ro-3306 and Neoplasms

Inhibitors of mitotic proteins such as Aurora kinase and polo-like kinase have shown promise in preclinical or early clinical development for cancer treatment. We have reported that the MiTMAB class of dynamin small molecule inhibitors are new antimitotic agents with a novel mechanism of action, blocking cytokinesis. Here, we examined 5 of the most potent of a new series of dynamin GTPase inhibitors called dynoles. They all induced cytokinesis failure at the point of abscission, consistent with inhibition of dynamin while not affecting other cell cycle stages. All 5 dynoles inhibited cell proliferation (MTT and colony formation assays) in 11 cancer cell lines. The most potent GTPase inhibitor, dynole 34-2, also induced apoptosis, as revealed by cell blebbing, DNA fragmentation, and PARP cleavage. Cell death was induced specifically following cytokinesis failure, suggesting that dynole 34-2 selectively targets dividing cells. Dividing HeLa cells were more sensitive to the antiproliferative properties of all 5 dynoles compared with nondividing cells, and nontumorigenic fibroblasts were less sensitive to cell death induced by dynole 34-2. Thus, the dynoles are a second class of dynamin GTPase inhibitors, with dynole 34-2 as the lead compound, that are novel antimitotic compounds acting specifically at the abscission stage.

Topics: Acrylamides; Animals; Antimitotic Agents; Antineoplastic Agents; Apoptosis; Calcineurin Inhibitors; Cell Death; Cell Division; Cell Line, Tumor; Cytokinesis; Dynamins; Fibroblasts; HeLa Cells; HT29 Cells; Humans; Indoles; Mice; Neoplasms; Polyploidy; Protein Kinase Inhibitors; Quinolines; Thiazoles; Tubulin

Abrogation of functional p53 is responsible for malignant cell transformation and the maintenance of malignant state of human papillomavirus-infected cancer cells. Thus, restoration of p53 has been regarded as an important strategy for molecular intervention combating papillomavirus-associated malignancies. We show here that depleting cyclin B1 stabilizes and reactivates p53 in papillomavirus-infected cervical cancer cell lines HeLa and CaSki. HeLa cells depleted of cyclin B1 exhibit mitotic defects in spindle formation and chromosome alignment. Downregulation of cyclin B1 increases p14 alternative reading frame of p16, the positive regulator of p53, and decreases phosphorylation of Ser315 in p53. Whereas RO-3306, a selective inhibitor of cyclin-dependent kinase 1 (Cdk1), suppresses this phosphorylation at Ser315 of p53, ZM447439, targeting Aurora A/B kinases, shows no effect. Further analyses in HeLa cells and HCT116 p53(-/-) cells suggest that the Ser315 phosphorylation by Cdk1 regulates negatively the protein stability and the function of p53. Moreover, increased p53 in HeLa cells is functional by showing its increased downstream effectors p21, mouse double minute 2 and Bax. Restoration of p53 and silencing cyclin B1 render cervical carcinoma cells more susceptible to DNA damage agent camptothecin. Taken together, targeting cyclin B1 might be an attractive strategy for preventing and treating papillomavirus-associated cancer by reactivating p53 and by reducing the Cdk1 activity.

Topics: Blotting, Western; CDC2 Protein Kinase; Cell Line, Tumor; Cell Nucleus; Cyclin B1; DNA Damage; Down-Regulation; HCT116 Cells; HeLa Cells; Host-Pathogen Interactions; Human papillomavirus 16; Human papillomavirus 18; Humans; Mitosis; Neoplasms; Phosphorylation; Quinolines; RNA Interference; Serine; Thiazoles; Tumor Suppressor Protein p53