Inducing apoptosis in chemotherapy-resistant B-lineage acute lymphoblastic leukaemia cells by targeting HSPA5, a master regulator of the anti-apoptotic unfolded protein response signalling network

Disruption of the Hippo pathway promotes the proliferation of childhood acute lymphoblastic leukemia cells, inhibits apoptosis and chemosensitivity

BACKGROUND

Despite advancements in chemotherapy and stem cell transplantation, the recurrence and chemoresistance of childhood acute lymphoblastic leukemia (cALL) remain a significant challenge, thus indicating the need for novel therapeutic targets.

RESEARCH DESIGN AND METHODS

The protein levels of YAP1, p-YAP1, TAZ, and Cyr61 of cALL patients and healthy volunteers were measured by western blot analysis. Then the leukemic cell line SUP-B15 was transfected with sh-YAP1 and pcDNA3.1-YAP1 to knockdown or overexpress YAP1. The viability, chemosensitivity, apoptosis, migration, and invasion of SUP-B15 cells were determined by MTT, flow cytometry, and Transwell assay.

RESULTS

The cALL patients had higher YAP1, TAZ, and Cyr61 protein expression and lower p-YAP1 protein expression in bone marrow tissues compared with healthy volunteers (p < 0.01). In SUP-B15 cells, YAP1 knockdown upregulated p-YAP1 protein expression (p < 0.01) and downregulated TAZ and Cyr61 protein expression (p < 0.01). In addition, knocking down YAP1 significantly inhibited cell viability, migration, and invasion, and induced apoptosis (p < 0.01). YAP1 knockdown also reduced the IC50 value following treatment with vincristine, daunorubicin, cyclophosphamide, and dexamethasone (p < 0.05).

CONCLUSIONS

Disruption of the Hippo pathway attenuates the development of cALL by promoting cell proliferation while suppressing apoptosis and drug sensitivity.

Multidimensional pan-cancer analysis of HSPA5 and its validation in the prognostic value of bladder cancer

Endoplasmic reticulum (ER) stress-related genes are closely related to the occurrence, development, and immunotherapy response of tumors. This study provides a comprehensive assessment of HSPA5 from a pan-cancer perspective using multi-omics data. We analyzed the function of HSPA5 in multiple tumor types using multiple databases. Finally, immunohistochemistry was used to examine the relationship between HSPA5 expression in tissue microarrays from 100 patients with bladder cancer and the prognosis of patients with bladder cancer. Using the TCGA database, we were able to determine that HSPA5 is significantly elevated in a number of common malignancies and is linked with a bad prognosis. Cox regression analysis showed that the high expression of HSPA5 was correlated with OS, progression free survival (PFS), disease free survival (DFS), and disease special survival (DSS) of adrenocortical carcinoma (ACC). In addition, we discovered significant disparities in HSPA5 methylation and phosphorylation levels between various malignancies and normal tissues. HSPA5 expression was significantly correlated with the levels of infiltrating cells and immune checkpoint genes. HSPA5 is highly expressed in bladder cancer and patients with high HSPA5 expression have a poor prognosis. Our study provides a basis for further understanding of the role of ER stress-related gene HSPA5 in different tumor genesis and development. HSPA5 has also been shown to be a prognostic biomarker for bladder cancer patients.

Cytoplasmic Shotgun Proteomic Points to Key Proteins and Pathways in Temozolomide-Resistant Glioblastoma Multiforme

Temozolomide (TMZ) is the first line of chemotherapy to treat primary brain tumors of the type glioblastoma multiforme (GBM). TMZ resistance (TMZR) is one of the main barriers to successful treatment and is a principal factor in relapse, resulting in a poor median survival of 15 months. The present paper focuses on proteomic analyses of cytosolic fractions from TMZ-resistant (TMZR) LN-18 cells. The experimental workflow includes an easy, cost-effective, and reproducible method to isolate subcellular fraction of cytosolic (CYTO) proteins, mitochondria, and plasma membrane proteins for proteomic studies. For this study, enriched cytoplasmic fractions were analyzed in replicates by nanoflow liquid chromatography tandem high-resolution mass spectrometry (nLC-MS/MS), and proteins identified were quantified using a label-free approach (LFQ). Statistical analysis of control (CTRL) and temozolomide-resistant (TMZR) proteomes revealed proteins that appear to be differentially controlled in the cytoplasm. The functions of these proteins are discussed as well as their roles in other cancers and TMZ resistance in GBM. Key proteins are also described through biological processes related to gene ontology (GO), molecular functions, and cellular components. For protein-protein interactions (PPI), network and pathway involvement analyses have been performed, highlighting the roles of key proteins in the TMZ resistance phenotypes. This study provides a detailed insight into methods of subcellular fractionation for proteomic analysis of TMZ-resistant GBM cells and the potential to apply this approach to future large-scale studies. Several key proteins, protein-protein interactions (PPI), and pathways have been identified, underlying the TMZ resistance phenotype and highlighting the proteins' biological functions.

Polyphyllin I attenuates the invasion and metastasis via downregulating GRP78 in drug-resistant hepatocellular carcinoma cells

Drug resistance to chemotherapy agents presents a major obstacle to the effective treatment of hepatocellular carcinoma (HCC), a common type of liver cancer. Increasing evidence indicates a link between drug resistance and the recurrence of HCC. Polyphyllin I (PPI), a promising pharmaceutical candidate, has shown potential therapeutic advantages in the treatment of sorafenib-resistant hepatocellular carcinoma (SR-HCC cells). In this study, we sought to investigate the mechanism underlying the inhibitory effect of PPI on the invasion and metastasis of SR-HCC cells. Our in vitro studies included scratch wound-healing migration assays and transwell assays to examine PPI's effect on HCC cell migration and invasion. Flow cytometry was employed to analyze the accumulation or efflux of chemotherapy drugs. The results of these experiments demonstrated that PPI increased the susceptibility of HCC to sorafenib while inhibiting SR-HCC cell growth, migration, and invasion. Molecular docking analysis revealed that PPI exhibited a higher binding affinity with GRP78. Western blot analysis and immunofluorescence experiments showed that PPI reduced the expression of GRP78, E-cadherin, N-cadherin, Vimentin, and ABCG2 in SR-HCC cells. Interference with and overproduction of GRP78 in vitro impacted the proliferation, migration, invasion, and metastasis of HCC cells. Further examination revealed that PPI hindered the expression of GRP78 protein, resulting in a suppressive effect on SR-HCC cell migration and invasion. Histological examination of tumor tissue substantiated that administering PPI via gavage to HepG2/S xenograft nude mice inhibited tumor growth and significantly reduced tumor size, as evidenced by xenograft experiments involving nude mice. Hematoxylin and eosin (HE) staining of tumor tissue specimens, along with immunohistochemistry (IHC), were conducted to evaluate the expression levels of Ki67, GRP78, N-cadherin, Vimentin, and ABCG2. The results indicated that PPI administration decreased the levels of proteins associated with metastasis and markers of drug resistance in tumor tissues, impeding tumor growth and spread. Overall, our findings demonstrated that PPI effectively suppressed the viability, proliferation, invasion, and metastasis of SR-HCC cells both in vitro and in vivo by modulating GRP78 activity. These findings provide new insights into the mechanism of PPI inhibition of SR-HCC cell invasion and metastasis, highlighting PPI as a potential treatment option for sorafenib-resistant HCC.

Arginine regulates HSPA5/BiP translation through ribosome pausing in triple-negative breast cancer cells

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with a high mortality rate due to a lack of therapeutic targets. Many TNBC cells are reliant on extracellular arginine for survival and express high levels of binding immunoglobin protein (BiP), a marker of metastasis and endoplasmic reticulum (ER) stress response.

METHODS

In this study, the effect of arginine shortage on BiP expression in the TNBC cell line MDA-MB-231 was evaluated. Two stable cell lines were generated in MDA-MB-231 cells: the first expressed wild-type BiP, and the second expressed a mutated BiP free of the two arginine pause-site codons, CCU and CGU, termed G-BiP.

RESULTS

The results showed that arginine shortage induced a non-canonical ER stress response by inhibiting BiP translation via ribosome pausing. Overexpression of G-BiP in MDA-MB-231 cells promoted cell resistance to arginine shortage compared to cells overexpressing wild-type BiP. Additionally, limiting arginine led to decreased levels of the spliced XBP1 in the G-BiP overexpressing cells, potentially contributing to their improved survival compared to the parental WT BiP overexpressing cells.

CONCLUSION

In conclusion, these findings suggest that the downregulation of BiP disrupts proteostasis during arginine shortage-induced non-canonical ER stress and plays a key role in cell growth inhibition, indicating BiP as a target of codon-specific ribosome pausing upon arginine shortage.

Cell surface GRP78: a potential mechanism of therapeutic resistant tumors

GRP78 is a protein that acts as a chaperone within the endoplasmic reticulum (ER) and has multiple functions. It is induced by stress and abets cells from survival. Despite, multiple Stress conditions like ER, chronic psychological and nutritional stress, hypoxia, chemotherapy, radiation therapy, and drug resistance induce cell surface GRP78 (CS-GRP78) expression in cancer cells. Further, CS-GRP78 is associated with increased malignancy and resistance to anti-cancer therapies and is considered a high-value druggable target. Recent preclinical research suggests that targeting CS-GRP78 with anti-GRP78 monoclonal antibodies (Mab) in combination with other agents may be effective in reversing the failure of chemotherapy, radiotherapy, or targeted therapies and increasing the efficacy of solid tumors treatment. This article will review recent evidence on the role of CS-GRP78 in developing resistance to anti-cancer treatments and the potential benefits of combining anti-GRP78 Mab with other cancer therapies for specific patient populations. Furthermore, our limited understanding of how CS-GRP78 regulated in human studies is a major drawback for designing effective CS-GRP78-targeted therapies. Hence, more research is still warranted to translate these potential therapies into clinical applications.

HSPA5, as a ferroptosis regulator, may serve as a potential therapeutic for head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a ferroptosis sensitive tumor type with high mortality rate. However, it remains largely unknown whether ferroptosis influences the tumor cell in HNSCC.

MATERIALS AND METHODS

To investigate how ferroptosis regulators were differentially expressed between normal and tumor tissue, data related to HNSCC was downloaded from The Cancer Genome Atlas. The expression levels of key factors in HNSCC and the relationship between key factors and ferroptosis in HNSCC were conducted in vitro, and then analyzed to correlate with the differences in prognosis and survival. This was then combined with TNM staging data, and the migration effects of key factors in HNSCC were verified by scratch test and transwell test.

RESULTS

In this study, gene expression analysis and correlation studies between genes showed that HSPA5 was a potentially key associated ferroptosis regulator in HNSCC. Bioinformatics analysis showed that high expression of HSPA5 in HNSCC was positively correlated with poor prognosis and distal metastasis of HNSCC. In vitro immunohistochemistry and western blot tests confirmed that HSPA5 was highly expressed in HNSCC tissues and cell lines. In vitro inhibition of HSPA5 reduced the viability of HNSCC cells and increased ferroptosis. The results of scratch, transwell, and immunofluorescence tests showed that HSPA5 was related to the migration of HNSCC. In addition, a pan-cancer analysis showed that HSPA5 was also overexpressed in many types of cancer with poor prognoses.

CONCLUSION

In total, our study demonstrates the critical role of ferroptosis regulators in HNSCC and that HSPA5, as a ferroptosis regulator, can be regarded as a key molecular target for designing new therapeutic regimens to control HNSCC metastasis and progression.

Osteoprogenitor-GMP crosstalk underpins solid tumor-induced systemic immunosuppression and persists after tumor removal

Remote tumors disrupt the bone marrow (BM) ecosystem (BME), eliciting the overproduction of BM-derived immunosuppressive cells. However, the underlying mechanisms remain poorly understood. Herein, we characterized breast and lung cancer-induced BME shifts pre- and post-tumor removal. Remote tumors progressively lead to osteoprogenitor (OP) expansion, hematopoietic stem cell dislocation, and CD41- granulocyte-monocyte progenitor (GMP) aggregation. The tumor-entrained BME is characterized by co-localization between CD41- GMPs and OPs. OP ablation abolishes this effect and diminishes abnormal myeloid overproduction. Mechanistically, HTRA1 carried by tumor-derived small extracellular vesicles upregulates MMP-13 in OPs, which in turn induces the alterations in the hematopoietic program. Importantly, these effects persist post-surgery and continue to impair anti-tumor immunity. Conditional knockout or inhibition of MMP-13 accelerates immune reinstatement and restores the efficacies of immunotherapies. Therefore, tumor-induced systemic effects are initiated by OP-GMP crosstalk that outlasts tumor burden, and additional treatment is required to reverse these effects for optimal therapeutic efficacy.

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.

Pipeline for Characterizing Alternative Mechanisms (PCAM) based on bi-clustering to study colorectal cancer heterogeneity

The cells of colorectal cancer (CRC) in their microenvironment experience constant stress, leading to dysregulated activity in the tumor niche. As a result, cancer cells acquire alternative pathways in response to the changing microenvironment, posing significant challenges for the design of effective cancer treatment strategies. While computational studies on high-throughput omics data have advanced our understanding of CRC subtypes, characterizing the heterogeneity of this disease remains remarkably complex. Here, we present a novel computational Pipeline for Characterizing Alternative Mechanisms (PCAM) based on biclustering to gain a more detailed understanding of cancer heterogeneity. Our application of PCAM to large-scale CRC transcriptomics datasets suggests that PCAM can generate a wealth of information leading to new biological understanding and predictive markers of alternative mechanisms. Our key findings include: 1) A comprehensive collection of alternative pathways in CRC, associated with biological and clinical factors. 2) Full annotation of detected alternative mechanisms, including their enrichment in known pathways and associations with various clinical outcomes. 3) A mechanistic relationship between known clinical subtypes and outcomes on a consensus map, visualized by the presence of alternative mechanisms. 4) Several potential novel alternative drug resistance mechanisms for Oxaliplatin, 5-Fluorouracil, and FOLFOX, some of which were validated on independent datasets. We believe that gaining a deeper understanding of alternative mechanisms is a critical step towards characterizing the heterogeneity of CRC. The hypotheses generated by PCAM, along with the comprehensive collection of biologically and clinically associated alternative pathways in CRC, could provide valuable insights into the underlying mechanisms driving cancer progression and drug resistance, which could aid in the development of more effective cancer therapies and guide experimental design towards more targeted and personalized treatment strategies. The computational pipeline of PCAM is available in GitHub (https://github.com/changwn/BC-CRC).

Ascendancy of unfolded protein response over glioblastoma: estimating progression, prognosis and survival

Glioblastoma (GBM) is presented with a poor prognosis. The endoplasmic reticulum stress (ERS) has been implicated as a major contributor to disease progression and chemoresistance in GBM. Triggering ERS by chemical agents or genetic modulations is identified as some of the reasons for regulating gene expression and the pathogenesis of GBM. ERS initiates unfolded protein response (UPR), an integrated system useful in restoring homeostasis or inducing apoptosis. Modulation of UPR might have positive outcomes in GBM treatment as UPR inducers have been shown to alter cell survival and migration. In the current review, we have utilized GSE7806, a publicly available dataset from Gene Expression Omnibus (GEO), to evaluate the genes expressed during 6.5 hr and 18 hr, which can be comparable to the early and late-onset of the disease. Subsequently, we have elucidated the prognosis and survival information whilst the expression of these genes in the GBM was noted in previous studies. This is the first of its kind review summarizing the most recent gene information correlating UPR and GBM.

Intrarenal Single-Cell Sequencing of Hepatitis B Virus Associated Membranous Nephropathy

To date, the pathogenesis of hepatitis B virus (HBV)-associated membranous nephropathy (MN) remains elusive. This study aimed to decipher the etiopathogenesis of HBV-associated MN by performing single-cell RNA sequencing (scRNA-seq) of kidney biopsy specimens from a patient with HBV-associated MN and two healthy individuals. We generated 4,114 intrarenal single-cell transcriptomes from the HBV-associated MN patient by scRNA-seq. Compared to healthy individuals, podocytes in the HBV-associated MN patient showed an increased expression of extracellular matrix formation-related genes, including HSPA5, CTGF, and EDIL3. Kidney endothelial cells (ECs) in the HBV-associated MN were enriched in inflammatory pathways, including NF-kappa B signaling, IL-17 signaling, TNF signaling and NOD-like receptor signaling. Gene ontology (GO) functional enrichment analysis and Gene Set Variation Analysis (GSVA) further revealed that differentially expressed genes (DEGs) of ECs from the HBV-associated MN patients were enriched in apoptotic signaling pathway, response to cytokine and leukocyte cell-cell adhesion. The up-regulated DEGs in glomerular ECs of HBV-associated MN patients were involved in biological processes such as viral gene expression, and protein targeting to endoplasmic reticulum. We further verified that the overexpressed genes in ECs from HBV-associated MN were mainly enriched in regulation of protein targeting to endoplasmic reticulum, exocytosis, viral gene expression, IL-6 and IL-1 secretion when compared with anti-phospholipase A2 receptor (PLA2R)-positive idiopathic membranous nephropathy (IMN). The receptor-ligand crosstalk analysis revealed potential interactions between endothelial cells and other cells in HBV-associated-MN. These results offer new insight into the pathogenesis of HBV-associated MN and may identify new therapeutic targets for HBV-associated MN.

Targeting of BCR-ABL1 and IRE1α induces synthetic lethality in Philadelphia-positive acute lymphoblastic leukemia

BCR-ABL1-positive acute lymphoblastic leukemia (ALL) cell survival is dependent on the inositol-requiring enzyme 1 alpha (IRE1α) branch of the unfolded protein response. In the current study, we have focused on exploring the efficacy of a simultaneous pharmacological inhibition of BCR-ABL1 and IRE1α in Philadelphia-positive (Ph+) ALL using tyrosine kinase inhibitor (TKI) nilotinib and the IRE1α inhibitor MKC-8866. The combination of 0.5 µM nilotinib and 30 µM MKC-8866 in Ph+ ALL cell lines led to a synergistic effect on cell viability. To mimic this dual inhibition on a genetic level, pre-B-cells from conditional Xbp1+/fl mice were transduced with a BCR-ABL1 construct and with either tamoxifen-inducible cre or empty vector. Cells showed a significant sensitization to the effect of TKIs after the induction of the heterozygous deletion. Finally, we performed a phosphoproteomic analysis on Ph+ ALL cell lines treated with the combination of nilotinib and MKC-8866 to identify potential targets involved in their synergistic effect. An enhanced activation of p38 mitogen-activated protein kinase α (p38α MAPK) was identified. In line with this findings, p38 MAPK and, another important endoplasmic reticulum-stress-related kinase, c-Jun N-terminal kinase (JNK) were found to mediate the potentiated cytotoxic effect induced by the combination of MKC-8866 and nilotinib since the targeting of p38 MAPK with its specific inhibitor BIRB-796 or JNK with JNK-in-8 hindered the synergistic effect observed upon treatment with nilotinib and MKC-8866. In conclusion, the identified combined action of nilotinib and MKC-8866 might represent a successful therapeutic strategy in high-risk Ph+ ALL.

ER Stress and Unfolded Protein Response in Leukemia: Friend, Foe, or Both?

The unfolded protein response (UPR) is an evolutionarily conserved adaptive signaling pathway triggered by a stress of the endoplasmic reticulum (ER) lumen compartment, which is initiated by the accumulation of unfolded proteins. This response, mediated by three sensors-Inositol Requiring Enzyme 1 (IRE1), Activating Transcription Factor 6 (ATF6), and Protein Kinase RNA-Like Endoplasmic Reticulum Kinase (PERK)—allows restoring protein homeostasis and maintaining cell survival. UPR represents a major cytoprotective signaling network for cancer cells, which frequently experience disturbed proteostasis owing to their rapid proliferation in an usually unfavorable microenvironment. Increased basal UPR also participates in the resistance of tumor cells against chemotherapy. UPR activation also occurs during hematopoiesis, and growing evidence supports the critical cytoprotective role played by ER stress in the emergence and proliferation of leukemic cells. In case of severe or prolonged stress, pro-survival UPR may however evolve into a cell death program called terminal UPR. Interestingly, a large number of studies have revealed that the induction of proapoptotic UPR can also strongly contribute to the sensitization of leukemic cells to chemotherapy. Here, we review the current knowledge on the consequences of the deregulation of UPR signaling in leukemias and their implications for the treatment of these diseases.

3D-printed HA15-loaded β-Tricalcium Phosphate/Poly (Lactic-co-glycolic acid) Bone Tissue Scaffold Promotes Bone Regeneration in Rabbit Radial Defects

In this study, a β-tricalcium phosphate (β-TCP)/poly (lactic-co-glycolic acid) (PLGA) bone tissue scaffold was loaded with osteogenesis-promoting drug HA15 and constructed by three-dimensional (3D) printing technology. This drug delivery system with favorable biomechanical properties, bone conduction function, and local release of osteogenic drugs could provide the basis for the treatment of bone defects. The biomechanical properties of the scaffold were investigated by compressive testing, showing comparable biomechanical properties with cancellous bone tissue. Furthermore, the microstructure, pore morphology, and condition were studied. Moreover, the drug release concentration, the effect of anti-tuberculosis drugs in vitro and in rabbit radial defects, and the ability of the scaffold to repair the defects were studied. The results show that the scaffold loaded with HA15 can promote cell differentiation into osteoblasts in vitro, targeting HSPA5. The micro-computed tomography scans showed that after 12 weeks of scaffold implantation, the defect of the rabbit radius was repaired and the peripheral blood vessels were regenerated. Thus, HA15 can target HSPA5 to inhibit endoplasmic reticulum stress which finally leads to promotion of osteogenesis, bone regeneration, and angiogenesis in the rabbit bone defect model. Overall, the 3D-printed β-TCP/PLGA-loaded HA15 bone tissue scaffold can be used as a substitute material for the treatment of bone defects because of its unique biomechanical properties and bone conductivity.

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.

Unfolded Protein Response in Leukemia: From Basic Understanding to Therapeutic Opportunities

Understanding genetic and epigenetic changes that underlie abnormal proliferation of hematopoietic stem and progenitor cells is critical for development of new approaches to monitor and treat leukemia. The unfolded protein response (UPR) is a conserved adaptive signaling pathway that governs protein folding, secretion, and energy production and serves to maintain protein homeostasis in various cellular compartments. Deregulated UPR signaling, which often occurs in hematopoietic stem cells and leukemia, defines the degree of cellular toxicity and perturbs protein homeostasis, and at the same time, offers a novel therapeutic target. Here, we review current knowledge related to altered UPR signaling in leukemia and highlight possible strategies for exploiting the UPR as treatment for this disease.

The Unfolded Protein Response: A Novel Therapeutic Target in Acute Leukemias

The unfolded protein response (UPR) is an evolutionarily conserved adaptive response triggered by the stress of the endoplasmic reticulum (ER) due, among other causes, to altered cell protein homeostasis (proteostasis). UPR is mediated by three main sensors, protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6α (ATF6α), and inositol-requiring enzyme-1α (IRE1α). Given that proteostasis is frequently disregulated in cancer, UPR is emerging as a critical signaling network in controlling the survival, selection, and adaptation of a variety of neoplasias, including breast cancer, prostate cancer, colorectal cancer, and glioblastoma. Indeed, cancer cells can escape from the apoptotic pathways elicited by ER stress by switching UPR into a prosurvival mechanism instead of cell death. Although most of the studies on UPR focused on solid tumors, this intricate network plays a critical role in hematological malignancies, and especially in multiple myeloma (MM), where treatment with proteasome inhibitors induce the accumulation of unfolded proteins that severely perturb proteostasis, thereby leading to ER stress, and, eventually, to apoptosis. However, UPR is emerging as a key player also in acute leukemias, where recent evidence points to the likelihood that targeting UPR-driven prosurvival pathways could represent a novel therapeutic strategy. In this review, we focus on the oncogene-specific regulation of individual UPR signaling arms, and we provide an updated outline of the genetic, biochemical, and preclinical therapeutic findings that support UPR as a relevant, novel target in acute leukemias.

GJA8 missense mutation disrupts hemichannels and induces cell apoptosis in human lens epithelial cells

Autosomal dominant congenital cataract (ADCC), the most common hereditary disease, is a major cause of eye disease in children. Due to its high genetic and clinical heterogeneity, the identification of ADCC-associated gene mutations is essential for the development of molecular therapies. In this study, we examined a four-generation Chinese pedigree with ADCC and identified putative mutations in ADCC candidate genes via next-generation sequencing (NGS) followed by Sanger sequencing. A novel missense mutation in GJA8 (c.T217C) in ADCC patients causes a serine-to-proline substitution at residue 73 of connexin 50 (Cx50); no mutation was found in unaffected family members and unrelated healthy individuals. Functional analysis revealed that this missense mutation disrupts protein function in human lens epithelial cells (HLEpiCs), which fails to form calcium-sensitive hemichannels. Furthermore, mutant Cx50 leads to decreased ROS scavenging by inhibiting G6PD expression and thus induces cell apoptosis via aberrant activation of the unfolded protein response (UPR). In conclusion, we report a novel GJA8 heterozygous mutation in a Chinese family with a vital role in ADCC, broadening the genetic spectrum of this disease.

The Cytotoxic Effects of Geranylgeranylacetone Are Attenuated in the High-Glucose Condition

Geranylgeranylacetone (GGA) has been used as an antiulcer drug and also is known as inducer of heat shock protein 70 that has cytoprotective effects especially in hyperglycemic condition. In contrast, cytotoxicity of GGA has also been reported. Some studies have reported that GGA suppresses cell growth and induces apoptosis in cell models of human leukemia, ovarian carcinoma, and colon cancer in vitro. Therefore, the aim of this study was to determine whether GGA can have a cytotoxic effect on a human cervical cancer cell line (HeLa), human colorectal adenocarcinoma cells (Caco-2), and human embryonic kidney cells 293 (HEK) in normal-glucose and high-glucose environments (NG and HG, respectively). The results showed that 100 μM GGA inhibited proliferation of HeLa cells only in NG environment despite inhibiting proliferation of Caco-2 and HEK cells regardless of glucose concentration. Cell viability assay revealed that GGA decreased viability of HeLa, Caco-2, and HEK cells only in NG environment. Flow cytometric analyses revealed that the type of cell death was a combination of necrosis and apoptosis. Our study revealed that difference in cytotoxicity of GGA is influenced by glucose condition. The cytotoxic effects of GGA are attenuated in the HG condition. Since both cytotoxic and cytoprotective effects are reported about GGA, further research is needed about the mechanism of the cytotoxic effects.

The interaction between SPARC and GRP78 interferes with ER stress signaling and potentiates apoptosis via PERK/eIF2α and IRE1α/XBP-1 in colorectal cancer

Therapy-refractory disease is one of the main contributors of treatment failure in cancer. In colorectal cancer (CRC), SPARC can function as a sensitizer to conventional chemotherapy by enhancing apoptosis by interfering with the activity of Bcl-2. Here, we examine a novel mechanism by which SPARC further potentiates apoptosis via its modulation of the unfolded protein response (UPR). Using mass spectrometry to identify SPARC-associated proteins, GRP78 was identified as a protein partner for SPARC in CRC. In vitro studies conducted to assess the signaling events resulting from this interaction, included induction of ER stress with tunicamycin, 5-fluorouracil (5-FU), and irinotecan (CPT-11). We found that the interaction between GRP78 and SPARC increased during exposure to 5-FU, CPT-11, and tunicamycin, resulting in an attenuation of GRP78’s inhibition of apoptosis. In addition, we also show that SPARC can sensitize CRC cells to PERK/eIF2α and IRE1α/XBP-1 UPR signaling by interfering with ER stress following binding to GRP78, which leads to ER stress-associated cell death in CRC cells. In line with these findings, a lower expression of GRP78 relative to SPARC in CRC is associated with a lower IC₅₀ for 5-FU in either sensitive or therapy-refractory CRC cells. Interestingly, this observation correlates with tissue microarray analysis of 143 human CRC, where low GRP78 to SPARC expression level was prognostic of higher survival rate (P = 0.01) in individuals with CRC. This study demonstrates that modulation of UPR signaling by SPARC promotes ER stress-associated death and potentiates apoptosis. This may be an effective strategy that can be combined with current treatment options to improve therapeutic efficacy in CRC.

Tumor-secreted GRP78 facilitates the migration of macrophages into tumors by promoting cytoskeleton remodeling

Glucose-regulated protein 78 (GRP78), an important molecular chaperone in the endoplasmic reticulum, is often over-expressed in the central region of advanced tumor and acts as a promoter of tumor progression. As main immune cells in the tumor microenvironment, infiltration of abundant macrophages into advanced tumor further facilitates growth of tumor. Although has potential association between GRP78 and infiltration of macrophages, its underlying mechanisms are poorly understood. Here, we report that secreted GRP78 facilitates recruitment of macrophages into tumors both in vitro and in vivo. Further studies reveal that secreted GRP78 transports into macrophages and bound to intracellular Ca²⁺, which lead to uneven distribution of Ca²⁺ and subsequent polarization of macrophages. The polarization of macrophages activates expression of microRNA-200b-3p. By directly targeting RhoGDI, miR-200b-3p stimulates the activity of RhoGTPase and ultimately leads to the distribution of GTP-Rac1 and GTP-Cdc42 in front protrusion and GTP-RhoA in rear contraction, which further results in migration of macrophages in a certain direction. Our results reveal a novel function of GRP78 to promote the recruitment of macrophages to tumor and provide a potential therapeutic target for malignancies.

Yarrow supercritical extract exerts antitumoral properties by targeting lipid metabolism in pancreatic cancer

Metabolic reprogramming is considered a hallmark of cancer. Currently, the altered lipid metabolism in cancer is a topic of interest due to the prominent role of lipids regulating the progression of various types of tumors. Lipids and lipid-derived molecules have been shown to activate growth regulatory pathways and to promote malignancy in pancreatic cancer. In a previous work, we have described the antitumoral properties of Yarrow (Achillea Millefolium) CO₂ supercritical extract (Yarrow SFE) in pancreatic cancer. Herein, we aim to investigate the underlaying molecular mechanisms by which Yarrow SFE induces cytotoxicity in pancreatic cancer cells. Yarrow SFE downregulates SREBF1 and downstream molecular targets of this transcription factor, such as fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD). Importantly, we demonstrate the in vivo effect of Yarrow SFE diminishing the tumor growth in a xenograft mouse model of pancreatic cancer. Our data suggest that Yarrow SFE can be proposed as a complementary adjuvant or nutritional supplement in pancreatic cancer therapy.

Link between the unfolded protein response and dysregulation of mitochondrial bioenergetics in Alzheimer's disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder affecting more than 47.5 million people worldwide. Metabolic impairments are common hallmarks of AD, and amyloid-β (Aβ) peptide and hyperphosphorylated tau protein—the two foremost histopathological signs of AD—have been implicated in mitochondrial dysfunction. Many neurodegenerative disorders, including AD, show excessive amounts of mis-/unfolded proteins leading to an activation of the unfolded protein response (UPR). In the present study, we aimed to characterize the link between ER stress and bioenergetics defects under normal condition (human SH-SY5Y neuroblastoma cells: control cells) or under pathological AD condition [SH-SY5Y cells overexpressing either the human amyloid precursor protein (APP) or mutant tau (P301L)]. More specifically, we measured UPR gene expression, cell viability, and bioenergetics parameters, such as ATP production and mitochondrial membrane potential (MMP) in basal condition and after an induced ER stress by thapsigargin. We detected highly activated UPR and dysregulated bioenergetics in basal condition in both AD cellular models. Strikingly, acute-induced ER stress increased the activity of the UPR in both AD cellular models, leading to up-regulation of apoptotic pathways, and further dysregulated mitochondrial function.

The Interplay Between Pattern Recognition Receptors and Autophagy in Inflammation

Pattern recognition receptors (PRRs) are sensors of exogenous and endogenous "danger" signals from pathogen-associated molecular patterns (PAMPs), and damage associated molecular patterns (DAMPs), while autophagy can respond to these signals to control homeostasis. Almost all PRRs can induce autophagy directly or indirectly. Toll-like receptors (TLRs), Nod-like receptors (NLRs), retinoic acid-inducible gene-I-like receptors (RLRs), and cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway can induce autophagy directly through Beclin-1 or LC3-dependent pathway, while the interactions with the receptor for advanced glycation end products (RAGE)/high mobility group box 1 (HMGB1), CD91/Calreticulin, and TLRs/HSPs are achieved by protein, Ca2⁺, and mitochondrial homeostasis. Autophagy presents antigens to PRRs and helps to clean the pathogens. In addition, the induced autophagy can form a negative feedback regulation of PRRs-mediated inflammation in cell/disease-specific manner to maintain homeostasis and prevent excessive inflammation. Understanding the interaction between PRRs and autophagy in a specific disease will promote drug development for immunotherapy. Here, we focus on the interactions between PRRs and autophagy and how they affect the inflammatory response.

Comprehensive transcriptomic analysis of heat shock proteins in the molecular subtypes of human breast cancer

BACKGROUND

Heat Shock Proteins (HSPs), a family of genes with key roles in proteostasis, have been extensively associated with cancer behaviour. However, the HSP family is quite large and many of its members have not been investigated in breast cancer (BRCA), particularly in relation with the current molecular BRCA classification. In this work, we performed a comprehensive transcriptomic study of the HSP gene family in BRCA patients from both The Cancer Genome Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohorts discriminating the BRCA intrinsic molecular subtypes.

METHODS

We examined gene expression levels of 1097 BRCA tissue samples retrieved from TCGA and 1981 samples of METABRIC, focusing mainly on the HSP family (95 genes). Data were stratified according to the PAM50 gene expression (Luminal A, Luminal B, HER2, Basal, and Normal-like). Transcriptomic analyses include several statistical approaches: differential gene expression, hierarchical clustering and survival analysis.

RESULTS

Of the 20,531 analysed genes we found that in BRCA almost 30% presented deregulated expression (19% upregulated and 10% downregulated), while of the HSP family 25% appeared deregulated (14% upregulated and 11% downregulated) (|fold change| > 2 comparing BRCA with normal breast tissues). The study revealed the existence of shared HSP genes deregulated in all subtypes of BRCA while other HSPs were deregulated in specific subtypes. Many members of the Chaperonin subfamily were found upregulated while three members (BBS10, BBS12 and CCTB6) were found downregulated. HSPC subfamily had moderate increments of transcripts levels. Various genes of the HSP70 subfamily were upregulated; meanwhile, HSPA12A and HSPA12B appeared strongly downregulated. The strongest downregulation was observed in several HSPB members except for HSPB1. DNAJ members showed heterogeneous expression pattern. We found that 23 HSP genes correlated with overall survival and three HSP-based transcriptional profiles with impact on disease outcome were recognized.

CONCLUSIONS

We identified shared and specific HSP genes deregulated in BRCA subtypes. This study allowed the recognition of HSP genes not previously associated with BRCA and/or any cancer type, and the identification of three clinically relevant clusters based on HSPs expression patterns with influence on overall survival.

Glucose-Related Protein 78 Expression and Its Effects on Cisplatin-Resistance in Cervical Cancer

Background

GRP78, the 78-kDa glucose-regulated protein, occupies a significant position in endoplasmic reticulum stress. Emerging evidences have shown that GRP78 induces chemoresistance in several tumors; however, the role of GRP78 in cervical cancer (CVC) still needs to be elucidated clearly.

Material/Methods

In the present study, we evaluated the expression levels of GRP78 in CVC tissues collected from patients through immunocytochemistry, western blot, and real-time PCR. To explore the exact role of GRP78 in CVC cells in the presence of cisplatin, we generated GRP78 knockdown CVC cells through small interfering RNA. After transfection, the apoptosis rate was assessed by flow cytometry. Then the expression levels of caspase-3, CHOP, and Bcl-2 in GRP78 knockdown cells were determined by western blot.

Results

The GRP78 levels in CVC tissues were increased significantly. Three types of CVC cells HeLa, SiHa, and C33A were treated with different concentrations of cisplatin and cultured for 12 hours, 24 hours, and 48 hours respectively. And SiHa cells exhibited the highest resistance to cisplatin at all time. Specifically, after 25 μM cisplatin treatment, more than 80% of C33A cells underwent apoptosis, whereas the apoptotic rate of SiHa cells was only 30–40%. Data suggested that GRP78 silencing increased chemo-sensitivity and improved the effects of cisplatin-induced apoptosis in SiHa cells. Moreover, inhibition of GRP78 could upregulate caspase-3 and CHOP expression and downregulate Bcl-2 expression.

Conclusions

GRP78 may represent a key bio-marker of CVC and silencing GRP78 may strengthen the resistance against cisplatin. GRP78 may be a potential molecular target for CVC therapies in future.

Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of AIP in the pituitary gland

Despite the well-recognized role of loss-of-function mutations of the aryl hydrocarbon receptor interacting protein gene (AIP) predisposing to pituitary adenomas, the pituitary-specific function of this tumor suppressor remains an enigma. To determine the repertoire of interacting partners for the AIP protein in somatotroph cells, wild-type and variant AIP proteins were used for pull-down/quantitative mass spectrometry experiments against lysates of rat somatotropinoma-derived cells; relevant findings were validated by co-immunoprecipitation and co-localization. Global gene expression was studied in AIP mutation positive and negative pituitary adenomas via RNA microarrays. Direct interaction with AIP was confirmed for three known and six novel partner proteins. Novel interactions with HSPA5 and HSPA9, together with known interactions with HSP90AA1, HSP90AB1 and HSPA8, indicate that the function/stability of multiple chaperone client proteins could be perturbed by a deficient AIP co-chaperone function. Interactions with TUBB, TUBB2A, NME1 and SOD1 were also identified. The AIP variants p.R304* and p.R304Q showed impaired interactions with HSPA8, HSP90AB1, NME1 and SOD1; p.R304* also displayed reduced binding to TUBB and TUBB2A, and AIP-mutated tumors showed reduced TUBB2A expression. Our findings suggest that cytoskeletal organization, cell motility/adhesion, as well as oxidative stress responses, are functions that are likely to be involved in the tumor suppressor activity of AIP.

Therapeutic targeting of membrane-associated GRP78 in leukemia and lymphoma: preclinical efficacy in vitro and formal toxicity study of BMTP-78 in rodents and primates

Translation of drug candidates into clinical settings requires demonstration of preclinical efficacy and formal toxicology analysis for filling an Investigational New Drug (IND) application with the US Food and Drug Administration (FDA). Here, we investigate the membrane-associated glucose response protein 78 (GRP78) as a therapeutic target in leukemia and lymphoma. We evaluated the efficacy of the GRP78-targeted proapoptotic drug bone metastasis targeting peptidomimetic 78 (BMTP-78), a member of the D(KLAKLAK)2-containing class of agents. BMTP-78 was validated in cells from patients with acute myeloid leukemia and in a panel of human leukemia and lymphoma cell lines, where it induced dose-dependent cytotoxicity in all samples tested. Based on the in vitro efficacy of BMTP-78, we performed formal good laboratory practice toxicology studies in both rodents (mice and rats) and nonhuman primates (cynomolgus and rhesus monkeys). These analyses represent required steps towards an IND application of BMTP-78 for theranostic first-in-human clinical trials.

The combination of digoxin and GSK2606414 exerts synergistic anticancer activity against leukemia in vitro and in vivo

Digoxin is a member of cardiac glycosides and recent studies show that digoxin plays anticancer role in several types of cancer. However, the anticancer effects and mechanism of digoxin in leukemia is largely unknown. Her, our data show that digoxin treatment significantly inhibits leukemia cell viability. In addition, digoxin treatment significantly induced apoptosis and G2/M cell cycle arrest in leukemia cells. Furthermore, we demonstrated that digoxin treatment inactivate that oncogenic pathway Akt/mTOR signaling in leukemia cells. In addition, our data show that digoxin treatment induces activation of unfolded protein response (UPR) signaling in leukemia cells. Interestingly, our in vitro and in vivo experiments show that combination treatment of digoxin and UPR inhibitor can synergistically suppress leukemia growth and induces apoptosis and cell cycle arrest compared to single drug treatment. In summary, our findings indicate that digoxin has potential anticancer effects on leukemia. The combination of digoxin and UPR signaling inhibitor can exerts synergistic anticancer activity against leukemia. © 2017 BioFactors, 43(6):812-820, 2017.

HSPA5 Gene encoding Hsp70 chaperone BiP in the endoplasmic reticulum

The HSPA5 gene encodes the binding immunoglobulin protein (BiP), an Hsp70 family chaperone localized in the ER lumen. As a highly conserved molecular chaperone, BiP assists in a wide range of folding processes via its two structural domains, a nucleotide-binding domain (NBD) and substrate-binding domain (SBD). BiP is also an essential component of the translocation machinery for protein import into the ER, a regulator for Ca²⁺ homeostasis in the ER, as well as a facilitator of ER-associated protein degradation (ERAD) via retrograde transportation of aberrant proteins across the ER membrane. When unfolded/misfolded proteins in the ER overwhelm the capacity of protein folding machinery, BiP can initiate the unfolded protein response (UPR), decrease unfolded/misfolded protein load, induce autophagy, and crosstalk with apoptosis machinery to assist in the cell survival decision. Post-translational modifications (PTMs) of BiP have been shown to regulate BiP's activity, turnover, and availability upon different extrinsic or intrinsic stimuli. As a master regulator of ER function, BiP is associated with cancer, cardiovascular disease, neurodegenerative disease, and immunological diseases. BiP has been targeted in cancer therapies and shows promise for application in other relevant diseases.

Characterization of visceral and subcutaneous adipose tissue transcriptome in pregnant women with and without spontaneous labor at term: implication of alternative splicing in the metabolic adaptations of adipose tissue to parturition

OBJECTIVE

The aim of this study was to determine gene expression and splicing changes associated with parturition and regions (visceral vs. subcutaneous) of the adipose tissue of pregnant women.

STUDY DESIGN

The transcriptome of visceral and abdominal subcutaneous adipose tissue from pregnant women at term with (n=15) and without (n=25) spontaneous labor was profiled with the Affymetrix GeneChip Human Exon 1.0 ST array. Overall gene expression changes and the differential exon usage rate were compared between patient groups (unpaired analyses) and adipose tissue regions (paired analyses). Selected genes were tested by quantitative reverse transcription-polymerase chain reaction.

RESULTS

Four hundred and eighty-two genes were differentially expressed between visceral and subcutaneous fat of pregnant women with spontaneous labor at term (q-value <0.1; fold change >1.5). Biological processes enriched in this comparison included tissue and vasculature development as well as inflammatory and metabolic pathways. Differential splicing was found for 42 genes [q-value <0.1; differences in Finding Isoforms using Robust Multichip Analysis scores >2] between adipose tissue regions of women not in labor. Differential exon usage associated with parturition was found for three genes (LIMS1, HSPA5, and GSTK1) in subcutaneous tissues.

CONCLUSION

We show for the first time evidence of implication of mRNA splicing and processing machinery in the subcutaneous adipose tissue of women in labor compared to those without labor.

Tamoxifen-induced cytotoxicity in breast cancer cells is mediated by glucose-regulated protein 78 (GRP78) via AKT (Thr308) regulation

Glucose regulated protein 78 (GRP78) has recently been suggested to be associated with drug resistance in breast cancer patients. However, the precise role of GRP78 in drug resistance and the involved signaling pathways are not clearly understood. In the present study, we show that among a panel of drugs, namely Paclitaxel (TAX), Doxorubicin (DOX), 5-fluorouracil (5-FU), UCN-01 and Tamoxifen (TAM) used, TAM alone up-regulated the expression of GRP78 significantly and induced apoptosis in MCF-7 and MDA-MB-231 cells. Interestingly, inhibition of GRP78 by a specific pharmacological inhibitor, VER-155008 augmented TAM-induced apoptosis, and overexpression of GRP78 rendered the cells resistant to TAM-induced cell death suggesting a role for GRP78 in TAM-induced cytotoxicity. Mechanistically, the expression of phosphorylated AKT as determined by Western blot analyses revealed that TAM selectively upregulated phosphorylation of AKT at Thr308 but not at Ser473, and siRNA silencing of GRP78 resulted in inhibition of AKT phosphorylation at Thr308 but not at Ser473. Further, a GRP78 inhibitor, VER155008 inhibited TAM-induced phosphorylation of GSK3β, a downstream substrate of AKT. These results, thus suggests a role for GRP78 in TAM-induced AKT activation. Additionally, co-localization studies by immunofluorescence, and immunoprecipitation experiments demonstrated a complex formation of AKT and GRP78. Furthermore, in glucose-free medium, the cells were sensitized to TAM-induced cell death that was associated with reduced AKT phosphorylation at Thr308, thus strengthening the association of AKT regulation with drug response. Collectively, our findings identify a role of GRP78 in AKT regulation in response to TAM in breast cancer cells.

Drugging the unfolded protein response in acute leukemias

The unfolded protein response (UPR), an endoplasmic reticulum (ER) stress-induced signaling cascade, is mediated by three major stress sensors IRE-1α, PERK, and ATF6α. Studies described the UPR as a critical network in selection, adaptation, and survival of cancer cells. While previous reviews focused mainly on solid cancer cells, in this review, we summarize the recent findings focusing on acute leukemias. We take into account the impact of the underlying genetic alterations of acute leukemia cells, the leukemia stem cell pool, and provide an outline on the current genetic, clinical, and therapeutic findings. Furthermore, we shed light on the important oncogene-specific regulation of individual UPR signaling branches and the therapeutic relevance of this information to answer the question if the UPR could be an attractive novel target in acute leukemias.

Low Dose Total Body Irradiation Combined With Recombinant CD19-Ligand × Soluble TRAIL Fusion Protein is Highly Effective Against Radiation-Resistant B-Precursor Acute Lymphoblastic Leukemia in Mice

In high-risk remission B-precursor acute lymphoblastic leukemia (BPL) patients, relapse rates have remained high post-hematopoietic stem cell transplantation (HSCT) even after the use of very intensive total body irradiation (TBI)-based conditioning regimens, especially in patients with a high “minimal residual disease” (MRD) burden. New agents capable of killing radiation-resistant BPL cells and selectively augmenting their radiation sensitivity are therefore urgently needed. We report preclinical proof-of-principle that the potency of radiation therapy against BPL can be augmented by combining radiation with recombinant human CD19-Ligand × soluble TRAIL (“CD19L–sTRAIL”) fusion protein. CD19L–sTRAIL consistently killed radiation-resistant primary leukemia cells from BPL patients as well as BPL xenograft cells and their leukemia-initiating in vivo clonogenic fraction. Low dose total body irradiation (TBI) combined with CD19L–sTRAIL was highly effective against (1) xenografted CD19⁺ radiochemotherapy-resistant human BPL in NOD/SCID (NS) mice challenged with an otherwise invariably fatal dose of xenograft cells derived from relapsed BPL patients as well as (2) radiation-resistant advanced stage CD19⁺ murine BPL with lymphomatous features in CD22ΔE12xBCR-ABL double transgenic mice. We hypothesize that the incorporation of CD19L–sTRAIL into the pre-transplant TBI regimens of patients with very high-risk BPL will improve their survival outcome after HSCT.

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CD19L–sTRAIL plus low dose radiation kills leukemia-initiating cells.

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CD19L–sTRAIL plus low dose TBI is very well tolerated in mice.

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CD19L–sTRAIL plus low dose TBI is very effective in mouse models of BPL.

CD22ΔE12 as a molecular target for RNAi therapy

B-precursor acute lymphoblastic leukaemia (BPL) is the most common form of cancer in children and adolescents. Our recent studies have demonstrated that CD22ΔE12 is a characteristic genetic defect of therapy-refractory clones in paediatric BPL and implicated the CD22ΔE12 genetic defect in the aggressive biology of relapsed or therapy-refractory paediatric BPL. The purpose of the present study is to evaluate the biological significance of the CD22ΔE12 molecular lesion in BPL and determine if it could serve as a molecular target for RNA interference (RNAi) therapy. Here we report a previously unrecognized causal link between CD22ΔE12 and aggressive biology of human BPL cells by demonstrating that siRNA-mediated knockdown of CD22ΔE12 in primary leukaemic B-cell precursors is associated with a marked inhibition of their clonogenicity. Additionally, we report a nanoscale liposomal formulation of CD22ΔE12-specific siRNA with potent in vitro and in vivo anti-leukaemic activity against primary human BPL cells as a first-in-class RNAi therapeutic candidate targeting CD22ΔE12.

Endoplasmic reticulum chaperones and oxidoreductases: critical regulators of tumor cell survival and immunorecognition

Endoplasmic reticulum (ER) chaperones and oxidoreductases are abundant enzymes that mediate the production of fully folded secretory and transmembrane proteins. Resisting the Golgi and plasma membrane-directed “bulk flow,” ER chaperones and oxidoreductases enter retrograde trafficking whenever they are pulled outside of the ER by their substrates. Solid tumors are characterized by the increased production of reactive oxygen species (ROS), combined with reduced blood flow that leads to low oxygen supply and ER stress. Under these conditions, hypoxia and the unfolded protein response upregulate their target genes. When this occurs, ER oxidoreductases and chaperones become important regulators of tumor growth. However, under these conditions, these proteins not only promote the folding of proteins, but also alter the properties of the plasma membrane and hence modulate tumor immune recognition. For instance, high levels of calreticulin serve as an “eat-me” signal on the surface of tumor cells. Conversely, both intracellular and surface BiP/GRP78 promotes tumor growth. Other ER folding assistants able to modulate the properties of tumor tissue include protein disulfide isomerase (PDI), Ero1α and GRP94. Understanding the roles and mechanisms of ER chaperones in regulating tumor cell functions and immunorecognition will lead to important insight for the development of novel cancer therapies.

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.

Enhanced antitumor effects of adenoviral-mediated siRNA against GRP78 gene on adenosine-induced apoptosis in human hepatoma HepG2 cells

Our previous studies show that adenosine-induced apoptosis is involved in endoplasmic reticulum stress in HepG2 cells. In this study, we have investigated whether knockdown of GRP78 by short hairpin RNA (shRNA) increases the cytotoxic effects of adenosine in HepG2 cells. The adenovirus vector-delivered shRNA targeting GRP78 (Ad-shGRP78) was constructed and transfected into HepG2 cells. RT-PCR assay was used to determine RNA interference efficiency. Effects of knockdown of GRP78 on adenosine-induced cell viabilities, cell-cycle distribution and apoptosis, as well as relative protein expressions were determined by flow cytometry and/or Western blot analysis. The intracellular Ca2+ concentration was detected by laser scanning confocal microscope. Mitochondrial membrane potential (ΔΨm) was measured by a fluorospectrophotometer. The results revealed that GRP78 mRNA was significantly downregulated by Ad-shGRP78 transfection. Knockdown of GRP78 enhanced HepG2 cell sensitivity to adenosine by modulating G0/G1 arrest and stimulating Bax, Bak, m-calpain, caspase-4 and CHOP protein levels. Knockdown of GRP78 worsened cytosolic Ca2+ overload and ΔΨm loss. Knockdown of caspase-4 by shRNA decreased caspase-3 mRNA expression and cell apoptosis. These findings indicate that GRP 78 plays a protective role in ER stress-induced apoptosis and show that the combination of chemotherapy drug and RNA interference adenoviruses provides a new treatment strategy against malignant tumors.

Treating relapsed or refractory Philadelphia chromosome-negative acute lymphoblastic leukemia: liposome-encapsulated vincristine

Acute lymphoblastic leukemia (ALL) remains a disease with poor outcomes in adults. While induction chemotherapy achieves a complete remission in almost 90% of patients, the majority will relapse and die of their disease. Relapsed ALL is associated with a high reinduction mortality and chemotherapy resistance, with allogeneic hematopoietic stem cell transplantation offering the only therapy with curative potential. However, there is no efficacious and well tolerated standard regimen accepted as a “bridge” to allogeneic stem cell transplantation or as definitive treatment for patients who are not transplant candidates. Vincristine is an active drug in patients with ALL, but its dose intensity is limited by neurotoxicity, and its full potential as an anticancer drug is thus not realized. Encapsulation of vincristine into sphingomyelin and cholesterol nanoparticle liposomes facilitates dose-intensification and densification to enhanced target tissues with reduced potential for toxicity. Vincristine sulfate liposome injection (VSLI) is associated with significant responses in clinically advanced ALL, and has recently been approved by the US Food and Drug Administration for treatment of relapsed and clinically advanced Philadelphia chromosome-negative ALL. This review provides an overview of the preclinical and clinical studies leading to the approval of VSLI for the treatment of relapsed and refractory ALL, and suggests potential areas of future clinical development.

Induction of the unfolded protein response drives enhanced metabolism and chemoresistance in glioma cells

The unfolded protein response (UPR) is an endoplasmic reticulum (ER)-based cytoprotective mechanism acting to prevent pathologies accompanying protein aggregation. It is frequently active in tumors, but relatively unstudied in gliomas. We hypothesized that UPR stress effects on glioma cells might protect tumors from additional exogenous stress (ie, chemotherapeutics), postulating that protection was concurrent with altered tumor cell metabolism. Using human brain tumor cell lines, xenograft tumors, human samples and gene expression databases, we determined molecular features of glioma cell UPR induction/activation, and here report a detailed analysis of UPR transcriptional/translational/metabolic responses. Immunohistochemistry, Western and Northern blots identified elevated levels of UPR transcription factors and downstream ER chaperone targets in gliomas. Microarray profiling revealed distinct regulation of stress responses between xenograft tumors and parent cell lines, with gene ontology and network analyses linking gene expression to cell survival and metabolic processes. Human glioma samples were examined for levels of the ER chaperone GRP94 by immunohistochemistry and for other UPR components by Western blotting. Gene and protein expression data from patient gliomas correlated poor patient prognoses with increased expression of ER chaperones, UPR target genes, and metabolic enzymes (glycolysis and lipogenesis). NMR-based metabolomic studies revealed increased metabolic outputs in glucose uptake with elevated glycolytic activity as well as increased phospholipid turnover. Elevated levels of amino acids, antioxidants, and cholesterol were also evident upon UPR stress; in particular, recurrent tumors had overall higher lipid outputs and elevated specific UPR arms. Clonogenicity studies following temozolomide treatment of stressed or unstressed cells demonstrated UPR-induced chemoresistance. Our data characterize the UPR in glioma cells and human tumors, and link the UPR to chemoresistance possibly via enhanced metabolism. Given the role of the UPR in the balance between cell survival and apoptosis, targeting the UPR and/or controlling metabolic activity may prove beneficial for malignant glioma therapeutics.