Vascular Disrupting Activity of Tubulin-Binding 1,5-Diaryl-1H-imidazoles

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Reduced Expression of the ROCK Inhibitor Rnd3 Is Associated with Increased Invasiveness and Metastatic Potential in Mesenchymal Tumor Cells

BACKGROUND: Mesenchymal and amoeboid movements are two important mechanisms adopted by cancer cells to invade the surrounding environment. Mesenchymal movement depends on extracellular matrix protease activity, amoeboid movement on the RhoA-dependent kinase ROCK. Cancer cells can switch from one mechanism to the other in response to different stimuli, limiting the efficacy of antimetastatic therapies. METHODOLOGY AND PRINCIPAL FINDINGS: We investigated the acquisition and molecular regulation of the invasion capacity of neoplastically transformed human fibroblasts, which were able to induce sarcomas and metastases when injected into immunocompromised mice. We found that neoplastic transformation was associated with a change in cell morphology (from fibroblastic to polygonal), a reorganization of the actin cytoskeleton, a decrease in the expression of several matrix metalloproteases and increases in cell motility and invasiveness. In a three-dimensional environment, sarcomagenic cells showed a spherical morphology with cortical actin rings, suggesting a switch from mesenchymal to amoeboid movement. Accordingly, cell invasion decreased after treatment with the ROCK inhibitor Y27632, but not with the matrix protease inhibitor Ro 28-2653. The increased invasiveness of tumorigenic cells was associated with reduced expression of Rnd3 (also known as RhoE), a cellular inhibitor of ROCK. Indeed, ectopic Rnd3 expression reduced their invasive ability in vitro and their metastatic potential in vivo. CONCLUSIONS: These results indicate that, during neoplastic transformation, cells of mesenchymal origin can switch from a mesenchymal mode of movement to an amoeboid one. In addition, they point to Rnd3 as a possible regulator of mesenchymal tumor cell invasion and to ROCK as a potential therapeutic target for sarcomas

Inhibition of SIRT2 Potentiates the Anti-motility Activity of Taxanes: Implications for Antineoplastic Combination Therapies

Taxanes are potent inhibitors of cell motility, a property implicated in their antiangiogenic and antimetastatic activity and unrelated to their antiproliferative effect. The molecular mechanism of this anti-motility activity is poorly understood. In this study, we found that paclitaxel induced tubulin acetylation in endothelial and tumor cells, at concentrations that affected cell motility but not proliferation (10-8 to 10-9 M, for 4 hours). Induction of tubulin acetylation correlated with inhibition of motility but not proliferation based on a comparison of highly and poorly cytotoxic taxanes (paclitaxel and IDN5390) and tumor cell lines sensitive and resistant to paclitaxel (1A9 and 1A9 PTX22). Consistent with the hypothesis that tubulin deacetylase activity might affect cell response to the anti-motility activity of taxanes, we found that overexpression of the tubulin deacetylase SIRT2 increased cell motility and reduced cell response to the anti-motility activity of paclitaxel. Conversely, the SIRT2 inhibitor splitomicin reduced cell motility and potentiated the anti-motility activity of paclitaxel. The inhibitory effect was further potentiated by the addition of the HDAC6 inhibitor trichostatin A. Paclitaxel and splitomicin promoted translocation into the nucleus—and hence activation—of FOXO3a, a negative regulator of cell motility. This study indicates a role for SIRT2 in the regulation of cell motility and suggests that therapies combining sirtuin inhibitors and taxanes could be used to treat cell motility-based pathologic processes such as tumor angiogenesis, invasion, and metastasis