Kim Hwang-Phill, Lee Mi-Sook, Yu Jiyon, Park Jin-Ah, Jong Hyun-Soon, Kim Tae-You, Lee Jung Weon, Bang Yung-Jue
Cancer Research Institute, Department of Tumor Biology, College of Medicine, Seoul National University, 28, Yongon-Dong, Chongno-Gu, Seoul 110-799, South Korea.
Biochem J. 2004 Apr 1;379(Pt 1):141-50. doi: 10.1042/BJ20031408.
Signalling by integrin-mediated cell anchorage to extracellular matrix proteins is co-operative with other receptor-mediated signalling pathways to regulate cell adhesion, spreading, proliferation, survival, migration, differentiation and gene expression. It was observed that an anchorage-independent gastric carcinoma cell line (SNU16) became adherent on TGF-beta1 (transforming growth factor beta1) treatment. To understand how a signal cross-talk between integrin and TGF-beta1 pathways forms the basis for TGF-beta1 effects, cell adhesion and signalling activities were studied using an adherent subline (SNU16Ad, an adherent variant cell line derived from SNU16) derived from the SNU16 cells. SNU16 and SNU16Ad cells, but not integrin alpha5-expressing SNU16 cells, showed an increase in adhesion on extracellular matrix proteins after TGF-beta1 treatment. This increase was shown to be mediated by an integrin alpha3 subunit, which was up-regulated in adherent SNU16Ad cells and in TGF-beta1-treated SNU16 cells, compared with the parental SNU16 cells. After TGF-beta1 treatment of SNU16Ad cells on fibronectin, Tyr-416 phosphorylation of c-Src was increased, but Ras-GTP loading and ERK1/ERK2 (extracellular-signal-regulated kinases 1 and 2) activity were decreased, which showed a dependence on c-Src family kinase activity. Studies on adhesion and signalling activities using pharmacological inhibitors or by transient-transfection approaches showed that inhibition of ERK1/ERK2 activity increased TGF-beta1-mediated cell adhesion slightly, but not the basal cell adhesion significantly, and that c-Src family kinase activity and decrease in Ras/ERKs cascade activity were required for the TGF-beta1 effects. Altogether, the present study indicates that TGF-beta1 treatment causes anchorage-independent gastric carcinoma cells to adhere by an increase in integrin alpha3 level and a c-Src family kinase activity-dependent decrease in Ras/ERKs cascade activity.
整合素介导的细胞与细胞外基质蛋白的锚定信号传导与其他受体介导的信号通路协同作用，以调节细胞粘附、铺展、增殖、存活、迁移、分化和基因表达。据观察，一种不依赖锚定的胃癌细胞系（SNU16）在转化生长因子β1（TGF-β1）处理后变得具有粘附性。为了了解整合素和TGF-β1信号通路之间的信号串扰如何构成TGF-β1效应的基础，使用源自SNU16细胞的贴壁亚系（SNU16Ad，一种源自SNU16的贴壁变异细胞系）研究了细胞粘附和信号传导活性。SNU16和SNU16Ad细胞，但不包括表达整合素α5的SNU16细胞，在TGF-β1处理后对细胞外基质蛋白的粘附增加。这种增加被证明是由整合素α3亚基介导的，与亲代SNU16细胞相比，整合素α3亚基在贴壁的SNU16Ad细胞和TGF-β1处理的SNU16细胞中上调。在纤连蛋白上对SNU16Ad细胞进行TGF-β1处理后，c-Src的Tyr-416磷酸化增加，但Ras-GTP负载和细胞外信号调节激酶1/2（ERK1/ERK2）活性降低，这显示出对c-Src家族激酶活性的依赖性。使用药理学抑制剂或通过瞬时转染方法对粘附和信号传导活性的研究表明，抑制ERK1/ERK2活性会略微增加TGF-β1介导的细胞粘附，但不会显著增加基础细胞粘附，并且TGF-β1效应需要c-Src家族激酶活性以及Ras/ERK级联活性的降低。总之，本研究表明，TGF-β1处理通过增加整合素α3水平和Ras/ERK级联活性的c-Src家族激酶活性依赖性降低，使不依赖锚定的胃癌细胞发生粘附。
