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 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 4-fold increase in the apoptotic index, and a approximately 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.