ZIA BC 005270 (ZIA) | |||
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Title | Molecular Mechanism of Action of Phorbol Ester | ||
Institution | NCI, Bethesda, MD | ||
Principal Investigator | Blumberg, Peter | NCI Program Director | N/A |
Cancer Activity | N/A | Division | CCR |
Funded Amount | $1,303,886 | Project Dates | 00/00/0000 - 00/00/0000 |
Fiscal Year | 2017 | Project Type | Intramural |
Research Topics w/ Percent Relevance | Cancer Types w/ Percent Relevance | ||
Arthritis (10.0%) Autoimmune Diseases (15.0%) Cancer (100.0%) Cancer Survivorship (35.0%) Chemotherapy (40.0%) Diabetes (45.0%) Inflammatory Bowel Disease (15.0%) |
Breast (5.0%) Leukemia (10.0%) Lung (10.0%) Multiple Myeloma (5.0%) Prostate (15.0%) Vascular Disease (5.0%) |
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Research Type | |||
Systemic Therapies - Discovery and Development Patient Care and Survivorship Issues |
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Abstract | |||
The overall direction of the Molecular Mechanisms of Tumor Promotion Section is to understand the regulation of the signaling pathways downstream from the lipophilic second messenger diacylglycerol, to elucidate the basis for heterogeneity of response to different ligands which function through this pathway, and to exploit this understanding for developing novel ligands with unique behavior that function through this pathway. A complementary direction is to understand the regulation and structure activity relations for the vanilloid receptor. The vanilloid receptor is a downstream target of the diacylglycerol signaling pathway, shares partial homology in its ligands to this pathway, and shares with the diacylglycerol signaling pathway an important role in inflammation. Both directions impact both our understanding of biological regulation and the potential development of therapeutic agents. Protein kinase C, the best studied downstream target for diacylglycerol, represents the classic system for tumor promotion and is a therapeutic target for cancer chemotherapy. The vanilloid receptor represents a promising therapeutic target for cancer pain, among other indications, and thus represents an important direction in palliative care for cancer patients. DAG-lactones represent a synthetically accessible platform for probing the structure activity relations of protein kinase C and the other targets downstream of the second messenger diacylglycerol. In a collaborative effort with the Kazanietz lab, we show that DAG ligands can achieve strong selectivity for PKC epsilon versus PKC alpha and that this selectivity can lead to differential PKC isotype down regulation. In other studies, we further refine our understanding of the features of dimeric DAG-lactones that might exploit the different spacing of the two C1 domains of different PKC isoforms as well as differences in C1 domain selectivity for generating ligands with marked isoform selectivity. Additionally, we have continued to evaluate DAG-lactones designed to have selectivity for the RasGRP subclass of diacylglycerol targets. This class of targets is of particular importance because it functions as an activator of Ras, which is many tumors shows enhanced activity without being mutated. Selectivity is being evaluated both at the in vitro level and in intact cells. Bryostatin is an agent in clinical trials with a unique mechanism of action. It binds to protein kinase C with high affinity and activates the enzyme but paradoxically antagonizes many protein kinase C mediated responses. We find, using microarray analysis of gene expression and aptamer arrays for analysis of protein expression, along with detailed examination of the time and dose dependence of genes representative of the differences in expression revealed by the microarray analysis, that transient duration is the predominant difference in the mode of action of bryostatin as compared to typical protein kinase C activators such as the phorbol esters. In collaboration with the group of Gary Keck, we seek to define the critical structural elements in bryostatin conferring its unique pattern of activity, with the goal of developing the next generation of bryostatin analogues. An important recent advance was to show that subcellular localization of bryostatin analogs cannot explain whether they function as phorbol ester analogs or as phorbol ester antagonists. Further, we show that bryostatin derivatives that only slowly penetrate into cells at no point are able to fully induce the transient responses induced by the phorbol esters. Protein kinase C is subject to post-translational modification, in particular phosphorylation. In collaboration with the CCR Collaborative Protein Technology Resource, we have shown that the extent of protein kinase C modification is much more extensive than had been recognized. Moreover, the pattern of modification was different for different ligands such as phorbol ester or bryostatin. We suggest |