时伴有Pro-casepase 3激活. C57BL/ 6小鼠移植成瘤实验显示,与对照相比,转染RI的B16-F10细胞形成的肿瘤重量显著减少,同时伴有肿瘤组织微血管密度降低.提示RI过表达能抑制微血管生成. 此外,体内外组织/细胞免疫化学和蛋白质印迹结果揭示,过表达RI可显著抑制整合素连接激酶(integrin-linked kinase,ILK)下游靶分子Akt和GSK-3β的磷酸化,并降低β-联蛋白的表达.研究结果证明,过表达RI可通过抑制ILK/ PI3K/AKT信号通路,促进细胞凋亡,引起S期阻滞,并抑制血管生成,从而显著抑制小鼠黑色素瘤B16-F10细胞在体内、外的生长.上述结果提示,RI可能是治疗黑色素瘤的有效分子靶点.     

VEGF—A和VEGF—C在皮肤恶性黑色素瘤表达的临床病理意义

目的：内皮细胞生长因子（Vascularendothelialgrowthfactor,VEGF）与恶性肿瘤转移密切相关,研究发现VEGF过度表达与恶性黑色素瘤转移有关,在本研究中通过研究VEGF在恶性黑色素瘤中的表达及与临床病理指标的相关性,为以VEGF为靶的抗转移治疗提供依据。方法：应用免疫组织化学技术检测恶性黑色素瘤中VEGF-A和VEGF-C表达,及与临床病理特点和生存状态的关系。结果：VEGF—A在皮肤恶性黑色素瘤中的阳性表达率是83．33％（30／36）,在色素痣中阳性表达率是15％（3／20）,两组间有显著性差异（P〈O．05）。VEGF—C在皮肤恶性黑色素瘤中的阳性表达率是88．9％（32／36）,在色素痣中阳性表达率是10％（2/20）,两组间有显著性差异（P〈0．01）。VEGF-A和VEGF—C表达与年龄、性别、肿瘤形态、肿瘤大小无显著关系,但与淋巴结转移和封闭血管环形成有关,VEGF-A和VEGF—C阳性病例淋巴结转移率和封闭血管环出现率显著高于VEGF-A和VEGF-C阴性病例。有统计学意义。对VEGF-A和VEGF-C表达与恶性黑色素瘤生存状态的关系分析显示,VEGF-A和VEGF-C表达阴性的病例的生存期和生存率均显著高于VEGF-A和VEGF-C表达阴性的病例,有统计学意义。结论：VEGF-A和VEGF-C表达与恶性黑色素瘤的淋巴结转移、血管形成和生存期相关,这两种蛋白过度表达反映黑色素瘤处于进展状态和预后差,可以作为黑色素瘤诊断、预后和复发预测的指标和靶向治疗的靶蛋白。     

重组FN多肽CH50抑制黑色素瘤B16细胞体内转移的研究

目的研究重组纤黏连蛋白（FN）多肽CH50对小鼠黑色素瘤B16细胞体内转移的影响,以探讨CH50多肽抑制肿瘤转移的可能分子机制。方法体外培养黑色素瘤B16细胞,用荧光染料CFSE标记,接种脾脏后24h取脾、肝、肺做冰冻切片,观察肿瘤细胞在3种组织中的侵袭情况。从脾脏接种B16细胞,建立体内肿瘤转移动物模型,采用基于流体动力学的体内基因转染方法于小鼠体内表达CH50多肽,RT-PCR检测CH50mRNA在肝组织的表达,Western印迹检测CH50多肽的表达。通过比较原位肿瘤结节及转移结节在数量、大小、分布上的差异及检测原位肿瘤组织中MMP-2、MMP-9表达差异,观察CH50多肽的治疗效果。结果注射24h后即可在脾脏形成荧光结节。pCH510质粒通过尾静脉注射后,可在肝组织中检测到CH50mRNA及CH50多肽的表达。从脾脏接种B16细胞后第14天可在脾脏形成原发肿瘤,至第35天肝脏表面已形成转移瘤结节,成功建立了体内器官问（脾转肝）肿瘤转移动物模型。体内转染表达CH50多肽能抑制肿瘤生长、侵袭和转移,抑制原位肿瘤结节中MMP-2、MMP-9的表达。结论CH50多肽可以通过对MMP-2、MMP-9蛋白表达的抑制作用来抑制黑色素瘤B16细胞的成瘤能力和体内侵袭、转移能力。     

骆驼蓬脂转移蛋白基因真核表达载体的构建及其体内外抗瘤效应的研究

目的:构建骆驼蓬脂转移蛋白(lipid transfer protein from Peganum harmala,PhLTP)基因真核表达质粒,并探讨其对黑色素瘤B16细胞在体内外的抗肿瘤作用。方法:将PhLTP基因亚克隆至pcDNA3.1上,获得重组质粒pcDNA3.1-PhLTP;用脂质体转染法将重组质粒及空载体外转染B16细胞,MTT检测其对B16细胞生长的影响。建立B16荷瘤小鼠模型,设重组质粒(pcDNA3.1-PhLTP)、空载(pcDNA3.1)、生理盐水和阳性药物(CTX)组,分别处理小鼠后测量各组肿瘤体积并称瘤重,计算抑瘤率。光镜观察鼠脾、肝等组织变化;免疫组织化学法检测各瘤体中PhLTP、血管内皮生长因子(VEGF)及碱性成纤维细胞生长因子(bFGF)的表达。结果:pcDNA3.1-PhLTP转染B16细胞72 h后,细胞增殖能力明显受到抑制(P0.01)。注射pcDNA3.1-PhLTP组的小鼠肿瘤生长速度明显减慢,肿瘤体积小于空载和生理盐水组(P0.05)。显微镜下可见重组质粒组肿瘤细胞有不同程度的点、片状坏死,而肝、肺等无明显病理损伤。重组质粒组肿瘤组织中有PhLTP蛋白的表达,且VEGF和bFGF的阳性表达指数都低于空载和生理盐水组(P0.01)。结论:成功构建了重组表达质粒pcDNA3.1-PhLTP,体内外实验结果显示其能有效地抑制B16细胞的生长,预示了该重组质粒在治疗黑色素瘤中的潜在应用价值。     

血清miR-200a和S-100B与妊娠期高血压疾病患者临床参数的关系及诊断价值分析

摘要 目的：检测妊娠期高血压疾病（HDCP）患者血清miR-200a和S-100钙结合蛋白B(S-100B)水平,分析其与HDCP患者临床参数的关系及对HDCP的诊断价值。方法：检测2017年2月至2019年2月我院收治的182例HDCP患者（观察组）和153例健康孕妇（对照组）血清miR-200a、S-100B水平,并比较不同年龄、入组时体质量指数（BMI）、分娩孕周、孕次、产次、病情程度、预后的HDCP患者血清miR-200a、S-100B水平差异。Pearson相关性分析血清miR-200a、S-100B及有关指标间的相关性。受试者工作特征（ROC）曲线分析血清miR-200a、S-100B水平诊断HDCP的价值。结果：观察组血清miR-200a、S-100B水平均高于对照组（P＜0.05）,血清miR-200a、S-100B水平随着病情加重而升高（P＜0.05）。血清miR-200a水平与HDCP患者年龄、入组时BMI、预后有关（P＜0.05）,血清S-100B水平与HDCP患者分娩孕周、预后有关（P＜0.05）。Pearson相关分析结果显示,HDCP患者血清miR-200a与S-100B、年龄、入组时BMI呈正相关（P＜0.05）,血清S-100B与分娩孕周呈正相关（P＜0.05）。ROC分析结果显示,血清miR-200a、S-100B水平诊断HDCP的曲线下面积（AUC）分别为0.743、0.721,灵敏度和特异度分别为72.93%、74.59%;72.00%、75.00%。结论：HDCP患者血清miR-200a、S-100B水平升高,两者与HDCP发病、进展和预后均存在密切关系。miR-200a、S-100B可能作为辅助HDCP诊断的生物学指标。     

内皮抑素抗黑色素瘤血管新生时间窗及最佳剂量的研究

目的:获取不同黑色素瘤发展阶段的荷瘤鼠的最佳治疗时间以及最佳用药量。方法:将肿瘤大小不等的雄性黑色素瘤荷瘤鼠进行内皮抑素分组对比治疗,在用药3、5、7天后处死荷瘤鼠,剥离瘤体,称瘤重,分析生长趋势,做病理切片并进行HE染色和免疫组化。在与对照组进行对照后,根据肿瘤的大小、恶性化的程度以及CD31和VEGF的表达情况,找出内皮抑素的用药最有效的治疗时间窗。然后通过进一步实验,在已经检测出的不同肿瘤大小的荷瘤鼠的恩度作用时间窗内,给荷瘤鼠使用用不同浓度梯度的药物,在不同肿瘤发展大小之后剥离瘤体,做与上述类似的操作并分析,确定在治疗时间窗时的恩度使用的最佳剂量。结论:5天为内皮抑素抗黑色素瘤血管新生时间窗,两个实验组中,中等剂量即15 mg/kg和20 mg/kg为恩度作用最佳剂量。     

小鼠囊胚与黑色素瘤细胞共培养模型优化

采用基因转染的方法,将EGFP(增强型绿色荧光蛋白)基因导入B16黑色素瘤细胞中,筛选出稳定表达绿色荧光蛋白的EGFP-B16细胞株,利用RT-PCR法检测细胞中EGFP基因的mRNA表达,流式细胞仪分析荧光细胞阳性率。利用EGFP-B16细胞与C57BL/6小鼠囊胚共培养,在激光共聚焦荧光显微镜下观察,比在普通倒置显微镜下观察B16细胞与C57BL/6小鼠囊胚共培养的模型能更加直观的表达胚胎与肿瘤的相互作用关系。     

人胃癌组织中乙酰肝素酶和S-100蛋白的表达及其意义

目的:探讨乙酰肝素酶和S-100蛋白在人胃癌组织中的表达及其意义。方法:根据胃癌的病理大体分型将40例胃癌组织分为早期组和晚期组。其中,早期组同时未伴有淋巴结转移,晚期组伴有淋巴结转移。采用光镜、透射电镜、原位杂交和免疫组化方法对这两组胃癌组织的超微结构,乙酰肝素酶和S-100蛋白表达进行检测。结果:早期组乙酰肝素酶阳性表达细胞较少,晚期组阳性细胞较多,二者数密度和面密度比较。具有统计学意义(P<0.01);早期组S-100蛋白阳性表达细胞较晚期组多,二者比较,具有统计学意义(P<0.01);电镜观察可见:在胃癌早期,淋巴细胞和树突状细胞浸润较多,树突状细胞突起与淋巴细胞相接触,基底膜基本完整。晚期,基底膜几乎消失。淋巴细胞和树突状细胞浸润较少,癌细胞穿基膜明显。结论:乙酰肝素酶和S-100蛋白的表达程度可作为判定胃癌的侵袭和转移的指标,对其预后的判断具有参考价值。     

Clinical-translational strategies for the elevation of Nm23-H1 metastasis suppressor gene expression

Interruption of the tumor metastatic process is a new, thought provoking molecular target for the treatment of cancer. The Nm23-H1 metastasis suppressor gene stands as a validated molecular target owing to its reduced expression in many aggressive human tumors, and the reduction in metastatic potential in vivo upon re-expression in multiple cell lines. Several compounds have been identified which elevate Nm23-H1 expression in vitro including indomethacin, γ Linolenic Acid, trichostatin A, 5-aza-deoxycytidine, and high dose medroxyprogesterone acetate. Using a model of lung metastatic colonization by MDA-MB-231 human breast carcinoma cells, we demonstrated that high dose MPA reduced the formation of overt lung metastases by 37–46% and those metastases that formed were statistically smaller. A Phase II clinical trial of high dose MPA, alone or in combination with metronomic chemotherapy has recently opened.     

Nm23-H1 regulates the proliferation and differentiation of the human chronic myeloid leukemia K562 cell line: A functional proteomics study

AimsNm23-H1 is a suppressor of metastasis that has been implicated in the regulation of proliferation and differentiation of hematopoietic cells, although specific mechanisms for Nm23-H1 have not been well-characterized. Our study is designed to further elucidate the role of Nm23-H1 in the human chronic myeloid leukemia K562 cell line.Main methodsIn this study we generated and selected two cell clone pools of human chronic myeloid leukemia K562 cells with up-regulated and down-regulated Nm23-H1 expression.Key findingsOur data show that knockdown of Nm23-H1 decreased proliferation and increased the percentage of cells arrested in the G0/G1 phase of the cell cycle. Correspondingly, K562 cells overexpressing Nm23-H1 were more proliferative. After treatment of these two cell types with phorbol 12-myristate 13-acetate (PMA) for 48 h, cells with reduced Nm23-H1 expression had a higher percentage of 8N ploidy and higher expression of CD41 than K562 cells overexpressing Nm23-H1. A functional proteomics analysis identified ten proteins, including ANP32A, Cdc42GAP, and the isoform 2 of SET, whose expression levels were significantly altered by down-regulation of Nm23-H1. In addition, cells with decreased levels of Nm23-H1 had significantly reduced expression of Cdc42 independent of treatment with PMA. The interaction of the endogenous Nm23-H1 and Cdc42 proteins has been further validated by reciprocal immunoprecipitations.SignificanceWe provide data that complement functional studies of Nm23-H1 in regulating hematopoietic cells, and address action mechanisms of Nm23-H1 that have not previously been reported.     

Nucleoside diphosphate kinase beta (Nm23-R1/NDPKbeta) is associated with intermediate filaments and becomes upregulated upon cAMP-induced differentiation of rat C6 glioma

Nucleoside diphosphate kinases (Nm23/NDPK) are enzymes functional in cell proliferation, differentiation, development, tumor progression, and metastasis. Nevertheless, no consensus exists about the molecular mechanism by which Nm23/NDPK isoforms exert their role in these processes. We investigated the expression of the rat Nm23-R1/NDPKbeta and Nm23-R2/NDPKalpha isoforms, homologues of the human Nm23-H1/NDPK A and Nm23-H2/NDPK B proteins, respectively, upon cAMP-induced differentiation of rat C6 glioma cells and demonstrated a differential interaction with intermediate filaments. Semiquantitative RT-PCR, immunoblotting, and flow cytometry showed a constitutive expression of both Nm23 isoforms. After induction of differentiation in C6 cells with cAMP analogs or isoproterenol, a dose-dependent 2- and 2.5-fold upregulation of the Nm23-R1 mRNA and protein, respectively, was observed. In contrast, the expression of Nm23-R2 remained unchanged. Localization of both isoforms with confocal laser scanning microscopy demonstrated a punctate reticular staining pattern for both Nm23 isoforms in the cytosol and processes of the cells which was particularly intense in the perinuclear region. In addition, while Nm23-R2 was colocalized and coimmunoprecipitated with vimentin in nondifferentiated cells, both isoforms were associated with GFAP in differentiated cells. The significance of these findings in relation to a possible function of Nm23 isoforms in cell proliferation, differentiation, and tumor-associated mechanisms is discussed.     

Discrimination between benign and malignant melanocytic skin lesions by multivariate analysis, quantitative S-100 immunohistochemistry, nuclear morphometry and DNA cytometry

OBJECTIVE: To determine whether combined quantitative immunohistochemistry of S-100, nuclear morphometry and DNA image cytometry improves discrimination between benign and malignant melanocytic skin lesions (MSLs). STUDY DESIGN: S-100 protein expression was measured in tissue sections of MSLs using an image cytometry system. Localized areas of high S-100 expression were used to identify regions in sequential, facing sections in which morphometric and cytometric features of nuclei, including DNA ploidy, were also measured. RESULTS: Malignant cases had significantly higher S-100 protein staining intensity, larger nuclei and greater DNA content (P < .05). High staining intensity for S-100 protein weakly correlated with variation in size of the mean nuclear area (P = .04) and DNA content (P = .03). Combining the features of nuclear area and DNA integrated optical density in areas of high-intensity staining for S-100 protein discriminated more accurately between 12 benign and 16 malignant areas than any of the features along (P = .0003). CONCLUSION: Combined multivariate quantitative immunohistochemical, morphometric and DNA cytometric analysis greatly improves discrimination between benign MSLs and malignant melanoma. Larger test sets are required to confirm the promising results of this initial study.     

Nm23-M5 mediates round and elongated spermatid survival by regulating GPX-5 levels

Nucleoside diphosphate (NDP) kinases are involved in numerous regulatory processes associated with proliferation, development, and differentiation. Previously, we cloned a new member of the NDPK family from mouse, Nm23-M5, which encodes a 211-amino acid protein and has 86% identity to the human Nm23-H5 [Hwang, K.C., Ok, D.W., Hong, J.C., Kim, M.O. and Kim, J.H. (2003) Cloning, sequencing, and characterization of the murine Nm23-M5 gene during mouse spermatogenesis and spermiogenesis. Biochem. Biophys. Res. Commun. 306, 198-207]. To better understand Nm23-M5 function, we generated transgenic mice with reduced Nm23-M5 levels in vivo using a short hairpin RNA (shRNA) knock-down system. Nm23-M5 expression was markedly reduced, as indicated by Northern and Western blot analysis. Nm23-M5 shRNA transgenic mice exhibited reduced numbers of haploid cells. Furthermore, the antioxidant enzyme glutathione peroxidase 5 (GPX-5) is regulated by Nm23-M5 at the level of both expression and activity. These results reveal that expression of Nm23-M5 plays a critical role in spermiogenesis by increasing the cellular levels of GPX-5 to eliminate reactive oxygen species.     

Regulation of Nm23-H1 and cell invasiveness by Kaposi's sarcoma-associated herpesvirus

The Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma (KS), and the induction of an invasive cellular phenotype by KSHV following de novo infection is an important pathogenic component mediating tumor progression. The metastasis suppressor gene known as Nm23-H1 regulates tumor cell invasiveness, but whether KSHV itself regulates Nm23-H1 expression or subcellular localization, and whether this impacts cell invasiveness, has not been established. We found that KSHV increases expression and nuclear translocation of Nm23-H1 and that nuclear translocation of Nm23-H1 is regulated by the KSHV-encoded latency-associated nuclear antigen (LANA). Moreover, activation of the Ras-BRaf-MAPK (mitogen-activated protein kinase) signal transduction pathway, secretion of promigratory factors associated with this pathway, and cell invasiveness are dependent on KSHV regulation of Nm23-H1. Finally, induction of cytoplasmic overexpression of Nm23-H1 using a pharmacologic inhibitor of DNA methylation reduced KSHV-associated Ras-BRaf-MAPK pathway activation and suppressed KSHV-induced invasiveness. These data provide the first evidence for KSHV regulation of Nm23-H1 as a mechanism for KSHV induction of an invasive cellular phenotype and support the potential utility of targeting Nm23-H1 as a therapeutic approach for the treatment of KS.     

The Association of the Nm23-M1 Protein and β-Tubulin Correlates with Cell Differentiation

The Nm23 protein is a nucleoside diphosphate kinase (NDPK) and is thought to play a critical role in metastatic behavior. It has been reported that a NDPK activity is present in microtubules assembled in vitro. Since microtubule assembly is determinant in cell growth and differentiation, we investigated whether Nm23-M1 forms molecular complexes with β-tubulin in murine cells either actively proliferating or differentiating. For this purpose a polyclonal antibody against the GST-Nm23-M1 fusion protein was generated and employed to detect Nm23-M1/β-tubulin complexes in murine tumor cells derived from the Lewis lung carcinoma (3LL) and in undifferentiated and differentiated myogenic cells (C2C12). Immunoblotting and immunoprecipitation experiments performed using the anti-fusion protein antibody demonstrated that the Nm23-M1 protein is detectable in in vitro tumor cell lines and in in vivo primary tumors but not in spontaneous lung metastases. These data are in good agreement with data previously reported. Immunoprecipitation experiments demonstrated that the Nm23-M1 protein forms complexes with β-tubulin in in vitro tumor cell lines, but not in primary tumors. Furthermore, the Nm23-M1 protein forms complexes with β-tubulin in myogenic cells prior to and after differentiation. Interestingly, however, the level of the Nm23-M1/β-tubulin complexes is remarkably increased in differentiated myotubes. In conclusion, the results indicate that the Nm23-M1 protein forms molecular complexes with β-tubulin and that the number of complexes increases during the differentiation process of murine cells.