9L gliosarcoma cell proliferation and tumor growth in rats are suppressed by N-hydroxy-N′-(4-butyl-2-methylphenol) formamidine (HET0016), a selective inhibitor of CYP4A

The present study examined the effects of N- hydroxy- N '-( 4butyl- 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 h of incubation, HET0016 reduced the proliferation of 9L in vitro by 55%, and this was associated with a fall in p42/ p44 mitogen- activated protein kinase and stress- activated protein kinase/ c- Jun NH (2)- terminal kinase phosphorylation and increased apoptosis. HET0016 inhibited epidermal growth factor ( EGF) and platelet- derived growth factor ( 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 i. p.) for 2 weeks reduced the volume of 9L tumors by 80%. This was accompanied by a 4- fold reduction in the mitotic index, a 3- to fold increase in the apoptotic index, and a similar to 50% decrease in vascularization in the tumor. HET0016 treatment increased mean survival time of the animals from 17 to 22 days. Liquid chromatography/ mass spectrometry experiments indicated that neither 9L cells grown in vitro nor 9L tumors removed produce 20- HETE when incubated with arachidonic acid. 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 antigrowth 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 antiproliferative effects of HET0016 on 9L cells in vitro seem unrelated to its ability to inhibit the formation of 20- HETE.