Glick A B, Lee M M, Darwiche N, Kulkarni A B, Karlsson S, Yuspa S H
Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Genes Dev. 1994 Oct 15;8(20):2429-40. doi: 10.1101/gad.8.20.2429.
To study the contribution of autocrine and paracrine TGF-beta 1 to tumor progression in a well-defined system of multistage carcinogenesis, keratinocytes with a targeted deletion of the TGF-beta 1 gene were initiated in vitro with the v-rasHa oncogene and their in vivo tumorigenic properties were determined by skin grafting initiated cells onto athymic mice in combination with either wild-type or null dermal fibroblasts. Grafts of v-rasHa-initiated null keratinocytes progressed rapidly to multifocal squamous cell carcinomas within dysplastic papillomas irrespective of the fibroblast genotype, whereas the initiated control genotypes formed well-differentiated papillomas. Malignant progression was not associated with mutations in the c-rasHa gene, alterations in p53 protein, or loss of responsiveness to TGF-beta 1. The tumor cell labeling index was elevated in grafts of initiated null keratinocytes with wild-type fibroblasts compared to tumors of other genotypes. However, labeling index in all tumors was reduced when TGF-beta 1 null fibroblasts formed the stroma. The null tumor cells could not accumulate TGF-beta 1 from the host, but grafts of uninitiated null keratinocytes, which formed a normal epidermis, became TGF-beta 1 positive even though they did not express TGF-beta 1 mRNA. These results demonstrate that autocrine TGF-beta 1 suppresses the frequency and rate of malignant progression, and that autocrine and paracrine TGF-beta 1 can have opposing effects on tumor cell proliferation. The lack of paracrine inhibition of tumor cell progression appears to result from the inability of tumor cells to localize host-derived TGF-beta 1 by a mechanism that operates in normal cells.
为了在一个明确的多阶段致癌系统中研究自分泌和旁分泌转化生长因子β1（TGF-β1）对肿瘤进展的作用，用v-rasHa癌基因在体外启动TGF-β1基因靶向缺失的角质形成细胞，并通过将起始细胞移植到无胸腺小鼠的皮肤上，并联合野生型或无效真皮成纤维细胞来确定其体内致瘤特性。无论成纤维细胞基因型如何，v-rasHa启动的无效角质形成细胞移植瘤均迅速进展为发育异常乳头瘤内的多灶性鳞状细胞癌，而起始对照基因型则形成分化良好的乳头瘤。恶性进展与c-rasHa基因突变、p53蛋白改变或对TGF-β1反应性丧失无关。与其他基因型肿瘤相比，野生型成纤维细胞的起始无效角质形成细胞移植瘤中的肿瘤细胞标记指数升高。然而，当TGF-β1无效成纤维细胞形成基质时，所有肿瘤的标记指数均降低。无效肿瘤细胞不能从宿主中积累TGF-β1，但形成正常表皮的未起始无效角质形成细胞移植瘤即使不表达TGF-β1 mRNA也变为TGF-β1阳性。这些结果表明，自分泌TGF-β1可抑制恶性进展的频率和速率，且自分泌和旁分泌TGF-β1对肿瘤细胞增殖可能具有相反的作用。肿瘤细胞进展缺乏旁分泌抑制似乎是由于肿瘤细胞无法通过正常细胞中起作用的机制定位宿主来源的TGF-β1所致。
