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Potentiation of the cytotoxicity of thymidylate synthase (TS) inhibitors by dipyridamole analogues with reduced α1-acid glycoprotein binding

Lookup NU author(s): Professor Nicola Curtin, Professor Alan Calvert, Professor Bernard Golding, Professor Roger Griffin, Professor Herbie Newell

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Abstract

Dipyridamole has been shown to enhance the in vitro activity of antimetabolite anticancer drugs through the inhibition of nucleoside transport. However, the clinical potential of dipyridamole has not been realized because of the avid binding of the drug to the plasma protein α1-acid glycoprotein (AGP). Dipyridamole analogues that retain potent nucleoside transport inhibitory activity in the presence of AGP are described and their ability to enhance the growth inhibitory and cytotoxic effects of thymidylate synthase (TS) inhibitors has been evaluated. Three dipyridamole analogues (NU3026, NU3059 and NU3060) were shown to enhance the growth inhibitory activity of the TS inhibitor CB3717 and block thymidine rescue in L1210 cells. The extent of potentiation at a fixed analogue concentration (10 μM) was related to the potency of inhibition of thymidine uptake. A further analogue, NU3076, was identified, which was more potent than dipyridamole with a K(i) value for inhibition of thymidine uptake of 0.1 μM compared to 0.28 μM for dipyridamole. In marked contrast to dipyridamole, inhibition of thymidine uptake by NU3076 was not significantly affected by the presence of AGP (5 mg ml-1). NU3076 and dipyridamole produced equivalent potentiation of the cytotoxicity of the non-classical antifolate TS inhibitor, nolatrexed, in L1210 cells with both compounds significantly reducing the LC90 by > threefold in the absence of salvageable thymidine. Thymidine rescue of L1210 cells from nolatrexed cytotoxicity was partially blocked by both 1 μM NU3076 and 1 μM dipyridamole. NU3076 also caused a significant potentiation of FU cytotoxicity in L1210 cells. These studies demonstrate that nucleoside transport inhibition can be maintained in the absence of AGP binding with the dipyridamole pharmacophore and that such analogues can enhance the cytotoxicity of TS inhibitors.


Publication metadata

Author(s): Curtin, N.J., Bowman, K., Turner, R., Huang, B., Loughlin, P., Calvert, A.H., Golding, B.T., Griffin, R.J., Newell, D.R.

Publication type: Article

Publication status: Published

Journal: British Journal of Cancer

Year: 1999

Volume: 80

Issue: 11

Pages: 1738-1746

Print publication date: 01/01/1999

ISSN (print): 0007-0920

ISSN (electronic): 1532-1827

URL: http://dx.doi.org/10.1038/sj.bjc.6690591

DOI: 10.1038/sj.bjc.6690591

PubMed id: 10468290


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