Received for publication November 7, 2005.
Revised December 8, 2005.
Accepted for publication December 8, 2005.

9L Gliosarcoma Cell Proliferation and Tumor Growth in Rats are Suppressed by HET0016, a Selective Inhibitor of CYP4A

Abstract

The present study examined the effects of N-hydroxy-N'-(4-butyl-2 methylphenyl) formamidine (HET0016), a selective inhibitor of the formation of 20-hydroxyeicosatrienoic acid (20-HETE) on the growth of 9L rat gliosarcoma cells in vitro and in vivo. After 48 hr incubation, HET0016 reduced the proliferation of 9L in vitro by 55% and this was associated with a fall in p42/p44 MAPK and SAPK/JNK phosphorylation, and increased apoptosis. HET0016 inhibited EGF and PDGF-induced proliferation and diminished phosphorylation of PDGF receptors. A stable 20-HETE analog increased 9L cell proliferation. In vivo, chronic administration of HET0016 (10 mg/Kg/day, ip) for two weeks reduced the volume of 9L tumors by 80%. This was accompanied by a 4-fold reduction in the mitotic index, a 3-4 folds increase in the apoptotic index and a ~50% decrease in vascularization in the tumor. HET0016 treatment increased mean survival time of the animals from 17 to 22 days. LC/MS experiments indicated that neither 9L cells grown in vitro nor 9L tumors removed produce 20-HETE when incubated with AA. The normal surrounding brain tissue, however, avidly makes 20-HETE, and this activity is selectively inhibited by HET0016. These results suggest that HET0016 may be the prototype of a class of anti-growth compounds that may be efficacious for treating malignant brain tumors. In vivo, it may act in part by inhibiting the formation of 20-HETE by the surrounding tissue. However, the anti proliferative effects of HET0016 on 9L cells in vitro appear unrelated to its ability to inhibit the formation of 20-HETE.

Key words: 20-HETE, 9L gliosarcoma, CYP4A inhibitors, HET0016, anti-angiogenisis, growth