Judware R, Culp L A
Case Western Reserve University, School of Medicine, Department of Molecular Biology and Microbiology, Cleveland, OH 44106, USA.
Oncogene. 1995 Dec 21;11(12):2599-607.
Amplification of the N-myc oncogene is associated with progression of neuroblastoma in humans. Previous studies indicated that neuroblastoma cell lines which are amplified for the N-myc gene and over-express N-myc exhibit enhanced tumorigenic properties when injected into athymic nude mice. In addition, neuroblastoma cells which over-express N-myc (IMR32 cells) expressed little or no beta 1, alpha 2, or alpha 3 integrin subunits, as compared with cells which do not express N-myc (SKNSH cells). In order to probe the possible relationship between N-myc and beta 1 integrin gene expressions more directly, transfection experiments were performed in which an N-myc cDNA (on the episomal expression vector pREP4; high-level constitutive expression is driven by an RSV-LTR promoter) was introduced into SKNSH cells. Expression of N-myc produced significant morphological alterations in transfected cells; one subpopulation of cells remained spread on tissue culture substrata, while a second subpopulation became rounded and grew as multi-cellular aggregates. Spread (attached) cells expressed low levels of N-myc and high levels of beta 1 integrin, while rounded (loose) cells expressed relatively high levels of N-myc and low levels of beta 1 integrin. Maintenance of transfected cells in higher concentrations of selective agent produced a higher proportion of loose cells, which expressed even greater amounts of N-myc and even less beta 1 integrin; a similar effect was observed in attached cells. Interestingly, loose cell populations expressed elevated levels of the neural cell adhesion molecule [NCAM]. The results presented here infer that N-myc regulates the expression of the beta 1 integrin and NCAM cell-surface receptors responsible for cell:extracellular cellular matrix interaction and possibly cell:cell adhesion.
N - myc 癌基因的扩增与人类神经母细胞瘤的进展相关。先前的研究表明，N - myc 基因扩增且 N - myc 过表达的神经母细胞瘤细胞系，注射到无胸腺裸鼠体内时表现出更强的致瘤特性。此外，与不表达 N - myc 的细胞（SKNSH 细胞）相比，过表达 N - myc 的神经母细胞瘤细胞（IMR32 细胞）几乎不表达或不表达β1、α2 或α3 整合素亚基。为了更直接地探究 N - myc 与β1 整合素基因表达之间的可能关系，进行了转染实验，将 N - myc cDNA（在附加型表达载体 pREP4 上；由 RSV - LTR 启动子驱动高水平组成型表达）导入 SKNSH 细胞。N - myc 的表达在转染细胞中产生了显著的形态学改变；一部分细胞仍铺展在组织培养底物上，而另一部分细胞则变圆并形成多细胞聚集体生长。铺展（附着）的细胞表达低水平的 N - myc 和高水平的β1 整合素，而圆形（松散）的细胞表达相对高水平的 N - myc 和低水平的β1 整合素。在较高浓度的选择剂中培养转染细胞会产生更高比例的松散细胞，这些细胞表达更多的 N - myc 和更少的β1 整合素；在附着细胞中也观察到了类似的效果。有趣的是，松散细胞群体表达升高水平的神经细胞黏附分子[NCAM]。此处呈现的结果推断，N - myc 调节负责细胞与细胞外基质相互作用以及可能的细胞与细胞黏附的β1 整合素和 NCAM 细胞表面受体的表达。
