Ligation of cell surface GRP78 with antibody directed against the COOH-terminal domain of GRP78 suppresses Ras/MAPK and PI 3-kinase/AKT signaling while promoting caspase activation in human prostate cancer cells.

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2010-01

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We have previously shown that treatment of prostate cancer and melanoma cells expressing GRP78 on their cell surface with antibody directed against the COOH-terminal domain of GRP78 upregulates and activates p53 causing decreased cell proliferation and upregulated apoptosis. In this report, we demonstrate that treatment of 1-LN prostate cancer cells with this antibody decreases cell surface expression of GRP78, Akt(Thr308) and Akt(Ser473) kinase activities and reduces phosphorylation of FOXO, and GSK3beta. This treatment also suppresses activation of ERK1/2, p38 MAPK and MKK3/6; however, it upregulates MKK4 activity. JNK, as determined by its phosphorylation state, is subsequently activated, triggering apoptosis. Incubation of cells with antibody reduced levels of anti-apoptotic Bcl-2, while elevating pro-apoptotic BAD, BAX and BAK expression as well as cleaved caspases-3, -7, -8 and -9. Silencing GRP78 or p53 gene expression by RNAi prior to antibody treatment abrogated these effects. We conclude that antibody directed against the COOH-terminal domain of GRP78 may prove useful as a pan suppressor of proliferative/survival signaling in cancer cells expressing GRP78 on their cell surface.

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Adenocarcinoma, Amino Acid Sequence, Antibodies, Monoclonal, Antigens, Neoplasm, Antigens, Surface, Caspases, Cell Line, Tumor, Enzyme Activation, Gene Knockdown Techniques, Heat-Shock Proteins, Humans, MAP Kinase Signaling System, Male, Mitogen-Activated Protein Kinases, Molecular Sequence Data, Neoplasm Proteins, Phosphatidylinositol 3-Kinases, Prostatic Neoplasms, Protein Kinases, Protein Structure, Tertiary, Proto-Oncogene Proteins c-akt, Signal Transduction, Transcription, Genetic

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https://hdl.handle.net/10161/3961

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Misra

Uma Kant Misra

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Pizzo

Salvatore Vincent Pizzo

Distinguished Professor of Pathology, in the School of Medicine

RESEARCH ABSTRACT
Studies from this laboratory identified cell surface expression of the molecular chaperone GRP78 as a major factor in prostate cancer and other malignancies.  Cell surface GRP78 functions as a signaling receptor promoting tumor proliferation and suppressing apoptosis.  Patients with a number of malignancies mount an autoimmune response to GRP78 and these antibodies, which bind to the NH2 terminal domains of GRP78, are receptor agonists whose appearance is a marker of poor prognosis.  More recently, we have shown that antibodies directed against the COOH-terminal domain of GRP78 are receptor antagonists which may have therapeutic potential for treating patients whose tumors express GRP78 on the cell surface.

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