Lu P J, Lu Q L, Rughetti A, Taylor-Papadimitriou J
Department of Epithelial Cell Biology, Imperial Cancer Research Fund, London, United Kingdom.
J Cell Biol. 1995 Jun;129(5):1363-78. doi: 10.1083/jcb.129.5.1363.
Overexpression of the B cell leukemia/lymphoma-2 (bcl-2) gene has been shown to confer a survival advantage on cells by inhibiting apoptosis. In epithelia, the bcl-2 gene is also related to development and differentiation, and the protein is strongly expressed in the embryo in the epithelial cells of the developing mammary gland. To investigate directly the effect of bcl-2 on human epithelial cells, we used an amphotropic recombinant retrovirus to introduce the gene into nontumorigenic cell lines developed from luminal epithelial cells cultured from milk. Here we demonstrate that while bcl-2 overexpression does not directly induce the tumorigenic phenotype, it provides a survival advantage to the mammary epithelial cells by inhibiting cell death at confluence or under conditions of serum starvation, bcl-2 can also affect the phenotype of the original epithelial cells, and promote epithelial-mesenchymal conversion, accompanied by loss of the cell adhesion molecules E-cadherin and alpha 2 beta 1 integrin. The extent of the epithelial-mesenchymal conversion varies with small differences in the phenotype of the parental line and with the level of expression of Bcl-2 and in some cases cell lines emerge with a mixed phenotype. The increased survival of Bcl-2-expressing cells at confluence results in multilayering, and the development of three- dimensional structures. Where a mixed phenotype is observed these structures consist of an outer layer of polarized epithelial cells separated by a basement membrane-like layer from an inner mass of fibroblastoid cells. Branching morphogenesis of bcl-2 transfectants is also observed in collagen gels (in the absence of fibroblast growth factors). The results strongly indicate that by increasing their survival under restrictive growth conditions, and by modifying the epithelial phenotype, bcl-2 can influence the specific morphogenetic behavior of mammary epithelial cells.
已表明B细胞白血病/淋巴瘤-2（bcl-2）基因的过表达通过抑制细胞凋亡赋予细胞生存优势。在上皮组织中，bcl-2基因也与发育和分化相关，并且该蛋白在发育中的乳腺上皮细胞的胚胎中强烈表达。为了直接研究bcl-2对人上皮细胞的影响，我们使用双嗜性重组逆转录病毒将该基因导入从乳汁培养的管腔上皮细胞衍生的非致瘤细胞系中。在此我们证明，虽然bcl-2过表达不会直接诱导致瘤表型，但它通过在汇合时或血清饥饿条件下抑制细胞死亡为乳腺上皮细胞提供生存优势，bcl-2还可影响原始上皮细胞的表型，并促进上皮-间质转化，同时伴随着细胞粘附分子E-钙粘蛋白和α2β1整合素的丧失。上皮-间质转化的程度因亲代细胞系表型的微小差异以及Bcl-2的表达水平而异，在某些情况下，细胞系会出现混合表型。表达Bcl-2的细胞在汇合时存活率增加导致多层化，并形成三维结构。在观察到混合表型的情况下，这些结构由一层极化上皮细胞外层组成，该外层通过类似基底膜的层与内部的成纤维细胞样细胞团分隔开。在胶原凝胶中（在没有成纤维细胞生长因子的情况下）也观察到bcl-2转染子的分支形态发生。结果强烈表明，通过在限制性生长条件下提高其存活率以及改变上皮表型，bcl-2可影响乳腺上皮细胞的特定形态发生行为。
