Malignant pheochromocytoma (PCC) is a rare tumor with a very poor prognosis and no effective treatments. The aim of this study was to assess the efficacy of a novel second-generation synthetic heat-shock protein 90 (HSP90) inhibitor, NVP-AUY922, to treat malignant PCC in vitro and in vivo.

Cell Counting Kit-8 (CCK-8) and Transwell assays were used to assess the effects of NVP-AUY922 on the proliferation and migration of the PCC cell line PC12. Flow cytometry was used to determine the effects of NVP-AUY922 on apoptosis and cell-cycle progression. Activation of phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB/AKT) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling was measured using a Western blot analysis. In vivo, a mouse xenograft model was used to test the effects of intraperitoneal injection of NVP-AUY922 on tumor growth.

NVP-AUY922 was found to be cytotoxic in PC12 cells at lower concentrations compared with 17-allylamino-17-demethoxygeldanamcyin (17-AAG). NVP-AUY922 inhibited the proliferation of PC12 cells in a time- and concentration-dependent manner and decreased the rate of migration of PC12 cells. Furthermore, we found that HSP90 inhibition induced cell-cycle arrest and apoptosis. In vivo, administration of NVP-AUY922 reduced PCC tumor growth without significant weight loss. Finally, we observed the modulation of MEK/ERK and PI3K/AKT signaling in response to NVP-AUY922 exposure.

NVP-AUY922 exhibits potent anti-PCC activities in vitro and in vivo and represents a promising therapeutic small molecule for treating malignant PCC.

• HSP90
• NVP-AUY922
• pheochromocytoma
• therapy
• xenograft model

The 22-mer c-kit promoter sequence folds into a parallel-stranded quadruplex with a unique structure, which has been elucidated by crystallographic and NMR methods and shows a high degree of structural conservation. We have carried out a series of extended (up to 10 μs long, ∼50 μs in total) molecular dynamics simulations to explore conformational stability and loop dynamics of this quadruplex. Unfolding no-salt simulations are consistent with a multi-pathway model of quadruplex folding and identify the single-nucleotide propeller loops as the most fragile part of the quadruplex. Thus, formation of propeller loops represents a peculiar atomistic aspect of quadruplex folding. Unbiased simulations reveal μs-scale transitions in the loops, which emphasizes the need for extended simulations in studies of quadruplex loops. We identify ion binding in the loops which may contribute to quadruplex stability. The long lateral-propeller loop is internally very stable but extensively fluctuates as a rigid entity. It creates a size-adaptable cleft between the loop and the stem, which can facilitate ligand binding. The stability gain by forming the internal network of GA base pairs and stacks of this loop may be dictating which of the many possible quadruplex topologies is observed in the ground state by this promoter quadruplex.

• Hsp90-inhibition
• Liposarcoma
• Myxoid
• NVP-AUY922

• Animals
• Antineoplastic Agents/pharmacology
• Apoptosis/drug effects
• Cell Proliferation/drug effects
• Cell Survival/drug effects
• Dose-Response Relationship, Drug
• G2 Phase Cell Cycle Checkpoints/drug effects
• HCT116 Cells
• HSP90 Heat-Shock Proteins/antagonists & inhibitors
• HSP90 Heat-Shock Proteins/metabolism
• Humans
• Isoxazoles/pharmacology
• Liposarcoma, Myxoid/drug therapy
• Liposarcoma, Myxoid/genetics
• Liposarcoma, Myxoid/metabolism
• Liposarcoma, Myxoid/pathology
• MAP Kinase Signaling System/drug effects
• Mice, Inbred NOD
• Mice, SCID
• Molecular Targeted Therapy
• Phosphatidylinositol 3-Kinase/metabolism
• Proto-Oncogene Proteins c-akt/metabolism
• Resorcinols/pharmacology
• Time Factors
• Xenograft Model Antitumor Assays

Gastrointestinal stromal tumors (GISTs) are the most common type of mesenchymal tumor of the gastrointestinal tract. The tumorigenesis of GISTs is driven by gain-of-function mutations in KIT or platelet-derived growth factor receptor α (PDGFRA), resulting in constitutive activation of the tyrosine kinase and its downstream signaling pathways. Oncogenic KIT or PDGFRA mutations are compelling therapeutic targets for the treatment of GISTs, and the KIT/PDGFRA inhibitor imatinib is the standard of care for patients with metastatic GISTs. However, most GIST patients develop clinical resistance to imatinib and other tyrosine kinase inhibitors. Five mechanisms of resistance have been characterized: (1) acquisition of a secondary point mutation in KIT or PDGFRA; (2) genomic amplification of KIT; (3) activation of an alternative receptor tyrosine kinase; (4) loss of KIT oncoprotein expression; and (5) wild-type GIST. Currently, sunitinib is used as a second-line treatment for patients after imatinib failure, and regorafenib has been approved for patients whose disease is progressing on both imatinib and sunitinib. Phase II/III trials are currently in progress to evaluate novel inhibitors and immunotherapies targeting KIT, its downstream effectors such as phosphatidylinositol 3-kinase, protein kinase B and mammalian target of rapamycin, heat shock protein 90, and histone deacetylase inhibitor. Other candidate targets have been identified, including ETV1, AXL, insulin-like growth factor 1 receptor, KRAS, FAS receptor, protein kinase c theta, ANO1 (DOG1), CDC37, and aurora kinase A. These candidates warrant clinical evaluation as novel therapeutic targets in GIST.

• Gastrointestinal stromal tumors
• Tyrosine kinase inhibitors
• KIT
• Platelet-derived growth factor receptor α
• Targets

• CKIT
• gastrointestinal stromal tumors
• gastrointestinal tract
• receptor tyrosine kinase
• targeted therapy

• B16 melanoma
• Cisplatin
• Neem leaf glycoprotein
• Sunitinib malate
• Tumor microenvironment

• soft tissue sarcoma
• targeted therapy
• molecular mechanisms

• Angiogenesis Inhibitors/therapeutic use
• Apoptosis/genetics
• Autophagy
• Cell Proliferation/drug effects
• Clinical Trials as Topic
• Gastrointestinal Neoplasms/drug therapy
• Gastrointestinal Neoplasms/therapy
• Gastrointestinal Stromal Tumors/drug therapy
• Humans
• Molecular Targeted Therapy
• Oncogene Fusion
• Oncogene Proteins, Fusion/antagonists & inhibitors
• Sarcoma/drug therapy
• Sarcoma/genetics
• Sarcoma/pathology
• Sarcoma/surgery
• Soft Tissue Neoplasms/drug therapy
• Soft Tissue Neoplasms/genetics
• Soft Tissue Neoplasms/pathology
• Translocation, Genetic
• Tumor Suppressor Protein p53/genetics

• R01 CA138345 NCI NIH HHS

• GIST
• adherence
• conjoint analysis
• discrete choice experiment
• patient preference
• toxicities