Compounds Triggering ER Stress Exert Anti-Melanoma Effects and Overcome BRAF Inhibitor Resistance

Targeting GRP78 suppresses oncogenic KRAS protein expression and reduces viability of cancer cells bearing various KRAS mutations

KRAS is the most commonly mutated oncogene in human cancers with limited therapeutic options, thus there is a critical need to identify novel targets and inhibiting agents. The 78-kDa glucose-regulated protein GRP78, which is upregulated in KRAS cancers, is an essential chaperone and the master regulator of the unfolded protein response (UPR). Following up on our recent discoveries that GRP78 haploinsufficiency suppresses both KRASG12D-driven pancreatic and lung tumorigenesis, we seek to determine the underlying mechanisms. Here, we report that knockdown of GRP78 via siRNA reduced oncogenic KRAS protein level in human lung, colon, and pancreatic cancer cells bearing various KRAS mutations. This effect was at the post-transcriptional level and is independent of proteasomal degradation or autophagy. Moreover, targeting GRP78 via small molecule inhibitors such as HA15 and YUM70 with anti-cancer activities while sparing normal cells significantly suppressed oncogenic KRAS expression in vitro and in vivo, associating with onset of apoptosis and loss of viability in cancer cells bearing various KRAS mutations. Collectively, our studies reveal that GRP78 is a previously unidentified regulator of oncogenic KRAS expression, and, as such, augments the other anti-cancer activities of GRP78 small molecule inhibitors to potentially achieve general, long-term suppression of mutant KRAS-driven tumorigenesis.

Dissecting the Immunological Profiles in NSD3-Amplified LUSC through Integrative Multi-Scale Analyses

Simple Summary

Although cancer immunotherapy has become a “game changer” in treating LUSC patients, challenges still prevail due to the heterogeneous response and insufficient predictive biomarkers. Recently, NSD3, a neighbor gene of FGFR1, was identified as a key genetic driver of LUSC tumorigenesis. While previous studies have reported the relevance of NSD3 in innate antiviral immunity, the association of NSD3 with the TIME remains an open question requiring further investigation. We first show that NSD3 gene amplification is associated with an immune-desert phenotype and correlated with a worse immunotherapy outcome. Further molecular characterizations pinpoint that the high activity of UPR signaling might be a pivotal mediator for the non-inflamed TME phenotype of NSD3-amplified LUSC. Concordantly, the pharmaco-transcriptomic correlation analysis indicated that the intervention of UPR signaling could be a promising synthetic lethality target for NSD3-amplified LUSC. Our findings reveal a previously unappreciated immunological role for NSD3 in LUSC pathobiology and provide therapeutic rationales for this daunting disease.

Abstract

The histone H3 lysine 36 (H3K36) methyltransferase NSD3, a neighboring gene of FGFR1, has been identified as a critical genetic driver of lung squamous cell carcinoma (LUSC). However, the molecular characteristics, especially the immunological roles of NSD3 in driving carcinogenesis, are poorly understood. In this study, we systematically integrated multi-omics data (e.g., genome, transcriptome, proteome, and TMA array) to dissect the immunological profiles in NSD3-amplified LUSC. Next, pharmaco-transcriptomic correlation analysis was implemented to identify the molecular underpinnings and therapeutic vulnerabilities in LUSC. We revealed that NSD3-amplified LUSC presents a non-inflamed tumor immune microenvironment (TIME) state in multiple independent LUSC patient cohorts. Predictably, elevated NSD3 expression was correlated with a worse immunotherapy outcome. Further molecular characterizations revealed that the high activity of unfolded protein response (UPR) signaling might be a pivotal mediator for the non-immunogenic phenotype of NSD3-amplified LUSC. Concordantly, we showed that NSD3-amplified LUSCs exhibited a more sensitive phenotype to compounds targeting UPR branches than the wild-type group. In brief, our multi-level analyses point to a previously unappreciated immunological role for NSD3 and provide therapeutic rationales for NSD3-amplified squamous lung cancer.

Low Concentrations of Oxidized Phospholipids Increase Stress Tolerance of Endothelial Cells

Oxidized phospholipids (OxPLs) are generated by enzymatic or autooxidation of esterified polyunsaturated fatty acids (PUFAs) residues. OxPLs are present in circulation and atherosclerotic plaques where they are thought to induce predominantly proinflammatory and toxic changes in endothelial (ECs) and other cell types. Unexpectedly, we found that low concentrations of OxPLs were not toxic but protected ECs from stress induced by serum deprivation or cytostatic drugs. The protective effect was observed in ECs obtained from different vessels and was monitored using a variety of readouts based on different biological and chemical principles. Analysis of the structure−activity relationship identified oxidized or missing fatty acid residue (OxPLs or Lyso-PLs, respectively) as a prerequisite for the protective action of a PL. Protective OxPLs or Lyso-PLs acquired detergent-like properties and formed in solution aggregates <10 nm in diameter (likely micelles), which were in striking contrast with large aggregates (>1000 nm, likely multilayer liposomes) produced by nonoxidized precursor PLs. Because surfactants, OxPLs, and Lyso-PLs are known to extract membrane cholesterol, we tested if this effect might trigger the protection of endothelial cells. The protective action of OxPLs and Lyso-PLs was inhibited by cotreatment with cholesterol and mimicked by cholesterol-binding beta-cyclodextrin but not inactive α-cyclodextrin. Wide-scale mRNA expression analysis in four types of ECs showed the induction of genes encoding for heat shock proteins (HSPs) and secreted prosurvival peptides and proteins. Inducers of HSPs, chemical chaperones, and pure prosurvival factors mimicked the protective action of OxPLs/Lyso-PLs. We hypothesize that oxidation changes the physicochemical properties of PLs, thus promoting membrane cholesterol redistribution or extraction leading to the expression of intra- and extracellular prosurvival factors.

Bromodomain inhibition overcomes treatment resistance in distinct molecular subtypes of melanoma

Therapy of BRAF-mutant melanoma with selective inhibitors of BRAF (BRAFi) and MEK (MEKi) represents a major clinical advance but acquired resistance to therapy has emerged as a key obstacle. To date, no clinical approaches successfully resensitize to BRAF/MEK inhibition. Here, we develop a therapeutic strategy for melanoma using bromosporine, a bromodomain inhibitor. Bromosporine (bromo) monotherapy produced significant anti-tumor effects against established melanoma cell lines and patient-derived xenografts (PDXs). Combinatorial therapy involving bromosporine and cobimetinib (bromo/cobi) showed synergistic anti-tumor effects in multiple BRAFi-resistant PDX models. The bromo/cobi combination was superior in vivo to standard BRAFi/MEKi therapy in the treatment-naive BRAF-mutant setting and to MEKi alone in the setting of immunotherapy-resistant NRAS- and NF1-mutant melanoma. RNA sequencing of xenografts treated with bromo/cobi revealed profound down-regulation of genes critical to cell division and mitotic progression. Bromo/cobi treatment resulted in marked DNA damage and cell-cycle arrest, resulting in induction of apoptosis. These studies introduce bromodomain inhibition, alone or combined with agents targeting the mitogen activated protein kinase pathway, as a rational therapeutic approach for melanoma refractory to standard targeted or immunotherapeutic approaches.

GRP78 plays a key role in sperm function via the PI3K/PDK1/AKT pathway

Glucose-regulated protein 78 (GRP78), which is commonly found in the endoplasmic reticulum (ER), is involved in stabilizing ER proteins and inducing the unfolded protein response. Furthermore, GRP78 is expressed on the surface of most common cancer cells, such as cells of breast, lung, liver, and prostate cancers, and plays a role in apoptosis and cell proliferation via the PI3K/PDK1/AKT signaling pathway. Therefore, various trials have been performed for evaluating cancer treatment by inhibiting GRP78. Moreover, GRP78 is expressed on the surface of spermatozoa; however, its role in spermatozoa physiology remains unclear. Therefore, this study was designed to investigate the effects of GRP78 on sperm function during capacitation and elucidate the underlying mechanisms. Boar spermatozoa were exposed to various concentrations of HA15, a GRP78 antagonist, and sperm kinematic parameters, capacitation status, cell viability, levels of PI3K/PDK1/AKT-pathway related proteins, and tyrosine phosphorylation were evaluated. GRP78 inhibition significantly decreased sperm motility, kinematic parameters, capacitated and acrosome-reacted spermatozoa counts, and cell viability. Moreover, GRP78 expression was significantly decreased in HA15-treated spermatozoa compared to that in the control group, and levels of PI3K/PDK1/AKT-pathway related proteins changed significantly. Furthermore, tyrosine phosphorylation was significantly altered in the HA15-treated group. The results of this study suggest that GRP78 inhibition in cancer therapy may negatively affect sperm function. These results lay a strong foundation for future studies aiming to identify the molecular mechanisms related to GRP78 in spermatozoa.

HSPA5 Inhibitor Meliorate DSS-Induced Colitis through HSPA1A/CHIP

Objective

Ulcerative colitis (UC) is closely related to immune response, in which Treg cells (Tregs) suppress the autoimmune response of effector T cells to maintain homeostasis. As a marker of endoplasmic reticulum stress (ERS), HSPA5 was highly expressed in the colon tissue of UC patients. This study is aimed at evaluating the therapeutic effect of HSPA5 inhibitor (HA15) on dextran sulfate sodium- (DSS-) induced ulcerative colitis in mice and explored the effect and related mechanism of HSPA5 inhibitor on the differentiation and function of Tregs.

Methods

Thirty-two C57BL/6 mice were randomly divided into four groups (8 mice per group): normal control group, DSS model group, HSPA5 inhibitor (HA15) group (intraperitoneal injection), and dexamethasone (DXM) group (intraperitoneal injection). Except for the blank control group, the other groups were induced with 3% DSS for 7 days and then given corresponding intervention therapy for 7 days.

Results

The disease activity index (DAI) score, colon length, histopathological changes, and scores of DSS-induced mice show that HA15 could significantly improve the degree of inflammation in ulcerative colitis. Moreover, HA15 can better inhibit the expression of HSPA5, HSPA1A, and CHIP in the colon and increase the level of FOXP3 mRNA. Finally, the content of Treg cells and the levels of IL-10 and TGF-β1 were significantly increased, and the levels of IL-6 were significantly reduced.

Conclusions

HA15 can improve the differentiation and function of Treg cells by inhibiting the HSPA1A/CHIP pathway, thereby improving ulcerative colitis. Therefore, inhibiting the expression of HSPA5 may serve as a new approach to treat ulcerative colitis.

Nanodrugs Manipulating Endoplasmic Reticulum Stress for Highly Effective Antitumor Therapy

Cancer is one of the leading causes of death worldwide due to high morbidity and mortality. Many attempts and efforts have been devoted to fighting cancer. Owing to the significant role of the endoplasmic reticulum (ER) in cell function, inducing ER stress can be promising for cancer treatment. However, the sustained activation of cytoprotective unfolded protein response (UPR) presents a tremendous obstacle for drugs in inducing unsolved ER stress in tumor cells, especially small-molecule drugs with poor bioavailability. Therefore, many emerging nanodrugs inducing and amplifying ER stress have been developed for efficient cancer treatment. More importantly, the novel discovery of ER stress in immunogenic cell death (ICD) makes it possible to repurpose antitumor drugs for immunotherapy through nanodrug-based strategies amplifying ER stress. Therefore, this mini-review aims to provide a comprehensive summary of the latest developments of the strategies underlying nanodrugs in the treatment of cancer via manipulating ER stress. Meanwhile, the prospects of ER stress–inducing nanodrugs for cancer treatment are systematically discussed, which provide a sound platform for novel therapeutic insights and inspiration for the design of nanodrugs in treating cancer.

Target Profiling of an Iridium(III)-Based Immunogenic Cell Death Inducer Unveils the Engagement of Unfolded Protein Response Regulator BiP

Clinical chemotherapeutic drugs have occasionally been observed to induce antitumor immune responses beyond the direct cytotoxicity. Such effects are coined as immunogenic cell death (ICD), representing a "second hit" from the host immune system to tumor cells. Although chemo-immunotherapy is highly promising, ICD inducers remain sparse with vague drug-target mechanisms. Here, we report an endoplasmic reticulum stress-inducing cyclometalated Ir(III)-bisNHC complex (1a) as a new ICD inducer, and based on this compound, a clickable photoaffinity probe was designed for target identification, which unveiled the engagement of the master regulator protein BiP (binding immunoglobulin protein)/GRP78 of the unfolded protein response pathway. This has been confirmed by a series of cellular and biochemical studies including fluorescence microscopy, cellular thermal shift assay, enzymatic assays, and so forth, showing the capability of 1a for BiP destabilization. Notably, besides 1a, the previously reported ICD inducers including KP1339, mitoxantrone, and oxaliplatin were also found to engage BiP interaction, suggesting the important role of BiP in eliciting anticancer immunity. We believe that the ICD-related target information in this work will help to understand the mode of action of ICD that is beneficial to designing new ICD agents with high specificity and improved efficacy.

Evolution of Chemical Research in Nice, Côte d'Azur: From Early Laboratories to the 'Institut de Chimie de Nice'

The 'Institut de Chimie de Nice' (ICN), founded in 2012, celebrates its 10th anniversary in 2022. Today, the ICN is part of the University Côte d'Azur (UCA), one out of nine excellence universities in France. ICN is also affiliated to the CNRS. We use the institute's anniversary to reflect on the origins and the successful evolution of research in chemical sciences in Nice, France. We outline research topics and their development towards modern chemistry in Nice that are characterized by innovation and territorial anchoring. At present, four research axes, namely aroma and perfume chemistry, medicinal chemistry, radiochemistry, and material chemistry structure the institute. ICN has created five start-up companies and includes a technological platform. The ICN is central part of the university and contributes to the advancement in chemical sciences as evidenced by both fundamental research and active contributions to local partnerships.

Autophagic and apoptotic cell death induced by the quinoline derivative 2-(6-methoxynaphthalen-2-yl)quinolin-4-amine in pancreatic cancer cells is via ER stress and inhibition of Akt/mTOR signaling pathway

Pancreatic cancer (PC) is among the most lethal cancers and is resistant to existing therapies, which highlights the need for new and alternative therapeutic treatments. Autophagy is emerging as one of the alternative cell death mechanisms and is well known to cross-talk with apoptosis. Autophagy can act as a viable option to treat highly resistant PC. The current study investigates and provides insight into the autophagic and apoptotic cell death induced by quinoline derivative 2-(6-methoxynaphthalen-2-yl)quinolin-4-amine (6MN-4-AQ) in PC cell lines PANC-1 and MIA PaCa-2. Treatment with 6MN-4-AQ reduced cell viability in concentration dependent manner (2-16 μM) and inhibited the clonogenic potential of PC cells at a concentration of 4 μM for 24 h. Further, we found that 6MN-4-AQ induced both apoptosis and autophagic cell death simultaneously. We identified that 6MN-4-AQ induced autophagic cell death by forming cytoplasmic vacuoles, the elevation of autophagy flux, increase in LC3-II, Beclin-1 protein expression, and degradation of p62. Moreover, 6MN-4-AQ induced apoptosis via Caspase-3 activation and cleavage of PARP in PC cells. Upon investigating the underlying mechanism associated with 6MN-4-AQ induced cell death, it was observed that 6MN-4-AQ treatment is able to suppress the Akt/mTOR pathway and induced ER stress leading to the induction of autophagy. Also, 6MN-4-AQ treatment suppressed epithelial to mesenchymal transition by reducing the protein expression of SLUG, snail, and vimentin. Subsequently, 6MN-4-AQ inhibited cell migration and invasion by down regulating MMP-7 and MMP-9 protein expression, suggesting that 6MN-4-AQ may serve as a plausible therapeutic agent for PC.

Combination Strategies Involving Immune Checkpoint Inhibitors and Tyrosine Kinase or BRAF Inhibitors in Aggressive Thyroid Cancer

Thyroid cancer is the most common (~90%) type of endocrine-system tumor, accounting for 70% of the deaths from endocrine cancers. In the last years, the high-throughput genomics has been able to identify pathways/molecular targets involved in survival and tumor progression. Targeted therapy and immunotherapy individually have many limitations. Regarding the first one, although it greatly reduces the size of the cancer, clinical responses are generally transient and often lead to cancer relapse after initial treatment. For the second one, although it induces longer-lasting responses in cancer patients than targeted therapy, its response rate is lower. The individual limitations of these two different types of therapies can be overcome by combining them. Here, we discuss MAPK pathway inhibitors, i.e., BRAF and MEK inhibitors, combined with checkpoint inhibitors targeting PD-1, PD-L1, and CTLA-4. Several mutations make tumors resistant to treatments. Therefore, more studies are needed to investigate the patient's individual tumor mutation burden in order to overcome the problem of resistance to therapy and to develop new combination therapies.

Cucurbitacin B-induced G2/M cell cycle arrest of conjunctival melanoma cells mediated by GRP78–FOXM1–KIF20A pathway

Conjunctival melanoma (CM) is a rare and fatal malignant eye tumor. In this study, we deciphered a novel anti-CM mechanism of a natural tetracyclic compound named as cucurbitacin B (CuB). We found that CuB remarkably inhibited the proliferation of CM cells including CM-AS16, CRMM1, CRMM2 and CM2005.1, without toxicity to normal cells. CuB can also induce CM cells G2/M cell cycle arrest. RNA-seq screening identified KIF20A, a key downstream effector of FOXM1 pathway, was abolished by CuB treatment. Further target identification by activity-based protein profiling chemoproteomic approach revealed that GRP78 is a potential target of CuB. Several lines of evidence demonstrated that CuB interacted with GRP78 and bound with a K_d value of 0.11 μmol/L. Furthermore, ATPase activity evaluation showed that CuB suppressed GRP78 both in human recombinant GRP78 protein and cellular lysates. Knockdown of the GRP78 gene significantly induced the downregulation of FOXM1 and related pathway proteins including KIF20A, underlying an interesting therapeutic perspective. Finally, CuB significantly inhibited tumor progression in NCG mice without causing obvious side effects in vivo. Taken together, our current work proved that GRP78–FOXM1–KIF20A as a promising pathway for CM therapy, and the traditional medicine CuB as a candidate drug to hinder this pathway.

Canine osteosarcoma cells exhibit basal accumulation of multiple chaperone proteins and are sensitive to small molecule inhibitors of GRP78 and heat shock protein function

Osteosarcoma is the most common type of bone cancer in dogs and humans, with significant numbers of patients experiencing treatment failure and disease progression. In our search for new approaches to treat osteosarcoma, we previously detected multiple chaperone proteins in the surface-exposed proteome of canine osteosarcoma cells. In the present study, we characterized expression of representative chaperones and find evidence for stress adaptation in canine osteosarcoma cells relative to osteogenic progenitors from normal bone. We compared the cytotoxic potential of direct (HA15) and putative (OSU-03012) inhibitors of Grp78 function and found canine POS and HMPOS osteosarcoma cells to be more sensitive to both compounds than normal cells. HA15 and OSU-03012 increased the thermal stability of Grp78 in intact POS cells at low micromolar concentrations, but each induced distinct patterns in Grp78 expression without significant change in Grp94. Both inhibitors were as effective alone as carboplatin and showed little evidence of synergy in combination treatment. However, HMPOS cells with acquired resistance to carboplatin were sensitive to inhibition of Grp78 (by HA15; OSU-03012), Hsp70 (by VER-155008), and Hsp90 (by 17-AAG) function. These results suggest that multiple nodes within the osteosarcoma chaperome may be relevant chemotherapeutic targets against platinum resistance.

A novel small-molecule activator of unfolded protein response suppresses castration-resistant prostate cancer growth

Androgen receptor-targeted therapy improves survival in castration-resistant prostate cancer (CRPC). However, almost all patients with CRPC eventually develop secondary resistance to these drugs. Therefore, alternative therapeutic approaches for incurable metastatic CRPC are urgently needed. Unfolded protein response (UPR) is regarded as a cytoprotective mechanism that removes misfolded proteins in rapidly proliferating tumor cells. However, acute activation of the UPR directly leads to tumor cell death. This study has shown that WJ-644A, a novel small molecule activator of UPR, potently inhibited the proliferation of prostate cancer cells and caused tumor regression with a good safety profile in multiple animal models. Mechanistically, we have identified that WJ-644A induced cell methuosis and autophagy upon UPR activation. Our study not only identifies the UPR as an actionable target for CRPC treatment, but also establishes WJ-644A as a novel UPR activator that has potential therapeutic value for CRPC.

Small Molecule Modifications Significantly Increase the Transfection Efficiency of Low-Molecular Polymer

Gene vectors with high biocompatibility and transfection efficiency are critical for successful gene therapy. PEI 25K (Polyethyleneimine 25K) is a common polymeric gene vector that has been employed as a positive control material in gene transfection studies due to its good performance in endosome escape. PEI 25K's indegradability and abundance of positive charges, on the other hand, cause toxicity in cells, limiting its use. In this study, we developed the PEI-ER non-viral vector by adding an endoplasmic reticulum (ER) targeting ligand to low molecular weight PEI 1.8K. These small molecule modifications dramatically improved PEI transfection efficiency while barely interfering with compatibility. PEI-ER/DNA complexes were discovered to enter the cell via caveolin-mediated endocytosis, avoiding destruction in the endosome. We believe that this little chemical alteration is a simple solution to enhance the efficacy of cationic polymer vectors in gene transport, and it has a lot of medicinal applications.

Increase in the sensitivity to PLX4720 through inhibition of transcription factor EB-dependent autophagy in BRAF inhibitor-resistant cells

Long-term treatment with oncogenic BRAF inhibitors confers resistance to BRAF inhibitor monotherapy. In this study, a combination treatment strategy with autophagy inhibitors was proposed to increase the sensitivity of BRAF mutant containing A375P melanoma cells that have developed resistance to BRAF inhibitors. We found that the A375P/Multi-drug resistance (A375P/Mdr) cells, which are resistant to both BRAF inhibitors and MEK inhibitors, exhibited a higher basal autophagic flux compared to their parental A375P cells, as determined by tandem mRFP-GFP-tagged LC3 imaging assay and LC3 conversion. In addition, transcription factor EB (TFEB), which acts as a transcription factor regulating the transcription of autophagy-related genes, was much more localized in the nucleus in A375P/Mdr cells than in A375P cells, indicating that the increase in basal autophagic flux was TFEB-dependent. In particular, the overexpression of an activated form of TFEB (TFEBAA) caused a modest increase in PLX4720 resistance in A375P/Mdr cells. Interestingly, treatment with early stage autophagy inhibitors reversed BRAF inhibitor-induced resistance, whereas late autophagy inhibition did not. In contrast, inhibition of ER stress by 4-phenylbutyric acid suppressed basal autophagic flux. Moreover, ER stress inhibition significantly remarkably inhibited the nuclear localization of TFEB, resulting in an increase in the sensitivity of A375P/Mdr cells to PLX4720. Taken together, these results suggest that autophagy may be an important mechanism of acquired resistance to BRAF inhibitors. Thus, targeting autophagy may be suitable for the treatment of tumors resistant to BRAF inhibitor.

The XBP1‒MARCH5‒MFN2 Axis Confers Endoplasmic Reticulum Stress Resistance by Coordinating Mitochondrial Fission and Mitophagy in Melanoma

Melanoma cells are relatively resistant to endoplasmic reticulum (ER) stress, which contributes to tumor progression under stressful conditions and renders tolerance to ER stress‒inducing therapeutic agents. Mitochondria are tightly interconnected with ER. However, whether mitochondria play a role in regulating ER stress resistance in melanoma remains elusive. In this study, we reported that the XBP1‒MARCH5‒MFN2 axis conferred ER stress resistance by coordinating mitochondrial fission and mitophagy in melanoma. Our integrative bioinformatics first revealed that the downregulation of mitochondrial genes was highly correlated with unfolded protein response activation in melanoma. Then we proved that mitochondrial fission and mitophagy were prominently induced to contribute to ER stress resistance both in vitro and in vivo by maintaining mitochondrial function. Mechanistically, the activation of IRE1α/ATF6-XBP1 branches of unfolded protein response promoted the transcription of E3 ligase MARCH5 to facilitate the ubiquitination and degradation of MFN2, which thereby triggered mitochondrial fission and mitophagy under ER stress. Together, our findings show a regulatory axis that links mitochondrial fission and mitophagy to the resistance to ER stress. Targeting mitochondrial quality control machinery can be exploited as an approach to reinforce the efficacy of ER stress‒inducing agents against cancer.

Exploration of Benzenesulfonamide-Bearing Imidazole Derivatives Activity in Triple-Negative Breast Cancer and Melanoma 2D and 3D Cell Cultures

Heterocyclic compounds are one of the main groups of organic compounds possessing wide range of applications in various areas of science and their derivatives are present in many bioactive structures. They display a wide variety of biological activities. Recently, more and more attention has been focused to such heterocyclic compounds as azoles. In this work, we have synthesized a series of new imidazole derivatives incorporating a benzenesulfonamide moiety in their structure, which then were evaluated for their cytotoxicity against human triple-negative breast cancer MDA-MB-231 and human malignant melanoma IGR39 cell lines by MTT assay. Benzenesulfonamide-bearing imidazole derivatives containing 4-chloro and 3,4-dichlorosubstituents in benzene ring, and 2-ethylthio and 3-ethyl groups in imidazole ring have been determined as the most active compounds. Half-maximal effective concentration (EC50) of the most cytotoxic compound was 27.8 ± 2.8 µM against IGR39 cell line and 20.5 ± 3.6 µM against MDA-MB-231 cell line. Compounds reduced cell colony formation of both cell lines and inhibited the growth and viability of IGR39 cell spheroids more efficiently compared to triple-negative breast cancer spheroids.

Pharmacological targeting of endoplasmic reticulum stress in disease

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) leads to ER stress, resulting in activation of the unfolded protein response (UPR) that aims to restore protein homeostasis. However, the UPR also plays an important pathological role in many diseases, including metabolic disorders, cancer and neurological disorders. Over the last decade, significant effort has been invested in targeting signalling proteins involved in the UPR and an array of drug-like molecules is now available. However, these molecules have limitations, the understanding of which is crucial for their development into therapies. Here, we critically review the existing ER stress and UPR-directed drug-like molecules, highlighting both their value and their limitations.

Heat Shock Cognate 70 kDa Protein Is the Target of Tetradecyl 2,3-Dihydroxybenzoate for Neuritogenic Effect in PC12 Cells

Tetradecyl 2,3-dihydroxybenzoate (ABG-001) is a lead compound derived from gentisides with a remarkable neuritogenic activity. However, the target of ABG-001 is yet to be defined to date. In this study, the potential target of ABG-001 was investigated via an activity-based protein profiling (ABPP) analysis, which is a chemical proteomic method for target identification by using chemical probes. Results indicated that the potential target proteins of ABG-001 were heat shock cognate 70 kDa protein (Hsc70), 78 kDa glucose-regulated protein (GRP78), and 14-3-3 theta protein. Then, the potential target of ABG-001 was confirmed by using inhibitors, the cellular thermal shift assay (CETSA) and small-interfering RNA (siRNA) analysis. The inhibitor of Hsc70 and siRNA significantly decreased the neurite outgrowth induced by ABG-001. Furthermore, ABG-001 induced neurite outgrowth was reduced by siRNA against Hsc70, and the results of CETSA suggested that Hsc70 showed a significant thermal stability-shifted effect upon ABG-001 treatment. These results indicated that Hsc70 is the target protein of ABG-001 in PC12 cells.

Small molecule-mediated induction of endoplasmic reticulum stress in cancer cells

The endoplasmic reticulum (ER) is one of the crucial sub-cellular organelles controlling myriads of functions including protein biosynthesis, folding, misfolding and unfolding. As a result, dysregulation of these pathways in the ER is implicated in cancer development and progression. Subsequently, targeting the ER in cancer cells emerged as an interesting unorthodox strategy in next-generation anticancer therapy. However, development of small molecules to selectively target the ER for cancer therapy remained elusive and unexplored. To address this, herein, we have developed a novel small molecule library of sulfonylhydrazide-hydrazones through a short and concise chemical synthetic strategy. We identified a fluorescent small molecule that localized into the endoplasmic reticulum (ER) of HeLa cells, induced ER stress followed by triggering autophagy which was subsequently inhibited by chloroquine (autophagy inhibitor) to initiate apoptosis. This small molecule showed remarkable cancer cell killing efficacy in different cancer cells as mono and combination therapy with chloroquine, thus opening a new direction to illuminate ER-biology towards the development of novel anticancer therapeutics.

HA15 alleviates bone loss in ovariectomy-induced osteoporosis by targeting HSPA5

The imbalance between osteogenesis and adipogenesis in the bone marrow is the main characteristic of osteoporosis (OP). Thus, exploring regulation of the differentiation of bone marrow stromal cells (BMSCs) into osteoblasts and adipocytes is important to identify novel targets for the treatment of OP. In the present study, the master regulator of endoplasmic reticulum (ER) stress, heat shock protein family A (Hsp70) member 5 (HSPA5) was shown to significantly accumulate in osteoblasts and adipocytes, but not in osteoclasts in bone sections from aged and postmenopausal OP mice. In vitro study revealed that HSPA5 negatively modulated osteogenic differentiation and positively promoted adipogenic differentiation, and that targeting HSPA5 with its inhibitor HA15 enhanced osteogenic differentiation and inhibited adipogenic differentiation. Also, HA15 treatment induces ER stress and autophagy, and decreases apoptosis in cells. We constructed a postmenopausal OP model in mice with ovariectomy surgery, and treated the mice with HA15. The results showed that HA15 treatment induced appropriate ER stress, activated autophagy and decreased apoptosis in osteoblasts, thereby alleviating bone loss in vivo. Our results indicated that HSPA5 participated in OP pathogenesis by regulating the differentiation of BMSCs. HSPA5 may serve as a new target for the treatment of OP, and targeting HSPA5 with HA15 prevents the progression of OP and provides a candidate therapeutic molecule for postmenopausal OP.

Silencing of CEBPB-AS1 modulates CEBPB expression and resensitizes BRAF-inhibitor resistant melanoma cells to vemurafenib

Supplemental Digital Content is available in the text.

Introduction of targeted therapy in the treatment of metastatic cutaneous malignant melanoma (CMM) has improved clinical outcome during the last years. However, only in a subset of the CMM patients, this will lead to long-term effects. CEBPB is a transcription factor that has been implicated in various physiological and pathological processes, including cancer development. We have investigated its prognostic impact on CMM and unexpectedly found that higher CEBPB mRNA levels correlated with a longer overall survival. Furthermore, in a small cohort of patients with metastatic CMM treated with BRAF-inhibitors, higher levels of CEBPB mRNA expression in the tumor cells prior treatment correlated to a longer progression-free survival. We have characterized an overlapping antisense transcript, CEBPB-AS1, with the aim to investigate the regulation of CEBPB expression in CMM and its impact on BRAF-inhibitor sensitivity. We demonstrated that silencing of CEBPB-AS1 resulted in epigenetic modifications in the CEBPB promoter and in increased CEBPB mRNA and protein levels, inhibited proliferation and partially resensitized BRAF-inhibitor resistant CMM cells to this drug-induced apoptosis. Our data suggest that targeting CEBPB-AS1 may represent a valuable tool to sensitize CMM cells to the BRAF-inhibitor-based therapies.

PERK mediates resistance to BRAF inhibition in melanoma with impaired PTEN

Targeting mutant BRAF in patients with melanomas harboring this oncogene has been highly successful as a first-line treatment, but other mutations may affect its efficacy and alter the route of acquired resistance resulting in recurrence and poor prognosis. As an evolving strategy, melanoma treatment needs to be expanded to include targets based on newly discovered emerging molecules and pathways. We here show that PERK plays a critical role in BRAF inhibitor-acquired resistance in melanoma with impaired PTEN. Inhibition of PERK by either shRNA or a pharmacological inhibitor blocked the growth of BRAF inhibitor-resistant melanoma with impaired PTEN in vitro and in vivo, suggesting an effective approach against melanomas with mutant BRAF and PTEN deficiency. Our current findings, along with our previous discovery that the AXL/AKT axis mediates resistance to BRAF inhibition in melanoma with wild-type PTEN, provide new insights toward a strategy for combating BRAF inhibition-acquired resistance in BRAF mutant melanoma with different PTEN statuses.

Adipocyte-driven unfolded protein response is a shared transcriptomic signature of metastatic prostate carcinoma cells

A critical unknown in the field of skeletal metastases is how cancer cells find a way to thrive under harsh conditions, as exemplified by metastatic colonization of adipocyte-rich bone marrow by prostate carcinoma cells. To begin understanding molecular processes that enable tumor cells to survive and progress in difficult microenvironments such as bone, we performed unbiased examination of the transcriptome of two different prostate cancer cell lines in the absence or presence of bone marrow adipocytes. Our RNAseq analyses and subsequent quantitative PCR and protein-based assays reveal that upregulation of endoplasmic reticulum (ER) stress and unfolded protein response (UPR) genes is a shared signature between metastatic prostate carcinoma cell lines of different origin. Pathway analyses and pharmacological examinations highlight the ER chaperone BIP as an upstream coordinator of this transcriptomic signature. Additional patient-based data support our overall conclusion that ER stress and UPR induction are shared, important factors in the response and adaptation of metastatic tumor cells to their micro-environment. Our studies pave the way for additional mechanistic investigations and offer new clues towards effective therapeutic interventions in metastatic disease.

Integration of Metabolomics and Transcriptomics Reveals Ketone Body and Lipid Metabolism Disturbance Related to ER Stress in the Liver

Once protein synthesis is excessive or misfolded protein becomes aggregated, which eventually overwhelms the capacity of the endoplasmic reticulum (ER), a state named ER stress would be reached. ER stress could affect many tissues, especially the liver, in which nonalcoholic fatty liver disease, liver steatosis, etc. have been reported relative. However, there is still a lack of systematic insight into ER stress in the liver, which can be obtained by integrating metabolomics and transcriptomics of the tissue. Here, tunicamycin was utilized to induce ER stress in C57BL/6N mice. Microarray and untargeted metabolomics were performed to identify the genes and metabolites significantly altered in liver tissues. Surprisingly, apart from the predictable unfolded protein response, liver lipid, arginine, and proline metabolisms were affirmed to be related to ER stress. Also, the ketone body metabolism changed most prominently in response to ER stress, with few studies backing. What is more, succinate receptor 1 (Sucnr1) may be a novel marker and therapeutical target of liver ER stress. In this study, the combination of the metabolome and transcriptome provided reliable information about liver pathological processes, including key relative pathways, potential markers, and targets involved in ER stress of the liver.

Regulating Twisted Skeleton to Construct Organ-Specific Perylene for Intensive Cancer Chemotherapy

The systemic use of pharmaceutical drugs for cancer patients is a compromise between desirable therapy and side effects because of the intrinsic shortage of organ-specific pharmaceutical drug. Design and construction of pharmaceutical drug to achieve the organ-specific delivery is thus desperately desirable. We herein regulate perylene skeleton to effect organ-specificity and present an example of lung-specific distribution on the basis of bay-twisted PDIC-NC. We further demonstrate that PDIC-NC can target into mitochondria to act as cellular respiration inhibitor, inducing insufficient production of adenosine triphosphate, promoting endogenous H2 O2 and . OH burst, elevating calcium overload, efficiently triggering the synergistic apoptosis, autophagy and endoplasmic reticulum stress of lung cancer cells. The antitumor performance of PDIC-NC is verified on in vivo xenografted, metastasis and orthotopic lung cancer, presenting overwhelming evidences for potentially clinical application. This study contributes a proof-of-concept demonstration of twisted perylene to well attain lung-specific distribution, and meanwhile achieves intensive lung cancer chemotherapy.

Identification of a class of non-conventional ER-stress-response-derived immunogenic peptides

Efforts to overcome resistance to immune checkpoint blockade therapy have focused on vaccination strategies using neoepitopes, although they cannot be applied on a large scale due to the "private" nature of cancer mutations. Here, we show that infection of tumor cells with Salmonella induces the opening of membrane hemichannels and the extracellular release of proteasome-generated peptides by the exacerbation of endoplasmic reticulum (ER) stress. Peptides released by cancer cells foster an antitumor response in vivo, both in mice bearing B16F10 melanomas and in dogs suffering from osteosarcoma. Mass spectrometry analysis on the supernatant of human melanoma cells revealed 12 peptides capable of priming healthy-donor CD8+ T cells that recognize and kill human melanoma cells in vitro and when xenotransplanted in vivo. Hence, we identified a class of shared tumor antigens that are generated in ER-stressed cells, such as tumor cells, that do not induce tolerance and are not presented by healthy cells.

HNRNPH1-stabilized LINC00662 promotes ovarian cancer progression by activating the GRP78/p38 pathway

Numerous studies suggest an important role for copy number alterations (CNAs) in cancer progression. However, CNAs of long intergenic noncoding RNAs (lincRNAs) in ovarian cancer (OC) and their potential functions have not been fully investigated. Here, based on analysis of The Cancer Genome Atlas (TCGA) database, we identified in this study an oncogenic lincRNA termed LINC00662 that exhibited a significant correlation between its CNA and its increased expression. LINC00662 overexpression is highly associated with malignant features in OC patients and is a prognostic indicator. LINC00662 significantly promotes OC cell proliferation and metastasis in vitro and in vivo. Mechanistically, LINC00662 is stabilized by heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1). Moreover, LINC00662 exerts oncogenic effects by interacting with glucose-regulated protein 78 (GRP78) and preventing its ubiquitination in OC cells, leading to activation of the oncogenic p38 MAPK signaling pathway. Taken together, our results define an oncogenic role for LINC00662 in OC progression mediated via GRP78/p38 signaling, with potential implications regarding therapeutic targets for OC.

Fluorinated thiazolidinol drives autophagic cell death in pancreatic cancer cells via AMPK activation and perturbation of critical sentinels of oncogenic signaling

Pancreatic cancer is one of the most malignant cancers around the world. The co-occurrence of mutation in KRAS and p53 makes it highly aggressive, proliferative, metastatic, and resistant to apoptotic cell death. Therefore, there is a need to trigger an alternate mechanism of cancer cell death in apoptosis-resistant pancreatic cancer. Autophagic cell death could be an alternate viable option for treatment in such cases. Thus, the identification of small molecules as autophagy modulators with potent anticancer efficacy would be of great importance in pancreatic cancer. The present study investigates fluorinated thiazolidionol (FTZ) driven autophagy modulation, underlying mechanism, and regulation of critical sentinels of oncogenic signaling in pancreatic cancer cells. We identified that FTZ triggered autophagic cell death in pancreatic cancer cells, independent of apoptosis evidenced by an increase in cytoplasmic vacuoles formation, autophagy flux, LC3-II expression, and p62 degradation. Further, the crucial events of apoptosis i.e., Caspase-3 activation and PARP cleavage, were not observed, indicating the non-occurrence of apoptotic cell death. Moreover, FTZ was able to activate AMPK and suppress PI3k/Akt/mTOR as well as MEK/ERK, the key oncogenic signaling pathways in cancer cells. Furthermore, treatment with FTZ suppressed migration, invasion, and angiogenesis in pancreatic cancer cells. Studies in vivo revealed significant regression of tumors by FTZ in nude mice model. Overall, our study demonstrates that FTZ induces autophagic cell death in pancreatic cancer cells independent of apoptosis, which is accompanied by AMPK activation and suppression of critical sentinels of oncogenic signaling in pancreatic cancer cells.

Development and in vivo evaluation of fused benzazole analogs of anti-melanoma agent HA15

Background: In line with our recent discovery of an efficient anticancer thiazolebenzenesulfonamide framework HA15 (1) based on a remarkable endoplasmic reticulum stress inducement mode of action, we report herein a series of innovative constrained HA15 analogs, featuring four types of bicylic derivatives. Results: The structure-activity relationship analysis, using a cell line assay, led us to identify a novel version of HA15: a new benzothiazole derivative (10b) exhibiting important anti-melanoma effect against sensitive and resistant melanoma cells. Meanwhile, compound 10b induced a significant tumor growth inhibition in vivo with no apparent signs of toxicity. Conclusion: These results consistently open new directions to improve and develop more powerful anticancer therapeutics harboring this type of fused framework.

USP22 promotes HER2-driven mammary carcinoma aggressiveness by suppressing the unfolded protein response

The Ubiquitin-Specific Protease 22 (USP22) is a deubiquitinating subunit of the mammalian SAGA transcriptional co-activating complex. USP22 was identified as a member of the so-called "death-from-cancer" signature predicting therapy failure in cancer patients. However, the importance and functional role of USP22 in different types and subtypes of cancer remain largely unknown. In the present study, we leveraged human cell lines and genetic mouse models to investigate the role of USP22 in HER2-driven breast cancer (HER2+-BC) and demonstrate for the first time that USP22 is required for the tumorigenic properties in murine and human HER2+-BC models. To get insight into the underlying mechanisms, we performed transcriptome-wide gene expression analyses and identified the Unfolded Protein Response (UPR) as a pathway deregulated upon USP22 loss. The UPR is normally induced upon extrinsic or intrinsic stresses that can promote cell survival and recovery if shortly activated or programmed cell death if activated for an extended period. Strikingly, we found that USP22 actively suppresses UPR induction in HER2+-BC cells by stabilizing the major endoplasmic reticulum (ER) chaperone HSPA5. Consistently, loss of USP22 renders tumor cells more sensitive to apoptosis and significantly increases the efficiency of therapies targeting the ER folding capacity. Together, our data suggest that therapeutic strategies targeting USP22 activity may sensitize tumor cells to UPR induction and could provide a novel, effective approach to treat HER2+-BC.

Identifying Novel Actionable Targets in Colon Cancer

Colorectal cancer is the fourth cause of death from cancer worldwide, mainly due to the high incidence of drug-resistance toward classic chemotherapeutic and newly targeted drugs. In the last decade or so, the development of novel high-throughput approaches, both genome-wide and chemical, allowed the identification of novel actionable targets and the development of the relative specific inhibitors to be used either to re-sensitize drug-resistant tumors (in combination with chemotherapy) or to be synthetic lethal for tumors with specific oncogenic mutations. Finally, high-throughput screening using FDA-approved libraries of “known” drugs uncovered new therapeutic applications of drugs (used alone or in combination) that have been in the clinic for decades for treating non-cancerous diseases (re-positioning or re-purposing approach). Thus, several novel actionable targets have been identified and some of them are already being tested in clinical trials, indicating that high-throughput approaches, especially those involving drug re-positioning, may lead in a near future to significant improvement of the therapy for colon cancer patients, especially in the context of a personalized approach, i.e., in defined subgroups of patients whose tumors carry certain mutations.

Function, Therapeutic Potential, and Inhibition of Hsp70 Chaperones

Hsp70s are among the most highly conserved proteins in all of biology. Through an iterative binding and release of exposed hydrophobic residues on client proteins, Hsp70s can prevent aggregation and promote folding to the native state of their client proteins. The human proteome contains eight canonical Hsp70s. Because Hsp70s are relatively promiscuous they play a role in folding a large proportion of the proteome. Hsp70s are implicated in disease through their ability to regulate protein homeostasis. In recent years, researchers have attempted to develop selective inhibitors of Hsp70 isoforms to better understand the role of individual isoforms in biology and as potential therapeutics. Selective inhibitors have come from rational design, forced localization, and serendipity, but the development of completely selective inhibitors remains elusive. In the present review, we discuss the Hsp70 structure and function, the known Hsp70 client proteins, the role of Hsp70s in disease, and current efforts to discover Hsp70 modulators.

Endoplasmic reticulum chaperone GRP78/BiP is critical for mutant Kras-driven lung tumorigenesis

Lung cancer is the leading cause of cancer mortality worldwide and KRAS is the most commonly mutated gene in lung adenocarcinoma (LUAD). The 78-kDa glucose-regulated protein GRP78/BiP is a key endoplasmic reticulum chaperone protein and a major pro-survival effector of the unfolded protein response (UPR). Analysis of the Cancer Genome Atlas database and immunostain of patient tissues revealed that compared to normal lung, GRP78 expression is generally elevated in human lung cancers, including tumors bearing the KRAS^G12D mutation. To test the requirement of GRP78 in human lung oncogenesis, we generated mouse models containing floxed Grp78 and Kras Lox-Stop-Lox G12D (Kras^LSL-G12D) alleles. Simultaneous activation of the Kras^G12D allele and knockout of the Grp78 alleles were achieved in the whole lung or selectively in lung alveolar epithelial type 2 cells known to be precursors for adenomas that progress to LUAD. Here we report that GRP78 haploinsufficiency is sufficient to suppress Kras^G12D-mediated lung tumor progression and prolong survival. Furthermore, GRP78 knockdown in human lung cancer cell line A427 (Kras^G12D/+) leads to activation of UPR and apoptotic markers and loss of cell viability. Our studies provide evidence that targeting GRP78 represents a novel therapeutic approach to suppress mutant KRAS-mediated lung tumorigenesis.

The Hydroxyquinoline Analogue YUM70 Inhibits GRP78 to Induce ER Stress-Mediated Apoptosis in Pancreatic Cancer

GRP78 (glucose-regulated protein, 78 kDa) is a key regulator of endoplasmic reticulum (ER) stress signaling. Cancer cells are highly proliferative and have high demand for protein synthesis and folding, which results in significant stress on the ER. To respond to ER stress and maintain cellular homeostasis, cells activate the unfolded protein response (UPR) that promotes either survival or apoptotic death. Cancer cells utilize the UPR to promote survival and growth. In this study, we describe the discovery of a series of novel hydroxyquinoline GRP78 inhibitors. A representative analogue, YUM70, inhibited pancreatic cancer cell growth in vitro and showed in vivo efficacy in a pancreatic cancer xenograft model with no toxicity to normal tissues. YUM70 directly bound GRP78 and inactivated its function, resulting in ER stress-mediated apoptosis. A YUM70 analogue conjugated with BODIPY showed colocalization of the compound with GRP78 in the ER. Moreover, a YUM70-PROTAC (proteolysis targeting chimera) was synthesized to force degradation of GRP78 in pancreatic cancer cells. YUM70 showed a strong synergistic cytotoxicity with topotecan and vorinostat. Together, our study demonstrates that YUM70 is a novel inducer of ER stress, with preclinical efficacy as a monotherapy or in combination with topoisomerase and HDAC inhibitors in pancreatic cancer. SIGNIFICANCE: This study identifies a novel ER stress inducer that binds GRP78 and inhibits pancreatic cancer cell growth in vitro and in vivo, demonstrating its potential as a therapeutic agent for pancreatic cancer.

Proteomic Discovery of VEEV E2-Host Partner Interactions Identifies GRP78 Inhibitor HA15 as a Potential Therapeutic for Alphavirus Infections

Alphaviruses are a genus of the Togaviridae family and are widely distributed across the globe. Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV), cause encephalitis and neurological sequelae while chikungunya virus (CHIKV) and Sindbis virus (SINV) cause arthralgia. There are currently no approved therapeutics or vaccines available for alphaviruses. In order to identify novel therapeutics, a V5 epitope tag was inserted into the N-terminus of the VEEV E2 glycoprotein and used to identify host-viral protein interactions. Host proteins involved in protein folding, metabolism/ATP production, translation, cytoskeleton, complement, vesicle transport and ubiquitination were identified as VEEV E2 interactors. Multiple inhibitors targeting these host proteins were tested to determine their effect on VEEV replication. The compound HA15, a GRP78 inhibitor, was found to be an effective inhibitor of VEEV, EEEV, CHIKV, and SINV. VEEV E2 interaction with GRP78 was confirmed through coimmunoprecipitation and colocalization experiments. Mechanism of action studies found that HA15 does not affect viral RNA replication but instead affects late stages of the viral life cycle, which is consistent with GRP78 promoting viral assembly or viral protein trafficking.

Chemogenomic and bioinformatic profiling of ERdj paralogs underpins their unique roles in cancer

The ER-resident Hsp70 paralog BiP is important in cellular homeostasis as well as in cancer cell progression. Although several BiP inhibitors have been developed, they have not succeeded in clinical trials due to toxicity issues. ER-resident co-chaperones (ERdjs) tailor the activity and specificity of BiP. Here, we report multiple-cancer analyses of BiP and ERdj genomic alterations including mRNA expression from cancer patients using available data from The Cancer Genome Atlas (TCGA). We examine the individual roles of BiP co-chaperones ERdj1-8 in mediating anticancer drug resistance through chemogenomic screening of ERdj1-8 CRISPR KO cells. In keeping with the idea that ERdjs regulate distinct facets of proteostasis, we find that each ERdj KO displays a unique signature of drug resistance. Taken together, our results demonstrate a novel way to understand functional specificity of ERdjs, suggesting a future personalized medicine approach, whereby ERdj mutation status is assessed to design an effective anticancer treatment plan.

Endoplasmic reticulum stress signals in the tumour and its microenvironment

Protein handling, modification and folding in the endoplasmic reticulum (ER) are tightly regulated processes that determine cell function, fate and survival. In several tumour types, diverse oncogenic, transcriptional and metabolic abnormalities cooperate to generate hostile microenvironments that disrupt ER homeostasis in malignant and stromal cells, as well as infiltrating leukocytes. These changes provoke a state of persistent ER stress that has been demonstrated to govern multiple pro-tumoural attributes in the cancer cell while dynamically reprogramming the function of innate and adaptive immune cells. Aberrant activation of ER stress sensors and their downstream signalling pathways have therefore emerged as key regulators of tumour growth and metastasis as well as response to chemotherapy, targeted therapies and immunotherapy. In this Review, we discuss the physiological inducers of ER stress in the tumour milieu, the interplay between oncogenic signalling and ER stress response pathways in the cancer cell and the profound immunomodulatory effects of sustained ER stress responses in tumours.

IRE1 Alpha/XBP1 Axis Sustains Primary Effusion Lymphoma Cell Survival by Promoting Cytokine Release and STAT3 Activation

Primary Effusion Lymphoma (PEL) is a highly aggressive B cell lymphoma associated with Kaposi's Sarcoma-associated Herpesvirus (KSHV). It is characterized by a high level of basal Endoplasmic Reticulum (ER) stress, Unfolded Protein Response (UPR) activation and constitutive phosphorylation of oncogenic pathways such as the Signal Transducer and activator of Transcription (STAT3). In this study, we found that the inositol requiring kinase (IRE) 1alpha/X-box binding protein (XBP1) axis of UPR plays a key role in the survival of PEL cells, while double stranded RNA-activated protein kinase-like ER kinase (PERK) and activating transcription factor (ATF) 6 slightly influence it, in correlation with the capacity of the IRE1alpha/XBP1 axis to induce the release of interleukin (IL)-6, IL-10 and Vascular-Endothelial Growth Factor (VEGF). Moreover, we found that IRE1alpha/XBP1 inhibition reduced STAT3 Tyr705 phosphorylation and induced a pro-survival autophagy in PEL cells. In conclusion, this study suggests that targeting the IRE1alpha/XBP1 axis represents a promising strategy against PEL cells and that the cytotoxic effect of this treatment may be potentiated by autophagy inhibition.

Cell Proliferation Is Strongly Associated with the Treatment Conditions of an ER Stress Inducer New Anti-Melanoma Drug in Melanoma Cell Lines

HA15 is a new anti-melanoma drug that triggers endoplasmic reticulum (ER) stress and causes deleterious effects on melanoma cell viability due to autophagy and apoptosis, regardless of driver mutations or drug resistance. In this study, we investigated the effect of HA15 on the viability/proliferation of BRAFV600E-mutant melanoma cells using different culture conditions. In contrast to the published data, we did not detect significant melanoma cell death under normal culture conditions using HA15 treatment. Indeed, only cells that were cultured under long-term starvation conditions were sensitive to the drug. Quantitative measurements of ER stress and autophagy markers showed that the compound HA15 does not trigger stress alone but synergistically enhances ER stress under starvation conditions. Importantly, we observed that the viability of normal melanocytes decreased significantly with treatment, even at low HA15 concentrations. Finally yet importantly, we were able to generate HA15-resistant cell lines, which failed by Cerezo et al. In summary, HA15 only influences the viability of cells that are starved for several hours before and during treatment. However, this in vitro setting is far from the in vivo conditions. In addition, our data clearly show that melanoma cells can acquire HA15 resistance. Further studies are needed to prove that HA15 is an effective anti-cancer agent.

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.

Discovery of a new molecule inducing melanoma cell death: dual AMPK/MELK targeting for novel melanoma therapies

In the search of biguanide-derived molecules against melanoma, we have discovered and developed a series of bioactive products and identified the promising new compound CRO15. This molecule exerted anti-melanoma effects on cells lines and cells isolated from patients including the ones derived from tumors resistant to BRAF inhibitors. Moreover, CRO15 was able to decrease viability of cells lines from a broad range of cancer types. This compound acts by two distinct mechanisms. First by activating the AMPK pathway induced by a mitochondrial disorder. Second by inhibition of MELK kinase activity, which induces cell cycle arrest and activation of DNA damage repair pathways by p53 and REDD1 activation. All of these mechanisms activate autophagic and apoptotic processes resulting in melanoma cell death. The strong efficacy of CRO15 to reduce the growth of melanoma xenograft sensitive or resistant to BRAF inhibitors opens interesting perspective.

Mechanisms of Resistance to BRAF-Targeted Melanoma Therapies

About half of all cutaneous melanomas harbor activating mutations in the BRAF oncogene. Dependence on this pathway makes the tumors vulnerable to BRAF (and downstream MEK) inhibition, and three drug combinations are approved to target this vulnerability in advanced melanomas with BRAFV600 mutations. Responses to BRAF/MEK inhibitors are usually fast, but durability of response can be limited. Five-year data from BRAF/MEK inhibitors show long-term survival benefit for a third of the patients. There is a wide variety of known mechanisms of resistance to BRAF/MEK inhibition, such as mitogen-activated protein kinase reactivation, activation of parallel pathways, alterations in cell-cycle regulation, and non-genetic resistance mechanisms. Strategies that have been explored to overcome these mechanisms include alternative dosing regimens, addition of another kinase inhibitor, and use of anti-PD-1 immunotherapy either in combination or post-relapse on BRAF/MEK inhibitor therapies.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.