The expression of the endoplasmic reticulum stress sensor BiP/GRP78 predicts response to chemotherapy and determines the efficacy of proteasome inhibitors in diffuse large b-cell lymphoma

Targeting PAK4 reverses cisplatin resistance in NSCLC by modulating ER stress

Chemoresistance poses a significant impediment to effective treatments for non-small-cell lung cancer (NSCLC). P21-activated kinase 4 (PAK4) has been implicated in NSCLC progression by invasion and migration. However, the involvement of PAK4 in cisplatin resistance is not clear. Here, we presented a comprehensive investigation into the involvement of PAK4 in cisplatin resistance within NSCLC. Our study revealed enhanced PAK4 expression in both cisplatin-resistant NSCLC tumors and cell lines. Notably, PAK4 silencing led to a remarkable enhancement in the chemosensitivity of cisplatin-resistant NSCLC cells. Cisplatin evoked endoplasmic reticulum stress in NSCLC. Furthermore, inhibition of PAK4 demonstrated the potential to sensitize resistant tumor cells through modulating endoplasmic reticulum stress. Mechanistically, we unveiled that the suppression of the MEK1-GRP78 signaling pathway results in the sensitization of NSCLC cells to cisplatin after PAK4 knockdown. Our findings establish PAK4 as a promising therapeutic target for addressing chemoresistance in NSCLC, potentially opening new avenues for enhancing treatment efficacy and patient outcomes.

Genetic and Pharmacological Modulation of Cellular Proteostasis Leads to Partial Functional Rescue of Homocystinuria-Causing Cystathionine-Beta Synthase Variants

Homocystinuria (HCU), an inherited metabolic disorder caused by lack of cystathionine beta-synthase (CBS) activity, is chiefly caused by misfolding of single amino acid residue missense pathogenic variants. Previous studies showed that chemical, pharmacological chaperones or proteasome inhibitors could rescue function of multiple pathogenic CBS variants; however, the underlying mechanisms remain poorly understood. Using Chinese hamster DON fibroblasts devoid of CBS and stably overexpressing human WT or mutant CBS, we showed that expression of pathogenic CBS variant mostly dysregulates gene expression of small heat shock proteins HSPB3 and HSPB8 and members of HSP40 family. Endoplasmic reticulum stress sensor BiP was found upregulated with CBS I278T variant associated with proteasomes suggesting proteotoxic stress and degradation of misfolded CBS. Co-expression of the main effector HSP70 or master regulator HSF1 rescued steady-state levels of CBS I278T and R125Q variants with partial functional rescue of the latter. Pharmacological proteostasis modulators partially rescued expression and activity of CBS R125Q likely due to reduced proteotoxic stress as indicated by decreased BiP levels and promotion of refolding as indicated by induction of HSP70. In conclusion, targeted manipulation of cellular proteostasis may represent a viable therapeutic approach for the permissive pathogenic CBS variants causing HCU.

Possible New Histological Prognostic Index for Large B-Cell Lymphoma

We conducted a retrospective analysis of GRP94 immunohistochemical (IHC) staining, an ER stress protein, on large B-cell lymphoma (LBCL) cells, intracellular p53, and 15 factors involved in the metabolism of the CHOP regimen: AKR1C3 (HO metabolism), CYP3A4 (CHOP metabolism), and HO efflux pumps (MDR1 and MRP1). The study subjects were 42 patients with LBCL at our hospital. The IHC staining used antibodies against the 17 factors. The odds ratios by logistic regression analysis used a dichotomous variable of CR and non-CR/relapse were statistically significant for MDR1, MRP1, and AKR1C3. The overall survival (OS) after R-CHOP was compared by the log-rank test. The four groups showed that Very good (5-year OS, 100%) consisted of four patients who showed negative IHC staining for both GRP94 and CYP3A4. Very poor (1-year OS, 0%) consisted of three patients who showed positive results in IHC for both GRP94 and CYP3A4. The remaining 35 patients comprised two subgroups: Good (5-year OS 60-80%): 15 patients who showed negative staining for both MDR1 and AKR1C3 and Poor (5-year OS, 10-20%): 20 patients who showed positive staining for either MDR, AKR1C3, MRP1, or p53. The Histological Prognostic Index (HPI) (the four groups: Very poor, Poor, Good, and Very good) is a breakthrough method for stratifying patients based on the factors involved in the development of treatment resistance.

Targeted inhibition of protein synthesis renders cancer cells vulnerable to apoptosis by unfolded protein response

Cellular stress responses including the unfolded protein response (UPR) decide over the fate of an individual cell to ensure survival of the entire organism. During physiologic UPR counter-regulation, protective proteins are upregulated to prevent cell death. A similar strategy induces resistance to UPR in cancer. Therefore, we hypothesized that blocking protein synthesis following induction of UPR substantially enhances drug-induced apoptosis of malignant cells. In line, upregulation of the chaperone BiP was prevented by simultaneous arrest of protein synthesis in B cell malignancies. Cytotoxicity by immunotoxins-approved inhibitors of protein synthesis-was synergistically enhanced in combination with UPR-inducers in seven distinct hematologic and three solid tumor entities in vitro. Synergistic cell death depended on mitochondrial outer membrane permeabilization via BAK/BAX, which correlated with synergistic, IRE1α-dependent reduction of BID, accompanied by an additive fall of MCL-1. The strong synergy was reproduced in vivo against xenograft mouse models of mantle cell lymphoma, Burkitt's lymphoma, and patient-derived acute lymphoblastic leukemia. In contrast, synergy was absent in blood cells of healthy donors suggesting a tumor-specific vulnerability. Together, these data support clinical evaluation of blocking stress response counter-regulation using inhibitors of protein synthesis as a novel therapeutic strategy.

Unveiling the dark side of glucose-regulated protein 78 (GRP78) in cancers and other human pathology: a systematic review

Glucose-Regulated Protein 78 (GRP78) is a chaperone protein that is predominantly expressed in the lumen of the endoplasmic reticulum. GRP78 plays a crucial role in protein folding by assisting in the assembly of misfolded proteins. Under cellular stress conditions, GRP78 can translocate to the cell surface (csGRP78) were it interacts with different ligands to initiate various intracellular pathways. The expression of csGRP78 has been associated with tumor initiation and progression of multiple cancer types. This review provides a comprehensive analysis of the existing evidence on the roles of GRP78 in various types of cancer and other human pathology. Additionally, the review discusses the current understanding of the mechanisms underlying GRP78's involvement in tumorigenesis and cancer advancement. Furthermore, we highlight recent innovative approaches employed in downregulating GRP78 expression in cancers as a potential therapeutic target.

Endoplasmic Reticulum Stress in the Brain Tumor Immune Microenvironment

Immunotherapy has emerged as a powerful strategy for halting cancer progression. However, primary malignancies affecting the brain have been exempt to this success. Indeed, brain tumors continue to portend severe morbidity and remain a globally lethal disease. Extensive efforts have been directed at understanding how tumor cells survive and propagate within the unique microenvironment of the central nervous system (CNS). Cancer genetic aberrations and metabolic abnormalities provoke a state of persistent endoplasmic reticulum (ER) stress that in turn promotes tumor growth, invasion, therapeutic resistance, and the dynamic reprogramming of the infiltrating immune cells. Consequently, targeting ER stress is a potential therapeutic approach. In this work, we provide an overview of how ER stress response is advantageous to brain tumor development, discuss the significance of ER stress in governing antitumor immunity, and put forth therapeutic strategies of regulating ER stress to augment the effect of immunotherapy for primary CNS tumors.

Is It Still Possible to Think about HSP70 as a Therapeutic Target in Onco-Hematological Diseases?

The search for molecules to be targeted that are involved in apoptosis resistance/increased survival and pathogenesis of onco-hematological malignancies is ongoing since these diseases are still not completely understood. Over the years, a good candidate has been identified in the Heat Shock Protein of 70kDa (HSP70), a molecule defined as “the most cytoprotective protein ever been described”. HSP70 is induced in response to a wide variety of physiological and environmental insults, allowing cells to survive lethal conditions. This molecular chaperone has been detected and studied in almost all the onco-hematological diseases and is also correlated to poor prognosis and resistance to therapy. In this review, we give an overview of the discoveries that have led us to consider HSP70 as a therapeutic target for mono- or combination-therapies in acute and chronic leukemias, multiple myeloma and different types of lymphomas. In this excursus, we will also consider HSP70 partners, such as its transcription factor HSF1 or its co-chaperones whose druggability could indirectly affect HSP70. Finally, we will try to answer the question asked in the title of this review considering that, despite the effort made by research in this field, HSP70 inhibitors never reached the clinic.

Bortezomib prodrug catalytic nanoreactor for chemo/chemodynamic therapy and macrophage re-education

Chemodynamic therapy (CDT), an emerging tumor-specific therapeutic modality, is frequently restrained by insufficient intratumoral Fenton catalysts and increasingly inefficient catalysis caused by the continuous consumption of limited H₂O₂ within tumors. Herein, we engineered a pH-responsive bortezomib (BTZ) polymer prodrug catalytic nanoreactor (HeZn@HA-BTZ) capable of self-supplying Fenton catalyst and H₂O₂. It is aimed for tumor-specific chemo/chemodynamic therapy via oxidative stress and endoplasmic reticulum (ER) stress dual-amplification and macrophage repolarization. A catechol‑boronate bond-based hyaluronic acid-BTZ prodrug HA-DA-BTZ was modified on Hemin and Zn²⁺ coordination nanoscale framework (HeZn), an innovative CDT inducer, to construct He-Zn@HA-BTZ. He-Zn@HA-BTZ with good stability and superior peroxidase-like activity preferentially accumulated at tumor sites and be actively internalized by tumor cells. Under the cleavage of catechol‑boronate bond in acidic endo/lysosomes, pre-masked BTZ was rapidly released to induce ubiquitinated protein aggregation, robust ER stress and elevated H₂O₂ levels. The amplified H₂O₂ was further catalyzed by HeZn via Fenton-catalytic reactions to produce hypertoxic •OH, enabling cascaded oxidative stress amplification and long-lasting effective CDT, which in turn aggravated BTZ-induced ER stress. Eventually, a dual-amplification of oxidative stress and ER stress was achieved to initiate cell apoptosis/necrosis with reduced BTZ toxicity. Intriguingly, He-Zn@HA-BTZ could repolarize macrophages from M2 to antitumor M1 phenotype for potential tumor therapy. This "all in one" prodrug nanocatalytic reactor not only enriches the CDT inducer library, but provides inspirational strategy for simultaneous oxidative stress and ER stress based excellent cancer therapy.

An in vivo drug repurposing screen and transcriptional analyses reveals the serotonin pathway and GSK3 as major therapeutic targets for NGLY1 deficiency

NGLY1 deficiency, a rare disease with no effective treatment, is caused by autosomal recessive, loss-of-function mutations in the N-glycanase 1 (NGLY1) gene and is characterized by global developmental delay, hypotonia, alacrima, and seizures. We used a Drosophila model of NGLY1 deficiency to conduct an in vivo, unbiased, small molecule, repurposing screen of FDA-approved drugs to identify therapeutic compounds. Seventeen molecules partially rescued lethality in a patient-specific NGLY1 deficiency model, including multiple serotonin and dopamine modulators. Exclusive dNGLY1 expression in serotonin and dopamine neurons, in an otherwise dNGLY1 deficient fly, was sufficient to partially rescue lethality. Further, genetic modifier and transcriptomic data supports the importance of serotonin signaling in NGLY1 deficiency. Connectivity Map analysis identified glycogen synthase kinase 3 (GSK3) inhibition as a potential therapeutic mechanism for NGLY1 deficiency, which we experimentally validated with TWS119, lithium, and GSK3 knockdown. Strikingly, GSK3 inhibitors and a serotonin modulator rescued size defects in dNGLY1 deficient larvae upon proteasome inhibition, suggesting that these compounds act through NRF1, a transcription factor that is regulated by NGLY1 and regulates proteasome expression. This study reveals the importance of the serotonin pathway in NGLY1 deficiency, and serotonin modulators or GSK3 inhibitors may be effective therapeutics for this rare disease.

NGLY1 deficiency is a rare disease with no effective treatment. We conducted a drug repurposing screen and used the Connectivity Map, a transcriptional-based computational approach, to identify compounds that may serve as therapeutics for NGLY1 deficient individuals. The drug repurposing screen identified FDA-approved compounds acting through the serotonin and dopamine pathway that partially rescued lethality in an NGLY1 deficiency fly model. We also found that expressing dNGLY1 (the Drosophila ortholog of NGLY1) exclusively in serotonin neurons, in an otherwise dNGLY1 deficient fly, partially rescued lethality. These data indicate the importance of the serotonin and dopamine systems in NGLY1 deficiency. The Connectivity Map analyses found GSK3 inhibitors as potential therapeutic compounds, which were validated in vivo in the fly. Furthermore, knockdown of sgg (the Drosophila ortholog of GSK3) partially rescued lethality in dNGLY1 deficient flies, suggesting GSK3 as a therapeutic target for NGLY1 deficiency. Taken together, this work identifies therapeutic strategies for NGLY1 deficiency.

Ixazomib induces apoptosis and suppresses proliferation in esophageal squamous cell carcinoma through activation of the c-Myc/NOXA pathway

Esophageal squamous cell carcinoma (ESCC) is one of the major subtypes of esophageal cancer. More than half of the ESCC patients in the world are in China, and the 5-year survival rate is less than 10%. As a new oral proteasome inhibitor, ixazomib has shown strong therapeutic effect in many solid tumors. In this study, we aimed to investigate the effects of ixazomib on the proliferation inhibition and apoptosis of ESCC cells.We used four human ESCC cell lines, cell viability assay, cell cycle and apoptosis assay, RT-PCR, Western blot, immunohistochemistry and ESCC xenografts model to clarify the roles of the therapeutic effect and mechanism of ixazomib in ESCC. Ixazomib significantly inhibited the proliferation and induced apoptosis in ESCC cells. RT-PCR results showed that the expression of endoplasmic reticulum stress-related gene NOXA and c-Myc significant increase after treatment with ixazomib in ESCC cell. Then we knockdown the NOXA and c-Myc by siRNA, the therapeutic effect of ixazomib markedly decrease, which confirmed that c-Myc/NOXA pathway played a key role in the treatment of ESCC with ixazomib. In vivo, the xenograft ESCC model mice were given 10 mg/kg of ixazomib every other day for 30 days. The results showed that the tumor size in the treatment group was significantly smaller than the control group. These results suggested that ixazomib is known to suppress proliferation and induce apoptosis in an ESCC cell lines, and this effect was likely mediated by increased activation of the c-Myc/NOXA signaling pathways. Significance Statement Esophageal squamous cell carcinoma (ESCC) is the common worldwide malignant tumors,but conventional chemotherapeutics suffer from a number of limitations. In this study, our results suggested that ixazomib is known to suppress proliferation and induce apoptosis in an ESCC cell lines. Therefore, ixazomib may be a potential new stratgegy for ESCC therapy.

Glucose- regulated protein 78 (GRP78) in renal cell carcinoma: A novel biomarker for predicting tumor behavior

Objective

To study the mRNA and protein expression of GRP78 in tumor and serum of the RCC patients and compare with the controls and to correlate the expression with the grade and stage of RCC.

Materials and methods

A prospective cohort study involving 60 patients planned for radical/partial nephrectomy for primary RCC between July 2017 to June 2019. The RCC and adjacent non-tumorous renal tissues (Control) along with serum samples of patients were collected. Control for the serum samples is from the patients undergoing simple nephrectomy for non-functioning kidney due to benign etiology. The GRP78 expression was studied using RT-PCR for mRNA expression, Western blot analysis and immunohistochemistry (IHC) for protein expression and using ELISA in serum for both the subjects and controls.

Results

Mean age of patients was 50.3 years. The mRNA and protein expression of GRP78 in tissue samples were significantly higher in RCC patients as compared to controls (p < 0.001). IHC also demonstrated significantly higher expression in tumour samples as compared to controls (p < 0.001). Circulatory levels of GRP78 in serum samples were also significantly increased (p < 0.0001) in RCC patients in comparison to control subjects. The expression of GRP78 in circulation significantly correlated with the pathological tumor stage (p = 0.03), grade of disease (p < 0.001).

Conclusion

The GRP78 in RCC is significantly upregulated both at molecular and protein level expression. The overexpression of GRP78 correlates with the stage and grade of disease, thereby, highlighting its prognostic ability.

The regulation of miR-320a/XBP1 axis through LINC00963 for endoplasmic reticulum stress and autophagy in diffuse large B-cell lymphoma

Background

This study incorporates fundamental research referring to considerable amounts of gene-sequencing data and bioinformatics tools to analyze the pathological mechanisms of diffuse large B-cell lymphoma (DLBCL).

Methods

A lncRNA-miRNA-mRNA ceRNA network of DLBCL was constructed through database analysis combining GTEx and TCGA. qPCR was used to detect the expression of LINC00963 and miR-320a in DLBCL cell lines. After LINC00963 or miR-320a overexpression in vitro, western blot was performed to assess the protein levels of UPR sensors (GRP78, p-IRE1, IRE1, active ATF6, ATF4 and XBP1), along with apoptosis markers (Bcl-2, Bax, caspase 3) and autophagy indicators (Beclin1, LC3II, LC3I and p62). Additionally, the expression of LC3 was analyzed through immunofluorescence (IF) assay. 

Results

Following LINC00963 overexpression in vitro, SUDHL4 cell line showed a marked increase in the level of UPR-related GRP78, p-IRE1 and spliced XBP-1/XBP-1(s), apoptosis-related Bax and cleaved caspase 3, as well as autophagy-related Beclin1 and LC3II, whereas miR-320a mimic greatly diminished the effects of LINC00963 overexpression. Moreover, LINC00963 targeted miR-320a while miR-320a bound to the 3’UTR of XBP1. It was also found that LINC00963 overexpression resulted in significantly delayed tumor growth in a xenograft model of DLBCL. 

Conclusion

Mechanistically, LINC00963/miR-320a regulated XBP1-apoptosis pathway and autophagy, implying the therapeutic potential of this pathway for selective targeting. The data presented here illustrated the mechanism of LINC00963/miR-320a/XBP1 in DLBCL for the first time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01992-y.

An Emerging Role for the Unfolded Protein Response in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and one of the leading causes of cancer-associated deaths in the world. It is characterised by dismal response rates to conventional therapies. A major challenge in treatment strategies for PDAC is the presence of a dense stroma that surrounds the tumour cells, shielding them from treatment. This unique tumour microenvironment is fuelled by paracrine signalling between pancreatic cancer cells and supporting stromal cell types including the pancreatic stellate cells (PSC). While our molecular understanding of PDAC is improving, there remains a vital need to develop effective, targeted treatments. The unfolded protein response (UPR) is an elaborate signalling network that governs the cellular response to perturbed protein homeostasis in the endoplasmic reticulum (ER) lumen. There is growing evidence that the UPR is constitutively active in PDAC and may contribute to the disease progression and the acquisition of resistance to therapy. Given the importance of the tumour microenvironment and cytokine signalling in PDAC, and an emerging role for the UPR in shaping the tumour microenvironment and in the regulation of cytokines in other cancer types, this review explores the importance of the UPR in PDAC biology and its potential as a therapeutic target in this disease.

Adaptive response of resistant cancer cells to chemotherapy

Despite advances in cancer therapeutics and the integration of personalized medicine, the development of chemoresistance in many patients remains a significant contributing factor to cancer mortality. Upon treatment with chemotherapeutics, the disruption of homeostasis in cancer cells triggers the adaptive response which has emerged as a key resistance mechanism. In this review, we summarize the mechanistic studies investigating the three major components of the adaptive response, autophagy, endoplasmic reticulum (ER) stress signaling, and senescence, in response to cancer chemotherapy. We will discuss the development of potential cancer therapeutic strategies in the context of these adaptive resistance mechanisms, with the goal of stimulating research that may facilitate the development of effective cancer therapy.

CXL146, a Novel 4H-Chromene Derivative, Targets GRP78 to Selectively Eliminate Multidrug-Resistant Cancer Cells

The 78-kDa glucose-regulated protein (GRP78), an endoplasmic reticulum (ER) chaperone, is a master regulator of the ER stress. A number of studies revealed that high levels of GRP78 protein in cancer cells confer multidrug resistance (MDR) to therapeutic treatment. Therefore, drug candidate that reduces GRP78 may represent a novel approach to eliminate MDR cancer cells. Our earlier studies showed that a set of 4H-chromene derivatives induced selective cytotoxicity in MDR cancer cells. In the present study, we elucidated its selective mechanism in four MDR cancer cell lines with one lead candidate (CXL146). Cytotoxicity results confirmed the selective cytotoxicity of CXL146 toward the MDR cancer cell lines. We noted significant overexpression of GRP78 in all four MDR cell lines compared with the parental cell lines. Unexpectedly, CXL146 treatment rapidly and dose-dependently reduced GRP78 protein in MDR cancer cell lines. Using human leukemia (HL) 60/mitoxantrone (MX) 2 cell line as the model, we demonstrated that CXL146 treatment activated the unfolded protein response (UPR); as evidenced by the activation of inositol-requiring enzyme 1α, protein kinase R-like ER kinase, and activating transcription factor 6. CXL146-induced UPR activation led to a series of downstream events, including extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase activation, which contributed to CXL146-induced apoptosis. Targeted reduction in GRP78 resulted in reduced sensitivity of HL60/MX2 toward CXL146. Long-term sublethal CXL146 exposure also led to reduction in GRP78 in HL60/MX2. These data collectively support GRP78 as the target of CXL146 in MDR treatment. Interestingly, HL60/MX2 upon long-term sublethal CXL146 exposure regained sensitivity to mitoxantrone treatment. Therefore, further exploration of CXL146 as a novel therapy in treating MDR cancer cells is warranted. SIGNIFICANCE STATEMENT: Multidrug resistance is one major challenge to cancer treatment. This study provides evidence that cancer cells overexpress 78-kDa glucose-regulated protein (GRP78) as a mechanism to acquire resistance to standard cancer therapies. A chromene-based small molecule, CXL146, selectively eliminates cancer cells with GRP78 overexpression via activating unfolded protein response-mediated apoptosis. Further characterization indicates that CXL146 and standard therapies complementarily target different populations of cancer cells, supporting the potential of CXL146 to overcome multidrug resistance in cancer treatment.

Induction of Endoplasmic Reticulum Stress Pathway by Green Tea Epigallocatechin-3-Gallate (EGCG) in Colorectal Cancer Cells: Activation of PERK/p-eIF2α/ATF4 and IRE1α

Epigallocatechin-3-gallate (EGCG) is the most abundant bioactive polyphenolic compound among the green tea constituents and has been identified as a potential anticancer agent in colorectal cancer (CRC) studies. This study was aimed to determine the mechanism of actions of EGCG when targeting the endoplasmic reticulum (ER) stress pathway in CRC. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay was performed on HT-29 cell line and normal cell line (3T3) to determine the EGCG toxicity. Next, western blot was done to observe the expression of the related proteins for the ER stress pathway. The Caspase 3/7 assay was performed to determine the apoptosis induced by EGCG. The results demonstrated that EGCG treatment was toxic to the HT-29 cell line. EGCG induced ER stress in HT-29 by upregulating immunoglobulin-binding (BiP), PKR-like endoplasmic reticulum kinase (PERK), phosphorylation of eukaryotic initiation factor 2 alpha subunit (eIF2α), activating transcription 4 (ATF4), and inositol-requiring kinase 1 alpha (IRE1α). Apoptosis was induced in HT-29 cells after the EGCG treatment, as shown by the Caspase 3/7 activity. This study indicates that green tea EGCG has the potential to inhibit colorectal cancer cells through the induction of ER stress.

The level of the endoplasmic reticulum stress chaperone protein, binding immunoglobulin protein (BiP), decreases following successful tuberculosis treatment

An increased Mycobacterium tuberculosis burden inside the host leads to higher demand of response proteins. This in turn results in metabolic shift and cellular stress, which is caused by the accumulation and trafficking of these proteins within the endoplasmic reticulum (ER). To resolve this, cells trigger the unfolded protein response (UPR), which is mainly mediated by binding immunoglobulin protein (BiP)/glucose-regulated protein 78 (GRP78) chaperone, and this in turn upregulates its transcription. This chaperone protein facilitates proper protein folding within the ER; however, it can also be passively secreted into the extracellular environment or be expressed on cell surfaces attached to anchor proteins and transmembrane proteins. This notion has been shown in studies on chronic inflammation, including cancer and arthritis, with the detection of BiP-specific antibodies from different sample types. The present study analysed secreted BiP from plasma samples collected from healthy participants and patients with newly diagnosed tuberculosis (TBdx), seen over the course of TB treatment at week 1 (W1), month 2 (M2), and month 6 (M6). The results revealed that during the initial TB disease and treatment period, cells are subjected to stress conditions resulting in metabolic shifts, which lead to the secretion of the intracellular UPR-mediating chaperone protein, BiP. This was indicated by mean differences between TBdx (mean 40.88ng/ml) and W1 (68.57ng/ml) in the TB participant groups. However, no difference was observed between the healthy group (mean 42.64ng/ml) and TBdx group (mean 40.88ng/ml). Analysis of paired time-point visits revealed increased BiP secretion during early TB treatment. The detection of BiP in plasma samples was found to decrease after successful TB treatment to levels comparable to those in the healthy controls. Evaluation of BiP levels in larger TB treatment studies may lead to the identification of a new target for early TB diagnosis and host-directed immunotherapy.

Inhibition of endoplasmic-reticulum-stress-mediated autophagy enhances the effectiveness of chemotherapeutics on pancreatic cancer

Background

Endoplasmic reticulum (ER) stress and its consequent unfolded protein response (UPR) are believed to be associated with progression, survival and chemoresistance of a variety of tumor cells through multiple cellular processes, including autophagy. Therefore, the ER stress-autophagy pathway presents a potential molecular target for therapeutic intervention. The objective of this study was to evaluate the therapeutic efficacy of ER stress and autophagy modulators in the context of pancreatic ductal adenocarcinoma (PDAC).

Methods

We first targeted IRE1α, an important regulator of the UPR, through STF-083010 treatment in PDAC cell lines in vitro. Chloroquine was then used to target autophagy and an optimal combination treatment was developed using chloroquine, sunitinib and gemcitabine. Apoptosis was analyzed using TUNEL assay, autophagy was estimated using lysotracker staining and electron microscopy, and UPR was analyzed using anti-GRP78 immunostaining and XBP1 splicing. Transplantation of PDAC derived KPCP1 and Panc02 cells in mouse pancreas were performed to study treatment efficacy in vivo.

Results

Suppression of the IRE1α by STF-083010 alone resulted in increased lysosomes and reduced viability of PDAC cells. Chloroquine treatment alone inhibited downstream autophagy but was insufficient in reducing PDAC cell growth. However, combining STF-083010 and chloroquine had additive anti-tumor efficacy when used with gemcitabine. Sunitinib alone caused abnormal maturation of the autolysosomes with increased intracellular multivesicular bodies and increased apoptosis evident in PDAC cells. Sunitinib showed a synergistic effect with chloroquine in reducing in vitro PDAC cell viability and significantly increased the efficacy of gemcitabine in human and murine PDAC cell lines. The anti-proliferative effect of gemcitabine was significantly increased when used in combination with sunitinib and/or chloroquine in both in vitro and in vivo PDAC models. The addition of sunitinib and/or chloroquine to gemcitabine, resulted in a significantly increased survival of the animals without noticeably increased toxicity. Sunitinib, gemcitabine and chloroquine treated mice showed a significant reduction of GRP78 expression, reduced cell proliferation and increased apoptosis in pancreas, compatible with a tumor response.

Conclusions

Sunitinib combined with chloroquine reduces tumor growth through suppression of autophagy and increased apoptosis. Co-administration of modulators of ER stress-mediated autophagy with chemotherapy presents a novel therapeutic approach in PDAC.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1562-z) contains supplementary material, which is available to authorized users.

Exocytosis of polyubiquitinated proteins in bortezomib-resistant leukemia cells: a role for MARCKS in acquired resistance to proteasome inhibitors

PSMB5 mutations and upregulation of the β5 subunit of the proteasome represent key determinants of acquired resistance to the proteasome inhibitor bortezomib (BTZ) in leukemic cells in vitro. We here undertook a multi-modality (DNA, mRNA, miRNA) array-based analysis of human CCRF-CEM leukemia cells and BTZ-resistant subclones to determine whether or not complementary mechanisms contribute to BTZ resistance. These studies revealed signatures of markedly reduced expression of proteolytic stress related genes in drug resistant cells over a broad range of BTZ concentrations along with a high upregulation of myristoylated alanine-rich C-kinase substrate (MARCKS) gene expression. MARCKS upregulation was confirmed on protein level and also observed in other BTZ-resistant tumor cell lines as well as in leukemia cells with acquired resistance to other proteasome inhibitors. Moreover, when MARCKS protein expression was demonstrated in specimens derived from therapy-refractory pediatric leukemia patients (n = 44), higher MARCKS protein expression trended (p = 0.073) towards a dismal response to BTZ-containing chemotherapy. Mechanistically, we show a BTZ concentration-dependent association of MARCKS protein levels with the emergence of ubiquitin-containing vesicles in BTZ-resistant CEM cells. These vesicles were found to be extruded and taken up in co-cultures with proteasome-proficient acceptor cells. Consistent with these observations, MARCKS protein associated with ubiquitin-containing vesicles was also more prominent in clinical leukemic specimen with ex vivo BTZ resistance compared to BTZ-sensitive leukemia cells. Collectively, we propose a role for MARCKS in a novel mechanism of BTZ resistance via exocytosis of ubiquitinated proteins in BTZ-resistant cells leading to quenching of proteolytic stress.

Global Quantitative Proteomics reveal Deregulation of Cytoskeletal and Apoptotic Signalling Proteins in Oral Tongue Squamous Cell Carcinoma

Oral malignancies remain to have higher morbidity and mortality rates owing to the poor understanding of the carcinogenesis and the lack of early detection and diagnosis. The lack of established biomarkers for oral tongue squamous cell carcinoma (OTSCC) resulted in aggressive multi-modality management less effective. Here, we report for the first time that a panel of potential markers identified from tongue tumor samples using two-dimensional-differential-in-gel-electrophoresis (2D-DIGE). Our approach of combining 2D-DIGE with tandem mass spectrometry identified 24 candidate proteins including cofilins, myosin light chain family members, annexins, serpins, HSPs and tropomyosins, with significant differential expression in tongue carcinomas as compared with their matched adjacent normal tissues. The expression levels of the identified proteins were further validated in larger cohort of Indian samples using qPCR. Most of the differentially regulated proteins are involved in actin cytoskeletal dynamics, drug resistance, immune system, inflammation and apoptotic signalling pathways and are known to play critical role in oral tumorigenesis. Taken together, the results from present investigation provide a valuable base for understanding the development and progression of OTSCC. The validated panel of proteins may be used as potential biomarkers for early detection as well as in predicting therapeutic outcome of OTSCC.

In vitro efficacy of a first-generation valosin-containing protein inhibitor (CB-5083) against canine lymphoma

Valosin-containing protein (VCP), through its critical role in the maintenance of protein homeostasis, is a promising target for the treatment of several malignancies, including canine lymphoma. CB-5083, a first-in-class VCP inhibitor, exerts cytotoxicity through the induction of irreversible proteotoxic stress and possesses a broad spectrum of anticancer activity. Here, we determined the cytotoxicity CB-5083 in canine lymphoma cells and its mechanism of action in vitro. Canine lymphoma cell lines were treated with varying concentrations of CB-5083 and assessed for viability by trypan blue exclusion and apoptosis by caspase activity assays. The mechanism of CB-5083 action was determined by immunoblotting and RT-qPCR analyses of Lys48 ubiquitination and markers of ER stress (DDIT3), autophagy (SQSTM1, MAP1LC3A) and DNA damage (γH2AX). Unfolded protein response markers were also evaluated by immunoblotting (eIF2α, P-eIF2α) and RT-qPCR (ATF4). CB-5083 treatment resulted in preferential cytotoxicity in canine lymphoma cell lines over control peripheral blood mononuclear cells. CB-5083 rapidly disrupted the ubiquitin-dependent protein degradation system, inducing sustained ER stress as indicated by a dramatic increase in DDIT3. Activation of the unfolded protein response occurred through the increase eIF2α phosphorylation and increased transcription of ATF4, but did not re-establish protein homeostasis. Cells rapidly underwent apoptosis through activation of the caspase cascade. These results further validate VCP as an attractive target for the treatment of canine lymphoma and identify CB-5083 as a novel therapy with clinical potential for this malignancy.

Relevance of the chaperone-like protein calreticulin for the biological behavior and clinical outcome of cancer

The death of cancer cells can be categorized as either immunogenic (ICD) or nonimmunogenic, depending on the initiating stimulus. The immunogenic processes of immunogenic cell death are mainly mediated by damage-associated molecular patterns (DAMPs), which include surface exposure of calreticulin (CRT), secretion of adenosine triphosphate (ATP), release of non-histone chromatin protein high-mobility group box 1 (HMGB1) and the production of type I interferons (IFNs). DAMPs are recognized by various receptors that are expressed by antigen-presenting cells (APCs) and potentiate the presentation of tumor antigens to T lymphocytes. Accumulating evidence indicates that CRT exposure constitutes one of the major checkpoints, that determines the immunogenicity of cell death both in vitro and in vivo in mouse models. Moreover, recent studies have identified CRT expression on tumor cells not only as a marker of ICD and active anti-tumor immune reactions but also as a major predictor of a better prognosis in various cancers. Here, we discuss the recent information on the CRT capacity to activate anticancer immune response as well as its prognostic and predictive role for the clinical outcome in cancer patients.

MicroRNAs as predictors for CNS relapse of systemic diffuse large B-cell lymphoma

Systemic diffuse large B-cell lymphoma (DLBCL) is a potentially curable disease using current regimen of immunochemotherapy. Central nervous system (CNS) relapse is a complication that occurs in approximately 5% of DLBCL patients and is associated with a high fatality rate. Early identification of molecular markers for CNS involvement may serve for the highly needed accurate stratification of patients into risk groups regarding CNS relapse. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the post-transcriptional level and are known to be involved in DLBCL pathophysiology. In this study, we utilized miRNA multiplex reading of systemic newly diagnosed DLBCL samples obtained from patients with clinical risk factors for CNS involvement whose disease course was distinguished by the presence or absence of subsequent CNS relapse. The analysis detected two differentially expressed miRNAs, miR-20a and miR-30d, that predict for CNS involvement. Replication of these results in different samples was used for validation. We performed bioinformatics miRNA-target enrichment analysis to reveal a number of putative mechanisms for these miRNAs regulation of CNS relapse, including neuronal plasticity and WNT signaling pathway. Altogether, we show that the expression level of two miRNAs may have valuable information that may refine stratification for patients-at-risk for relapse with CNS involvement in DLBCL. Further larger scale studies are needed to shed light on the pathways involved in this disease.

The Unfolded Protein Response in Immunogenic Cell Death and Cancer Immunotherapy

The unfolded protein response (UPR) is a conserved pathway that is stimulated when endoplasmic reticulum (ER) proteostasis is disturbed or lost. Accumulating evidence indicates that chronic activation of the UPR supports the main hallmarks of cancer by favoring cancer cell-autonomous and nonautonomous processes, which ultimately foster the immunosuppressive and protumorigenic microenvironment. However, certain forms of therapy-induced ER stress can elicit immunogenic cancer cell death (ICD), which enables the release of key immunostimulatory or danger signals, eventually driving efficient antitumor immunity. In this review, after a brief discussion of the interplay between ER stress and protumorigenic inflammation, we review the relevance of therapy-mediated ER stress pathways in evoking ICD and how they could be used to optimize current immunotherapy approaches against cancer.

Synergistic cytotoxic effects of bortezomib and CK2 inhibitor CX-4945 in acute lymphoblastic leukemia: turning off the prosurvival ER chaperone BIP/Grp78 and turning on the pro-apoptotic NF-κB

The proteasome inhibitor bortezomib is a new targeted treatment option for refractory or relapsed acute lymphoblastic leukemia (ALL) patients. However, a limited efficacy of bortezomib alone has been reported. A terminal pro-apoptotic endoplasmic reticulum (ER) stress/unfolded protein response (UPR) is one of the several mechanisms of bortezomib-induced apoptosis. Recently, it has been documented that UPR disruption could be considered a selective anti-leukemia therapy. CX-4945, a potent casein kinase (CK) 2 inhibitor, has been found to induce apoptotic cell death in T-ALL preclinical models, via perturbation of ER/UPR pathway. In this study, we analyzed in T- and B-ALL preclinical settings, the molecular mechanisms of synergistic apoptotic effects observed after bortezomib/CX-4945 combined treatment. We demonstrated that, adding CX-4945 after bortezomib treatment, prevented leukemic cells from engaging a functional UPR in order to buffer the bortezomib-mediated proteotoxic stress in ER lumen. We documented that the combined treatment decreased pro-survival ER chaperon BIP/Grp78 expression, via reduction of chaperoning activity of Hsp90. Bortezomib/CX-4945 treatment inhibited NF-κB signaling in T-ALL cell lines and primary cells from T-ALL patients, but, intriguingly, in B-ALL cells the drug combination activated NF-κB p65 pro-apoptotic functions. In fact in B-cells, the combined treatment induced p65-HDAC1 association with consequent repression of the anti-apoptotic target genes, Bcl-xL and XIAP. Exposure to NEMO (IKKγ)-binding domain inhibitor peptide reduced the cytotoxic effects of bortezomib/CX-4945 treatment. Overall, our findings demonstrated that CK2 inhibition could be useful in combination with bortezomib as a novel therapeutic strategy in both T- and B-ALL.

Diffuse large B-cell lymphoma: R-CHOP failure-what to do?

Although rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) is the standard treatment for patients with diffuse large B-cell lymphoma (DLBCL), ∼30% to 50% of patients are not cured by this treatment, depending on disease stage or prognostic index. Among patients for whom R-CHOP therapy fails, 20% suffer from primary refractory disease (progress during or right after treatment) whereas 30% relapse after achieving complete remission (CR). Currently, there is no good definition enabling us to identify these 2 groups upon diagnosis. Most of the refractory patients exhibit double-hit lymphoma (MYC-BCL2 rearrangement) or double-protein-expression lymphoma (MYC-BCL2 hyperexpression) which have a more aggressive clinical picture. New strategies are currently being explored to obtain better CR rates and fewer relapses. Although young relapsing patients are treated with high-dose therapy followed by autologous transplant, there is an unmet need for better salvage regimens in this setting. To prevent relapse, maintenance therapy with immunomodulatory agents such as lenalidomide is currently undergoing investigation. New drugs will most likely be introduced over the next few years and will probably be different for relapsing and refractory patients.

ON 01910.Na inhibits growth of diffuse large B-cell lymphoma by cytoplasmic sequestration of sumoylated C-MYB/TRAF6 complex

Diffuse large B-cell lymphoma (DLBCL), the most common lymphoma, shows either no response or development of resistance to further treatment in 30% of the patients that warrants the development of novel drugs. We have reported that ON 01910.Na (rigosertib), a multikinase inhibitor, is selectively cytotoxic for DLBCL and induces more hyperphosphorylation and sumoylation of Ran GTPase-activating protein 1 (RanGAP1) in DLBCL cells than in non-neoplastic lymphoblastoid cell line. However, the exact mechanism of rigosertib-induced cell death in DLBCL remains to be clarified. Here, we analyzed the efficacy of rigosertib against DLBCL cells in vitro and in vivo and its molecular effects on tumor biology. We found for the first time that rigosertib attenuated expression of unmodified and sumoylated tumor necrosis factor receptor-associated factor 6 (TRAF6) and c-Myb and inhibited nuclear entry of sumoylated RanGAP1, TRAF6, and c-Myb that was confirmed by immunofluorescence. Moreover, co-immunoprecipitation showed that rigosertib induced sequestration of c-Myb and TRAF6 in the cytoplasm by stimulating their sumoylation through the RanGAP1*SUMO1/Ubc9 pathway. Specific knockdown of c-Myb and TRAF6 induced tumor cell apoptosis and cell cycle arrest at G1 phase. Xenograft mice bearing lymphoma cells also exhibited effective tumor regression on rigosertib treatment along with cytoplasmic expression of c-Myb and TRAF6. Nuclear expression of c-Myb in clinical cases of DLBCL correlated with a poor prognosis. Thus, suppression of c-Myb and TRAF6 activity may have therapeutic implication in DLBCL. These data support the clinical development of rigosertib in DLBCL.

Bortezomib for the treatment of mantle cell lymphoma: an update

Bortezomib is a first in class proteasome inhibitor, initially approved by the US Food and Drug Administration for the treatment of plasma cell myeloma. Bortezomib has been approved for the treatment of relapsed and refractory mantle cell lymphoma (MCL) and, more recently, in the upfront setting as well. Treatment algorithms for MCL have rapidly evolved over the past two decades, and the optimal regimen remains to be defined. The choice of treatment regimen is based on disease risk stratification models, the expected toxicity of antineoplastic agents, the perceived patient ability to tolerate the planned treatments and the availability of novel agents. As new drugs with novel mechanisms of action and variable toxicity profiles come into use, treatment decisions for a given patient have become increasingly complex. This article provides an overview of the evolving use of bortezomib in the rapidly changing management landscape of MCL.

A novel combination treatment for breast cancer cells involving BAPTA-AM and proteasome inhibitor bortezomib

Glucose-regulated protein 78 kDa/binding immunoglobulin protein (GRP78/BIP) is a well-known endoplasmic reticulum (ER) chaperone protein regulating ER stress by facilitating protein folding, assembly and Ca²⁺ binding. GRP78 is also a member of the heat shock protein 70 gene family and induces tumor cell survival and resistance to chemotherapeutics. Bortezomib is a highly specific 26S proteasome inhibitor that has been approved as treatment for patients with multiple myeloma. The present study first examined the dose- and time-dependent effects of bortezomib on GRP78 expression levels in the highly metastatic mouse breast cancer 4T1 cell line using western blot analysis. The analysis results revealed that GRP78 levels were significantly increased by bortezomib at a dose as low as 10 nM. Time-dependent experiments indicated that the accumulation of GRP78 was initiated after a 24 h incubation period following the addition of 10 nM bortezomib. Subsequently, the present study determined the half maximal inhibitory concentration of intracellular calcium chelator BAPTA-AM (13.6 µM) on 4T1 cells. The combination effect of BAPTA-AM and bortezomib on the 4T1 cells was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and WST-1 assays and an iCELLigence system. The results revealed that the combination of 10 nM bortezomib + 5 µM BAPTA-AM is more cytotoxic compared with monotherapies, including 10 nM bortezomib, 1 µM BAPTA-AM and 5 µM BAPTA-AM. In addition, the present results revealed that bortezomib + BAPTA-AM combination causes cell death through the induction of apoptosis. The present results also revealed that bortezomib + BAPTA-AM combination-induced apoptosis is associated with a clear increase in the phosphorylation of stress-activated protein kinase/Jun amino-terminal kinase SAPK/JNK. Overall, the present results suggest that bortezomib and BAPTA-AM combination therapy may be a novel therapeutic strategy for breast cancer treatment.

Elevated GRP78 expression is associated with poor prognosis in patients with pancreatic cancer

Glucose-regulated protein 78 (GRP78) is a member of the heat-shock protein 70 family. We evaluated the expression of GRP78 using tissue microarray-based immunohistochemistry in tumor tissues and adjacent nontumor tissues from 180 pancreatic ductal adenocarcinoma (PDAC) patients. The associations between the expression levels of GRP78, clinicopathological factors, and overall survival were evaluated. The results showed that the expression of GRP78 was significantly higher in PDAC cells than in normal pancreatic duct cells within adjacent nontumor tissues (p < 0.05). The increased expression of GRP78 in the tumor tissues was significantly correlated with a higher T-stage (p < 0.05) and a shorter overall survival (OS, p < 0.05). In an in vitro study, the regulation of GRP78 in the PDAC cell lines affected the proliferation, migration, and invasion of PDAC cells through the regulation of CyclinD1, cyclin-dependent kinase (CDK) 4, CDK6, phospho-signal transducer, activator of transcription 3 (p-STAT3), janus kinase 2 (JAK2), ras homolog gene family member A (RhoA), Rho-associated kinase 1 (ROCK1), and sterile alpha motif domain containing protein 4 (Smad4). The present data suggest that GRP78 plays a crucial role in the proliferation, migration, and invasion of pancreatic cancer cells and may be a suitable prognostic marker in PDAC.

Drugs acting on homeostasis: challenging cancer cell adaptation

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

Prognostic and Predictive Value of DAMPs and DAMP-Associated Processes in Cancer

It is now clear that human neoplasms form, progress, and respond to therapy in the context of an intimate crosstalk with the host immune system. In particular, accumulating evidence demonstrates that the efficacy of most, if not all, chemo- and radiotherapeutic agents commonly employed in the clinic critically depends on the (re)activation of tumor-targeting immune responses. One of the mechanisms whereby conventional chemotherapeutics, targeted anticancer agents, and radiotherapy can provoke a therapeutically relevant, adaptive immune response against malignant cells is commonly known as “immunogenic cell death.” Importantly, dying cancer cells are perceived as immunogenic only when they emit a set of immunostimulatory signals upon the activation of intracellular stress response pathways. The emission of these signals, which are generally referred to as “damage-associated molecular patterns” (DAMPs), may therefore predict whether patients will respond to chemotherapy or not, at least in some settings. Here, we review clinical data indicating that DAMPs and DAMP-associated stress responses might have prognostic or predictive value for cancer patients.

Dual Targeting of Protein Degradation Pathways with the Selective HDAC6 Inhibitor ACY-1215 and Bortezomib Is Synergistic in Lymphoma

PURPOSE

Pan-class histone deacetylase (HDAC) inhibitors are effective treatments for select lymphomas. Isoform-selective HDAC inhibitors are emerging as potentially more targeted agents. HDAC6 is a class IIb deacetylase that facilitates misfolded protein transport to the aggresome for degradation. We investigated the mechanism and therapeutic impact of the selective HDAC6 inhibitor ACY-1215 alone and in combination with bortezomib in preclinical models of lymphoma.

EXPERIMENTAL DESIGN

Concentration-effect relationships were defined for ACY-1215 across 16 lymphoma cell lines and for synergy with bortezomib. Mechanism was interrogated by immunoblot and flow cytometry. An in vivo xenograft model of DLBCL was used to confirm in vitro findings. A collection of primary lymphoma samples were surveyed for markers of the unfolded protein response (UPR).

RESULTS

Concentration-effect relationships defined maximal cytotoxicity at 48 hours with IC50 values ranging from 0.9 to 4.7 μmol/L. Strong synergy was observed in combination with bortezomib. Treatment with ACY-1215 led to inhibition of the aggresome evidenced by acetylated α-tubulin and accumulated polyubiquitinated proteins and upregulation of the UPR. All pharmacodynamic effects were enhanced with the addition of bortezomib. Findings were validated in vivo where mice treated with the combination demonstrated significant tumor growth delay and prolonged overall survival. Evaluation of a collection of primary lymphoma samples for markers of the UPR revealed increased HDAC6, GRP78, and XBP-1 expression as compared with reactive lymphoid tissue.

CONCLUSIONS

These data are the first results to demonstrate that dual targeting of protein degradation pathways represents an innovative and rational approach for the treatment of lymphoma.

Controlling the unfolded protein response-mediated life and death decisions in cancer

Cancer cells are exposed to intrinsic (oncogene) or extrinsic (microenvironmental) challenges, leading to activation of stress response pathways. The unfolded protein response (UPR) is the cellular response to endoplasmic reticulum (ER) stress and plays a pivotal role in tumor development. Depending on ER stress intensity and duration, the UPR is either pro-survival to preserve ER homeostasis or pro-death if the stress cannot be resolved. On one hand, the adaptive arm of the UPR is essential for cancer cells to survive the harsh conditions they are facing, and on the other hand, cancer cells have evolved mechanisms to bypass ER stress-induced cell death, thereby conferring them with a selective advantage for malignant transformation. Therefore, the mechanisms involved in the balance between survival and death outcomes of the UPR may be exploited as therapeutic tools to treat cancer.

Endoplasmic reticulum stress is involved in the lidocaine-induced apoptosis in SH-SY5Y neuroblastoma cells

Lidocaine has been indicated to promote apoptosis and to promote endoplasmic reticulum (ER) stress. However, the mechanism underlining ER stress-mediated apoptosis is unclear. In the present study, we investigated the promotion to ER stress in the lidocaine-induced apoptosis in human neuroblastoma SH-SY5Y cells. Firstly, we confirmed that lidocaine treatment induced apoptosis in SH-SY5Y cells, time-dependently and dose-dependently, via MTT cell viability assay and annexin V/FITC apoptosis detection with a FACScan flow cytometer. And the anti-apoptosis Bcl-2 and Bcl-xL were downregulated, whereas the apoptosis-executive caspase 3 was promoted through Western blot assay and caspase 3 activity assay. Moreover, the ER stress-associated binding immunoglobulin protein (BiP), PKR-like ER kinase (PERK), activating transcription factor 4 (ATF4) and CCAAT/enhancer-binding protein homologous protein (CHOP) were also upregulated at both mRNA and protein levels by lidocaine treatment. On the other hand, downregulation of the ER stress-associated BiP by RNAi method not only blocked the lidocaine-promoted ER stress but also attenuated the lidocaine-induced SH-SY5Y cell apoptosis. In conclusion, the present study confirmed the involvement of ER stress in the lidocaine-induced apoptosis in human neuroblastoma SH-SY5Y cells. Our study provides a better understanding on the mechanism of lidocaine's neurovirulence.

In vivo intratumoral Epstein-Barr virus replication is associated with XBP1 activation and early-onset post-transplant lymphoproliferative disorders with prognostic implications

Post-transplant lymphoproliferative disorders are life-threatening complications following hematopoietic or solid organ transplantation. They represent a spectrum of mostly EBV-driven lymphoplasmacytic proliferations. While the oncogenic effect of EBV is related to latent infection, lytic infection also has a role in lymphomagenesis. In vitro, EBV replication is linked to plasma cell differentiation and XBP1 activation, although this phenomenon has never been addressed in vivo. We analyzed for the first time latent and lytic intratumoral EBV infection in a series of 35 adult patients with a diagnosis of post-transplant lymphoproliferative disorder (26M/9F, median age 54 years). A complete EBV study was performed including the analysis of the latent EBER, latent membrane protein-11, and EBV nuclear antigens as well as the immediate-early BZLF1/ZEBRA and early BMRF1/EADE31 lytic genes. XBP1 activation was assessed by nuclear protein expression. EBV infection was observed in 28 (80%) cases being latency II and III the most frequently observed 22 (79%). Intratumoral EBV replication was detected in 17 (60%) cases. Among these, XBP1 activation was observed in 11/12 evaluable cases associated with strong cytoplasmic immunoglobulin expression consistent with plasma cell differentiation. Intriguingly, the combination of latency III infection and EBV replication identified a high-risk subgroup of patients with significantly shorter survival (overall survival at 1 year 18% vs 48%) and early-onset (median of 7 vs 26 months) post-transplant lymphoproliferative disorder. Moreover, these patients appear to be more heavily immunosuppressed, so they exhibit lower rates of rejection and graft vs host disease but higher rates of cytomegalovirus reactivation. In conclusion, EBV replication is associated with plasma cell differentiation and XBP1 activation with prognostic implications. Both latency III and lytic EBV infection are related to aggressive and early-onset post-transplant lymphoproliferative disorder. These results suggest that immunohistochemical study of latent and lytic EBV genes in the clinical practice may help to select higher-risk patients to new therapies including antiviral treatments.

Stimulation of surface IgM of chronic lymphocytic leukemia cells induces an unfolded protein response dependent on BTK and SYK

B-cell receptor (BCR) signaling plays a key role in the behavior of chronic lymphocytic leukemia (CLL). However, cellular consequences of signaling are incompletely defined. Here we explored possible links between BCR signaling and the unfolded protein response (UPR), a stress response pathway that can promote survival of normal and malignant cells. Compared with normal B cells, circulating CLL cells expressed increased, but variable, levels of UPR components. Higher expression of CHOP and XBP1 RNAs was associated with more aggressive disease. UPR activation appeared due to prior tissue-based antigenic stimulation because elevated expression of UPR components was detected within lymph node proliferation centers. Basal UPR activation also correlated closely with surface immunoglobulin M (sIgM) signaling capacity in vitro in both IGHV unmutated CLL and within mutated CLL. sIgM signaling increased UPR activation in vitro with responders showing increased expression of CHOP and XBP1 RNAs, and PERK and BIP proteins, but not XBP1 splicing. Inhibitors of BCR-associated kinases effectively prevented sIgM-induced UPR activation. Overall, this study demonstrates that sIgM signaling results in activation of some components the UPR in CLL cells. Modulation of the UPR may contribute to variable clinical behavior, and its inhibition may contribute to clinical responses to BCR-associated kinase inhibitors.

Bortezomib for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

Bortezomib , the first proteasome inhibitor (PI) to be evaluated in humans, is approved in the USA and Europe for the treatment of patients with multiple myeloma, and in the USA for patients with relapsed mantle cell lymphoma (MCL).

AREAS COVERED

This review examines the role of bortezomib in the therapy of non-Hodgkin's lymphoma (NHL). Bortezomib may be particularly effective against the NF-κB-dependent activated B-cell subtype of diffuse large B-cell lymphoma. The combination of bortezomib with rituximab and dexamethasone represents a standard approach for the treatment of Waldenström's macroglobulinemia, and that with bendamustine and rituximab has demonstrated excellent efficacy in follicular lymphoma. Combinations with other novel agents, such as inhibitors of cyclin-dependent kinases or histone deacetylases, also hold substantial promise in NHL. Unmet needs in NHL, competitor compounds, chemistry, pharmacokinetics, pharmacodynamics and safety and tolerability of bortezomib are also discussed.

EXPERT OPINION

The success of bortezomib in MCL has validated the proteasome as a therapeutic target in NHL. Rational combinations, for example, with Bruton's tyrosine kinase inhibitors or BH3-mimetics, may hold the key to optimizing the therapeutic potential of PIs in NHL. Future trials are likely to involve newer agents with improved pharmacodynamic (e.g., carfilzomib, marizomib) or pharmacokinetic (e.g., ixazomib, oprozomib) properties.

Triptolide activates unfolded protein response leading to chronic ER stress in pancreatic cancer cells

Pancreatic cancer is a devastating disease with a survival rate of <5%. Moreover, pancreatic cancer aggressiveness is closely related to high levels of prosurvival mediators, which can ultimately lead to rapid disease progression. One of the mechanisms that enables tumor cells to evade cellular stress and promote unhindered proliferation is the endoplasmic reticulum (ER) stress response. Disturbances in the normal functions of the ER lead to an evolutionarily conserved cell stress response, the unfolded protein response (UPR). The UPR initially compensates for damage, but it eventually triggers cell death if ER dysfunction is severe or prolonged. Triptolide, a diterpene triepoxide, has been shown to be an effective compound against pancreatic cancer. Our results show that triptolide induces the UPR by activating the PKR-like ER kinase-eukaryotic initiation factor 2α axis and the inositol-requiring enzyme 1α-X-box-binding protein 1 axis of the UPR and leads to chronic ER stress in pancreatic cancer. Our results further show that glucose-regulated protein 78 (GRP78), one of the major regulators of ER stress, is downregulated by triptolide, leading to cell death by apoptosis in MIA PaCa-2 cells and autophagy in S2-VP10 cells.

Non-Hodgkin's B-cell lymphoma: advances in molecular strategies targeting drug resistance

Non-Hodgkin's lymphoma (NHL) is a heterogeneous class of cancers displaying a diverse range of biological phenotypes, clinical behaviours and prognoses. Standard treatments for B-cell NHL are anthracycline-based combinatorial chemotherapy regimens composed of cyclophosphamide, doxorubicin, vincristine and prednisolone. Even though complete response rates of 40-50% with chemotherapy can be attained, a substantial proportion of patients relapse, resulting in 3-year overall survival rates of about 30%. Relapsed lymphomas are refractory to subsequent treatments with the initial chemotherapy regimen and can exhibit cross-resistance to a wide variety of anticancer drugs. The emergence of acquired chemoresistance thus poses a challenge in the clinic preventing the successful treatment and cure of disseminated B-cell lymphomas. Gene-expression analyses have increased our understanding of the molecular basis of chemotherapy resistance and identified rational targets for drug interventions to prevent and treat relapsed/refractory diffuse large B-cell lymphoma. Acquisition of drug resistance in lymphoma is in part driven by the inherent genetic heterogeneity and instability of the tumour cells. Due to the genetic heterogeneity of B-cell NHL, many different pathways leading to drug resistance have been identified. Successful treatment of chemoresistant NHL will thus require the rational design of combinatorial drugs targeting multiple pathways specific to different subtypes of B-cell NHL as well as the development of personalized approaches to address patient-to-patient genetic heterogeneity. This review highlights the new insights into the molecular basis of chemorefractory B-cell NHL that are facilitating the rational design of novel strategies to overcome drug resistance.

A reappraisal of the diagnostic and therapeutic management of uncommon histologies of primary ocular adnexal lymphoma

Lymphoma is the most common malignancy arising in the ocular adnexa, which includes conjunctiva, lachrymal gland, lachrymal sac, eyelids, orbit soft tissue, and extraocular muscles. Ocular adnexal lymphoma (OAL) accounts for 1%-2% of non-Hodgkin lymphoma and 5%-15% of extranodal lymphoma. Histology, stage, and primary localizations are the most important variables influencing the natural history and therapeutic outcome of these malignancies. Among the various lymphoma variants that could arise in the ocular adnexa, marginal zone B-cell lymphoma (OA-MZL) is the most common one. Other types of lymphoma arise much more rarely in these anatomical sites; follicular lymphoma is the second most frequent histology, followed by diffuse large B-cell lymphoma and mantle cell lymphoma. Additional lymphoma entities, like T-cell/natural killer cell lymphomas and Burkitt lymphoma, only occasionally involve orbital structures. Because they are so rare, related literature mostly consists of anecdotal cases included within series focused on OA-MZL and sporadic case reports. This bias hampers a global approach to clinical and molecular properties of these types of lymphoma, with a low level of evidence supporting therapeutic options. This review covers the prevalence, clinical presentation, behavior, and histological and molecular features of uncommon forms of primary OAL and provides practical recommendations for therapeutic management.

The unfolded protein response regulator GRP78 is a novel predictive biomarker in colorectal cancer

Adjuvant fluoropyrimidine-based (5-FU) chemotherapy is a mainstay of treatment for colorectal cancer (CRC), but only provides benefit for a subset of patients. To improve stratification we examined (for the first time in CRC), whether analysis of GRP78 expression provides a predictive biomarker and performed functional studies to examine the role of GRP78 in sensitivity to 5-FU. 396 CRC patient samples were collected in a prospective uniform manner and GRP78 expression was determined by immunohistochemistry on tissue microarrays using a well-validated antibody. Expression was correlated with clinicopathological parameters and survival. The role of GRP78 in 5-FU sensitivity was examined in CRC cells using siRNA, drug inhibition and flow cytometry. GRP78 expression was significantly elevated in cancer tissue (p < 0.0001), and correlated with depth of invasion (p = 0.029) and stage (p = 0.032). Increased overall 5-year survival was associated with high GRP78 expression (p = 0.036). Patients with stage II cancers treated by surgery alone, with high GRP78 also had improved survival (71% v 50%; p = 0.032). Stage III patients with high GRP78 showed significant benefit from adjuvant chemotherapy (52% vs. 28%; p = 0.026), whereas patients with low GRP78 failed to benefit (28% vs. 32%; p = 0.805). Low GRP78 was an independent prognostic indicator of reduced overall 5-year survival (p = 0.004; HR = 1.551; 95%CI 1.155-2.082). In vitro, inhibition of GRP78 reduces apoptosis in response to 5-FU in p53 wild-type cells. GRP78 expression may provide a simple additional risk stratification to inform the adjuvant treatment of CRC and future studies should combine analysis with determination of p53 status.

Development of a gene expression database and related analysis programs for evaluation of anticancer compounds

Genome-wide transcriptional expression analysis is a powerful strategy for characterizing the biological activity of anticancer compounds. It is often instructive to identify gene sets involved in the activity of a given drug compound for comparison with different compounds. Currently, however, there is no comprehensive gene expression database and related application system that is; (i) specialized in anticancer agents; (ii) easy to use; and (iii) open to the public. To develop a public gene expression database of antitumor agents, we first examined gene expression profiles in human cancer cells after exposure to 35 compounds including 25 clinically used anticancer agents. Gene signatures were extracted that were classified as upregulated or downregulated after exposure to the drug. Hierarchical clustering showed that drugs with similar mechanisms of action, such as genotoxic drugs, were clustered. Connectivity map analysis further revealed that our gene signature data reflected modes of action of the respective agents. Together with the database, we developed analysis programs that calculate scores for ranking changes in gene expression and for searching statistically significant pathways from the Kyoto Encyclopedia of Genes and Genomes database in order to analyze the datasets more easily. Our database and the analysis programs are available online at our website (http://scads.jfcr.or.jp/db/cs/). Using these systems, we successfully showed that proteasome inhibitors are selectively classified as endoplasmic reticulum stress inducers and induce atypical endoplasmic reticulum stress. Thus, our public access database and related analysis programs constitute a set of efficient tools to evaluate the mode of action of novel compounds and identify promising anticancer lead compounds.