HMGB1 knockdown increases MM cell vulnerability by regulating autophagy and DNA damage repair

Gfi-1 modulates HMGB1-Mediated autophagy to overcome oxaliplatin resistance in colorectal cancer

Background

Resistance to oxaliplatin (L-OHP) is a major barrier in the treatment of colorectal cancer (CRC). Autophagy is the main cause of L-OHP tolerance in CRC cells.

Method

The human colon cancer cell lines HCT116 and SW480 were treated with L-OHP to obtain the drug-resistant cell lines HCT116/L-OHP and SW480/L-OHP, respectively. To probe the relationship between autophagy and L-OHP tolerance of growth factor independent 1 (Gfi-1) and high-mobility group protein 1 (HMGB1) in CRC cells, gene knockout or overexpression was performed, and Western blotting was used to determine the levels of drug tolerance interrelated proteins. Transwell and CCK-8 assays were employed to analyze the proliferation of cancer cells. Immunofluorescence detection of LC3 reflected autophagy levels. Finally, the relationship between Gfi-1 and HMGB1 was detected by chromatin immunoprecipitation (ChIP).

Result

Compared to normal CRC cells, L-OHP-tolerant CRC cells exhibited greater autophagy (8.2 times greater in HCT116/L-OHP cells and 7.4 times greater in SW480/L-OHP cells). In addition, we detected low levels of Gfi-1 (0.6-fold for HCT116/L-OHP cells and 0.4-fold for SW480/L-OHP cells), and OE-Gfi-1 decreased HMGB1 levels (0.6-fold for HCT116/L-OHP + OE-Gfi-1 cells and 0.5-fold for SW480/L-OHP + OE-Gfi-1 cells). The inhibition of Gfi-1 further enhanced cell viability (1.7 times in HCT116+sh-Gfi-1 cells and 1.2 times in SW480+sh-Gfi-1 cells) and invasion (1.8 times in HCT116+sh-Gfi-1 cells and 2.1 times in SW480+sh-Gfi-1 cells) in CRC cells, thus promoting oxaliplatin resistance in these cells. The autophagy inhibitor 3-MA reversed the above effects. Furthermore, we noted that Gfi-1 can restrain HMGB1 expression by binding to its promoter (0.5 times in HCT116+OE-Gfi-1 cells and 0.5 times in SW480+OE-Gfi-1 cells). The inhibitory influence of 3-MA on HMGB1 reversed the influence of Gfi-1 on autophagy and malignant progression in CRC cells.

Conclusion

Our study suggested that Gfi-1 inhibited HMGB1 to reduce CRC autophagy levels, increasing CRC sensitivity to L-OHP.

The mechanism of high mobility group box-1 protein and its bidirectional regulation in tumors

High-mobility group box-1 protein (HMGB1) is a nonhistone chromatin-related protein widely found in eukaryotic cells. It is involved in the transcription, replication, and repair of DNA to maintain nuclear homeostasis. It participates in cell growth, differentiation, and signal transduction. Recent studies showed that HMGB1 has a bidirectional regulatory effect on tumors by regulating TLR4/MYD88/NF-κB and RAGE/AMPK/mTOR signaling pathways. On the one hand, it is highly expressed in a variety of tumors, promoting tumor proliferation and invasion, while on the other hand, it induces autophagy and apoptosis of tumor cells and stimulates tumor-infiltrating lymphocytes to produce an anti-tumor immune response. At present, HMGB1 could be used as a target to regulate the drug resistance and prognostication in cancer. Clinical applications of HMGB1 in cancer need further in-depth studies.

HMGB1 in the interplay between autophagy and apoptosis in cancer

Lysosome-mediated autophagy and caspase-dependent apoptosis are dynamic processes that maintain cellular homeostasis, ensuring cell health and functionality. The intricate interplay and reciprocal regulation between autophagy and apoptosis are implicated in various human diseases, including cancer. High-mobility group box 1 (HMGB1), a nonhistone chromosomal protein, plays a pivotal role in coordinating autophagy and apoptosis levels during tumor initiation, progression, and therapy. The regulation of autophagy machinery and the apoptosis pathway by HMGB1 is influenced by various factors, including the protein's subcellular localization, oxidative state, and interactions with binding partners. In this narrative review, we provide a comprehensive overview of the structure and function of HMGB1, with a specific focus on the interplay between autophagic degradation and apoptotic death in tumorigenesis and cancer therapy. Gaining a comprehensive understanding of the significance of HMGB1 as a biomarker and its potential as a therapeutic target in tumor diseases is crucial for advancing our knowledge of cell survival and cell death.

Autophagy-related mechanisms for treatment of multiple myeloma

Multiple myeloma (MM) is a type of hematological cancer that occurs when B cells become malignant. Various drugs such as proteasome inhibitors, immunomodulators, and compounds that cause DNA damage can be used in the treatment of MM. Autophagy, a type 2 cell death mechanism, plays a crucial role in determining the fate of B cells, either promoting their survival or inducing cell death. Therefore, autophagy can either facilitate the progression or hinder the treatment of MM disease. In this review, autophagy mechanisms that may be effective in MM cells were covered and evaluated within the contexts of unfolded protein response (UPR), bone marrow microenvironment (BMME), drug resistance, hypoxia, DNA repair and transcriptional regulation, and apoptosis. The genes that are effective in each mechanism and research efforts on this subject were discussed in detail. Signaling pathways targeted by new drugs to benefit from autophagy in MM disease were covered. The efficacy of drugs that regulate autophagy in MM was examined, and clinical trials on this subject were included. Consequently, among the autophagy mechanisms that are effective in MM, the most suitable ones to be used in the treatment were expressed. The importance of 3D models and microfluidic systems for the discovery of new drugs for autophagy and personalized treatment was emphasized. Ultimately, this review aims to provide a comprehensive overview of MM disease, encompassing autophagy mechanisms, drugs, clinical studies, and further studies.

Identification of evolutionary mechanisms of myelomatous effusion by single-cell RNA sequencing

Myelomatous effusion (ME) is a rare manifestation of extramedullary multiple myeloma (MM) with limited therapeutic options and poor outcomes. The molecular mechanisms underlying ME are incompletely understood. We profiled transcriptomes of bone marrow, peripheral blood (PB), and pleural effusion/ascites from 3 patients with ME using single-cell RNA sequencing analysis. We found that ME contained a higher percentage of cytotoxic T cells, whereas PB contained a higher proportion of naive T cells. Malignant cells varied within and between sites and patients in their expression of signatures. We identified a gene module highly expressed in intramedullary and extramedullary plasma cell clusters and defined cell clusters expressing this gene set as extramedullary-initiating cells (EMICs). This gene set was associated with increased cellular proliferation, involved in p53 signaling, and related to poor prognosis in MM. The transcriptional regulators E2F1, YY1, and SMAD1 were activated in EMICs. Leukocyte immunoglobulin-like receptor subfamily B4 (LILRB4) was upregulated in extramedullary EMICs. We confirmed that LILRB4 promoted MM cell migration in vitro. This study provided insight into the evolutionary mechanisms of ME and defined EMICs and LILRB4 associated with extramedullary development.

The role of High-mobility group box-1 and Psoriasin in multiple myeloma: Analysis of a population affected by monoclonal gammopathies and review of the literature

Multiple myeloma (MM) is a plasma cells neoplasm which is often preceded by a preneoplastic condition called monoclonal gammopathy of unknown significance (MGUS). A protein called High-mobility group box-1 (HMGB-1) controls transcription and genomic stability. Both pro- and anti-tumor properties of HMGB1 have been described during tumor growth. The S100 protein family includes a protein known as psoriasin. Poorer prognosis and survival were linked to higher psoriasin expression in cancer patients. The goal of the current investigation was to compare the plasma levels of HMGB-1 and psoriasin in patients with MM and MGUS significance, as well as in a group of healthy controls. According to our research, patients with MGUS have higher HMGHB-1 concentrations than healthy controls (846.7 ± 287.6 pg/ml vs. 176.9 ± 204.8 pg/ml for controls, p < 0.001). Similarly, we found a huge difference in HMGB-1 levels for MM patients with respect to controls (928.0 ± 551.4 pg/ml vs. 176.9 ± 204.8 pg/ml; p = 0.001). No difference was found as for the Psoriasin levels in the three groups considered. Additionally, we tried to evaluate the knowledge already present in the literature about putative mechanisms of action for these molecules in the onset and development of these disorders.

Autophagy: A Potential Therapeutic Target to Tackle Drug Resistance in Multiple Myeloma

Multiple myeloma (MM) is the second most prevalent hematologic malignancy. In the past few years, the survival of MM patients has increased due to the emergence of novel drugs and combination therapies. Nevertheless, one of the significant obstacles in treating most MM patients is drug resistance, especially for individuals who have experienced relapses or developed resistance to such cutting-edge treatments. One of the critical processes in developing drug resistance in MM is autophagic activity, an intracellular self-digestive process. Several possible strategies of autophagy involvement in the induction of MM-drug resistance have been demonstrated thus far. In multiple myeloma, it has been shown that High mobility group box protein 1 (HMGB1)-dependent autophagy can contribute to drug resistance. Moreover, activation of autophagy via proteasome suppression induces drug resistance. Additionally, the effectiveness of clarithromycin as a supplemental drug in treating MM has been reported recently, in which autophagy blockage is proposed as one of the potential action mechanisms of CAM. Thus, a promising therapeutic approach that targets autophagy to trigger the death of MM cells and improve drug susceptibility could be considered. In this review, autophagy has been addressed as a survival strategy crucial for drug resistance in MM.

The potential link between Covid-19 and multiple myeloma: A new saga

BACKGROUND

Covid-19 is considered a primary respiratory disease-causing viral pneumonia and, in severe cases, leads to acute lung injury and acute respiratory distress syndrome (ARDS). In addition, though, extra-pulmonary manifestations of Covid-19 have been shown. Furthermore, severe acute respiratory distress syndrome coronavirus type 2 (SARS-CoV-2) infection may coexist with several malignancies, including multiple myeloma (MM).

METHODS

This critical literature review aimed to find the potential association between SARS-CoV-2 infection and MM in Covid-19 patients with underlying MM. Narrative literature and databases search revealed that ARDS is developed in both MM and Covid-19 due to hypercalcemia and proteasome dysfunction.

RESULTS

Notably, the expression of angiogenic factors and glutamine deficiency could link Covid-19 severity and MM in the pathogenesis of cardiovascular complications. MM and Covid-19 share thrombosis as a typical complication; unlike thrombosis in Covid-19, which reflects disease severity, thrombosis does not reflect disease severity in MM. In both conditions, thromboprophylaxis is essential to prevent pulmonary thrombosis and other thromboembolic disorders. Moreover, Covid-19 may exacerbate the development of acute kidney injury and neurological complications in MM patients.

CONCLUSION

These findings highlighted that MM patients might be a risk group for Covid-19 severity due to underlying immunosuppression and most of those patients need specific management in the Covid-19 era.

Guggulsterone Induces Apoptosis in Multiple Myeloma Cells by Targeting High Mobility Group Box 1 via Janus Activated Kinase/Signal Transducer and Activator of Transcription Pathway

Multiple myeloma (MM) is a hematological disorder characterized by the abnormal expansion of plasma cells in the bone marrow. Despite great advances over the past three decades in discovering the efficacious therapies for MM, the disease remains incurable for most patients owing to emergence of drug-resistant cancerous cells. Guggulsterone (GS), a phytosteroid, extracted from the gum resin of guggul plant, has displayed various anticancer activities in vitro and in vivo; however, the molecular mechanisms of its anticancer activity have not been evaluated in MM cells. Therefore, in this study, we investigated the anticancer activity of GS in various MM cell lines (U266, MM.1S, and RPMI 8226) and the mechanisms involved. GS treatment of MM cells caused inhibition of cell proliferation and induction of apoptotic cell death as indicated by increased Bax protein expression, activation of caspases, and cleavage of poly (ADP-ribose) polymerase. This was associated with the downregulation of various proliferative and antiapoptotic gene products, including cyclin D, Bcl-2, Bcl-xL, and X-linked inhibitor of apoptosis protein. GS also suppressed the constitutive and interleukin 6-induced activation of STAT3. Interestingly, the inhibition of Janus activated kinase or STAT3 activity by the specific inhibitors or by siRNA knockdown of STAT3 resulted in the downregulation of HMGB1, suggesting an association between GS, STAT3, and HMGB1. Finally, GS potentiated the anticancer effects of bortezomib (BTZ) in MM cells. Herein, we demonstrated that GS could be a potential therapeutic agent for the treatment of MM, possibly alone or in combination with BTZ.

Deubiquitylase USP12 induces pro-survival autophagy and bortezomib resistance in multiple myeloma by stabilizing HMGB1

Despite the establishment of novel therapeutic interventions, multiple myeloma (MM) remains invariably incurable due to development of drug resistance and subsequent relapse, which are attributed to activation of oncogenic pathways such as autophagy. Deubiquitinating enzymes (DUBs) are promising targets to overcome resistance to proteasome inhibitor-based treatment. Ubiquitin-specific protease-12 (USP12) is a DUB with a known prognostic value in several cancers. We found that USP12 protein levels were significantly higher in myeloma patient samples than in non-cancerous human samples. Depletion of USP12 suppressed cell growth and clonogenicity and inhibited autophagy. Mechanistic studies showed that USP12 interacted with, deubiquitylated and stabilized the critical autophagy mediator HMGB1 (high mobility group box-1) protein. Knockdown of USP12 decreased the level of HMGB1 and suppressed HMGB1-mediated autophagy in MM. Furthermore, basal autophagy activity associated with USP12/HMGB1 was elevated in bortezomib (BTZ)-resistant MM cell lines. USP12 depletion, concomitant with a reduced expression of HMGB1, suppressed autophagy and increased the sensitivity of resistant cells to BTZ. Collectively, our findings have identified an important role of the deubiquitylase USP12 in pro-survival autophagy and resultant BTZ resistance in MM by stabilizing HMGB1, suggesting that the USP12/HMGB1 axis might be pursued as a potential diagnostic and therapeutic target in human MM.

PIWIL1 Drives Chemoresistance in Multiple Myeloma by Modulating Mitophagy and the Myeloma Stem Cell Population

As an important member of the Argonaute protein family, PIWI-like protein 1 (PIWIL1) plays a key role in tumor cell viability. However, the exact function of PIWIL1 in multiple myeloma (MM) and the underlying mechanism remain unclear. Here, we revealed that PIWIL1 was highly expressed in myeloma cell lines and newly diagnosed MM patients, and that its expression was notably higher in refractory/relapsed MM patients. PIWIL1 promoted the proliferation of MM cells and conferred resistance to chemotherapeutic agents both in vitro and in vivo. More importantly, PIWIL1 enhanced the formation of autophagosomes, especially mitophagosomes, by disrupting mitochondrial calcium signaling and modulating mitophagy-related canonical PINK1/Parkin pathway protein components. Mitophagy/autophagy inhibitors overcome PIWIL1-induced chemoresistance. In addition, PIWIL1 overexpression increased the proportion of side population (SP) cells and upregulated the expression of the stem cell-associated genes Nanog, OCT4, and SOX2, while its inhibition resulted in opposite effects. Taken together, our findings demonstrated that PIWIL1 induced drug resistance by activating mitophagy and regulating the MM stem cell population. PIWIL1 depletion significantly overcame drug resistance and could be used as a novel therapeutic target for reversing resistance in MM patients.

HMGB1 could restrict 1,3-β-glucan induced mice lung inflammation by affecting Beclin1 and Bcl2 interaction and promoting the autophagy of epithelial cells

Fungi were microorganisms that are ubiquitous in a variety of environments. Inhalation of fungi-contaminated organic dust led to hypersensitivity pneumonitis and might eventually cause irreversible pulmonary fibrosis. Studies showed that maintaining the homeostasis of epithelial cells was vital for defending the exogenous fungi invasion. HMGB1-dependent autophagy played a critical role in maintaining cell homeostasis in multiple inflammatory diseases. However, the actual role of HMGB1-dependent autophagy in hypersensitivity pneumonitis was unclear. In our study, mice were exposed to 0.3 mg/50 μL 1,3-β-glucan solution by intratracheal instillation to set up the lung inflammation model. To investigate the role of HMGB1-dependent autophagy in 1,3-β-glucan induced lung inflammation, AAV-sh-HMGB1 was intratracheally injected to silence HMGB1 in the lung. Our finding suggested that silencing HMGB1 could aggravate the 1,3-β-glucan induced lung inflammation by inhibiting the autophagy of epithelial cells. And ubiquitination of Beclin1 contributed to decreasing the interaction of Beclin1 and Bcl2, which might be a key regulatory mechanism of HMGB1 on 1,3-β-glucan induced autophagy.

Molecular mechanisms involved in DNA repair in human cancers: An overview of PI3k/Akt signaling and PIKKs crosstalk

The cellular genome is frequently subjected to abundant endogenous and exogenous factors that induce DNA damage. Most of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family members are activated in response to DNA damage and are the most important DNA damage response (DDR) proteins. The DDR system protects the cells against the wrecking effects of these genotoxicants and repairs the DNA damage caused by them. If the DNA damage is severe, such as when DNA is the goal of chemo-radiotherapy, the DDR drives cells toward cell cycle arrest and apoptosis. Some intracellular pathways, such as PI3K/Akt, which is overactivated in most cancers, could stimulate the DDR process and failure of chemo-radiotherapy with the increasing repair of damaged DNA. This signaling pathway induces DNA repair through the regulation of proteins that are involved in DDR like BRCA1, HMGB1, and P53. In this review, we will focus on the crosstalk of the PI3K/Akt and PIKKs involved in DDR and then discuss current achievements in the sensitization of cancer cells to chemo-radiotherapy by PI3K/Akt inhibitors.

Involvement of Alarmins in the Pathogenesis and Progression of Multiple Myeloma

OBJECTIVE

Multiple Myeloma (MM) is a haematological disease resulting from the neoplastic transformation of plasma cells. The uncontrolled growth of plasma cells in the bone marrow and the delivery of several cytokines causes bone erosion that often does not regress, even in the event of disease remission. MM is characterised by a multi-step evolutionary path, which starts with an early asymptomatic stage defined as monoclonal gammopathy of undetermined significance (MGUS) evolving to overt disease.

DATA SOURCES AND STUDY SELECTION

We have selected scientific publications on the specific topics "alarmis, MGUS, and MM", drawing from PubMed. The keywords we used were alarmines, MGUS, MM, and immune system.

RESULTS

The analysis confirms the pivotal role of molecules such as high-mobility group box-1, heat shock proteins, and S100 proteins in the induction of neoangiogenesis, which represents a milestone in the negative evolution of MM as well as other haematological and non-haematological tumours.

CONCLUSIONS

Modulation of the host immune system and the inhibition of neoangiogenesis may represent the therapeutic target for the treatment of MM that is capable of promoting better survival and reducing the risk of RRMM.

HMGB1 enhances chemotherapy resistance in multiple myeloma cells by activating the nuclear factor-κB pathway

Chemotherapy resistance is a main obstacle in the clinical chemotherapeutic treatment of multiple myeloma (MM). High-mobility group box 1 (HMGB1) has been revealed to be associated with the sensitivity of MM cells to chemotherapy, but how HMGB1 regulates chemotherapy resistance in MM has yet to be fully elucidated. In the present study, the exact molecular mechanism underlying HMGB1-mediated drug resistance in MM was explored using three chemotherapy-resistant MM cells (RPMI8226/ADR, RPMI8226/BOR and RPMI8226/DEX) that were successfully established. Reverse transcription-quantitative polymerase chain reaction revealed that the three chemotherapy-resistant MM cells exhibited a higher release of HMGB1 compared with the parental RPMI8226 cells. Interference with endogenous HMGB1 increased the sensitivity of drug-resistant MM cells to chemotherapy, which was supported by the low IC₅₀ value and the enlargement of cell apoptosis. Furthermore, short hairpin (sh)RNA-transfected MM cells showed an obvious elevation in phosphorylated (p)-IKKα/β, p-IκBα and p-p65 in whole cell lysate and/or nucleus, and treatment of nuclear factor (NF)-κB activator reversed the effect of shHMGB1-mediated cell viability and apoptosis in MM cells. In conclusion, HMGB1 regulates drug resistance in MM cells by regulating NF-κB signaling pathway, suggesting that HMGB1 has the potential to serve as a target for MM treatment.

Astragaloside IV and Saponins of Rhizoma Polygonati Cure Cyclophosphamide-Induced Myelosuppression in Lung Adenocarcinoma via Down-Regulating miR-142-3p

Our previous study revealed that Shuanghuang Shengbai granule could cure the myelosuppression induced by cyclophosphamide (CTX) in lung cancer. However, its hematopoietic effects and molecular mechanisms remain not fully understood. Therefore, this study was intended to investigate the effects and the underlying mechanisms of Astragaloside IV (AS) and saponins of rhizoma polygonati (SRP), the two main bioactive ingredients of Shuanghuang Shengbai granule, on CTX-induced myelosuppression. CTX inhibited the proliferation and promoted apoptosis in bone marrow hematopoietic stem cells (BMHSCs), accompanied by the increased expression of miR-142-3p. AS and/or SRP treatment could alleviate CTX-induced cell injury and suppress the expression of miR-142-3p. Over-expression of miR-142-3p partially reversed the therapeutic effect of AS and/or SRP on CTX-induced cell injury in BMHSCs. Further mechanism exploration discovered that HMGB1 was the target gene of miR-142-3p, and miR-142-3p negatively regulated the expression of HMGB1. To further explore the function of AS and/or SRP in vivo, we constructed a lung cancer xenograft combined with CTX-induced myelosuppression mouse model, and we found that AS and SRP remarkably reversed the CTX-induced reduction of white blood cells, bone marrow nucleated cells, and thymus index in vivo and did not affect the chemotherapy effect of lung cancer. Collectively, our results strongly suggested that AS and SRP could improve the hematopoietic function of myelosuppressed lung cancer mice, and their effects may be related to the inhibition of miR-142-3p expression in BMHSCs.

A Small Molecule Stabilizer of the MYC G4-Quadruplex Induces Endoplasmic Reticulum Stress, Senescence and Pyroptosis in Multiple Myeloma

Simple Summary

The DNA G-quadruplex (G4) present in the promoter of the MYC oncogene, commonly amplified in cancers, including multiple myeloma, represents a potential anti-cancer target. A previously identified MYC G4-stablizer, which demonstrated cytotoxicity and senescence in myeloma cells, was discovered to induce endoplasmic reticulum stress and non-apoptotic cell death, pyroptosis. Cancers including myeloma escape apoptosis through upregulation of anti-apoptotic proteins and drug resistance; therefore, induction of pyroptosis provides an alternate therapeutic option. Thus, our study provides a disease-specific experimental strategy for identifying new investigational drugs in cancer treatment.

Abstract

New approaches to target MYC include the stabilization of a guanine-rich, G-quadruplex (G4) tertiary DNA structure in the NHE III region of its promoter. Recent screening of a small molecule microarray platform identified a benzofuran, D089, that can stabilize the MYC G4 and inhibit its transcription. D089 induced both dose- and time-dependent multiple myeloma cell death mediated by endoplasmic reticulum induced stress. Unexpectedly, we uncovered two mechanisms of cell death: cellular senescence, as evidenced by increased levels of p16, p21 and γ-H2AX proteins and a caspase 3-independent mechanism consistent with pyroptosis. Cells treated with D089 exhibited high levels of the cleaved form of initiator caspase 8; but failed to show cleavage of executioner caspase 3, a classical apoptotic marker. Cotreatment with the a pan-caspase inhibitor Q-VD-OPh did not affect the cytotoxic effect of D089. In contrast, cleaved caspase 1, an inflammatory caspase downstream of caspases 8/9, was increased by D089 treatment. Cells treated with D089 in addition to either a caspase 1 inhibitor or siRNA-caspase 1 showed increased IC₅₀ values, indicating a contribution of cleaved caspase 1 to cell death. Downstream effects of caspase 1 activation after drug treatment included increases in IL1B, gasdermin D cleavage, and HMGB1 translocation from the nucleus to the cytoplasm. Drug treated cells underwent a ‘ballooning’ morphology characteristic of pyroptosis, rather than ‘blebbing’ typically associated with apoptosis. ASC specks colocalized with NLRP3 in proximity ligation assays after drug treatment, indicating inflammasome activation and further confirming pyroptosis as a contributor to cell death. Thus, the small molecule MYC G4 stabilizer, D089, provides a new tool compound for studying pyroptosis. These studies suggest that inducing both tumor senescence and pyroptosis may have therapeutic potential for cancer treatment.

High mobility group box 1 (HMGB1): a pivotal regulator of hematopoietic malignancies

High mobility group box 1 (HMGB1) is a nonhistone chromatin-associated protein that has been widely reported to play a pivotal role in the pathogenesis of hematopoietic malignancies. As a representative damage-associated molecular pattern (DAMP), HMGB1 normally exists inside cells but can be secreted into the extracellular environment through passive or active release. Extracellular HMGB1 binds with several different receptors and interactors to mediate the proliferation, differentiation, mobilization, and senescence of hematopoietic stem cells (HSCs). HMGB1 is also involved in the formation of the inflammatory bone marrow (BM) microenvironment by activating proinflammatory signaling pathways. Moreover, HMGB1-dependent autophagy induces chemotherapy resistance in leukemia and multiple myeloma. In this review, we systematically summarize the emerging roles of HMGB1 in carcinogenesis, progression, prognosis, and potential clinical applications in different hematopoietic malignancies. In summary, targeting the regulation of HMGB1 activity in HSCs and the BM microenvironment is highly beneficial in the diagnosis and treatment of various hematopoietic malignancies.

Roles of HMGB1 in regulating myeloid-derived suppressor cells in the tumor microenvironment

Myeloid-derived suppressor cells (MDSCs) are notable contributors to the immunosuppressive tumor microenvironment (TME) and are closely associated with tumor progression; in addition, MDSCs are present in most patients with cancer. However, the molecular mechanisms that regulate MDSCs in the etiopathogenesis of human tumor immunity remain unclear. The secreted alarmin high mobility group box 1 (HMGB1) is a proinflammatory factor and inducer of many inflammatory molecules during MDSC development. In this review, we detail the currently reported characteristics of MDSCs in tumor immune escape and the regulatory role of secreted HMGB1 in MDSC differentiation, proliferation, activity and survival. Notably, different posttranslational modifications of HMGB1 may have various effects on MDSCs, and these effects need further identification. Moreover, exosome-derived HMGB1 is speculated to exert a regulatory effect on MDSCs, but no report has confirmed this hypothesis. Therefore, the effects of HMGB1 on MDSCs need more research attention, and additional investigations should be conducted.

High mobility group box-1 protects against Aflatoxin G1-induced pulmonary epithelial cell damage in the lung inflammatory environment

Aflatoxin G₁ (AFG₁) is a member of the carcinogenic aflatoxin family. Our previous studies indicated that oral administration of AFG₁ caused tumor necrosis factor (TNF)-α-dependent inflammation that enhanced oxidative DNA damage in alveolar epithelial cells, which may be related to AFG₁-induced lung carcinogenesis. High mobility group box-1 (HMGB1) is a nuclear DNA-binding protein; the intracellular and extracellular roles of HMGB1 have been shown to contribute to DNA repair and sterile inflammation. The role of HMGB1 in DNA damage in an aflatoxin-induced lung inflammatory environment was investigated in this study. Upregulation of HMGB1, TLR2, and RAGE was observed in AFG₁-induced lung inflamed tissues and adenocarcinoma. Blocking AFG₁-induced inflammation by neutralization of TNF-α inhibited the upregulation of HMGB1 in mouse lung tissues, suggesting that AFG₁-induced TNF-α-dependent inflammation regulated HMGB1 expression. In the in vitro human pulmonary epithelial cell line model, Beas-2b, AFG₁ directly enhanced the cytosolic translocation of HMGB1 and its extracellular secretion. The addition of extracellular soluble HMGB1 protected AFG₁-induced DNA damage through the TLR2/NF-κB pathway in Beas-2b cells. In addition, blockade of endogenous HMGB1 by siRNA significantly enhanced AFG₁-induced damage. Thus, our findings showed that both extracellularly-released and nuclear and cytosolic HMGB1 could protect the cell from AFG₁-induced cell damage in a TNF-α-dependent lung inflammatory environment.

Upregulation of miR-129-5p increases the sensitivity to Taxol through inhibiting HMGB1-mediated cell autophagy in breast cancer MCF-7 cells

Although Taxol has improved the survival of cancer patients as a first-line chemotherapeutic agent, an increasing number of patients develop resistance to Taxol after prolonged treatment. The potential mechanisms of cancer cell resistance to Taxol are not completely clear. It has been reported that microRNAs (miRNAs) are involved in regulating the sensitivity of cancer cells to various chemotherapeutic agents. In this study, we aimed to explore the role of miR-129-5p in regulating the sensitivity of breast cancer cells to Taxol. Cell apoptosis and autophagy, and the sensitivity of MCF-7 cells to Taxol were assessed with a series of in vitro assays. Our results showed that the inhibition of autophagy increased the Taxol-induced apoptosis and the sensitivity of MCF-7 cells to Taxol. Up-regulation of miR-129-5p also inhibited autophagy and induced apoptosis. Furthermore, miR-129-5p overexpression increased the sensitivity of MCF-7 cells to Taxol. High mobility group box 1 (HMGB1), a target gene of miR-129-5p and a regulator of autophagy, was negatively regulated by miR-129-5p. We found that interference of HMGB1 enhanced the chemosensitivity of Taxol by inhibiting autophagy and inducing apoptosis in MCF-7 cells. Taken together, our findings suggested that miR-129-5p increased the chemosensitivity of MCF-7 cells to Taxol through suppressing autophagy and enhancing apoptosis by inhibiting HMGB1. Using miR-129-5p/HMGB1/autophagy-based therapeutic strategies may be a potential treatment for overcoming Taxol resistance in breast cancer.

The Use of Murine Models for Studying Mechanistic Insights of Genomic Instability in Multiple Myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the accumulation of clonal plasma cells in the bone marrow. In normal plasma cell development, cells undergo programmed DNA breaks and translocations, a process necessary for generation of a wide repertoire of antigen-specific antibodies. This process also makes them vulnerable for the acquisition of chromosomal defects. Well-known examples of these aberrations, already seen at time of MM diagnosis, are hyperdiploidy or the translocations involving the immunoglobulin heavy chain. Over the recent years, however, novel aspects concerning genomic instability and its role in tumor development, disease progression and nascence of refractory disease were identified. As such, genomic instability is becoming a very relevant research topic with the potential identification of novel disease pathways. In this review, we aim to describe recent studies involving murine MM models focusing on the deregulation of processes implicated in genomic instability and their clinical impact. More specifically, we will discuss chromosomal instability, DNA damage and repair responses, development of drug resistance, and recent insights into the study of clonal hierarchy using different murine MM models. Lastly, we will discuss the importance and the use of murine MM models in the pre-clinical evaluation of promising novel therapeutic agents.

Alarmin HMGB1 and Soluble RAGE as New Tools to Evaluate the Risk Stratification in Patients With the Antiphospholipid Syndrome

Antiphospholipid antibody syndrome (APS) is a systemic autoimmune disease characterized by arterial and/or venous thrombosis, pregnancy morbidity in the presence of circulating “anti-phospholipid antibodies” (aPL). One of the main target antigens of aPL is β₂-glycoprotein I (β₂-GPI). APS may occur as a primary syndrome or associated with Systemic Lupus Erythematosus (SLE). High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein which is secreted from different type of cells during activation and/or cell death and may act as a proinflammatory mediator through ligation to its receptors, including RAGE. There is accumulating evidence that HMGB1 contributes to the pathogenesis of inflammatory and autoimmune diseases, especially SLE. In a previous study we demonstrated increased serum levels of HMGB1 in both primary and secondary APS patients. In this work we analyzed: (i) in vitro whether anti-β₂-GPI antibodies from APS patients may induce both a HMGB1 cellular relocation by activation of its putative receptor RAGE in platelets and monocytes and, (ii) ex vivo, serum levels of HMGB1/soluble RAGE (sRAGE) in APS patients and their possible correlation with clinical manifestations. Platelets and monocytes from healthy donors were incubated with affinity purified anti-β₂-GPI antibodies. HMGB1 and RAGE expression were analyzed by Western Blot. Sera from 60 consecutive APS patients (primary or secondary), diagnosed according to the Sydney Classification Criteria, were enrolled. As a control, 30 matched healthy subjects were studied. Serum levels of HMGB1 and sRAGE were analyzed by Western Blot. In vitro results showed that anti-β₂-GPI antibodies were able to induce RAGE activation and HMGB1 cellular relocation in both monocytes and platelets. HMGB1 and sRAGE serum levels were significantly increased in APS patients in comparison with healthy subjects (p<0.0001). Interestingly, APS patients with spontaneous recurrent abortion showed significantly higher levels of sRAGE; moreover, in APS patients a direct correlation between serum levels of HMGB1 and disease duration was detected. Our observations suggest that anti-β₂-GPI antibodies may trigger RAGE activation and HMGB1 cellular relocation during APS. Monitoring these molecules serum levels may represent an useful tool to evaluate the pathogenesis and risk stratification of clinical manifestations in APS.

Therapeutic Modulation of Autophagy in Leukaemia and Lymphoma

Haematopoiesis is a tightly orchestrated process where a pool of hematopoietic stem and progenitor cells (HSPCs) with high self-renewal potential can give rise to both lymphoid and myeloid lineages. The HSPCs pool is reduced with ageing resulting in few HSPC clones maintaining haematopoiesis thereby reducing blood cell diversity, a phenomenon called clonal haematopoiesis. Clonal expansion of HSPCs carrying specific genetic mutations leads to increased risk for haematological malignancies. Therefore, it comes as no surprise that hematopoietic tumours develop in higher frequency in elderly people. Unfortunately, elderly patients with leukaemia or lymphoma still have an unsatisfactory prognosis compared to younger ones highlighting the need to develop more efficient therapies for this group of patients. Growing evidence indicates that macroautophagy (hereafter referred to as autophagy) is essential for health and longevity. This review is focusing on the role of autophagy in normal haematopoiesis as well as in leukaemia and lymphoma development. Attenuated autophagy may support early hematopoietic neoplasia whereas activation of autophagy in later stages of tumour development and in response to a variety of therapies rather triggers a pro-tumoral response. Novel insights into the role of autophagy in haematopoiesis will be discussed in light of designing new autophagy modulating therapies in hematopoietic cancers.