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OSU-03012 Stimulates PKR-Like Endoplasmic Reticulum-Dependent Increases in 70-kDa Heat Shock Protein Expression, Attenuating Its Lethal Actions in Transformed Cells

Departments of Biochemistry (M.A.P., A.Y., M.R., G.Z., S.S., S.G., P.D.), Medicine (M.R., S.G.), Neurosurgery (M.G.), and Radiation Oncology (A.Y.), Virginia Commonwealth University, Richmond, Virginia; Division of Medicinal Chemistry, College of Pharmacy, the Ohio State University, Columbus, Ohio (C.-S.C.); Departments of Radiation Oncology (C.K.) and Hematology/Oncology (L.H.), University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania; Department of Radiation Oncology, Harvard University, Boston, Massachusetts (S.K.C.); Departments of Pathology, Neurosurgery and Urology, Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, College of Physicians and Surgeons, New York, New York (P.B.F.); Division of Human Gene Therapy, Departments of Medicine, Pathology, and Surgery and the Gene Therapy Center, University of Alabama at Birmingham, Birmingham, Alabama (D.T.C.); and Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts (M.Y.S.)

We have further defined mechanism(s) by which 2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl}acetamide [OSU-03012 (OSU)], a derivative of the cyclooxygenase-2 (COX2) inhibitor celecoxib but lacking COX2 inhibitory activity, kills transformed cells. In cells lacking expression of protein kinase R-like endoplasmic reticulum kinase (PERK^-/-), the lethality of OSU was attenuated. OSU enhanced the expression of Beclin 1 and ATG5 and cleavage of pro-caspase 4 in a PERK-dependent fashion and promoted the Beclin 1- and ATG5-dependent formation of vacuoles containing LC3, followed by a subsequent caspase 4-dependent cleavage of cathepsin B and a cathepsin B-dependent formation of low pH intracellular vesicles; cathepsin B was activated and released into the cytosol and genetic suppression of caspase 4, cathepsin B, or apoptosis-inducing factor function significantly suppressed cell killing. In parallel, OSU caused PERK-dependent increases in 70-kDa heat shock protein (HSP70) expression and decreases in 90-kDa heat shock protein (HSP90) and Grp78/BiP expression. Changes in HSP70 expression were post-transcriptional. Knock-down or small-molecule inhibition of HSP70 expression enhanced OSU toxicity, and overexpression of HSP70 suppressed OSU-induced low pH vesicle formation and lethality. Our data demonstrate that OSU-03012 causes cell killing that is dependent on PERK-induced activation of multiple toxic proteases. OSU-03012 also increased expression of HSP70 in a PERK-dependent fashion, providing support for the contention that OSU-03012-induced PERK signaling promotes both cell survival and cell death processes.

Address correspondence to: Dr. Paul Dent, Department of Biochemistry, 401 College Street, Massey Cancer Center, Room 280a, Box 980035, Virginia Commonwealth University, Richmond, VA 23298-0035. E-mail: pdent{at}vcu.edu