Targeting HSP70 and GRP78 in canine osteosarcoma cells in combination with doxorubicin chemotherapy

Cell surface GRP78: a potential mechanism of therapeutic resistant tumors

GRP78 is a protein that acts as a chaperone within the endoplasmic reticulum (ER) and has multiple functions. It is induced by stress and abets cells from survival. Despite, multiple Stress conditions like ER, chronic psychological and nutritional stress, hypoxia, chemotherapy, radiation therapy, and drug resistance induce cell surface GRP78 (CS-GRP78) expression in cancer cells. Further, CS-GRP78 is associated with increased malignancy and resistance to anti-cancer therapies and is considered a high-value druggable target. Recent preclinical research suggests that targeting CS-GRP78 with anti-GRP78 monoclonal antibodies (Mab) in combination with other agents may be effective in reversing the failure of chemotherapy, radiotherapy, or targeted therapies and increasing the efficacy of solid tumors treatment. This article will review recent evidence on the role of CS-GRP78 in developing resistance to anti-cancer treatments and the potential benefits of combining anti-GRP78 Mab with other cancer therapies for specific patient populations. Furthermore, our limited understanding of how CS-GRP78 regulated in human studies is a major drawback for designing effective CS-GRP78-targeted therapies. Hence, more research is still warranted to translate these potential therapies into clinical applications.

Synthetic Small Molecule Modulators of Hsp70 and Hsp40 Chaperones as Promising Anticancer Agents

A class of chaperones dubbed heat shock protein 70 (Hsp70) possesses high relevance in cancer diseases due to its cooperative activity with the well-established anticancer target Hsp90. However, Hsp70 is closely connected with a smaller heat shock protein, Hsp40, forming a formidable Hsp70-Hsp40 axis in various cancers, which serves as a suitable target for anticancer drug design. This review summarizes the current state and the recent developments in the field of (semi-)synthetic small molecule inhibitors directed against Hsp70 and Hsp40. The medicinal chemistry and anticancer potential of pertinent inhibitors are discussed. Since Hsp90 inhibitors have entered clinical trials but have exhibited severe adverse effects and drug resistance formation, potent Hsp70 and Hsp40 inhibitors may play a significant role in overcoming the drawbacks of Hsp90 inhibitors and other approved anticancer drugs.

Hyaluronic Acid Nanoparticles for Immunogenic Chemotherapy of Leukemia and T-Cell Lymphoma

Ratiometric delivery of combination chemotherapy can achieve therapeutic efficacy based on synergistic interactions between drugs. It is critical to design such combinations with drugs that complement each other and reduce cancer growth through multiple mechanisms. Using hyaluronic acid (HA) as a carrier, two chemotherapeutic agents—doxorubicin (DOX) and camptothecin (CPT)—were incorporated and tested for their synergistic potency against a broad panel of blood-cancer cell lines. The pair also demonstrated the ability to achieve immunogenic cell death by increasing the surface exposure levels of Calreticulin, thereby highlighting its ability to induce apoptosis via an alternate pathway. Global proteomic profiling of cancer cells treated with HA–DOX–CPT identified pathways that could potentially predict patient sensitivity to HA–DOX–CPT. This lays the foundation for further exploration of integrating drug delivery and proteomics in personalized immunogenic chemotherapy.

7,8-Dihydroxyflavone suppresses proliferation and induces apoptosis of human osteosarcoma cells

Recent studies suggest that 7,8-dihydroxyflavone (7,8-DHF) inhibits the development of several tumors. However, its role in osteosarcoma (OS) remains unknown. This study was designed to investigate the effects and underlying mechanisms of 7,8-DHF that may influence OS development. Human OS cell lines (U2OS and 143B) were treated with 7,8-DHF; cell viability and cell migration were assessed by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and wound-healing assay, respectively; and cell death and apoptosis were evaluated by LIVE/DEAD staining and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay, respectively. Reactive oxygen species production was measured using 2,7-dichlorodihydrofluorescein diacetate probe. Akt, Bcl-xL/Bcl-2 asociated death promoter (Bad), p38 mitogen-activated protein kinase (MAPK), extracellular regulated protein kinase (ERK), and c-Jun N-terminal kinase (JNK) expression and their respective phosphorylation levels were detected by western blot analysis. We found that 7,8-DHF reduced cell viability in a dose-dependent manner and also promoted apoptosis, inhibited migration, and induced oxidative stress in OS cells. Moreover, 7,8-DHF inhibited Akt, Bad, and p38MAPK, but activated ERK and JNK signals. In summary, our results suggest that 7,8-DHF inhibits OS progression, possibly by regulating Akt/Bad and MAPK signaling. These findings provide new evidence for the pharmacological effects of 7,8-DHF that may improve drug therapy for OS patients.

Molecular Chaperones in Osteosarcoma: Diagnosis and Therapeutic Issues

Osteosarcoma (OS) is the most common form of primary bone tumor affecting mainly children and young adults. Despite therapeutic progress, the 5-year survival rate is 70%, but it drops drastically to 30% for poor responders to therapies or for patients with metastases. Identifying new therapeutic targets is thus essential. Heat Shock Proteins (HSPs) are the main effectors of Heat Shock Response (HSR), the expression of which is induced by stressors. HSPs are a large family of proteins involved in the folding and maturation of other proteins in order to maintain proteostasis. HSP overexpression is observed in many cancers, including breast, prostate, colorectal, lung, and ovarian, as well as OS. In this article we reviewed the significant role played by HSPs in molecular mechanisms leading to OS development and progression. HSPs are directly involved in OS cell proliferation, apoptosis inhibition, migration, and drug resistance. We focused on HSP27, HSP60, HSP70 and HSP90 and summarized their potential clinical uses in OS as either biomarkers for diagnosis or therapeutic targets. Finally, based on different types of cancer, we consider the advantage of targeting heat shock factor 1 (HSF1), the major transcriptional regulator of HSPs in OS.

Dog breeds and body conformations with predisposition to osteosarcoma in the UK: a case-control study

Background

Osteosarcoma is an aggressive and painful bone neoplasm in dogs. Previous studies have reported epidemiological associations suggesting that large body mass, long bone length and the genetics of certain breeds including the Rottweiler are associated with elevated osteosarcoma risk. However, these studies were often limited by selection bias and confounding factors, and have rarely offered insights into breed-associated protection for osteosarcoma. The current study includes 1756 appendicular and axial osteosarcoma cases presenting to VPG Histology (Bristol, UK) compared against a control population of 905,211 dogs without osteosarcoma from primary care electronic patient records in the VetCompass™ dataset.

Methods and study design

Retrospective, case-control study. Multivariable logistic regression analysis explored associations between demographic risk factors (including breed, chondrodystrophy, age, sex/neuter status, skull-shape, and body mass) and osteosarcoma of all anatomical sites.

Results

We identified several breeds with increased and reduced odds of osteosarcoma. At highest risk were the Rottweiler and Great Dane, with > 10 times the odds of osteosarcoma compared with crossbreds, and the Rhodesian Ridgeback, which has not featured in previous lists of at-risk breeds for osteosarcoma, and had an odds ratio of 11.31 (95% confidence interval 7.37–17.35). Breeds at lowest risk of osteosarcoma (protected breeds) included the Bichon Frise, the French Bulldog and the Cavalier King Charles Spaniel, all with odd ratios of less than 0.30 compared with crossbreds. Body mass was strongly associated with osteosarcoma risk; dogs over 40 kg exhibited osteosarcoma odds of 45.44 (95% confidence interval 33.74–61.20) compared with dogs less than 10 kg. Chondrodystrophic breeds had an osteosarcoma odds ratio of 0.13 (95% confidence interval 0.11–0.16) compared with non-chondrodystrophic breeds.

Conclusions

This study provides evidence of strong breed-associated osteosarcoma risk and protection, suggesting a genetic basis for osteosarcoma pathogenesis. It highlights that breeds selected for long legs/large body mass are generally overrepresented amongst at-risk breeds, whilst those selected for short leg length/small body mass are generally protected. These findings could inform genetic studies to identify osteosarcoma risk alleles in canines and humans; as well as increasing awareness amongst veterinarians and owners, resulting in improved breeding practices and clinical management of osteosarcoma in dogs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40575-021-00100-7.

Association of GRP78, HIF-1α and BAG3 Expression with the Severity of Chronic Lymphocytic Leukemia

INTRODUCTION

Parallel with the progression of Chronic Lymphocytic Leukemia (CLL), the levels of 78KDa Glucose-Regulated Protein (GRP78) and Hypoxia-Inducible Factor 1 alpha (HIF-1α) are increased as they may activate the induction of anti-apoptotic proteins such as BCL2 Associated Athanogene 3 (BAG3). Previous studies have indicated that there is a positive correlation among GRP78, HIF-1α and BAG3.

OBJECTIVE

This study aimed to evaluate the effect of metabolic factors involved in invasive CLL on apoptotic factors.

METHODS

A case-control study was conducted on 77 patients diagnosed with CLL along with 100 healthy individuals. Cell blood count was performed for all participants. According to Binet's classification, CLL patients were divided into different groups. B cells were isolated from the peripheral blood of CLL patients by binding to anti-CD19 beads. The expression of BAG3, GRP78 and HIF-1α genes was analyzed using the RT-PCR method. To confirm the results of RT-PCR, western blot analysis was carried out.

RESULTS

The results showed that there was a strong association among the expression of BAG3, GRP78 and HIF-1α. The stage of CLL in patients was highly correlated with the expression rate of each gene (p<0.001). Accordingly, the western blot analysis indicated that the concentrations of GRP78 and HIF-1α were significantly higher than the expression of BAG3, considering the stage of CLL.

CONCLUSION

It was shown that increased expression of GRP78 and HIF-1α could result in the elevation of BAG3, as well as the disease progression. Therefore, the role of these metabolic factors might be more pronounced compared with the anti-apoptotic agents to monitor disease progression in CLL patients.

Effect of timing of bisphosphonate administration on canine osteosarcoma cells undergoing radiation therapy

The effects of radiation therapy may be potentiated by combining radiation therapy with secondary therapies. Clinically, radiation therapy has been combined with bisphosphonates for treatment of canine appendicular osteosarcoma for years. The objective of this study was to determine if the timing of administration of bisphosphonates in relation to radiation therapy alters clonogenic survival or cell viability of canine osteosarcoma cells in vitro. Canine osteosarcoma cells were treated before administration of radiation, concurrent with radiation, or after radiation. Reduction in clonogenic survival was identified when bisphosphonates were administered post-radiation compared with pre-radiation. No significant differences were identified for cell viability at any time points. Further investigation of the cellular effects of bisphosphonates on canine osteosarcoma cells is warranted. Consideration may be given to administering bisphosphonates 24 h after radiation to reduce replication of canine osteosarcoma cells and possibly prolong the analgesic effects of both treatments.

Preliminary Virtual Screening Studies to Identify GRP78 Inhibitors Which May Interfere with SARS-CoV-2 Infection

SARS-CoV-2 Spike protein was predicted by molecular docking to bind the host cell surface GRP78, which was suggested as a putative good molecular target to inhibit Covid-19. We aimed to confirm that GRP78 gene expression was increased in blood of SARS-CoV-2 (+) versus SARS-CoV-2 (-) pneumonia patients. In addition, we aimed to identify drugs that could be repurposed to inhibit GRP78, thus with potential anti-SARS-CoV-2 activity. Gene expression studies were performed in 10 SARS-CoV-2 (-) and 24 SARS-CoV-2 (+) pneumonia patients. A structure-based virtual screen was performed with 10,761 small molecules retrieved from DrugBank, using the GRP78 nucleotide binding domain and substrate binding domain as molecular targets. Results indicated that GRP78 mRNA levels were approximately four times higher in the blood of SARS-CoV-2 (+) versus SARS-CoV-2 (-) pneumonia patients, further suggesting that GRP78 might be a good molecular target to treat Covid-19. In addition, a total of 409 compounds were identified with potential as GRP78 inhibitors. In conclusion, we found preliminary evidence that further proposes GRP78 as a possible molecular target to treat Covid-19 and that many clinically approved drugs bind GRP78 as an off-target effect. We suggest that further work should be urgently carried out to confirm if GRP78 is indeed a good molecular target and if some of those drugs have potential to be repurposed for SARS-CoV-2 antiviral activity.

Understanding and Modeling Metastasis Biology to Improve Therapeutic Strategies for Combating Osteosarcoma Progression

Osteosarcoma is a malignant primary tumor of bone, arising from transformed progenitor cells with osteoblastic differentiation and osteoid production. While categorized as a rare tumor, most patients diagnosed with osteosarcoma are adolescents in their second decade of life and underscores the potential for life changing consequences in this vulnerable population. In the setting of localized disease, conventional treatment for osteosarcoma affords a cure rate approaching 70%; however, survival for patients suffering from metastatic disease remain disappointing with only 20% of individuals being alive past 5 years post-diagnosis. In patients with incurable disease, pulmonary metastases remain the leading cause for osteosarcoma-associated mortality; yet identifying new strategies for combating metastatic progression remains at a scientific and clinical impasse, with no significant advancements for the past four decades. While there is resonating clinical urgency for newer and more effective treatment options for managing osteosarcoma metastases, the discovery of druggable targets and development of innovative therapies for inhibiting metastatic progression will require a deeper and more detailed understanding of osteosarcoma metastasis biology. Toward the goal of illuminating the processes involved in cancer metastasis, a convergent science approach inclusive of diverse disciplines spanning the biology and physical science domains can offer novel and synergistic perspectives, inventive, and sophisticated model systems, and disruptive experimental approaches that can accelerate the discovery and characterization of key processes operative during metastatic progression. Through the lens of trans-disciplinary research, the field of comparative oncology is uniquely positioned to advance new discoveries in metastasis biology toward impactful clinical translation through the inclusion of pet dogs diagnosed with metastatic osteosarcoma. Given the spontaneous course of osteosarcoma development in the context of real-time tumor microenvironmental cues and immune mechanisms, pet dogs are distinctively valuable in translational modeling given their faithful recapitulation of metastatic disease progression as occurs in humans. Pet dogs can be leveraged for the exploration of novel therapies that exploit tumor cell vulnerabilities, perturb local microenvironmental cues, and amplify immunologic recognition. In this capacity, pet dogs can serve as valuable corroborative models for realizing the science and best clinical practices necessary for understanding and combating osteosarcoma metastases.

The Major Heat Shock Proteins, Hsp70 and Hsp90, in 2-Methoxyestradiol-Mediated Osteosarcoma Cell Death Model

2-Methoxyestradiol is one of the natural 17β-estradiol derivatives and a potential novel anticancer agent currently being under evaluation in advanced phases of clinical trials. However, the mechanism of anticancer action of 2-methoxyestradiol has not been yet fully established. In our previous studies we have demonstrated that 2-methoxyestradiol selectively induces the expression and nuclear translocation of neuronal nitric oxide synthase in osteosarcoma 143B cells. Heat shock proteins (Hsps) are factors involved in the regulation of expression and activity of nitric oxide synthases. Herein, we chose osteosarcoma cell lines differed in metastatic potential, metastatic 143B and highly metastatic MG63.2 cells, in order to further investigate the anticancer mechanism of 2-methoxyestradiol. The current study aimed to determine the role of major heat shock proteins, Hsp90 and Hsp70 in 2-methoxyestradiol-induced osteosarcoma cell death. We focused on the implication of Hsp90 and Hsp70 in control under expression of neuronal nitric oxide synthase, localization of the enzyme, and further generation of nitro-oxidative stress. To give the insight into the role of Hsp90 in regulation of anticancer efficacy of 2-methoxyestradiol, we used geldanamycin as a potent Hsp90 inhibitor. Herein, we evidenced that inhibition of Hsp90 controls the protein expression of 2-methoxyestradiol-induced neuronal nitric oxide synthase and inhibits enzyme nuclear translocation. We propose that decreased level of neuronal nitric oxide synthase protein after a combined treatment with 2-methoxyestradiol and geldanamycin is directly associated with the accompanying upregulation of Hsp70 and downregulation of Hsp90. This interaction resulted in abrogation of anticancer efficacy of 2-methoxyestradiol by geldanamycin.

Functional redundancy of HSPA1, HSPA2 and other HSPA proteins in non-small cell lung carcinoma (NSCLC); an implication for NSCLC treatment

Heat shock proteins (HSPs) are a large group of chaperones considered critical for maintaining cellular proteostasis. Their aberrant expression in tumors can modulate the course of processes defined as hallmarks of cancer. Previously, we showed that both stress-inducible HSPA1 and testis-enriched HSPA2, highly homologous members of the HSPA (HSP70) family, are often overexpressed in non-small cell lung carcinoma (NSCLC). HSPA1 is among the best characterized cancer-related chaperones, while the significance of HSPA2 for cancer remains poorly understood. Previously we found that in primary NSCLC, HSPA1 was associated with good prognosis while HSPA2 correlated with bad prognosis, suggesting possible different roles of these proteins in cancer. Therefore, in this work we investigated the impact of HSPA1 and HSPA2 on NSCLC cell phenotype. We found that neither paralog-selective nor simultaneous knockdown of HSPA1 and HSPA2 gene expression reduced growth and chemoresistance of NSCLC cells. Only blocking of HSPA proteins using pan-HSPA inhibitors, VER-155008 or JG-98, exerted potent anticancer effect on NSCLC cells, albeit the final outcome was cell type-dependent. Pan-HSPA inhibition sensitized NSCLC cells to bortezomib, but not to platinum derivates. Our result suggests the inhibitors of proteasome and HSPAs seem an effective drug combination for pre-clinical development in highly aggressive NSCLC.

7Hsp70 serum levels in pet dogs-a potential diagnostic biomarker for spontaneous round cell tumors

The concentration of circulating heat shock protein 70 (Hsp70) was measured in liquid biopsies of canine tumor patients as a potential biomarker. Compared with rodent tumor models, spontaneously occurring tumors in pet dogs reflect the clinical situation of human patients better, as dogs cohabitate with their owners in the same environment, reach a much older age than rodents, can provide blood samples much more frequently, and receive up-to-date medical care and, similar to humans, their tumors show a high genetic heterogeneity. Due to the species-specific sequence homology of human and canine Hsp70, two human enzyme-linked immunosorbent assay (ELISA) systems (R&D and lipHsp70) were used to measure canine Hsp70 concentrations in serum and plasma. In general, higher Hsp70 concentrations were found in serum compared with plasma samples of dogs, and the lipHsp70 ELISA detected higher peak concentrations of Hsp70 in a broader range than the R&D ELISA. Compared with a tumor-free control group, serum Hsp70 concentrations were higher in tumor-bearing dogs, irrespective of breed, age, body weight, and gender. A sub-classification of the different tumors according to their cytological characteristics revealed significantly elevated Hsp70 serum concentrations in dogs with round cell tumors (p < 0.01), a heterogeneous group of malignancies with hematopoietic origin such as mast cells, plasma cells, lymphocytes, histiocytes, and melanomas. Future studies with larger patient cohorts and well-defined tumor sizes are necessary to elucidate the role of serum Hsp70 as a biomarker for tumor detection and monitoring of outcome in pet animals.

Cell line-specific efficacy of thermoradiotherapy in human and canine cancer cells in vitro

Objective

Aims were to investigate sensitivity of various human and canine cancer cell lines to hyperthermia and the influence of particular treatment conditions, and to analyze the DNA-damage response and mode of cell death in cell line radiosensitized by hyperthermia. Additionally, we were interested in the involvement of HSP70 in radiosensitization.

Methods

Radiosensitization by hyperthermia was determined in a panel of human and canine cancer cell lines using clonogenic cell survival assay, as well as levels of heat shock proteins (HSPs) using immunoblotting. The influence of the hyperthermia-radiotherapy time gap, different temperatures and the order of treatments on clonogenicity of hyperthermia-sensitive A549 cells was investigated. Additionally, DNA damage and cell death were assessed by Comet assay and an apoptosis/necrosis assay. Further we induced transient knockdown in A549 cells to test HSP70’s involvement in radiosensitization.

Results

Out of eight cell lines tested, only two (A549 and Abrams) showed significant decrease in clonogenic cell survival when pre-treated with hyperthermia at 42°C. Strong induction of HSP70 upon thermoradiotherapy (HT-RT) treatment was found in all cell lines. Transient knockdown of HSP70 in A549 cells did not result in decrease of clonogenic cell survival in response to HT-RT.

Conclusion

Tumor cell-type, temperature and order of treatment play an important role in radiosensitization by hyperthermia. However, hyperthermia has limited potency to radiosensitize canine cancer cells grown in a 2D cell culture setting presented here. DNA damage and apoptosis/necrosis did not increase upon combined treatment and cytosolic levels of HSP70 appear not to play critical role in the radiosensitization of A549 cells.

Pharmacological effectors of GRP78 chaperone in cancers

The protein chaperone GRP78 is a master regulator of endoplasmic reticulum (ER) functions and is frequently over-expressed at the surface of cancer cells where it contributes to chemo-resistance. It represents a well-studied ER stress marker but an under-explored target for new drug development. This review aims to untangle the structural and functional diversity of GRP78 modulators, covering over 130 natural products, synthetic molecules, specific peptides and monoclonal antibodies that target GRP78. Several approaches to promote or to incapacitate GRP78 are presented, including the use of oligonucleotides and specific cell-delivery peptides often conjugated to cytotoxic payloads to design GRP78-targeted therapeutics. A repertoire of drugs that turn on/off GRP78 is exposed, including molecules which bind directly to GRP78, principally to its ATP site. There exist many options to regulate positively or negatively the expression of the chaperone, or to interfere with its cellular trafficking. This review provides a molecular cartography of GRP78 pharmacological effectors and adds weight to the notion that GRP78 repressors could represent promising anticancer therapeutics, notably as regards limiting chemo-resistance of cancer cells. The potential of GRP78-targeting drugs in other therapeutic modalities is also evoked.

VER-155008 induced Hsp70 proteins expression in fish cell cultures while impeding replication of two RNA viruses

The heat-shock protein 70 (Hsp70) inhibitor, VER-155008 (VER), was explored as a potential antiviral agent for two RNA viruses important to fish aquaculture, viral hemorrhagic septicemia virus (VHSV) and infectious pancreatic necrosis virus (IPNV). Studies were done at a temperature of 14 °C, and with cell lines commonly used to propagate these viruses. These were respectively EPC from fathead minnow for VHSV and CHSE-214 from Chinook salmon embryo for IPNV. Additionally, both viruses were studied with the Atlantic salmon heart endothelial cell line ASHe. For both VHSV and IPNV, 25 μM VER impeded replication. This was evidenced by delays in the development of cytopathic effect (CPE) and the expression of viral proteins, N for VHSV and VP2 for IPNV, and by less production of viral RNA and of viral titre. As VER inhibits the activity of Hsp70 family members, these results suggest that VHSV and IPNV utilize one or more Hsp70s in their life cycles. Yet neither virus induced Hsp70. Surprisingly VER alone induced Hsp70, but whether this induction modulated VER's antiviral effects is unknown. Exploring this apparent paradox in the future should improve the usefulness of VER as an antiviral agent.

Evaluation of effects of radiation therapy combined with either pamidronate or zoledronate on canine osteosarcoma cells

Canine osteosarcoma is a devastating disease with an overall poor prognosis. Radiation therapy and bisphosphonates are currently used in combination for palliative treatment, despite a paucity of literature that investigates their combined use. The objectives of this study were to assess the in vitro effects of radiation therapy and bisphosphonates on canine osteosarcoma cells when used in combination. Canine osteosarcoma cell lines D17 and Dharma were treated with radiation and pamidronate or zoledronate, both alone and in combination. The effects of these treatments were assessed using clonogenic survival and cell viability assays. Dose-dependent decreases in clonogenic survival and cell viability were observed for both radiation and bisphosphonate treatment. Combination index analysis revealed antagonistic interactions when radiation and bisphosphonates were used in combination at specific doses for both D17 and Dharma osteosarcoma cells. Further investigation of the combined effects of radiation and bisphosphonates for the palliative treatment of canine osteosarcoma is warranted.

HSP70 Inhibitor Suppresses IGF-I-Stimulated Migration of Osteoblasts through p44/p42 MAP Kinase

Heat shock protein 70 (HSP70) is a ubiquitously expressed molecular chaperone in a variety of cells including osteoblasts. We previously showed that insulin-like growth factor-I (IGF-I) elicits migration of osteoblast-like MC3T3-E1 cells through the activation of phosphatidylinositol 3-kinase/Akt and p44/p42 mitogen-activated protein (MAP) kinase. In the present study, we investigated the effects of HSP70 inhibitors on the IGF-I-elicited migration of these cells and the mechanism involved. The IGF-I-stimulated osteoblast migration evaluated by a wound-healing assay and by a transwell cell migration was significantly reduced by VER-155008 and YM-08, which are both HSP70 inhibitors. VER-155008 markedly suppressed the IGF-I-induced phosphorylation of p44/p42 MAP kinase without affecting that of Akt. In conclusion, our results strongly suggest that the HSP70 inhibitor reduces the IGF-I-elicited migration of osteoblasts via the p44/p42 MAP kinase.

Hsp70: A Cancer Target Inside and Outside the Cell

Heat shock protein 70 (Hsp70) is the most ubiquitous stress-inducible chaperone. It accumulates in the cells in response to a wide variety of physiological and environmental insults including anticancer chemotherapy, thus allowing the cell to survive to lethal conditions. Intracellular Hsp70 is viewed as a cytoprotective protein. Indeed, this protein can inhibit key effectors of the apoptotic and autophagy machineries. In cancer cells, the expression of Hsp70 is abnormally high, and Hsp70 may participate in oncogenesis and in resistance to chemotherapy. In rodent models, Hsp70 overexpression increases tumor growth and metastatic potential. Depletion or inhibition of Hsp70 frequently reduces the size of the tumors and can even cause their complete involution. However, HSP70 is also found in the extra-cellular space where it may signal via membrane receptors or endosomes to alter gene transcription and cellular function. Overall, Hsp70 extracellular function is believed to be immnunogenic and the term chaperokine to define the extracellular chaperones such as Hsp70 has been advanced. In this chapter the knowledge to date, as well as some emerging paradigms about the intra- and extra-cellular functions of Hsp70, are presented. The strategies targeting Hsp70 that are being developed in cancer therapy will also be discussed.

Heat shock protein 70 and tumor-infiltrating NK cells as prognostic indicators for patients with squamous cell carcinoma of the head and neck after radiochemotherapy: A multicentre retrospective study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG)

Tumor cells frequently overexpress heat shock protein 70 (Hsp70) and present it on their cell surface, where it can be recognized by pre-activated NK cells. In our retrospective study the expression of Hsp70 was determined in relation to tumor-infiltrating CD56⁺ NK cells in formalin-fixed paraffin embedded (FFPE) tumor specimens of patients with SCCHN (N = 145) as potential indicators for survival and disease recurrence. All patients received radical surgery and postoperative cisplatin-based radiochemotherapy (RCT). In general, Hsp70 expression was stronger, but with variable intensities, in tumor compared to normal tissues. Patients with high Hsp70 expressing tumors (scores 3-4) showed significantly decreased overall survival (OS; p = 0.008), local progression-free survival (LPFS; p = 0.034) and distant metastases-free survival (DMFS; p = 0.044), compared to those with low Hsp70 expression (scores 0-2), which remained significant after adjustment for relevant prognostic variables. The adverse prognostic value of a high Hsp70 expression for OS was also observed in patient cohorts with p16- (p = 0.001), p53- (p = 0.0003) and HPV16 DNA-negative (p = 0.001) tumors. The absence or low numbers of tumor-infiltrating CD56⁺ NK cells also correlated with significantly decreased OS (p = 0.0001), LPFS (p = 0.0009) and DMFS (p = 0.0001). A high Hsp70 expression and low numbers of tumor-infiltrating NK cells have the highest negative predictive value (p = 0.00004). In summary, a strong Hsp70 expression and low numbers of tumor-infiltrating NK cells correlate with unfavorable outcome following surgery and RCT in patients with SCCHN, and thus serve as negative prognostic markers.

Suppression of heat shock protein 70 by siRNA enhances the antitumor effects of cisplatin in cultured human osteosarcoma cells

Although advances in chemotherapy have improved the prognosis for osteosarcoma, some patients do not respond sufficiently to treatment. Heat shock protein 70 (Hsp70) is expressed at high levels in cancer cells and attenuates the therapeutic efficacy of anticancer agents, resulting in a poorer prognosis. This study investigated whether small interfering RNA (siRNA)-mediated inhibition of Hsp70 expression in an osteosarcoma cell line would enhance sensitivity to cisplatin. The expression of Hsp70 with cisplatin treatment was observed by using Western blotting and real-time reverse transcription polymerase chain reaction (RT-PCR). Changes in the IC50 of cisplatin when Hsp70 was inhibited by siRNA were evaluated. Cisplatin's effectiveness in inducing apoptosis was assessed by assay of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), caspase-3 activity, and mitochondrial membrane potential. Up-regulation of Hsp70 expression was dependent on the concentration of cisplatin. Inhibition of Hsp70 expression significantly reduced the IC50 of cisplatin. When cisplatin was added to osteosarcoma cells with Hsp70 expression inhibited, a significant increase in apoptosis was demonstrated in TUNEL, caspase-3, and mitochondrial membrane potential assays. Inhibition of Hsp70 expression induced apoptosis in cultured osteosarcoma cells, indicating that Hsp70 inhibition enhanced sensitivity to cisplatin. Inhibition of Hsp70 expression may provide a new adjuvant therapy for osteosarcoma.