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CHEMOTHERAPY, ANTIBIOTICS, AND GENE THERAPY

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

Henry Ford Hospital, Detroit, Michigan (M.G., J.D.F., S.L.B., A.S.A., P.A.E.); Medical College of Wisconsin, Milwaukee, Wisconsin (R.J.R.); University of Texas Southwestern Medical Center, Dallas, Texas (J.R.F.); and Henry Ford Hospital and Wayne State University, Detroit, Michigan (A.G.S.)

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 NH₂-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 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.

Address correspondence to: Dr. Meng Guo, Eye Care Services, Henry Ford Hospital, One Ford Place, 4 D, Detroit, MI 48202-3450. E-mail: mguo1{at}hfhs.org