Synergistic activity of the Hsp90 inhibitor ganetespib with taxanes in non-small cell lung cancer models

Oleanolic acid increases the anticancer potency of doxorubicin in pancreatic cancer cells

Combination therapy is a novel cancer therapy approach that combines two or more chemotherapy drugs. This treatment modality enhances the efficacy of chemotherapy by targeting key pathways in an additive or synergistic manner. Therefore, we investigated the efficacy of combination therapy by widely used chemotherapy drug doxorubicin (DOX) and oleanolic acid (OA) to induction of apoptosis for pancreatic cancer (PC) therapy. The effects of DOX, OA, and their combination (DOX-OA) were investigated on proliferation and viability of PC cell line (PANC-1) by MTT assay. Moreover, migration and invasion of the cancer cells were evaluated by trans-well migration assay and wound healing assay. Flow cytometry and DAPI (4',6-diamidino-2-phenylindole) staining were employed to investigate apoptosis quantification and qualification of the treated cancer cells. Finally, mRNA expression of apoptosis-related genes was assessed by quantitative real-time polymerase chain reaction. Our results demonstrated that the proliferation and metastasis potential of PC cells significantly decreased after treatment by DOX, OA, and DOX-OA. Moreover, we observed an increase in apoptosis percentage in the treated cancer cells. The apoptosis-related gene expression was modified to increase the apoptosis rate in all of the treatment groups. However, the anticancer potency of DOX-OA combination was significantly more than that of DOX and OA treatments alone. Our study suggested that DOX-OA combination exerts more profound anticancer effects against PC cell lines than DOX or OA monotherapy. This approach may increase the efficiency of chemotherapy and reduce unintended side effects by lowering the prescribed dose of DOX.

The effects of STA-9090 (Ganetespib) and venetoclax (ABT-199) combination on apoptotic pathways in human cervical cancer cells

Combined chemotherapy is recommended strategy as a first-line treatment method in patients with cervical cancer. Ganetespib (STA-9090) is a second-generation heat shock protein 90 (Hsp90) inhibitor that blocks the ATPase function of Hsp90 and inhibits the proper folding of oncogenic client proteins. Venetoclax (ABT-199) is an orally bioavailable Bcl-2 (B-cell lymphoma 2) inhibitor that stimulates apoptotic signaling pathways in cancer cells. This study evaluated the anticancer effects of STA-9090 combined with Venetoclax in the human cervical cancer cell line (HeLa). The human cervical cancer cells were treated with STA-9090, Venetoclax, and Sta-9090 plus Venetoclax for 48 h, and cell viability was measured using the XTT assay. The alteration of the Hsp90 protein expression level and the chaperone activity of HSP90 were detected by ELISA and luciferase aggregation assay, respectively. For the apoptotic process, qRT-PCR was applied to study Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), Bcl-2-like protein 1 (Bcl-xL ), Cytochrome c (Cyt-c), Caspase3 (Cas-3), and Caspase7 (Cas-7) expression levels after drug treatments. Also, a colorimetric Cas-3 activity assay was performed to detect the induction of the apoptosis process. Our results demonstrated that 8 nM of STA-9090 combined with 4 µM of Venetoclax synergistically inhibited cervical cancer cell proliferation more than STA-9090 or Venetoclax alone after 48 h of treatment. STA-9090 and Venetoclax combination decreased the protein expression level of Hsp90 and significantly inhibited chaperone activity of Hsp90. This combination stimulated apoptosis in cervical cancer cells by down-regulating of anti-apoptotic markers while inducing pro-apoptotic markers. Also, the STA-9090-Venetoclax combination increased Cas-3 activity in Hela cells. Collectively, these findings pointed out that the STA-9090-Venetoclax combination exhibited more activity than the individual drugs to stimulate toxicity and apoptosis in cervical cancer cells based on HSP90 inhibition.

Ganetespib (STA-9090) augments sorafenib efficacy via necroptosis induction in hepatocellular carcinoma: Implications from preclinical data for a novel therapeutic approach

Sorafenib, a multikinase inhibitor, is a first-line treatment for advanced hepatocellular carcinoma, but its long-term effectiveness is limited by the emergence of resistance mechanisms. One such mechanism is the reduction of microvessel density and intratumoral hypoxia caused by prolonged sorafenib treatment. Our research has demonstrated that HSP90 plays a critical role in conferring resistance to sorafenib in HepG2 cells under hypoxic conditions and N-Nitrosodiethylamine-exposed mice as well. This occurs through the inhibition of necroptosis on the one hand and the stabilization of HIF-1α on the other hand. To augment the effects of sorafenib, we investigated the use of ganetespib, an HSP90 inhibitor. We found that ganetespib activated necroptosis and destabilized HIF-1α under hypoxia, thus enhancing the effectiveness of sorafenib. Additionally, we discovered that LAMP2 aids in the degradation of MLKL, which is the mediator of necroptosis, through the chaperone-mediated autophagy pathway. Interestingly, we observed a significant negative correlation between LAMP2 and MLKL. These effects resulted in a reduction in the number of surface nodules and liver index, indicating a regression in tumor production rates in mice with HCC. Furthermore, AFP levels decreased. Combining ganetespib with sorafenib showed a synergistic cytotoxic effect and resulted in the accumulation of p62 and inhibition of macroautophagy. These findings suggest that the combined therapy of ganetespib and sorafenib may offer a promising approach for the treatment of hepatocellular carcinoma by activating necroptosis, inhibiting macroautophagy, and exhibiting a potential antiangiogenic effect. Overall, continued research is critical to establish the full therapeutic potential of this combination therapy.

Role of Ganetespib, an HSP90 Inhibitor, in Cancer Therapy: From Molecular Mechanisms to Clinical Practice

Heat-shock proteins are upregulated in cancer and protect several client proteins from degradation. Therefore, they contribute to tumorigenesis and cancer metastasis by reducing apoptosis and enhancing cell survival and proliferation. These client proteins include the estrogen receptor (ER), epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R), human epidermal growth factor receptor 2 (HER-2), and cytokine receptors. The diminution of the degradation of these client proteins activates different signaling pathways, such as the PI3K/Akt/NF-κB, Raf/MEK/ERK, and JAK/STAT3 pathways. These pathways contribute to hallmarks of cancer, such as self-sufficiency in growth signaling, an insensitivity to anti-growth signals, the evasion of apoptosis, persistent angiogenesis, tissue invasion and metastasis, and an unbounded capacity for replication. However, the inhibition of HSP90 activity by ganetespib is believed to be a promising strategy in the treatment of cancer because of its low adverse effects compared to other HSP90 inhibitors. Ganetespib is a potential cancer therapy that has shown promise in preclinical tests against various cancers, including lung cancer, prostate cancer, and leukemia. It has also shown strong activity toward breast cancer, non-small cell lung cancer, gastric cancer, and acute myeloid leukemia. Ganetespib has been found to cause apoptosis and growth arrest in these cancer cells, and it is being tested in phase II clinical trials as a first-line therapy for metastatic breast cancer. In this review, we will highlight the mechanism of action of ganetespib and its role in treating cancer based on recent studies.

Establishment and large-scale validation of a three-dimensional tumor model on an array chip for anticancer drug evaluation

Two-dimensional (2D) tumor model has always poorly predicted drug response of animal model due to the lack of recapitulation of tumor microenvironment. Establishing a biomimetic, controllable, and cost-effective three-dimensional (3D) model and large-scale validation of its in vivo predictivity has shown promise in bridging the gap between the 2D tumor model and animal model. Here, we established a matrigel-based 3D micro-tumor model on an array chip for large-scale anticancer drug evaluation. Compared with the 2D tumor model, the 3D tumor model on the chip showed spheroid morphology, slower proliferation kinetics, and comparable reproducibility. Next, the results of the chemotherapeutic evaluation from 18 drugs against 27 cancer cell lines showed 17.6% of drug resistance on the 3D tumor model. Moreover, the evaluation results of targeted drugs showed expected sensitivity and higher specificity on the 3D tumor model compared with the 2D model. Finally, the evaluation results on the 3D tumor model were more consistent with the in vivo cell-derived xenograft model, and excluded 95% false-positive results from the 2D model. Overall, the matrigel-based 3D micro-tumor model on the array chip provides a promising tool to accelerate anticancer drug discovery.

Zeylenone synergizes with cisplatin in osteosarcoma by enhancing DNA damage, apoptosis, and necrosis via the Hsp90/AKT/GSK3β and Fanconi anaemia pathway

A safer and more effective combination strategy designed to enhance the efficacy and minimize the toxicity of cisplatin in osteosarcoma (OS) is urgently needed. Zeylenone (zey), a cyclohexene oxide compound, exerted an obvious inhibitory effect on several cancer cell lines and exhibited little cytotoxicity towards normal cells, enabling zey to play a unique role in combination therapy. Thus, the study aimed to determine whether the combination of zey and cisplatin produces synergistic antitumour effects on OS and to further explore molecular mechanisms. Initially, we found that zey potentiated the anti-osteosarcoma efficacy of cisplatin and exhibited synergistic interactions with cisplatin in vitro, which also were confirmed in vivo by using xenograft model. Mechanistically, zey and cisplatin synergistically induced DNA damage, cell cycle arrest, necrosis, and apoptosis in OS cells. Importantly, zey had a high binding affinity for Hsp90 and reduced the expression of Hsp90, which further induced the suppression of AKT/GSK3β signalling axis and the degradation of Fanconi anaemia (FA) pathway proteins. Thus, the Hsp90/AKT/GSK3β and FA pathway are the key to the synergism between zey and cisplatin. Overall, zey shows promise for development as a cisplatin chemosensitizer with clinical utility in restoring cisplatin sensitivity of cancer cells.

Heat-activated nanomedicine formulation improves the anticancer potential of the HSP90 inhibitor luminespib in vitro

The heat shock protein 90 inhibitor, luminespib, has demonstrated potent preclinical activity against numerous cancers. However, clinical translation has been impeded by dose-limiting toxicities that have necessitated dosing schedules which have reduced therapeutic efficacy. As such, luminespib is a prime candidate for reformulation using advanced drug delivery strategies that improve tumor delivery efficiency and limit off-target side effects. Specifically, thermosensitive liposomes are proposed as a drug delivery strategy capable of delivering high concentrations of drug to the tumor in combination with other chemotherapeutic molecules. Indeed, this work establishes that luminespib exhibits synergistic activity in lung cancer in combination with standard of care drugs such as cisplatin and vinorelbine. While our research team has previously developed thermosensitive liposomes containing cisplatin or vinorelbine, this work presents the first liposomal formulation of luminespib. The physico-chemical properties and heat-triggered release of the formulation were characterized. Cytotoxicity assays were used to determine the optimal drug ratios for treatment of luminespib in combination with cisplatin or vinorelbine in non-small cell lung cancer cells. The formulation and drug combination work presented in this paper offer the potential for resuscitation of the clinical prospects of a promising anticancer agent.

Identification of Predictive Biomarkers of Response to HSP90 Inhibitors in Lung Adenocarcinoma

Heat shock protein 90 (HSP90) plays an essential role in lung adenocarcinoma, acting as a key chaperone involved in the correct functioning of numerous highly relevant protein drivers of this disease. To this end, HSP90 inhibitors have emerged as promising therapeutic strategies, even though responses to them have been limited to date. Given the need to maximize treatment efficacy, the objective of this study was to use isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic techniques to identify proteins in human lung adenocarcinoma cell lines whose basal abundances were correlated with response to HSP90 inhibitors (geldanamycin and radicicol derivatives). From the protein profiles identified according to response, the relationship between lactate dehydrogenase B (LDHB) and DNA topoisomerase 1 (TOP1) with respect to sensitivity and resistance, respectively, to geldanamycin derivatives is noteworthy. Likewise, rhotekin (RTKN) and decaprenyl diphosphate synthase subunit 2 (PDSS2) were correlated with sensitivity and resistance to radicicol derivatives. We also identified a relationship between resistance to HSP90 inhibition and the p53 pathway by glucose deprivation. In contrast, arginine biosynthesis was correlated with sensitivity to HSP90 inhibitors. Further study of these outcomes could enable the development of strategies to improve the clinical efficacy of HSP90 inhibition in patients with lung adenocarcinoma.

Randomized Phase III Study of Ganetespib, a Heat Shock Protein 90 Inhibitor, With Docetaxel Versus Docetaxel in Advanced Non-Small-Cell Lung Cancer (GALAXY-2)

PURPOSE

Ganetespib, a highly potent heat shock protein 90 inhibitor, blocks multiple oncogenic pathways, resulting in antitumor activity. We evaluated the combination of ganetespib and docetaxel for second-line therapy of patients with advanced adenocarcinoma of the lung.

PATIENTS AND METHODS

In this international phase III trial, patients with stage IIIB or IV adenocarcinoma diagnosed > 6 months before study entry and 1 prior systemic therapy were randomly assigned (1:1) to ganetespib 150 mg/m² on days 1 and 15 with docetaxel 75 mg/m² on day 1 of a 21-day cycle or to docetaxel alone. The primary end point was overall survival (OS).

RESULTS

Of 677 enrolled patients, 335 were randomly assigned to ganetespib and docetaxel and 337 were assigned to docetaxel. The trial was stopped early as a result of futility at a planned interim analysis. The median OS time was 10.9 months (95% CI, 9.0 to 12.3 months) in the ganetespib and docetaxel arm compared with 10.5 months (95% CI, 8.6 to 12.2 months) in docetaxel arm (hazard ratio [HR], 1.11; 95% CI, 0.899 to 1.372; P = .329). Median progression-free survival was 4.2 months in the ganetespib and docetaxel arm and 4.3 months in the docetaxel arm (HR, 1.16; 95% CI, 0.96 to 1.403; P = .119). The addition of ganetespib did not improve outcomes compared with docetaxel alone for any secondary end point, including survival in the elevated lactate dehydrogenase or EGFR and ALK wild-type populations. The most common grade 3 or 4 adverse event in both arms was neutropenia (30.9% with ganetespib and docetaxel v 25% with docetaxel).

CONCLUSION

The addition of ganetespib to docetaxel did not result in improved survival for salvage therapy of patients with advanced-stage lung adenocarcinoma.

Synergistic activity of Hsp90 inhibitors and anticancer agents in pancreatic cancer cell cultures

Heat shock protein 90 (Hsp90) is a widely investigated target for anticancer therapy. The experimental Hsp90 inhibitors ICPD47 and ICPD62 demonstrated anticancer activity against colorectal, osteosarcoma and cervical cancer cell lines. However, their anticancer activity has not been investigated against pancreatic cancer cell lines yet, and there are no data about synergistic activity of these compounds in combination with clinically used anticancer agents. Pancreatic cancer cell lines, MIA PaCa-2 and PANC-1 were exposed to ICPD47 and ICPD62 alone and in combinations with antimetabolites gemcitabine (GEM), 5-fluorouracil (5-FU) and topoisomerase inhibitor doxorubicin (DOX). Effects on cell viability were determined by MTT assay. The synergistic activity was evaluated using Chou-Talalay method. Also, 3D cell cultures were formed using 3D Bioprinting method and the activity of each compound and their combinations was examined by measuring the size change of spheroids. The strongest synergistic activities were determined in combinations using all ratios of ICPD47 with GEM and ICPD62 with GEM in MIA PaCa-2 cell line (combination index <0.5). The combinations of ICPD47 with 5-FU and ICPD47 with GEM in a ratio of 1:5 showed the greatest effect on tumour spheroid growth in both cell lines. The ICPD47 in combination with mild hyperthermia showed significant results, where the EC₅₀ value in PANC-1 cell line dropped from 4.04 ± 0.046 to 1.68 ± 0.004 µM. The ICPD47 and ICPD62 under the same conditions could act synergistically with GEM, 5-FU and DOX and is worth of further investigations, and studies of synergistic effect is a promising path for more efficient anticancer therapies.

Part I of GANNET53: A European Multicenter Phase I/II Trial of the Hsp90 Inhibitor Ganetespib Combined With Weekly Paclitaxel in Women With High-Grade, Platinum-Resistant Epithelial Ovarian Cancer-A Study of the GANNET53 Consortium

Background: Stabilized mutant p53 protein (mutp53) is a novel target in epithelial ovarian cancer. Due to aberrant conformation, mutp53 proteins depend on folding support by the Hsp90 chaperone. Hsp90 blockade induces degradation of mutp53, resulting in tumor cell cytotoxicity and increased sensitivity to chemotherapeutics. Preclinical synergy of the Hsp90 inhibitor ganetespib combined with paclitaxel provided the rationale for testing the combination in platinum-resistant ovarian cancer (PROC) patients in the GANNET53 trial (NCT02012192). Methods: Eligible patients had high-grade PROC with ≤ 4 prior lines of chemotherapy. Weekly paclitaxel (80 mg/m²) and increasing doses of ganetespib (100, 150 mg/m²) were given i.v. on days 1, 8, 15 in a 28 days cycle until disease progression or unacceptable toxicity. Endpoints were safety and determination of phase II dose. Dose limiting toxicity (DLT) was defined as grade 4 toxicity (with exceptions) occurring in cycles 1&2. Results: Ten patients (median age 59 years; range 43-70) were enrolled. No DLT occurred in cohort 1 (4 patients treated with paclitaxel + ganetespib 100 mg/m²), nor in cohorts 2 and 3 (6 patients treated with paclitaxel + ganetespib 150 mg/m²). The most common adverse event (AE) related to ganetespib was transient grade 1/2 diarrhea (n = 6). Related grade 1/2 AEs in >2 patients included QTc prolongation (n = 4), nausea (n = 3), anemia (n = 3), headache (n = 3), fatigue (n = 3), and dyspnoea (n = 3). Most frequently related grade 3/4 AEs were diarrhea (n = 3) and neutropenia (n = 2). There was 1 death on study due to hemorrhage from a duodenal ulcer. Three patients discontinued study treatment due to serious AEs (digestive hemorrhage n = 1, cardiac failure n = 1, abdominal pain and vomiting n = 1), 6 due to progressive disease, one due to investigator and patient decision. Two patients achieved a partial response (ORR 20%) and 4 patients a stable disease (disease control rate of 60%). Median PFS was 2.9 months (1.6 months in cohort 1 at 100 mg/m² ganetespib, 5.1 months in cohorts 2+3 at 150 mg/m² ganetespib). Conclusions: The combination of ganetespib 150 mg/m² with paclitaxel 80 mg/m² once weekly for 3 out of 4 weeks was generally well-tolerated with no DLTs, and therefore chosen for the randomized phase II trial.

Hsp90 inhibitors enhance the antitumoral effect of osimertinib in parental and osimertinib-resistant non-small cell lung cancer cell lines

Background

Osimertinib improve therapy for non-small cell lung cancer (NSCLC). However, invariable acquired resistance appears.

Methods

MTT assay was used to analyze cell viability. Protein expression and activation was detected by Western blotting. In addition, the effects of heat shock protein 90 (Hsp90) inhibitors and osimertinib were studied in colony formation assays.

Results

Our laboratory generated osimertinib resistant cell lines from PC9 cell line and overexpression or activation of several proteins was detected. Hsp90 inhibitors, ganetespib and luminespib, inhibited cell viability and colony formation in H1975, PC9 and PC9-derived osimertinib-resistant cell lines and combination of these inhibitors with osimertinib achieved to enhance this cell viability and colony formation inhibition. Luminespib downregulated the expression of the several proteins involved in osimertinib-resistance and the combination of this compound plus osimertinib caused an important decrease of expression of several of these proteins, such as Stat3, Yap, Akt, EGFR and Met. Osimertinib activated the phosphorylation of several membrane receptors and downstream molecules that was partially inhibited by luminespib. In addition, a lung cancer patient with an EGFR eon 20 mutation had a partial radiographic response to ganetespib.

Conclusions

Hsp90 inhibitors and osimertinib exhibits a good efficiency to inhibit cell viability, colony formation and inhibits expression and activation of proteins involved in osimertinib-resistance and may represent an effective strategy for NSCLC with intrinsic resistance to osimertinib inhibition.

Nanomedicine-Assisted Combination Therapy of NSCLC: New Platinum-Based Anticancer Drug Synergizes the Therapeutic Efficacy of Ganetespib

Purpose: K-RAS is the most common mutated oncogene associated with Non-Small-Cell Lung Cancer (NSCLC). So far, there are no promising chemotherapies for the direct inhibition of K-RAS, and considered to be undruggable. In this work, we have introduced a new platinum-based cyanoximate complex, Pt(MCO)2, as an anti-cancer drug to enhance the therapeutic efficacy of Hsp90 inhibitor drug, ganetespib for the combination therapy of NSCLC. Methods: We have synthesized polyacrylic acid (PAA)-coated magnetic nanoparticles (MNPs) and used as drug delivery system. These MNPs were decorated with folic acid in order to target folate receptor-expressing NSCLC. The individual and combination of drugs as well as an optical dye DiI were co-encapsulated successfully inside the PAA-coating of MNPs to evaluate synergistic treatment option for NSCLC. The magnetic resonance (MR) and optical imaging modalities assisted for the monitoring drug loading and NSCLC treatment. Results: To evaluate the therapeutic efficacy of these customized MNPs, various cell-based assays including cell viability, apoptosis and necrosis, cell migration, comet and ROS experiments were performed. Results showed minimal toxicity for functional MNPs with no therapeutic drug and more than 60% cell death within 48 h of treatment, when single drug was encapsulated. Importantly, more than 90% cells were dead when both drugs were delivered. Overall, the results indicated that the Pt(MCO)2 drug enhances the therapeutic efficacy of ganetespib by more than 30% toxicity towards the targeted treatment of NSCLC, while showed minimal toxicity to the normal healthy tissues. Conclusion: We successfully developed new dual-modal magnetic nanomedicines for the rapid and controlled release of combination of drugs for the effective treatment of NSCLC. The MR and fluorescence modalities help monitoring the delivery of drugs, where the new platinum-based drug Pt(MCO)2 synergizes the therapeutic efficacy of ganetespib.

Ganetespib targets multiple levels of the receptor tyrosine kinase signaling cascade and preferentially inhibits ErbB2-overexpressing breast cancer cells

Although ErbB2-targeted therapeutics have significantly improved ErbB2⁺ breast cancer patient outcomes, therapeutic resistance remains a significant challenge. Therefore, the development of novel ErbB2-targeting strategies is necessary. Importantly, ErbB2 is a sensitive client protein of heat shock protein 90 (HSP90), which regulates client protein folding, maturation, and stabilization. HSP90 inhibition provides an alternative therapeutic strategy for ErbB2-targeted degradation. In particular, ganetespib, a novel HSP90 inhibitor, is a promising agent for ErbB2⁺ cancers. Nevertheless, the anti-cancer efficacy and clinical application of ganetespib for ErbB2⁺ breast cancer is largely unknown. In our study, we examined the anti-cancer effects of ganetespib on ErbB2⁺ BT474 and SKBR3 breast cancer cells, and isogenic paired cancer cell lines with lentivirus-mediated ErbB2 overexpression. Ganetespib potently inhibited cell proliferation, cell cycle progression, survival, and activation/phosphorylation of ErbB2 and key downstream effectors in ErbB2⁺ breast cancer cells. Moreover, ganetespib decreased the total protein levels of HSP90 client proteins and reduced ErbB2 protein half-life. ErbB2-overexpressing cancer cells were also more sensitive to ganetespib-mediated growth inhibition than parental cells. Ganetespib also strikingly potentiated the inhibitory effects of lapatinib in BT474 and SKBR3 cells. Ultimately, our results support the application of ganetespib-mediated HSP90 inhibition as a promising therapeutic strategy for ErbB2⁺ breast cancer.

Implications of KRAS mutations in acquired resistance to treatment in NSCLC

Rationale

KRAS is the most common and, simultaneously, the most ambiguous oncogene implicated in human cancer. Despite KRAS mutations were identified in Non Small Cell Lung Cancers (NSCLCs) more than 20 years ago, selective and specific inhibitors aimed at directly abrogating KRAS activity are not yet available. Nevertheless, many therapeutic approaches have been developed potentially useful to treat NSCLC patients mutated for KRAS and refractory to both standard chemotherapy and targeted therapies.

The focus of this review will be to provide an overview of the network related to the intricate molecular KRAS pathways, stressing on preclinical and clinical studies that investigate the predictive value of KRAS mutations in NSCLC patients.

Materials and Methods

A bibliographic search of the Medline database was conducted for articles published in English, with the keywords KRAS, KRAS mutations in non-small cell lung cancer, KRAS and tumorigenesis, KRAS and TKIs, KRAS and chemotherapy, KRAS and monoclonal antibody, KRAS and immunotherapy, KRAS and drugs, KRAS and drug resistance.

ALK and ROS1 as targeted therapy paradigms and clinical implications to overcome crizotinib resistance

During the past decade, more than 10 targetable oncogenic driver genes have been validated in non-small cell lung cancer (NSCLC). Anaplastic lymphoma kinase (ALK) and ROS1 kinase are two new driver genes implicated in ALK- and ROS1-rearranged NSCLC. Inhibition of ALK and ROS1 by crizotinib has been reported to be highly effective and well tolerated in these patients. However, resistance to crizotinib emerges years after treatment, and increasing efforts have been made to overcome this issue. Here, we review the biology of ALK and ROS1 and their roles in cancer progression. We also summarize the ongoing and completed clinical trials validating ALK and ROS1 as targets for cancer treatment. In the last section of the review, we will discuss the molecular mechanisms of crizotinib resistance and focus approaches to overcome it. This review describes an exciting new area of research and may provide new insights for targeted cancer therapies.

Molecular mechanism and targeted therapy of Hsp90 involved in lung cancer: New discoveries and developments (Review)

The exploration of the molecular mechanisms and signaling pathways on lung cancer is very important for developing new strategies of diagnosis and treatment to this disease, such as finding valuable lung cancer markers and molecularly targeted therapies. Previously, a number of studies disclose that heat shock protein 90 (Hsp90) is upregulated in cancer cells, tissues and serum of lung cancer patients, and its upregulation intimately correlates with the occurrence, development and outcome of lung cancer. On the contrary, inhibition of Hsp90 can suppress cell proliferation, motility and metastasis of lung cancer and promote apoptosis of lung cancer cells via complex signaling pathways. In addition, a series of Hsp90 inhibitors have been investigated as effective molecular targeted therapy tactics fighting against lung cancer. This review, systematically summarizes the role of Hsp90 in lung cancer, the molecular mechanisms and development of anti-Hsp90 treatment in lung cancer.

Targeting Heat Shock Proteins in Cancer: A Promising Therapeutic Approach

Heat shock proteins (HSPs) are a large family of chaperones that are involved in protein folding and maturation of a variety of "client" proteins protecting them from degradation, oxidative stress, hypoxia, and thermal stress. Hence, they are significant regulators of cellular proliferation, differentiation and strongly implicated in the molecular orchestration of cancer development and progression as many of their clients are well established oncoproteins in multiple tumor types. Interestingly, tumor cells are more HSP chaperonage-dependent than normal cells for proliferation and survival because the oncoproteins in cancer cells are often misfolded and require augmented chaperonage activity for correction. This led to the development of several inhibitors of HSP90 and other HSPs that have shown promise both preclinically and clinically in the treatment of cancer. In this article, we comprehensively review the roles of some of the important HSPs in cancer, and how targeting them could be efficacious, especially when traditional cancer therapies fail.

Reactivation of the p90RSK-CDC25C Pathway Leads to Bypass of the Ganetespib-Induced G2-M Arrest and Mediates Acquired Resistance to Ganetespib in KRAS-Mutant NSCLC

A subset of non-small cell lung cancers (NSCLC) are dependent upon oncogenic driver mutations, including the most frequently observed driver mutant KRAS, which is associated with a poor prognosis. As direct RAS targeting in the clinic has been unsuccessful to date, use of Hsp90 inhibitors appeared to be a promising therapy for KRAS-mutant NSCLC; however, limited clinical efficacy was observed due to rapid resistance. Furthermore, the combination of the Hsp90 inhibitor (Hsp90i), ganetespib, and docetaxel was tested in a phase III clinical trial and failed to demonstrate benefit. Here, we investigated the mechanism(s) of resistance to ganetespib and explored why the combination with docetaxel failed in the clinic. We have not only identified a critical role for the bypass of the G₂-M cell-cycle checkpoint as a mechanism of ganetespib resistance (GR) but have also found that GR leads to cross-resistance to docetaxel. Reactivation of p90RSK and its downstream target, CDC25C, was critical for GR and mediated the bypass of a G₂-M arrest. Overexpression of either p90RSK or CDC25C lead to bypass of G₂-M arrest and induced ganetespib resistance in vitro and in vivo Moreover, resistance was dependent on p90RSK/CDC25C signaling, as synthetic lethality to ERK1/2, p90RSK, or CDC25C inhibitors was observed. Importantly, the combination of ganetespib and p90RSK or CDC25C inhibitors was highly efficacious in parental cells. These studies provide a way forward for Hsp90 inhibitors through the development of novel rationally designed Hsp90 inhibitor combinations that may prevent or overcome resistance to Hsp90i. Mol Cancer Ther; 16(8); 1658-68. ©2017 AACR.

BIIB021: A novel inhibitor to heat shock protein 90–addicted oncology

Heat shock protein 90 is induced in response to the cell stress. Its overexpression has been reported in many cancers with poor prognosis. It acts as a chaperone to the client proteins, especially the activated oncoproteins in malignancies to protect them from degradation. Heat shock protein 90 inhibition represented anti-cancer effects in many studies. Previous natural product–based compounds are limited by their association with target toxicities. BIIB021 is an orally available, fully synthetic novel small-molecule heat shock protein 90 inhibitor that has shown strong antitumor activities in a large number of preclinical models and is now under clinical investigation. This review will summarize its therapeutic effects and highlight the prospect of targeting heat shock protein 90 in the cancer therapy.

Heat shock protein antagonists in early stage clinical trials for NSCLC

INTRODUCTION

Cancer cells have a higher need of chaperones than normal cells to prevent the toxic effects of intracellular protein misfolding and aggregation. Heat shock proteins (Hsps) belong to these chaperones; they are classified into families according to molecular size. Hsps are upregulated in many cancers and inhibition can inhibit tumor growth by destabilizing proteins necessary for tumor survival. In non-small cell lung cancer (NSCLC), there are three different Hsp antagonist classes that are in (early) clinical trials: Hsp90, Hsp70 and Hsp27 inhibitors. Areas covered: The rationale to use Hsp inhibitors in NSCLC will be summarized and phase I-III trials will be reviewed. Expert opinion: Several Hsp90 inhibitors have been tested in phase I-III trials, until now none was positive in unselected NSCLC; therefore development of AUY922, ganetespib and retaspimycin was halted. Results seem more promising in molecularly selected patients, especially in ALK-rearranged NSCLC. Hsp27 is overexpressed in squamous NSCLC and is a mechanism of chemotherapy resistance. The Hsp27 inhibitor apatorsen is now tested in squamous NSCLC. No phase II/III data are known for Hsp70 inhibitors. Combination of Hsp inhibitors with heat shock transcription factor 1 inhibitors or focal adhesion kinase inhibitors might be of interest for future trials.

Hsp90 inhibitor SY-016 induces G2/M arrest and apoptosis in paclitaxel-resistant human ovarian cancer cells

The aim of the present study was to evaluate the in vitro effect of a heat shock protein (Hsp)90 inhibitor, SY-016, on the paclitaxel (PTX)-resistant human ovarian cancer cell line OVCAR-3PTX, and explore its mechanism of apoptosis. In the present study, SY-016 was used in combination with PTX to determine its effect on the cell proliferation and apoptosis of OVCAR-3PTX cells. The drug-resistant tumor cells were established in vitro by stepwise sequential exposure to increasing concentrations of PTX. The cell viability and cell cycle distribution were measured by MTT assay and flow cytometric analysis, respectively. The induction of apoptosis was measured by caspase-3 activity, DNA fragmentation and western blot analyses. The cell viability significantly decreased following treatment with PTX and SY-016 as compared with either drug alone. The DNA fragmentation assay revealed an induction of apoptosis. The results from the flow cytometric analysis revealed an increase in the percentage of cells in the G2/M phase. Downregulation of B-cell lymphoma (Bcl)-2, X-linked inhibitor of apoptosis protein, survivin, Akt, nuclear factor-κB and cyclin-dependent kinase 4, as well as upregulation of Bcl-2-associated X protein, were observed. SY-016 may contribute to the induction of apoptosis in OVCAR-3PTX cells. These results suggest that SY-016 in combination with PTX may be a beneficial chemotherapeutic strategy, particularly in patients with tumors refractory to PTX.

Ganetespib overcomes resistance to PARP inhibitors in breast cancer by targeting core proteins in the DNA repair machinery

DNA damage repair plays essential roles in drug resistance, especially resistance to Poly (ADP-ribose) polymerase (PARP) inhibitors in the clinic. A subset of DNA repair proteins such as Breast cancer gene 1 (BRCA1), BRCA2 and RecA homolog (RAD51) are client proteins of heat shock protein 90 (Hsp90). Clearance of these DNA repair proteins by inhibition of Hsp90 is a promising strategy for overcoming resistance to PARP inhibitors. Here we report the pharmacological analysis of the highly potent second-generation Hsp90 inhibitor, ganetespib. Methods Nuclear BRCA1, BRCA2, and RAD51 expression in breast cancer cells were detected by subcellular fractionation and western blot analysis. Formation of nuclear RAD51 and γ-H2AX foci was analyzed by immunofluorescent staining. The cytotoxicity of ganetespib and ABT-888 in breast cancer cells were evaluated by cell proliferation, colony survival, and apoptosis assay. To investigate the efficacy of this therapy in vivo, SCID mice bearing MCF7 xenografts were treated with ganetespib and ABT-888, both as single agents and in combination. Results Ganetespib significantly destabilized nuclear BRCA1, BRCA2, and RAD51, and efficiently disrupted homologous recombination-mediated DNA double-strand break repair in breast cancer cells. The synergistic antitumor effects of ganetespib and the PARP inhibitor, ABT-888 were observed, and concurrent treatment with both inhibitors synergistically inhibited xenograft tumor growth. Importantly, the combined treatment was well tolerated, without significant loss of body weight or major histological changes in the breast cancer xenograft model. Conclusion These data provide a novel strategy for the treatment of breast cancer with wild type BRCA1 using combination therapy targeting Hsp90 to overcome resistance to PARP inhibitors.

Role of 14-3-3 sigma in over-expression of P-gp by rifampin and paclitaxel stimulation through interaction with PXR

In this study, we presented the role of 14-3-3σ to activate CK2-Hsp90β-PXR-MDR1 pathway on rifampin and paclitaxel treated LS174T cells and in vivo LS174T cell-xenografted nude mouse model. Following several in vitro and in vivo experiments, rifampin and paclitaxel were found to be stimulated the CK2-Hsp90β-PXR-MDR1 pathway. Of the proteins in this pathway, Pregnane X receptor (PXR) is a representative transcription factor of multidrug resistance protein 1 (MDR1). We constructed FLAG-PXR-LS174T stable cell lines and discovered 22 proteins that interacted with PXR on rifampin treatment. Among them, Hsp90β and 14-3-3σ were isolated for further study. Both the proteins were found to be localized in cytoplasm on rifampin treatment by using confocal microscopy. On the other hand, PXR was found to be localized in nucleus after rifampin and paclitaxel treatment by using cell fractionation assay. In Western blot analysis, rifampin did not influence the expression of 14-3-3σ protein. Transient transfection of 14-3-3σ into LS174T cells induced overexpression of PXR; however, P-glycoprotein (P-gp) was not changed significantly. P-gp overexpression was induced only when 14-3-3σ transfected LS174T cells were treated with rifampin and paclitaxel, whereas 14-3-3σ inhibition by nonpeptidic inhibitor, BV02 and 14-3-3σ siRNA reduced rifampin induced PXR and P-gp expression. Cell survival rates were much higher at 14-3-3σ-LS174T stable cell lines than LS174T cells following paclitaxel and vincristine treatment. This data indicates that 14-3-3σ contributes to P-gp overexpression through interaction with PXR with rifampin and paclitaxel treatment.

Radioresistant human lung adenocarcinoma cells that survived multiple fractions of ionizing radiation are sensitive to HSP90 inhibition

Despite the common usage of radiotherapy for the treatment of NSCLC, outcomes for these cancers when treated with ionizing radiation (IR) are still unsatisfactory. A better understanding of the mechanisms underlying resistance to IR is needed to design approaches to eliminate the radioresistant cells and prevent tumor recurrence and metastases. Using multiple fractions of IR we generated radioresistant cells from T2821 and T2851 human lung adenocarcinoma cells. The radioresistant phenotypes present in T2821/R and T2851/R cells include multiple changes in DNA repair genes and proteins expression, upregulation of EMT markers, alterations of cell cycle distribution, upregulation of PI3K/AKT signaling and elevated production of growth factors, cytokines, important for lung cancer progression, such as IL-6, PDGFB and SDF-1 (CXCL12). In addition to being radioresistant these cells were also found to be resistant to cisplatin.

HSP90 is a molecular chaperone involved in stabilization and function of multiple client proteins implicated in NSCLC cell survival and radioresistance. We examined the effect of ganetespib, a novel HSP90 inhibitor, on T2821/R and T2851/R cell survival, migration and radioresistance. Our data indicates that ganetespib has cytotoxic activity against parental T2821 and T2851 cells and radioresistant T2821/R and T2851/R lung tumor cells. Ganetespib does not affect proliferation of normal human lung fibroblasts. Combining IR with ganetespib completely abrogates clonogenic survival of radioresistant cells.

Our data show that HSP90 inhibition can potentiate the effect of radiotherapy and eliminate radioresistant and cisplatin -resistant residual cells, thus it may aid in reducing NSCLC tumor recurrence after fractionated radiotherapy.

Molecular targets in urothelial cancer: detection, treatment, and animal models of bladder cancer

Bladder cancer remains one of the most expensive cancers to treat in the United States due to the length of required treatment and degree of recurrence. In order to treat bladder cancer more effectively, targeted therapies are being investigated. In order to use targeted therapy in a patient, it is important to provide a genetic background of the patient. Recent advances in genome sequencing, as well as transcriptome analysis, have identified major pathway components altered in bladder cancer. The purpose of this review is to provide a broad background on bladder cancer, including its causes, diagnosis, stages, treatments, animal models, as well as signaling pathways in bladder cancer. The major focus is given to the PI3K/AKT pathway, p53/pRb signaling pathways, and the histone modification machinery. Because several promising immunological therapies are also emerging in the treatment of bladder cancer, focus is also given on general activation of the immune system for the treatment of bladder cancer.

Hsp90 Inhibitor Ganetespib Sensitizes Non-Small Cell Lung Cancer to Radiation but Has Variable Effects with Chemoradiation

PURPOSE

HSP90 inhibition is well known to sensitize cancer cells to radiation. However, it is currently unknown whether additional radiosensitization could occur in the more clinically relevant setting of chemoradiation (CRT). We used the potent HSP90 inhibitor ganetespib to determine whether it can enhance CRT effects in NSCLC.

EXPERIMENTAL DESIGN

We first performed in vitro experiments in various NSCLC cell lines combining radiation with or without ganetespib. Some of these experiments included clonogenic survival assay, DNA damage repair, and cell-cycle analysis, and reverse-phase protein array. We then determined whether chemotherapy affected ganetespib radiosensitization by adding carboplatin-paclitaxel to some of the in vitro and in vivo xenograft experiments.

RESULTS

Ganetespib significantly reduced radiation clonogenic survival in a number of lung cancer cell lines, and attenuated DNA damage repair with irradiation. Radiation caused G₂-M arrest that was greatly accentuated by ganetespib. Ganetespib with radiation also dose-dependently upregulated p21 and downregulated pRb levels that were not apparent with either drug or radiation alone. However, when carboplatin-paclitaxel was added, ganetespib was only able to radiosensitize some cell lines but not others. This variable in vitro CRT effect was confirmed in vivo using xenograft models.

CONCLUSIONS

Ganetespib was able to potently sensitize a number of NSCLC cell lines to radiation but has variable effects when added to platinum-based doublet CRT. For optimal clinical translation, our data emphasize the importance of preclinical testing of drugs in the context of clinically relevant therapy combinations. Clin Cancer Res; 22(23); 5876-86. ©2016 AACR.

HSP90 as a novel molecular target in non-small-cell lung cancer

Lung cancer remains the most lethal cancer, with over 160,000 annual deaths in the USA alone. Over the past decade, the discovery of driver mutations has changed the landscape for the treatment of non-small-cell lung cancer (NSCLC). Targeted therapies against epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) have now been approved by the Food and Drug Administration as part of the standard first-line treatment of NSCLC. Despite good initial responses, most patients develop resistance within 8–12 months and have disease progression.

Development of Heat Shock Protein (Hsp90) Inhibitors To Combat Resistance to Tyrosine Kinase Inhibitors through Hsp90-Kinase Interactions

Heat shock protein 90 (Hsp90) is a ubiquitous chaperone of all of the oncogenic tyrosine kinases. Many Hsp90 inhibitors, alone or in combination, have shown significant antitumor efficacy against the kinase-positive naïve and mutant models. However, clinical trials of these inhibitors are unsuccessful due to insufficient clinical benefits and nonoptimal safety profiles. Recently, much progress has been reported on the Hsp90-cochaperone-client complex, which will undoubtedly assist in the understanding of the interactions between Hsp90 and its clients. Meanwhile, Hsp90 inhibitors have shown promise against patients' resistance caused by early generation tyrosine kinase inhibitors (TKIs), and at least 13 Hsp90 inhibitors are being reevaluated in the clinic. In this regard, the objectives of the current perspective are to summarize the structure and function of the Hsp90-cochaperone-client complex, to analyze the structural and functional insights into the Hsp90-client interactions to address several existing unresolved problems with Hsp90 inhibitors, and to highlight the preclinical and clinical studies of Hsp90 inhibitors as an effective treatment against resistance to tyrosine kinase inhibitors.

Treating patients with ALK-positive non-small cell lung cancer: latest evidence and management strategy

Rearrangements in anaplastic lymphoma kinase (ALK) gene and echinoderm microtubule-associated protein-like 4 (EML4) gene were first described in a small portion of patients with non-small cell lung cancer (NSCLC) in 2007. Fluorescence in situ hybridization is used as the diagnostic test for detecting an EML4-ALK rearrangement. Crizotinib, an ALK inhibitor, is effective in treating advanced ALK-positive NSCLC, and the US Food and Drug Administration approved it for treating ALK-positive NSCLC in 2011. Several mechanisms of acquired resistance to crizotinib have recently been reported. Second-generation ALK inhibitors were designed to overcome these resistance mechanisms. Two of them, ceritinib and alectinib, were approved in 2014 for advanced ALK-positive NSCLC in the US and Japan, respectively. Heat shock protein 90 (Hsp90) inhibitors also showed activity against ALK-positive NSCLC. Here we review the recent development of crizotinib, ceritinib, alectinib and other second-generation ALK inhibitors as well as Hsp90 inhibitors. We also discuss management strategies for advanced ALK-positive NSCLC.

Ganetespib: research and clinical development

Under stressful conditions, the heat shock protein 90 (HSP90) molecular chaperone protects cellular proteins (client proteins) from degradation via the ubiquitin-proteasome pathway. HSP90 expression is upregulated in cancers, and this contributes to the malignant phenotype of increased proliferation and decreased apoptosis and maintenance of metastatic potential via conservation of its client proteins, including human epidermal growth factor receptor 2, anaplastic lymphoma kinase, androgen receptor, estrogen receptor, Akt, Raf-1, cell cycle proteins, and B-cell lymphoma 2 among others. Hence, inhibition of HSP90 leads to the simultaneous degradation of its many clients, thereby disrupting multiple oncogenic signaling cascades. This has sparked tremendous interest in the development of HSP90 inhibitors as an innovative anticancer strategy. Based on the wealth of compelling data from preclinical studies, a number of HSP90 inhibitors have entered into clinical testing. However, despite enormous promise and anticancer activity reported to date, none of the HSP90 inhibitors in development has been approved for cancer therapy, and the full potential of this class of agents is yet to be realized. This article provides a review on ganetespib, a small molecule HSP90 inhibitor that is currently under evaluation in a broad range of cancer types in combination with other therapeutic agents with the hope of further enhancing its efficacy and overcoming drug resistance. Based on our current understanding of the complex HSP90 machinery combined with the emerging data from these key clinical trials, ganetespib has the potential to be the first-in-class HSP90 inhibitor to be approved as a new anticancer therapy.

[New targets and new drugs in thoracic oncology]

A number of mechanisms that drive oncogenesis have been deciphered over the last 20 years. The main oncogenic factors in the field of thoracic oncology are mutations of EGFR, KRAS, and EML4-ALK translocation, which are most often reported in adenocarcinomas. However, new molecular targets have been highlighted recently including BRAF mutations, HER2 or PI3K, new translocations such as ROS1 or KIF5B-RET. Molecular abnormalities have also been identified in tumors other than adenocarcinoma (squamous and small cell carcinoma). Therapeutic strategies have been designed to inhibit these signaling pathways including monoclonal antibodies and tyrosine kinase inhibitors. Some of these molecules are now approved as therapies, others are currently undergoing testing in clinical trials. We here present a review of novel targeted agents for lung cancer.

The HSP90 inhibitor ganetespib potentiates the antitumor activity of EGFR tyrosine kinase inhibition in mutant and wild-type non-small cell lung cancer

Small molecule inhibitors of epidermal growth factor receptor (EGFR) tyrosine kinase activity, such as erlotinib and gefitinib, revolutionized therapy for non-small cell lung cancer (NSCLC) patients whose tumors harbor activating EGFR mutations. However, mechanisms to overcome the invariable development of acquired resistance to such agents, as well as realizing their full clinical potential within the context of wild-type EGFR (WT-EGFR) disease, remain to be established. Here, the antitumor efficacy of targeted EGFR tyrosine kinase inhibitors (TKIs) and the HSP90 inhibitor ganetespib, alone and in combination, were evaluated in NSCLC. Ganetespib potentiated the efficacy of erlotinib in TKI-sensitive, mutant EGFR-driven NCI-HCC827 xenograft tumors, with combination treatment causing significant tumor regressions. In erlotinib-resistant NCI-H1975 xenografts, concurrent administration of ganetespib overcame erlotinib resistance to significantly improve tumor growth inhibition. Ganetespib co-treatment also significantly enhanced antitumor responses to afatinib in the same model. In WT-EGFR cell lines, ganetespib potently reduced cell viability. In NCI-H1666 cells, ganetespib-induced loss of client protein expression, perturbation of oncogenic signaling pathways, and induction of apoptosis translated to robust single-agent activity in vivo. Dual ganetespib/erlotinib therapy induced regressions in NCI-H322 xenograft tumors, indicating that the sensitizing properties of ganetespib for erlotinib were conserved within the WT-EGFR setting. Mechanistically, combined ganetespib/erlotinib exposure stabilized EGFR protein levels in an inactive state and completely abrogated extracellular-signal-regulated kinase (ERK) and AKT signaling activity. Thus, selective HSP90 blockade by ganetespib represents a potentially important complementary strategy to targeted TKI inhibition alone for inducing substantial antitumor responses and overcoming resistance, in both the mutant and WT-EGFR settings.

The HSP90 Inhibitor Ganetespib Radiosensitizes Human Lung Adenocarcinoma Cells

The molecular chaperone HSP90 is involved in stabilization and function of multiple client proteins, many of which represent important oncogenic drivers in NSCLC. Utilization of HSP90 inhibitors as radiosensitizing agents is a promising approach. The antitumor activity of ganetespib, HSP90 inhibitor, was evaluated in human lung adenocarcinoma (AC) cells for its ability to potentiate the effects of IR treatment in both in vitro and in vivo. The cytotoxic effects of ganetespib included; G2/M cell cycle arrest, inhibition of DNA repair, apoptosis induction, and promotion of senescence. All of these antitumor effects were both concentration- and time-dependent. Both pretreatment and post-radiation treatment with ganetespib at low nanomolar concentrations induced radiosensitization in lung AC cells in vitro. Ganetespib may impart radiosensitization through multiple mechanisms: such as down regulation of the PI3K/Akt pathway; diminished DNA repair capacity and promotion of cellular senescence. In vivo, ganetespib reduced growth of T2821 tumor xenografts in mice and sensitized tumors to IR. Tumor irradiation led to dramatic upregulation of β-catenin expression in tumor tissues, an effect that was mitigated in T2821 xenografts when ganetespib was combined with IR treatments. These data highlight the promise of combining ganetespib with IR therapies in the treatment of AC lung tumors.

A randomized phase II study of ganetespib, a heat shock protein 90 inhibitor, in combination with docetaxel in second-line therapy of advanced non-small cell lung cancer (GALAXY-1)

BACKGROUND

This trial was designed to evaluate the activity and safety of ganetespib in combination with docetaxel in advanced non-small cell lung cancer (NSCLC) and to identify patient populations most likely to benefit from the combination.

PATIENTS AND METHODS

Patients with one prior systemic therapy for advanced disease were eligible. Docetaxel (75 mg/m(2) on day 1) was administered alone or with ganetespib (150 mg/m(2) on days 1 and 15) every 3 weeks. The primary end points were progression-free survival (PFS) in two subgroups of the adenocarcinoma population: patients with elevated lactate dehydrogenase (eLDH) and mutated KRAS (mKRAS).

RESULTS

Of 385 patients enrolled, 381 were treated. Early in the trial, increased hemoptysis and lack of efficacy were observed in nonadenocarcinoma patients (n = 71); therefore, only patients with adenocarcinoma histology were subsequently enrolled. Neutropenia was the most common grade ≥3 adverse event: 41% in the combination arm versus 42% in docetaxel alone. There was no improvement in PFS for the combination arm in the eLDH (N = 114, adjusted hazard ratio (HR) = 0.77, P = 0.1134) or mKRAS (N = 89, adjusted HR = 1.11, P = 0.3384) subgroups. In the intent-to-treat adenocarcinoma population, there was a trend in favor of the combination, with PFS (N = 253, adjusted HR = 0.82, P = 0.0784) and overall survival (OS) (adjusted HR = 0.84, P = 0.1139). Exploratory analyses showed significant benefit of the ganetespib combination in the prespecified subgroup of adenocarcinoma patients diagnosed with advanced disease >6 months before study entry (N = 177): PFS (adjusted HR = 0.74, P = 0.0417); OS (adjusted HR = 0.69, P = 0.0191).

CONCLUSION

Advanced lung adenocarcinoma patients treated with ganetespib in combination with docetaxel had an acceptable safety profile. While the study's primary end points were not met, significant prolongation of PFS and OS was observed in patients >6 months from diagnosis of advanced disease, a subgroup chosen as the target population for the phase III study.

Casein Kinase 2 (CK2)-mediated Phosphorylation of Hsp90β as a Novel Mechanism of Rifampin-induced MDR1 Expression

The P-glycoprotein (P-gp) encoded by the MDR1 gene is a drug-exporting transporter located in the cellular membrane. P-gp induction is regarded as one of the main mechanisms underlying drug-induced resistance. Although there is great interest in the regulation of P-gp expression, little is known about its underlying regulatory mechanisms. In this study, we demonstrate that casein kinase 2 (CK2)-mediated phosphorylation of heat shock protein 90β (Hsp90β) and subsequent stabilization of PXR is a key mechanism in the regulation of MDR1 expression. Furthermore, we show that CK2 is directly activated by rifampin. Upon exposure to rifampin, CK2 catalyzes the phosphorylation of Hsp90β at the Ser-225/254 residues. Phosphorylated Hsp90β then interacts with PXR, causing a subsequent increase in its stability, leading to the induction of P-gp expression. In addition, inhibition of CK2 and Hsp90β enhances the down-regulation of PXR and P-gp expression. The results of this study may facilitate the development of new strategies to prevent multidrug resistance and provide a plausible mechanism for acquired drug resistance by CK2-mediated regulation of P-gp expression.

The effect of 17-allylamino-17-demethoxygeldanamycin alone or in combination with paclitaxel on anaplastic thyroid carcinoma cells

The effect of 17-allylamino-17-demethoxygeldanamycin (17-AAG), an hsp90 inhibitor, alone or in combination with paclitaxel on survival of anaplastic thyroid carcinoma (ATC) was evaluated. In 8505C and CAL62 cells, after treatment of 17-AAG, cell viability decreased, and the percentage of dead cells increased. 17-AAG did not cause cleavage of caspase-3 protein, and change expression of IAPs. Pretreatment of z-VAD-fmk did not alter cell viability and the percentage of dead cells. In 17-AAG-treated cells, knockdown of p53 rescued growth inhibition, while cycloheximide attenuated cell death. When cells were treated with both 17-AAG and paclitaxel, all of the combination index values were higher than 1, indicating antagonism between 17-AAG and paclitaxel. In 17-AAG- and paclitaxel-treated cells, compared with paclitaxel alone-treated cells, the protein levels of hsp90, hsp70, and hsc70 increased. In conclusion, our results suggest that 17-AAG induces non-apoptotic cell death requiring de novo protein synthesis in ATC cells. Moreover, these results demonstrate that 17-AAG antagonizes paclitaxel with concomitant alterations in hsp90 client proteins in ATC cells.

High-level expression of Hsp90β is associated with poor survival in resectable non-small-cell lung cancer patients

AIMS

The aim of this study was to investigate the expression of Hsp90β and GRP94, and elucidate the clinical significance of their expression, in patients with resectable non-small-cell lung cancer (NSCLC).

METHODS AND RESULTS

Surgical tissue specimens were obtained from 208 patients with NSCLC who underwent surgical resection. The expression levels of Hsp90β and GRP94 were assessed with tissue microarrays and immunohistochemistry. No correlations were observed between Hsp90β or GRP94 expression and several clinicopathological factors. The high-Hsp90β group [median overall survival (OS) 20.4 months; 95% confidence interval (CI) 0.000-40.864] showed a significant decrease in OS as compared with the low-Hsp90β group (median OS not reached; P = 0.003). In contrast to the Hsp90β analysis, the GRP94 analysis did not show a difference in OS. Moreover, in subgroup analyses of patients with squamous cell carcinoma histology, OS (P = 0.012) and relapse-free survival (P = 0.044) were significantly worse in the high-Hsp90β group than in the low-Hsp90β group. Multivariate analysis suggested that old age [hazard ratio (HR) 1.568; 95% CI 1.019-2.412; P = 0.041], advanced disease (HR 2.066; 95% CI 1.218-3.502; P = 0.007) and high Hsp90β expression (HR 1.802; 95% CI 1.061-3.060; P = 0.029) were independent poor prognostic factors for OS.

CONCLUSIONS

Hsp90β expression might be a useful marker of poor OS, although further large prospective studies are warranted to validate our findings.

HSP90 inhibition enhances antimitotic drug-induced mitotic arrest and cell death in preclinical models of non-small cell lung cancer

HSP90 inhibitors are currently undergoing clinical evaluation in combination with antimitotic drugs in non-small cell lung cancer (NSCLC), but little is known about the cellular effects of this novel drug combination. Therefore, we investigated the molecular mechanism of action of IPI-504 (retaspimycin HCl), a potent and selective inhibitor of HSP90, in combination with the microtubule targeting agent (MTA) docetaxel, in preclinical models of NSCLC. We identified a subset of NSCLC cell lines in which these drugs act in synergy to enhance cell death. Xenograft models of NSCLC demonstrated tumor growth inhibition, and in some cases, regression in response to combination treatment. Treatment with IPI-504 enhanced the antimitotic effects of docetaxel leading to the hypothesis that the mitotic checkpoint is required for the response to drug combination. Supporting this hypothesis, overriding the checkpoint with an Aurora kinase inhibitor diminished the cell death synergy of IPI-504 and docetaxel. To investigate the molecular basis of synergy, an unbiased stable isotope labeling by amino acids in cell culture (SILAC) proteomic approach was employed. Several mitotic regulators, including components of the ubiquitin ligase, anaphase promoting complex (APC/C), were specifically down-regulated in response to combination treatment. Loss of APC/C by RNAi sensitized cells to docetaxel and enhanced its antimitotic effects. Treatment with a PLK1 inhibitor (BI2536) also sensitized cells to IPI-504, indicating that combination effects may be broadly applicable to other classes of mitotic inhibitors. Our data provide a preclinical rationale for testing the combination of IPI-504 and docetaxel in NSCLC.

Hsp90 inhibitor as a sensitizer of cancer cells to different therapies (review)

Hsp90 is a molecular chaperone that maintains the structural and functional integrity of various client proteins involved in signaling and many other functions of cancer cells. The natural inhibitors, ansamycins influence the Hsp90 chaperone function by preventing its binding to client proteins and resulting in their proteasomal degradation. N- and C-terminal inhibitors of Hsp90 and their analogues are widely tested as potential anticancer agents in vitro, in vivo as well as in clinical trials. It seems that Hsp90 competitive inhibitors target different tumor types at nanomolar concentrations and might have therapeutic benefit. On the contrary, some Hsp90 inhibitors increased toxicity and resistance of cancer cells induced by heat shock response, and through the interaction of survival signals, that occured as side effects of treatments, could be very effectively limited via combination of therapies. The aim of our review was to collect the data from experimental and clinical trials where Hsp90 inhibitor was combined with other therapies in order to prevent resistance as well as to potentiate the cytotoxic and/or antiproliferative effects.

Combination of SNX-2112 with 5-FU exhibits antagonistic effect in esophageal cancer cells

The low efficacy of single-drug chemotherapy forms the basis for combination therapy in esophageal squamous cell carcinoma. SNX-2112, a selective heat shock protein 90 (Hsp90) inhibitor, was recently reported as being effective in combination with cisplatin and paclitaxel. In this study, we investigated the effect of SNX-2112 in combination with 5-fluorouracil (5-FU), another first-line anticancer drug, in esophageal cancer. Unexpectedly, tetrazolium assay revealed that the combination of SNX-2112 with 5-FU exhibited antagonistic effect. Flow cytometry revealed that the SNX-2112 and 5-FU combination greatly decreased the number of G2/M cells compared to SNX-2112-only treatment in Eca‑109 cells. This effect might be related to the altered mRNA level of cyclin-related genes including cyclin D1, Chk2 and Cdk4. Further, 5-FU attenuated SNX-2112-induced apoptosis by decreasing poly(ADP-ribose) polymerase (PARP) cleavage and inactivating caspase-3, -8 and -9. Additionally, 5-FU suppressed the SNX-2112-induced decrease of mitochondrial membrane potential. Moreover, 5-FU partly recovered Hsp90 client proteins, including Akt, p-Akt, inhibitor of κB kinase (IKK)α, extracellular signal-regulated kinase (ERK)1/2, and glycogen synthase kinase (GSK)-3β, which SNX-2112 had downregulated. Taken together, this is the first report that the combination of SNX-2112 with 5-FU exhibited antagonistic effect in esophageal cancer cells by affecting growth inhibition, cell cycle, apoptosis, and Hsp90 client proteins, suggesting that care is required in the clinical application of combined SNX-2112 and 5-FU.

HSP-90 inhibitor ganetespib is synergistic with doxorubicin in small cell lung cancer

Small cell lung cancer (SCLC) at advanced stage is considered an incurable disease. Despite good response to initial chemotherapy, the responses in SCLC patients with metastatic disease are of short duration and resistance inevitably occurs. Although several target-specific drugs have altered the paradigm of treatment for many other cancers, we have yet to witness a revolution of the same magnitude in SCLC treatment. Anthracyclines, such as doxorubicin, have definite activity in this disease, and ganetespib has shown promising activity in preclinical models but underwhelming activity as a single agent in SCLC patients. Using SCLC cell lines, we demonstrated that ganetespib (IC50: 31 nM) was much more potent than 17-allylamino-17-demethoxygeldanamycin (17-AAG), a geldanamycin derivative (IC50: 16 μM). Ganetespib inhibited SCLC cell growth via induction of persistent G2/M arrest and Caspase 3-dependent cell death. MTS assay revealed that ganetespib synergized with both doxorubicin and etoposide, two topoisomerase II inhibitors commonly used in SCLC chemotherapy. Expression of receptor-interacting serine/threonine-protein kinase 1 (RIP1), a protein that may function as a pro-survival scaffold protein or a pro-death kinase in TNFR1-activated cells, was induced by doxorubicin and downregulated by ganetespib. Depletion of RIP1 by either RIP1 small interfering RNA (siRNA) or ganetespib sensitized doxorubicin-induced cell death, suggesting that RIP1 may promote survival in doxorubicin-treated cells and that ganetespib may synergize with doxorubicin in part through the downregulation of RIP1. In comparison to ganetespib or doxorubicin alone, the ganetespib+doxorubicin combination caused significantly more growth regression and death of human SCLC xenografts in immunocompromised mice. We conclude that ganetespib and doxorubicin combination exhibits significant synergy and is efficacious in inhibiting SCLC growth in vitro and in mouse xenograft models. Our preclinical study suggests that ganetespib and doxorubicin combination therapy may be an effective strategy for SCLC treatment, which warrants clinical testing.

Heat shock protein 90 inhibitors in non-small-cell lung cancer

PURPOSE OF REVIEW

Heat shock protein 90 (Hsp90) protects cellular proteins from degradation by the ubiquitin-proteasome system in conditions of stress. Many cancers have increased expression of Hsp90 to ensure their malignant phenotype of increased proliferation, decreased apoptosis, and metastatic potential by conservation of proteins like epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2, anaplastic lymphoma kinase (ALK), v-Raf murine sarcoma viral oncogene homologue B1, AKT, B-cell lymphoma 2, and cell cycle proteins. This review discusses recent developments in the strategy of Hsp90 inhibition as a targeted therapy in non-small-cell lung cancer (NSCLC).

RECENT FINDINGS

Hsp90 inhibitors result in growth inhibition and tumor regression in NSCLC cell lines and tumor xenograft models, both as monotherapy and in combination with other drugs. Hsp90 inhibition has particular efficacy in molecular subtypes of NSCLC, such as EGFR-mutated and ALK-rearranged NSCLC. IPI-504 and ganetespib have activity in NSCLC both as monotherapy and in combination with docetaxel.

SUMMARY

Preclinical studies and early clinical trials have confirmed the efficacy of Hsp90 inhibition as a targeted therapy in NSCLC. Ongoing trials will further define the utility of Hsp90 inhibitors in NSCLC.

Heat shock protein 90 promotes epithelial to mesenchymal transition, invasion, and migration in colorectal cancer

Epithelial to mesenchymal transition (EMT), invasion, and motility are essential steps in colorectal cancer (CRC) metastasis regulated by HIF-1α and NF-κB. Since HSP90 activates HIF-1α and NF-κB, we hypothesized that inhibition of HSP90 leads to inhibition of HIF-1α and NF-κB resulting in inhibition of EMT, invasion, and motility. Treatment of colorectal cancer cell lines HT-29 and HCT-116 with ganetespib at 50 nM for 24 h inhibited EMT (downregulated vimentin and upregulated E-cadherin), matrigel invasion, and spheroid migration. Ganetespib treatment or HSP90 knockdown downregulated molecular pathways associated with EMT, invasion, and motility. The overexpression of HIF-1α or NF-κB resulted in increased EMT, invasion, and motility in both cell lines and these effects were inhibited by ganetespib. Similar effects were observed in animal xenografts treated with ganetespib. Taken together, our data demonstrate for the first time that inhibition of HSP90 downregulates both HIF-1α and NF-κB leading to inhibition of EMT, motility, and invasiveness in colorectal cancer.

The HSP90 inhibitor ganetespib has chemosensitizer and radiosensitizer activity in colorectal cancer

The integration of targeted agents to standard cytotoxic regimens has improved outcomes for patients with colorectal cancer (CRC) over recent years; however this malignancy remains the second leading cause of cancer mortality in industrialized countries. Small molecule inhibitors of heat shock protein 90 (HSP90) are one of the most actively pursued classes of compounds for the development of new cancer therapies. Here we evaluated the activity of ganetespib, a second-generation HSP90 inhibitor, in models of CRC. Ganetespib reduced cell viability in a panel of CRC cell lines in vitro with low nanomolar potency. Mechanistically, drug treatment exerted concomitant effects on multiple oncogenic signaling pathways, cell cycle regulation, and DNA damage repair capacity to promote apoptosis. Combinations of ganetespib and low-dose ionizing radiation enhanced the radiosensitivity of HCT 116 cells and resulted in superior cytotoxic activity over either treatment alone. In vivo, the single-agent activity of ganetespib was relatively modest, suppressing HCT 116 xenograft tumor growth by approximately half. However, ganetespib significantly potentiated the antitumor efficacy of the 5-Fluorouracil (5-FU) prodrug capecitabine in HCT 116 xenografts, causing tumor regressions in a model that is intrinsically resistant to fluoropyrimidine therapy. This demonstration of combinatorial benefit afforded by an HSP90 inhibitor to a standard CRC adjuvant regimen provides an attractive new framework for the potential application of ganetespib as an investigational agent in this disease.