Windham T Christopher, Parikh Nila U, Siwak Doris R, Summy Justin M, McConkey David J, Kraker Alan J, Gallick Gary E
Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, Texas, TX 77030, USA.
Oncogene. 2002 Nov 7;21(51):7797-807. doi: 10.1038/sj.onc.1205989.
Src is a non-receptor protein tyrosine kinase, the expression and activity of which is increased in >80% of human colon cancers with respect to normal colonic epithelium. Previous studies from this and other laboratories have demonstrated that Src activity contributes to tumorigenicity of established colon adenocarcinoma cell lines. Src participates in the regulation of many signal transduction pathways, among which are those leading to cellular survival. In this study, we addressed the potential role of Src activation to a specific aspect of tumor cell survival, resistance to detachment-induced apoptosis (anoikis). Using five colon tumor cell lines with different biologic properties and genetic alterations, we demonstrate that expression and activity of Src corresponds with resistance to anoikis. Enforced expression of activated Src in subclones of SW480 cells (of low intrinsic Src expression and activity) increases resistance to anoikis; whereas decreased Src expression in HT29 cells (of high Src expression and activity) by transfection with anti-sense Src expression vectors increases susceptibility to anoikis. In contrast, increasing or decreasing Src expression had no effect on susceptibility to staurosporine-induced apoptosis in attached cells. PD173955, a Src family-specific tyrosine kinase inhibitor, increases the susceptibility of HT29 cells to anoikis in a dose- and time-dependent manner. Increasing Src expression and activity led to increased phosphorylation of Akt, a mediator of cellular survival pathways, whereas decreasing Src activity led to decreased Akt phosphorylation. In colon tumor cells with high Src activity, the PI3 kinase inhibitor LY 294002 sensitized cells to anoikis. These results suggest that Src activation may contribute to colon tumor progression and metastasis in part by activating Akt-mediated survival pathways that decrease sensitivity of detached cells to anoikis.
Src是一种非受体蛋白酪氨酸激酶，相对于正常结肠上皮，其在80%以上的人类结肠癌中表达和活性增加。本实验室和其他实验室先前的研究表明，Src活性有助于已建立的结肠腺癌细胞系的致瘤性。Src参与许多信号转导途径的调节，其中包括导致细胞存活的途径。在本研究中，我们探讨了Src激活在肿瘤细胞存活的一个特定方面——对脱离诱导的凋亡（失巢凋亡）的抵抗中的潜在作用。使用五种具有不同生物学特性和基因改变的结肠肿瘤细胞系，我们证明Src的表达和活性与对失巢凋亡的抵抗相关。在SW480细胞亚克隆（内源性Src表达和活性较低）中强制表达活化的Src可增加对失巢凋亡的抵抗；而通过转染反义Src表达载体降低HT29细胞（Src表达和活性较高）中的Src表达，则增加了对失巢凋亡的敏感性。相反，增加或降低Src表达对贴壁细胞中星形孢菌素诱导的凋亡敏感性没有影响。PD173955，一种Src家族特异性酪氨酸激酶抑制剂，以剂量和时间依赖性方式增加HT29细胞对失巢凋亡的敏感性。Src表达和活性的增加导致细胞存活途径的介导因子Akt的磷酸化增加，而Src活性的降低导致Akt磷酸化减少。在具有高Src活性的结肠肿瘤细胞中，PI3激酶抑制剂LY 294002使细胞对失巢凋亡敏感。这些结果表明，Src激活可能部分通过激活Akt介导的存活途径来促进结肠肿瘤的进展和转移，该途径降低了脱离细胞对失巢凋亡的敏感性。
