OSU-03012 suppresses GRP78/BiP expression that causes PERK-dependent increases in tumor cell killing

Abstract

We have further defined mechanism(s) by which the drug OSU-03012 (OSU) kills tumor cells. OSU lethality was suppressed by knock down of PERK and enhanced by knock down of ATF6 and IRE1α. OSU treatment suppressed expression of the chaperone, BiP/GRP78, and did so through reduced stability of the protein. Knock down of BiP/GRP78 further enhanced OSU lethality. Overexpression of BiP/GRP78 abolished OSU toxicity. Pre-treatment of cells with OSU enhanced radiosensitivity to a greater extent than concomitant or sequential drug treatment with radiation exposure. Expression of a mutant active p110 PI3K, or mutant active forms of the EGFR in GBM cells did not differentially suppress OSU killing. In contrast loss of PTEN function reduced OSU lethality, without altering AKT, p70 S6K or mTOR activity, or the drug's ability to radiosensitize GBM cells. Knock down of PTEN protected cells from OSU and radiation treatment whereas re-expression of PTEN facilitated drug lethality and radiosensitization. In a dose-dependent fashion OSU prolonged the survival of mice carrying GBM tumors and interacted with radiotherapy to further prolong survival. Collectively, our data show that reduced BiP/GRP78 levels play a key role in OSU-3012 toxicity in GBM cells, and that this drug has in vivo activity against an invasive primary human GBM isolate.

Regulation of dimethyl-fumarate toxicity by proteasome inhibitors

“…Antibody reagents, other kinase inhibitors, caspase inhibitors cell culture reagents, and non-commercial recombinant adenoviruses have been previously described. [39][40][41][42] Previously characterized semi-established GBM5 / GBM6 / GBM12 / GBM14 glioblastoma cells were supplied by Dr. C.D. James (University of California, San Francisco) and Dr. J.N.…”

“…Samples were isolated at the indicated times and SDS PAGE and immunoblotting was performed as described in refs. [39][40][41][42] Blots were observed by using an Odyssey IR imaging system (LI-COR Biosciences, Lincoln, NE).…”

“…[39][40][41][42] Cells were infected with these adenoviruses at an approximate m.o.i. as indicated in the figure legend (usually an moi of 50).…”

The Heat Shock Protein Story—From Taking mTORC1,2 and Heat Shock Protein Inhibitors as Therapeutic Measures for Treating Cancers to Development of Cancer Vaccines

“…The drug was inferred to treat glioblastomas also according to [180]. See Section 5.6 on the PERK-eIF2α-ATF4-CHOP apoptotic signaling machinery for details, according to authors' review opinion.…”

Needle-Free Delivery of Acetalated Dextran-Encapsulated AR-12 Protects Mice from Francisella tularensis Lethal Challenge

“…Initially, it was thought that the mechanism of action of AR-12 was the direct inhibition of PDK-I (30), which results in lower AKT phosphorylation, along with endoplasmic reticulum stress and autophagy induction (24,26,31). However, recent studies indicate that PDK-I is not the target of AR-12 (26,32); rather, the target is immunoglobulin heavy chain-binding protein (GRP78/ BiP). Additionally, our previous studies indicated that AR-12 induces autophagy in macrophages at 1 M (28, 29), which is much lower than the concentration observed for its inhibitory activity against PDK-1.…”