This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gururaja, T. L. Articles by Payan, D. G. Search for Related Content PubMed PubMed Citation Articles by Gururaja, T. L. Articles by Payan, D. G.

R-253 Disrupts Microtubule Networks in Multiple Tumor Cell Lines

Authors' Affiliation: Rigel Pharmaceuticals, Inc., South San Francisco, California

Requests for reprints: Tarikere L. Gururaja, Rigel Pharmaceuticals, Inc., 1180 Veterans Boulevard, South San Francisco, CA 94080. Phone: 650-624-1100; Fax: 650-624-1101; E-mail: tgururaja{at}rigel.com.

Purpose: The design and development of synthetic small molecules to disrupt microtubule dynamics is an attractive therapeutic strategy for anticancer drug discovery research. Loss of clinical efficacy of many useful drugs due to drug resistance in tumor cells seems to be a major hurdle in this endeavor. Thus, a search for new chemical entities that bind tubulin, but neither are a substrate of efflux pump, P-glycoprotein 170/MDR1, nor cause undesired side effects, would potentially increase the therapeutic index in certain cancer treatments.

Experimental Design: A high-content cell-based screen of a compound library led to the identification of a new class of compounds belonging to a thienopyrimidine series, which exhibited significant antitumor activities. On structure-activity relationship analysis, R-253 [N-cyclopropyl-2-(6-(3,5-dimethylphenyl)thieno[3,2-d]pyrimidin-4-yl)hydrazine carbothioamide] emerged as a potent antiproliferative agent (average EC₅₀, 20 nmol/L) when examined in a spectrum of tumor cell lines.

Results: R-253 is structurally unique and destabilizes microtubules both in vivo and in vitro. Standard fluorescence-activated cell sorting and Western analyses revealed that the effect of R-253 on cell growth was associated with cell cycle arrest in mitosis, increased select G₂-M checkpoint proteins, and apoptosis. On-target activity of R-253 on microtubules was further substantiated by immunofluorescence studies and selected counter assays. R-253 competed with fluorescent-labeled colchicine for binding to tubulin, indicating that its binding site on tubulin could be similar to that of colchicine. R-253 neither is a substrate of P-glycoprotein 170/MDR1 nor is cytotoxic to nondividing human hepatocytes.

Conclusion: Both biochemical and cellular mechanistic studies indicate that R-253 could become a promising new tubulin-binding drug candidate for treating various malignancies.

This article has been cited by other articles:

				Y.-M. Wang, L.-X. Hu, Z.-M. Liu, X.-F. You, S.-H. Zhang, J.-R. Qu, Z.-R. Li, Y. Li, W.-J. Kong, H.-W. He, et al. N-(2,6-Dimethoxypyridine-3-yl)-9-Methylcarbazole-3-Sulfonamide as a Novel Tubulin Ligand against Human Cancer Clin. Cancer Res., October 1, 2008; 14(19): 6218 - 6227. [Abstract] [Full Text] [PDF]