Journal
MOLECULAR CANCER THERAPEUTICS
Volume 10, Issue 8, Pages 1419-1429Publisher
AMER ASSOC CANCER RESEARCH
DOI: 10.1158/1535-7163.MCT-10-1057
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Funding
- New Zealand Foundation of Research, Science, and Technology
- Cancer Society of NZ
- Wellington Medical Research Foundation
- Victoria University of Wellington
- NIH [CA100202, RO1 CA114335]
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Peloruside A and laulimalide are potent microtubule-stabilizing natural products with a mechanism of action similar to that of paclitaxel. However, the binding site of peloruside A and laulimalide on tubulin remains poorly understood. Drug resistance in anticancer treatment is a serious problem. We developed peloruside A- and laulimalide-resistant cell lines by selecting 1A9 human ovarian carcinoma cells that were able to grow in the presence of one of these agents. The 1A9-laulimalide resistant cells (L4) were 39-fold resistant to the selecting agent and 39-fold cross-resistant to peloruside A, whereas the 1A9-peloruside A resistant cells (R1) were 6-fold resistant to the selecting agent while they remained sensitive to laulimalide. Neither cell line showed resistance to paclitaxel or other drugs that bind to the taxoid site on beta-tubulin nor was there resistance to microtubule-destabilizing drugs. The resistant cells exhibited impaired peloruside A/laulimalide-induced tubulin polymerization and impaired mitotic arrest. Tubulin mutations were found in the beta I-tubulin isotype, R306H or R306C for L4 and A296T for R1 cells. This is the first cell-based evidence to support a beta-tubulin-binding site for peloruside A and laulimalide. To determine whether the different resistance phenotypes of the cells were attributable to any other tubulin alterations, the beta-tubulin isotype composition of the cells was examined. Increased expression of beta II- and beta III-tubulin was observed in L4 cells only. These results provide insight into how alterations in tubulin lead to unique resistance profiles for two drugs, peloruside A and laulimalide, that have a similar mode of action. Mol Cancer Ther; 10(8); 1419-29. (C) 2011 AACR.
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