Spontaneous and Controllable Activation of Suicide Gene Expression Driven by the Stress-InducibleGrp78Promoter Resulting in Eradication of Sizable Human Tumors

Crosstalk between endoplasmic reticulum stress and multidrug-resistant cancers: hope or frustration

Endoplasmic reticulum stress (ERS) is a kind of cell response for coping with hypoxia and other stresses. Pieces of evidence show that continuous stress can promote the occurrence, development, and drug resistance of tumors through the unfolded protein response. Therefore, the abnormal ac-tivation of ERS and its downstream signaling pathways not only can regulate tumor growth and metastasis but also profoundly affect the efficacy of antitumor therapy. Therefore, revealing the molecular mechanism of ERS may be expected to solve the problem of tumor multidrug resistance (MDR) and become a novel strategy for the treatment of refractory and recurrent tumors. This re-view summarized the mechanism of ERS and tumor MDR, reviewed the relationship between ERS and tumor MDR, introduced the research status of tumor tissue and ERS, and previewed the prospect of targeting ERS to improve the therapeutic effect of tumor MDR. This article aims to provide researchers and clinicians with new ideas and inspiration for basic antitumor treatment.

Anti-breast cancer drugs targeting cell-surface glucose-regulated protein 78: a drug repositioning in silico study

Breast cancer (BC) is prevalent worldwide and is a leading cause of death among women. However, cell-surface glucose-regulated protein 78 (cs-GRP78) is overexpressed in several types of cancer and during pathogen infections. This study examines two well-known BC drugs approved by the FDA as BC treatments to GRP78. The first type consists of inhibitors of cyclin-based kinases 4/6, including abemaciclib, palbociclib, ribociclib, and dinaciclib. In addition, tunicamycin, and doxorubicin, which are among the most effective anticancer drugs for early and late-stage BC, are tested against GRP78. As (-)-epiGallocatechin gallate inhibits GRP78, it is also being evaluated (used as positive control). Thus, using molecular dynamics simulation approaches, this study aims to examine the advantages of targeting GRP78, which represents a promising cancer therapy regime. In light of recent advances in computational drug response prediction models, this study aimed to examine the benefits of GRP78 targeting, which represents a promising cancer therapy regime, by utilizing combined molecular docking and molecular dynamics simulation approaches. The simulated protein (50 ns) was docked with the drugs, then a second round of dynamics simulation was performed for 100 ns. After that, the binding free energies were calculated from 30 to 100 ns for each complex during the simulation period. These findings demonstrate the efficacy of abemaciclib, ribociclib, and tunicamycin in binding to the nucleotide-binding domain of the GRP78, paving the way for elucidating the mode of interactions between these drugs and cancer (and other stressed) cells that overexpress GRP78.Communicated by Ramaswamy H. Sarma.

Endoplasmic Reticulum Stress and Cancer: Could Unfolded Protein Response Be a Druggable Target for Cancer Therapy?

Unfolded protein response (UPR) is an adaptive response which is used for re-establishing protein homeostasis, and it is triggered by endoplasmic reticulum (ER) stress. Specific ER proteins mediate UPR activation, after dissociation from chaperone Glucose-Regulated Protein 78 (GRP78). UPR can decrease ER stress, producing an ER adaptive response, block UPR if ER homeostasis is restored, or regulate apoptosis. Some tumour types are linked to ER protein folding machinery disturbance, highlighting how UPR plays a pivotal role in cancer cells to keep malignancy and drug resistance. In this review, we focus on some molecules that have been revealed to target ER stress demonstrating as UPR could be a new target in cancer treatment.

Multifunctional TPP-PEG-biotin self-assembled nanoparticle drug delivery-based combination therapeutic approach for co-targeting of GRP78 and lysosome

Background

In this study, a multifunctional tetraphenylporphyrin (TPP) conjugated polyethylene glycol with biotin (TPP-PEG-biotin) as a photo-dynamic therapy (PDT) material encapsulating a ruthenium complex 1 (Ru-1) was fabricated as self-assembled nanoparticle (Ru-1@TPP-PEG-biotin SAN) to co-target glucose-regulated protein 78 (GRP78) and the lysosome as a new anti-cancer therapeutic strategy.

Results

The MTT assay results reveals the enhanced anticancer activity of the Ru-1@TPP-PEG-biotin SANs due to the co-targeting of the GRP78 and lysosome. The Ru-1@TPP-PEG-biotin reduced level of GRP78 and lysosomal ceramide that contributed to the stability of the lysosomal membrane. The endoplasmic reticulum (ER) stress concomitant with the inhibition of GRP78 was clearly monitored by the phosphorylation of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and inositol-requiring enzyme 1 α (IRE1α) kinases to indicate the activation of the unfolded protein response (UPR) signaling using immunofluorescence assay. On the other hand, the degradation of the lysosome was observed through PDT action by the Ru-1@TPP-PEG-biotin SAN treatment. This was confirmed by the co-localization assay showing the disappearance of cathepsin D and lysosomal-associated membrane protein 1 (LAMP1) in the lysosome.

Conclusions

Considering lysosome-mediated autophagy is an effective cancer cell survival mechanism, the degradation of the lysosome along with GRP78 inhibition by the Ru-1@TPP-PEG-biotin SAN combination therapy is suggested as a new co-targeting cancer treatment.

Targeted Inhibitory Effect of Nasopharyngeal Carcinoma Cells by Hre2.Grp78 Chimeric Promoter Regulating Fusion Gene TK/VP3

Objective:

To construct plasmids with Hre₂.Grp78 chimeric promoter regulating fusion gene TK/VP3 and elaborate the effects of overexpressed TK/VP3 on nasopharyngeal carcinoma cells.

Methods:

Four plasmids were constructed, including pcDNA3.1-CMV-TK/VP3, pcDNA3.1-Hre₂.TK/VP3, pcDNA3.1-Grp78.TK/VP3, and pcDNA3.1-Hre₂.Grp78.TK/VP3. The human nasopharyngeal carcinoma cell line HNE1 cells were transfected with the 4 plasmids, respectively. Cell viabilities were evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and apoptosis was conducted using flow cytometry analysis. The expression of TK, VP3, Grp78, and hypoxia-inducible factor 1α and apoptosis-related proteins was determined by real-time quantitative polymerase chain reaction and Western blotting.

Results:

The recombinant plasmids that could steadily overexpress TK and VP3 were successfully constructed. Expression of TK and VP3 in cells transfected with pcDNA3.1-Hre₂.TK/VP3 and pcDNA3.1-Grp78.TK/VP3 was significantly higher than pcDNA3.1-CMV-TK/VP3, and expression in cells transfected with pcDNA3.1-Hre₂.Grp78.TK/VP3 was the highest. Under glucose deprivation or hypoxia condition, Grp78 or hypoxia-inducible factor 1α was overexpressed so that expression of TK and VP3 was significantly upregulated, which could further inhibit cell proliferation and enhance cell apoptosis.

Conclusion:

We successfully constructed 4 plasmids with Hre₂.Grp78 chimeric promoter regulating fusion gene TK/VP3, which could significantly inhibit the proliferation as well as enhance the apoptosis of nasopharyngeal carcinoma cells under glucose deprivation or hypoxia condition.

Efficacy of systemic temozolomide-activated phage-targeted gene therapy in human glioblastoma

Glioblastoma multiforme (GBM) is the most lethal primary intracranial malignant neoplasm in adults and most resistant to treatment. Integration of gene therapy and chemotherapy, chemovirotherapy, has the potential to improve treatment. We have introduced an intravenous bacteriophage (phage) vector for dual targeting of therapeutic genes to glioblastoma. It is a hybrid AAV/phage, AAVP, designed to deliver a recombinant adeno-associated virus genome (rAAV) by the capsid of M13 phage. In this vector, dual tumor targeting is first achieved by phage capsid display of the RGD4C ligand that binds the αvβ3 integrin receptor. Second, genes are expressed from a tumor-activated and temozolomide (TMZ)-induced promoter of the glucose-regulated protein, Grp78 Here, we investigated systemic combination therapy using TMZ and targeted suicide gene therapy by the RGD4C/AAVP-Grp78 Firstly, in vitro we showed that TMZ increases endogenous Grp78 gene expression and boosts transgene expression from the RGD4C/AAVP-Grp78 in human GBM cells. Next, RGD4C/AAVP-Grp78 targets intracranial tumors in mice following intravenous administration. Finally, combination of TMZ and RGD4C/AAVP-Grp78 targeted gene therapy exerts a synergistic effect to suppress growth of orthotopic glioblastoma.

Myocardial Infarction-Related Transcripts (MIAT) Participate in Diabetic Optic Nerve Injury by Regulating Heart Shock Protein 5 (HSPA5) via Competitively Binding to MicroRNA-379

Background

The aim of this study was to explore the role of MIAT (myocardial infarction related transcripts) in diabetic optic neuropathy and its underlying mechanism.

Material/Methods

QRT-PCR (quantitative real-time polymerase chain reaction) was performed to detect the mRNA levels of MIAT and HSPA5 (heart shock protein 5) in diabetic rat model and high-glucose cultured Müller cells. After the intracellular MIAT level was increased by lentivirus transfection, the proliferation, cell cycle, and apoptosis of Müller cells were measured using the CCK-8 (Cell Counting Kit-8) assay, flow cytometry, and TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling) assay, respectively. Mechanisms underlying the MIAT-related apoptosis were explored by Western blot analysis. The binding condition of microRNA-379 to MIAT and HSPA5 was confirmed by luciferase reporter gene assay.

Results

Both MIAT and HSPA5 levels were remarkably increased in high-glucose cultured Müller cells. After transfected with LV (lentivirus)-MIAT, Müller cells showed a decreased proliferation and an enhanced apoptosis with the increased expressions of pro-apoptotic proteins. However, no remarkable changes were observed in cell cycle. Further mechanistic studies found that MIAT regulated HSPA5 expression by directly binding to microRNA-379.

Conclusions

MIAT was overexpressed in the diabetic optic nerve. MIAT overexpression remarkably promoted the apoptosis of Müller cells by adsorbing microRNA-379 and thus regulating HSPA5, which was a direct target of microRNA-379.

MicroRNA-495-3p inhibits multidrug resistance by modulating autophagy through GRP78/mTOR axis in gastric cancer

Multidrug resistance (MDR) accounts for poor prognosis in gastric cancer (GC). MicroRNAs (miRNAs) are critical regulators of MDR via modulation of the target genes. The present study revealed that miR-495-3p could act via a target gene, GRP78, to regulate the process of autophagy and inhibit MDR. Based on the in vitro and in vivo gain-of-function or loss-of-function experiments, overexpression of miR-495-3p was sufficient to reverse the MDR to four chemotherapeutics in vitro and inhibit the tumor growth in vivo. Moreover, GRP78 was positively associated with the occurrence of autophagy. Thus, reducing the expression of GRP78 by siRNA resulted in autophagy-suppressive activity similar to that of miR-495-3p on mammalian target of rapamycin (mTOR) and its substrates activation and autophagy inhibition, while restoring GRP78 attenuated the anti-autophagy effects caused by miR-495-3p. Clinically, either miR-495-3p downregulation or GRP78 upregulation was associated with malignant phenotypes in patients with GC. In conclusion, these findings demonstrate that miR-495-3p is an important regulator of autophagy balance and MDR by modulating the GRP78/mTOR axis. In addition, miR-495-3p and GRP78 could be used as prognostic factors for overall survival in GC, which implicates miR-495-3p as a therapeutic target in cancer.

Endoplasmic reticulum chaperone glucose-regulated protein 78 in gastric cancer: An emerging biomarker

The endoplasmic reticulum (ER) is the principal organelle responsible for the synthesis, initial post-translational modification, folding, export and secretion of proteins. It is also responsible for the maintenance of cellular homeostasis. In response to cellular stress conditions including glucose deprivation, hypoxia and changes in calcium homeostasis, ER stress machinery is activated and triggers the unfolded protein response, resulting in the restoration of homeostasis or activation of cell death. Glucose-regulated protein 78 (GRP78), a molecular chaperone, may be induced by ER stress at the transcriptional and translational level. A number of studies have demonstrated that GRP78 serves an important role in tumor cell proliferation, metastasis, angiogenesis and drug-resistance. The present review systematically describes the association between GRP78 expression and gastric cancer pathogenesis, and emphasizes that GRP78 is a novel diagnostic and therapeutic biomarker of gastric cancer.

HSPA5 negatively regulates lysosomal activity through ubiquitination of MUL1 in head and neck cancer

HSPA5/GRP78/BiP plays an important role in cell survival or tumor progression. For these reasons, HSPA5 is an emerging therapeutic target in cancer development. Here we report that HSPA5 contributes to head and neck cancer (HNC) survival via maintenance of lysosomal activity; however, a nonthermal plasma (NTP, considered as a next-generation cancer therapy)-treated solution (NTS) inhibits HNC progression through HSPA5-dependent alteration of lysosomal activity. HSPA5 prevents NTS-induced lysosome inhibition through lysosomal-related proteins or regulation of gene expression. However, NTS-induced MUL1/MULAN/GIDE/MAPL (mitochondrial ubiquitin ligase activator of NFKB 1) leads to downregulation of HSPA5 via K48-linked ubiquitination at the lysine 446 (K446) residue. MUL1 knockdown hinders NTS-induced lysosome inhibition or cytotoxicity through the reduction of HSPA5 ubiquitination in HNC cells. While MUL1 was suppressed, HSPA5 was overexpressed in tissues of HNC patients. NTS strongly inhibited HNC progression via alterations of expression of MUL1 and HSPA5, in vivo in a xenograft model. However, NTS did not induce inhibition of tumor progression or HSPA5 reduction in MUL1 knockout (KO) HNC cells which were generated by CRISPR/Cas9 system. The data provide compelling evidence to support the idea that the regulation of the MUL1-HSPA5 axis can be a novel strategy for the treatment of HNC.

Thinking Outside the Box

A broad definition of preconditioning is "the preparation for a subsequent action." Mounting evidence demonstrates that novel remote preconditioning paradigms, in which protective stimuli experienced locally can capacitate systemic tolerance and enhanced cell viability upon exposure to ensuing cellular insults, have been largely successful in the field of cardiovascular ischemia/reperfusion injury. To ensure successful protective preconditioning, some models (including the uterus) have been demonstrated to activate the unfolded protein response (UPR), which is a cellular stress response controlled at the level of the endoplasmic reticulum. However, in the context of remote preconditioning, activation of these intracellular molecular pathways must result in the extracellular transmission of adaptive signals to remote targets. In our recently published manuscript, we have described the activation of the UPR in the pregnant uterine myocyte to be associated with increased uterine myocyte quiescence and normal gestational length. We hypothesize that ubiquitous uterine gestational stresses experienced in every pregnancy, which have been demonstrated in other systems to activate the UPR, may induce a robust paracrine dissemination of a uterine secretome, for example, glucose-regulated protein 78, with preconditioning-like properties. Furthermore, we speculate that the gestational stress-induced uterine secretome acts to promote both local and systemic tolerance to the ensuing gestational insults, allowing for the maintenance of uterine quiescence. In this context, preterm labor may be the result of a pregnant uterus experiencing a stress it cannot accommodate or when it is unable to host an appropriate UPR resulting in insufficient preconditioning and a diminished local and systemic capacity to tolerate pregnancy-dependent increases in normal gestational stress. This is highly attractive from a clinical viewpoint as we ultimately aim to identify local and systemic adaptations that may serve as preconditioning stimuli for use as a strategy to restore appropriate preconditioning profiles to prolong uterine quiescence in pregnancy.

Towards a transcriptome-based theranostic platform for unfavorable breast cancer phenotypes

Inflammatory breast carcinoma (IBC) is one of the most lethal forms of human breast cancer, and effective treatment for IBC is an unmet clinical need in contemporary oncology. Tumor-targeted theranostic approaches are emerging in precision medicine, but only a few specific biomarkers are available. Here we report up-regulation of the 78-kDa glucose-regulated protein (GRP78) in two independent discovery and validation sets of specimens derived from IBC patients, suggesting translational promise for clinical applications. We show that a GRP78-binding motif displayed on either bacteriophage or adeno-associated virus/phage (AAVP) particles or loop-grafted onto a human antibody fragment specifically targets orthotopic IBC and other aggressive breast cancer models in vivo. To evaluate the theranostic value, we used GRP78-targeting AAVP particles to deliver the human Herpes simplex virus thymidine kinase type-1 (HSVtk) transgene, obtaining simultaneous in vivo diagnosis through PET imaging and tumor treatment by selective activation of the prodrug ganciclovir at tumor sites. Translation of this AAVP system is expected simultaneously to image, monitor, and treat the IBC phenotype and possibly other aggressive (e.g., invasive and/or metastatic) subtypes of breast cancer, based on the inducible cell-surface expression of the stress-response chaperone GRP78, and possibily other cell-surface receptors in human tumors.

Melanoma and the Unfolded Protein Response

The UPR (unfolded protein response) has been identified as a key factor in the progression and metastasis of cancers, notably melanoma. Several mediators of the UPR are upregulated in cancers, e.g., high levels of GRP78 (glucose-regulator protein 78 kDa) correlate with progression and poor outcome in melanoma patients. The proliferative burden of cancer induces stress and activates several cellular stress responses. The UPR is a tightly orchestrated stress response that is activated upon the accumulation of unfolded proteins within the ER (endoplasmic reticulum). The UPR is designed to mediate two conflicting outcomtes, recovery and apoptosis. As a result, the UPR initiates a widespread signaling cascade to return the cell to homeostasis and failing to achieve cellular recovery, initiates UPR-induced apoptosis. There is evidence that ER stress and subsequently the UPR promote tumourigenesis and metastasis. The complete role of the UPR has yet to be defined. Understanding how the UPR allows for adaption to stress and thereby assists in cancer progression is important in defining an archetype of melanoma pathology. In addition, elucidation of the mechanisms of the UPR may lead to development of effective treatments of metastatic melanoma.

Identification of markers that functionally define a quiescent multiple myeloma cell sub-population surviving bortezomib treatment

Background

The mechanisms allowing residual multiple myeloma (MM) cells to persist after bortezomib (Bz) treatment remain unclear. We hypothesized that studying the biology of bortezomib-surviving cells may reveal markers to identify these cells and survival signals to target and kill residual MM cells.

Methods

We used H2B-GFP label retention, biochemical tools and in vitro and in vivo experiments to characterize growth arrest and the unfolded protein responses in quiescent Bz-surviving cells. We also tested the effect of a demethylating agent, 5-Azacytidine, on Bz-induced quiescence and whether inhibiting the chaperone GRP78/BiP (henceforth GRP78) with a specific toxin induced apoptosis in Bz-surviving cells. Finally, we used MM patient samples to test whether GRP78 levels might associate with disease progression. Statistical analysis employed t-test and Mann-Whitney tests at a 95% confidence.

Results

We report that Bz-surviving MM cells in vitro and in vivo enter quiescence characterized by p21^CIP1 upregulation. Bz-surviving MM cells also downregulated CDK6, Ki67 and P-Rb. H2B-GFP label retention showed that Bz-surviving MM cells are either slow-cycling or deeply quiescent. The Bz-induced quiescence was stabilized by low dose (500nM) of 5-azacytidine (Aza) pre-treatment, which also potentiated the initial Bz-induced apoptosis. We also found that expression of GRP78, an unfolded protein response (UPR) survival factor, persisted in MM quiescent cells. Importantly, GRP78 downregulation using a specific SubAB bacterial toxin killed Bz-surviving MM cells. Finally, quantification of Grp78^high/CD138+ MM cells from patients suggested that high levels correlated with progressive disease.

Conclusions

We conclude that Bz-surviving MM cells display a GRP78^HIGH/p21^HIGH/CDK6^LOW/P-Rb^LOW profile, and these markers may identify quiescent MM cells capable of fueling recurrences. We further conclude that Aza + Bz treatment of MM may represent a novel strategy to delay recurrences by enhancing Bz-induced apoptosis and quiescence stability.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1460-1) contains supplementary material, which is available to authorized users.

Small-Animal PET Imaging of Pancreatic Cancer Xenografts Using a 64Cu-Labeled Monoclonal Antibody, MAb159

Overexpression of the GRP78 receptor on cell surfaces has been linked with tumor growth, metastasis, and resistance to therapy. We developed a (64)Cu-labeled probe for PET imaging of tumor GRP78 expression based on a novel anti-GRP78 monoclonal antibody, MAb159.

METHODS

MAb159 was conjugated with the (64)Cu-chelator DOTA through lysines on the antibody. DOTA-human IgG was also prepared as a control that did not bind to GRP78. The resulting PET probes were evaluated in BXPC3 pancreatic cancer xenografts in athymic nude mice.

RESULTS

The radiotracer was synthesized with a specific activity of 0.8 MBq/μg of antibody. In BXPC3 xenografts, (64)Cu-DOTA-MAb159 demonstrated prominent tumor accumulation (4.3 ± 1.2, 15.4 ± 2.6, and 18.3 ± 1.0 percentage injected dose per gram at 1, 17, and 48 after injection, respectively). In contrast, (64)Cu-DOTA-human IgG had low BXPC3 tumor accumulation (4.8 ± 0.5, 7.5 ± 0.7, and 4.6 ± 0.8 percentage injected dose per gram at 1, 17, and 48 h after injection, respectively).

CONCLUSION

We demonstrated that GRP78 can serve as a valid target for pancreatic cancer imaging. The success of this approach will be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-GRP78 treatment. Moreover, these newly developed probes may have important applications in other types of cancer overexpressing GRP78.

Expression and significance of glucose-regulated protein 78 in human osteosarcoma

The present study aimed to investigate the expression of glucose-regulated protein 78 (GRP78) in osteosarcoma cells, and analyze the differences in expression between tumor and normal tissues, pre- and post-chemotherapy patients and metastatic and non-metastatic tumors. According to these results, the associations between the expression of GRP78 and tumor growth, metastasis and chemotherapeutics could be determined. Between 2007 and 2012, 60 patients who had been diagnosed with osteosarcoma were selected for the present study. Of these patients, 20 presented with non-metastatic tumors and 40 with metastatic tumors, and 20 had been treated without chemotherapy and 40 with chemotherapy. In addition, 60 specimens obtained from adjacent normal tissues were collected for the control groups. Immunofluorescence staining was used to examine the expression of GRP78 in the different tissues. The total RNA and protein were extracted from crushed tissues and used in the reverse transcription polymerase chain reaction and western blot analysis. GRP78 was primarily located in the intracavity of the endoplasmic reticulum. The expression level of GRP78 in the tumor tissue was higher than that in the normal tissue surrounding the tumor (P<0.01). In addition, the level was higher in the metastatic tumors compared with the non-metastatic tumors (P<0.05), and in the non-chemotherapy-treated patients compared with the chemotherapy-treated patients (P<0.01). The expression level of GRP78 mRNA in the tumor tissue was higher than that in the normal tissue (P<0.01). Furthermore, the level was higher in the metastasis group than in the non-metastasis group (P<0.05), and in the non-chemotherapy group than in the chemotherapy group (P<0.01). The expression level of GRP78 protein was higher in the tumor tissue compared with the normal tissue (P<0.01), in the metastasis group compared with the non-metastasis group (P<0.05), and in the non-chemotherapy group compared with the chemotherapy group (P<0.01). In conclusion, the present study detected the expression of GRP78 in patients with osteosarcoma and revealed a higher expression level in the tumor tissues compared with the normal tissues around the tumor, in the metastasis group compared with the non-metastasis group and in the non-chemotherapy-treated group compared with the chemotherapy-treated group.

Systemic gene transfer of binding immunoglobulin protein (BiP) prevents disease progression in murine collagen-induced arthritis

Summary Recombinant human binding immunoglobulin protein (BiP) has previously demonstrated anti-inflammatory properties in multiple models of inflammatory arthritis. We investigated whether these immunoregulatory properties could be exploited using gene therapy techniques. A single intraperitoneal injection of lentiviral vector containing the murine BiP (Lenti-mBiP) or green fluorescent protein (Lenti-GFP) transgene was administered in low- or high-dose studies during early arthritis. Disease activity was assessed by visual scoring, histology, serum cytokine and antibody production measured by cell enzyme-linked immunosorbent assay (ELISA) and ELISA, respectively. Lentiviral vector treatment caused significant induction of interferon (IFN)-γ responses regardless of the transgene; however, further specific effects were directly attributable to the BiP transgene. In both studies Lenti-mBiP suppressed clinical arthritis significantly. Histological examination showed that low-dose Lenti-mBiP suppressed inflammatory cell infiltration, cartilage destruction and significantly reduced pathogenic anti-type II collagen (CII) antibodies. Lenti-mBiP treatment caused significant up-regulation of soluble cytotoxic T lymphocyte antigen-4 (sCTLA-4) serum levels and down-regulation of interleukin (IL)-17A production in response to CII cell restimulation. In-vitro studies confirmed that Lenti-mBiP spleen cells could significantly suppress the release of IL-17A from CII primed responder cells following CII restimulation in vitro, and this suppression was associated with increased IL-10 production. Neutralization of CTLA-4 in further co-culture experiments demonstrated inverse regulation of IL-17A production. In conclusion, these data demonstrate proof of principle for the therapeutic potential of systemic lentiviral vector delivery of the BiP transgene leading to immunoregulation of arthritis by induction of soluble CTLA-4 and suppression of IL-17A production.

Bacteriophage-derived vectors for targeted cancer gene therapy

Cancer gene therapy expanded and reached its pinnacle in research in the last decade. Both viral and non-viral vectors have entered clinical trials, and significant successes have been achieved. However, a systemic administration of a vector, illustrating safe, efficient, and targeted gene delivery to solid tumors has proven to be a major challenge. In this review, we summarize the current progress and challenges in the targeted gene therapy of cancer. Moreover, we highlight the recent developments of bacteriophage-derived vectors and their contributions in targeting cancer with therapeutic genes following systemic administration.

The unfolded protein response as a target for cancer therapy

Various physiological and pathological conditions generate an accumulation of misfolded proteins in the endoplasmic reticulum (ER). This results in ER stress followed by a cellular response to cope with this stress and restore homeostasis: the unfolded protein response (UPR). Overall, the UPR leads to general translational arrest and the induction of specific factors to ensure cell survival or to mediate cell death if the stress is too severe. In multiple cancers, components of the UPR are overexpressed, indicating increased dependence on the UPR. In addition, the UPR can confer resistance to anti-cancer treatment. Therefore, modification of the UPR should be explored for its anti-cancer properties. This review discusses factors associated with the UPR that represent potential therapeutic targets.

Reversed expression of GRIM-1 and GRP78 in human non-small cell lung cancer

Gene associated with retinoid and interferon-induced mortality 1 (GRIM-1) acts as a tumor growth suppressor via apoptosis induction. However, GRIM-1 expression in human non-small cell lung cancer (NSCLC) and its potential interaction with another apoptosis-associated protein-glucose-regulated protein 78 (GRP78)-are as yet unknown. Using 40 surgical specimens, we showed significantly lower expression of GRIM-1 in NSCLC at both protein and messenger RNA (mRNA) levels compared with that in normal tissues (P < .01 and P < .001, respectively). Interestingly, these tumors tended to express higher basal amounts of GRP78 protein and mRNA (P < .05 and P < .001, respectively). Similarly, in the NSCLC tissues, weaker staining for GRIM-1 (main intensity + to ++) but stronger staining for GRP78 (main intensity +++ to ++++) was observed. Correlation analysis showed that protein and mRNA expression or the percentage of cells immunoreactive for GRIM-1 was negatively correlated with that of GRP78 (r = -0.279, r = -0.326, or r = -0.571, respectively). Coimmunoprecipitation and transient transfection revealed that GRIM-1 interacted with GRP78 and suppressed GRP78 protein expression. In addition, there was no correlation between GRIM-1 expression and clinical characteristics, whereas GRP78 expression was significantly correlated with tumor-nodes-metastasis (TNM) stage (stage 3 + 4 versus stage 1 + 2). In conclusion, the expression of GRIM-1 and GRP78 was negatively correlated in human NSCLC tissues, and the down-regulation of GRP78 by GRIM-1 provides a possible mechanism for their interaction. This study suggests a novel potential molecular pathway inactivated during the development of NSCLC.

Glucose-regulated proteins in cancer: molecular mechanisms and therapeutic potential

The glucose-regulated proteins (GRPs) are stress-inducible chaperones that mostly reside in the endoplasmic reticulum or the mitochondria. Recent advances show that the GRPs have functions that are distinct from those of the related heat shock proteins, and they can be actively translocated to other cellular locations and assume novel functions that control signalling, proliferation, invasion, apoptosis, inflammation and immunity. Mouse models further identified their specific roles in development, tumorigenesis, metastasis and angiogenesis. This Review describes their discovery and regulation, as well as their biological functions in cancer. Promising agents that use or target the GRPs are being developed, and their efficacy as anticancer therapeutics is also discussed.

A cyclic HSV1-TK reporter for real-time PET imaging of apoptosis

The coordination of cell proliferation and programmed death (apoptosis) is essential for normal physiology, and imbalance in these two opposing processes is implicated in various diseases. Objective and quantitative noninvasive imaging of apoptosis would significantly facilitate rapid screening as well as validation of therapeutic chemicals. Herein, we molecularly engineered an apoptosis switch-on PET-based cyclic herpes simplex virus type 1-thymidine kinase reporter (cTK266) containing a caspase-3 recognition domain as the switch. Translation of the reporter and protein splicing in healthy mammalian cells produce an inactive cyclic chimera. Upon apoptosis, caspase-3-specific cleavage of the circular product occurs, resulting in the restoration of the thymidine kinase activity, which can be detected in living cells and animals by noninvasive PET imaging. Our results showed the high sensitivity of this reporter in dynamic and quantitative imaging of apoptosis in living subjects. This reporter could be applied as a valuable tool for high-throughput functional screening of proapoptotic and antiapoptotic compounds in preclinical models in drug development, and monitoring the destination of therapeutic cells in clinical settings.

Recent advances in the management of osteosarcoma and forthcoming therapeutic strategies

Osteosarcoma is the most frequent primary bone tumor and occurs mainly in young patients (average age: 18 years). No evolution of the survival rates has been recorded for two decades in response to current treatment, associating often toxic and badly tolerated cures of chemotherapy (given a significant rate of bad responders) with preserving surgery. Among the proposed innovative strategies, immune-based therapy, antiangiogenesis agents, tumor-suppressor or suicide gene therapy, or anticancer drugs not commonly used in osteosarcoma are presented. A further strategy is to target the tumor microenvironment rather than the tumor itself.

Inhibition of histone deacetylation and DNA methylation improves gene expression mediated by the adeno-associated virus/phage in cancer cells

Bacteriophage (phage), viruses that infect bacteria only, have become promising vectors for targeted systemic delivery of genes to cancer, although, with poor efficiency. We previously designed an improved phage vector by incorporating cis genetic elements of adeno-associated virus (AAV). This novel AAV/phage hybrid (AAVP) specifically targeted systemic delivery of therapeutic genes into tumors. To advance the AAVP vector, we recently introduced the stress-inducible Grp78 tumor specific promoter and found that this dual tumor-targeted AAVP provides persistent gene expression, over time, in cancer cells compared to silenced gene expression from the CMV promoter in the parental AAVP. Herein, we investigated the effect of histone deacetylation and DNA methylation on AAVP-mediated gene expression in cancer cells and explored the effect of cell confluence state on AAVP gene expression efficacy. Using a combination of AAVP expressing the GFP reporter gene, flow cytometry, inhibitors of histone deacetylation, and DNA methylation, we have demonstrated that histone deacetylation and DNA methylation are associated with silencing of gene expression from the CMV promoter in the parental AAVP. Importantly, inhibitors of histone deacetylases boost gene expression in cancer cells from the Grp78 promoter in the dual tumor-targeted AAVP. However, cell confluence had no effect on AAVP-guided gene expression. Our findings prove that combination of histone deacetylase inhibitor drugs with the Grp78 promoter is an effective approach to improve AAVP-mediated gene expression in cancer cells and should be considered for AAVP-based clinical cancer gene therapy.

Cancer stem cell hypothesis: a brief summary and two proposals

The investigation and development of the cancer stem cell (CSC) model has received much focus during these years. CSC is characterized as a small fraction of cancer cells that have an indefinite ability for self-renewal and pluripotency and are responsible for initiating and sustaining of the bulk of cancer. So, whether current treatment strategies, most of which target the rapid division of cancer cells, could interfere with the slow-cycling CSCs is broadly questioned. Meanwhile, however, the new understanding of tumorigenesis has led to the development of new drug screening strategies. Both stem cells and mesenchymal stem cells have been vigorously used in pre-clinical studies of their anti-tumor potential, mainly due to their inherent tumoritropic migratory properties and their ability to carry anti-tumor transgenes. Here, based on the tumorigenic and tumoritropic characteristics of CSCs, we proposed two hypotheses exploring possible usage of CSCs as novel anti-tumor agents and potential sources for tissue regeneration. Further experimental validation of these hypotheses may unravel some new research topics.

Cancer stem cell hypothesis: a brief summary and two proposals

The investigation and development of the cancer stem cell (CSC) model has received much focus during these years. CSC is characterized as a small fraction of cancer cells that have an indefinite ability for self-renewal and pluripotency and are responsible for initiating and sustaining of the bulk of cancer. So, whether current treatment strategies, most of which target the rapid division of cancer cells, could interfere with the slow-cycling CSCs is broadly questioned. Meanwhile, however, the new understanding of tumorigenesis has led to the development of new drug screening strategies. Both stem cells and mesenchymal stem cells have been vigorously used in pre-clinical studies of their anti-tumor potential, mainly due to their inherent tumoritropic migratory properties and their ability to carry anti-tumor transgenes. Here, based on the tumorigenic and tumoritropic characteristics of CSCs, we proposed two hypotheses exploring possible usage of CSCs as novel anti-tumor agents and potential sources for tissue regeneration. Further experimental validation of these hypotheses may unravel some new research topics.

Dual systemic tumor targeting with ligand-directed phage and Grp78 promoter induces tumor regression

The tumor-specific Grp78 promoter is overexpressed in aggressive tumors. Cancer patients would benefit greatly from application of this promoter in gene therapy and molecular imaging; however, clinical benefit is limited by lack of strategies to target the systemic delivery of Grp78-driven transgenes to tumors. This study aims to assess the systemic efficacy of Grp78-guided expression of therapeutic and imaging transgenes relative to the standard cytomegalovirus (CMV) promoter. Combination of ligand and Grp78 transcriptional targeting into a single vector would facilitate systemic applications of the Grp78 promoter. We generated a dual tumor-targeted phage containing the arginine-glycine-aspartic acid tumor homing ligand and Grp78 promoter. Next, we combined flow cytometry, Western blot analysis, bioluminescence imaging of luciferase, and HSVtk/ganciclovir gene therapy and compared efficacy to conventional phage carrying the CMV promoter in vitro and in vivo in subcutaneous models of rat and human glioblastoma. We show that double-targeted phage provides persistent transgene expression in vitro and in tumors in vivo after systemic administration compared with conventional phage. Next, we showed significant tumor killing in vivo using the HSVtk/ganciclovir gene therapy and found a systemic antitumor effect of Grp78-driven HSVtk against therapy-resistant tumors. Finally, we uncovered a novel mechanism of Grp78 promoter activation whereby HSVtk/ganciclovir therapy upregulates Grp78 and transgene expression via the conserved unfolded protein response signaling cascade. These data validate the potential of Grp78 promoter in systemic cancer gene therapy and report the efficacy of a dual tumor targeting phage that may prove useful for translation into gene therapy and molecular imaging applications.

Unique diagnostic and therapeutic roles of porphyrins and phthalocyanines in photodynamic therapy, imaging and theranostics

Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

Cripto/GRP78 modulation of the TGF-β pathway in development and oncogenesis

Cripto is a small, GPI-anchored signaling protein that regulates cellular survival, proliferation, differentiation and migration during normal developmental processes and tumorigenesis. Cripto functions as an obligatory co-receptor for the TGF-β ligands Nodal, GDF1 and GDF3 but attenuates signaling of others such as activin-A, activin-B and TGF-β1. Soluble, secreted forms of Cripto also activate Src, ras/raf/MAPK and PI3K/Akt pathways via a mechanism that remains largely obscure. This review describes the biological roles and signaling mechanisms of Cripto, highlighting our identification of the 78 kDa glucose regulated protein (GRP78) as a cell surface receptor/co-factor required for Cripto signaling via both TGF-β and Src/MAPK/PI3K pathways. We discuss emerging evidence indicating that Cripto/GRP78 signaling regulates normal somatic stem cells and their tumorigenic counterparts.

The critical roles of endoplasmic reticulum chaperones and unfolded protein response in tumorigenesis and anticancer therapies

Cancer progression is characterized by rapidly proliferating cancer cells that are in need of increased protein synthesis. Therefore, enhanced endoplasmic reticulum (ER) activity is required to facilitate the folding, assembly and transportation of membrane and secretory proteins. These functions are carried out by ER chaperones. It is now becoming clear that the ER chaperones have critical functions outside of simply facilitating protein folding. For example, cancer progression requires glucose regulated protein (GRP) 78 for cancer cell survival and proliferation, as well as angiogenesis in the microenvironment. GRP78 can translocate to the cell surface acting as a receptor regulating oncogenic signaling and cell viability. Calreticulin, another ER chaperone, can translocate to the cell surface of apoptotic cancer cells and induce immunogenic cancer cell death and antitumor responses in vivo. Tumor-secreted GRP94 has been shown to elicit antitumor immune responses when used as antitumor vaccines. Protein disulfide isomerase is another ER chaperone that demonstrates pro-oncogenic and pro-survival functions. Because of intrinsic alterations of cellular metabolism and extrinsic factors in the tumor microenvironment, cancer cells are under ER stress, and they respond to this stress by activating the unfolded protein response (UPR). Depending on the severity and duration of ER stress, the signaling branches of the UPR can activate adaptive and pro-survival signals, or induce apoptotic cell death. The protein kinase RNA-like ER kinase signaling branch of the UPR has a dual role in cancer proliferation and survival, and is also required for ER stress-induced autophagy. The activation of the inositol-requiring kinase 1α branch promotes tumorigenesis, cancer cell survival and regulates tumor invasion. In summary, perturbance of ER homeostasis has critical roles in tumorigenesis, and therapeutic modulation of ER chaperones and/or UPR components presents potential antitumor treatments.

Molecular imaging with activatable reporter systems

Molecular imaging is a newly emerged multiple disciplinary field that aims to visualize, characterize and quantitatively measure biological processes at cellular and molecular levels in humans and other living systems. A reporter gene is a piece of DNA encoding reporter protein, which presents as a readily measurable phenotype that can be distinguished easily from the background of endogenous protein. After being transferred into cells of organ systems (transgenes), the reporter gene can be utilized to visualize transcriptional and posttranscriptional regulation of gene expression, protein-protein interactions, or trafficking of proteins or cells in living subjects. Herein, we review previous classification of reporter genes and regroup the reporter gene based imaging as basic, inducible and activatable, based on the regulation of reporter gene transcription and post-translational modification of reporter proteins. We then focus on activatable reporters, in which the signal can be activated at the posttranslational level for visualizing protein-protein interactions, protein phosphorylation or tertiary structure changes. The applications of several types of activatable reporters will also be summarized. We conclude that activatable reporter imaging can benefit both basic biomedical research and drug development.

GRP78 Protein Expression in Ovarian Cancer Patients and Perspectives for a Drug-Targeting Approach

Glucose-regulated protein of 78 kD (GRP78) is a chaperone protein mainly located in the endoplasmic reticulum (ER). This protein is normally present at low levels in adult cells but its expression is triggered by ER stress including glucose deprivation and hypoxia. In tumor cells, it is overexpressed with fraction of protein found at the cell surface. This paper presents the physiology of GRP78 in the context of ovarian cancer and its potential use as drug delivery systems targeting ovarian cancer cell.

Glucose regulated protein 78: a critical link between tumor microenvironment and cancer hallmarks

Glucose regulated protein 78 (GRP78) has long been recognized as a molecular chaperone in the endoplasmic reticulum (ER) and can be induced by the ER stress response. Besides its location in the ER, GRP78 has been found to be present in cell plasma membrane, cytoplasm, mitochondria, nucleus as well as cellular secretions. GRP78 is implicated in tumor cell proliferation, apoptosis resistance, immune escape, metastasis and angiogenesis, and its elevated expression usually correlates with a variety of tumor microenvironmental stresses, including hypoxia, glucose deprivation, lactic acidosis and inflammatory response. GRP78 protein acts as a centrally located sensor of stress, which feels and adapts to the alteration in the tumor microenvironment. This article reviews the potential contributions of GRP78 to the acquisition of cancer hallmarks based on intervening in stress responses caused by tumor niche alterations. The paper also introduces several potential GRP78 relevant targeted therapies.

Inositol 1,4,5-trisphosphate receptor 1 mutation perturbs glucose homeostasis and enhances susceptibility to diet-induced diabetes

The inositol 1,4,5-trisphosphate receptors (IP3Rs) as ligand-gated Ca(2)(+) channels are key modulators of cellular processes. Despite advances in understanding their critical role in regulating neuronal function and cell death, how this family of proteins impact cell metabolism is just emerging. Unexpectedly, a transgenic mouse line (D2D) exhibited progressive glucose intolerance as a result of transgene insertion. Inverse PCR was used to identify the gene disruption in the D2D mice. This led to the discovery that Itpr1 is among the ten loci disrupted in chromosome 6. Itpr1 encodes for IP3R1, the most abundant IP3R isoform in mouse brain and also highly expressed in pancreatic β-cells. To study IP3R1 function in glucose metabolism, we used the Itpr1 heterozygous mutant mice, opt/+. Glucose homeostasis in male mice cohorts was examined by multiple approaches of metabolic phenotyping. Under regular diet, the opt/+ mice developed glucose intolerance but no insulin resistance. Decrease in second-phase glucose-stimulated blood insulin level was observed in opt/+ mice, accompanied by reduced β-cell mass and insulin content. Strikingly, when fed with high-fat diet, the opt/+ mice were more susceptible to the development of hyperglycemia, glucose intolerance, and insulin resistance. Collectively, our studies identify the gene Itpr1 being interrupted in the D2D mice and uncover a novel role of IP3R1 in regulation of in vivo glucose homeostasis and development of diet-induced diabetes.

Identification of the proteins related to p53-mediated radioresponse in nasopharyngeal carcinoma by proteomic analysis

Radiotherapy is the primary treatment for nasopharyngeal cancer (NPC), and p53 is closely associated with the radiosensitivity of cancer, but the molecular mechanisms of p53-mediated radioresponse in NPC remains unclear. We previously established NPC CNE2sip53 cell line with p53 knockdown and paired control cell line CNE2/pSUPER, which provides a cell model system to investigate mechanisms of p53-mediated radioresponse in NPC. In this study, we first compared the radiosensitivity of CNE2sip53 and CNE2/pSUPER by a clonogenic survival assay, cell growth assay, and Hoechst 33258 staining and flow cytometry analysis of apoptotic cells. The results showed that the radiosensitivity of CNE2sip53 was significantly lower than that of CNE2/pSUPER, indicating that p53 plays a role in mediating NPC radiosensitivity. To search for the proteins associated with the p53-mediated radioresponse in NPC, a proteomic approach was performed to identify the radioresponsive proteins in CNE2sip53 and CNE2p/SUPER, respectively, and then the difference of radioresponsive proteins in CNE2sip53 and CNE2p/SUPER was compared. As a result, 14 differential radioresponsive proteins were identified in the two cell lines, 4 proteins of which were conformed by Western blot. Among them, 9 and 5 proteins were identified solely from CNE2p/SUPER and CNE2sip53, respectively. Furthermore, protein-protein interaction analysis showed that 7 differential radioresponsive proteins identified only in CNE2p/SUPER were related to p53 protein. Our results suggest that the differential radioresponsive proteins unique to CNE2p/SUPER may be involved in p53-mediated radioresponse in NPC, which will be helpful for elucidating the mechanisms of p53-mediated NPC cellular response to radiotherapy.

Association of elevated GRP78 expression with increased astrocytoma malignancy via Akt and ERK pathways

Unlike other members of HSP70 family, GRP78 manifests multifaceted subcellular distribution and forms complex with different signals, resulting in its close correlation with various tumors. However, its expression profile and function in glioma remain less well defined. In this study, normal brain tissue and astrocytic tumor specimens were evaluated for GRP78 expression, which was shown to be up-regulated in astrocytoma compared with normal tissue, increased markedly as astrocytoma pathologic grade escalates, and can still be enhanced for disease recurrence. By employing Cox regression analyses, high GRP78 expression was correlated with a poorer outcome for recurrent glioblastoma patients. In addition, immunofluorescence microscopy detected cell surface positioning of GRP78 on human glioma cells. After transfection with siRNA or antibody ligation of surface GRP78, phosphorylation of Akt and ERK was attenuated. These findings indicate that GRP78 plays an important role in astrocytoma malignancy, whereas its cell surface localization may be attractive for clinical utilization.

Roles of GRP78 in physiology and cancer

As one member of 70 kDa heat shock proteins, glucose-regulated protein 78 (GRP78) participates in protein folding, transportation and degradation. This sort of capacity can be enhanced by stresses under which GRP78 is induced rapidly. Unlike its homologues, GRP78 presents multifaceted subcellular position: When ER retention, it serves as the switch of unfolded protein response; When mitochondrial binding, it directly interacts with apoptotic executors; When cell surface residing, it recognizes extracellular ligands, transducing proliferative signals, especially in certain tumors. The close correlation between GRP78 and neoplasm provides us further insight into the event of carcinogenesis and cancer cell chemoresistance, indicating its prognostic predicting significance and validating potential therapeutics for clinical usage, especially because its small molecular inhibitors are emerging quickly these years. What's more, GRP78-related signaling may be helpful for clearer understanding of its biological mechanisms.

GRP78 up-regulation is associated with androgen receptor status, Hsp70-Hsp90 client proteins and castrate-resistant prostate cancer

GRP78/BiP is a key member of the molecular chaperone heat shock protein (Hsp) 70 family. It has a critical role in prostate cancer (PC) including Pten loss-driven carcinogenesis, but the molecular basis of this remains unclear. We investigated the effect of GRP78 and its putative client proteins, including androgen receptor (AR) in clinical PC. Expression of GRP78 and key Hsp70-hsp90 client proteins (HER2, HER3, AR and AKT) were studied in an incidence tissue microarray (TMA) of prostate cancer. The relationship of GRP78 and AR was further tested in in vitro cell models (LNCaP and its derived LNCaP-CR subclone) and a matched TMA of hormone-naïve (HNPC) and castrate-resistant prostate cancer (CRPC). In vitro and in vivo expression of GRP78 and client proteins were assessed by western blotting and immunohistochemistry, respectively, using the weighted histoscore method. Significant co-expression of GRP78, pAKT, HER2, HER3 and AR was observed in PC. Abnormal AR, GRP78 and pAKT expression have significant impact on patient survival. GRP78 expression in AR(+) tumours was significantly higher than in AR(-) tumours. In keeping with our clinical data, activation of AR by dihydrotestosterone (DHT) potently activated GRP78 expression in both LNCaP and LNCaP-CR cells. For the first time, using a matched HNPC and CRPC TMA, enhanced cytoplasmic and membranous GRP78 expression was observed in CRPC. Future prospective studies are therefore warranted to validate GRP78 as prognostic marker and therapeutic target, in the context of the AR and pAKT status. In summary, GRP78 is co-expressed with Hsp70-hsp90 client proteins. Up-regulated expression of AR and GRP78 expression in untreated prostate cancer predicts a less favourable outcome. This points to the importance of understanding in the molecular interaction among AR, GRP78 and AKT.

The role of porphyrin chemistry in tumor imaging and photodynamic therapy

In recent years several review articles and books have been published on the use of porphyrin-based compounds in photodynamic therapy (PDT). This critical review is focused on (i) the basic concept of PDT, (ii) advantages of long-wavelength absorbing photosensitizers (PS), (iii) a brief discussion on recent advances in developing PDT agents, and (iv) the various synthetic strategies designed at the Roswell Park Cancer Institute, Buffalo, for developing highly effective long-wavelength PDT agents and their utility in constructing the conjugates with tumor-imaging and therapeutic potential (Theranostics). The clinical status of certain selected PDT agents is also summarized (205 references).

Glucose-regulated protein 78 (GRP78) silencing enhances cell migration but does not influence cell proliferation in hepatocellular carcinoma

BACKGROUND

GRP78 plays an essential role in embryonic development and in the therapeutic treatment and progression of cancer. However, little is known about the role of GRP78 in hepatocellular carcinoma (HCC).

METHODS

In this study, we characterized five different HCC cell lines to examine GRP78 expression patterns and found that only HepJ5 cells ectopically overexpress GRP78. We knocked down GRP78 expression in HepJ5 cells using a small interfering RNA (siRNA), and the proliferation assay and migration assay were performed.

RESULTS

Using siRNA technique, we could successfully reduce GRP78 expression levels in HepJ5 cells. In a cell growth study, we found that GRP78-siRNA caused no significant changes in cellular proliferation in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation, and cell cycle distribution. In a cell migration study, we found that GRP78-siRNA HepJ5 cells had dramatically increased migration ability in Transwell assay.

CONCLUSIONS

We conclude that ectopically expressed GRP78 does not contribute to the increased proliferation of HepJ5 cells, but does correlate with the migration of HCC cells under normoxic conditions.

Identification of biomarkers for predicting nasopharyngeal carcinoma response to radiotherapy by proteomics

Radiotherapy is the primary treatment for nasopharyngeal cancer (NPC), but radioresistance remains a serious obstacle to successful treatment in many cases. To identify the proteins involved in this resistance and to evaluate their potential for predicting NPC response to radiotherapy, we first established a radioresistant subclone cell line (CNE2-IR) derived from NPC cell line CNE2 by treating the cells with five rounds of sublethal ionizing radiation. Proteomics was then performed to compare the protein profiles of CNE2-IR and CNE2, and a total of 34 differential proteins were identified. Among them, 14-3-3sigma and Maspin were downregulated and GRP78 and Mn-SOD were upregulated in the radioresistant CNE2-IR compared with control CNE2, which was conformed by Western blot. Immunohistochemistry was performed to detect the expression of the four validated proteins in the 39 radioresistant and 51 radiosensitive NPC tissues and their value for predicting NPC response to radiotherapy were evaluated by receiver operating characteristic analysis. The results showed that the downregulation of 14-3-3sigma and Maspin and the upregulation of GRP78 and Mn-SOD were significantly correlated with NPC radioresistance and the combination of the four proteins achieved a sensitivity of 90% and a specificity of 88% in discriminating radiosensitive from radiaoresistant NPC. Furthermore, the resistance to ionizing radiation can be partially reversed by the overexpression of 14-3-3sigma in the CNE2-IR. The data suggest that 14-3-3sigma, Maspin, GRP78, and Mn-SOD are potential biomarkers for predicting NPC response to radiotherapy and their dysregulation may be involved in the radioresistance of NPC.

Patterns of GRP78 and MTJ1 expression in primary cutaneous malignant melanoma

Cell surface expression of glucose-regulated protein 78 (GRP78) occurs in several types of cancer; however, its role in the behavior of primary cutaneous melanoma is not well studied. The association of cell surface GRP78 with other proteins such as MTJ1 stimulates cell proliferation. In this study, we characterized the pattern of expression of GRP78 and MTJ1 in invasive primary cutaneous melanomas and analyzed the relationships between the pattern of expression and various clinicopathological parameters. We found two patterns of GRP78 expression in invasive primary cutaneous melanoma. One pattern showed a gradual fading of protein expression from superficial to deeper levels within the same tumor. The second pattern of expression showed a similar fading with an abrupt regaining of expression at the deep invasive edge of the melanoma. These two distinct patterns of GRP78 expression correlated with both patient survival and depth of tumor invasion. A moderate MTJ1 expression was found to be associated with decreased patient survival; however, no significant associations were observed between patterns of GRP78 and MTJ1 expression. Our study (1) describes two distinct patterns of GRP78 in invasive primary cutaneous melanoma, (2) inversely correlates regain of GRP78 expression with patient survival, and (3) suggests a modifying effect of MTJ1 on GRP78 in enhancing tumor aggressiveness.

Targeting the endoplasmic reticulum-stress response as an anticancer strategy

The endoplasmic reticulum (ER) is the site of synthesis and folding of secretory and membrane bound proteins. The capacity of the ER to process proteins is limited and the accumulation of unfolded and misfolded proteins can lead to ER stress which has been associated with a wide range of diseases including cancer. In this review we initially provide an overview of our current understanding of how cells respond to ER stress at the molecular level and the key players involved in mediating the unfolded protein response (UPR). We review the evidence suggesting that the ER stress response could be important for the growth and development of tumors under stressful growth conditions such as hypoxia or glucose deprivation, which are commonly encountered by most solid tumors, and we analyse how it may be possible to exploit the unfolded protein response as an anticancer strategy. Two approaches to target the unfolded protein response are proposed-the first involves inhibiting components of the unfolded protein response so cells cannot adapt to stressful conditions and the second involves overloading the unfolded protein response so the cell is unable to cope, leading to cell death. We focused on proteins with an enzymatic activity that can be targeted by small molecule inhibitors as this is one of the most common approaches utilized by drug discovery companies. Finally, we review drugs currently in clinical development that affect the ER stress response and that may have potential as anti-tumor agents alone or in combination with other chemotherapeutics.

Effectiveness of HSV-tk suicide gene therapy driven by the Grp78 stress-inducible promoter in esophagogastric junction and gastric adenocarcinomas

BACKGROUND

The thymidine kinase gene of the herpes simplex virus (HSV-tk) is a suicide gene when administrated with the prodrug ganciclovir (GCV). This study investigated the effectiveness of HSV-tk activation as gene therapy for gastroesophageal junction and gastric adenocarcinomas using either the stress-inducible Grp78 promoter or the murine leukemia virus long-terminal repeat (LTR) promoter.

METHODS

The HSV-tk gene, controlled by either the Grp78 promoter or the LTR promoter, was transduced into the gastroesophageal junction adenocarcinoma cell line SK-GT-5 and the gastric adenocarcinoma cell line MKN-74. Cell viability after exposure to varying concentrations of GCV was compared. The same cell lines were used to develop a nude mouse model for studies of the HSV-tk/GCV effect in vivo. The effect of intraperitoneal GCV injection on growth of the subcutaneous tumors was measured. HSV-TK expression was measured by Western blot and reverse transcription polymerase chain reaction.

RESULTS

Cell viability in vitro was significantly lower in the HSV-tk expressing (HSV-tk+) cells compared to control (no HSV-tk) cells after exposure to GCV. MKN-74tk+ cells were more sensitive to GCV killing than SK-GT-5tk+ cells. After culture with 1 microg/ml GCV for 10 days, MKN-74/tk cells were totally killed, whereas most SK-GT-5/tk cells survived. Cell viability was significantly lower under glucose starvation conditions when HSV-tk expression was regulated by the Grp78 promoter compared with the LTR promoter. MKN-74 tumors formed with HSV-tk+ cells in nude mice were eliminated after administration of GCV for 3 weeks, but GCV had no effect on tumors formed from HSV-tk- cells. Eradication of tumor formed with Grp78-tk cells was faster than that with LTR-tk cells. HSV-TK protein and mRNA were expressed in the transduced, but not the non-transduced tumors.

CONCLUSION

HSV-tk xwith ganciclovir suicide gene therapy results in significant cell killing in gastroesophageal junction and gastric adenocarcinoma cells both in vitro and in vivo, but complete tumor elimination only occurred with the gastric adenocarcinoma cell tumors. The most effective approach in this study used the Grp78 promoter in glucose-starvation stress conditions.