An essential part for Rho–associated kinase in the transcellular invasion of tumor cells

Abstract

Adhesion of tumor cells to host cell layers and subsequent transcellular migration are pivotal steps in cancer invasion and metastasis. The small GTPase Rho controls cell adhesion and motility through reorganization of the actin cytoskeleton and regulation of actomyosin contractility. Cultured rat MM1 hepatoma cells migrate through a mesothelial cell monolayer in vitro in a serum-dependent, Rho-mediated manners. Among several proteins isolated as putative target molecules of Rho, the ROCK (ROK) family of Rho-associated serine-threonine protein kinases are thought to participate in the induction of focal adhesions and stress fibers in cultured cells, and to mediate calcium sensitization of smooth muscle contraction by enhancing phosphorylation of the regulatory light chain of myosin. Transfection of MM1 cells with cDNA encoding a dominant active mutant of ROCK conferred invasive activity independently of serum and Rho. In contrast, expression of a dominant negative, kinase-defective ROCK mutant substantially attenuated the invasive phenotype. A specific ROCK inhibitor (Y-27632) blocked both Rho-mediated activation of actomyosin and invasive activity of these cells. Furthermore, continuous delivery of this inhibitor using osmotic pumps considerably reduced the dissemination of MM1 cells implanted into the peritoneal cavity of syngeneic rats. These results indicate that ROCK plays an essential part in tumor cell invasion, and demonstrate its potential as a therapeutic target for the prevention of cancer invasion and metastasis.

Downregulation of laminin α4 chain expression inhibits glioma invasionin vitro andin vivo

“…In general, cancer cell motility involves integrin signaling, focal-contact formation and actomyosin-dependent contractility controlled by Rac, Rho or myosin light-chain kinase signaling pathways. 28,[35][36][37][38] Laminins affect cell functions, including adhesion, migration and differentiation, through binding to integrins. Integrins a6b1 and a3b1 are laminin-8 receptors.…”

Metastasis: cell-autonomous mechanisms versus contributions by the tumor microenvironment

“…After an early activation phase, where RhoA is required for Ecadherin clustering, RhoA gets gradually downregulated with a concomitant repression of cell migration [30]. In contrast, forced expression of RhoA (and also RhoC) in tumor cells induces focal adhesions and stress fibers, promoting invasion and metastasis [31,32]. Upon loss of Ecadherin function, RhoA, Rac1 and Cdc42 are released from adhesion junctions and promote cell migration and invasion.…”

Dependence of metastatic cancer cell invasion on MLCK-catalyzed phosphorylation of myosin regulatory light chain

“…6 Increased MRLC phosphorylation has been demonstrated to parallel an increase in motility and/or invasiveness of cells overexpressing upstream regulators of MLCK and MRLC, whereas inhibition of MRLC phosphorylation showed reversed effects. [7][8][9][10] The MLL cell, a rat prostatic adenocarcinoma, is highly metastatic in vivo, correlating with its highly invasive behaviour in vitro as demonstrated by the in vitro invasion assay. 11 Here, we show that in vitro invasion of MLL cells was severely inhibited by treatment with the MLCK inhibitors, ML-7 and ML-9, while the ability to survive and proliferate was minimally affected.…”