Differential sensitivity of leukemic and normal hematopoietic progenitors to the killing effect of hyperthermia and quercetin used in combination: role of heat-shock protein-70

Exhaustion of Protective Heat Shock Response Induces Significant Tumor Damage by Apoptosis after Modulated Electro-Hyperthermia Treatment of Triple Negative Breast Cancer Isografts in Mice

Simple Summary

Breast cancer is one of the most frequent cancer types among women worldwide. Triple-negative breast cancer is a highly aggressive breast cancer type with very poor survival due to the lack of targeted therapy. Modulated electro-hyperthermia (mEHT) is a newly emerging form of adjuvant, electromagnetic cancer-treatment. Capacitive energy delivery and frequency modulation enable the application of non-thermal effects. Furthermore, selective energy absorption by the tumor (as demonstrated in our present paper) enables 2.5 °C selective heating of the tumor. In the present study, we demonstrate in an in vivo syngeneic Balb/c TNBC mouse model that mEHT caused a remarkable reduction in the number of viable tumor cells accompanied by significant cleaved caspase-3-related apoptotic tumor tissue destruction and a transitional heat shock response. Furthermore, we demonstrated in vitro that the tumor cell killing effect of mEHT was amplified by inhibitors of the protective heat shock response such as Quercetin and KRIBB11.

Abstract

Modulated electro-hyperthermia (mEHT) is a complementary antitumor therapy applying capacitive radiofrequency at 13.56 MHz. Here we tested the efficiency of mEHT treatment in a BALB/c mouse isograft model using the firefly luciferase-transfected triple-negative breast cancer cell line, 4T1. Tumors inoculated orthotopically were treated twice using a novel ergonomic pole electrode and an improved mEHT device (LabEHY 200) at 0.7 ± 0.3 W for 30 min. Tumors were treated one, two, or three times every 48 h. Tumor growth was followed by IVIS, caliper, and ultrasound. Tumor destruction histology and molecular changes using immunohistochemistry and RT-qPCR were also revealed. In vivo, mEHT treatment transitionally elevated Hsp70 expression in surviving cells indicating heat shock-related cell stress, while IVIS fluorescence showed a significant reduction of viable tumor cell numbers. Treated tumor centers displayed significant microscopic tumor damage with prominent signs of apoptosis, and major upregulation of cleaved/activated caspase-3-positive tumor cells. Serial sampling demonstrated substantial elevation of heat shock (Hsp70) response twelve hours after the treatment which was exhausted by twenty-four hours after treatment. Heat shock inhibitors Quercetin or KRIBB11 could synergistically amplify mEHT-induced tumor apoptosis in vitro. In conclusion, modulated electro-hyperthermia exerted a protective heat shock response as a clear sign of tumor cell stress. Exhaustion of the HSR manifested in caspase-dependent apoptotic tumor cell death and tissue damage of triple-negative breast cancer after mEHT monotherapy. Inhibiting the HSR synergistically increased the effect of mEHT. This finding has great translational potential.

Quercetin Enhances Chemosensitivity to Gemcitabine in Lung Cancer Cells by Inhibiting Heat Shock Protein 70 Expression

Quercetin is a bioflavonoid known for antioxidation and antiproliferation activities. We demonstrated that quercetin inhibited cancer cell growth and sensitized cancer cells to gemcitabine treatment by promoting apoptosis via inhibiting heat shock protein 70 expression. Our results suggest that quercetin might have potential to increase sensitivity to chemotherapy and that heat shock protein 70 could be a new target for lung cancer treatment.

BACKGROUND

Quercetin is a bioflavonoid with antiproliferative and proapoptotic activity in various cancer cells. However, little is known about the mechanism by which quercetin inhibits cancer growth or its potential role as a chemosensitizer in lung cancer cells. We investigated whether quercetin-induced inhibition of heat shock protein 70 (HSP70) is involved in its anticancer activity and whether it could modulate the responsiveness of lung cancer cells to chemotherapy.

MATERIALS AND METHODS

Various concentrations of quercetin and gemcitabine, either alone or in combination, were applied to lung cancer cells (A549 and H460 cells). We evaluated cell viability with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide salt assay, apoptotic activity by determining caspase-3 and caspase-9 activities, and HSP70 expression using Western blot analysis after treatment.

RESULTS

Quercetin reduced cell viability and suppressed HSP70 expression in both cell lines dose-dependently. Adding a fixed quercetin dose enhanced gemcitabine-induced cell death, which was related to increased caspase-3 and caspase-9 activities. Combination treatment with quercetin and gemcitabine downregulated HSP70 expression more prominently than treatment with quercetin or gemcitabine alone.

CONCLUSION

Quercetin-induced HSP70 inhibition was involved in growth inhibition and sensitization to chemotreatment in lung cancer cells. Quercetin might have potential as a chemosensitizer in lung cancer treatment.

Effect of flavonoids and hyperthermal intraperitoneal chemotherapy on tumour growth and micronucleus induction in mouse tumour model

Hyperthermia enhanced the clastogenicity of alkylating agents. We investigated whether quercetin (QU; 3,3',4',5,7-pentahydroxy flavone) or naringenin (NAR) can sensitize Ehrlich ascites tumour (EAT) to cisplatin (CP) hyperthermal intraperitoneal chemotherapy treatment and whether these flavonoids in combination with CP can ameliorate CP-induced micronuclei (MNs) in peripheral blood reticulocytes of mice. QU or NAR were administered to mice 7 and 3 days before implantation of EAT cells, while CP (5 or 10 mg kg-1) was injected intraperitoneally to normothermic or hyperthermic-treated mice 3 days after implantation of EAT cells (2 106). Our study supports the claim that the QU or NAR in combined treatment with CP has the potential to inhibit tumour growth in both normothermic and hyperthermic conditions and attenuate number of MNs in the peripheral blood reticulocytes of mice at normothermic condition but enhanced the clastogenicity of CP agents in hyperthermal condition.

Inducible hsp70 in the regulation of cancer cell survival: analysis of chaperone induction, expression and activity

Understanding the mechanisms that control stress is central to realize how cells respond to environmental and physiological insults. All the more important is to reveal how tumour cells withstand their harsher growth conditions and cope with drug-induced apoptosis, since resistance to chemotherapy is the foremost complication when curing cancer. Intensive research on tumour biology over the past number of years has provided significant insights into the molecular events that occur during oncogenesis, and resistance to anti-cancer drugs has been shown to often rely on stress response and expression of inducible heat shock proteins (HSPs). However, with respect to the mechanisms guarding cancer cells against proteotoxic stresses and the modulatory effects that allow their survival, much remains to be defined. Heat shock proteins are molecules responsible for folding newly synthesized polypeptides under physiological conditions and misfolded proteins under stress, but their role in maintaining the transformed phenotype often goes beyond their conventional chaperone activity. Expression of inducible HSPs is known to correlate with limited sensitivity to apoptosis induced by diverse cytotoxic agents and dismal prognosis of several tumour types, however whether cancer cells survive because of the constitutive expression of heat shock proteins or the ability to induce them when adapting to the hostile microenvironment remains to be elucidated. Clear is that tumours appear nowadays more "addicted" to heat shock proteins than previously envisaged, and targeting HSPs represents a powerful approach and a future challenge for sensitizing tumours to therapy. This review will focus on the anti-apoptotic role of heat shock 70kDa protein (Hsp70), and how regulatory factors that control inducible Hsp70 synthesis, expression and activity may be relevant for response to stress and survival of cancer cells.

KNK437, a benzylidene lactam compound, sensitises prostate cancer cells to the apoptotic effect of hyperthermia

Hyperthermia is known to serve as a powerful tool in the treatment of prostate cancer which is commonly diagnosed in men. Quercetin and KNK437, Hsp70 inhibitors, play an important role in blocking thermotolerance in some cancer cells. In the present study we investigated the effects of KNK437 and quercetin on the acquisition of thermotolerance and heat-induced apoptosis. Also, it was examined whether the possible mechanism triggering apoptotic pathway included caspase-3 activation in prostate cancer cells. For this purpose, PC-3 and LNCaP cells were treated with hyperthermia following pretreatment with or without KNK437 or quercetin. Thermotolerance was investigated by colony formation assay in these cells, while Hsp70 mRNA levels were measured by real time RT-PCR. Sandwich ELISA was used for detection of Hsp70 protein levels. Apoptosis was detected by flow cytometric annexin V binding assay and by western blot analysis of procaspase-3 and cleaved poly (ADP-ribose) polymerase levels. In our study, KNK437 and quercetin inhibited thermotolerance in a dose-dependent manner in PC-3 cells. KNK437 and quercetin decreased heat-induced accumulation of Hsp70 mRNA and protein in PC-3 and LNCaP cells. KNK437 and quercetin pretreatment enhanced the apoptotic effect of hyperthermia in both cells. We found that KNK437 was more effective than quercetin in inducing apoptotic cell death, activation of caspase-3, and cleavage of PARP in prostate cancer cells. We suggest that KNK437 is a useful agent for enhancing the efficiency of hyperthermic therapy which has less toxic side-effects in prostate cancer.

Cytotoxic effect of flavonoids on leukemia cells and normal cells of human blood

We compared the cytotoxic effect of 11 flavonoids on chronic myeloid leukemia (erythroblast crisis) K562 cells and peripheral blood mononuclear cells from healthy donors. Baicalein and myricetin had a specific cytotoxic effect on leukemia cells.

Heat shock proteins and Bcl-2 expression and function in relation to the differential hyperthermic sensitivity between leukemic and normal hematopoietic cells

A major problem in autologous stem cell transplantation is the occurrence of relapse by residual neoplastic cells from the graft. The selective toxicity of hyperthermia toward malignant hematopoietic progenitors compared with normal bone marrow cells has been utilized in purging protocols. The underlying mechanism for this selective toxicity has remained unclear. By using normal and leukemic cell line models, we searched for molecular mechanisms underlying this selective toxicity. We found that the differential heat sensitivity could not be explained by differences in the expression or inducibility of Hsp and also not by the overall chaperone capacity of the cells. Despite an apparent similarity in initial heat-induced damage, the leukemic cells underwent heat-induced apoptosis more readily than normal hematopoietic cells. The differences in apoptosis initiation were found at or upstream of cytochrome c release from the mitochondria. Sensitivity to staurosporine-induced apoptosis was similar in all cell lines tested, indicating that the apoptotic pathways were equally functional. The higher sensitivity to heat-induced apoptosis correlated with the level of Bcl-2 protein expression. Moreover, stable overexpression of Bcl-2 protected the most heat sensitive leukemic cells against heat-induced apoptosis. Our data indicate that leukemic cells have a specifically lower threshold for heat damage to initiate and execute apoptosis, which is due to an imbalance in the expression of the Bcl-2 family proteins in favor of the proapoptotic family members.

Heat shock protein 70 increases tumorigenicity and inhibits apoptosis in pancreatic adenocarcinoma

Pancreatic carcinoma is a malignant disease that responds poorly to chemotherapy because of its resistance to apoptosis. Heat shock proteins (Hsp) are not only cytoprotective but also interfere with the apoptotic cascade. Here, we investigated the role of Hsp70 in regulating apoptosis in pancreatic cancer cells. Hsp70 expression was increased in pancreatic cancer cells compared with normal pancreatic ductal cells. This was confirmed by increased mRNA levels for Hsp70 in human pancreatic cancer tissue compared with neighboring normal tissue from the same patient. Depletion of Hsp70 by quercetin decreased cell viability and induced apoptosis in cancer cells but not in normal pancreatic ductal cells. To show that this is a specific effect of Hsp70 on apoptosis, levels of Hsp70 were knocked down by short interfering RNA treatment, which also induced apoptosis in cancer cells as indicated by Annexin V staining and caspase activation. Daily administration of quercetin to nude mice decreased tumor size as well as Hsp70 levels in tumor tissue. These findings indicate that Hsp70 plays an important role in apoptosis and that selective Hsp70 knockdown can be used to induce apoptosis in pancreatic cancer cells.

Heat shock proteins: new keys to the development of cytoprotective therapies

All cells, from bacterial to human, have a common, intricate response to stress that protects them from injury. Heat shock proteins (Hsps), also known as stress proteins and molecular chaperones, play a central role in protecting cellular homeostatic processes from environmental and physiologic insult by preserving the structure of normal proteins and repairing or removing damaged ones. An understanding of the interplay between Hsps and cell stress tolerance will provide new tools for treatment and drug design that maximise preservation or restoration of health. For example, the increased vulnerability of tissues to injury in some conditions, such as ageing, diabetes mellitus and menopause, or with the use of certain drugs,, such as some antihypertensive medications, is associated with an impaired Hsp response. Additionally, diseases that are associated with tissue oxidation, free radical formation, disorders of protein folding, or inflammation, may be improved therapeutically by elevated expression of Hsps. The accumulation of Hsps, whether induced physiologically, pharmacologically, genetically, or by direct administration of the proteins, is known to protect the organism from a great variety of pathological conditions, including myocardial infarction, stroke, sepsis, viral infection, trauma, neurodegenerative diseases, retinal damage, congestive heart failure, arthritis, sunburn, colitis, gastric ulcer, diabetic complications and transplanted organ failure. Conversely, lowering Hsps in cancer tissues can amplify the effectiveness of chemo- or radiotherapy. Treatments and agents that induce Hsps include hyperthermia, heavy metals (zinc and tin), salicylates, dexamethasone, cocaine, nicotine, alcohol, alpha-adrenergic agonists, PPAR-gamma agonists, bimoclomol, geldanamycin, geranylgeranylacetone and cyclopentenone prostanoids. Compounds that suppress Hsps include quercetin (a bioflavinoid), 15-deoxyspergualin (an immunosuppressive agent) and retinoic acid. Researchers who are cognisant of the Hsp-related effects of these and other agents will be able to use them to develop new therapeutic paradigms.

Increased megakaryopoiesis in cultures of CD34-enriched cord blood cells maintained at 39 degrees C

Based on previous evidence suggesting positive effects of fever on in vivo hematopoiesis, we tested the effect of hyperthermia on megakaryopoiesis (MK) in ex vivo cultures of CD34-enriched cord blood (CB) cells. The cells were cultured at 37 degrees C or 39 degrees C for 14 days in cytokine conditions optimized for megakaryocyte development and analyzed periodically. Compared to 37 degrees C, the cultures maintained at 39 degrees C produced significantly more (up to 10-fold) total cells, myeloid and MK progenitors, and total MKs, and showed accelerated and enhanced MK maturation with increased yields of proplatelets and platelets. This observation could facilitate clinical applications requiring ex vivo expansion of hematopoietic cells.

Flavonoid effects on normal and leukemic cells

Quercetin and flavopiridol, both flavonoids which influence oxidative milieu, proliferation, and apoptosis of various cell types, were examined for their effects on acute myelogenous leukemic cells and normal progenitors. Both quercetin and flavopiridol inhibited the growth and viability of various acute myelogenous leukemia (AML) cell lines and AML blasts isolated afresh from patients with AML of various subtypes. The effects on inhibition of proliferation and decreased viability were also significant in normal CD34+ cells isolated from normal marrow donors. In certain AML cases, the effects of flavopiridol appeared to be mediated through activation of caspase 3, offering one possible mechanism for the apoptosis evident after exposure to flavopiridol as measured by annexin V expression. These flavonoid compounds might find use in various therapeutic settings in AML.

Flavonoid quercetin sensitizes a CD95-resistant cell line to apoptosis by activating protein kinase Calpha

We previously demonstrated that quercetin, a naturally occurring flavonoid with strong antioxidant properties, was able to enhance programmed cell death in HPB-acute lymphoblastic leukemia (ALL) cell line, derived from a human tymoma, when associated with the agonistic anti-CD95 monoclonal antibody. Here, we report that HPB-ALL cells are normally resistant to CD95-mediated apoptosis, and quercetin is able to sensitize this cell line through a mechanism independent of its antioxidant properties. In fact, other compounds structurally and functionally similar to quercetin, when associated with anti-CD95 antibody did not induce any CD95-mediated apoptosis, still maintaining their antioxidant capacity. We found that quercetin effects are mediated by the activation of PKCalpha. Treatment of HPB-ALL cells with quercetin slightly decreased PKCalpha activity, but when the flavonoid was associated with anti-CD95, the kinase activity increased by 12-fold with respect to the treatment with quercetin. In addition, overexpression of PKCalpha induced programmed cell death in the absence of any additional stimulus, while a kinase-defective mutant of PKCalpha was ineffective. Our data confirm the involvement of specific PKC isoforms in CD95 signaling and suggest, for the first time, that quercetin targets this pathway increasing apoptogenic response in a cell line resistant to CD95-mediated apoptosis.

Quercetin and tamoxifen sensitize human melanoma cells to hyperthermia

Hyperthermia produces regression of human cancer. Because hyperthermia has produced only limited results, attention has focused on searching for substances able to sensitize tumour cells to the effects of hyperthermia. The flavonoid quercetin has been reported to be a hyperthermic sensitizer in ovarian and uterine cervical tumours and in leukaemia. Quercetin and tamoxifen inhibit melanoma cell growth. We therefore investigated whether quercetin and tamoxifen can sensitize M10, M14 and MNT1 human melanoma cells to hyperthermia. We observed that both quercetin and tamoxifen synergize with hyperthermia (42.5 degrees C) in reducing the clonogenic activity of M14 and MNT1 and in inducing apoptotic cell death in all three cell lines. As revealed by flow cytometric and Northern blot analyses, quercetin and tamoxifen reduced heat shock protein-70 expression at both protein and mRNA levels. Our results suggest that quercetin and tamoxifen can be usefully combined with hyperthermia in the therapy of recurrent and/or metastatic melanoma.

Quercetin inhibits c-fos, heat shock protein, and glial fibrillary acidic protein expression in injured astrocytes

Quercetin, a bioflavonoid, is found widely in many kinds of fruits and vegetables. It is known to engage in many bioactivities, such as interfering with of the progress of stress responses to injury. In the present study, we investigated the effects of quercetin on some injury responses in primary cultures of astrocytes. These injury responses included the elevation of c-fos protein, heat shock protein (HSP70), and glial fibrillary acidic protein (GFAP). After heat shock insult, the levels of c-fos protein and HSP70 in astrocytes increased. With quercetin treatment, these proteins were significantly reduced. The inhibition of these injury responses by quercetin in astrocytes indicated a dose dependency, with the highest effect at 100 microM. We have previously established a scratch injury model in a primary culture of astrocytes. In that model, astrocytes responded to the scratch injury by an elevation in their GFAP level and formation of hypertrophic cell processes, which extend into the scratch areas. Quercetin treatment reduced the number of hypertrophic cell processes being extended into the scratch areas. With 100 microM of quercetin, there was a complete inhibition of the formation of the hypertrophic cell process. Western blot analysis for GFAP indicated that quercetin significantly reduced the induction of GFAP in the scratch model. At 100 microM, the total GFAP content in the injured cultures was reduced to a level lower than that of the control. This implied that quercetin might possess an antigliotic property.

Quercetin and anti-CD95(Fas/Apo1) enhance apoptosis in HPB-ALL cell line

Several malignant cell lines are resistant to CD95-(Apo1/Fas)-mediated apoptosis, even when the CD95 receptor is highly expressed. Sensitivity to CD95-induced apoptosis can be restored using different molecules. In this study, we showed that quercetin, a naturally occurring flavonoid, in association with the agonistic anti-CD95 monoclonal antibody, increases DNA fragmentation and caspase-3 activity in HPB-ALL cells. These cells have been selected for their known resistance to CD95-induced apoptosis. At molecular level, quercetin lowers the level of intracellular reactive oxygen species, reduces mitochondrial transmembrane potential, thereby leaving the expression of CD95 receptor unchanged.

Inhibition of Vpr-induced cell cycle abnormality by quercetin: a novel strategy for searching compounds targeting Vpr

Vpr, an accessory gene product of HIV-1 which induces cell cycle abnormality leading to the increased HIV replication, is supposed to be a possible target for anti-AIDS drugs. We recently established a cell line (MIT-23) in which Vpr-induced cell cycle perturbation could be manipulated by a tetracycline promoter. Here, we screened anti-Vpr activity in 27 kinds of herb drugs using MIT-23 cells. One of the extracts prepared from Houttuyniae herba showed an inhibitory activity. Quercetin (QCT), a compound of this crude drug, efficiently inhibited Vpr function without affecting its expression. Furthermore, data suggested that Vpr-induced transcription from HIV-LTR was considerably abrogated by QCT. These data indicate that QCT, a flavonoid previously reported to inhibit HIV replication, also targets Vpr, implicating that MIT-23 cell provides a novel strategy for screening compounds possessing anti-Vpr activity which would be in turn utilized for clarifying the mechanism of Vpr function.

Effects of quercetin and sunphenon on responses of cancer cells to heat shock damage

Quercetin is a flavonoid well known to inhibit growth and heat shock protein (HSP) synthesis of cancer cells. However, sunphenon has been scarcely reported concerning effects on cancer cells. We compared the effects of sunphenon with those of quercetin on the human cholangio-cellular carcinoma cell line (HuCC-T1). Both flavonoids inhibited HuCC-T1 growth in a concentration-dependent manner without reduction of HSP70 and HSP90 expression before heat shock damage. The heat shock reduced the cell viability of the quercetin-treated HuCC-T1, but not that of the sunphenon-treated cells. This inhibitory effect of quercetin on tolerance to heat shock is thought to be due to marked suppression of HSP72. Sunphenon conversely increased HSP72 expression after heat shock. Although neither flavonoid altered HSP90 protein levels before and after heat shock, quercetin delayed the reorganization of filamentous actin (F-actin) during the recovery period after heat shock. Since HSP90 could preserve F-actin structure during stresses, quercetin might affect the interaction between HSP90 and F-actin without influencing HSP90 expression. In conclusion, quercetin would be more useful than sunphenon in combined therapy with hyperthermia for cancer.