Water-soluble HPMA copolymer-wortmannin conjugate retains phosphoinositide3-kinase inhibitory activity in vitro and in vivo

Phosphoinositide kinases and ATM-related genes play a central role in many physiological processes. Activation of phosphoinositide 3-kinase (PI 3-kina se) is essential for signal transduction by many growth factors and oncogen es and may contribute to tumor progression. In the nanomolar range, Wortman nin (WM), a fungal metabolite, is a potent inhibitor of type I PI 3-kinase- , it covalently modifies its catalytic subunit. Because WM is soluble only in organic solvents and unstable in water, there are difficulties in its us e in vivo. To generate a water-soluble WM derivative, we used a conjugate o f N-(2-hydroxypropyl)methaerylamide (HPMA) copolymer and 11-O-desacetylwort mannin (DAWM), which has a slightly lower inhibitory activity than WM. We c ovalently attached DAWM to HPMA copolymer containing oligopeptide (GFLG) si de-chains. The final product had an estimated molecular mass of 20 kDa and contained 2 wt.% of DAWM. The HPMA copolymer PHPMA-DAWM conjugate inhibited type I PI 3-kinase activity in vitro and growth factor-stimulated activati on of Akt in vivo; it possessed approximately 50% of the inhibitory activit y of DMSO solubilized WM. The specificity and stability of the PHPMA-DAWM c onjugate is currently under investigation. The new water-soluble form of WM may be useful in investigations of the role of PI 3-kinase in tumor progre ssion and other cellular biological functions in vivo. (C) 2001 Elsevier Sc ience BY All rights reserved.