The Role of HMGB1 in Radioresistance of Bladder Cancer

DNA repair in tumor radioresistance: insights from fruit flies genetics

BACKGROUND

Radiation therapy (RT) is a key anti-cancer treatment that involves using ionizing radiation to kill tumor cells. However, this therapy can lead to short- and long-term adverse effects due to radiation exposure of surrounding normal tissue. The type of DNA damage inflicted by radiation therapy determines its effectiveness. High levels of genotoxic damage can lead to cell cycle arrest, senescence, and cell death, but many tumors can cope with this damage by activating protective mechanisms. Intrinsic and acquired radioresistance are major causes of tumor recurrence, and understanding these mechanisms is crucial for cancer therapy. The mechanisms behind radioresistance involve processes like hypoxia response, cell proliferation, DNA repair, apoptosis inhibition, and autophagy.

CONCLUSION

Here we briefly review the role of genetic and epigenetic factors involved in the modulation of DNA repair and DNA damage response that promote radioresistance. In addition, leveraging our recent results on the effects of low dose rate (LDR) of ionizing radiation on Drosophila melanogaster we discuss how this model organism can be instrumental in the identification of conserved factors involved in the tumor resistance to RT.

IGF2BP3 prevent HMGB1 mRNA decay in bladder cancer and development

BACKGROUND

IGF2BP3 functions as an RNA-binding protein (RBP) and plays a role in the posttranscriptional control of mRNA localization, stability, and translation. Its dysregulation is frequently associated with tumorigenesis across various cancer types. Nonetheless, our understanding of how the expression of the IGF2BP3 gene is regulated remains limited. The specific functions and underlying mechanisms of IGF2BP3, as well as the potential benefits of targeting it for therapeutic purposes in bladder cancer, are not yet well comprehended.

METHODS

The mRNA and protein expression were examined by RT-qPCR and western blotting, respectively. The methylation level of CpG sites was detected by Bisulfite sequencing PCR (BSP). The regulation of IGF2BP3 expression by miR-320a-3p was analyzed by luciferase reporter assay. The functional role of IGF2BP3 was determined through proliferation, colony formation, wound healing, invasion assays, and xenograft mouse model. The regulation of HMGB1 by IGF2BP3 was investigated by RNA immunoprecipitation (RIP) and mRNA stability assays.

RESULTS

We observed a significant elevation in IGF2BP3 levels within bladder cancer samples, correlating with more advanced stages and grades, as well as an unfavorable prognosis. Subsequent investigations revealed that the upregulation of IGF2BP3 expression is triggered by copy number gain/amplification and promoter hypomethylation in various tumor types, including bladder cancer. Furthermore, miR-320a-3p was identified as another negative regulator in bladder cancer. Functionally, the upregulation of IGF2BP3 expression exacerbated bladder cancer progression, including the proliferation, migration, and invasion of bladder cancer. Conversely, IGF2BP3 silencing produced the opposite effects. Moreover, IGF2BP3 expression positively correlated with inflammation and immune infiltration in bladder cancer. Mechanistically, IGF2BP3 enhanced mRNA stability and promoted the expression of HMGB1 by binding to its mRNA, which is a factor that promotes inflammation and orchestrates tumorigenesis in many cancers. Importantly, pharmacological inhibition of HMGB1 with glycyrrhizin, a specific HMGB1 inhibitor, effectively reversed the cancer-promoting effects of IGF2BP3 overexpression in bladder cancer. Furthermore, the relationship between HMGB1 mRNA and IGF2PB3 is also observed in mammalian embryonic development, with the expression of both genes gradually decreasing as embryonic development progresses.

CONCLUSIONS

Our present study sheds light on the genetic and epigenetic mechanisms governing IGF2BP3 expression, underscoring the critical involvement of the IGF2BP3-HMGB1 axis in driving bladder cancer progression. Additionally, it advocates for the investigation of inhibiting IGF2BP3-HMGB1 as a viable therapeutic approach for treating bladder cancer.

Role of HMGB1 and its associated signaling pathways in human malignancies

The High-Mobility Group Box-1 (HMGB1), a non-histone chromatin-associated protein, plays a crucial role in cancer growth and response to therapy as it retains a pivotal role in promoting both cell death and survival. HMGB1 has been reported to regulate several signaling pathways engaged in inflammation, genome stability, immune function, cell proliferation, cell autophagy, metabolism, and apoptosis. However, the association between HMGB1 and cancer is complex and its mechanism in tumorigenesis needs to be further elucidated. This review aims to understand the role of HMGB1 in human malignancies and discuss the signaling pathways linked to this process to provide a comprehensive understanding on the association of HMGB1 with carcinogenesis. Further, we will review the role of HMGB1 as a target/biomarker for cancer therapy, the therapeutic strategies used to target this protein, and its potential role in preventing or treating cancers. In light of the recent growing evidence linking HMGB1 to cancer progression, we think that it may be suggested as a novel and emergent therapeutic target for cancer therapy. Hence, HMGB1 warrants paramount investigation to comprehensively map its role in tumorigenesis.

Pharmacotherapy developments in autophagy inhibitors for bladder cancer

INTRODUCTION

Autophagy is an intracellular process that plays a key role in the cellular homeostasis. Recently, it has been described as a potential therapeutic target in oncology, whether by activating or inhibiting its different cascades. Autophagy inhibitors interact with different molecular processes of the hallmarks of cancer.

AREAS COVERED

Multiple proteins of the autophagy cascade could be aimed by specific inhibitors in many tumors, notably bladder cancer. In fact, bladder cancer has been increasing in prevalence over the last decade, and resistance to conventional treatment has been extensively reported in the literature. Autophagy inhibitors in bladder cancer have been described in preclinical studies to increase the sensitivity of the tumor to chemotherapy and radiotherapy. This paper is a review of the literature, which selected randomized trials, cohort studies, and case-control studies documenting the relationship between autophagy inhibitors and bladder cancer treatment.

EXPERT OPINION

Autophagy is a promising pathway for cancer cell targeting that opens the horizons for a potential new therapeutic area in particular the multidisciplinary management of bladder cancer.

Dialog beyond the Grave: Necrosis in the Tumor Microenvironment and Its Contribution to Tumor Growth

Damage-associated molecular patterns (DAMPs) are endogenous molecules released from the necrotic cells dying after exposure to various stressors. After binding to their receptors, they can stimulate various signaling pathways in target cells. DAMPs are especially abundant in the microenvironment of malignant tumors and are suspected to influence the behavior of malignant and stromal cells in multiple ways often resulting in promotion of cell proliferation, migration, invasion, and metastasis, as well as increased immune evasion. This review will start with a reminder of the main features of cell necrosis, which will be compared to other forms of cell death. Then we will summarize the various methods used to assess tumor necrosis in clinical practice including medical imaging, histopathological examination, and/or biological assays. We will also consider the importance of necrosis as a prognostic factor. Then the focus will be on the DAMPs and their role in the tumor microenvironment (TME). We will address not only their interactions with the malignant cells, frequently leading to cancer progression, but also with the immune cells and their contribution to immunosuppression. Finally, we will emphasize the role of DAMPs released by necrotic cells in the activation of Toll-like receptors (TLRs) and the possible contributions of TLRs to tumor development. This last point is very important for the future of cancer therapeutics since there are attempts to use TLR artificial ligands for cancer therapeutics.

Radiotherapy, PARP Inhibition, and Immune-Checkpoint Blockade: A Triad to Overcome the Double-Edged Effects of Each Single Player

Radiotherapy and, more recently, PARP inhibitors (PARPis) and immune-checkpoint inhibitors represent effective tools in cancer therapy. Radiotherapy exerts its effects not only by damaging DNA and inducing tumor cell death, but also stimulating anti-tumor immune responses. PARPis are known to exert their therapeutic effects by inhibiting DNA repair, and they may be used in combination with radiotherapy. Both radiotherapy and PARPis modulate inflammatory signals and stimulate type I IFN (IFN-I)-dependent immune activation. However, they can also support the development of an immunosuppressive tumor environment and upregulate PD-L1 expression on tumor cells. When provided as monotherapy, immune-checkpoint inhibitors (mainly antibodies to CTLA-4 and the PD-1/PD-L1 axis) result particularly effective only in immunogenic tumors. Combinations of immunotherapy with therapies that favor priming of the immune response to tumor-associated antigens are, therefore, suitable strategies. The widely explored association of radiotherapy and immunotherapy has confirmed this benefit for several cancers. Association with PARPis has also been investigated in clinical trials. Immunotherapy counteracts the immunosuppressive effects of radiotherapy and/or PARPis and synergies with their immunological effects, promoting and unleashing immune responses toward primary and metastatic lesions (abscopal effect). Here, we discuss the beneficial and counterproductive effects of each therapy and how they can synergize to overcome single-therapy limitations.

Downregulation of CEMIP enhances radiosensitivity by promoting DNA damage and apoptosis in colorectal cancer

Colorectal cancer (CRC) is the third leading malignancy worldwide in both new cases and deaths. Neoadjuvant radiotherapy is the standard preoperative regimens for locally advanced patients. However, approximately 50% of patients develop recurrence and metastasis after radiotherapy, which is largely due to the radiation resistance properties of the tumor, and the internal mechanism has not been elucidated. Here we found that CEMIP expression is up-regulated in a variety of tumor types, particularly in CRC. Public databases and clinical samples revealed that CEMIP expression is significantly higher in tumor tissues than in adjacent normal tissues in patients with locally advanced CRC who received neoadjuvant chemoradiotherapy, and it is closely related to the poor prognosis. Functional characterization uncovered that downregulation of CEMIP expression can enhance the radiosensitivity of CRC cells, which is confirmed to be achieved by promoting DNA damage and apoptosis. In vivo studies further verified that CEMIP knockdown can significantly improve the radiosensitivity of subcutaneously implanted colorectal tumors in mice, suggesting that CEMIP may be a radiation-resistant gene in CRC. Mechanistically, EGFR/PI3K/Akt signaling pathway is hypothesized to play a key role in CEMIP mediating radiation resistance. These results provide a potential new strategy targeting CEMIP gene for the comprehensive treatment of locally advanced CRC patients.

The Role of PARP1 and PAR in ATP-Independent Nucleosome Reorganisation during the DNA Damage Response

The functioning of the eukaryotic cell genome is mediated by sophisticated protein-nucleic-acid complexes, whose minimal structural unit is the nucleosome. After the damage to genomic DNA, repair proteins need to gain access directly to the lesion; therefore, the initiation of the DNA damage response inevitably leads to local chromatin reorganisation. This review focuses on the possible involvement of PARP1, as well as proteins acting nucleosome compaction, linker histone H1 and non-histone chromatin protein HMGB1. The polymer of ADP-ribose is considered the main regulator during the development of the DNA damage response and in the course of assembly of the correct repair complex.

Curcumin in the treatment of urological cancers: Therapeutic targets, challenges and prospects

Urological cancers include bladder, prostate and renal cancers that can cause death in males and females. Patients with urological cancers are mainly diagnosed at an advanced disease stage when they also develop resistance to therapy or poor response. The use of natural products in the treatment of urological cancers has shown a significant increase. Curcumin has been widely used in cancer treatment due to its ability to trigger cell death and suppress metastasis. The beneficial effects of curcumin in the treatment of urological cancers is the focus of current review. Curcumin can induce apoptosis in the three types of urological cancers limiting their proliferative potential. Furthermore, curcumin can suppress invasion of urological cancers through EMT inhibition. Notably, curcumin decreases the expression of MMPs, therefore interfering with urological cancer metastasis. When used in combination with chemotherapy agents, curcumin displays synergistic effects in suppressing cancer progression. It can also be used as a chemosensitizer. Based on pre-clinical studies, curcumin administration is beneficial in the treatment of urological cancers and future clinical applications might be considered upon solving problems related to the poor bioavailability of the compound. To improve the bioavailability of curcumin and increase its therapeutic index in urological cancer suppression, nanostructures have been developed to favor targeted delivery.

Factors and molecular mechanisms of radiation resistance in cancer cells

PURPOSE

The aim of this work is to review the published studies on radiation resistance mechanisms and molecular markers involved in different tumors. The revision has been focused in the last 5 years (2016-2021).

CONCLUSIONS

Radioresistance is a cause of concern as it causes failure of radiation therapy and subsequent tumor relapse. Combination chemotherapy and radiation therapy are clinically successful in treating many types of tumors. Despite continued improvements in cancer treatment, locoregional recurrence or metastatic spread continues to occur in a high proportion of patients after being treated with radiation therapy or combination treatments. There is strong evidence that cancer stem cells contribute to radiation resistance, contributing to treatment failure. The mechanisms of radiation resistance in different tumors are not fully understood. A better understanding of cancer stem cells and the associated signaling pathways that regulate radiation resistance will open up new strategies for treating cancer by radiation therapy. Radiation can damage malignant cells mainly by the induction of DNA double strand breaks. However, in some tumors appear resistant cells that repopulate the tumor following therapy leading over time to the failure of the treatment. Native mechanisms and induced pathways, are the cause of radiation resistance. It has been described that numerous molecular markers acting through numerous mechanisms of action involved in radiation resistance, such as apoptosis resistance, alterations of cell growth, proliferation and DNA repair, hypoxia, increase in invasiveness and migration capacity, cell cycle alterations and expression of heat shock proteins, among others. Therefore, resistance to radiation is a multifactorial phenomenon that, in different cell types, it occurs through different regulatory mechanisms in which different molecules intervene. Resistance can be acquired by altering different regulatory pathways in different tumors. The knowledge of radiation resistance markers could help in the classification and treatment of patients with more aggressive tumors.

HMGB1 induces radioresistance through PI3K/AKT/ATM pathway in esophageal squamous cell carcinoma

BACKGROUND

To explore the effect of HMGB1 on the radio-sensitivity of esophageal cancer cells through regulating the PI3K/Akt/ATM pathway.

METHODS AND RESULTS

We observed the expression of HMGB1 and p-ATM in biopsies of esophageal cancer patients with immunohistochemical staining. Western blot and RT-qPCR were applied to detect the protein and RNA related to PI3K/Akt/ATM pathway, respectively. In addition, we inhibited the PI3K/Akt pathway with ly294002 and activated it with IGF1, then we explored the invasion, proliferation ability, and apoptosis of esophageal cancer cells in vitro by transwell, CCK8 assay, and flow cytometry respectively. In vivo, xenograft tumor model was established in nude mice to study the effect of HMGB1 on radioresistance via PI3K/AKT/ATM Signaling Pathway. The survival rate in patients with single positive/double negative expression of HMGB1 and p-ATM was significantly higher than in those with both positive expression of HMGB1 and p-ATM, the depletion of HMGB1 combined with ly294002 significantly inhibited cell proliferation and invasion ability, meanwhile, the addition of IGF1 reversed it. Meanwhile, depletion of HMGB1 and ly294002 promoted apoptosis and arrested the cancer cells in G0/G1 cell cycle with the decreased expression of Cyclin D1 and CDK4 and improved P16. We further validated these results in vivo, the application of HMGB1 silencing promoted apoptosis of xenograft tumors after radiation, especially combined with pathway inhibitor ly294002.

CONCLUSIONS

Esophageal cancer patients with high expression of HMGB1 and p-ATM have a poor prognosis after chemo-radiotherapy. Down-regulation of HMGB1 may promote the radio-sensitivity of esophageal cancer cells through regulating PI3K/Akt/ATM pathway.

Emerging roles of autophagy in the development and treatment of urothelial carcinoma of the bladder

INTRODUCTION

High recurrence rates, frequent surveillance strategies, and current multidisciplinary treatment approaches make urothelial carcinoma of bladder (UCB) one of the most expensive cancers to clinically manage. Recent studies have demonstrated a role for autophagy in bladder tumorigenesis. It serves as a tumor suppressor by maintaining genomic integrity and preventing tumor proliferation during initial stages of tumor development. Nevertheless, once established, cancer cells may utilize protective autophagy to endure cellular stress and survive in the adverse environment. Its excessive stimulation supports cancer cells' resistance to therapeutic modalities.

AREAS COVERED

PubMed and Google Scholar electronic databases were searched for recently published studies. This review summarizes emerging roles of autophagy in development/progression of UCB and treatment resistance and explores novel therapeutic targets for prevention of cancer invasion, metastatic spread', and disease relapse.

EXPERT OPINION

The development of novel therapies via targeting of autophagy may augment current treatment regimens and improve clinical outcomes. Synthetic compounds or plant-based metabolites are reported to enhance cancer therapies by modulating autophagic flux. Successful autophagy-focused therapeutic intervention requires a mechanistic understanding of autophagic effects on tumor initiation and progression and the development of efficient biomarkers to monitor it in tumor tissues.

CD68+ Macrophage Infiltration Associates With Poor Outcome of HPV Negative Oral Squamous Carcinoma Patients Receiving Radiation: Poly(I:C) Enhances Radiosensitivity of CAL-27 Cells but Promotes Macrophage Recruitment Through HMGB1

Patients with human papillomavirus (HPV) negative oral squamous cell carcinoma (OSCC) generally have poor clinical outcomes and worse responses to radiotherapy. It is urgent to explore the underlining mechanisms of the distinct prognoses between HPV negative and HPV positive OSCC and to develop effective therapy strategy to increase the survival rate of HPV negative OSCC patients. We conducted a retrospective cohort of 99 resected OSCC patients to evaluate the prognosis of HPV negative and HPV positive OSCC patients receiving radiation or not. We further addressed the association of CD68⁺ macrophage infiltration with HPV status and the effects on survival of OSCC patients. We also used the TCGA-OSCC cohort for further verification. Based on the cohort study, we applied a synthetic dsRNA polymer, polyriboinosinic-polyribocytidylic acid (poly(I:C)), on CAL-27 (HPV negative OSCC cells). We co-cultured its condition medium with THP-1 derived macrophage and examined the cytokines and macrophage migration. We found that high CD68⁺ macrophage infiltration associated with poor overall survival in HPV negative OSCC patients receiving radiation. In vitro, poly(I:C) could induce apoptosis and enhance the radiosensitivity, but increase macrophage recruitment. Targeting HMGB1 could inhibit IL-6 induction and macrophage recruitment. Our findings indicated that CD68⁺ macrophage might play an important role in the outcomes of HPV negative OSCC patients receiving radiation. Our findings also suggested that radiation combined poly(I:C) might be a potential therapy strategy to increase the radiation response and prognosis of HPV negative OSCC. Notably, HMGB1 should be targeted to inhibit macrophage recruitment and enhance overall therapy effects.

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.

Value of HMGB1 expression for assessing gastric cancer severity: a systematic meta-analysis

OBJECTIVE

To evaluate the clinical value of high mobility group box-1 (HMGB1) expression levels in patients with gastric cancer.

METHODS

Articles published from January 2000 to August 2022 were searched using PubMed, Google Scholar and Science Direct, Springer, Wiley and NIH to evaluate the clinicopathological significance of HMGB1 expression in gastric cancer.

RESULTS

A total of 156 publications were selected, of which six studies, comprising 846 patients, met the criteria for inclusion in this study. Forest plots of clinicopathological characteristics indicated that HMGB1 expression was not associated with age (odds ratio (OR) = 1.07, 95% confidence interval (CI): 0.89-1.28), sex (OR = 0.90, 95% CI: 0.81-1.00), TNM (OR = 1.39, 95% CI: 0.82-2.37), N stage (OR = 1.42, 95% CI: 0.97-2.07), or tumor differentiation (OR = 0.96, 95% CI: 0.71-1.29), but was highly correlated with pT stage (OR = 1.56, 95% CI: 1.17-2.07). Funnel plots showed no significant publication bias in the included studies in terms of age, sex, TNM, pT stage, N stage, or tumor differentiation.

CONCLUSION

HMGB1 expression was significantly correlated with tumor pT stage, but not with age, sex, TNM stage, tumor N stage, tumor differentiation, or lymphatic metastasis in patients with GC.

Role of neutrophil extracellular traps in radiation resistance of invasive bladder cancer

Radiation therapy (RT) is used in the management of several cancers; however, tumor radioresistance remains a challenge. Polymorphonuclear neutrophils (PMNs) are recruited to the tumor immune microenvironment (TIME) post-RT and can facilitate tumor progression by forming neutrophil extracellular traps (NETs). Here, we demonstrate a role for NETs as players in tumor radioresistance. Using a syngeneic bladder cancer model, increased NET deposition is observed in the TIME of mice treated with RT and inhibition of NETs improves overall radiation response. In vitro, the protein HMGB1 promotes NET formation through a TLR4-dependent manner and in vivo, inhibition of both HMGB1 and NETs significantly delays tumor growth. Finally, NETs are observed in bladder tumors of patients who did not respond to RT and had persistent disease post-RT, wherein a high tumoral PMN-to-CD8 ratio is associated with worse overall survival. Together, these findings identify NETs as a potential therapeutic target to increase radiation efficacy.

Radioresistance remains a challenge in the treatment of bladder cancer. In this study, the authors show in mice that radiation increases deposits of neutrophil extracellular traps (NETs) via a TLR4-dependent mechanism and that NETs-targeting strategies can improve the response to radiotherapy.

Downregulation of high mobility group box 1 enhances the radiosensitivity of non-small cell lung cancer by acting as a crucial target of microRNA-107

High mobility group box 1 (HMGB1) has been reported to regulate the sensitivity of several types of cancer cell to chemoradiotherapy. The present study aimed to investigate the changes in HMGB1 expression after radiotherapy, as well as its regulatory role in the radiosensitivity of non-small cell lung cancer (NSCLC) cells. The expression levels of HMGB1 in the serum of 73 patients with NSCLC were analyzed by ELISA. HMGB1 mRNA and microRNA (miR)-107 expression in NSCLC cells were assessed using reverse transcription-quantitative PCR. Receiver operating characteristic analysis was used to evaluate the diagnostic value of HMGB1. Cell counting kit-8, Transwell invasion and clonogenic assays were used to determine cellular viability, invasiveness and colony formation ability, respectively. Following radiotherapy, the levels of HMGB1 were significantly decreased in the serum of patients with NSCLC, and lower serum levels had relatively high diagnostic accuracy in radiosensitive patients. Furthermore, HMGB1-knockdown retarded cellular proliferation and invasion with or without irradiation, and enhanced NSCLC cell radiosensitivity. Furthermore, knocking down miR-107 reversed the decreases in cellular proliferation and invasiveness both with and without irradiation, and reduced the survival fractions induced by sh-HMGB1. HMGB1-knockdown leads to radiosensitivity that may result from suppression of the Toll-like receptor 4 (TLR4)/NF-κB signaling pathway. Collectively, decreased expression of HMGB1 was found to be a putative diagnostic predictor of radiosensitivity in patients with NSCLC. HMGB1-knockdown inhibited the proliferation and enhanced the radiosensitivity of NSCLC cells, which may be regulated via miR-107 by mediating the TLR4/NF-κB signaling pathway. Thus, HMGB1 may be a potential regulator of radioresistance in NSCLC, and the HMGB1/miR-107 axis may represent a promising therapeutic target.

Review of Experimental Studies to Improve Radiotherapy Response in Bladder Cancer: Comments and Perspectives

Bladder cancer is among the top ten most common cancer types in the world. Around 25% of all cases are muscle-invasive bladder cancer, for which the gold standard treatment in the absence of metastasis is the cystectomy. In recent years, trimodality treatment associating maximal transurethral resection and radiotherapy combined with concurrent chemotherapy is increasingly used as an organ-preserving alternative. However, the use of this treatment is still limited by the lack of biomarkers predicting tumour response and by a lack of targeted radiosensitising drugs that can improve the therapeutic index, especially by limiting side effects such as bladder fibrosis. In order to improve the bladder-preserving treatment, experimental studies addressing these main issues ought to be considered (both in vitro and in vivo studies). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews, we conducted a literature search in PubMed on experimental studies investigating how to improve bladder cancer radiotherapy with different radiosensitising agents using a comprehensive search string. We made comments on experimental model selection, experimental design and results, formulating the gaps of knowledge still existing: such as the lack of reliable predictive biomarkers of tumour response to chemoradiation according to the molecular tumour subtype and lack of efficient radiosensitising agents specifically targeting bladder tumour cells. We provided guidance to improve forthcoming studies, such as taking into account molecular characteristics of the preclinical models and highlighted the value of using patient-derived xenografts as well as syngeneic models. Finally, this review could be a useful tool to set up new radiation-based combined treatments with an improved therapeutic index that is needed for bladder preservation.

Cdc20 induces the radioresistance of bladder cancer cells by targeting FoxO1 degradation

Ionizing radiation is a conventional therapy for cancer patients, but patients often experience distant metastasis and recurrence, which lead to a poor prognosis after the implementation of this treatment. Moreover, the underlying mechanisms by which radioresistance contributes to metastatic potential is still elusive. Here, we explored the molecular mechanisms that contribute to radioresistance in bladder cancer. To achieve this, we established two irradiation-resistant (IR) cell lines, T24R and 5637R, which were derived from parental bladder cancer cell lines. Cell viability was detected by CCK-8 assay, while migration and invasion abilities were examined by wound healing and Transwell chamber assays, respectively. Furthermore, the role of Cdc20 in the regulation of epithelial to mesenchymal transition (EMT) in IR cells was explored by Western blotting, immunoprecipitation and immunofluorescence staining. The IR cells exhibited EMT properties, and our data showed that Cdc20 expression was significantly elevated in IR cells. Remarkably, Cdc20 silencing reversed the EMT phenotype in IR cells. Mechanistically, Cdc20 governed IR-mediated EMT in part by governing forkhead box O1 (FoxO1) degradation. Taken together, our findings showed that the inactivation of Cdc20 or the activation of FoxO1 might be a potential strategy to overcome radioresistance in bladder cancer.

Contrast effects of autophagy in the treatment of bladder cancer

Bladder cancer is a disease that negatively affects patients' quality of life, but treatment options have remained unchanged for a long time. Although promising results have been achieved with current bladder cancer treatments, cancer recurrence, progression, and therapy resistance are the most severe problems preventing the efficiency of bladder cancer treatments. Autophagy refers to an evolutionarily conserved catabolic process in which proteins, damaged organelles, and cytoplasmic components are degraded by lysosomal enzymes. Autophagy regulates the therapeutic response to the chemotherapy drugs, thus determining the effect of therapy on cancer cells. Autophagy is a stress-induced cell survival mechanism and its excessive stimulation can cause resistance of tumor cells to therapeutic agents. Depending on the conditions, an increase in autophagy may cause treatment resistance or autophagic cell death, and it is related to important anti-cancer mechanisms, such as apoptosis. Therefore, understanding the roles of autophagy under different conditions is important for designing effective anti-cancer agents. The dual role of autophagy in cancer has attracted considerable attention in respect of bladder cancer treatment. In this review, we summarize the basic characteristics of autophagy, including its mechanisms, regulation, and functions, and we present examples from current studies concerning the dual role of autophagy in bladder cancer progression and therapy.

Atorvastatin Enhances Effects of Radiotherapy on Prostate Cancer Cells and Xenograft Tumor Mice Through Triggering Interaction Between Bcl-2 and MSH2

BACKGROUND Prostate cancer (PCa) is considered to be the 4th most common cancer in males in the world. This study aimed to explore effects of atorvastatin on colony formation of PCa cells and radio-resistance of xenograft tumor models. MATERIAL AND METHODS PCa cell lines, including PC3, DU145, and Lncap, were treated with irradiation (4 Gy) and/or atorvastatin (6 μg/mL). Cells were divided into tumor cell group, irradiation treatment group (IR group) and irradiation+atorvastatin treatment group (IR-AS group). Xenograft tumor mouse model was established. Plate clone formation assay (multi-target/single-hit model) was conducted to evaluate colony formation. Flow cytometry analysis was employed to detect apoptosis. Interaction between Bcl-2 and MSH2 was evaluated with immuno-fluorescence assay. RESULTS According to the plate colony formation assay and multi-target/single-hit model, IR-treatment significantly suppressed colony formation in PCa cells (including PC3, DU145, and Lncap cells) compared to no-IR treated cells (P<0.05). Atorvastatin remarkably enhanced inhibitive effects of irradiation on colony formation of PCa cells (P<0.05), however, the IR+AS group demonstrated no effects on apoptosis, comparing to IR group (P>0.05). Atorvastatin administration (IR+AS group) significantly reduced tumor size of IR-treated PCa cells-induced xenograft tumor mice (P<0.05). Bcl-2 interacted with MSH2 both in tumor tissues of xenograft tumor mice. CONCLUSIONS Atorvastatin administration inhibited colony formation in PCa cells and enhanced effects of radiotherapy on tumor growth of xenograft tumor mice, which might be associated with interaction between Bcl-2 and MSH2 molecule.

The interactions and communications in tumor resistance to radiotherapy: Therapy perspectives

Tumor microenvironment (TME) includes a wide range of cell types including cancer cells, cells which are involved in stromal structure and immune cells (tumor suppressor and tumor promoting cells). These cells have several interactions with each other that are mainly regulated via the release of intercellular mediators. Radiotherapy can modulate these interactions via shifting secretions into inflammatory or anti-inflammatory responses. Radiotherapy also can trigger resistance of cancer (stem) cells via activation of stromal cells. The main mechanisms of tumor resistance to radiotherapy is the exhaustion of anti-tumor immunity via suppression of CD4+ T cells and apoptosis of cytotoxic CD8+ T lymphocytes (CTLs). Cancer-associated fibroblasts (CAFs), mesenchymal-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) are the main suppressor of anti-tumor immunity via the release of several chemokines, cytokines and immune suppressors. In this review, we explain the main cellular and molecular interactions and secretions in TME following radiotherapy. Furthermore, the main signaling pathways and intercellular connections that can be targeted to improve therapeutic efficiency of radiotherapy will be discussed.

HMGB1 in Radiotherapy: A Two Headed Signal Regulating Tumor Radiosensitivity and Immunity

Radiotherapy (RT) is a mainstay of cancer treatment. Recent studies have shown that RT not only directly induces cell death but also has late and sustained immune effects. High mobility group box 1 (HMGB1) is a nuclear protein released during RT, with location-dependent functions. It is essential for normal cellular function but also regulates the proliferation and migration of tumor cells by binding to high-affinity receptors. In this review, we summarize recent evidence on the functions of HMGB1 in RT according to the position, intracellular HMGB1 and extracellular HMGB1. Intracellular HMGB1 induces radiation tolerance in tumor cells by promoting DNA damage repair and autophagy. Extracellular HMGB1 plays a more intricate role in radiation-related immune responses, wherein it not only stimulates the anti-tumor immune response by facilitating the recognition of dying tumor cells but is also involved in maintaining immunosuppression. Factors that potentially affect the role of HMGB1 in RT-induced cytotoxicity have also been discussed in the context of possible therapeutic applications, which helps to develop effective and targeted radio-sensitization therapies.

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.

LncRNA HOTAIR enhances breast cancer radioresistance through facilitating HSPA1A expression via sequestering miR-449b-5p

Background

Breast cancer (BRCA) is the leading cause of cancer‐related death in women worldwide. Pre‐ and postoperative radiotherapy play a pivotal role in BRCA treatment but its efficacy remains limited and plagued by the emergence of radiation resistance, which aggravates patient prognosis. The long noncoding RNA (lncRNA)‐implicated mechanisms underlying radiation resistance are rarely reported. The aim of this study was to determine whether lncRNA HOX transcript antisense RNA (HOTAIR) modulated the radiosensitivity of breast cancer through HSPA1A.

Methods

A Gammacell 40 Exactor was used for irradiation treatment. Bioinformatic tools and luciferase reporter assay were adopted to explore gene expression profile and demonstrate the interactions between lncRNA, miRNA and target mRNA 3′‐untranslated region (3′‐UTR). The expression levels of certain genes were determined by real‐time PCR and western‐blot analyses. in vitro and in vivo functional assays were conducted by cell viability and tumorigenicity assays.

Results

The levels of oncogenic lncRNA HOTAIR were positively correlated with the malignancy of BRCA but reversely correlated with the radiosensitivity of breast cancer cells. Moreover, the expression levels of HOTAIR were positively associated with those of heat shock protein family A (Hsp70) member 1A (HSPA1A) in clinical BRCA tissues and HOTAIR upregulated HSPA1A at the mRNA and protein levels in irradiated BRCA cells. Mechanistically, miR‐449b‐5p restrained HSPA1A expression through targeting the 3′‐UTR of HSPA1A mRNA, whereas HOTAIR acted as a competing sponge to sequester miR‐449b‐5p and thereby relieved the miR‐449b‐5p‐mediated HSPA1A repression. Functionally, HOTAIR conferred decreased radiosensitivity on BRCA cells, while miR‐449b‐5p overexpression or HSPA1A knockdown abrogated the HOTAIR‐enhanced BRCA growth under the irradiation exposure both in vitro and in vivo.

Conclusions

LncRNA HOTAIR facilitates the expression of HSPA1A by sequestering miR‐449b‐5p post‐transcriptionally and thereby endows BRCA with radiation resistance.

Key points

Therapeutically, HOTAIR and HSPA1A may be employed as potential targets for BRCA radiotherapy. Our findings shed new light into the mechanism by which lncRNAs modulate the radiosensitivity of tumors.

Long noncoding RNA NNT-AS1 enhances the malignant phenotype of bladder cancer by acting as a competing endogenous RNA on microRNA-496 thereby increasing HMGB1 expression

The long noncoding RNA nicotinamide nucleotide transhydrogenase antisense RNA 1 (NNT-AS1) is a key malignancy regulator in a variety of human cancers. In this study, we first measured the expression of NNT-AS1 in bladder cancer and examined its role in cancer progression. The mechanisms behind the oncogenic functions of NNT-AS1 in bladder cancer were explored. We found that NNT-AS1 was upregulated in bladder cancer tissues and cell lines. This increased expression demonstrated a significant correlation with advanced clinical stage, lymph node metastasis, and shorter overall survival. NNT-AS1 knockdown suppressed bladder cancer cell proliferation, migration, and invasion and facilitated apoptosis in vitro and hindered tumor growth in vivo. NNT-AS1 functioned as a competing endogenous RNA for microRNA-496 (miR-496), and the suppressive effects of NNT-AS1 knockdown on malignant characteristics were abrogated by miR-496 silencing. HMGB1 was identified as a direct target gene of miR-496 in bladder cancer, and HMGB1 expression was enhanced by NNT-AS1 via sponging of miR-496. In conclusion, the NNT-AS1–miR-496–HMGB1 pathway plays a significant role in the aggressive behavior of bladder cancer and may lead to new NNT-AS1–based diagnostics and therapeutics.

Glutamine affects T24 bladder cancer cell proliferation by activating STAT3 through ROS and glutaminolysis

Changes in metabolism are common phenomena in tumors. Glutamine (Gln) has been documented to play a critical role in tumor growth. In this study, we aimed to to explore the mechanisms through which bladder cancer cells utilize Gln to fulfill their biosynthetic needs during proliferation. In addition, the roles of Gln in the tricarboxylic acid (TCA) cycle, reactive oxygen species (ROS) regulation, and signal transducer and activator of transcription 3 (STAT3) expression were examined in vitro in the T24 bladder cancer cell line. The results revealed that the T24 cell line was markedly Gln-dependent and that Gln supplementation promoted T24 proliferation through the actions of Gln as a ROS moderator and as a metabolic fuel in the TCA cycle. Importantly, extracellular Gln deprivation deregulated the production of the transcription factor, STAT3. Additionally, STAT3 expression was affected by the degree of Gln metabolism, as regulated by Gln intermediates and ROS. Thus, on the whole, the findings of this study demonstrate that Gln promotes the proliferation of the Gln-dependent bladder cancer cell line, T24, by supplementing adenosine triphosphate (ATP) production and neutralizing ROS to activate the STAT3 pathway.

PD-1/PD-L1 Immune Checkpoint Inhibition with Radiation in Bladder Cancer: In Situ and Abscopal Effects

The combination of radiation with immune checkpoint inhibitors was reported in some cancers to have synergic effects both locally and distally. Our aim was to assess this combined therapy on both radiated and nonradiated bladder tumors and to characterize the immune landscape within the tumor microenvironment. Murine bladder cancer cells (MB49) were injected subcutaneously in both flanks of C57BL/6 mice. Mice were randomly assigned to the following treatments: placebo, anti-PD-L1 (four intraperitoneal injections over 2 weeks), radiation to right flank (10 Gy in two fractions), or radiation+anti-PD-L1. Tumor digestion, flow cytometry, and qPCR were performed. Log-rank analysis was used for statistical significance. Radiation+anti-PD-L1 group demonstrated statistically significant slower tumor growth rate both in the radiated and nonirradiated tumors (P < 0.001). Survival curves demonstrated superior survival in the combination group compared with each treatment alone (P = 0.02). Flow cytometry showed increased infiltration of immunosuppressive cells as well as CTL in the radiation and combination groups (P = 0.04). Ratio of immunosuppressive cells to CTL shifted in favor of cytotoxic activity in the combination arm (P < 0.001). The qPCR analysis revealed downregulation of immunosuppressive genes (CCL22, IL22, and IL13), as well as upregulation of markers of CTL activation (CXCL9, GZMA, and GZMB) within both the radiated and distant tumors within the combination group. Combining radiation with immune checkpoint inhibitor provided better response in the radiated tumors and also the distant tumors along with a shift within the tumor microenvironment favoring cytotoxic activity. These findings demonstrate a possible abscopal effect in urothelial carcinoma with combination therapy.

Interactions of high mobility group box protein 1 (HMGB1) with nucleic acids: Implications in DNA repair and immune responses

High mobility group box protein 1 (HMGB1) is a highly versatile, abundant, and ubiquitously expressed, non-histone chromosomal protein, which belongs to the HMGB family of proteins. These proteins form an integral part of the architectural protein repertoire to support chromatin structure in the nucleus. In the nucleus, the role of HMGB1 is attributed to its ability to bind to undamaged DNA, damaged DNA, and alternative (i.e. non-B) DNA structures with high affinity and subsequently induce bending of the DNA substrates. Due to its binding to DNA, HMGB1 has been implicated in critical biological processes, such as DNA transcription, replication, repair, and recombination. In addition to its intracellular functions, HMGB1 can also be released in the extracellular space where it elicits immunological responses. HMGB1 associates with many different molecules, including DNA, RNA, proteins, and lipopolysaccharides to modulate a variety of processes in both DNA metabolism and in innate immunity. In this review, we will focus on the implications of the interactions of HMGB1 with nucleic acids in DNA repair and immune responses. We report on the roles of HMGB1 in nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR) and DNA double-strand break repair (DSBR). We also report on its roles in immune responses via its potential effects on antigen receptor diversity generation [V(D)J recombination] and interactions with foreign and self-nucleic acids. HMGB1 expression is altered in a variety of cancers and immunological disorders. However, due to the diversity and complexity of the biological processes influenced by HMGB1 (and its family members), a detailed understanding of the intracellular and extracellular roles of HMGB1 in DNA damage repair and immune responses is warranted to ensure the development of effective HMGB1-related therapies.

The immune mediated role of extracellular HMGB1 in a heterotopic model of bladder cancer radioresistance

Radical cystectomy (RC) together with bilateral pelvic lymph node dissection remains the standard treatment for muscle invasive bladder cancer (MIBC). However, radiation-based treatments such as tri-modal therapy (TMT) involving maximally performed transurethral resection of bladder tumor (TURBT), radiotherapy (XRT), and a chemosensitizer represent an attractive, less invasive alternative. Nevertheless, 25–30% of MIBC patients will experience local recurrence after TMT and half will develop metastasis. Radioresistance of tumor cells could potentially be one of the causes for local recurrence post treatment. High mobility group box-1 (HMGB1) was shown to play a role in bladder cancer radioresistance through its intracellular functions in promoting DNA damage repair and autophagy. Recently, HMGB1 was found to be passively released from irradiated tumor cells. However, less is known about the involvement of extracellular HMGB1 in impairing radiation response and its exact role in modulating the tumor immune microenvironment after XRT. We identified a novel mechanism of bladder cancer radioresistance mediated by the immunological functions of HMGB1. The combination of radiation plus extracellular HMGB1 inhibition markedly improved the radiation response of tumors and resulted in marked changes in the immune landscape. Moreover, combining radiation and HMGB1 inhibition significantly impaired tumor infiltrating MDSCs and TAMs -but not Tregs- and shifted the overall tumor immune balance towards anti-tumoral response. We conclude that extracellular HMGB1 is involved in bladder cancer radioresistance through promoting pro-tumor immune mechanisms.

High mobility group box 1 promotes radioresistance in esophageal squamous cell carcinoma cell lines by modulating autophagy

Resistance to radiotherapy results in relapse and treatment failure in locally advanced esophageal squamous cell carcinoma (ESCC). High mobility group box 1 (HMGB1) is reported to be associated with the radioresistance in bladder and breast cancer. However, the role of HMGB1 in the radiotherapy response in ESCC has not been fully elucidated. Here, we investigated the role of HMGB1 to radioresistance in ESCC clinical samples and cell lines. We found that HMGB1 expression was associated with tumor recurrence after postoperative radiotherapy in locally advanced ESCC patients. HMGB1 knockdown in ESCC cells resulted in increased radiosensitivity both in vitro and in vivo. Autophagy level was found depressed in HMGB1 inhibition cells and activation of autophagy brought back cell’s radioresistance. Our results demonstrate that HMGB1 activate autophagy and consequently promote radioresistance. HMGB1 may be used as a predictor of poor response to radiotherapy in ESCC patients. Our finding also highlights the importance of the utility of HMGB1 in ESCC radiosensitization.

Cytoplasmic HMGB1 and HMGB1-Beclin1 complex are increased in radioresistant oral squamous cell carcinoma

Cytoplasmic high mobility group box 1 (HMGB1) is an autophagy regulator, and autophagy is important in the radioresistance of various solid cancers. We evaluated the degree of autophagy and cytoplasmic HMGB1 in radioresistant oral squamous cell carcinoma (SCC) by culturing the SCC15 and quasiliquid layer 1 (QLL1) SCC cell lines that originate from cancer of the oral tongue and a metastatic lymph node, respectively, and then delivered radiation to induce radioresistance to cells. We then compared the degree of autophagy between non-irradiated control and radioresistant cancer cells using a western blot assay. We also compared the total and cytoplasmic concentrations of HMGB1 between the non-irradiated control and radioresistant cancer cells by western blot assay, and extracellular concentrations of HMGB1 with an enzyme-linked immunosorbent assay (ELISA). Formation of an HMGB1-Beclin1 complex was evaluated by immunofluorescence and co-immunoprecipitation assays. Autophagy increased in the radioresistant SCC15 cells (compared with non-irradiated control SCC15 cells) but not in the radioresistant QLL1 cells. The total amount of HMGB1 expression within cells did not differ; however, the degree of cytoplasmic HMGB1 expression was higher in radioresistant SCC15 cells than in non-irradiated control SCC15 cells. The HMGB1-Beclin1 complex, which is a main regulator of autophagy, was also increased in radioresistant SCC15 cells compared with non-irradiated control SCC15 cells. Autophagy flux and cytoplasmic HMGB1-Beclin1 increased after the acquisition of radioresistance in oral SCC.

Med19 is involved in chemoresistance by mediating autophagy through HMGB1 in breast cancer

Adriamycin (ADM)-based regimens are the most effective chemotherapeutic treatments for breast cancer. However, intrinsic and acquired chemoresistance is a major therapeutic problem. Our goal was to clarify the role of mediator complex subunit 19 (Med19) in chemotherapy resistance and to elucidate the related molecular mechanisms. In this study, ADM-resistant human cells (MCF-7/ADM) and tissues exhibited increased Med19 expression and autophagy levels relative to the corresponding control groups. Additionally, MCF-7/ADM cells showed changes in two selective markers of autophagy. There was a dose-dependent increase in the light chain 3 (LC3)-II/LC3-I ratio and a decrease in sequestosome 1 (P62/SQSTMl) expression. Furthermore, lentivirus-mediated Med19 inhibition significantly attenuated the LC3-II/LC3-I ratio, autophagy-related gene 3 (Atg3) and autophagy-related gene 5 (Atg5) expression, P62 degradation, and red fluorescent protein-LC3 dot formation after treatment with ADM or rapamycin, an autophagy activator. Furthermore, the antiproliferative effects of ADM, cisplatin (DDP), and taxol (TAX) were significantly enhanced after suppressing Med19 expression. Notably, the effects of Med19 on autophagy were mediated through the high-mobility group box-1 (HMGB1) pathway. Our findings suggest that Med19 suppression increased ADM chemosensitivity by downregulating autophagy through the inhibition of HMGB1 signaling in human breast cancer cells. Thus, the regulatory mechanisms of Med19 in autophagy should be investigated to reduce tumor resistance to chemotherapy.

The progression of HMGB1-induced autophagy in cancer biology

Autophagy is an important process of cellular degradation and has been proven to contribute to tumorigenesis. High-mobility group box 1 (HMGB1) is an abundant nonhistone protein that has been widely reported to play a central role in the induction of autophagy. In nucleus, HMGB1 upregulates the expression of HSP27 to induce autophagy. In cytoplasm, the Beclin-1/PI3K-III complex can be activated by HMGB1 to promote autophagy. Extracellular HMGB1 binds to the receptor for advanced glycation end products to induce autophagy. Recent studies have shown that HMGB1-induced autophagy exerts multiple functions in various cancers like proliferation. Moreover, inhibition of HMGB1-induced autophagy can reverse chemoresistance, which is regulated by noncoding RNAs such as microRNAs and lncRNAs. Here, we provide a brief introduction to HMGB1 and HMGB1-induced autophagy in cancer. We also discuss the challenges associated with performing further investigations on this issue. HMGB1-induced autophagy exerts significant functions in cancer and has potential utility for new strategy to reverse drug resistance.

Bladder Preservation Therapy: Review of Literature and Future Directions of Trimodal Therapy

PURPOSE OF THE REVIEW

This review targets the latest literature on bladder preservation therapy with emphasis on trimodal therapy (TMT), highlighting its role in the management of muscle invasive bladder cancer (MIBC) and outlining future directions in bladder preservation research.

RECENT FINDINGS

TMT is the most promising bladder preservation treatment modality. Comparable results to contemporary radical cystectomy series are seen in properly selected patients. A multidisciplinary team approach is critical in the management of these patients. Future research is directed at the integration of immunotherapy into the treatment protocol. TMT, involving maximal transurethral resection followed by chemoradiation, is an attractive alternative to radical cystectomy with urinary diversion in carefully selected patients with muscle invasive disease. In the absence of randomized trial (RCT), comparison between TMT and cystectomy, based on retrospective data from large centers, suggests comparable oncological outcomes, with a favorable impact on quality of life.

The multifaceted role of autophagy in cancer and the microenvironment

Autophagy is a crucial recycling process that is increasingly being recognized as an important factor in cancer initiation, cancer (stem) cell maintenance as well as the development of resistance to cancer therapy in both solid and hematological malignancies. Furthermore, it is being recognized that autophagy also plays a crucial and sometimes opposing role in the complex cancer microenvironment. For instance, autophagy in stromal cells such as fibroblasts contributes to tumorigenesis by generating and supplying nutrients to cancerous cells. Reversely, autophagy in immune cells appears to contribute to tumor‐localized immune responses and among others regulates antigen presentation to and by immune cells. Autophagy also directly regulates T and natural killer cell activity and is required for mounting T‐cell memory responses. Thus, within the tumor microenvironment autophagy has a multifaceted role that, depending on the context, may help drive tumorigenesis or may help to support anticancer immune responses. This multifaceted role should be taken into account when designing autophagy‐based cancer therapeutics. In this review, we provide an overview of the diverse facets of autophagy in cancer cells and nonmalignant cells in the cancer microenvironment. Second, we will attempt to integrate and provide a unified view of how these various aspects can be therapeutically exploited for cancer therapy.

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

Background

With the development of novel therapeutic agents, the survival of multiple myeloma (MM) patients has much improved. However, the disease is incurable due to drug resistance. Previous studies have found that high-mobility group box 1 (HMGB1) is involved in inflammation, angiogenesis, DNA damage repair, and cancer invasion, progression, metastasis and drug resistance and that high HMGB1 expression is associated with poor MM prognosis, yet the role and mechanism of HMGB1 in MM remains unclear.

Methods

Through gene expression and Oncomine database analyses, we found that HMGB1 is associated with a poor prognosis in MM patients. RNA interference together with gene array analysis, cell proliferation and apoptosis assays, autophagy detection assays, western blotting, and in vivo xenograft models were employed to evaluate the effect of HMGB1 and the mechanism involved in MM drug resistance.

Results

MM cell lines and primary MM samples were found to express high levels of HMGB1, which was negatively associated with the 3-year survival of MM patients. HMGB1 knockdown in MM cells enhanced the inhibitory effect of chemotherapy with dexamethasone (Dex) via apoptosis induction. Furthermore, downregulation of HMGB1 activated the mTOR pathway, inhibited autophagy and increased DNA damage induced by Dex by modulating expression of related genes. In vivo, xenograft models showed that after Dex treatment, the tumor burden of HMGB1-knockdown mice was decreased compared with that of control mice.

Conclusions

Our research shows that HMGB1 participates in autophagy and DNA damage repair and that downregulation of HMGB1 enhances the sensitivity of MM cells to Dex, suggesting that HMGB1 may serve as a target for MM treatment.

Wnt signaling induces radioresistance through upregulating HMGB1 in esophageal squamous cell carcinoma

Although many articles have uncovered that Wnt signaling is involved in radioresistance, the mechanism is rarely reported. Here we generated two radioresistant cells rECA109 and rKyse150 from parental esophageal cancer cells ECA109 and Kyse150. We then found that Wnt signaling activity was higher in radioresistant cells and was further activated upon ionizing radiation (IR) exposure. In addition, radioresistant cells acquired epithelial-to-mesenchymal transition (EMT) properties and stem quality. Wnt signaling was then found to be involved in radioresistance by promoting DNA damage repair. In our present study, high-mobility group box 1 protein (HMGB1), a chromatin-associated protein, was firstly found to be transactivated by Wnt signaling and mediate Wnt-induced radioresistance. The role of HMGB1 in the regulation of DNA damage repair with the activation of DNA damage checkpoint response in response to IR was the main cause of HMGB1-induced radioresistance.

MicroRNA-935 Inhibits Proliferation and Invasion of Osteosarcoma Cells by Directly Targeting High Mobility Group Box 1

Numerous studies have suggested that microRNAs (miRNAs) are dysregulated in osteosarcoma (OS), implicating miRNAs in OS initiation and progression. Therefore, knowledge of aberrantly expressed miRNAs in OS may provide novel mechanistic insights into the tumorigenesis and tumor development of OS and facilitate therapeutic methods for patients with this aggressive bone neoplasm. In this study, data obtained from reverse transcription quantitative polymerase chain reaction (RT-qPCR) revealed that miR-935 was significantly decreased in OS tissues and cell lines. Restoration expression of miR-935 obviously restricted proliferation and invasion of OS cells. In addition, high-mobility group box 1 (HMGB1) was predicted to be a putative target of miR-935. Subsequent dual-luciferase reporter assay, RT-qPCR, and Western blot analysis confirmed that miR-935 could directly target the 3′-untranslated region of HMGB1 and negatively regulated HMGB1 expression in OS cells. Furthermore, a significant negative association was found between miR-935 and HMGB1 mRNA expression in OS tissues. Rescue experiments showed that recovery of HMGB1 expression partially rescued miR-935-induced suppression of cell proliferation and invasion in OS. These results provide the first evidence for the suppressive roles of miR-935 in OS by directly targeting HMGB1, suggesting that miR-935 may be a potential candidate for the treatment of patients with this disease.

Effect of HMGB1 Polymorphisms on Urothelial Cell Carcinoma Susceptibility and Clinicopathological Characteristics

The high mobility group box 1 gene (HMGB1) plays a prominent role in cancer progression, angiogenesis, invasion, and metastasis. This study explored the effect of HMGB1 polymorphisms on clinicopathological characteristics of urothelial cell carcinoma (UCC). In total, 1293 participants (431 patients with UCC and 862 healthy controls) were recruited. Four single-nucleotide polymorphisms (SNPs) of HMGB1 (rs1412125, rs1360485, rs1045411, and rs2249825) were assessed using TaqMan real-time polymerase chain reaction assay. The results indicated that individuals carrying at least one T allele at rs1045411 had a lower risk of UCC than those with the wild-type allele [adjusted odds ratio = 0.722, 95% confidence interval (CI) = 0.565-0.924]. Furthermore, female patients with UCC carrying at least one T allele at rs1045411 were at a lower invasive tumor stage than those with the wild-type allele [odds ratio (OR) = 0.396, 95% CI = 0.169-0.929], similar to nonsmoking patients (OR = 0.607, 95% CI = 0.374-0.985). In conclusion, this is the first report on correlation between HMGB1 polymorphisms and UCC risk. Individuals carrying at least one T allele at rs1045411 are associated with a lower risk of UCC and a less invasive disease in women and nonsmokers.

Genetic determinants for chemo- and radiotherapy resistance in bladder cancer

Bladder cancer (BCa) is burdened by high rates of chemo- and radio-resistance. We reviewed and summarized the current evidence regarding the genetic determinants of resistance in patients treated with chemotherapy and/or radiotherapy (RT) for BCa. Genetic heterogeneity may preexist to treatment arising with tumorigenesis or increasing progressively during the treatment. Several biological pathways seem to be involved in the cellular response to treatment. These pathways comprehend mechanisms leading to modify the intracellular concentration of the drug, mechanisms leading to increase the repair of DNA damage caused by the treatment, mechanisms leading to increase cell survival, despite DNA damage, acting on the signaling pathways affecting apoptosis, mechanisms promoting autophagy. In the present review, we focused on the genetic determinants of resistance affecting the aforementioned mechanisms.

"Stealth dissemination" of macrophage-tumor cell fusions cultured from blood of patients with pancreatic ductal adenocarcinoma

Here we describe isolation and characterization of macrophage-tumor cell fusions (MTFs) from the blood of pancreatic ductal adenocarcinoma (PDAC) patients. The MTFs were generally aneuploidy, and immunophenotypic characterizations showed that the MTFs express markers characteristic of PDAC and stem cells, as well as M2-polarized macrophages. Single cell RNASeq analyses showed that the MTFs express many transcripts implicated in cancer progression, LINE1 retrotransposons, and very high levels of several long non-coding transcripts involved in metastasis (such as MALAT1). When cultured MTFs were transplanted orthotopically into mouse pancreas, they grew as obvious well-differentiated islands of cells, but they also disseminated widely throughout multiple tissues in "stealth" fashion. They were found distributed throughout multiple organs at 4, 8, or 12 weeks after transplantation (including liver, spleen, lung), occurring as single cells or small groups of cells, without formation of obvious tumors or any apparent progression over the 4 to 12 week period. We suggest that MTFs form continually during PDAC development, and that they disseminate early in cancer progression, forming "niches" at distant sites for subsequent colonization by metastasis-initiating cells.

Cytolethal Distending Toxin Enhances Radiosensitivity in Prostate Cancer Cells by Regulating Autophagy

Cytolethal distending toxin (CDT) produced by Campylobacter jejuni contains three subunits: CdtA, CdtB, and CdtC. Among these three toxin subunits, CdtB is the toxic moiety of CDT with DNase I activity, resulting in DNA double-strand breaks (DSB) and, consequently, cell cycle arrest at the G2/M stage and apoptosis. Radiation therapy is an effective modality for the treatment of localized prostate cancer (PCa). However, patients often develop radioresistance. Owing to its particular biochemical properties, we previously employed CdtB as a therapeutic agent for sensitizing radioresistant PCa cells to ionizing radiation (IR). In this study, we further demonstrated that CDT suppresses the IR-induced autophagy pathway in PCa cells by attenuating c-Myc expression and therefore sensitizes PCa cells to radiation. We further showed that CDT prevents the formation of autophagosomes via decreased high-mobility group box 1 (HMGB1) expression and the inhibition of acidic vesicular organelle (AVO) formation, which are associated with enhanced radiosensitivity in PCa cells. The results of this study reveal the detailed mechanism of CDT for the treatment of radioresistant PCa.

HMGB1-mediated autophagy attenuates gemcitabine-induced apoptosis in bladder cancer cells involving JNK and ERK activation

High-mobility group box 1 (HMGB1) has been found to mediate autophagy during chemotherapy in several cancers. However, whether HMGB1plays a role in autophagy and chemoresistance in bladder cancer is elusive. In this report, HMGB1 expression was found to be increased in 30 primary bladder cancer tissue specimens compared to their matched adjacent non-tumor tissues. While gemcitabine induced apoptotic cell death, it also induced HMGB1 expression and autophagy in bladder cancer T24 and BIU-87 cells. Suppressing HMGB1 expression with siRNA strongly potentiated gemcitabine-induced apoptosis. HMGB1 siRNA or autophagy inhibitors suppressed gemcitabine-induced autophagy. Further, gemcitabine activated c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinase (ERK) and Bcl-2 phosphorylation, and blocking ERK and JNK inhibited autophagy and increased apoptosis in gemcitabine-treated cells. Interestingly, suppressing HMGB1 expression attenuated gemcitabine-induced ERK and JNK activation and Bcl-2 phosphorylation. Thus, our results suggest that while gemcitabine kills bladder cancer cells through apoptosis, a cytoprotective autophagy is also induced involving HMGB1-mediated JNK and ERK to counteract the cytotoxicity of gemcitabine, and intervention targeting this pathway may improve the anticancer efficacy of gemcitabine against bladder cancer.

Down-regulation of LncRNA TUG1 enhances radiosensitivity in bladder cancer via suppressing HMGB1 expression

Background

Long non-coding RNAs (lncRNAs) have been reported to regulate the sensitivity of different cancer cells to chemoradiotherapy. Aberrant expression of lncRNA Taurine-upregulated gene 1 (TUG1) has been found to be involved in the development of bladder cancer, however, its function and underlying mechanism in the radioresistance of bladder cancer remains unclear.

Methods

Quantitative real-time PCR (qRT-PCR) was conducted to measure the expression of TUG1 and HMGB1 mRNA in bladder cancer tissues and cell lines. HMGB1 protein levels were tested by western blot assays. Different doses of X-ray were used for radiation treatment of bladder cancer cells. Colony survival and cell viability were detected by clonogenic assay and CCK-8 Kit, respectively. Cell apoptosis was determined by flow cytometry. A xenograft mouse model was constructed to observe the effect of TUG1 on tumor growth in vivo.

Results

The levels of TUG1 and HMGB1 were remarkably increased in bladder cancer tissues and cell lines. Radiation treatment markedly elevated the expression of TUG1 and HMGB1. TUG1 knockdown inhibited cell proliferation, promoted cell apoptosis and decreased colony survival in SW780 and BIU87 cells under radiation. Moreover, TUG1 depletion suppressed the HMGB1 mRNA and protein levels. Furthermore, overexpression of HMGB1 reversed TUG1 knockdown-induced effect in bladder cancer cells. Radiation treatment dramatically reduced the tumor volume and weight in xenograft model, and this effect was more obvious when combined with TUG1 silencing.

Conclusion

LncRNA TUG1 knockdown enhances radiosensitivity of bladder cancer by suppressing HMGB1 expression. TUG1 acts as a potential regulator of radioresistance of bladder cancer, and it may represent a promising therapeutic target for bladder cancer patients.