van Nimwegen Maroesja J, Verkoeijen Saertje, van Buren Liesbeth, Burg Danny, van de Water Bob
Department of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University, Leiden, The Netherlands.
Cancer Res. 2005 Jun 1;65(11):4698-706. doi: 10.1158/0008-5472.CAN-04-4126.
An increased expression of focal adhesion kinase (FAK) in a variety of cancers is associated with a poor disease prognosis. To study the role of FAK in breast tumor growth and metastasis formation, we used conditional doxycycline-regulated expression of a dominant-negative acting splice variant of FAK, FAK-related non-kinase (FRNK), in MTLn3 mammary adenocarcinoma cells in a syngeneic Fischer 344 rat tumor and metastasis model. In cell culture, doxycycline-mediated expression of FRNK inhibited MTLn3 cell spreading and migration in association with reduced formation of focal adhesions and phosphorylation of FAK on Tyr(397), but FRNK did not cause apoptosis. Continuous expression of FRNK decreased the primary tumor growth in the mammary fat pad by 60%, which was not due to induction of apoptosis. Lung metastasis formation was almost completely prevented when FRNK was already expressed 1 day before tumor cell injection, whereas expression of FRNK 11 days after injection did not affect lung metastasis formation. FRNK expression during the first 5 days was sufficient to block metastasis formation, excluding the possibility of FRNK-induced dormancy of tumor cells. Together, these data fit with a model wherein FAK is required for breast tumor cell invasion/migration processes that take place in the early phase of metastasis formation. Our findings suggest that FAK is a good candidate for therapeutic intervention of metastasis formation.
在多种癌症中，粘着斑激酶（FAK）表达增加与疾病预后不良相关。为了研究FAK在乳腺肿瘤生长和转移形成中的作用，我们在同基因Fischer 344大鼠肿瘤和转移模型的MTLn3乳腺腺癌细胞中，使用强力霉素调控的FAK显性负性作用剪接变体——FAK相关非激酶（FRNK）的条件性表达。在细胞培养中，强力霉素介导的FRNK表达抑制MTLn3细胞铺展和迁移，同时粘着斑形成减少以及FAK在Tyr(397)位点的磷酸化降低，但FRNK并未引起细胞凋亡。FRNK的持续表达使乳腺脂肪垫中的原发性肿瘤生长减少60%，这并非由细胞凋亡诱导所致。当在肿瘤细胞注射前1天就已表达FRNK时，肺转移形成几乎完全被阻止，而在注射后11天表达FRNK则不影响肺转移形成。在最初5天内表达FRNK就足以阻止转移形成，排除了FRNK诱导肿瘤细胞休眠的可能性。总之，这些数据符合一种模型，即FAK是转移形成早期阶段乳腺肿瘤细胞侵袭/迁移过程所必需的。我们的研究结果表明，FAK是转移形成治疗干预的良好候选靶点。
