Protective role of Hsp27 protein against gamma radiation-induced apoptosis and radiosensitization effects of Hsp27 gene silencing in different human tumor cells

Promoter methylation of heat shock protein B2 in human esophageal squamous cell carcinoma

Hypermethylation of gene promoters and the corresponding loss of gene expression are recognized as a hallmark of human cancer, and DNA methylation has emerged as a promising biomarker for the detection of human esophageal squamous cell carcinoma (ESCC). To identify novel genes methylated in ESCC, we screened 35 candidate genes identified from an oligonucleotide microarray. Among them, the heat shock protein B2 (HSPB2) was methylated in 95.7% (67/70) of primary ESCCs, whereas no methylation was found in normal esophageal tissues from ESCC patients (0%, 0/20). RT-PCR analysis revealed that HSPB2 expression was silenced or weakly expressed in most ESCC cell lines, and re-activated by the demethylating agent 5-aza-2'-deoxy-cytidine. These results indicate that promoter methylation of HSPB2 is one of the causal factors for loss or down-regulation of HSPB2 expression. mRNA expression of HSPB2 in ESCC tissues was significantly down-regulated compared to normal tissues. Our data suggest that promoter methylation of HSPB2 deserves further attention as a novel molecular biomarker in human ESCC.

Inhibition of heat shock protein 27 (HspB1) tumorigenic functions by peptide aptamers

Human heat shock protein 27 (Hsp27, HspB1) is an anti-apoptotic protein characterized for its tumorigenic and metastatic properties, and now referenced as a major therapeutic target in many types of cancer. Hsp27 biochemical properties rely on a structural oligomeric and dynamic organization. Downregulation by small interfering RNA or inhibition with dominant-negative mutant have proven their efficiency to counteract the anti-apoptotic and protective properties of Hsp27. In this study, we report the isolation and characterization of Hsp27-targeted molecules interfering with its structural organization. Using the peptide aptamer (PA) strategy, we isolated PAs that specifically interact with Hsp27 and not with the other members of the small heat shock protein family. In mammalian cell cultures, PAs expression perturbed the dimerization and oligomerization of Hsp27, and acted as negative regulators of the anti-apoptotic and cytoprotective activities of this protein. Further studies analyzing SQ20B cell xenografts in immunocompromised mice showed that PAs strongly reduced tumor development through cell cycle arrest. Our data suggest that PAs could provide a potential tool to develop strategies for the discovery of Hsp27 chemical inhibitors.

Hyperthermia-induced apoptosis in Tca8113 cells is inhibited by heat shock protein 27 through blocking phospholipid scramblase 3 phosphorylation

PURPOSE

Hyperthermia induces tumour cell apoptosis through the mitochondrial apoptotic pathway; however, the signal transduction mechanism underlying this process still needs to be fully elucidated. Phospholipid scramblase 3 (PLS3), a target of protein kinase C-delta (PKC-delta), resides in mitochondria and plays pivotal roles in regulating apoptotic response. Activated PLS3 facilitates cardiolipin (CL) translocation from the mitochondrial inner membrane to the outer leaflet of the mitochondrial outer membrane and triggers apoptosis.

MATERIALS AND METHODS

The tongue squamous cell carcinoma Tca8113 cells were transfected or co-transfected using Lipofectamine 2000 with plasmids pCMV-6xHis-PLS3, pCMV-6xHis-PLS3 (T21A), pHA-PKC-delta, pHA-PKC-delta-KD (K376R), pHA-Hsp27, and empty control plasmid pcDNA3.1. The transfected cells were heated in water bath at 43 degrees C for 20 min, 40 min and 60 min. Assessments of apoptosis and redistribution of mitochondrial cardiolipin were performed by flow cytometry. PLS3, PKC-delta, Hsp27, phosphorylation of PLS3 and PLS3/PKC-delta interaction were detected by western blotting.

RESULTS

In our study the results show that elevated levels of the wild-type PLS3, but not the PLS3 (T21A) mutant, is able to increase hyperthermia-induced CL translocation and apoptosis. Wild-type PKC-delta facilitates PLS3 phosphorylation, PKC-delta/PLS3 interaction, and CL translocation, which consequently promote apoptosis. In contrast, heat shock protein 27 (Hsp27) blocks PKC-delta-induced PLS3 phosphorylation, suppresses PKC-delta/PLS3 interaction and CL translocation, and inhibits apoptosis.

CONCLUSIONS

Our findings suggest that phosphorylation of PLS3 by PKC-delta is involved in the hyperthermia-induced apoptotic signal transduction pathway in Tca8113 cells, and that Hsp27 blocks this pathway to suppress hyperthermia-induced apoptosis.

HLJ1 is a novel caspase-3 substrate and its expression enhances UV-induced apoptosis in non-small cell lung carcinoma

Carcinogenesis is determined based on both cell proliferation and death rates. Recent studies demonstrate that heat shock proteins (HSPs) regulate apoptosis. HLJ1, a member of the DnaJ-like Hsp40 family, is a newly identified tumor suppressor protein closely related to relapse and survival in non-small cell lung cancer (NSCLC) patients. However, its role in apoptosis is currently unknown. In this study, NSCLC cell lines displaying varying HLJ1 expression levels were subjected to ultraviolet (UV) irradiation, followed by flow cytometry. Interestingly, the percentages of apoptotic cells in the seven cell lines examined were positively correlated with HLJ1 expression. Enforcing expression of HLJ1 in low-HLJ1 expressing highly invasive cells promoted UV-induced apoptosis through enhancing JNK and caspase-3 activation in NSCLC. Additionally, UV irradiation led to reduced levels of HLJ1 predominantly in apoptotic cells. The pan-caspase inhibitor, zVAD-fmk and caspase-3-specific inhibitor, DEVD-fmk, prevented UV-induced degradation of HLJ1 by the late stage of apoptosis. Further experiments revealed a non-typical caspase-3 cleavage site (MEID) at amino acid 125-128 of HLJ1. Our results collectively suggest that HLJ1 is a novel substrate of caspase-3 during the UV-induced apoptotic process.

Dynamic processes that reflect anti-apoptotic strategies set up by HspB1 (Hsp27)

Human HspB1 (also denoted Hsp27) is an oligomeric anti-apoptotic protein that has tumorigenic and metastatic roles. To approach the structural organizations of HspB1 that are active in response to apoptosis inducers acting through different pathways, we have analyzed the relative protective efficiency induced by this protein as well its localization, oligomerization and phosphorylation. HeLa cells, that constitutively express high levels of HspB1 were treated with either etoposide, Fas agonist antibody, staurosporine or cytochalasin D. Variability in HspB1 efficiency to interfere with the different apoptotic transduction pathways induced by these agents were detected. Moreover, inducer-specific dynamic changes in HspB1 localization, native size and phosphorylation were observed, that differed from those observed after heat shock. Etoposide and Fas treatments gradually shifted HspB1 towards large but differently phosphorylated oligomeric structures. In contrast, staurosporine and cytochalasin D induced the rapid but transient formation of small oligomers before large structures were formed. These events correlated with inducer-specific phosphorylations of HspB1. Of interest, the formation of small oligomers in response to staurosporine and cytochalasin D was time correlated with the rapid disruption of F-actin. The subsequent, or gradual in the case of etoposide and Fas, formation of large oligomeric structures was a later event concomitant with the early phase of caspase activation. These observations support the hypothesis that HspB1 has the ability, through specific changes in its structural organization, to adapt and interfere at several levels with challenges triggered by different signal transduction pathways upstream of the execution phase of apoptosis.

Differential heat shock protein localization in chronic lymphocytic leukemia

Mechanisms behind carcinogenesis and resistance of tumor cells to treatment regimes remain elusive. The major stress proteins Hsp72, Hsp90, and Hsp27 are credible candidates to provide this resistance, as their overexpression in many cancer types is well documented. In addition to being present inside tumor cells, where they confer resistance to apoptosis, Hsp72, in particular, is presented externally, embedded in the cell membrane of cancer cells. This study aimed to investigate the localization of Hsp72, Hsp90, and Hsp27 in leukocytes from patients with CLL and age-matched control subjects. CLL patients were found to express significantly higher levels of iHsp90 (CLL=2463 MFI; control=748 MFI) and iHsp27 (CLL=2190 MFI; control=1031 MFI) in lymphocytes than that expressed by lymphocytes from control subjects. Furthermore, expression of iHsp90 was shown to be related to stage of disease, and expression of iHsp27 correlated with levels of active caspase-3. Patients were found to express very high levels or very low levels of sHsp72 and iHsp72 in CD5(+)/CD19(+) cells, although surface and intracellular datasets did not correlate. Levels of extracellular Hsp72 circulating in the serum were found to correlate with internal levels of Hsp72 and were also found to be significantly lower in patients receiving corticosteroid treatment than in patients not receiving corticosteroid treatment. Finally, analysis of the number of circulating Tregs revealed significantly elevated numbers in CLL patients compared with control subjects.

Molecular fingerprinting of radiation resistant tumors: can we apprehend and rehabilitate the suspects?

Radiation therapy continues to be one of the more popular treatment options for localized prostate cancer. One major obstacle to radiation therapy is that there is a limit to the amount of radiation that can be safely delivered to the target organ. Emerging evidence suggests that therapeutic agents targeting specific molecules might be combined with radiation therapy for more effective treatment of tumors. Recent studies suggest that modulation of these molecules by a variety of mechanisms (e.g., gene therapy, antisense oligonucleotides, small interfering RNA) may enhance the efficacy of radiation therapy by modifying the activity of key cell proliferation and survival pathways such as those controlled by Bcl-2, p53, Akt/PTEN and cyclooxygenase-2. In this article, we summarize the findings of recent investigations of radiosensitizing agents in the treatment of prostate cancer.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part II: targeting cell cycle events, caspases, NF-κB and the proteasome

BACKGROUND

Endoplasmic reticulum stress (ERS), the unfolded protein response (UPR) and apoptosis signal transduction pathways are fundamental to normal cellular homeostasis and survival, but are exploited by cancer cells to promote the cancer phenotype.

OBJECTIVE

Collateral activation of ERS and UPR role players impact on cell growth, cell cycle arrest or apoptosis, genomic stability, tumour initiation and progression, tumour aggressiveness and drug resistance. An understanding of these processes affords promising prospects for specific cancer drug targeting of the ERS, UPR and apoptotic pathways.

METHOD

This review (Part II of II) brings forward the latest developments relevant to the molecular connections among cell cycle regulators, caspases, NF-κB, and the proteasome with ERS and UPR signalling cascades, their functions in apoptosis induction, apoptosis resistance and oncogenesis, and how these relationships can be exploited for targeted cancer therapy.

CONCLUSION

Overall, ERS, the UPR and apoptosis signalling cascades (the molecular therapeutic targets) and the development of drugs that attack these targets signify a success story in cancer drug discovery, but a more reductionist approach is necessary to determine the precise molecular switches that turn on antiapoptotic and pro-apoptotic programmes.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

BACKGROUND

In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival.

OBJECTIVE

This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies.

METHOD

In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis.

CONCLUSION

Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.

Dysregulation of heat shock protein 27 expression in oral tongue squamous cell carcinoma

Background

Recent proteomic studies identified Hsp27 as a highly over-expressed protein in oral squamous cell carcinoma (OSCC). Clinical studies that attempted to evaluate the prognostic values of Hsp27 yielded inconsistent results, which may be due to inclusion of OSCC cases from multiple anatomic sites. In this study, to determine the utility of Hsp27 for prognosis, we focused on oral tongue SCC (OTSCC), one of the most aggressive forms of OSCC.

Methods

Archival clinical samples of 15 normal oral tongue mucosa, 31 dysplastic lesions, 80 primary OTSCC, and 32 lymph node metastases were examined for Hsp27 expression by immunohistochemistry (IHC). Statistical analyses were carried out to assess the prognostic value of Hsp27 expression for patients with this disease.

Results

Dysregulation of Hsp27 expression was observed in dysplastic lesions, primary OTSCC, and lymph node metastases, and appears to be associated with disease progression. Statistical analysis revealed that the reduced Hsp27 expression in primary tumor tissue was associated with poor differentiation. Furthermore, the higher expression of Hsp27 was correlated with better overall survival.

Conclusion

Our study confirmed that the dysregulation of Hsp27 expression is a frequent event during the progression of OTSCC. The expression of Hsp27 appears to be an independent prognostic marker for patients with this disease.

Heat shock protein 27 as a new therapeutic target for radiation sensitization of head and neck squamous cell carcinoma

In a wide range of human cancers, increased levels of heat shock protein 27 (Hsp27) are closely associated with tumorigenesis, metastasis, resistance to anticancer therapeutics, and thus poor prognosis. In this study, we evaluate the radiosensitizing effects of Hsp27 gene silencing using OGX-427, a second-generation antisense oligonucleotide (ASO), on the radioresistant head and neck squamous cell carcinoma (HNSCC) SQ20B cells. In vitro, the downregulation of Hsp27 significantly enhanced radiation-induced apoptotic and clonogenic death, and promoted Akt inactivation. In vivo, combining OGX-427 with local tumor irradiation (5 x 2 Gy) led to a significant regression of SQ20B tumors related to a high rate of apoptosis and decreased levels of glutathione antioxidant defenses. Increasing the total radiation dose (15 x 2 Gy) significantly amplified the radiosensitizing effect of OGX-427. Treatment of tumors with OGX-427 plus radiation resulted in a decrease in angiogenesis associated with a reduced activation of the Akt pathway. Furthermore, the combined treatment enhanced the survival of SQ20B-bearing mice and showed no signs of acute and delayed toxicity. Our findings demonstrate for the first time that Hsp27 knockdown enhances the cytotoxic effects of radiotherapy in vivo and provide preclinical proof of principle for clinical trials using Hsp27 antisense technology in the treatment of patients with HNSCC radioresistant cancers.

Effectiveness of monoenergetic and spread-out bragg peak carbon-ions for inactivation of various normal and tumour human cell lines

This work aimed at measuring cell-killing effectiveness of monoenergetic and Spread-Out Bragg Peak (SOBP) carbon-ion beams in normal and tumour cells with different radiation sensitivity. Clonogenic survival was assayed in normal and tumour human cell lines exhibiting different radiosensitivity to X- or gamma-rays following exposure to monoenergetic carbon-ion beams (incident LET 13-303 keV/microm) and at various positions along the ionization curve of a therapeutic carbon-ion beam, corresponding to three dose-averaged LET (LET(d)) values (40, 50 and 75 keV/microm). Chinese hamster V79 cells were also used. Carbon-ion effectiveness for cell inactivation generally increased with LET for monoenergetic beams, with the largest gain in cell-killing obtained in the cells most radioresistant to X- or gamma-rays. Such an increased effectiveness in cells less responsive to low LET radiation was found also for SOBP irradiation, but the latter was less effective compared with monoenergetic ion beams of the same LET. Our data show the superior effectiveness for cell-killing exhibited by carbon-ion beams compared to lower LET radiation, particularly in tumour cells radioresistant to X- or gamma-rays, hence the advantage of using such beams in radiotherapy. The observed lower effectiveness of SOBP irradiation compared to monoenergetic carbon beam irradiation argues against the radiobiological equivalence between dose-averaged LET in a point in the SOBP and the corresponding monoenergetic beams.

Life span alteration after irradiation in Drosophila melanogaster strains with mutations of Hsf and Hsps

The life span alteration after gamma-irradiation and/or paraquat treatment in Drosophila in wild type strain Canton-S and strains with mutations of heat shock factor (1-4 alleles) and heat shock proteins (Hsp70Ba ( 304 ), Hsp83 ( e6A ), Hsp22 ( EY09909 ), Hsp67Bb ( EY099099 )) was investigated. Chronic low-dose rate gamma-irradiation (0.017 and 0.17 cGy/h) on pre-imago stages was used as a priming dose (absorbed doses were 4 and 40 cGy). Paraquat, a free radical inducing agent, was a challenging factor (20 mM for 1 day). It was shown that chronic irradiation led to adaptive response in both sexes except homozygous males and females with mutations of Hsf ( 4 ) and Hsp70Ba ( 304 ). The gender-specific differences in stress response were discovered in wild type strain Canton-S, Hsp22 ( EY09909 ) Hsp67Bb ( EY09909 ) homozygotes and Hsp83 ( e6A ) heterozygotes: the adaptive response persisted in males, but not in females. Thus, Drosophila Hsp and Hsf mutation homozygotes did not demonstrate the adaptive response in the majority of cases, implying an important role of those genes in radiation hormesis and adaptation to stresses.