Functional inhibition of Hsp70 by Pifithrin-μ switches Gambogic acid induced caspase dependent cell death to caspase independent cell death in human bladder cancer cells

Pifithrin-µ Induces Stress Granule Formation, Regulates Cell Survival, and Rewires Cellular Signaling

(1) Background: Stress granules (SGs) are cytoplasmic protein-RNA condensates that assemble in response to various insults. SG production is driven by signaling pathways that are relevant to human disease. Compounds that modulate SG characteristics are therefore of clinical interest. Pifithrin-µ is a candidate anti-tumor agent that inhibits members of the hsp70 chaperone family. While hsp70s are required for granulostasis, the impact of pifithrin-µ on SG formation is unknown. (2) Methods: Using HeLa cells as model system, cell-based assays evaluated the effects of pifithrin-µ on cell viability. Quantitative Western blotting assessed cell signaling events and SG proteins. Confocal microscopy combined with quantitative image analyses examined multiple SG parameters. (3) Results: Pifithrin-µ induced bona fide SGs in the absence of exogenous stress. These SGs were dynamic; their properties were determined by the duration of pifithrin-µ treatment. The phosphorylation of eIF2α was mandatory to generate SGs upon pifithrin-µ exposure. Moreover, the formation of pifithrin-µ SGs was accompanied by profound changes in cell signaling. Pifithrin-µ reduced the activation of 5'-AMP-activated protein kinase, whereas the pro-survival protein kinase Akt was activated. Long-term pifithrin-µ treatment caused a marked loss of cell viability. (4) Conclusions: Our study identified stress-related changes in cellular homeostasis that are elicited by pifithrin-µ. These insights are important knowledge for the appropriate therapeutic use of pifithrin-µ and related compounds.

Role of heat shock protein 70 in regulation of anti-inflammatory response to curcumin in 3T3-L1 adipocytes

BACKGROUND/OBJECTIVES

Curcumin is a well-known phytochemical with anti-inflammatory effects. Heat shock protein (HSP) 70, an intracellular chaperone, inhibits proinflammatory signaling activation. Although curcumin has been shown to induce HSP70 expression in various cell types, whether HSP70 mediates the anti-inflammatory effects of curcumin in mature adipocytes remains unclear.

MATERIALS/METHODS

To assess the role of HSP70 in regulating the anti-inflammatory response to curcumin in adipocytes, fully differentiated 3T3-L1 adipocytes were treated with curcumin, lipopolysaccharide (LPS), and/or the HSP70 inhibitor pifithrin-μ (PFT-μ). The expression levels of HSP70 and proinflammatory cytokines were then measured.

RESULTS

Curcumin upregulated HSP70 expression at both protein and mRNA levels and attenuated LPS-induced Il6, Ptx3, and Ccl2 mRNA upregulation. PFT-μ tended to exacerbate the LPS-induced upregulation of Il6, Ptx3, Ccl2, and Tnfa mRNA expression. However, on curcumin pretreatment, the tendency of PFT-μ to upregulate LPS-induced proinflammatory cytokine expression decreased or disappeared.

CONCLUSION

These results indicate that HSP70 is involved in the regulation of inflammatory responses but may not be crucial for the anti-inflammatory effects of curcumin in 3T3-L1 adipocytes.

Non-coding RNA and autophagy: Finding novel ways to improve the diagnostic management of bladder cancer

Major fraction of the human genome is transcribed in to the RNA but is not translated in to any specific functional protein. These transcribed but not translated RNA molecules are called as non-coding RNA (ncRNA). There are thousands of different non-coding RNAs present inside the cells, each regulating different cellular pathway/pathways. Over the last few decades non-coding RNAs have been found to be involved in various diseases including cancer. Non-coding RNAs are reported to function both as tumor enhancer and/or tumor suppressor in almost each type of cancer. Urothelial carcinoma of the urinary bladder is the second most common urogenital malignancy in the world. Over the last few decades, non-coding RNAs were demonstrated to be linked with bladder cancer progression by modulating different signalling pathways and cellular processes such as autophagy, metastasis, drug resistance and tumor proliferation. Due to the heterogeneity of bladder cancer cells more in-depth molecular characterization is needed to identify new diagnostic and treatment options. This review emphasizes the current findings on non-coding RNAs and their relationship with various oncological processes such as autophagy, and their applicability to the pathophysiology of bladder cancer. This may offer an understanding of evolving non-coding RNA-targeted diagnostic tools and new therapeutic approaches for bladder cancer management in the future.

Prodrug Nanosensitizer Overcomes the Radiation Resistance of Hypoxic Tumor

Clinical radiation therapy (RT) is often hindered by the low radiation energy absorption coefficient and the hypoxic features of tumor tissues. Among the tremendous efforts devoted to overcoming the barriers to efficient RT, the application of hypoxic radiosensitizers and cell-cycle-specific chemotherapeutics has shown great potential. However, their effectiveness is often compromised by their limited bioavailability, especially in the hypoxic region, which plays a major role in radioresistance. Herein, to simultaneously improve the delivery efficacy of both hypoxic radiosensitizer and cell-cycle-specific drug, a gambogic acid (GA) metronidazole (MN) prodrug (GM) was designed and synthesized based on GA, a naturally occurring chemotherapeutic and multiple pathway inhibitor, and MN, a typical hypoxic radiosensitizer. In combination with MN-containing block copolymers, the prodrug nanosensitizer (NS) of GM was obtained. Owing to the bioreduction of MN, the as-designed prodrug could be efficiently delivered to hypoxic cells and act on mitochondria to cause the accumulation of reactive oxygen species. The strong G₂/M phase arrest caused by the prodrug NS could further sensitize treated cells to external radiation under hypoxic conditions by increasing DNA damage and delaying DNA repair. After coadministration of the NS with a well-established tissue-penetrating peptide, efficient tumor accumulation, deep tumor penetration, and highly potent chemoradiotherapy could be achieved.

PES derivative PESA is a potent tool to globally profile cellular targets of PES

PES (2-phenylethynesulfonamide, pifithrin-μ, PFTμ) is an electrophilic compound that exhibits anticancer properties, protects against chemotherapy-induced peripheral neuropathy in chemotherapy, and shows immunomodulatory, anti-inflammatory and anti-viral activities. PES generally shows higher cytotoxicity towards tumor cells than non-tumor cells. The mechanism of action of PES is unclear but may involve the covalent modification of proteins as PES has been found to be a covalent inhibitor of Hsp70. We developed a new PES derivative PESA with a terminal alkynyl group to perform click-reaction-assisted activity-based protein profiling (click-reaction ABPP) and used this to screen for cellular targets of PES. We found PES and its derivatives PES-Cl and PESA have comparable ability to undergo a Michael addition reaction with GSH and Hsp70, and showed similar cytotoxicity. By fluorescence imaging and proteomics studies we identified over 300 PESA-attached proteins in DOHH2 cells. Some proteins involved in cancer-related redox processes, such as peroxiredoxin 1 (PRDX1), showed higher frequency and abundance in mass spectrometry detection. Our results suggest that cytotoxicity of PES and its derivatives may be related to attack of protein thiols and cellular GSH resulting in breakdown of cellular redox homeostasis. This study provides a powerful new tool compound within the PES class of bioactive compounds and gives insight into the working mechanisms of PES and its derivatives.

Hsp70 in Liquid Biopsies-A Tumor-Specific Biomarker for Detection and Response Monitoring in Cancer

In contrast to normal cells, tumor cells of multiple entities overexpress the Heat shock protein 70 (Hsp70) not only in the cytosol, but also present it on their plasma membrane in a tumor-specific manner. Furthermore, membrane Hsp70-positive tumor cells actively release Hsp70 in small extracellular vesicles with biophysical characteristics of exosomes. Due to conformational changes of Hsp70 in a lipid environment, most commercially available antibodies fail to detect membrane-bound and vesicular Hsp70. To fill this gap and to assess the role of vesicular Hsp70 in circulation as a potential tumor biomarker, we established the novel complete (comp)Hsp70 sandwich ELISA, using two monoclonal antibodies (mAbs), that is able to recognize both free and lipid-associated Hsp70 on the cell surface of viable tumor cells and on small extracellular vesicles. The epitopes of the mAbs cmHsp70.1 (aa 451-461) and cmHsp70.2 (aa 614-623) that are conserved among different species reside in the substrate-binding domain of Hsp70 with measured affinities of 0.42 nM and 0.44 nM, respectively. Validation of the compHsp70 ELISA revealed a high intra- and inter-assay precision, linearity in a concentration range of 1.56 to 25 ng/mL, high recovery rates of spiked liposomal Hsp70 (>84%), comparable values between human serum and plasma samples and no interference by food intake or age of the donors. Hsp70 concentrations in the circulation of patients with glioblastoma, squamous cell or adeno non-small cell lung carcinoma (NSCLC) at diagnosis were significantly higher than those of healthy donors. Hsp70 concentrations dropped concomitantly with a decrease in viable tumor mass upon irradiation of patients with approximately 20 Gy (range 18-22.5 Gy) and after completion of radiotherapy (60-70 Gy). In summary, the compHsp70 ELISA presented herein provides a sensitive and reliable tool for measuring free and vesicular Hsp70 in liquid biopsies of tumor patients, levels of which can be used as a tumor-specific biomarker, for risk assessment (i.e., differentiation of grade III vs. IV adeno NSCLC) and monitoring of therapeutic outcomes.

2-phenylethynesulfonamide inhibits growth of oral squamous cell carcinoma cells by blocking the function of heat shock protein 70

Oral squamous cell carcinoma (OSCC) is the most common malignancy in the oral cavity, which accounts for >90% of all diagnosed oral cancers. 2-phenylethynesulfonamide (PES) was known as a selective heat shock protein 70 (Hsp70) function inhibitor, which induced cytotoxic effects on various tumor cell types, but showed to be less toxic to normal cells. However, no associated evaluation of PES on OSCC was found. In the present study, the proliferation of OSCC cells treated with PES was analyzed using a CCK-8 assay. The effects of PES on the cell cycle and apoptosis of OSCC cells were determined by flow cytometric analyses. Expression of associated protein was determined by Western blot analysis. The results of the present study showed that PES inhibited the proliferation of OSCC cell lines in vivo and in vitro. PES induced apoptosis and arrested the cell cycle of OSCC cells. PES inhibited the expression of X-linked inhibitor of apoptosis protein (XIAP), baculoviral IAP repeat containing 2 (c-IAP1), phosphorylated AKT (p-AKT), and phosphorylated extracellular signal-regulated kinase (p-ERK). Additionally, knockdown of Hsp70 enhanced the effects of PES. By contrast, overexpression of Hsp70 attenuated the inhibitory effects of PES on cell viability. PES disrupted the interaction between Hsp70 and XIAP. In conclusion, the present study demonstrated that PES suppresses the growth of OSCC cells through Hsp70-dependent mechanism.

A Novel Inhibitor of HSP70 Induces Mitochondrial Toxicity and Immune Cell Recruitment in Tumors

The protein chaperone HSP70 is overexpressed in many cancers including colorectal cancer, where overexpression is associated with poor survival. We report here the creation of a uniquely acting HSP70 inhibitor (HSP70i) that targets multiple compartments in the cancer cell, including mitochondria. This inhibitor was mitochondria toxic and cytotoxic to colorectal cancer cells, but not to normal colon epithelial cells. Inhibition of HSP70 was efficacious as a single agent in primary and metastatic models of colorectal cancer and enabled identification of novel mitochondrial client proteins for HSP70. In a syngeneic colorectal cancer model, the inhibitor increased immune cell recruitment into tumors. Cells treated with the inhibitor secreted danger-associated molecular patterns (DAMP), including ATP and HMGB1, and functioned effectively as a tumor vaccine. Interestingly, the unique properties of this HSP70i in the disruption of mitochondrial function and the inhibition of proteostasis both contributed to DAMP release. This HSP70i constitutes a promising therapeutic opportunity in colorectal cancer and may exhibit antitumor activity against other tumor types. SIGNIFICANCE: These findings describe a novel HSP70i that disrupts mitochondrial proteostasis, demonstrating single-agent efficacy that induces immunogenic cell death in treated tumors.

Autophagy in cancer: Recent advances and future directions

Autophagy is being explored as a potential therapeutic target for enhancing the cytotoxic effects of chemotherapeutic regimens in various malignancies. Autophagy plays a very important role in cancer pathogenesis. Here, we discuss the updates on the modulation of autophagy via dynamic interactions with different organelles and the exploitation of selective autophagy for exploring therapeutic strategies. We further discuss the role of autophagy inhibitors in cancer preclinical and clinical trials, novel autophagy inhibitors, and challenges likely to be faced by clinicians while inducting autophagy modulators in clinical practice.

Gambogic acid exhibits anti-metastatic activity on malignant melanoma mainly through inhibition of PI3K/Akt and ERK signaling pathways

Gambogic acid (GA) is a potential anti-cancer compound that is extracted from the resin of Garciania hanburyi. The present study was designed to evaluate the anti-metastatic effect of GA on melanoma cell lines in vitro and to explore the underlying mechanism. The anti-proliferative activity of GA on melanoma cells was assessed by CCK-8 assay. The Wound-healing, transwell, adhesion, and tube formation assays were performed to examine the inhibition of GA on the cell's migration, invasion, adhesion, and angiogenesis capacities, respectively. Enzymatic activity of MMP-2 and MMP-9 were detected by gelatin zymography assay. Protein expressions regulated by GA treatment were tested by Western blot assay. The present results showed that GA significantly inhibited the proliferation of highly metastatic melanoma A375, B16-F10 cells and human umbilical vein endothelial cells (HUVECs) in time- and doses-dependent manners. Furthermore, GA significantly inhibited the migratory, invasive and adhesive properties of A375 and B16-F10 cells, and tube-forming potential of HUVECs at sub-IC50 concentrations, where no significant cytotoxicity was observed. Mechanistically, GA treatment suppressed the EMT and angiogenesis processes and reduced the enzymatic activity of MMP-2 and MMP-9. Moreover, abnormal PI3K/Akt and ERK signaling pathways in A375 and B16-F10 cells and HUVECs were notably suppressed by GA treatment. Collectively, our results suggest that GA exerts anti-metastasis activity in melanoma cells by suppressing the EMT and angiogenesis through the PI3K/Akt and ERK signaling pathways, and might be used as a phytomedicine against metastatic melanoma.

Combination of Anti-Cancer Drugs with Molecular Chaperone Inhibitors

Most molecular chaperones belonging to heat shock protein (HSP) families are known to protect cancer cells from pathologic, environmental and pharmacological stress factors and thereby can hamper anti-cancer therapies. In this review, we present data on inhibitors of the heat shock response (particularly mediated by the chaperones HSP90, HSP70, and HSP27) either as a single treatment or in combination with currently available anti-cancer therapeutic approaches. An overview of the current literature reveals that the co-administration of chaperone inhibitors and targeting drugs results in proteotoxic stress and violates the tumor cell physiology. An optimal drug combination should simultaneously target cytoprotective mechanisms and trigger the imbalance of the tumor cell physiology.

Hsp70 inhibitors: Implications for the treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies in the world. Despite intensive advances in diagnosis and treatment of CRC, it is yet one of the leading cause of cancer related morbidity and mortality. Therefore, there is an urgent medical need for alternative therapeutic approaches to treat CRC. The 70 kDa heat shock proteins (Hsp70s) are a family of evolutionary conserved heat shock proteins, which play an important role in cell homeostasis and survival. They overexpress in various types of malignancy including CRC and are typically accompanied with poor prognosis. Hence, inhibition of Hsp70 may be considered as a striking chemotherapeutic avenue. This review summarizes the current knowledge on the progress made so far to discover compounds, which target the Hsp70 family, with particular emphasis on their efficacy in treatment of CRC. We also briefly explain the induction of Hsp70 as a strategy to prevent CRC.

HSPA8/HSC70 in Immune Disorders: A Molecular Rheostat that Adjusts Chaperone-Mediated Autophagy Substrates

HSPA8/HSC70 is a molecular chaperone involved in a wide variety of cellular processes. It plays a crucial role in protein quality control, ensuring the correct folding and re-folding of selected proteins, and controlling the elimination of abnormally-folded conformers and of proteins daily produced in excess in our cells. HSPA8 is a crucial molecular regulator of chaperone-mediated autophagy, as a detector of substrates that will be processed by this specialized autophagy pathway. In this review, we shortly summarize its structure and overall functions, dissect its implication in immune disorders, and list the known pharmacological tools that modulate its functions. We also exemplify the interest of targeting HSPA8 to regulate pathological immune dysfunctions.

Membrane heat shock protein 70: a theranostic target for cancer therapy

Members of the 70 kDa stress protein family are found in nearly all subcellular compartments of nucleated cells where they fulfil a number of chaperoning functions. Heat shock protein 70 (HSP70), also termed HSPA1A, the major stress-inducible member of this family is overexpressed in a large variety of different tumour types. Apart from its intracellular localization, a tumour-selective HSP70 membrane expression has been determined. A membrane HSP70–positive tumour phenotype is associated with aggressiveness and therapy resistance, but also serves as a recognition structure for targeted therapies. Furthermore, membrane-bound and extracellularly residing HSP70 derived from tumour cells play pivotal roles in eliciting anti-tumour immune responses. Herein, we want to shed light on the multiplicity of different activities of HSP70, depending on its intracellular, membrane and extracellular localization with the goal to use membrane HSP70 as a target for novel therapies including nanoparticle-based approaches for the treatment of cancer.

This article is part of the theme issue ‘Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective’.

Integrative analysis reveals ncRNA-mediated molecular regulatory network driving secondary hair follicle regression in cashmere goats

Background

Cashmere is a keratinized product derived from the secondary hair follicles (SHFs) of cashmere goat skins. The cashmere fiber stops growing following the transition from the actively proliferating anagen stage to the apoptosis-driven catagen stage. However, little is known regarding the molecular mechanisms responsible for the occurrence of apoptosis in SHFs, especially as pertains to the role of non-coding RNAs (ncRNAs) and their interactions with other molecules. Hair follicle (HF) degeneration is caused by localized apoptosis in the skin, while anti-apoptosis pathways may coexist in adjacent HFs. Thus, elucidating the molecular interactions responsible for apoptosis and anti-apoptosis in the skin will provide insights into HF regression.

Results

We used multiple-omics approaches to systematically identify long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and mRNAs expressed in cashmere goat skins in two crucial phases (catagen vs. anagen) of HF growth. Skin samples were collected from three cashmere goats at the anagen (September) and catagen (February) stages, and six lncRNA libraries and six miRNA libraries were constructed for further analysis. We identified 1122 known and 403 novel lncRNAs in the goat skins, 173 of which were differentially expressed between the anagen and catagen stages. We further identified 3500 gene-encoding transcripts that were differentially expressed between these two phases. We also identified 411 known miRNAs and 307 novel miRNAs, including 72 differentially expressed miRNAs. We further investigated the target genes of lncRNAs via both cis- and trans-regulation during HF growth. Our data suggest that lncRNAs and miRNAs act synergistically in the HF growth transition, and the catagen inducer factors (TGFβ1 and BDNF) were regulated by miR-873 and lnc108635596 in the lncRNA-miRNA-mRNA networks.

Conclusion

This study enriches the repertoire of ncRNAs in goats and other mammals, and contributes to a better understanding of the molecular mechanisms of ncRNAs involved in the regulation of HF growth and regression in goats and other hair-producing species.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4603-3) contains supplementary material, which is available to authorized users.

Long noncoding RNA GAS5 promotes bladder cancer cells apoptosis through inhibiting EZH2 transcription

Aberrant expression of long noncoding RNA GAS5 in bladder cancer (BC) cells was identified in recent studies. However, the regulatory functions and underlying molecular mechanisms of GAS5 in BC development remain unclear. Here, we confirmed that there was a negative correlation between GAS5 level and bladder tumor clinical stage. Functionally, overexpression of GAS5 reduced cell viability and induced cell apoptosis in T24 and EJ bladder cancer cells. Mechanistically, GAS5 effectively repressed EZH2 transcription by directly interacting with E2F4 and recruiting E2F4 to EZH2 promoter. We previously reported that miR-101 induced the apoptosis of BC cells by inhibiting the expression of EZH2. Interestingly, the present study showed that downregulation of EZH2 by GAS5 resulted in overexpression of miR-101 in T24 and EJ cells. Furthermore, the level of GAS5 was increased under the treatment of Gambogic acid (GA), a promising natural anti-cancer compound, whereas knockdown of GAS5 suppressed the inhibitory effect of GA on cell viability and abolished GA-induced apoptosis in T24 and EJ cells. Taken together, our findings demonstrated a tumor-suppressor role of GAS5 by inhibiting EZH2 on transcriptional level, and additionally provided a novel therapeutic strategy for treating human bladder cancer.

Synthesis, antitumor activity and molecular mechanism of doxorubicin conjugated trimethyl-chitosan polymeric micelle loading Beclin1 siRNA for drug-resisted bladder cancer therapy

Herein, we describe a convenient approach for the preparation of a polymeric micelle using doxorubicin (DOX) conjugated trimethyl-chitosan (TMC) with Beclin-1 siRNA (Si-Beclin1/DOX-TMC). This micelle displayed a potent capacity for autophagy inhibition and reversed drug-resistance to DOX in BIU-87/ADR cell lines. The Si-Beclin1/DOX-TMC micelle was highly cytotoxic to both drug-sensitive BIU-87 and drug-resistant BIU-87/ADR cells. Its capacity to reverse drug-resistance was dependent upon upregulation of autophagy levels in BIU-87/ADR cells. DOX was conjugated to TMC via a pH-sensitive Schiff base, which responded to the acidic lysosome microenvironment and resulted in the cytoplasmic release of DOX. The structure of DOX conjugation to the TMC polymeric micelle was characterized by NMR, GPC, TEM and DLS. DOX release profiles in different pH environment were determined by HPLC. Cellular uptake, changes to nuclei morphology and formation of autophagosomes were observed using a fluorescence microscope. Finally, in vivo antitumor activity of systemic Si-Beclin1/DOX-TMC micelle administration was evaluated in BIU-87/ADR xenograft models and Si-Beclin1/DOX-TMC micelles showed significantly suppressed tumor growth.

Herein, we describe a convenient approach for the preparation of a polymeric micelle using doxorubicin (DOX) conjugated trimethyl-chitosan (TMC) with Beclin-1 siRNA (Si-Beclin1/DOX-TMC).

1-(Benzenesulfonyl)-1,5-dihydro-4,1-benzoxazepine as a new scaffold for the design of antitumor compounds

Aim: Bozepinib is a potent and selective anticancer compound which chemical structure is made up of a benzofused seven-membered ring and a purine moiety. We previously demonstrated that the purine fragment does not exert antiproliferative effect per se. Methodology: A series of 1-(benzenesulfonyl)-4,1-benzoxazepine derivatives were synthesized in order to study the influence of the benzofused seven-membered ring in the biological activity of bozepinib by means of antiproliferative, cell cycle and apoptosis studies. Results & conclusion: Our results show that the methyleneoxy enamine sulfonyl function is essential in the antitumor activity of the structures and thus, it is a scaffold suitable for further modification with a view to obtain more potent antitumor compounds.

LncRNA SPRY4-IT1 sponges miR-101-3p to promote proliferation and metastasis of bladder cancer cells through up-regulating EZH2

Emerging evidences have indicated that long non-coding RNAs (LncRNAs) play vital roles in cancer development and progression. Previous studies have suggested that overexpression of SPRY4-IT1 predicates poor prognosis and promotes tumor progress in several cancers. However, the underlying mechanism of SPRY4-IT1 in bladder cancer remains unknown. In this study, we found that SPRY4-IT1 knockdown induced inhibition of cell proliferation, cell migration and invasion ability, and caused promotion of apoptosis in bladder cancer both in vitro and in vivo. Mechanistically, knockdown of SPRY4-IT1 increased the expression of miR-101-3p and subsequently inhibited the expression of EZH2 at posttranscriptional level. Importantly, SPRY4-IT1 could directly interact with miR-101-3p and down-regulation of miR-101-3p efficiently reversed the suppression of EZH2 induced by SPRY4-IT1 shRNA. Thus, SPRY4-IT1 positively regulated the expression of EZH2 through sponging miR-101-3p, and played an oncogenic role in bladder cancer progression. Together, our study elucidates the role of LncRNA SPRY4-IT1 as a miRNA sponge in bladder cancer, and sheds new light on LncRNA-directed diagnostics and therapeutics in bladder cancer.

[Inhibiting HSP70 expression enhances cisplatin sensitivity of cervical cancer cells]

OBJECTIVE

To investigate the relationship between sensitivity to cisplatin (DDP) and the expression of HSP70 in cervical cancer cells in vitro.

METHODS

Cervical cancer Hela229 cells treated with different concentrations of DDP and the HSP70 inhibitor (PFT-µ) were examined for cell viability using MTT assay and colony forming ability. The cell apoptosis was analyzed by flow cytometry with propidium iodide staining and DAPI staining, and JC-1 staining was used to determine mitochondrial membrane potential. The expressions of HSP70, Bcl-2, Bax and caspase-3 were measured with Western blotting. A nude mouse model bearing Hela229 cell xenograft was used to evaluate the effect of DDP and PFT-µ on tumor growth.

RESULTS

Hela229 cells expressed a higher level of HSP70 than normal cervical cells. The combined use of PFT-µ significantly enhanced the inhibitory effect of DDP (P<0.01) and increased the cell apoptosis in Hela229 cells. JC-1 staining demonstrated that DDP combined with PFT-µ more obviously reduced mitochondrial membrane potential. DDP combined with PFT-µ more strongly lowered Bcl-2 expression and increased the expressions of casepase-3 and Bax than DDP alone. In the nude mouse model, PFT-µ significantly enhanced DDP sensitivity of Hela229 cell xenografts (P<0.01).

CONCLUSIONS

Inhibition of HSP70 expression can enhance the sensitivity of cervical cancer cell to DDP both in vivo and in vitro possibly by promoting cell apoptosis, suggesting the potential of HSP70 as a new target for gene therapy of cervical cancer.