Hyperthermia induces apoptosis through endoplasmic reticulum and reactive oxygen species in human osteosarcoma cells

Hyperthermia enhances photodynamic therapy by regulation of HCP1 and ABCG2 expressions via high level ROS generation

Photodynamic therapy (PDT) is a cancer treatment that make use of the cancer-specific accumulation of porphyrins. We have reported that mitochondrial reactive oxygen species (mitROS) upregulate uptake transporter of porphyrins, heme carrier protein-1 (HCP-1). The accumulation of cancer-specific porphyrins was increased by mitROS production, thereby the cancer-specific PDT cytotoxicity was enhanced. Thus we investigated whether mitROS production by hyperthermia can enhanced the cytotoxicity of PDT or not. In this study, 1 h of hyperthermia at 42 °C increased the mitROS production, and both the accumulation of cancer-specific porphyrins and the PDT cytotoxicity increased. Moreover, the authors treated cells with N-acetyl-L-cysteine (NAC) to examine the effect of mitROS. NAC inhibited the increasing ROS production after hyperthermia to restrain the post-treatment increase of cancer-specific porphyrins accumulation. Moreover, the increase of ROS production in cancer cells after hyperthermia upregulated HCP-1 expression and downregulated ABCG2 expression. These regulation were inhibited by NAC. These results suggest that hyperthermia treatment increased mitROS production, which involved HpD accumulation and enhanced PDT effects in cancer cells. The mechanism of this phenomenon was most likely to be due to both the upregulation of HCP-1 and the downregulation of ABCG2 by mitROS.

Microwave hyperthermia promotes caspase‑3-dependent apoptosis and induces G2/M checkpoint arrest via the ATM pathway in non‑small cell lung cancer cells

Post-operative microwave (MW) hyperthermia has been applied as an important adjuvant therapy to enhance the efficacy of traditional cancer treatment. A better understanding of the molecular mechanisms of MW hyperthermia may provide guided and further information on clinical hyperthermia treatment. In this study, we examined the effects of MW hyperthermia on non-small cell lung carcinoma (NSCLC) cells in vitro, as well as the underlying mechanisms. In order to mimic clinical treatment, we developed special MW heating equipment for this study. Various NSCLC cells (H460, PC-9 and H1975) were exposed to hyperthermia treatment using a water bath or MW heating system. The results revealed that MW hyperthermia significantly inhibited cell growth compared with the water bath heating system. Furthermore, MW hyperthermia increased the production of reactive oxygen species (ROS), decreased the levels of mitochondrial membrane potential (MMP) and induced caspase-3 dependent apoptosis. It also induced G₂/M phase arrest through the upregulation of the expression of phosphorylated (p-) ataxia telangiectasia mutated (ATM), p-checkpoint kinase 2 (Chk2) and p21, and the downregulation of the expression of cdc25c, cyclin B1 and cdc2. On the whole, the findings of this study indicate that the exposure of NSCLC cells to MW hyper-thermia promotes caspase-3 dependent apoptosis and induces G₂/M cell cycle arrest via the ATM pathway. This preclinical study may help to provide laboratory-based evidence for MW hyperthermia treatment in clinical practice.

Seawater inhalation induces acute lung injury via ROS generation and the endoplasmic reticulum stress pathway

Seawater (SW) inhalation can induce acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In the present study, SW induced apoptosis of rat alveolar epithelial cells and histopathological alterations to lung tissue. Furthermore, SW administration increased generation of reactive oxygen species (ROS), whereas pretreatment with the ROS scavenger, N-acetyl-L-cysteine (NAC), significantly decreased ROS generation, apoptosis and histopathological alterations. In addition, SW exposure upregulated the expression levels of glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP), which are critical proteins in the endoplasmic reticulum (ER) stress response, thus indicating that SW may activate ER stress. Conversely, blocking ER stress with 4-phenylbutyric acid (4-PBA) significantly improved SW-induced apoptosis and histopathological alterations, whereas an ER stress inducer, thapsigargin, had the opposite effect. Furthermore, blocking ROS with NAC inhibited SW-induced ER stress, as evidenced by the downregulation of GRP78, phosphorylated (p)-protein kinase R-like ER kinase (PERK), p-inositol-requiring kinase 1α (IRE1α), p-50 activating transcription factor 6α and CHOP. In addition, blocking ER stress with 4-PBA decreased ROS generation. In conclusion, the present study indicated that ROS and ER stress pathways, which are involved in alveolar epithelial cell apoptosis, are important in the pathogenesis of SW-induced ALI.

Oxidative and endoplasmic reticulum stress defense mechanisms of bovine granulosa cells exposed to heat stress

In most mammalian species including cattle, heat stress has detrimental effects on ovarian function through disturbing estradiol production and viability of granulosa cells. However, effect of heat stress and underlying cellular defense mechanisms of bovine granulosa cells is not fully understood. Here, we aimed to investigate the effect of heat stress on granulosa cells function and the associated defense mechanism. For this an in vitro granulosa cell model was used to investigate the role of elevated temperature (41 °C) on granulosa cell functions at 24 h and 48 h exposure compared to the control cultured at 37 °C. The results showed that reactive oxygen species level was higher in cells under 41 °C at 24 h compared to control. In response to increased reactive oxygen species level, the expression of NRF2 and its antioxidant genes, CAT and PRDX1 were higher in bovine granulosa cells exposed to heat stress. Interestingly, heat stress markedly increased expression of endoplasmic reticulum stress marker genes; GRP78 and GRP94, in cultured bovine granulosa cells at 24 h, and higher protein accumulation of GRP78 accompanied by increased expression of apoptotic genes, BAX and CASPASE-3. Moreover, heat stress significantly decreased the bovine granulosa cells proliferation, which was supported by decreased in the expression of proliferation marker gene PCNA. All in all heat stress induce reactive oxygen species accumulation, apoptosis and reduced proliferation, which trigger the NRF2 mediated oxidative stress and endoplasmic reticulum stress response by bovine granulosa cells.

Post-Modified Polypeptides with UCST-Type Behavior for Control of Cell Attachment in Physiological Conditions

Upper Critical Solution Temperature (UCST)-type thermally responsive polypeptides (TRPs) with phase transition temperatures around 37 °C in phosphate-buffered saline (PBS) buffer (pH 7.4, 100 mM) were prepared from poly(l-ornithine) hydrobromide and coated on non-tissue culture-treated plastic plates (nTCP). Cell adhesion was observed at temperatures above the phase transition temperature of the coating polymer (39 °C), while cell release was triggered when the culture temperature was switched to 37 °C. Approximately 65% of the attached cells were released from the surface within 6 h after changing the temperature, and more than 96% of the released cells were viable. Water contact angle measurements performed at 39 and 37 °C demonstrated that the surface hydrophobicity of the new TRP coatings changed in response to applied temperature. The cell attachment varied with the presence of serum in the media, suggesting that the TRP coatings mediated cell attachment and release as the underlying polymer surface changed conformation and consequently the display of adsorbed protein. These new TRP coatings provide an additional means to mediate cell attachment for application in cell-based tissue regeneration and therapies.

Hyperthermia with different temperatures inhibits proliferation and promotes apoptosis through the EGFR/STAT3 pathway in C6 rat glioma cells

Malignant gliomas are a group of aggressive neoplasms among human cancers. The curative effects of current treatments are finite for improving the prognosis of patients. Hyperthermia (HT) is an effective treatment for cancers; however, the effects of HT with different temperatures in treatment of MG and relevant mechanisms remain unclear. MTT assay and Annexin V-fluorescein isothiocyanate/propidium iodide staining were used for investigating the proliferation and apoptosis of C6 cells, respectively. Western blotting was applied to detect the expression of proteins. Ultrasonography was employed to evaluate the tumor formation rate, growth rate, angiogenesis rate and degree of hardness of tumors in vivo. The authors certified that HT with 42–46°C × 1 h, 1 t could inhibit proliferation, promote apoptosis, reduce tumor formation rate, growth rate, angiogenesis rate, degree of hardness of tumors, ischemic tolerance and anoxic tolerance, and have synergy with temozolomide in C6 cells. Long-term HT (43°C × 1 h, 1 t/5 d, 90 d) did not cut down the sensitivity of C6 cells to HT, and sustainably inhibited the proliferation of C6 cells. Furthermore, the authors proved HT produced these effects primarily through inhibition of the EGFR/STAT3/HIF-1A/VEGF-A pathway.

Identification of Key Genes Affecting Results of Hyperthermia in Osteosarcoma Based on Integrative ChIP-Seq/TargetScan Analysis

Background

The purpose of this study was to research the effects of hyperthermia on osteosarcoma (OS) by integrating the Chromatin Immunoprecipitation with the generation sequencing (ChIP-Seq) and TargetScan analysis of heat shock transcription factor 1 (HSF1).

Material/Methods

The HSF1 ChIP-seq dataset of GSE60984 was downloaded from the Gene Expressed Omnibus (GEO) database. The HSF1-binding sites were screened by MACS2 in OS cells after 10 and 20 min of hyperthermia, and they were annotated using the ChIPseeker package. The overlapped genes were selected out when HSF1-binding sites were located in the promoter region. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the overlaps. The miRNA-gene pairs of the overlaps were screened out via TargetScan, and the miRNA-gene-regulated network was constructed by Cytoscape software.

Results

1880 and 1283 genes of promoter regions were obtained in the osteosarcoma cells after 10 and 20 min of hyperthermia, respectively, and 889 of them were overlapped. The overlapped genes were enriched in 122 GO terms and 3 KEGG pathways. There were 13 657 pairs involved in the miRNA-gene regulated network of the overlaps.

Conclusions

Some biomarkers were identified for OS treated with hyperthermia. Moreover, some GO terms (regulation of programmed cell death and regulation of cell death) and pathways (p53 signaling pathway, methane metabolism, and viral myocarditis) might be involved.

Melatonin enhances hyperthermia-induced apoptotic cell death in human leukemia cells

Melatonin is an endogenous indoleamine with a wide range of biological functions. In addition to modulating circadian rhythms, it plays important roles in the health as an antioxidant. Melatonin has also the ability to induce apoptosis in cancer cells and to enhance the antitumoral activity of chemotherapeutic agents. In this study, the effect of melatonin on hyperthermia-induced apoptosis was explored using human leukemia cells. The results demonstrate that melatonin greatly improved the cytotoxicity of hyperthermia in U937 cells. The potentiation of cell death was achieved with 1 mmol/L concentrations of the indoleamine but not with concentrations close to physiological levels in blood (1 nmol/L). This effect was associated to an enhancement of the apoptotic response, revealed by an increase in cells with hypodiploid DNA content and activation of multiple caspases (caspase-2, caspase-3, caspase-8, and caspase-9). Melatonin also increased hyperthermia-induced Bid activation as well as translocation of Bax from the cytosol to mitochondria and cytochrome c release. Hyperthermia-provoked apoptosis and potentiation by melatonin were abrogated by a broad-spectrum caspase inhibitor (z-VAD-fmk) as well as by specific inhibitors against caspase-8 or caspase-3. In contrast, blocking of the mitochondrial pathway of apoptosis either with a caspase-9 inhibitor or overexpressing the anti-apoptotic protein Bcl-2 (U937/Bcl-2) reduced the number of apoptotic cells in response to hyperthermia but it was unable to suppress melatonin enhancement. Melatonin appears to modulate the apoptotic response triggered by hyperthermia in a cell type-specific manner as similar results were observed in HL-60 but not in K562 or MOLT-3 cells.

Enhancement of hyperthermia-induced apoptosis by 5Z-7-oxozeaenol, a TAK1 inhibitor, in A549 cells

KRAS mutant lung cancers have long been considered as untreatable with drugs. Transforming growth factor-β-activated kinase 1 (TAK1) appears to play an anti-apoptotic role in response to multiple stresses and has been reported to be a responsive kinase that regulates cell survival in KRAS-dependent cells. In this study, in order to find a useful approach to treat KRAS mutant lung cancer, we focused on the combined effects of 5Z-7-oxozeaenol, a TAK1 inhibitor, with hyperthermia (HT) in KRAS mutant lung cancer cell line A549. Annexin V-FITC/PI assay, cell cycle analysis, and colony formation assay revealed a significant enhancement in apoptosis induced by HT treatment, when the cells were pre-incubated with 5Z-7-oxozeaenol in a dose-dependent manner. The enhanced apoptosis by 5Z-7-oxozeaenol was accompanied by a significant increase in reactive oxygen species (ROS) generation and loss of mitochondrial membrane potential (MMP). In addition, western blot showed that 5Z-7-oxozeaenol enhanced HT-induced expressions of cleaved caspase-3, cleaved caspase-8, and HSP70 and decreased HT-induced expressions of Bcl-2, p-p38, p-JNK, and LC3. Moreover, 5Z-7-oxozeaenol pre-treatment resulted in a marked elevation of intracellular calcium level which might be associated with endoplasmic reticulum (ER) stress-related pathway. Taken together, our data provides further insights of the mechanism of action of 5Z-7-oxozeaenol and HT treatment, and their potential application as a novel approache to treat patients with KRAS mutant lung cancer.

Hyperthermia: an effective strategy to induce apoptosis in cancer cells

Heat has been used as a medicinal and healing modality throughout human history. The combination of hyperthermia (HT) with radiation and anticancer agents has been used clinically and has shown positive results to a certain extent. However, the clinical results of HT treatment alone have been only partially satisfactory. Cell death following HT treatment is a function of both temperature and treatment duration. HT induces cancer cell death through apoptosis; the degree of apoptosis and the apoptotic pathway vary in different cancer cell types. HT-induced reactive oxygen species production are responsible for apoptosis in various cell types. However, the underlying mechanism of signal transduction and the genes related to this process still need to be elucidated. In this review, we summarize the molecular mechanism of apoptosis induced by HT, enhancement of heat-induced apoptosis, and the genetic network involved in HT-induced apoptosis.

Hyperthermia adds to trabectedin effectiveness and thermal enhancement is associated with BRCA2 degradation and impairment of DNA homologous recombination repair

The tetrahydroisoquinoline trabectedin is a marine compound with approved activity against human soft-tissue sarcoma. It exerts antiproliferative activity mainly by specific binding to the DNA and inducing DNA double-strand breaks (DSB). As homologous recombination repair (HRR)-deficient tumors are more susceptible to trabectedin, hyperthermia-mediated on-demand induction of HRR deficiency represents a novel and promising strategy to boost trabectedin treatment. For the first time, we demonstrate enhancement of trabectedin effectiveness in human sarcoma cell lines by heat and characterize cellular events and molecular mechanisms related to heat-induced effects. Hyperthermic temperatures (41.8 or 43°C) enhanced significantly trabectedin-related clonogenic cell death and G2/M cell cycle arrest followed by cell type-dependent induction of apoptosis or senescence. Heat combination increased accumulation of γH2AX foci as key marker of DSBs. Expression of BRCA2 protein, an integral protein of the HRR machinery, was significantly decreased by heat. Consequently, recruitment of downstream RAD51 to γH2AX-positive repair foci was almost abolished indicating relevant impairment of HRR by heat. Accordingly, enhancement of trabectedin effectiveness was significantly augmented in BRCA2-proficient cells by hyperthermia and alleviated in BRCA2 knockout or siRNA-transfected BRCA2 knockdown cells. In peripheral blood mononuclear cells isolated from sarcoma patients, increased numbers of nuclear γH2AX foci were detected after systemic treatment with trabectedin and hyperthermia of the tumor region. The findings establish BRCA2 degradation by heat as a key factor for a novel treatment strategy that allows targeted chemosensitization to trabectedin and other DNA damaging antitumor drugs by on-demand induction of HRR deficiency.

Drugs acting on homeostasis: challenging cancer cell adaptation

Cancer treatment aims to exploit properties that define malignant cells. In recent years, it has become apparent that malignant cells often survive cancer treatment and ensuing cell stress by switching on auxiliary turnover pathways, changing cellular metabolism and, concomitantly, the gene expression profile. The changed profile impacts the material exchange of cancer cells with affected tissues. Herein, we show that pathways of proteostasis and energy generation regulate common transcription factors. Namely, when one pathway of intracellular turnover is blocked, it triggers alternative turnover mechanisms, which induce transcription factor proteins that control expression of cytokines and regulators of apoptosis, cell division, differentiation, metabolism, and response to hormones. We focus on several alternative turnover mechanisms that can be blocked by drugs already used in clinical practice for the treatment of other non-cancer related diseases. We also discuss paradigms on the challenges posed by cancer cell adaptation mechanisms.

Calcium and ROS: A mutual interplay

Calcium is an important second messenger involved in intra- and extracellular signaling cascades and plays an essential role in cell life and death decisions. The Ca²⁺ signaling network works in many different ways to regulate cellular processes that function over a wide dynamic range due to the action of buffers, pumps and exchangers on the plasma membrane as well as in internal stores. Calcium signaling pathways interact with other cellular signaling systems such as reactive oxygen species (ROS). Although initially considered to be potentially detrimental byproducts of aerobic metabolism, it is now clear that ROS generated in sub-toxic levels by different intracellular systems act as signaling molecules involved in various cellular processes including growth and cell death. Increasing evidence suggests a mutual interplay between calcium and ROS signaling systems which seems to have important implications for fine tuning cellular signaling networks. However, dysfunction in either of the systems might affect the other system thus potentiating harmful effects which might contribute to the pathogenesis of various disorders.

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Calcium and ROS act as signaling molecules inside the cell and their pathways can interact.

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The mutual interplay of calcium and ROS is required for the fine tuning of signaling.

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Failure in the interplay results in dysfunction and pathologies.

Identification of proteins interacting with protein kinase C-δ in hyperthermia-induced apoptosis and thermotolerance of Tca8113 cells

The purpose of the present study was to investigate the differential proteins that interact with protein kinase C‑δ (PKC‑δ) in hyperthermia‑induced apoptosis as well as thermotolerance in Tca8113 cells, and furthermore, to investigate the mechanisms of these processes in tumor cells. Activation of PKC‑δ was previously indicated to be involved in the heat sensitivity and thermal resistance of tongue squamous carcinoma cells. Tca8113 cell apoptosis was induced by incubation at 43˚C for 80 min and the thermotolerant Tca8113 cells (TT‑Tca8113) were generated through a gradient temperature‑elevating method. The apoptotic rate of the cells was determined by flow cytometry, while cleavage and activation of PKC‑δ were analyzed by western blot analysis. The proteins that interacted with PKC‑δ in the Tca8113 and TT‑Tca8113 cells were identified by co‑immunoprecipitation coupled with mass spectrometry. Co‑immunoprecipitation analysis followed by electrospray ionization mass spectrometric analysis were utilized to identify the pro‑ and anti‑apoptotic proteins that interacted with PKC‑δ. Significant cell apoptosis was observed in Tca8113 cells following hyperthermia, and the apoptotic rate was significantly higher than that in the control group (P<0.05). Marked PKC‑δ cleavage fragmentation was also identified. By contrast, the apoptotic rate of the TT‑Tca8113 cells was not significantly increased following hyperthermia and no PKC‑δ cleavage fragmentation was observed. Among the proteins interacting with PKC‑δ, 39 were found to be involved in the promotion of apoptosis and 16 in the inhibition of apoptosis of Tca8113 cells; these proteins were known to be involved in the regulation of cell proliferation, apoptosis, transcription and intracellular protein transport. The results of the present study provided evidence that PKC‑δ is a crucial factor in the heat sensitivity and thermal resistance of tongue squamous carcinoma cells and elucidated the underlying molecular basis, which may aid in the improvement of hyperthermic cancer treatments.

Endoplasmic reticulum oxidoreductin 1α mediates homocysteine-induced hepatocyte endoplasmic reticulum stress

AIM: To assess the role of endoplasmic reticulum oxidoreductin 1α (ERO1α) in homocysteine (Hcy)-induced endoplasmic reticulum stress (ERS).

METHODS: Hepatocytes were cultured in the presence or absence of Hcy (100 μmol/L), and ELISA was used to determine the concentrations of of glucose-regulated protein 78 (GRP78), X-box binding protein-1 (XBP-1), protein kinase RNA-like endoplasmic reticulum kinase (PERK) and activating transcription factor 6 (ATF6). Hepatocytes were then cultured with different concentrations of Hcy (0, 50, 100, 200, 500 μmol/L) and 100 μmol/L Hcy plus folic acid and vitamin B₁₂, and the expression of ERO1α was detected by qRT-PCR and Western blot. ERO1α recombinant plasmid and ERO1α small interfering RNAs were then used to transfect hepatocytes, and the expression of ERO1α and the concentrations of GRP78, PERK, ATF6 and XBP-1 were measured.

RESULTS: Compared with non-treated cells, the concentrations of GRP78, PERK, ATF6 and XBP-1 significantly increased in Hcy-treated cells (P < 0.01, P < 0.01, P < 0.05, P < 0.01). Hcy decreased the expression of ERO1α at mRNA and protein levels (P < 0.01) in a dose-dependent manner. Transfection with ERO1α recombinant plasmid significantly increased the expression of ERO1α (P < 0.01), while transfection with three ERO1α small interfering RNAs significantly decreased the expression of ERO1α, with siRNA2 having the most significant effect (P < 0.01). Compared with the Hcy group, the concentrations of GRP78, PERK, ATF6 and XBP-1 significantly decreased in the Hcy + pERO1α recombinant plasmid group (P < 0.05), but increased in the Hcy + siRNA2 group (P < 0.01).

CONCLUSION: ERO1α may be involved in Hcy-induced hepatocyte ERS possibly by regulation of the GRP78-XBP-1/PERK/ATF6 signal pathway.