Protective role of HSP27 against UVC-induced cell death in human cells

Targeting metabolic syndrome with phytochemicals: Focus on the role of molecular chaperones and hormesis in drug discovery

Adaptive cellular stress response confers stress tolerance against inflammatory and metabolic disorders. In response to metabolic stress, the key mediator of cellular adaptation and tolerance is a class of molecules called the molecular chaperones (MCs). MCs are highly conserved molecules that play critical role in maintaining protein stability and functionality. Hormesis in this context is a unique adaptation mechanism where a low dose of a stressor (which is toxic at high dose) confers a stress-resistant adaptive cellular phenotype. Hormesis can be observed at different level of biological organization at various measurable endpoints. The MCs are believed to play a key role in adaptation during hormesis. Several phytochemicals are known for their hormetic response and are called phytochemical hormetins. The role of phytochemical-mediated hormesis on the adaptive cellular processes is proposed as a potential therapeutic approach to target inflammation associated with metabolic syndrome. However, the screening of phytochemical hormetins would require a paradigm shift in the methods currently used in drug discovery.

Advances in DNA Repair-Emerging Players in the Arena of Eukaryotic DNA Repair

Genomic DNA is constantly damaged by factors produced during natural metabolic processes as well as agents coming from the external environment. Considering such a wide array of damaging agents, eukaryotic cells have evolved a DNA damage response (DRR) that opposes the influence of deleterious factors. Despite the broad knowledge regarding DNA damage and repair, new areas of research are emerging. New players in the field of DDR are constantly being discovered. The aim of this study is to review current knowledge regarding the roles of sirtuins, heat shock proteins, long-noncoding RNAs and the circadian clock in DDR and distinguish new agents that may have a prominent role in DNA damage response and repair.

Heat shock proteins and DNA repair mechanisms: an updated overview

Heat shock proteins (HSPs), also known as molecular chaperones, participate in important cellular processes, such as protein aggregation, disaggregation, folding, and unfolding. HSPs have cytoprotective functions that are commonly explained by their antiapoptotic role. Their involvement in anticancer drug resistance has been the focus of intense research efforts, and the relationship between HSP induction and DNA repair mechanisms has been in the spotlight during the past decades. Because DNA is permanently subject to damage, many DNA repair pathways are involved in the recognition and removal of a diverse array of DNA lesions. Hence, DNA repair mechanisms are key to maintain genome stability. In addition, the interactome network of HSPs with DNA repair proteins has become an exciting research field and so their use as emerging targets for cancer therapy. This article provides a historical overview of the participation of HSPs in DNA repair mechanisms as part of their molecular chaperone capabilities.

The involvement of annexin II in resistance to UVB-induced cell death and in the increased nucleotide excision repair capacity of UV-damaged DNA in human cells

Annexin II, an HSP27-interacting protein, is involved in the protection of human cells against UVC. UVB is concerned with deleterious actions on human health. In this study, we attempted to confirm the anti-UVB effect of annexin II, and to elucidate the mechanisms underlying annexin II-involving UV resistance. The RSa cells were more sensitive to UVB lethality than the AP(r)-1 cells. Overproduction of annexin II in RSa cells resulted in increased resistance to UVB lethality, while annexin II siRNA-transfected AP(r)-1 cells were sensitized to UVB lethality. The excision capacity of the two major types (CPD and 6-4PP) of UVC- and UVB-damaged DNA in AP(r)-1 cells was greater than in RSa cells. The excision capacity of the RSa cells improved following upregulation of annexin II, while the capacity of the AP(r)-1 cells decreased after annexin II downregulation. Our results suggest that annexin II is involved in the UV resistance of human cells, via functioning in nucleotide excision repair.

Extracellular release of annexin II from pancreatic cancer cells and resistance to anticancer drug-induced apoptosis by supplementation of recombinant annexin II

OBJECTIVES

Extracellular microenvironment plays crucial roles in the development of cancers and chemoresistance. Pancreatic carcinoma is resistant to almost all chemotherapeutic agents. In this study, we identified annexin II in the medium from pancreatic cancer cells as a protein released into the extracellular environment.

METHODS

Medium from 5-hour cultures of various cancer cells was collected. Proteins in the medium were detected by molecular mass analysis and immunoblotting. Anticancer drug sensitivity of cells preincubated with or without recombinant annexin II (rANX II) was measured using crystal violet assay and colony survival assay. Apoptosis-related molecules were analyzed by immunoblotting.

RESULTS

Recombinant ANX II supplementation in the medium confers resistance to anticancer drugs, including cisplatin, 5-fluorouracil, and gemcitabine, in MiaPaCa-2 and AsPC-1 cells. In MiaPaCa-2 cells, rANX II supplementation resulted in suppression of caspase-3 activation associated with increased Bcl-2/Bax ratios. Suppression of cisplatin-induced cell death by rANX II supplementation was canceled by inhibitors of phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase signal pathways.

CONCLUSIONS

The current study is the first report to demonstrate that supplementation of rANX II in the medium increased resistance to anticancer drugs in pancreatic cancer cells. Recombinant ANX II exerts cell death-suppressive function by antagonizing cisplatin-induced apoptosis.

Involvement of heat shock protein 27 in the susceptibility of KT human breast cancer cells to UVC and interferon lethality

Revealing the key molecules regulating the stress-response pathways in human cells is an intriguing problem. Chaperones, such as glucose-regulated protein 78 (GRP78) and heat shock protein 27 (HSP27), are important molecules for protecting the viability of human cells; however, it remains to be further clarified whether the molecules differentially modulate cellular responses to various types of stressors, such as DNA-damaging ultraviolet ray C (principally 254-nm wavelength, UVC) and cytocidal cytokine interferons. In the present study, the human breast cancer cell lines KT and MCF-7 were examined for GRP78 and HSP27 expression following exposure to UVC and human interferon-β (HuIFN-β). The KT cells demonstrated a higher sensitivity to both UVC and HuIFN-β lethality than MCF-7 cells. The cellular expression levels of GRP78 in KT cells, assessed by western blot analysis, were approximately 2-fold higher than that in MCF-7 cells, while the expression of HSP27 in the KT cells was 20% of the expression in the MCF-7 cells. Decreased resistance to UVC lethality was observed in GRP78 siRNA-transfected KT cells. In addition, HSP27 cDNA transfection of KT cells resulted in an increased resistance to UVC lethality. The cDNA-transfected KT cells showed an increased viability against HuIFN-β, compared with that of empty vector-transfected cells. By contrast, KT cells pretreated with HuIFN-β and irradiated with UVC demonstrated an increased resistance to UVC lethality, in association with increased levels of HSP27 expression. Thus, HSP27 may control the survival response pathways to both UVC and HuIFN-β in the human cells examined.

Identification of heat shock protein 27 as a radioresistance-related protein in nasopharyngeal carcinoma cells

PURPOSE

To identify the proteins involved in radioresistance in nasopharyngeal cancer (NPC) cells.

METHODS

Sublethal ionizing radiation was applied to establish a radioresistant NPC cell line from its parental NPC cell line CNE1. Clonogenic survival assay, cell growth assay and flow cytometry analysis were used to examine the difference of radiosensitivity in the radioresistant CNE1 cells (CNE1-IR) and control CNE1 cells. Comparative proteomics was performed to identify the differential proteins in the two cell lines. Association of HSP27, one of upregulated proteins in CNE1-IR cells, with NPC cell radioresistance was selected for further investigation using antisense oligonucleotides (ASOs), clonogenic survival assay, Hoechst 33258 staining of apoptotic cells and MTT assay of cell viability.

RESULTS

Radioresistant NPC cell line CNE1-IR derived from its parental cell line CNE1 was established. Thirteen differential proteins in the CNE1-IR and CNE1 cells were identified by proteomics, and differential expression of HSP27, one of identified proteins, was selectively confirmed by western blot. Inhibition of HSP27 expression by HSP27 ASOs decreased clonogenic survival and cell viability and increased cell apoptosis of CNE1-IR cells after irradiation, that is, enhanced radiosensitivity of CNE1-IR cells.

CONCLUSION

The data suggest that HSP27 is a radioresistant protein in NPC cells, and its upregulation may be involved in the NPC radioresistance.

Hsp27 protects adenocarcinoma cells from UV-induced apoptosis by Akt and p21-dependent pathways of survival

Transcriptional activation of p53 target genes, due to DNA damage, causes either apoptosis or survival by cell cycle arrest and DNA repair. However, the regulators of the choice between cell death and survival signaling have not been completely elucidated. Here, we report that human adenocarcinoma cells (MCF-7) survive UV-induced DNA damage by heat shock protein 27 (Hsp27)-assisted Akt/p21 phosphorylation/translocation. Protein levels of the p53 target genes, such as p21, Bcl-2, p38MAPK, and Akt, showed a positive correlation to Hsp27 level during 48 hours postirradiation, whereas p53 expression increased initially but started decreasing after 12 hours. Hsp27 prevented the G(1)-S phase cell cycle arrest, observed after 8 hours of post-UV irradiation, and PARP-1 cleavage was inhibited. Conversely, silencing Hsp27 enhanced G(1)-S arrest and cell death. Moreover, use of either Hsp27 or Akt small interference RNA reduced p21 phosphorylation and enhanced its retention in nuclei even after 48 hours postirradiation, resulting in enhanced cell death. Our results showed that Hsp27 expression and its direct chaperoning interaction increases Akt stability, and p21 phosphorylation and nuclear-to-cytoplasm translocation, both essential effects for the survival of UV-induced DNA-damaged cells. We conclude that the role of Hsp27 in cancer is not only for enhanced p53 proteolysis per se, rather it is also a critical determinant in p21 phosphorylation and translocation.

The roles of HSP27 and annexin II in resistance to UVC-induced cell death: comparative studies of the human UVC-sensitive and -resistant cell lines RSa and APr-1

We have reported that heat shock protein 27 (HSP27) and annexin II are involved in the protection of human cells against UVC-induced cell death. In this study we tried to confirm the combined roles of HSP27 and annexin II in cell death after UVC irradiation. In RSa cells with sensitivity to UVC, expression of annexin II decreased after UVC irradiation, but not in AP(r)-1 cells with increased resistance to UVC. HSP27 siRNA-transfected AP(r)-1 cells were sensitized to UVC lethality and showed decreased annexin II expression after UVC irradiation. In contrast, transfection of RSa cells with HSP27 cDNA increased their resistance to UVC lethality and caused increased annexin II expression. Furthermore, over-production of annexin II in RSa cells resulted in increased resistance to UVC lethality. This study indicates the involvement of cellular HSP27 expression in the UVC susceptibility of human cells, which occurs in association with regulation of annexin II expression.

The level of Hsp27 in lymphocytes is negatively associated with a higher risk of lung cancer

Heat shock proteins (Hsps) can protect cells, organs, and whole organisms against damage caused by abnormal environmental hazards. Some studies have reported that lymphocyte Hsps may serve as biomarkers for evaluating disease status and exposure to environmental stresses; however, few epidemiologic studies have examined the associations between lymphocyte Hsps levels and lung cancer risk. We examined lymphocyte levels of Hsp27 and Hsp70 in 263 lung cancer cases and age- and gender-matched cancer-free controls by flow cytometry. Multivariate logistic regression models were used to estimate the association between lymphocyte Hsps levels and lung cancer risk. Our results showed that Hsp27 levels were significantly lower in lung cancer cases than in controls (16.5 vs 17.8 mean fluorescence intensity, P < 0.001). This was not observed for Hsp70 levels. Further stratification analysis revealed that lymphocyte Hsp27 levels were negatively associated with lung cancer risk especially in males and heavy smokers. There was a statistical trend of low odd ratios (95% confidence intervals) and upper tertile levels of Hsp27 [1.000, 0.904 (0.566-1.444) and 0.382 (0.221-0.658, P (trend) = 0.001) in males and 1.000, 0.9207 (0.465-1.822) and 0.419 (0.195-0.897, P (trend) = 0.036) in heavy smokers] after adjustment for confounding factors. These results suggest that lower lymphocyte Hsp27 levels might be associated with an increased risk of lung cancer. Our findings need to be validated in a large prospective study.

Strategies to promote donor cell survival: combining preconditioning approach with stem cell transplantation

Stem cell transplantation has emerged as a potential modality in cardiovascular therapeutics due to their inherent characteristics of self-renewal, unlimited capacity for proliferation and ability to cross lineage restrictions and adopt different phenotypes. Constrained by extensive death in the unfriendly milieu of ischemic myocardium, the results of heart cell therapy in experimental animal models as well as clinical studies have been less than optimal. Several factors which play a role in early cell death after engraftment in the ischemic myocardium include: absence of survival factors in the transplanted heart, disruption of cell-cell interaction coupled with loss of survival signals from matrix attachments, insufficient vascular supply and elaboration of inflammatory cytokines resulting from ischemia and/or cell death. This article reviews various signaling pathways involved in triggering highly complex forms of cell death and provides critical appreciation of different novel anti-death strategies developed from the knowledge gained from using an ischemic preconditioning approach. The use of pharmacological preconditioning for up-regulation of pro-survival proteins and cardiogenic markers in the transplanted stem cells will be discussed.

Hsp27, Hsp70 and mismatch repair proteins hMLH1 and hMSH2 expression in peripheral blood lymphocytes from healthy subjects and cancer patients

Mismatch repair (MMR) deficiency and higher expression levels of heat shock proteins (Hsps) have been implicated with drug resistance to topoisomerase II poisons (doxorubicin) and to platinum compounds (cisplatin). This study was designed to determine individual influences of doxorubicin and cisplatin treatment on the expression of Hsp27, Hsp70, hMLH1 and hMSH2 proteins and in the DNA damage status in peripheral blood lymphocytes (PBLs). In addition, we studied whether these proteins and the DNA damage correlated with the survival of cancer patients. PBLs from 10 healthy donors and 25 cancer patients (before and after three cycles of chemotherapy) were exposed to in vitro treatments: C (control), HS (heat shock at 42 degrees C), Do or Pt (doxorubicin or cisplatin alone), and HS+Do or HS+Pt (heat shock+doxorubicin or heat shock+cisplatin). PBLs were collected at time 0 (T0: immediately after drug treatment) and after 24h of repair (T24). Hsp27, Hsp70, hMLH1 and hMSH2 were studied by immunocytochemistry and the DNA damage by alkaline comet assay. Immunofluorescence studies and confocal microscopy revealed that hMLH1 and hMSH2 colocalized with Hsp27 and Hsp72 (inducible form of Hsp70). hMLH1 and hMSH2 were significantly induced by Pt and HS+Pt at T24 in cancer patients, but only modestly influenced by Do. Cancer patients presented higher basal expression of total and nuclear Hsp27 and Hsp70 than controls, and these proteins were also increased by HS, Do and HS+Do. The Hsp70 induction by Pt and HS+Pt was noted in cancer patients, especially nuclear Hsp70. In cancer patients, basal DNA damage was slightly higher than in healthy persons; and after Pt and HS+Pt treatments, DNA migration and number of apoptotic cells were higher than controls. Hsps accomplished a cytoprotective function in pre-chemotherapy PBLs (HS before Do or Pt), but not in post-chemotherapy samples. In Pt-treated patients the ratio N/C (nuclear/cytoplasmic) of Hsp27 was related to disease free survival and overall survival, and hMSH2 correlated with overall survival. The results point to the utility of these molecules and of the comet assay as possible predictive markers.

Overexpressed heat shock protein 70 protects cells against DNA damage caused by ultraviolet C in a dose-dependent manner

Heat shock protein 70 (Hsp70) comprises proteins that have been reported to protect cells, tissues, and organisms against damage from a wide variety of stressful stimuli; however, little is known about whether Hsp70 protects against DNA damage. In this study, we investigated the relationship between Hsp70 expression and the levels of ultraviolet C (UVC)-induced DNA damage in A549 cells with normal, inhibited, and overexpressed Hsp70 levels. Hsp70 expression was inhibited by treatment with quercetin or overexpressed by transfection of plasmids harboring the hsp70 gene. The level of DNA damage was assessed by the comet assay. The results showed that the levels of DNA damage (shown as the percentage of comet cells) in A549 cells increased in all cells after exposure to an incident dose of 0, 10, 20, 40, and 80 J/m2 whether Hsp70 was inhibited or overexpressed. This response was dose dependent: a protection against UVC-induced DNA damage in cells with overexpressed Hsp70 was observed at UVC dose 20 J/m2 with a maximum at 40 J/m2 when compared with cells with normal Hsp70 levels and in quercetin-treated cells. This differential protection disappeared at 80 J/m2. These results suggest that overexpressed Hsp70 might play a role in protecting A549 cells from DNA damage caused by UVC irradiation, with a threshold of protection from at UVC irradiation-induced DNA damage by Hsp70. The detailed mechanism how Hsp70 is involved in DNA damage and possible DNA repair warrants further investigation.

Enhanced expression of transferrin receptor confers UV-resistance in human and monkey cells

One of the most intriguing biological subjects is cell-surface molecules that regulate the susceptibility of human cells to cell-killing effects after irradiation with far-ultraviolet light (UV, principally 254 nm wavelength). Human RSa cells have unusual sensitivity to UV-induced cell-killing. We searched for molecules on the cell-surface of RSa cells that were present in different amounts as compared to a variant of these cells, UV(r)-1 cells, which have increased resistance to UV cell-killing. Among the 21 molecules examined, the amount of transferrin receptor (TfR) protein was found to be 2-fold higher in UV(r)-1 cells compared with in RSa cells. The amounts of this protein were also higher in the UV-resistant hematopoietic cell lines, CEM6 and Daudi, as compared to the UV-sensitive cell lines, Molt4 and 697. Culturing of UV(r)-1 cells in a medium containing anti-transferrin antibodies resulted in sensitization of the cells to UV cell-killing as demonstrated by colony formation assay. Similar results were observed by treatment of the cells with TfR siRNA. In contrast, overexpression of TfR protein led to a resistance to UV cell-killing in RSa cells and monkey COS7 cells as demonstrated by both colony formation and apoptosis assay. In TfR-overexpressing cells, reduction of p53 and Bax protein was observed after UV-irradiation. Thus, TfR expression appears to be involved in the regulation of UV-resistance, possibly via modulation of the amount of p53 and Bax protein.

Decreased cell survival and DNA repair capacity after UVC irradiation in association with down-regulation of GRP78/BiP in human RSa cells

In contrast to extensive studies on the roles of molecular chaperones, such as heat shock proteins, there are only a few reports about the roles of GRP78/BiP, an endoplasmic reticulum (ER) stress-induced molecular chaperone, in mammalian cell responses to DNA-damaging stresses. To investigate whether GRP78/BiP is involved in resistance to a DNA-damaging agent, UVC (principally 254 nm in wavelength), we established human cells with down-regulation of GRP78/BiP by transfection of human RSa cells with antisense cDNA for GRP78/BiP. We found that the transfected cells showed higher sensitivity to UVC-induced cell death than control cells transfected with the vector alone. In the antisense-cDNA transfected cells, the removal capacities of the two major types of UVC-damaged DNA (thymine dimers and (6-4) photoproducts) in vivo and DNA synthesis activity of whole cell extracts to repair UVC-irradiated plasmids in vitro were remarkably decreased compared with those in the control cells. Furthermore, the antisense-cDNA transfected cells also showed slightly higher sensitivity to cisplatin-induced cell death than the control cells. Cisplatin-induced DNA damage is primarily repaired by nucleotide excision repair, like UVC-induced DNA damage. The present results suggest that GRP78/BiP plays a protective role against UVC-induced cell death possibly via nucleotide excision repair, at least in the human RSa cells tested.