Ad-ING4对人前列腺癌细胞PC-3体内外抑癌效应的研究

背景与目的：腺病毒作为载体已被广泛用于肿瘤的基因治疗。ING4是生长抑制因子家族中的一个成员,是一种潜在的抑癌基因。本研究旨在探讨腺病毒介导的人ING4基因（Ad-ING4）对人前列腺癌细胞PC-3的体内外抑癌效应及其分子机制。方法：将扩增的Ad-ING4重组腺病毒感染PC-3细胞,用RT-PCR法检测ING4在PC-3细胞中的转录;MTT法检测ING4基因对PC-3细胞增殖的影响：流式细胞术和Hoechst33258染色法检测细胞凋亡的变化;半定量RT-PCR法检测ING4基因的表达对PC．3细胞中的bcl-2、bax、p53和caspase-3凋亡相关基因表达的影响。用Ad-ING4重组腺病毒在裸鼠PC-3移植瘤的瘤体内注射治疗,观察肿瘤生长变化,15d后处死裸鼠,摘除瘤体,称瘤重;用免疫组化法检测瘤组织中Bcl-2、Bax、Caspase-3和CD34蛋白的表达。结果：腺病毒介导的人ING4基因在PC-3细胞中成功转录,明显抑制PC-3细胞增殖,上调p53、bax、caspase．3基因表达和下调bcI-2基因表达,并诱导细胞凋亡。Ad-ING4重组腺病毒能显著抑制裸鼠PC-3移植瘤的生长,瘤重的抑制率达37％,与空病毒载体Ad-GFP组和细胞对照PBS组比较差异有统计学意义（P〈0．05）;免疫组化结果显示Ad-ING4重组腺病毒能明显上调Bax和Caspase-3蛋白的表达水平,下调Bcl-2和CD34蛋白的表达水平。结论：腺病毒介导的ING4基因在体内外均可明显抑制人前列腺癌细胞PC-3的生长,诱导其凋亡,其机制可能是上调P53、Bax、Caspase-3蛋白和下调Bcl-2蛋白表达水平。     

JNJ-26481585对人肺腺癌培美曲塞耐药裸鼠移植瘤的抑制作用及其机制探讨

目的:探讨JNJ-26481585对人肺腺癌培美曲塞耐药裸鼠移植瘤的抑制作用及其抗癌机制。方法:构建人肺腺癌A549/培美曲塞耐药细胞（A549/PEM）的移植瘤裸鼠模型,随机分为模型组、培美曲塞组、JNJ组、联合组（培美曲塞+JNJ）,第28天治疗观察结束时处死裸鼠,剥离肿瘤组织标本待测。测定4组裸鼠肿瘤体积与体质量,计算抑瘤率,观察各治疗组药物对荷瘤裸鼠的毒副反应,TUNEL方法检测4组移植瘤细胞凋亡情况的差异, qRT-PCR检测4组移植瘤细胞FAM96A、Bax、Bcl-2基因mRNA表达水平差异,Western blot检测4组移植瘤细胞FAM96A、Bax、Bcl-2蛋白表达的差异。结果:联合组的肿瘤体积、体质量低于JNJ组,JNJ组的肿瘤体积、体质量低于培美曲塞组,联合组的抑瘤率高于JNJ组,JNJ组抑瘤率高于培美曲塞组(均P<0.05)。联合组的细胞凋亡率高于JNJ组,JNJ组细胞凋亡率高于培美曲塞组(均P<0.05)。联合组肿瘤细胞的FAM96A、Bax表达水平高于JNJ组, JNJ组FAM96A、Bax表达水平高于培美曲塞组,联合组Bcl-2表达水平低于JNJ组,JNJ组Bcl-2表达水平低于培美曲塞组(均P<0.05)。联合组与单药组比较,血细胞计数均明显下降,肝功能指标均明显升高（P<0.05）;培美曲塞组与JNJ组比较,血细胞及肝功能指标无统计学差异(P>0.05)。结论:JNJ-26481585可通过激活抑癌基因FAM96A的表达、上调Bax表达及下调Bcl-2的表达来促进癌细胞凋亡,逆转肺腺癌对培美曲塞的耐药性,并与培美曲塞协同发挥抗癌作用。     

树突状细胞瘤内注射联合放疗对小鼠肾癌组织Bcl-2和Bax表达的影响

目的:研究放疗增强树突状细胞免疫治疗小鼠肾癌的作用与机制。方法:应用Ren-ca肾癌细胞制作BALB/c小鼠皮下移植瘤模型,分为对照组、单纯放疗组、单纯DC组和DC联合放疗组共4组进行治疗。皮下荷瘤的BALB/c小鼠,在接种瘤细胞后第12~16天,连续5d接受肿瘤局部放射治疗,7Gy6MeV/次,并于第11、15、19和22天分别4次在肿瘤部位直接注射未负载肿瘤抗原的DC细胞,1×106/次,第28天处死小鼠。检测各组肿瘤生长速度和质量。利用免疫印迹法(Westernblot法)检测肿瘤组织的相关凋亡蛋白表达。结果:接受不同治疗的小鼠体内肿瘤质量明显不同,未治疗组为(5·3±0·8)g,单纯DC组(4·5±0·7)g,单纯放疗组(2·8±0·3)g,DC联合放疗组(1·1±0·7)g,经Wilcoxon-Mann-Whitney秩和检验,DC联合放疗组与单纯治疗组和对照组之间差异均有统计学意义,P<0·01。DC联合放疗组肿瘤组织中抗凋亡蛋白Bcl-2表达下调,促凋亡蛋白Bax表达上调。结论:瘤内注射DC联合放疗比单一方法明显提高抑制Renca肾癌细胞在BALB/c小鼠的生长,其增效作用涉及肿瘤细胞的凋亡机制。     

125I粒子植入联合放射治疗对A549裸鼠移植瘤生长及HIF-1表达的影响

 【摘要】　目的　研究125I粒子植入联合放射治疗对A549裸鼠移植瘤生长及乏氧诱导因子-1α（HIF-1α）表达的影响。方法　应用裸鼠建立肺腺癌A549移植瘤模型,待平均瘤体积达到（300±50）mm3时40只裸鼠随机分成4组（每组10只）,对照组 ：不做任何处理;单纯放射治疗组 ：第1天予单次外照射,6 MV-X线,10 Gy;125I粒子植入组 ：肿瘤中心植入1枚活度27.75 MBq的125I粒子;放疗加125I粒子植入组（联合治疗组）：第1天在肿瘤中心植入1枚活度27.75 MBq的125I粒子的同时予单次外照射,6MV-X线,10 Gy。治疗后共观察15 d,绘制肿瘤生长曲线,测量各组肿瘤体积并计算抑瘤率,分别用免疫组织化学及蛋白免疫印迹方法测定HIF-1α的表达。结果　治疗第8天起,瘤体积联合治疗组（209±21）mm3与对照组（322±30）mm3相比差异有统计学意义（t＝46.4,P＝0.000）。第15天后,单纯放射治疗组、125I粒子植入组、联合治疗组抑瘤率依次为45.9 %、44.4 %、69.4 %,联合治疗组与单纯放射治疗组比较差异有统计学意义（t＝52.03,P＝0.000）,联合治疗组与125I粒子植入组比较差异有统计学意义（t＝53.98,P＝0.000）,单纯放射治疗组和125I粒子植入组相比,差异无统计学意义（t＝0.591,P＝0.596）。联合治疗组与其他各组相比HIF-1α改变差异均无统计学意义（P＝0.342）。结论　放射治疗联合125I粒子植入能显著抑制转染人类肺腺癌A549裸鼠移植肿瘤的生长,但未抑制肿瘤细胞HIF-1α的表达。     

吴茱萸碱联合放射治疗对舌鳞癌细胞Tca-8113裸鼠移植瘤生长的抑制作用

目的:研究吴茱萸碱(evodiamine,EVO)联合射线对舌鳞癌细胞Tca-8113裸鼠移植瘤生长的抑制作用。方法:建立舌鳞癌Tca-8113细胞裸鼠皮下移植瘤模型16只,随机分为空白对照组、EVO组、放射组及联合组,观察并绘制肿瘤生长曲线图,计算肿瘤抑制率;肿瘤组织通过常规苏木精-伊红染色行病理学检查;免疫组织化学法检测移植瘤组织中Ki67、Bax和Bcl-2表达情况;透射电子显微镜观察细胞凋亡形态。结果:治疗第12天起,联合组肿瘤体积与其余各组相比,明显减小(P<0.05);治疗结束时,EVO组、放射组和联合组的抑瘤率分别为15.15%、43.29%和63.20%。联合组Ki67和Bcl-2表达水平较EVO组和放射组下降,Bax表达水平增高(P<0.05)。联合组坏死细胞数增多,且细胞呈典型凋亡特征。结论:放疗联合EVO能抑制舌鳞癌Tca-8113细胞裸鼠移植瘤的生长,可能与Ki67和Bcl-2表达下调以及Bax表达上调有关。     

健择联合电子线照射对人胰腺癌裸鼠移植瘤凋亡的影响

目的探讨健择联合电子线外照射对人胰腺癌细胞株(panc-1)裸鼠移植瘤细胞凋亡的作用。方法建立人胰腺癌panc-1裸鼠移植瘤模型,36只裸鼠随机分为6组：对照组（A组）、单纯放疗组(B组)、健择25mg/kg组(C组)、健择50 mg/kg组(D组)、联合治疗1组（E组）、联合治疗2组（F组）。A组裸鼠尾静脉注射0.9%氯化钠溶液,B组荷瘤鼠背部肿瘤局部以6MeV电子线照射。C、D组分别以25 mg/kg、50 mg/kg健择裸鼠尾静脉注射,E、F组分别以25、50 mg/kg健择裸鼠尾静脉注射加背部肿瘤6MeV电子线照射。采用TUNEL法检测凋亡指数（AI）,免疫组织化学检测凋亡抑制蛋白Bcl-2、凋亡相关蛋白Bax的表达情况。结果干预组较对照组肿瘤细胞凋亡明显增加,干预组各组之间凋亡指数比较差异有统计学意义（P＜0.05）。免疫组织化学结果示：与对照组比较,干预各组均可不同程度下调Bcl-2蛋白表达,Bax蛋白表达上调（P＜0.05）,联合治疗组与其他各组比较,Bcl-2蛋白表达降低,Bax蛋白表达升高,差异均有统计学意义（P ＜0.05）。结论健择联合电子线对人胰腺癌移植瘤的凋亡有促进作用。     

左旋棉酚对小鼠宫颈癌移植瘤细胞凋亡的影响及其机制

目的探讨左旋棉酚［(-)-gossypol,LGP］对顺铂诱导小鼠宫颈癌移植瘤凋亡的影响及可能的作用机制。方法建立小鼠宫颈癌U14细胞皮下移植瘤模型,将60只小鼠按随机原则分为左旋棉酚组、顺铂(Cisplatin,DDP)组、左旋棉酚+顺铂(LGP+DDP)组及模型对照（Model Control）组4组,用药干预8天后采用电子天平称量瘤重并计算抑瘤率;采用TUNEL法检测各组瘤组织的凋亡情况;采用免疫组织化学法检测各组肿瘤组织中Bcl-2、Bax和P-gp蛋白的表达水平。结果各干预组小鼠移植瘤瘤重均低于Model组,其中LGP+DDP组瘤重最低,其次为DDP组(P＜0.01);各组移植瘤组织内AI均高于Model组（P＜0.05）,且LGP+DDP组最高（P＜0.01）;含LGP组移植瘤组织内P-gp、Bcl-2蛋白的表达降低（P＜0.05）, Bax蛋白的表达升高（P＜0.05）,Bax/Bcl-2比值升高,LGP+DDP组的上述作用明显优于单药组（P＜0.01）;相关性分析表明P-gp蛋白的表达量与Bcl-2的表达量呈正相关,与Bax的表达量呈负相关（P＜0.01）。结论 LGP能抑制小鼠宫颈癌移植瘤的生长,且与DDP联合后抑制作用更显著;其可能的机制:LGP可能是通过下调Bcl-2、上调Bax蛋白诱导小鼠宫颈癌细胞凋亡,降低P-gp蛋白的表达,增加肿瘤组织对DDP的化疗敏感度。     

重组人血管内皮抑素联合重组人P53腺病毒对裸鼠乳腺癌移植瘤的抑制

摘 要 目的: 探讨重组人血管内皮抑素（recombinant human endostatin,ES）联合重组人P53腺病毒（rAd/P53）对乳腺癌细胞MCF7裸鼠移植瘤的抑制作用。方法：建立裸鼠荷人乳腺癌模型，随机分为对照组、ES组、rAd/P53组和两药联合组,分别给予相应治疗；观察肿瘤生长，免疫组化法检测肿瘤组织微血管密度（microvessel density，MVD）和血管内皮生长因子（vascular endothelial growth factor, VEGF）的表达。结果：各治疗组均可明显抑制移植瘤生长， ES组、rAd/P53组和联合用药组的抑瘤率分别为51.67％、48.74％和75.54％，联合用药组抑瘤作用最为显著（P<0.05）。对照组、ES组、rAd/P53组与联合用药组的移植瘤组织MVD分别为31.17±2.48、20.33±4.84、22.33±3.88及12.50±2.74，VEGF 表达H评分分别为45.33±589、35.83±546、33.67±4.80及22.33±4.41，联合用药组的MVD和VEGF表达显著低于其余各组（P<0.01）。 结论：重组人ES联合rAd/P53治疗可显著抑制裸鼠乳腺癌移植瘤的生长及微血管生成。     

槲皮素联合顺铂对肺腺癌小鼠移植瘤Bcl-2和Bax表达的调控及意义

目的：观察槲皮素联合顺铂对肺腺癌LA795细胞的T739小鼠移植瘤的抑制作用，检测移植瘤中Bcl-2和Bax的表达水平及肿瘤细胞凋亡指数，探讨其作用机制。方法：将32只接种了LA795肺腺癌细胞的T739小鼠随机分成对照组（A组）、顺铂组（B组）、槲皮素组（C组）、槲皮素＋顺铂组（D组）。用药16d后，观察肿瘤生长情况，接种后24d活杀各组小鼠，移植瘤标本称瘤体质量和测量体积，免疫组织化学和图像分析系统定量检测肿瘤组织的Bcl-2和Bax表达，原位凋亡TUNEL法检测肿瘤细胞凋亡指数。结果：B、C、D各用药组肿瘤的生长受到明显抑制，瘤体质量明显低于A组，其抑瘤率分别为38．57％、26．03％和51．58％，联合用药组抗瘤作用进一步增强。Bcl-2表达在A组高于B、C、D组，Bax表达在A组明显低于B、C、D组，各用药组与对照组相比差异均有统计学意义（P〈0．05或P〈0．01）；肿瘤细胞的凋亡指数在各用药组都比对照组明显提高，差异有统计学意义（P〈0．01）。结论：槲皮素联合顺铂可明显抑制肺腺癌细胞在小鼠体内的生长，其作用机制可能是通过调控肿瘤中Bcl-2和Bax的表达，从而抑制细胞增殖和促进细胞凋亡。     

吉西他滨对人胰腺癌裸鼠移植瘤的放疗增敏作用

目的：评价吉西他滨对人胰腺癌移植瘤的放疗增敏作用。方法：建立人胰腺癌裸鼠移植瘤模型,36只裸鼠随机分为6组：对照组（A）、单纯放疗组（B）、吉西他滨25mg/kg组（C）、吉西他滨50mg/kg组（D）、吉西他滨25mg/kg＋放疗组（E）、吉西他滨50mg/kg＋放疗组（F）。对照组予腹腔注射生理盐水,单纯放疗组荷瘤鼠背部肿瘤局部以6MeV电子线照射。C、D组分别以25mg/kg、50mg/kg吉西他滨腹腔注射,E、F组分别以25mg/kg、50mg/kg吉西他滨腹腔注射加背部肿瘤6MeV电子线照射。然后每两天测量肿瘤的长短径、比较各组的瘤体积、肿瘤生长延缓天数、抑瘤率,利用增敏系数（EF）评价吉西他滨的增敏作用。结果：与对照组比较,25mg/kg、50mg/kg单剂量吉西他滨对移植瘤生长有明显抑制作用（P〈0.01）;两组剂量吉西他滨联合放疗组局部肿瘤生长受到明显抑制,抑瘤率分别为88.22%、91.23%,明显高于单纯放疗组（44.11%,P〈0.05）和吉西他滨两个剂量单药组（72.88%、77.53%,P〈0.05）。联合组（E、F组）肿瘤生长延缓天数（瘤体积增长2倍）分别为9、15天,高于单纯放疗组（4天,P〈0.05）和吉西他滨两个剂量单药组（4、4天,P〈0.05）。结论：吉西他滨可显著增强人胰腺癌裸鼠移植瘤放射治疗敏感性。     

The insulin-like growth factor system as a therapeutic target in colorectal cancer.

The purpose of this review is to examine recent evidence that investigates the role of the insulin-like growth factor (IGF) system in colorectal cancer. We concentrate on the evidence that makes the case for the investigation of strategies that might be used to disrupt the IGF system in prevention and treatment. Even though the weight of evidence suggests that components of the IGF system may be appropriate targets, there are a lack of studies that make a systematic characterisation of all the system components in human colorectal cancer. It is anticipated that this information, and the new therapeutic molecules which follow, will impact on the prevention and treatment of patients with this disease.     

Combination therapy of imatinib mesylate and interferon-alpha demonstrates minimal activity and significant toxicity in metastatic renal cell carcinoma: results of a single- institution phase II trial

Background

Renal cell carcinoma (RCC) is characterized by increased expression of vascular endothelial growth factor and platelet-derived growth factor (PDGF)-β, both of which contribute to its angiogenic phenotype. Interferon-α (IFN-α) improves survival in patients with metastatic RCC, perhaps partly because of its antiangiogenic properties. Imatinib mesylate inhibits PDGF-mediated signal transduction and might thus have antiangiogenic activity as well.

Patients and Methods

Patients with metastatic RCC were treated with IFN-α (9 × 10⁶ IU subcutaneously 3 times weekly) and oral imatinib mesylate (600 mg daily starting on day 8). Therapy was continuous, and response was evaluated at 8-week intervals using the Response Evaluation Criteria in Solid Tumors. Baseline plasma PDGF-AA, PDGF-AB, and PDGF-BB levels were obtained.

Results

Between January 2003 and January 2005, 17 patients were treated. One patient (6%) had a partial response, 4 (24%) had stable disease, 7 (41%) had progressive disease, and 5 (29%) were unevaluable because of early withdrawal secondary to toxicity. Median time to progression (TTP) using the Kaplan-Meier method was 8 weeks, and median overall survival was 17.8 months. Six patients (35%) withdrew from therapy because of toxicity, and 9 patients (53%) experienced ≥ 1 grade 3/4 toxicity. Platelet-derived growth factor AA, AB, and BB plasma levels did not correlate with TTP or overall survival.

Conclusion

Based on a response rate of only 6%, a median TTP of 2 months, and significant toxicities, further study of IFN-α in combination with imatinib mesylate is not recommended in patients with metastatic RCC.     

Expression of Epidermal Growth Factor, Transforming Growth Factor-α and Their Receptor Genes in Human Gastric Carcinomas; Implication for Autocrine Growth

The expressions of mRNA for epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and EGF receptor (EGFR) genes were examined in 7 human gastric carcinoma cell lines and 15 gastric carcinoma tissues and the corresponding normal mucosas. All of the gastric carcinoma cell lines expressed mRNA for EGFR and TGF-α genes. TMK-1 and MKN-28 cells also expressed EGF mRNA. Production of EGF, TGF-α and EGFR protein by gastric carcinoma cell lines was also confirmed by EGF and TGF-α specific monoclonal antibody binding. As for surgical specimens, EGFR and TGF-α mRNA were detected at high levels in all the tumor tissues. Interestingly, EGF mRNA was detected in 5 (33.3%) of the 15 gastric carcinomas but it was not detected in normal tissues. Moreover, anti-EGF and anti-TGF-α monoclonal antibodies inhibited the spontaneous ³H-TdR uptake by gastric carcinoma cells. These results suggest that EGF and/or TGF-α produced by tumor cells act as autocrine growth factors for gastric carcinomas.     

The controversial role of placental growth factor in tumor growth

The significance of placental growth factor (PlGF) in tumor growth is still a matter of debate. Depending on the model, PlGF overexpression has been shown to result in tumor growth promotion or inhibition. This review article summarizes the most relevant literature data concerning this still unsolved important question.     

Estimate of tumor growth time for breast cancer local recurrences: rapid growth after wake-up?

To obtain an estimate of the subclinical tumor growth time (TGT) for breast cancer, a series of 31 patients with local recurrence as first event after mastectomy was evaluated. The recurrence diameter was measured, and the minimum growth rate (mGR) consistent with the sequence no detection at the preceding physical examination recurrence of diameter Dr was obtained. The growth rate for uninterrupted exponential growth from surgery (GRu) was also calculated. mGR was significantly higher than GRu (p < 0.0001), and unrelated to the recurrence-free survival (RFS). Therefore, starting points of local recurrence growth curves had to be set at times variously delayed after mastectomy. The estimate of the delay lower limit (mD), which was obtained from mGR and GRu, showed a strong linear correlation with RFS (R=0.984; p < 0.0001). From the regression equation, TGT for local recurrences could be estimated at 30 ± 8 weeks or less. These findings support the concept that the lag time between surgical treatment of breast cancer and clinical evidence of local recurrence may be explained by a period of tumor dormancy followed by a tumor growing phase. The TGT estimate is remarkably shorter than previously believed and could considerably change the current picture of breast cancer history.     

Intussusceptive microvascular growth in tumors

Intussusception is an alternative to the sprouting mode of angiogenesis. The advantage of this mechanism of vascular growth is that blood vessels are generated more rapidly and the capillaries thereby formed are less leaky. This review article summarizes our current knowledge concerning the role played by intussusceptive microvascular growth in tumor growth. Interestingly, an angiogenic switch from sprouting to intussusceptive angiogenesis occurs after treatment with angiogenesis inhibitors and may be considered as a tumor-protective adaptative response.     

Evaluation of Novel Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

The epidermal growth factor system is a well characterized growth factor receptor pathway, the deregulation of which has been be associated with neoplastic growth. Overexpression or amplification of the epidermal growth factor receptor (EGFR) or one of its ligands has been linked with the malignant transformation of cells and is correlated with poor prognosis in patients. PD 153035, a quinazoline, has been shown to inhibit the tyrosine kinase activity of EGFR by blocking ATP binding (Fry et al., Science 265: 1093-1095, 1994). We set out to determine whether the growth inhibition caused by this agent and five related compounds is a direct result of the blocking of EGFR signaling. The effects on cell proliferation produced by these agents were tested on several tumor cell lines and EC50 values obtained. The EGF responsive cell lines A-431 and MDA-MB-468 exhibit EC50 values of 3 and 6.7 micro M, respectively, for PD 153035 which was found to be the most potent. The agents were then tested for their ability to block the paradoxical high dose EGF induced inhibition of A-431 and MDA-MB-468 cell growth as well as EGF induced phosphorylation in A-431 cells. These compounds are able to completely block the effects of exogenously added EGF at 0.5 microM or less. However, higher doses (EC50's >or= 2 microM) were needed to block the growth of human tumor cell lines potentially implicating a second site of action for these compounds.     

In vitro growth characteristics associated with benign and metastatic variants of tumor cells

Summary Tumors show a wide range of growth rates in vivo. In general, nonmetastatic (benign) tumors appear to grow slowly, while metastasizing (malignant) tumors proliferate rapidly and contain a large number of dividing cells. In order to analyze if there is a direct relationship between metastatic potential and growth rate (without the influence of host factors), in vitro analyses are necessary. In vitro studies that compared monolayer doubling times and in vivo tumorigenicity rarely demonstrated a correlation between the two parameters. Differences in monolayer growth rates were observed among tumors, but the differences were unrelated to in vivo growth. In contrast, some tumor systems demonstrated a correlation between in vivo growth and/or malignant potential and growth properties observed during anchorage independent growth. Evidence is presented to show that in particular tumor systems, an analysis of colony size and colony morphology during growth in suspension can be used to study the relationship between malignant potential and growth properties.     

The effects of type beta transforming growth factor on proliferation and epidermal growth factor receptor expression in a human glioblastoma cell line

Summary Type beta transforming growth factor (B-TGF) is a potent growth inhibitor to many human tumor cell lines. Very little is known about the mechanism for this growth inhibitory action of BTGF We here report the effect of B-TGF on proliferation and epidermal growth factor receptor (R-EGF) expression in a human glioblastoma cell line named T-MG1.B-TGF inhibite the soft agar growth of T-MG1 cells. Maximum inhibition was 70%, achieved with 0.5 units BTGF. BTGF had no effect on monolayer growth of T MGl cells.T-MG1 cells contained abundant R-EGF, which could be divided into two subpopulations, one high affinity and one low affinity population of R-EGF. Treatment with B-TGF caused an initial decrease (0-6 h) in EGF-binding, followed by an increase in EGF-binding which reached maximum after 24 h exposure to B-TGE. Since addition of EGF to agar cultures gave no additional increase in inhibition by B-TGF and EGF alone had no inhibitory effect, we believe that binding of EGF to its receptor is not part of the pathway mediating the inhibitory effect of B-TGF.All neoplastic cells have lost some measure of growth control and the cellular elements involved are growth factors, growth factor receptors and oncogenes. T-MG1 cells contain abundant R-EGF and this may partly explain their malignant nature (malignant nature is here defined as ability to proliferate in agarose). Type alpha transforming growth factors, which in some cancer cells act as uncontrolled autocrine growth factors, were not found in protein extracts from T-MG1 cells. BTGF, which is normally found in all cells, could not be detected in protein extracts from T-MG1 cells. The lack of B-TGF as an autocrine growth inhibitor may be of importance for maintaining the malignant nature of T-MG1 cells.