Endoplasmic Reticulum Stress Protein GRP78 Modulates Lipid Metabolism to Control Drug Sensitivity and Antitumor Immunity in Breast Cancer

SPDYC serves as a prognostic biomarker related to lipid metabolism and the immune microenvironment in breast cancer

Breast cancer remains the most common malignant carcinoma among women globally and is resistant to several therapeutic agents. There is a need for novel targets to improve the prognosis of patients with breast cancer. Bioinformatics analyses were conducted to explore potentially relevant prognostic genes in breast cancer using The Cancer Genome Atlas (TCGA) and The Gene Expression Omnibus (GEO) databases. Gene subtypes were categorized by machine learning algorithms. The machine learning-related breast cancer (MLBC) score was evaluated through principal component analysis (PCA) of clinical patients' pathological statuses and subtypes. Immune cell infiltration was analyzed using the xCell and CIBERSORT algorithms. Kyoto Encyclopedia of Genes and Genomes enrichment analysis elucidated regulatory pathways related to speedy/RINGO cell cycle regulator family member C (SPDYC) in breast cancer. The biological functions and lipid metabolic status of breast cancer cell lines were validated via quantitative real-time polymerase chain reaction (RT‒qPCR) assays, western blotting, CCK-8 assays, PI‒Annexin V fluorescence staining, transwell assays, wound healing assays, and Oil Red O staining. Key differentially expressed genes (DEGs) in breast cancer from the TCGA and GEO databases were screened and utilized to establish the MLBC score. Moreover, the MLBC score we established was negatively correlated with poor prognosis in breast cancer patients. Furthermore, the impacts of SPDYC on the tumor immune microenvironment and lipid metabolism in breast cancer were revealed and validated. SPDYC is closely related to activated dendritic cells and macrophages and is simultaneously correlated with the immune checkpoints CD47, cytotoxic T lymphocyte antigen-4 (CTLA-4), and poliovirus receptor (PVR). SPDYC strongly correlated with C-C motif chemokine ligand 7 (CCL7), a chemokine that influences breast cancer patient prognosis. A significant relationship was discovered between key genes involved in lipid metabolism and SPDYC, such as ELOVL fatty acid elongase 2 (ELOVL2), malic enzyme 1 (ME1), and squalene epoxidase (SQLE). Potent inhibitors targeting SPDYC in breast cancer were also discovered, including JNK inhibitor VIII, AICAR, and JW-7-52-1. Downregulation of SPDYC expression in vitro decreased proliferation, increased the apoptotic rate, decreased migration, and reduced lipid droplets. SPDYC possibly influences the tumor immune microenvironment and regulates lipid metabolism in breast cancer. Hence, this study identified SPDYC as a pivotal biomarker for developing therapeutic strategies for breast cancer.

A bibliometric analysis of endoplasmic reticulum stress and atherosclerosis

The mechanisms underlying the occurrence and development of atherosclerosis (AS) are diverse, among which endoplasmic reticulum stress (ERS) is an important mechanism that should not be overlooked. However, up to now, there has been no bibliometric study on the relationship between ERS and AS. To understand the research progress in ERS and AS, this paper conducted a statistical analysis of publications in this field using bibliometrics. A total of 1,035 records were retrieved from the Web of Science Core Collection. CiteSpace, VOSviewer, and the R package "bibliometric" were used to analyze the spatiotemporal distribution, countries, authors, institutions, journals, references, and keywords of the literature, and to present the basic information of this field through visualized maps, as well as determine the collaboration relationships among researchers in this field. This field has gradually developed and stabilized over the past 20 years. The current research hotspots in this field mainly include the relationship between ERS and AS-related cells, the mechanisms by which ERS promotes AS, related diseases, and associated cytokines, etc. Vascular calcification, endothelial dysfunction, NLRP3 inflammasome, and heart failure represent the frontier research in this field and are becoming new research hotspots. It is hoped that this study will provide new insights for research and clinical work in the field of ERS and AS.

Metabolic reprogramming and interventions in angiogenesis

BACKGROUND

Endothelial cell (EC) metabolism plays a crucial role in the process of angiogenesis. Intrinsic metabolic events such as glycolysis, fatty acid oxidation, and glutamine metabolism, support secure vascular migration and proliferation, energy and biomass production, as well as redox homeostasis maintenance during vessel formation. Nevertheless, perturbation of EC metabolism instigates vascular dysregulation-associated diseases, especially cancer.

AIM OF REVIEW

In this review, we aim to discuss the metabolic regulation of angiogenesis by EC metabolites and metabolic enzymes, as well as prospect the possible therapeutic opportunities and strategies targeting EC metabolism.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we discuss various aspects of EC metabolism considering normal and diseased vasculature. Of relevance, we highlight that the implications of EC metabolism-targeted intervention (chiefly by metabolic enzymes or metabolites) could be harnessed in orchestrating a spectrum of pathological angiogenesis-associated diseases.

SPRTN is involved in hepatocellular carcinoma development through the ER stress response

Endoplasmic reticulum (ER) stress, prompted by the accumulation of misfolded or unfolded proteins, triggers the activation of the unfolded protein response (UPR) pathway to restore ER homeostasis. This stress response is implicated in the development of hepatocellular carcinoma (HCC). A biallelic mutation in SPRTN is currently the only known single-gene mutation implicated in the early onset of HCC. However, the exact mechanism linking SPRTN mutations to HCC remains unclear. In our study, we analyzed SPRTN and UPR in 21 human HCC tissue samples using RT-qPCR, immunoblot, and immunohistochemistry. We found alterations in the expression levels of SPRTN and UPR-related genes and proteins in HCC samples. The impact of SPRTN on the ER stress response was assessed in SPRTN-depleted HepG2 cells through RNA sequencing, pull-down assay, comet assay, and mitotic index calculation. We demonstrated that SPRTN interacts with the UPR sensor GRP78. Furthermore, we observed a decrease in SPRTN levels during ER stress, and increased sensitivity to ER stress in SPRTN-depleted cells. These findings suggest an essential role for SPRTN in the ER stress response and provide new insights into HCC pathogenesis. This newly discovered function of SPRTN could significantly enhance our understanding and treatment of HCC.

Thrombospondin-1 in drug activity and tumor response to therapies

Thrombospondins (TSPs) have numerous different roles in cancer, regulating the behavior of cancer cells and non-neoplastic cells, and defining the responses of tumor cells to environmental changes, thorough their ability to orchestrate cellular and molecular interactions in the tumor microenvironment (TME). As a result of these activities, TSPs can also control drug delivery and activity, tumor response and resistance to therapies, with different outcomes depending on the nature of TSP-interacting cell types, receptors, and ligands, in a highly context-dependent manner. This review, focusing primarily on TSP-1, discusses the effects of TSPs on tumor response to chemotherapy, antiangiogenic, low-dose metronomic chemotherapy, immunotherapy, and radiotherapy, by analyzing TSP activity on different cell compartments - tumor cells, vascular endothelial cells and immune cells. We review evidence of the value of TSPs, specifically TSP-1 and TSP-2, as biomarkers of prognosis and tumor response to therapy. Finally, we examine possible approaches to develop TSP-based compounds as therapeutic tools to potentiate the efficacy of anticancer therapy.

Transcriptomics and molecular docking reveal the potential mechanism of lycorine against pancreatic cancer

BACKGROUND

Pancreatic cancer is an extremely malignant digestive tumor, however, owing to its high drug resistance of pancreatic cancer, the search for more effective anti-pancreatic cancer drugs is urgently needed. Lycorine, an alkaloid of natural plant origin, exerts antitumor effects on a variety of tumors.

PURPOSE

This study aimed to investigate the therapeutic effect of lycorine on pancreatic cancer and elucidate its potential molecular mechanism.

METHODS

Two pancreatic cancer cell lines, PANC-1 and BxPC-3, were used to investigate the therapeutic effects of lycorine on pancreatic cancer in vitro using the CCK8 assay, colony formation assay, 5-Ethynyl-2'- deoxyuridine (EdU) incorporation assay, flow cytometry, and western blotting. Transcriptome sequencing and gene set enrichment analysis (GSEA) were used to analyze the differentially expressed genes and pathways after lycorine treatment. Molecular docking, quantitative real-time PCR (qRT-PCR), oil red O staining, small interfering RNA (siRNA) transfection, and other experiments were performed to further validate the differentially expressed genes and pathways. In vivo experiments were conducted to investigate lycorine's inhibitory effects and toxicity on pancreatic cancer using a tumor-bearing mouse model.

RESULTS

Lycorine inhibited the proliferation of pancreatic cancer cells, caused G2/M phase cycle arrest and induced apoptosis. Transcriptome sequencing and GSEA showed that lycorine inhibition of pancreatic cancer was associated with fatty acid metabolism, and aldehyde dehydrogenase 3A1 (ALDH3A1) was a significantly enriched target in the fatty acid metabolism process. ALDH3A1 expression was significantly upregulated in pancreatic cancer and was closely associated with prognosis. Molecular docking showed that lycorine binds strongly to ALDH3A1. Further studies revealed that lycorine inhibited the fatty acid oxidation (FAO) process in pancreatic cancer cells and induced cell growth inhibition and apoptosis through ALDH3A1. Lycorine also showed significant suppressive effects in tumor-bearing mice. Importantly, it did not result in significant toxicity to liver and kidney of mice, demonstrating its therapeutic potential as a safe antitumor agent.

CONCLUSION

Lycorine inhibited pancreatic cancer cell proliferation, blocked the cell cycle, and induced apoptosis by targeting ALDH3A1. FAO inhibition was identified for the first time as a possible mechanism for the anticancer effects of lycorine. These findings enrich the theory of targeted therapy for pancreatic cancer, expand our understanding of the pharmacological targets of lycorine, and provide a reference for exploring its natural components.

NR3C2 activates LCN2 transcription to promote endoplasmic reticulum stress and cell apoptosis in ischemic cerebral infarction

Endoplasmic reticulum (ER) stress can lead to cell death and worsen tissue damage during ischemic events. Nuclear receptor subfamily 3 group C member 2 (NR3C2) and lipocalin 2 (LCN2) are known to be associated with ER stress. In this study, we obtained a potential interaction between NR3C2 and LCN2 through bioinformatics. The primary objective was to investigate their roles and interactions in the context of ER stress in ischemic cerebral infarction (ICI). A mouse model of ICI was generated by middle cerebral artery occlusion, resulting in elevated levels of NR3C2 and LCN2 in brain tissues. NR3C2 bound to the LCN2 promoter, thereby activating its transcription. Either knockdown of LCN2 or NR3C2 led to an improvement in neurologic deficits in mice, along with a reduction in infract size, tissue damage, ER stress, inflammation, and cell apoptosis in their brain tissues. Similar results were reproduced in HT22 cells, where LCN2 or NR3C2 knockdown alleviated oxygen-glucose deprivation-induced ER stress, inflammation, and cell apoptosis while improving cell viability. However, the protective effects of NR3C2 knockdown were counteracted when LCN2 was overexpressed, both in vitro and in vivo. Overall, this study demonstrates that NR3C2 activates LCN2 transcription, ultimately promoting ER stress and cell apoptosis in the context of ICI.

ER chaperone GRP78/BiP translocates to the nucleus under stress and acts as a transcriptional regulator

Cancer cells are commonly subjected to endoplasmic reticulum (ER) stress. To gain survival advantage, cancer cells exploit the adaptive aspects of the unfolded protein response such as upregulation of the ER luminal chaperone GRP78. The finding that when overexpressed, GRP78 can escape to other cellular compartments to gain new functions regulating homeostasis and tumorigenesis represents a paradigm shift. Here, toward deciphering the mechanisms whereby GRP78 knockdown suppresses EGFR transcription, we find that nuclear GRP78 is prominent in cancer and stressed cells and uncover a nuclear localization signal critical for its translocation and nuclear activity. Furthermore, nuclear GRP78 can regulate expression of genes and pathways, notably those important for cell migration and invasion, by interacting with and inhibiting the activity of the transcriptional repressor ID2. Our study reveals a mechanism for cancer cells to respond to ER stress via transcriptional regulation mediated by nuclear GRP78 to adopt an invasive phenotype.

Combining PD-L1 blockade with immunogenic cell death induced by AIE photosensitizer to improve antitumor immunity

Immunogenic cell death (ICD) is considered an effective death mode to trigger immune response. However, the currently available efficient ICD inducers are quite limited. Endoplasmic reticulum (ER) stress is known as the precursor of ICD, which can be directly triggered by reactive oxygen species in situ. Herein, a novel photosensitizer (α-Th-TPA-PIO) based on phosphindole oxide, featuring aggregation-induced emission (AIE) is designed and prepared, which possesses good ability of hydroxyl radicals (HO^•) generation. Besides, α-Th-TPA-PIO can selectively accumulate in ER and trigger ER stress under white light irradiation, further leading to effective ICD. Combining with anti-programmed death-ligand 1 (anti-PD-L1), the synergistic effect of photodynamic therapy (PDT) and immune checkpoint blockade can achieve a significantly enhanced inhibition effect on the growth of tumors and simultaneously provoke a systemic antitumor immune response. Notably, by adopting this therapeutic strategy to bilateral and metastatic tumor models, the growth of both primary and distant subcutaneous tumors can be successfully suppressed, and metastatic tumor can also be inhibited to some degree. Taken together, this work not only provides a novel ICD photoinducer based on PDT, but also brings about a useful immunomodulatory strategy to realize superior antitumor effect.

Caffeine alleviates acute liver injury by inducing the expression of NEDD4L and deceasing GRP78 level via ubiquitination

BACKGROUND

Acute liver injury is liver cell injury that occurs rapidly in a short period of time. Caffeine has been shown to maintain hepatoprotective effect with an unclear mechanism. Endoplasmic reticulum stress (ERS) has significant effects in acute liver injury. Induction of GRP78 is a hallmark of ERS. Whether or not caffeine's function is related to GRP78 remains to be explored.

METHODS

Acute liver injury model was established by LPS-treated L02 cells and in vivo administration of LPS/D-Gal in mice. Caffeine was pre-treated in L02 cells or mice. Gene levels was determined by real-time PCR and western blot. Cell viability was tested by CCK-8 assay and cell apoptosis was tested by flow cytometry. The interaction of GRP78 and NEDD4L was determined by Pull-down and co-immunoprecipitation (Co-IP) assay. The ubiquitination by NEDD4L on GRP78 was validated by in vitro ubiquitination assay.

RESULTS

Caffeine protected liver cells against acute injury induced cell apoptosis and ERS both in vitro and in vivo. Suppression of GRP78 could block the LPS-induced cell apoptosis and ERS. NEDD4L was found to interact with GRP78 and ubiquitinate its lysine of 324 site directly. Caffeine treatment induced the expression of NEDD4L, resulting in the ubiquitination and inhibition of GRP78.

CONCLUSION

Caffeine mitigated the acute liver injury by stimulating NEDD4L expression, which inhibited GRP78 expression via ubiquitination at its K324 site. Low dose of caffeine could be a promising therapeutic treatment for acute liver injury.

Impaired Heat Shock Protein Expression in Activated T Cells in B-Cell Lymphoma

Heat shock proteins (HSPs) are molecular chaperones that act in a variety of cellular processes, ensuring protein homeostasis and integrity. HSPs play critical roles in the modulation of various immune cells. However, the role of HSPs in T cell activation is largely unknown. We show that HSPs are upregulated following CD3/CD28 stimulation, suggesting that HSP expression might be regulated via TCR. We found that B-cell lymphoma (BCL) patients have dysregulated expression of intracellular and extracellular HSPs, immune checkpoints PD-1, CTLA-4, and STAT3 in CD3/CD28-activated T cells. Consistent with previous findings, we show that HSP90 inhibition downregulated CD4 and CD8 surface markers in healthy controls and BCL patients. HSP90 inhibition alone or in combination with PD-1 or CTLA-4 inhibitors differentially affected CD4+ and CD8+ T cell degranulation responses when stimulated with allogeneic DCs or CD3/CD28 in BCL patients. Additionally, we showed that HSP90 inhibition does not significantly affect intracellular PD-1 and CTLA-4 expression in CD3/CD28-activated T cells. These findings may provide the basis for the discovery of novel immunological targets for the treatment of cancer patients and improve our understanding of HSP functions in immune cells.

Potential to Eradicate Cancer Stemness by Targeting Cell Surface GRP78

Cancer stemness is proposed to be the main cause of metastasis and tumor relapse after conventional therapy due to the main properties of cancer stem cells. These include unlimited self-renewal, the low percentage in a cell population, asymmetric/symmetric cell division, and the hypothetical different nature for absorbing external substances. As the mechanism of how cancer stemness is maintained remains unknown, further investigation into the basic features of cancer stemness is required. Many articles demonstrated that glucose-regulated protein 78 (GRP78) plays a key role in cancer stemness, suggesting that this molecule is feasible for targeting cancer stem cells. This review summarizes the history of finding cancer stem cells, as well as the functions of GRP78 in cancer stemness, for discussing the possibility of targeting GRP78 to eradicate cancer stemness.

Lipid Dyshomeostasis and Inherited Cerebellar Ataxia

Cerebellar ataxia is a form of ataxia that originates from dysfunction of the cerebellum, but may involve additional neurological tissues. Its clinical symptoms are mainly characterized by the absence of voluntary muscle coordination and loss of control of movement with varying manifestations due to differences in severity, in the site of cerebellar damage and in the involvement of extracerebellar tissues. Cerebellar ataxia may be sporadic, acquired, and hereditary. Hereditary ataxia accounts for the majority of cases. Hereditary ataxia has been tentatively divided into several subtypes by scientists in the field, and nearly all of them remain incurable. This is mainly because the detailed mechanisms of these cerebellar disorders are incompletely understood. To precisely diagnose and treat these diseases, studies on their molecular mechanisms have been conducted extensively in the past. Accumulating evidence has demonstrated that some common pathogenic mechanisms exist within each subtype of inherited ataxia. However, no reports have indicated whether there is a common mechanism among the different subtypes of inherited cerebellar ataxia. In this review, we summarize the available references and databases on neurological disorders characterized by cerebellar ataxia and show that a subset of genes involved in lipid homeostasis form a new group that may cause ataxic disorders through a common mechanism. This common signaling pathway can provide a valuable reference for future diagnosis and treatment of ataxic disorders.

Selective pressure of endocrine therapy activates the integrated stress response through NFκB signaling in a subpopulation of ER positive breast cancer cells

Background

While estrogen receptor (ER) positive breast tumors generally respond well to endocrine therapy (ET), up to 40% of patients will experience relapse, either while on endocrine therapy or after ET is completed. We previously demonstrated that the selective pressure of tamoxifen activates the NFκB pathway in ER + patient tumors, breast cancer cell lines, and breast cancer xenograft tumors, and that this activation allows for survival of a subpopulation of NFκB + cells that contribute to cell regrowth and tumor relapse after ET withdrawal. However, the mechanisms contributing to the expansion of an NFκB + cell population on ET are unknown.

Methods

Here, we utilized single-cell RNA sequencing and bioinformatics approaches to characterize the NFκB + cell population and its clinical relevance. Follow-up studies were conducted to validate our findings and assess the function of the integrated stress response pathway in breast cancer cell lines and patient-derived models.

Results

We found that the NFκB + population that arises in response to ET is a preexisting population is enriched under the selective pressure of ET. Based on the preexisting NFκB + cell population, we developed a gene signature and found that it is predictive of tumor relapse when expressed in primary ER + tumors and is retained in metastatic cell populations. Moreover, we identified that the integrated stress response (ISR), as indicated by increased phosphorylation of eIF2α, occurs in response to ET and contributes to clonogenic growth under the selective pressure of ET.

Conclusions

Taken together, our findings suggest that a cell population with active NFκB and ISR signaling can survive and expand under the selective pressure of ET and that targeting this population may be a viable therapeutic strategy to improve patient outcome by eliminating cells that survive ET. Understanding the mechanisms by which breast cancer cells survive the selective pressure of ET may improve relapse rates and overall outcome for patients with ER + breast tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01515-1.

Estrogen Receptor and the Unfolded Protein Response: Double-Edged Swords in Therapy for Estrogen Receptor-Positive Breast Cancer

Estrogen receptor α (ERα) is a target for the treatment of ER-positive breast cancer patients. Paradoxically, it is also the initial site for estrogen (E₂) to induce apoptosis in endocrine-resistant breast cancer. How ERα exhibits distinct functions, in different contexts, is the focus of numerous investigations. Compelling evidence demonstrated that unfolded protein response (UPR) is closely correlated with ER-positive breast cancer. Treatment with antiestrogens initially induces mild UPR through ERα with activation of three sensors of UPR-PRK-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6)-in the endoplasmic reticulum. Subsequently, these sensors interact with stress-associated transcription factors such as c-MYC, nuclear factor-κB (NF-κB), and hypoxia-inducible factor 1α (HIF1α), leading to acquired endocrine resistance. Paradoxically, E₂ further activates sustained secondary UPR via ERα to induce apoptosis in endocrine-resistant breast cancer. Specifically, PERK plays a key role in inducing apoptosis, whereas IRE1α and ATF6 are involved in endoplasmic reticulum stress-associated degradation after E₂ treatment. Furthermore, persistent activation of PERK deteriorates stress responses in mitochondria and triggers of NF-κB/tumor necrosis factor α (TNFα) axis, ultimately determining cell fate to apoptosis. The discovery of E₂-induced apoptosis has clinical relevance for treatment of endocrine-resistant breast cancer. All of these findings demonstrate that ERα and associated UPR are double-edged swords in therapy for ER-positive breast cancer, depending on the duration and intensity of UPR stress. Herein, we address the mechanistic progress on how UPR leads to endocrine resistance and commits E₂ to inducing apoptosis in endocrine-resistant breast cancer.

HSP70 and HSP90 in Cancer: Cytosolic, Endoplasmic Reticulum and Mitochondrial Chaperones of Tumorigenesis

HSP70 and HSP90 are two powerful chaperone machineries involved in survival and proliferation of tumor cells. Residing in various cellular compartments, HSP70 and HSP90 perform specific functions. Concurrently, HSP70 and HSP90 homologs may also translocate from their primary site under various stress conditions. Herein, we address the current literature on the role of HSP70 and HSP90 chaperone networks in cancer. The goal is to provide a comprehensive review on the functions of cytosolic, mitochondrial and endoplasmic reticulum HSP70 and HSP90 homologs in cancer. Given that high expression of HSP70 and HSP90 enhances tumor development and associates with tumor aggressiveness, further understanding of HSP70 and HSP90 chaperone networks may provide clues for the discoveries of novel anti-cancer therapies.

Linking cell-surface GRP78 to cancer: From basic research to clinical value of GRP78 antibodies

Glucose-related protein 78 (GRP78) is a chaperone protein localized primarily in the endoplasmic reticulum (ER) lumen, where it helps in proper protein folding by targeting misfolded proteins and facilitating protein assembly. In stressed cells, GRP78 is translocated to the cell surface (csGRP78) where it binds to various ligands and triggers different intracellular pathways. Thus, csGRP78 expression is associated with cancer, involved in the maintenance and progression of the disease. Extracellular exposition of csGRP78 leads to the production of autoantibodies as observed in patients with prostate or ovarian cancer, in which the ability to target csGRP78 affects the tumor development. Present on the surface of cancer cells and not normal cells in vivo, csGRP78 represents an interesting target for therapeutic antibody strategies. Here we give an overview of the csGRP78 function in the cell and its role in oncogenesis, thereby providing insight into the clinical value of GRP78 monoclonal antibodies for cancer prognosis and treatment.

The HSP Immune Network in Cancer

Heat shock proteins are molecular chaperones which support tumor development by regulating various cellular processes including unfolded protein response, mitochondrial bioenergetics, apoptosis, autophagy, necroptosis, lipid metabolism, angiogenesis, cancer cell stemness, epithelial-mesenchymal transition and tumor immunity. Apart from their intracellular activities, HSPs have also distinct extracellular functions. However, the role that HSP chaperones play in the regulation of immune responses inside and outside the cell is not yet clear. Herein, we explore the intracellular and extracellular immunologic functions of HSPs in cancer. A broader understanding of how HSPs modulate immune responses may provide critical insights for the development of effective immunotherapies.

HSP70s in Breast Cancer: Promoters of Tumorigenesis and Potential Targets/Tools for Therapy

The high frequency of breast cancer worldwide and the high mortality among women with this malignancy are a serious challenge for modern medicine. A deeper understanding of the mechanisms of carcinogenesis and emergence of metastatic, therapy-resistant breast cancers would help development of novel approaches to better treatment of this disease. The review is dedicated to the role of members of the heat shock protein 70 subfamily (HSP70s or HSPA), mainly inducible HSP70, glucose-regulated protein 78 (GRP78 or HSPA5) and GRP75 (HSPA9 or mortalin), in the development and pathogenesis of breast cancer. Various HSP70-mediated cellular mechanisms and pathways which contribute to the oncogenic transformation of mammary gland epithelium are reviewed, as well as their role in the development of human breast carcinomas with invasive, metastatic traits along with the resistance to host immunity and conventional therapeutics. Additionally, intracellular and cell surface HSP70s are considered as potential targets for therapy or sensitization of breast cancer. We also discuss a clinical implication of Hsp70s and approaches to targeting breast cancer with gene vectors or nanoparticles downregulating HSP70s, natural or synthetic (small molecule) inhibitors of HSP70s, HSP70-binding antibodies, HSP70-derived peptides, and HSP70-based vaccines.

Similarities and Differences of Hsp70, hsc70, Grp78 and Mortalin as Cancer Biomarkers and Drug Targets

Background: Upregulation of Heath Shock Protein 70 (HSP70) chaperones supports cancer cell survival. Their high homology causes a challenge to differentiate them in experimental or prevention and treatment strategies. The objective of this investigation was to determine similarities and differences of Hsp70, hsc70, Grp78 and Mortalin members of the HSP70 family encoded by HSPA1, HSPA8, HSPA5 and HSPA9 genes, respectively. Methods: Literature reviews were conducted using HSPA1, HSPA5, HSPA8 and HSPA9 gene or protein names or synonyms combined with biological or cancer-relevant terms. Ingenuity Pathway Analysis was used to identify and compare profiles of proteins that directly bind individual chaperones and their associated pathways. TCGA data was probed to identify associations of hsc70 with cancer patient survival. ClinicalTrials.gov was used to identify HSP70 family studies. Results: The chaperones have similar protein folding functions. Their different cellular effects are determined by co-chaperones and client proteins combined with their intra- and extra-cellular localizations. Their upregulation is associated with worse patient prognosis in multiple cancers and can stimulate tumor immune responses or drug resistance. Their inhibition selectively kills cancer over healthy cells. Conclusions: Differences in Hsp70, hsc70, Grp78 and mortalin provide opportunities to calibrate HSP70 inhibitors for individual cancers and combination therapies.

Pristimerin induces apoptosis and tumor inhibition of oral squamous cell carcinoma through activating ROS-dependent ER stress/Noxa pathway

BACKGROUND

Pristimerin (Pri), a natural quinone methide triterpenoid isolated from Celastraceae and Hippocrateaceae, exhibits potent antitumor activity against various cancers. However, the mechanism of apoptosis induction by Pri in oral squamous cell carcinoma (OSCC) and its anti-OSCC effect in vivo has not been widely studied.

PURPOSE

This study aimed to investigate the anti-OSCC activities of Pri in vitro and in vivo and addressed the potential mechanisms of Pri-induced apoptosis.

METHODS

The effects of Pri on OSCC cells were analyzed by cell viability, colony formation and flow cytometry assays. Western blotting and qRT-PCR assays were chosen to detect the expression of proteins and genes. The anti-OSCC efficacy of Pri in vivo was evaluated by CAL-27 xenografts.

RESULTS

We showed that Pri inhibited the proliferation of human OSCC cell lines. Additionally, Pri induced apoptosis by upregulating Noxa expression. Furthermore, Pri treatment triggered excessive endoplasmic reticulum (ER) stress activation and subsequently induced c-Jun N-terminal kinase (JNK) signaling. ROS scavengers and ER stress inhibitors significantly attenuated Pri-induced OSCC cell apoptosis. Finally, Pri suppressed tumor growth in CAL-27 xenografts, accompanied ER stress activation and cell apoptosis.

CONCLUSION

These results reveal that Pri suppressed tumor growth and triggered cell apoptosis through ER stress activation in OSCC cells and xenografts, suggesting that Pri may serve as a therapeutic agent for OSCC.

Hepatokine Pregnancy Zone Protein Governs the Diet-Induced Thermogenesis Through Activating Brown Adipose Tissue

Intermittent fasting (IF), as a dietary intervention for weight loss, takes effects primarily through increasing energy expenditure. However, whether inter-organ systems play a key role in IF remains unclear. Here, a novel hepatokine, pregnancy zone protein (PZP) is identified, which has significant induction during the refeeding stage of IF. Further, loss of function studies and protein therapeutic experiment in mice revealed that PZP promotes diet-induced thermogenesis through activating brown adipose tissue (BAT). Mechanistically, circulating PZP can bind to cell surface glucose-regulated protein of 78 kDa (GRP78) to promote uncoupling protein 1 (UCP1) expression via a p38 MAPK-ATF2 signaling pathway in BAT. These studies illuminate a systemic regulation in which the IF promotes BAT thermogenesis through the endocrinal system and provide a novel potential target for treating obesity and related disorders.

HNRNPA2B1 regulates tamoxifen- and fulvestrant-sensitivity and hallmarks of endocrine resistance in breast cancer cells

Despite new combination therapies improving survival of breast cancer patients with estrogen receptor α (ER+) tumors, the molecular mechanisms for endocrine-resistant disease remain unresolved. Previously we demonstrated that expression of the RNA binding protein and N6-methyladenosine (m6A) reader HNRNPA2B1 (A2B1) is higher in LCC9 and LY2 tamoxifen (TAM)-resistant ERα breast cancer cells relative to parental TAM-sensitive MCF-7 cells. Here we report that A2B1 protein expression is higher in breast tumors than paired normal breast tissue. Modest stable overexpression of A2B1 in MCF-7 cells (MCF-7-A2B1 cells) resulted in TAM- and fulvestrant- resistance whereas knockdown of A2B1 in LCC9 and LY2 cells restored TAM and fulvestrant, endocrine-sensitivity. MCF-7-A2B1 cells gained hallmarks of TAM-resistant metastatic behavior: increased migration and invasion, clonogenicity, and soft agar colony size, which were attenuated by A2B1 knockdown in MCF-7-A2B1 and the TAM-resistant LCC9 and LY2 cells. MCF-7-A2B1, LCC9, and LY2 cells have a higher proportion of CD44+/CD24-/low cancer stem cells (CSC) compared to MCF-7 cells. MCF-7-A2B1 cells have increased ERα and reduced miR-222-3p that targets ERα. Like LCC9 cells, MCF-7-A2B1 have activated AKT and MAPK that depend on A2B1 expression and are growth inhibited by inhibitors of these pathways. These data support that targeting A2B1 could provide a complimentary therapeutic approach to reduce acquired endocrine resistance.

The double-stranded RNA-dependent protein kinase inhibitor alleviates endoplasmic reticulum stress and alleviates sepsis-induced renal injury

The double-stranded RNA-dependent protein kinase (PKR) is involved in inflammatory cytokine expression and disease pathogenesis in many conditions. The aim of this study was to explore the role of PKR in sepsis-induced renal tissue injury. Six-week-old C57BL/6J mice received PKR inhibitor (imoxin) and Endoplasmic reticulum (ER) inducer (tunicamycin) 2 hr prior to induction of inflammation via cecal ligation and puncture (CLP). Renal tissues were collected 24 hr after the CLP treatment and protein expression were assessed. The expression of creatinine (Cre) and blood urea nitrogen (BUN) in serum and inflammation factor in tissues was detected by ELISA, and the apoptosis of renal tissue was detected by TUNEL staining. PKR inhibitors reduce the expression of sepsis-induced ER stress in renal tissue, as well as the pathological changes and renal impairment in renal tissue. PKR inhibitors reduce the expression of sepsis-induced inflammatory response and sepsis-induced apoptosis in renal tissue by ER stress. In conclusion, PKR inhibitor alleviates ER stress and alleviates sepsis-induced renal injury.

Experimental models of endocrine responsive breast cancer: strengths, limitations, and use

Breast cancers characterized by expression of estrogen receptor-alpha (ER; ESR1) represent approximately 70% of all new cases and comprise the largest molecular subtype of this disease. Despite this high prevalence, the number of adequate experimental models of ER+ breast cancer is relatively limited. Nonetheless, these models have proved very useful in advancing understanding of how cells respond to and resist endocrine therapies, and how the ER acts as a transcription factor to regulate cell fate signaling. We discuss the primary experimental models of ER+ breast cancer including 2D and 3D cultures of established cell lines, cell line- and patient-derived xenografts, and chemically induced rodent models, with a consideration of their respective general strengths and limitations. What can and cannot be learned easily from these models is also discussed, and some observations on how these models may be used more effectively are provided. Overall, despite their limitations, the panel of models currently available has enabled major advances in the field, and these models remain central to the ability to study mechanisms of therapy action and resistance and for hypothesis testing that would otherwise be intractable or unethical in human subjects.

Are cachexia-associated tumors transmitTERS of ER stress?

Cancer cachexia is associated with deficient response to chemotherapy. On the other hand, the tumors of cachectic patients remarkably express more chemokines and have higher immune infiltration. For immunogenicity, a strong induction of the unfolded protein response (UPR) is necessary. UPR followed by cell surface exposure of calreticulin on the dying tumor cell is essential for its engulfment by macrophages and dendritic cells. However, some tumor cells upon endoplasmic reticulum (ER) stress can release factors that induce ER stress to other cells, in the so-called transmissible ER stress (TERS). The cells that received TERS produce more interleukin 6 (IL-6) and chemokines and acquire resistance to subsequent ER stress, nutrient deprivation, and genotoxic stress. Since ER stress enhances the release of extracellular vesicles (EVs), we suggest they can mediate TERS. It was found that ER stressed cachexia-inducing tumor cells transmit factors that trigger ER stress in other cells. Therefore, considering the role of EVs in cancer cachexia, the release of exosomes can possibly play a role in the process of blunting the immunogenicity of the cachexia-associated tumors. We propose that TERS can cause an inflammatory and immunosuppressive phenotype in cachexia-inducing tumors.

Dihydromyricetin Imbues Antiadipogenic Effects on 3T3-L1 Cells via Direct Interactions with 78-kDa Glucose-Regulated Protein

BACKGROUND

Obesity is among the most serious public health problems worldwide, with few safe pharmaceutical interventions. Natural products have become an important source of potential anti-obesity therapeutics. Dihydromyricetin (DHM) exerts antidiabetic effects. The biochemical target of DHM, however, has been unknown. It is crucial to identify the biochemical target of DHM for elucidating its physiological function and therapeutic value.

OBJECTIVES

The objective of this study was to identify the biochemical target of DHM.

METHODS

An abundant antiadipogenic flavanonol was extracted from the herbal plant Ampelopsis grossedentata through bioassay-guided fractionation and characterized with high-resolution LC-MS and 1H and 13C nuclear magnetic resonance. Antiadipogenic experiments were done with mouse 3T3-L1 preadipocytes. A biochemical target of the chemical of interest was identified with drug affinity responsive target stability assay. Direct interactions between the chemical of interest and the protein target in vitro were predicted with molecular docking and subsequently confirmed with surface plasmon resonance. Expression levels of peroxisome proliferator-activated receptor γ (PPARγ), which is associated with 78-kDa glucose-regulated protein (GRP78), were measured with real-time qPCR.

RESULTS

DHM was isolated, purified, and structurally characterized. Cellular studies showed that DHM notably reduced intracellular oil droplet formation in 3T3-L1 cells with a median effective concentration of 294 μM (i.e., 94 μg/mL). DHM targeted the ATP binding site of GRP78, which is associated with adipogenesis. An equilibrium dissociation constant between DHM and GRP78 was 21.8 μM. In 3T3-L1 cells upon treatment with DHM at 50 μM (i.e., 16 μg/mL), the expression level of PPARγ was downregulated to 53.9% of the solvent vehicle control's level.

CONCLUSIONS

DHM targets GRP78 in vitro. DHM is able to reduce lipid droplet formation in 3T3-L1 cells through a mode of action that is plausibly associated with direct interactions between GRP78 and DHM, which is a step forward in determining potential applications of DHM as an anti-obesity agent.

Tagitinin C induces ferroptosis through PERK-Nrf2-HO-1 signaling pathway in colorectal cancer cells

Rationale: Colorectal cancer (CRC) is a common malignant tumor of the digestive system. However, the efficacy of surgery and chemotherapy is limited. Ferroptosis is an iron- and reactive oxygen species (ROS)-dependent form of regulated cell death (RCD) and plays a vital role in tumor suppression. Ferroptosis inducing agents have been studied extensively as a novel promising way to fight against therapy resistant cancers. The aim of this study is to investigate the mechanism of action of tagitinin C (TC), a natural product, as a novel ferroptosis inducer in tumor suppression. Methods: The response of CRC cells to tagitinin C was assessed by cell viability assay, clonogenic assay, transwell migration assay, cell cycle assay and apoptosis assay. Molecular approaches including Western blot, RNA sequencing, quantitative real-time PCR and immunofluorescence were employed as well. Results: Tagitinin C, a sesquiterpene lactone isolated from Tithonia diversifolia, inhibits the growth of colorectal cancer cells including HCT116 cells, and induced an oxidative cellular microenvironment resulting in ferroptosis of HCT116 cells. Tagitinin C-induced ferroptosis was accompanied with the attenuation of glutathione (GSH) levels and increased in lipid peroxidation. Mechanistically, tagitinin C induced endoplasmic reticulum (ER) stress and oxidative stress, thus activating nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). As a downstream gene (effector) of Nrf2, heme oxygenase-1 (HO-1) expression increased significantly with the treatment of tagitinin C. Upregulated HO-1 led to the increase in the labile iron pool, which promoted lipid peroxidation, meanwhile tagitinin C showed synergistic anti-tumor effect together with erastin. Conclusion: In summary, we provided the evidence that tagitinin C induces ferroptosis in colorectal cancer cells and has synergistic effect together with erastin. Mechanistically, tagitinin C induces ferroptosis through ER stress-mediated activation of PERK-Nrf2-HO-1 signaling pathway. Tagitinin C, identified as a novel ferroptosis inducer, may be effective chemosensitizer that can expand the efficacy and range of chemotherapeutic agents.

Protein profile of MCF-7 breast cancer cell line treated with lectin delivered by CaCO3NPs revealed changes in molecular chaperones, cytoskeleton, and membrane-associated proteins

The second most predominant cancer in the world and the first among women is breast cancer. We aimed to study the protein abundance profiles induced by lectin purified from the Agaricus bisporus mushroom (ABL) and conjugated with CaCO₃NPs in the MCF-7 breast cancer cell line. Two-dimensional electrophoresis (2-DE) and orbitrap mass spectrometry techniques were used to reveal the protein abundance pattern induced by lectin. Flow cytometric analysis showed the accumulation of ABL-CaCO₃NPs treated cells in the G1 phase than the positive control. Thirteen proteins were found different in their abundance in breast cancer cells after 24 h exposure to lectin conjugated with CaCO₃NPs. Most of the identified proteins were showing a low abundance in ABL-CaCO₃NPs treated cells in comparison to the positive and negative controls, including V-set and immunoglobulin domain, serum albumin, actin cytoplasmic 1, triosephosphate isomerase, tropomyosin alpha-4 chain, and endoplasmic reticulum chaperone BiP. Hornerin, tropomyosin alpha-1 chain, annexin A2, and protein disulfide-isomerase were up-regulated in comparison to the positive. Bioinformatic analyses revealed the regulation changes of these proteins mainly affected the pathways of 'Bcl-2-associated athanogene 2 signalling pathway', 'Unfolded protein response', 'Caveolar-mediated endocytosis signalling', 'Clathrin-mediated endocytosis signalling', 'Calcium signalling' and 'Sucrose degradation V', which are associated with breast cancer. We concluded that lectin altered the abundance in molecular chaperones/heat shock proteins, cytoskeletal, and metabolic proteins. Additionally, lectin induced a low abundance of MCF-7 cancer cell proteins in comparison to the positive and negative controls, including; V-set and immunoglobulin domain, serum albumin, actin cytoplasmic 1, triosephosphate isomerase, tropomyosin alpha-4 chain, and endoplasmic reticulum chaperone BiP.

Noninvasive Classification of Human Triple Negative Breast Cancer by PET Imaging with GRP78-Targeted Molecular Probe [68Ga]DOTA-VAP

PURPOSE

There is currently no effective noninvasive method for accurate molecular typing of triple negative breast cancer (TNBC) except needle biopsy. Glucoregulated Protein 78 (GRP78) is overexpressed in TNBC cells and tumors which closely related to the invasion, metastasis, and drug resistance of cancer. Meanwhile, it has been verified that VAP peptide bind specifically to GRP78 in vitro and in vivo. In this study, we constructed a GRP78-targeted molecular probe Ga-68-radiolabeled DOTA-VAP conjugate ([⁶⁸Ga]DOTA-VAP) based on VAP peptide, and evaluated its potential to distinguish TNBC from non-TNBC tumors.

PROCEDURES

DOTA-VAP was synthesized and then radiolabeled with Ga-68 to obtain [⁶⁸Ga]DOTA-VAP. The expression of GRP78 in TNBC MDA-MB-231 and non-TNBC MCF-7 cells was validated by Western Blot, and cell binding or uptake experiments with both [⁶⁸Ga]DOTA-VAP and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) were also performed. Biodistribution analysis and positron emission tomography (PET) imaging of [⁶⁸Ga]DOTA-VAP were carried out in subcutaneous MDA-MB-231 and MCF-7 human breast cancer tumor models with [¹⁸F]FDG PET imaging as comparison.

RESULTS

[⁶⁸Ga]DOTA-VAP was prepared with high radiochemical purity which showed excellent stability in vitro. The MDA-MB-231 tumors were clearly visualized by [⁶⁸Ga]DOTA-VAP PET imaging with a low background, except for the relatively high liver uptake. Cells and tumors of MDA-MB-231 could be distinguished from MCF-7 by [⁶⁸Ga]DOTA-VAP instead of [¹⁸F]FDG. Biodistribution results were consistent with the imaging results. The blocking study with excess cold peptide showed significantly reduced tumor uptake, which indicated the specificity of [⁶⁸Ga]DOTA-VAP targeting MDA-MB-231 tumors in vivo.

CONCLUSIONS

GRP78-targeted PET imaging with [⁶⁸Ga]DOTA-VAP provided an effective approach for the noninvasive accurate classification of TNBC from other breast cancer subtypes comparing with [¹⁸F]FDG. GRP78 may be a potential target for the diagnosis and treatment of TNBC. For clinical transformation, efforts should be made to overcome deficiencies of [⁶⁸Ga]DOTA-VAP such as relative high uptake in normal tissues.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ENR) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are upregulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation upregulates SOX2OT expression. This upregulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ENR stress reprogramming of breast cancer cells.

Naringin attenuates cerebral ischemia-reperfusion injury in rats by inhibiting endoplasmic reticulum stress

Objective

This investigation was carried out with an aim of exploring neuroprotection by naringin (Nar) in rats with cerebral ischemia-reperfusion (CI/R) injury and its mechanism.

Methods

Rats were grouped into ischemia-reperfusion (I/R), sham operation (Sham), nimodipine control (NIM), and different doses of Nar (Nar-L, Nar-M, Nar-H) groups. With Zea Longa score for assessment of neurological deficits, dry and wet method for measurement of brain tissue water content, and (2,3,5-triphenyltetrazolium chloride) TTC staining for determination of cerebral infarction volume, the related parameters were obtained and compared. Subsequently, ELISA was introduced to detect levels of proinflammatory cytokines (TNF-α, IL-8) and anti-inflammatory cytokine (IL-10) in the serum as well as superoxide dismutase (SOD) and malondialdehyde (MDA) activities in brain tissue. Western blot was applied to evaluate endoplasmic reticulum stress (ERS)-related proteins expression, including glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), caspase-12, and activating transcription factor 6 (ATF-6).

Results

Nar significantly alleviated nerve injury and decreased brain tissue water content and brain infraction volume in CI/R injury rats in a concentration-dependent manner. Reduction of TNF-α, IL-8 as well as MDA content and elevation of IL-10 as well as SOD activity were confirmed to be caused by Nar treatment in a concentration-dependent manner. Meanwhile, ERS-related proteins also markedly decreased in the Nar groups.

Conclusion

Nar may achieve neuroprotection and alleviation of CI/R injury by anti-inflammation, anti-oxidation, and inhibiting ERS, and its efficacy is concentration-dependent.

The Immunology of Hormone Receptor Positive Breast Cancer

Immune checkpoint blockade (ICB) has revolutionized the treatment of cancer patients. The main focus of ICB has been on reinvigorating the adaptive immune response, namely, activating cytotoxic T cells. ICB has demonstrated only modest benefit against advanced breast cancer, as breast tumors typically establish an immune suppressive tumor microenvironment (TME). Triple-negative breast cancer (TNBC) is associated with infiltration of tumor infiltrating lymphocytes (TILs) and patients with TNBC have shown clinical responses to ICB. In contrast, hormone receptor positive (HR+) breast cancer is characterized by low TIL infiltration and minimal response to ICB. Here we review how HR+ breast tumors establish a TME devoid of TILs, have low HLA class I expression, and recruit immune cells, other than T cells, which impact response to therapy. In addition, we review emerging technologies that have been employed to characterize components of the TME to reveal that tumor associated macrophages (TAMs) are abundant in HR+ cancer, are highly immune-suppressive, associated with tumor progression, chemotherapy and ICB-resistance, metastasis and poor survival. We reveal novel therapeutic targets and possible combinations with ICB to enhance anti-tumor immune responses, which may have great potential in HR+ breast cancer.

Functions of Thrombospondin-1 in the Tumor Microenvironment

The identification of thrombospondin-1 as an angiogenesis inhibitor in 1990 prompted interest in its role in cancer biology and potential as a therapeutic target. Decreased thrombospondin-1 mRNA and protein expression are associated with progression in several cancers, while expression by nonmalignant cells in the tumor microenvironment and circulating levels in cancer patients can be elevated. THBS1 is not a tumor suppressor gene, but the regulation of its expression in malignant cells by oncogenes and tumor suppressor genes mediates some of their effects on carcinogenesis, tumor progression, and metastasis. In addition to regulating angiogenesis and perfusion of the tumor vasculature, thrombospondin-1 limits antitumor immunity by CD47-dependent regulation of innate and adaptive immune cells. Conversely, thrombospondin-1 is a component of particles released by immune cells that mediate tumor cell killing. Thrombospondin-1 differentially regulates the sensitivity of malignant and nonmalignant cells to genotoxic stress caused by radiotherapy and chemotherapy. The diverse activities of thrombospondin-1 to regulate autophagy, senescence, stem cell maintenance, extracellular vesicle function, and metabolic responses to ischemic and genotoxic stress are mediated by several cell surface receptors and by regulating the functions of several secreted proteins. This review highlights progress in understanding thrombospondin-1 functions in cancer and the challenges that remain in harnessing its therapeutic potential.

Planarians (Platyhelminthes)-An Emerging Model Organism for Investigating Innate Immune Mechanisms

An organism responds to the invading pathogens such as bacteria, viruses, protozoans, and fungi by engaging innate and adaptive immune system, which functions by activating various signal transduction pathways. As invertebrate organisms (such as sponges, worms, cnidarians, molluscs, crustaceans, insects, and echinoderms) are devoid of an adaptive immune system, and their defense mechanisms solely rely on innate immune system components. Investigating the immune response in such organisms helps to elucidate the immune mechanisms that vertebrates have inherited or evolved from invertebrates. Planarians are non-parasitic invertebrates from the phylum Platyhelminthes and are being investigated for several decades for understanding the whole-body regeneration process. However, recent findings have emerged planarians as a useful model for studying innate immunity as they are resistant to a broad spectrum of bacteria. This review intends to highlight the research findings on various antimicrobial resistance genes, signaling pathways involved in innate immune recognition, immune-related memory and immune cells in planarian flatworms.

Calcium mitigates fluoride-induced kallikrein 4 inhibition via PERK/eIF2α/ATF4/CHOP endoplasmic reticulum stress pathway in ameloblast-lineage cells

OBJECTIVES

The present study aimed to investigated the effect and mechanism of Ca²⁺ treatment on fluoride in ameloblast-lineage cells (ALCs).

MATERIALS AND METHODS

The effects of fluoride and different Ca²⁺ levels treatment on the proliferative activity, cell apoptosis, cell cycle, intracellular free Ca²⁺, were firstly determined. Kallikrein 4 (KLK4), glucose-responsive protein 78 (GRP78), Protein kinase R -like endoplasmic reticulum kinase (PERK), the α subunit of eukaryotic initiation factor 2 (eIF2α), activating transcription factor 4 (ATF4), CCAAT enhancer-binding protein homologous protein (CHOP), were investigated in ALCs.

RESULTS

The proliferative activity was obviously inhibited under concentrations of single fluoride high than 1 mM, and indicated highest proliferation at single 2.5 mM Ca²⁺ concentration in ALC cells. In addition, we found that single fluoride markedly induced intracellular free Ca²⁺ increasing, G2/M phase arrest, apoptosis. GRP78 and endoplasmic reticulum stress pathway of PERK/eIF2α/ATF4/CHOP were significantly increased, while the proliferation and KLK4 were markedly reduced in ALCs. Ca²⁺ additional treatment can obviously reverse the effect of fluoride-induced apoptosis and inhibition of KLK4. The effect of GRP78 and endoplasmic reticulum stress pathway of PERK/eIF2α/ATF4/CHOP were also alleviated under Ca²⁺ additional treatment in ALCs. More important, the results of 2.5 mmol/L Ca²⁺ treatment on the proliferation, cell cycle and apoptosis suggest this concentration is relatively better to mediate the intracellular Ca²⁺ homeostasis in ALCs.

CONCLUSIONS

In sum, Ca²⁺-supplementation exerts antagonistic the toxic effects on fluoride and this inhibitory effect suggests the potential implications for Ca²⁺-supplementation on fluorosis.

Rosa canina L. Can Restore Endoplasmic Reticulum Alterations, Protein Trafficking and Membrane Integrity in a Dextran Sulfate Sodium-Induced Inflammatory Bowel Disease Phenotype

Rosa canina L. is a natural polyphenol-rich medicinal plant that exhibits antioxidant and anti-inflammatory activities. Recent in vivo studies have demonstrated that a methanol extract of Rosa canina L. (RCME) has reversed an inflammatory bowel disease (IBD)-like phenotype that has been triggered by dextran sulfate sodium (DSS) in mice. In the current study, we investigated the effects of RCME on perturbations of cellular mechanisms induced by DSS-treatment of intestinal Caco-2 cells, including stress response in the endoplasmic reticulum (ER), protein trafficking and sorting as well as lipid rafts integrity and functional capacities of an intestinal enzyme. 6 days post-confluent cells were treated for 24 h with DSS (3%) or simultaneously with DSS (3%) and RCME (100 µg/mL) or exclusively with RCME (100 µg/mL) or not treated. The results obtained demonstrate the ability of RCME to counteract the substantial increase in the expression levels of several ER stress markers in DSS-treated cells. Concomitantly, the delayed trafficking of intestinal membrane glycoproteins sucrase-isomaltase (SI) and dipeptidyl peptidase 4 (DPP4) induced by DSS between the ER and the Golgi has been compromised by RCME. Furthermore, RCME restored the partially impaired polarized sorting of SI and DPP4 to the brush border membrane. An efficient sorting mechanism of SI and DPP4 is tightly associated with intact lipid rafts structures in the trans-Golgi network (TGN), which have been distorted by DSS and normalized by RCME. Finally, the enzymatic activities of SI are enhanced in the presence of RCME. Altogether, DSS treatment has triggered ER stress, impaired trafficking and function of membrane glycoproteins and distorted lipid rafts, all of which can be compromised by RCME. These findings indicate that the antioxidants in RCME act at two major sites in Caco-2 cells, the ER and the TGN and are thus capable of maintaining the membrane integrity by correcting the sorting of membrane-associated proteins.

Unfolded protein response in colorectal cancer

Colorectal cancer (CRC) is a gastrointestinal malignancy originating from either the colon or the rectum. A growing number of researches prove that the unfolded protein response (UPR) is closely related to the occurrence and progression of colorectal cancer. The UPR has three canonical endoplasmic reticulum (ER) transmembrane protein sensors: inositol requiring kinase 1 (IRE1), pancreatic ER eIF2α kinase (PERK), and activating transcription factor 6 (ATF6). Each of the three pathways is closely associated with CRC development. The three pathways are relatively independent as well as interrelated. Under ER stress, the activated UPR boosts the protein folding capacity to maximize cell adaptation and survival, whereas sustained or excessive ER triggers cell apoptosis conversely. The UPR involves different stages of CRC pathogenesis, promotes or hinders the progression of CRC, and will pave the way for novel therapeutic and diagnostic approaches. Meanwhile, the correlation between different signal branches in UPR and the switch between the adaptation and apoptosis pathways still need to be further investigated in the future.

CD47 (Cluster of Differentiation 47)

CD47, also known as integrin-associated protein, is a constitutively and ubiquitously expressed transmembrane receptor. CD47 is conserved across amniotes including mammals, reptiles, and birds. Expression is increased in many cancers and, in non-malignant cells, by stress and with aging. The up-regulation of CD47 expression is generally epigenetic, whereas gene amplification occurs with low frequency in some cancers. CD47 is a high affinity signaling receptor for the secreted protein thrombospondin-1 (THBS1) and the counter-receptor for signal regulatory protein-α (SIRPA, SIRPα) and SIRPγ (SIRPG). CD47 interaction with SIRPα serves as a marker of self to innate immune cells and thereby protects cancer cells from phagocytic clearance. Consequently, higher CD47 correlates with a poor prognosis in some cancers, and therapeutic blockade can suppress tumor growth by enhancing innate antitumor immunity. CD47 expressed on cytotoxic T cells, dendritic cells, and NK cells mediates inhibitory THBS1 signaling that further limits antitumor immunity. CD47 laterally associates with several integrins and thereby regulates cell adhesion and migration. CD47 has additional lateral binding partners in specific cell types, and ligation of CD47 in some cases modulates their function. THBS1-CD47 signaling in non-malignant cells inhibits nitric oxide/cGMP, calcium, and VEGF signaling, mitochondrial homeostasis, stem cell maintenance, protective autophagy, and DNA damage response, and promotes NADPH oxidase activity. CD47 signaling is a physiological regulator of platelet activation, angiogenesis and blood flow. THBS1/CD47 signaling is frequently dysregulated in chronic diseases.

Lipid Metabolism and Immune Checkpoints

Immune checkpoints are essential for the regulation of immune cell functions. Although the abrogation of immunosurveillance of tumor cells is known, the regulators of immune checkpoints are not clear. Lipid metabolism is one of the important metabolic activities in organisms. In lipid metabolism, a large number of metabolites produced can regulate the gene expression and activation of immune checkpoints through various pathways. In addition, increasing evidence has shown that lipid metabolism leads to transient generation or accumulation of toxic lipids that result in endoplasmic reticulum (ER) stress and then regulate the transcriptional and posttranscriptional modifications of immune checkpoints, including transcription, protein folding, phosphorylation, palmitoylation, etc. More importantly, the lipid metabolism can also affect exosome transportation of checkpoints and the degradation of checkpoints by affecting ubiquitination and lysosomal trafficking. In this chapter, we mainly empathize on the roles of lipid metabolism in the regulation of immune checkpoints, such as gene expression, activation, and degradation.

Emerging Landscapes of Tumor Immunity and Metabolism

The metabolic reprogramming of cancer tissue has higher metabolic activity than surrounding tissues. At the same time, the local infiltration of immunosuppressive cells is also significantly increased, resulting in a significant decrease in tumor immunity. During the progression of cancer cells, immunosuppressive tumor microenvironment is formed around the tumor due to their metabolic reprogramming. In addition, it is the changes in metabolic patterns that make tumor cells resistant to certain drugs, impeding cancer treatment. This article reviews the mechanisms of immune escape caused by metabolic reprogramming, and aims to provide new ideas for clinical tumor immunotherapy combined with metabolic intervention for tumor treatment.

Dual blockade of CD47 and HER2 eliminates radioresistant breast cancer cells

Although the efficacy of cancer radiotherapy (RT) can be enhanced by targeted immunotherapy, the immunosuppressive factors induced by radiation on tumor cells remain to be identified. Here, we report that CD47-mediated anti-phagocytosis is concurrently upregulated with HER2 in radioresistant breast cancer (BC) cells and RT-treated mouse syngeneic BC. Co-expression of both receptors is more frequently detected in recurrent BC patients with poor prognosis. CD47 is upregulated preferentially in HER2-expressing cells, and blocking CD47 or HER2 reduces both receptors with diminished clonogenicity and augmented phagocytosis. CRISPR-mediated CD47 and HER2 dual knockouts not only inhibit clonogenicity but also enhance macrophage-mediated attack. Dual antibody of both receptors synergizes with RT in control of syngeneic mouse breast tumor. These results provide the evidence that aggressive behavior of radioresistant BC is caused by CD47-mediated anti-phagocytosis conjugated with HER2-prompted proliferation. Dual blockade of CD47 and HER2 is suggested to eliminate resistant cancer cells in BC radiotherapy.

Lipid-mediated regulation of the cancer-immune crosstalk

Besides acting as principle cellular building blocks and energy reservoirs, lipids also carry important signals associated with many fundamental cell biological processes, such as proliferation, differentiation, migration, stress responses and cell demise. Hyperactive lipid metabolism is closely associated with cancer progression and unfavorable outcomes. The underlying mechanisms are being gradually deciphered. In this review, we aim to summarize recent advances on how reprogrammed lipid metabolism and accompanying signaling cascades directly modulate cancer cells, as well as influencing stromal cells and immune cells within the tumor microenvironment. For future studies, special attention should be paid to lipid-mediated crosstalk among cancer cells, their neighboring stromal cells, and immune cells, plus how these multi-level communications determine anti-tumor immunity and bring novel immunotherapeutic opportunities.

Targeting the GRP78 Pathway for Cancer Therapy

The 78-kDa glucose-regulated protein (GRP78) plays an important part in maintaining protein stability, regulating protein folding, and inducing apoptosis autophagy, which is considered as a powerful protein. Meanwhile, it also plays a role in ensuring the normal function of organs. In recent years, more and more researches have been carried out on the targeted therapy of GRP78, mainly focusing on its relevant role in tumor and its role as a major modulator and modulator of subordinate pathways. The ability of GRP78 to respond to endoplasmic reticulum stress (ERS) determines whether tumor cells survive and whether the changes in expression level of GRP78 regulated by endoplasmic reticulum (ER) caused by various factors will directly or indirectly affect cell proliferation, apoptosis, and injury, or reduce the body's defense ability, or have protective effects on various organs.

Exploring the Regulation Mechanism of Xihuang Pill, Olibanum and β-Boswellic Acid on the Biomolecular Network of Triple-Negative Breast Cancer Based on Transcriptomics and Chemical Informatics Methodology

Background

Xihuang Pill (XHP) is mainly used to treat “Ru Yan (breast cancer)”. Evidence-based medical evidence and showed that XHP improves the efficacy of chemotherapy and reduced chemotherapy-induced toxicity in breast cancer patients. However, the mechanism of XHP against breast cancer is not clear.

Methods

The effect of XHP extract on cell half-inhibitory concentration (IC50) and cell viability of MD-MB-231 cells was detected by CCK-8 method. The cell inhibition rate of MDA-MB-453 cells were detected by MTT method. Apoptosis was detected by flow cytometry, cell transfer ability was detected by Transwell method, and cell proliferation ability was detected by colony formation assay. The expression of Notch1, β-catenin and c-myc mRNA in MDA-MB-453 cells were detected by real-time fluorescence quantitative PCR. Then, chemical informatics and transcriptomics methodology was utilized to predict the potential compounds and targets of XHP, and collect triple negative breast cancer (TNBC) genes and the data of Olibanum and β-boswellic acid intervention MD-MB-231 cells (from GSE102891). The cytoscape software was utilized to undergo network construction and network analysis. Finally, the data from the network analysis was imported into the DAVID database for enrichment analysis of signaling pathways and biological processes.

Results

The IC50 was 15.08 g/L (for MD-MB-231 cells). After interfering with MD-MB-231 cells with 15.08 g/L XHP extract for 72 h, compared with the control group, the cell viability, migration and proliferation was significantly decreased, while early apoptosis and late apoptosis were significantly increased (P < 0.01). After interfering with MDA-MB-453 cells with 6 g/L XHP extract for 72 h, compared with the control group, the cell inhibition and apoptosis rate increased, while the expression of Notch1, β-catenin and c-myc mRNA decreased. (P < 0.05). The chemical informatics and transcriptomics analysis showed that four networks were constructed and analyzed: (1) potential compounds-potential targets network of XHP; (2) XHP-TNBC PPI network; (3) DEGs PPI network of Olibanum-treated MD-MB 231 cells; (4) DEGs PPI network of β-boswellic acid -treated MD-MB 231 cells. Several anti-TNBC biological processes, signaling pathways, targets and so on were obtained.

Conclusion

XHP may exert anti-TNBC effects through regulating biological processes, signaling pathways, targets found in this study.

IRE1α regulates macrophage polarization, PD-L1 expression, and tumor survival

In the tumor microenvironment, local immune dysregulation is driven in part by macrophages and dendritic cells that are polarized to a mixed proinflammatory/immune-suppressive phenotype. The unfolded protein response (UPR) is emerging as the possible origin of these events. Here we report that the inositol-requiring enzyme 1 (IRE1α) branch of the UPR is directly involved in the polarization of macrophages in vitro and in vivo, including the up-regulation of interleukin 6 (IL-6), IL-23, Arginase1, as well as surface expression of CD86 and programmed death ligand 1 (PD-L1). Macrophages in which the IRE1α/X-box binding protein 1 (Xbp1) axis is blocked pharmacologically or deleted genetically have significantly reduced polarization and CD86 and PD-L1 expression, which was induced independent of IFNγ signaling, suggesting a novel mechanism in PD-L1 regulation in macrophages. Mice with IRE1α- but not Xbp1-deficient macrophages showed greater survival than controls when implanted with B16.F10 melanoma cells. Remarkably, we found a significant association between the IRE1α gene signature and CD274 gene expression in tumor-infiltrating macrophages in humans. RNA sequencing (RNASeq) analysis showed that bone marrow-derived macrophages with IRE1α deletion lose the integrity of the gene connectivity characteristic of regulated IRE1α-dependent decay (RIDD) and the ability to activate CD274 gene expression. Thus, the IRE1α/Xbp1 axis drives the polarization of macrophages in the tumor microenvironment initiating a complex immune dysregulation leading to failure of local immune surveillance.

Thrombospondin-1 counteracts the p97 inhibitor CB-5083 in colon carcinoma cells

p97 has recently emerged as a therapeutic target for cancer due to its essential functions in protein homeostasis. CB-5083 is a first-in-class, potent and selective ATP-competitive p97 inhibitor that induces proteotoxic stress in cancer cells. Potential mechanisms regulating the sensitivity of cells to p97 inhibition remain poorly studied. Here, we demonstrate that Thrombospondin-1 (THBS1) is a CB-5083-upregulated gene that helps confer resistance of HCT116 cells to CB-5083. Our immunoblotting and immunofluorescence data showed that CB-5083 significantly increases the steady-state abundance of THBS1. Blockade of THBS1 induction sensitized cells to CB-5083-mediated growth inhibition. Suppression of THBS1 caused an increase of CB-5083-induced sub-G1 population and caspase 3/7 activity suggesting that its function is linked to the survival of cancer cells in response to p97 inhibition. Altogether our data provide new evidence that THBS1 is important for the susceptibility of cells to p97 inhibition.

KSHV infection skews macrophage polarisation towards M2-like/TAM and activates Ire1 α-XBP1 axis up-regulating pro-tumorigenic cytokine release and PD-L1 expression

Background

Kaposi’s Sarcoma Herpesvirus (KSHV) is a gammaherpesvirus strongly linked to human cancer. The virus is also able to induce immune suppression, effect that contributes to onset/progression of the viral-associated malignancies. As KSHV may infect macrophages and these cells abundantly infiltrate Kaposi’s sarcoma lesions, in this study we investigated whether KSHV-infection could affect macrophage polarisation to promote tumorigenesis.

Methods

FACS analysis was used to detect macrophage markers and PD-L1 expression. KSHV infection and the molecular pathways activated were investigated by western blot analysis and by qRT-PCR while cytokine release was assessed by Multi-analyte Kit.

Results

We found that KSHV infection reduced macrophage survival and skewed their polarisation towards M2 like/TAM cells, based on the expression of CD163, on the activation of STAT3 and STAT6 pathways and the release of pro-tumorigenic cytokines such as IL-10, VEGF, IL-6 and IL-8. We also found that KSHV triggered Ire1 α-XBP1 axis activation in infected macrophages to increase the release of pro-tumorigenic cytokines and to up-regulate PD-L1 surface expression.

Conclusions

The findings that KSHV infection of macrophages skews their polarisation towards M2/TAM and that activate Ire1 α-XBP1 to increase the release of pro-tumorigenic cytokines and the expression of PD-L1, suggest that manipulation of UPR could be exploited to prevent or improve the treatment of KSHV-associated malignancies.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ER) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are up-regulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression, and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation up-regulates SOX2OT expression. This up-regulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ER stress reprogramming of breast cancer cells.