Mechanistic evaluation of the novel HSP90 inhibitor NVP-AUY922 in adult and pediatric glioblastoma

Gene expression-based chemical genomics identifies heat-shock protein 90 inhibitors as potential therapeutic drugs in cholangiocarcinoma

BACKGROUND

Cholangiocarcinoma (CCA) is an aggressive tumor with a poor prognosis. There is no standard therapy for CCA, and novel drugs for treating refractory CCA need to be identified.

METHODS

The authors hypothesized that, if a drug could reverse the gene expression signature of CCA, then it may inhibit the carcinogenesis of CCA and, hence, would be a potential therapeutic agent. Thus, the gene expression signatures from patients with CCA were queried using the bioinformatic method Connectivity Map, resulting in the enrichment of heat-shock protein 90 (HSP90) inhibitors with therapeutic potentials.

RESULTS

Two HSP90 inhibitors, 17-AAG (tanespimycin) and the synthetic diarylisoxazole amide resorcinol NVP-AUY922, demonstrated potent antiproliferative activity in in vitro studies. In a thioacetamide-induced animal model, NVP-AUY922 also had antitumor activity and resulted in objective tumor regression. In addition, NVP-AUY922 reduced the expression of client oncoproteins involved in CCA oncogenesis and inhibited downstream proteins of both the phosphatidylinositol 3-kinase catalytic subunit α/v-akt murine thymoma viral oncogene homolog 1 protein kinase (PIK3/AKT) pathway and the v-Ki-ras2 Kirsten rat sarcoma viral oncogene/mitogen-activated protein kinase (KRAS/MAPK) pathway.

CONCLUSIONS

Preclinical data from the current study suggest that NVP-AUY922 may be an effective treatment option for patients with CCA.

Anti-tumor activity of the HSP90 inhibitor SNX-2112 in pediatric cancer cell lines

BACKGROUND

HSP90 plays a central role in stabilizing client proteins involved in malignant processes. SNX-2112 is an orally administered potent HSP90 inhibitor that has demonstrated pre-clinical anti-tumor activity in adult malignancies. As many childhood tumors depend upon HSP90 client proteins, we sought to test the pre-clinical efficacy of SNX-2112 in a panel of pediatric cancer cell lines both as a single-agent and in combination with cisplatin (CP).

PROCEDURE

Eight cell lines (from osteosarcoma, neuroblastoma, hepatoblastoma, and lymphoma) were studied. Short- and long-term effects of SNX-2112 were assessed by MTT and clonogenic assays. Cell cycling was measured using flow cytometry. Status of HSC70, HSP72, AKT1, C-Raf, and PARP was assessed by immunoblotting. Efficacy of SNX-2112 in combination with CP was assessed using median-effect analysis.

RESULTS

Cell lines studied demonstrated sensitivity to SNX-2112 with IC(50) values ranging from 10-100 nM. Low dose treatments (12 nM) resulted in a cytostatic response with a minimal increase in sub-G1 content. A higher dose (70 nM) exhibited a more prolonged inhibition and larger sub-G1 accumulation. Observed levels of AKT1 and C-Raf were markedly reduced over time along with an increase in PARP cleavage. In concurrently administered combination treatments, SNX-2112 and CP synergistically inhibited cell growth.

CONCLUSIONS

SNX-2112 showed marked single-agent activity in pediatric cancer cell lines with downstream effects on HSP90 client proteins. The combination of SNX-2112 and CP showed synergistic activity in two cell lines tested. Further studies of HSP90 inhibitors such as SNX-2112 as a single agent or in combination with chemotherapy are warranted in pediatric cancer.

Evidence for efficacy of new Hsp90 inhibitors revealed by ex vivo culture of human prostate tumors

PURPOSE

Targeting Hsp90 has significant potential as a treatment for prostate cancer, but prototypical agents such as 17-allylamino-17 demethoxygeldanamycin (17-AAG) have been ineffective in clinical trials. Recently, a phase I study aimed at defining a biologically active dose reported the first response to an Hsp90 inhibitor in a patient with prostate cancer, which supports the development of new generation compounds for this disease.

EXPERIMENTAL DESIGN

The biological actions of two new synthetic Hsp90 inhibitors, NVP-AUY922 and NVP-HSP990, were evaluated in the prostate cancer cell lines PC-3, LNCaP, and VCaP and in an ex vivo culture model of human prostate cancer.

RESULTS

In cell lines, both NVP-AUY922 and NVP-HSP990 showed greater potency than 17-AAG with regard to modulation of Hsp90 client proteins, inhibition of proliferation, and induction of apoptotic cell death. In prostate tumors obtained from radical prostatectomy that were cultured ex vivo, treatment with 500 nmol/L of NVP-AUY922, NVP-HSP990, or 17-AAG caused equivalent target modulation, determined by the pharmacodynamic marker Hsp70, but only NVP-AUY922 and NVP-HSP990 showed antiproliferative and proapoptotic activity.

CONCLUSIONS

This study provides some of the first evidence that new generation Hsp90 inhibitors are capable of achieving biologic responses in human prostate tumors, with both NVP-AUY922 and NVP-HSP990 showing potent on-target efficacy. Importantly, the ex vivo culture technique has provided information on Hsp90 inhibitor action not previously observed in cell lines or animal models. This approach, therefore, has the potential to enable more rational selection of therapeutic agents and biomarkers of response for clinical trials.

Sensitization of (colon) cancer cells to death receptor related therapies: a report from the FP6-ONCODEATH research consortium

The objective of the ONCODEATH consortium [EU Research Consortium "ONCODEATH" (2006-2010)] was to achieve sensitization of solid tumor cells to death receptor related therapies using rational mechanism-based drug combinations of targeted therapies. In this collaborative effort, during a period of 42 mo, cell and animal model systems of defined oncogenes were generated. Exploitation of generated knowledge and tools enabled the consortium to achieve the following research objectives: (1) elucidation of tumor components which confer sensitivity or resistance to TRAIL-induced cell death; (2) providing detailed knowledge on how small molecule Hsp90, Aurora, Choline kinase, BRAF inhibitors, DNA damaging agents, HDAC and DNMT inhibitors affect the intrinsic apoptotic amplification and execution machineries; (3) optimization of combined action of TRAIL with these therapeutics for optimum effects with minimum concentrations and toxicity in vivo. These findings provide mechanistic basis for a pharmacogenomic approach, which could be exploited further therapeutically, in order to reach novel personalized therapies for cancer patients.

The HSP90 inhibitor NVP-AUY922 radiosensitizes by abrogation of homologous recombination resulting in mitotic entry with unresolved DNA damage

Background

Heat shock protein 90 (HSP90) is a molecular chaperone responsible for the conformational maintenance of a number of client proteins that play key roles in cell cycle arrest, DNA damage repair and apoptosis following radiation. HSP90 inhibitors exhibit antitumor activity by modulating the stabilisation and activation of HSP90 client proteins. We sought to evaluate NVP-AUY922, the most potent HSP90 inhibitor yet reported, in preclinical radiosensitization studies.

Principal Findings

NVP-AUY922 potently radiosensitized cells in vitro at low nanomolar concentrations with a concurrent depletion of radioresistance-linked client proteins. Radiosensitization by NVP-AUY922 was verified for the first time in vivo in a human head and neck squamous cell carcinoma xenograft model in athymic mice, as measured by delayed tumor growth and increased surrogate end-point survival (p = <0.0001). NVP-AUY922 was shown to ubiquitously inhibit resolution of dsDNA damage repair correlating to delayed Rad51 foci formation in all cell lines tested. Additionally, NVP-AUY922 induced a stalled mitotic phenotype, in a cell line-dependent manner, in HeLa and HN5 cell lines irrespective of radiation exposure. Cell cycle analysis indicated that NVP-AUY922 induced aberrant mitotic entry in all cell lines tested in the presence of radiation-induced DNA damage due to ubiquitous CHK1 depletion, but resultant downstream cell cycle effects were cell line dependent.

Conclusions

These results identify NVP-AUY922 as the most potent HSP90-mediated radiosensitizer yet reported in vitro, and for the first time validate it in a clinically relevant in vivo model. Mechanistic analysis at clinically achievable concentrations demonstrated that radiosensitization is mediated by the combinatorial inhibition of cell growth and survival pathways, ubiquitous delay in Rad51-mediated homologous recombination and CHK1-mediated G₂/M arrest, but that the contribution of cell cycle perturbation to radiosensitization may be cell line specific.

Advances in the clinical development of heat shock protein 90 (Hsp90) inhibitors in cancers

Hsp90 is an ATP dependent molecular chaperone protein which integrates multiple oncogenic pathways. As such, Hsp90 inhibition is a promising anti-cancer strategy. Several inhibitors that act on Hsp90 by binding to its N-terminal ATP pocket have entered clinical evaluation. Robust pre-clinical data suggested anti-tumor activity in multiple cancer types. Clinically, encouraging results have been demonstrated in melanoma, acute myeloid leukemia, castrate refractory prostate cancer, non-small cell lung carcinoma and multiple myeloma. In breast cancer, proof-of-concept was demonstrated by first generation Hsp90 inhibitors in combination with trastuzumab mainly in human epidermal growth factor receptor 2 (HER2)+metastatic breast cancer. There are a multitude of second generation Hsp90 inhibitors currently under investigation. To date, however, there is no FDA approved Hsp90 inhibitor nor standardized assay to ascertain Hsp90 inhibition. This review summarizes the current status of both first and second generation Hsp90 inhibitors based on their chemical classification and stage of clinical development. It also discusses the pharmacodynamic assays currently implemented in clinic as well as other novel strategies aimed at enhancing the effectiveness of Hsp90 inhibitors. Ultimately, these efforts will aid in maximizing the full potential of this class of agents. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).

Radiosensitization of normoxic and hypoxic h1339 lung tumor cells by heat shock protein 90 inhibition is independent of hypoxia inducible factor-1α

Background

Ionizing irradiation is a commonly accepted treatment modality for lung cancer patients. However, the clinical outcome is hampered by normal tissue toxicity and tumor hypoxia. Since tumors often have higher levels of active heat shock protein 90 (Hsp90) than normal tissues, targeting of Hsp90 might provide a promising strategy to sensitize tumors towards irradiation. Hsp90 client proteins include oncogenic signaling proteins, cell cycle activators, growth factor receptors and hypoxia inducible factor-1α (HIF-1α). Overexpression of HIF-1α is assumed to promote malignant transformation and tumor progression and thus might reduce the accessibility to radiotherapy.

Methodology/Principal Findings

Herein, we describe the effects of the novel Hsp90 inhibitor NVP-AUY922 and 17-allylamino-17-demethoxygeldanamycin (17-AAG), as a control, on HIF-1α levels and radiosensitivity of lung carcinoma cells under normoxic and hypoxic conditions. NVP-AUY922 exhibited a similar biological activity to that of 17-AAG, but at only 1/10 of the dose. As expected, both inhibitors reduced basal and hypoxia-induced HIF-1α levels in EPLC-272H lung carcinoma cells. However, despite a down-regulation of HIF-1α upon Hsp90 inhibition, sensitivity towards irradiation remained unaltered in EPLC-272H cells under normoxic and hypoxic conditions. In contrast, treatment of H1339 lung carcinoma cells with NVP-AUY922 and 17-AAG resulted in a significant up-regulation of their initially high HIF-1α levels and a concomitant increase in radiosensitivity.

Conclusions/Significance

In summary, our data show a HIF-1α-independent radiosensitization of normoxic and hypoxic H1339 lung cancer cells by Hsp90 inhibition.

Strong anti-tumor effect of NVP-AUY922, a novel Hsp90 inhibitor, on non-small cell lung cancer

The anti-tumor activity of a newly developed Hsp90 inhibitor, NVP-AUY922 (AUY922), against non-small cell lung cancer (NSCLC) was examined. Twenty-one NSCLC cell lines were used, the somatic alterations of which were characterized. Cell proliferation was analyzed using a modified MTS assay. Expression of the client proteins was assessed using Western blotting. The cell cycle was analyzed using flow cytometry. The IC50 value of AUY922 for the NSCLC cell lines ranged from 5.2 to 860 nM (median, 20.4 nM). Based on previous data, cells with an IC50 of less than 50 nM were classified as sensitive cells and 19 of the 21 NSCLC cell lines were judged to be sensitive. The IC50 of five malignant pleural mesothelioma (MPM) cell lines revealed that the MPM cells had a significantly higher IC50 value (median, 89.2 nM; range, 22.2-24,100 nM) than the NSCLC cells (p=0.015). There was significant depletion of both the total and phosphorylated client proteins--EGFR, MET, HER2 and AKT--at low drug concentrations (50-100 nM) in drug-sensitive cell lines. Cell-cycle analysis was performed for two sensitive cell lines, H1975 and H838. Following AUY922 treatment, an increase in the sub-G0-G1 cell population, as well as appearance of cleaved PARP expression, indicated the induction of apoptosis. In conclusion, AUY922 was effective against most NSCLC cell lines, independent of the type of known molecular alteration, and appears to be a promising new drug for the treatment of NSCLC.

A compound that inhibits the HOP-Hsp90 complex formation and has unique killing effects in breast cancer cell lines

The chaperone Hsp90 is required for the correct folding and maturation of certain "client proteins" within all cells. Hsp90-mediated folding is particularly important in cancer cells, because upregulated or mutant oncogenic proteins are often Hsp90 clients. Hsp90 inhibitors thus represent a route to anticancer agents that have the potential to be active against several different types of cancer. Currently, various Hsp90 inhibitors that bind to Hsp90 at its ATP-binding site are in preclinical and clinical trials. Some of the most promising Hsp90 ATP-binding site inhibitors are the well characterized geldanamycin derivative 17-AAG and the recently described compounds PU-H71 and NVP-AUY922. An undesirable characteristic of these compounds is the transcriptional upregulation of Hsp70 that has prosurvival effects. Here we characterize the activity of a new type of chaperone inhibitor, 1,6-dimethyl-3-propylpyrimido[5,4-e][1,2,4]triazine-5,7-dione (named C9 for simplicity). Using purified protein components in vitro, C9 prevents Hsp90 from interacting with the cochaperone HOP and is thus expected to impair the Hsp90-dependent folding pathway in vivo. We show that this compound is effective in killing various breast cancer cell lines including the highly metastatic MDA-MB-231. An important property of this compound is that it does not induce the transcriptional upregulation of Hsp70. Moreover, when cells are treated with a combination of C9 and either 17-AAG or NVP-AUY922, the overexpression of Hsp70 is counteracted considerably and C9's lethal-IC50 decreases compared to its value when added alone.

Circulating extracellular proteasome in the cerebrospinal fluid: a study on concentration and proteolytic activity

Alterations of the intracellular ubiquitin-proteasome pathway are found in neurodegenerative and inflammatory disorders of the central nervous system, as well as in its malignancies. Inhibitory substrates of the proteasomes represent promising approaches to control autoimmune inflammations and induction of apoptosis in cancer cells. Extracellular circulating proteasomes are positively correlated to outcome prognosis in hematogenic neoplasias and the outcome in critically ill patients. Previously, we reported raised levels of proteolytic active 20S proteasomes in the extracellular alveolar space in patients with acute respiratory distress syndrome (ARDS). For the cerebrospinal fluid, we assumed that extracellular circulating proteasomes with enzymatic activity can be found, too. Cerebrospinal fluid (CSF) samples of twenty-six patients (14 females, 12 males), who underwent diagnostic spinal myelography, were analyzed for leukocyte cell count, total protein content, lactate and interleukine-6 (Il-6) concentrations. CSF samples were analyzed for concentration and enzymatic activity of extracellular 20S proteasomes (fluorescenic substrate cleavage; femtokatal). Blood samples were analyzed with respect to concentration of extracellular circulating proteasomes. Choroidal plexus was harvested at autopsies and examined with immunoelectron microscopy (EM) for identification of possible transportation mechanisms. Statistical analysis was performed using SPSS (18.0.3). In all patients, extracellular proteasome was found in the CSF. The mean concentration was 24.6 ng/ml. Enzymatic activity of the 20S subunits of proteasomes was positively identified by the fluorescenic subtrate cleavage at a mean of 8.5 fkat/ml. Concentrations of extracellular proteasomes in the CSF, total protein content and Il-6 were uncorrelated. Immunoelectron microscopy revealed merging vesicles of proteasomes with the outer cell membrane suggestive of an exozytic transport mechanism. For the first time, extracellular circulating 20S proteasome in the CSF of healthy individuals is identified and its enzymatic activity detected. A possible exozytic vesicle-bond transportation mechanism is suggested by immunoelectron microscopy. The present study raises more questions on the function of extracellular proteasome in the CSF and encourages further studies on the role of extracellular protesomes in pathological conditions of the central nervous system (tumor lesions and inflammatory processes).

Hsp90 inhibitor-mediated disruption of chaperone association of ATR with hsp90 sensitizes cancer cells to DNA damage

Following DNA damage that results in stalled replication fork, activation of ATR-CHK1 signaling induces the DNA damage response (DDR) in transformed cells. In the present studies on human cervical and breast cancer cells, we determined the effects of hsp90 inhibition on the levels and accumulation of DNA damage/repair-associated proteins following exposure to γ-ionizing radiation (IR; 4 Gy). We show that hsp90 inhibition with 17-allylamino-demehoxygeldanamycin or the novel, nongeldanamycin analogue AUY922 (resorcinylic isoxazole amide; Novartis Pharma) dose-dependently reduced the levels of ATR and CHK1 without affecting ATM levels. AUY922-mediated depletion of ATR and CHK1 was associated with an increase in their polyubiquitylation and decreased binding to hsp90. Cotreatment with bortezomib partially restored AUY922-mediated depletion of ATR and CHK1 levels. Additionally, treatment with AUY922 reduced the accumulation of ATR, p53BP1, and CHK1 but not γ-H2AX to the sites of DNA damage. Following exposure to IR, AUY922 treatment abrogated IR-induced phospho (p)-ATR and p-CHK1 levels, but significantly enhanced γ-H2AX levels. AUY922 treatment also increased IR-induced accumulation of the cells in G(2)-M phase of the cell cycle, inhibited the repair of IR-induced DNA damage, and augmented IR-mediated loss of clonogenic survival. Short hairpin RNA-mediated depletion of ATR also inhibited IR-induced p-ATR and p-CHK1, but increased γ-H2AX levels, sensitizing cancer cells to IR-induced apoptosis and loss of clonogenic survival. These findings indicate that ATR is a bona fide hsp90 client protein and post-IR administration of AUY922, by inhibiting ATR-CHK1-mediated DDR, sensitizes cancer cells to IR.