HIF-1α/MDR1 pathway confers chemoresistance to cisplatin in bladder cancer

Unsymmetrical Bisacridines' Interactions with ABC Transporters and Their Cellular Impact on Colon LS 174T and Prostate DU 145 Cancer Cells

Multidrug resistance (MDR) is a process that constitutes a significant obstacle to effective anticancer therapy. Here, we examined whether unsymmetrical bisacridines (UAs) are substrates for ABC transporters and can influence their expression in human colon LS 174T and prostate DU 145 cancer cells. Moreover, we investigated the cytotoxicity and the cellular response induced by UAs in these cells. The ATPase activities of MDR1, MRP1, and MRP2 were measured using vesicles prepared from insect Sf9 cells expressing particular ABC transporters. The gene expression and protein levels were analyzed using qPCR and Western blotting. The cellular effects were studied by MTT (cytotoxicity), flow cytometry (cell cycle analysis and phosphatidylserine externalization), and fluorescence microscopy. We showed that UAs are substrates for MDR1. Importantly, they did not influence remarkably the expressions of the ABCB1, ABCC1, and ABCC2 genes and the levels of the MDR1 and PXR proteins in the studied cells. Furthermore, the cytotoxicity and the level of apoptosis triggered by UAs in LS 174T cells possessing higher expressions of metabolic enzymes were lower compared with DU 145 cells. These results indicate that during possible UA treatment, the occurrence of drug resistance could be limited, which could favor the use of such compounds as potential candidates for future studies.

Impact of ABCB1 and ABCG2 Transporter in Outcome of Gallbladder Cancer

BACKGROUND

Gallbladder cancer (GBC) is a biologically aggressive malignancy requiring appropriate biomarkers to improve its outcome. Role of ABC transporters (ABCB1 and ABCG2) has been linked to cancer aggressiveness, tumorigenesis and multidrug resistance. Herein, we studied the prognostic implication of ABCB1 and ABCG2 in GBC.

METHODS

Fresh tissue (tumour & normal) samples collected from 54 patients who underwent R0 resection, were analysed for mRNA and protein expression of ABCB1 and ABCG2 by quantitative Real-Time PCR and western blotting, respectively, in this prospective study. The molecular findings were correlated with clinical-pathological parameters using χ2 and fisher exact test. The molecular changes in ABCB1 and ABCG2 were analysed for predicting overall survival (OS), disease-free survival (DFS) and response to chemotherapy using Kaplan-Meier log-rank test and Cox regression multivariate analysis.

RESULTS

The mean age of the cohort was 50 ± 13.2 with 26 (48.1%) in patients having early stage gallbladder cancer (GBC). Over-expression of ABCB1 and ABCG2 was noted in 32/54 (59%) and 40/54 (74%) cases, respectively. The protein expression of ABCB1(P-glycoprotein) and ABCG2 (BCRP) was higher in 27/54 (50%) and 37/54 (59%) cases, respectively. The mean OS and DFS was 20.7 ± 11.5 and 19.3 ± 12.2 months at median follow-up of 24 months. The TNM stage, lymph node metastasis, and presence of gallstone were significant factors for predicting OS and DFS on multivariate analysis. Both ABCB1 and ABCG2 did not show any significant correlation with OS and DFS with similar incidences of late death and recurrence among over-expression and down-expression. Sub-group comparison suggests that change in expression pattern of ABCB1 and ABCG2 may not affect response to chemotherapy in GBC.

CONCLUSION

Altered expression of ABCB1 and ABCG2 may not be a useful prognostic marker for survival or response to chemotherapy in GBC. Presently, histo-pathological characteristics and associated gallstones are the important predictors for survival and recurrence in GBC.

Cellular signaling in the hypoxic cancer microenvironment: Implications for drug resistance and therapeutic targeting

The rewiring of cellular metabolism is a defining characteristic of cancer, as tumor cells adapt to acquire essential nutrients from a nutrient-poor environment to sustain their viability and biomass. While hypoxia has been identified as a major factor depriving cancer cells of nutrients, recent studies have revealed that cancer cells distant from supporting blood vessels also face nutrient limitations. To overcome this challenge, hypoxic cancer cells, which heavily rely on glucose as an energy source, employ alternative pathways such as glycogen metabolism and reductive carboxylation of glutamine to meet their energy requirements for survival. Our preliminary studies, alongside others in the field, have shown that under glucose-deficient conditions, hypoxic cells can utilize mannose and maltose as alternative energy sources. This review aims to comprehensively examine the hypoxic cancer microenvironment, its association with drug resistance, and potential therapeutic strategies for targeting this unique niche. Furthermore, we will critically evaluate the current literature on hypoxic cancer microenvironments and explore state-of-the-art techniques used to analyze alternate carbohydrates, specifically mannose and maltose, in complex biological fluids. We will also propose the most effective analytical methods for quantifying mannose and maltose in such biological samples. By gaining a deeper understanding of the hypoxic cancer cell microenvironment and its role in drug resistance, novel therapeutic approaches can be developed to exploit this knowledge.

The Role of Hypoxia-inducible Factor-1 in Bladder Cancer

Bladder cancer (BC) is one of the most common malignant tumors worldwide and poses a significant hazard to human health. During the development of BC, hypoxia plays a crucial role. Hypoxia-inducible factor (HIF) is a key transcription factor for hypoxic adaptation, which regulates the transcription of various genes, including inflammation, angiogenesis, and glycolytic metabolism. Recent studies have shown the precise role of HIF in various biological behaviors of BC. More importantly, a new antitumor medication targeting HIF-2 has been used to treat renal cancer. However, therapies targeting HIF-1 in BC have not yet been developed. In this review, we discussed how HIF-1 is expressed and affects the growth, metastasis, and angiogenesis of BC. At the same time, we investigated several HIF-1 inhibitors that provide new perspectives for targeting HIF-1.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

Microdevices for cancer stem cell culture as a predictive chemotherapeutic response platform

Microfluidic platforms for clinical use are a promising translational strategy for cancer research specially for drug screening. Identifying cancer stem cells (CSC) using sphere culture techniques in microfluidic devices (MDs) showed to be better reproducing physiological responses than other in vitro models and allow the optimization of samples and reagents. We evaluated individual sphere proliferation and stemness toward chemotherapeutic treatment (CT) with doxorubicin and cisplatin in bladder cancer cell lines (MB49-I and J82) cultured in MDs used as CSC treatment response platform. Our results confirm the usefulness of this device to evaluate the CT effect in sphere-forming efficiency, size, and growth rate from individual spheres within MDs and robust information comparable to conventional culture plates was obtained. The expression of pluripotency genetic markers (Oct4, Sox2, Nanog, and CD44) could be analyzed by qPCR and immunofluorescence in spheres growing directly in MDs. MDs are a suitable platform for sphere isolation from tumor samples and can provide information about CT response. Microfluidic-based CSC studies could provide information about treatment response of cancer patients from small samples and can be a promising tool for CSC-targeted specific treatment with potential in precision medicine. KEY MESSAGES: We have designed a microfluidic platform for CSC enriched culture by tumor sphere formation. Using MDs, we could quantify and determine sphere response after CT using murine and human cell lines as a proof of concept. MDs can be used as a tumor-derived sphere isolation platform to test the effect of antitumoral compounds in sphere proliferation.

Classification of formalin-fixed bladder cancer cells with laser tweezer Raman spectroscopy

Bladder cancer is a common cancer that is relatively hard to detect at an early stage because of its non-obvious symptoms. It is known that bladder cells can be found in urine samples which potentially could be used for early detection of bladder cancer. Raman spectroscopy is a powerful non-invasive tool for accessing biochemical information of cells. Combined with laser tweezers, to allow isolation of single cells, Raman spectroscopy has been used to characterise a number of bladder cells that might be found in a urine sample. Using principal component-canonical variates analysis (PC-CVA) and k-fold validation, the results shows that the invasive bladder cancer cells can be identified with accuracy greater than 87%. This demonstrates the potential of developing an early detection method that identifies the invasive bladder cancer cells in urine samples.

Circ_0000235 targets MCT4 to promote glycolysis and progression of bladder cancer by sponging miR-330-5p

Warburg effect plays a crucial role in bladder cancer (Bca) development. However, the mechanism by which glycolysis is involved in Bca remains poorly understood. CircRNAs commonly play a regulatory role in tumor progression. Our study discovered and identified a novel circRNA, hsa_circ_0000235 (circ235), and investigated its role in the glycolytic process, which further results in the progression of Bca. We applied qRT-PCR to assess its clinicopathological relevance and evaluated its proliferation, migration, and glycolytic capacity. We investigated its mechanism using RNA immunoprecipitation, dual-luciferase reporters, and fluorescence in situ hybridization. The findings demonstrated that circ235 was dramatically increased in Bca tissues and was related to a worse prognosis. In vitro studies revealed that circ235 accelerated the rate of extracellular acidification and promoted glucose uptake and lactate manufacture in Bca cells. Additionally, it strengthened the proliferative and migratory capacities. Experiments on animals revealed that downregulating circ235 dramatically reduced carcinogenesis and tumor growth. Circ235 activates monocarboxylate transporter 4 (MCT4) by sponging miR-330-5p, which promotes glycolysis and tumor growth. In conclusion, these findings suggest that circ235 may be a viable molecular marker and therapeutic target for Bca.

Novel cancer treatment paradigm targeting hypoxia-induced factor in conjunction with current therapies to overcome resistance

Chemotherapy, radiotherapy, targeted therapy, and immunotherapy are established cancer treatment modalities that are widely used due to their demonstrated efficacy against tumors and favorable safety profiles or tolerability. Nevertheless, treatment resistance continues to be one of the most pressing unsolved conundrums in cancer treatment. Hypoxia-inducible factors (HIFs) are a family of transcription factors that regulate cellular responses to hypoxia by activating genes involved in various adaptations, including erythropoiesis, glucose metabolism, angiogenesis, cell proliferation, and apoptosis. Despite this critical function, overexpression of HIFs has been observed in numerous cancers, leading to resistance to therapy and disease progression. In recent years, much effort has been poured into developing innovative cancer treatments that target the HIF pathway. Combining HIF inhibitors with current cancer therapies to increase anti-tumor activity and diminish treatment resistance is one strategy for combating therapeutic resistance. This review focuses on how HIF inhibitors could be applied in conjunction with current cancer treatments, including those now being evaluated in clinical trials, to usher in a new era of cancer therapy.

Pesticides and Bladder Cancer: Mechanisms Leading to Anti-Cancer Drug Chemoresistance and New Chemosensitization Strategies

Multiple risk factors have been associated with bladder cancer. This review focuses on pesticide exposure, as it is not currently known whether agricultural products have a direct or indirect effect on bladder cancer, despite recent reports demonstrating a strong correlation. While it is known that pesticide exposure is associated with an increased risk of bladder cancer in humans and dogs, the mechanism(s) by which specific pesticides cause bladder cancer initiation or progression is unknown. In this narrative review, we discuss what is currently known about pesticide exposure and the link to bladder cancer. This review highlights multiple pathways modulated by pesticide exposure with direct links to bladder cancer oncogenesis/metastasis (MMP-2, TGF-β, STAT3) and chemoresistance (drug efflux, DNA repair, and apoptosis resistance) and potential therapeutic tactics to counter these pesticide-induced affects.

Vitamin D increases the efficacy of cisplatin on bladder cancer cell lines

BACKGROUND

1,25(OH)2D3(Calcitriol), which is a broad regulatory molecule, plays a role in changing the efficacy of chemotherapeutic drugs. Cisplatin is one of a current standard chemotherapy regimen for bladder cancer. Increasing the effectiveness of the treatment and reducing the side effects to chemotherapeutics are of great importance in bladder cancer. We aimed to investigate the effect of the combination of cisplatin and calcitriol in order to create a possible advantage in treatment of bladder cancer.

METHODS

T24, ECV-304 and HUVEC cell lines were treated with calcitriol and cisplatin individually and in combination. Dose determination and combination treatments of calcitriol and cisplatin were evaluated using the MTT assay for cytotoxicity analysis on the cells. Annexin V-PI staining method was used for apoptosis determination by flow cytometry. Also the P-gp expression levels were determined by flow cytometry.

RESULTS

The combination treatment increased the anti-proliferative efficacy compared to the efficacy in cisplatin alone in T24 cells and reduced the cytotoxicity in the HUVEC healthy cells compared to cisplatin alone. Combination treatment achieved significantly higher apoptosis rate in T24 cells compared with the rates in treatment of cisplatin alone. However apoptosis decreased in HUVEC cell line. P-gp ratios were increased in HUVEC and decreased in T24 cells with combination treatment compared to the numbers in the control cells. The rate of apoptosis and P-gp levels showed no significant change in ECV-304 cells.

CONCLUSION

Our study revealed that the combination of calcitriol and cisplatin allows the use of cisplatin at lower doses in T24 bladder cancer cell line.

Hypoxia-Inducible Factor-1: A Novel Therapeutic Target for the Management of Cancer, Drug Resistance, and Cancer-Related Pain

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that regulates the transcription of many genes that are responsible for the adaptation and survival of tumor cells in hypoxic environments. Over the past few decades, tremendous efforts have been made to comprehensively understand the role of HIF-1 in tumor progression. Based on the pivotal roles of HIF-1 in tumor biology, many HIF-1 inhibitors interrupting expression, stabilization, DNA binding properties, or transcriptional activity have been identified as potential therapeutic agents for various cancers, yet none of these inhibitors have yet been successfully translated into clinically available cancer treatments. In this review, we briefly introduce the regulation of the HIF-1 pathway and summarize its roles in tumor cell proliferation, angiogenesis, and metastasis. In addition, we explore the implications of HIF-1 in the development of drug resistance and cancer-related pain: the most commonly encountered obstacles during conventional anticancer therapies. Finally, the current status of HIF-1 inhibitors in clinical trials and their perspectives are highlighted, along with their modes of action. This review provides new insights into novel anticancer drug development targeting HIF-1. HIF-1 inhibitors may be promising combinational therapeutic interventions to improve the efficacy of current cancer treatments and reduce drug resistance and cancer-related pain.

Magnesium isoglycyrrhizinate suppresses bladder cancer progression by modulating the miR-26b/Nox4 axis

Magnesium isoglycyrrhizinate (MI), a magnesium salt of 18α-GA stereoisomer, has been reported to exert efficient hepatoprotective activity. However, its effect on bladder cancer remains unclear. The study explored the effects of MI on the growth, colony formation, apoptosis, invasion, and migration of bladder cancer cells (HTB9 and BIU87 cells). Typical apoptotic changes of bladder cancer cells such as nuclear concentration and fragmentation were observed using Hoechst staining. The effects of MI on the expression levels of microRNA-26b (miR-26b), NADPH oxidase 4 (Nox4), nuclear transcription factor-κB (NF-κB), and hHypoxia inducible factor-1α (HIF-1α) were detected using qRT-PCR and Western blot. The potential targets of miR-26b were predicted using Targetscan, and their interactions were determined by luciferase reporter assay. A xenograft mouse model was established to evaluate the anti-tumor effects of MI in vivo. MI significantly suppressed the proliferation, colony formation, invasion, and migration and induced apoptosis of human bladder cancer cells, and MI significantly increased miR-26b expression. Nox 4 was identified to be a direct target of miR-26b. MiR-26b mimics significantly decreased the relative luciferase activity of wild type (WT) Nox 4 but not mutant type (MUT) Nox4. Meanwhile, MI markedly downregulated the expression levels of Nox4, NF-κB, and HIF-1α both in vitro and in vivo. Moreover, MI inhibited xenograft tumor growth in vivo and decreased the expression of Nox4, NF-κB, and HIF-1α. Overall, MI showed a potent anti-tumor effect against bladder cancer partially via modulating the miR-26b/Nox4 axis.

Spheroid Culture Differentially Affects Cancer Cell Sensitivity to Drugs in Melanoma and RCC Models

2D culture as a model for drug testing often turns to be clinically futile. Therefore, 3D cultures (3Ds) show potential to better model responses to drugs observed in vivo. In preliminary studies, using melanoma (B16F10) and renal (RenCa) cancer, we confirmed that 3Ds better mimics the tumor microenvironment. Here, we evaluated how the proposed 3D mode of culture affects tumor cell susceptibility to anti-cancer drugs, which have distinct mechanisms of action (everolimus, doxorubicin, cisplatin). Melanoma spheroids showed higher resistance to all used drugs, as compared to 2D. In an RCC model, such modulation was only observed for doxorubicin treatment. As drug distribution was not affected by the 3D shape, we assessed the expression of MDR1 and mTor. Upregulation of MDR1 in RCC spheroids was observed, in contrast to melanoma. In both models, mTor expression was not affected by the 3D cultures. By NGS, 10 genes related with metabolism of xenobiotics by cytochrome p450 were deregulated in renal cancer spheroids; 9 of them were later confirmed in the melanoma model. The differences between 3D models and classical 2D cultures point to the potential to uncover new non-canonical mechanisms to explain drug resistance set by the tumor in its microenvironment.

TGF-β protects osteosarcoma cells from chemotherapeutic cytotoxicity in a SDH/HIF1α dependent manner

Background

In the widespread adoption of chemotherapy, drug resistance has been the major obstacle to tumor elimination in cancer patients. Our aim was to explore the role of TGF-β in osteosarcoma-associated chemoresistance.

Methods

We performed a cytotoxicity analysis of methotrexate (MTX) and cisplatin (CIS) in TGF-β-treated osteosarcoma cells. Then, the metabolite profile of the core metabolic energy pathways in Saos-2 and MG-63 cell extracts was analyzed by ¹H-NMR. We detected the expression of succinate dehydrogenase (SDH), STAT1, and hypoxia-inducible factor 1α (HIF1α) in TGF-β-treated osteosarcoma cells and further tested the effects of these molecules on the cytotoxicity induced by chemotherapeutic agents. Using in vivo experiments, we examined the tumor growth and survival time of Saos-2-bearing mice treated with a combination of chemotherapeutic agents and a HIF1α inhibitor.

Results

The metabolic analysis revealed enhanced succinate production in osteosarcoma cells after TGF-β treatment. We further found a decrease in SDH expression and an increase in HIF1α expression in TGF-β-treated osteosarcoma cells. Consistently, blockade of SDH efficiently enhanced the resistance of Saos-2 and MG-63 cells to MTX and CIS. Additionally, a HIF1α inhibitor significantly strengthened the anticancer efficacy of the chemotherapeutic drugs in mice with osteosarcoma cancer.

Conclusion

Our study demonstrated that TGF-β attenuated the expression of SDH by reducing the transcription factor STAT1. The reduction in SDH then caused the upregulation of HIF1α, thereby rerouting glucose metabolism and aggravating chemoresistance in osteosarcoma cells. Linking tumor cell metabolism to the formation of chemotherapy resistance, our study may guide the development of additional treatments for osteosarcoma.

lncRNA-UCA1 in the diagnosis of bladder cancer: A meta-analysis

BACKGROUND

The main purpose of this study is to systematically evaluate the diagnostic value of long-chain non-coding RNA urothelial carcinoembryonic antigen 1 (lncRNA-UCA1) for bladder cancer, and to provide a scientific basis for the diagnosis of bladder cancer.

METHODS

By searching PubMed, Web of Science, EMBASE, CNKI, Wanfang, Weipu and other databases, in order to collect relevant literature of lncRNA-UCA1 for diagnosis of bladder cancer. The starting and ending time of the search is from the establishment of the database to December 31, 2019. Screen documents and extract data according to inclusion and exclusion criteria. QUADAS entry tool was used to evaluate the quality of literature. Meta-Disc 1.4 and Stata 12.0 software were used for statistical analysis, and UCA1 was combined for the statistics of bladder cancer diagnosis.

RESULTS

A total of 7 articles were included in this study, including 954 cases of bladder cancer patients and 482 cases of non-bladder cancer patients. The receiver operating characteristic curve (ROC) curve AUC of lncRNA-UCA1 used to diagnose bladder cancer was 0.86. The sensitivity was 0.83 (95% CI: 0.80-0.85), and the specificity was 0.86 (95% CI: 0.82-0.89). The positive likelihood ratio is 6.38 (95% CI: 3.01-13.55), and the negative likelihood ratio is 0.20 (95% CI: 0.13-0.31). The diagnostic odds ratio is 33.13 (95% CI: 11.16-98.33).

CONCLUSION

lncRNA-UCA1 has a high value of clinical auxiliary diagnosis for bladder cancer, and it can be further promoted and applied clinically.

Hypoxia-Induced Autophagy Enhances Cisplatin Resistance in Human Bladder Cancer Cells by Targeting Hypoxia-Inducible Factor-1α

Purpose

To investigate the effect of hypoxia on chemoresistance and the underlying mechanism in bladder cancer cells.

Methods

BIU-87 bladder cancer cell line was treated with cisplatin under hypoxic and normoxic conditions and tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blotting. All the data were expressed as mean ± standard error from three independent experiments and analyzed by multiple t-tests.

Results

Apoptosis of bladder cancer cells caused by cisplatin was attenuated in hypoxic conditions. Hypoxia enhanced autophagy caused by cisplatin. The autophagy inhibitor and HIF-1α inhibitor can reverse the chemoresistance in hypoxic condition. Apoptosis and autophagy of bladder cancer cells were downregulated by HIF-1α inhibitor YC-1. Hypoxia-induced autophagy enhanced chemoresistance to cisplatin via the HIF-1 signaling pathway.

Conclusion

Resistance to cisplatin in BIU-87 bladder cancer cells under hypoxic conditions can be explained by activation of autophagy, which is regulated by HIF-1α-associated signaling pathways. The hypoxia–autophagy pathway may be a target for improving the efficacy of cisplatin chemotherapy in bladder cancer.

HIF in Nephrotoxicity during Cisplatin Chemotherapy: Regulation, Function and Therapeutic Potential

Simple Summary

Cisplatin is a widely used chemotherapy drug, but its use and efficacy are limited by its nephrotoxicity. HIF has protective effects against kidney injury during cisplatin chemotherapy, but it may attenuate the anti-cancer effect of cisplatin. In this review, we describe the role and regulation of HIF in cisplatin-induced nephrotoxicity and highlight the therapeutic potential of targeting HIF in chemotherapy.

Abstract

Cisplatin is a highly effective, broad-spectrum chemotherapeutic drug, yet its clinical use and efficacy are limited by its side effects. Particularly, cancer patients receiving cisplatin chemotherapy have high incidence of kidney problems. Hypoxia-inducible factor (HIF) is the “master” transcription factor that is induced under hypoxia to trans-activate various genes for adaptation to the low oxygen condition. Numerous studies have reported that HIF activation protects against AKI and promotes kidney recovery in experimental models of cisplatin-induced acute kidney injury (AKI). In contrast, little is known about the effects of HIF on chronic kidney problems following cisplatin chemotherapy. Prolyl hydroxylase (PHD) inhibitors are potent HIF inducers that recently entered clinical use. By inducing HIF, PHD inhibitors may protect kidneys during cisplatin chemotherapy. However, HIF activation by PHD inhibitors may reduce the anti-cancer effect of cisplatin in tumors. Future studies should test PHD inhibitors in tumor-bearing animal models to verify their effects in kidneys and tumors.

DNA damage response and resistance of cancer stem cells

The cancer stem cell (CSC) model defines tumors as hierarchically organized entities, containing a small population of tumorigenic CSC, or tumour-initiating cells, placed at the apex of this hierarchy. These cells may share common qualities with chemo- and radio-resistant cancer cells and contribute to self-renewal activities resulting in tumour formation, maintenance, growth and metastasis. Yet, it remains obscure what self-defense mechanisms are utilized by these cells against the chemotherapeutic drugs or radiotherapy. Recently, attention has been focused on the pivotal role of the DNA damage response (DDR) in tumorigenesis. In line with this note, an increased DDR that prevents CSC and chemoresistant cells from genotoxic pressure of chemotherapeutic drugs or radiation may be responsible for cancer metastasis. In this review, we focus on the current knowledge concerning the role of DDR in CSC and resistant cancer cells and describe the existing opportunities of re-sensitizing such cells to modulate therapeutic treatment effects.

Competitive glucose metabolism as a target to boost bladder cancer immunotherapy

Bladder cancer - the tenth most frequent cancer worldwide - has a heterogeneous natural history and clinical behaviour. The predominant histological subtype, urothelial bladder carcinoma, is characterized by high recurrence rates, progression and both primary and acquired resistance to platinum-based therapy, which impose a considerable economic burden on health-care systems and have substantial effects on the quality of life and the overall outcomes of patients with bladder cancer. The incidence of urothelial tumours is increasing owing to population growth and ageing, so novel therapeutic options are vital. Based on work by The Cancer Genome Atlas project, which has identified targetable vulnerabilities in bladder cancer, immune checkpoint inhibitors (ICIs) have arisen as an effective alternative for managing advanced disease. However, although ICIs have shown durable responses in a subset of patients with bladder cancer, the overall response rate is only ~15-25%, which increases the demand for biomarkers of response and therapeutic strategies that can overcome resistance to ICIs. In ICI non-responders, cancer cells use effective mechanisms to evade immune cell antitumour activity; the overlapping Warburg effect machinery of cancer and immune cells is a putative determinant of the immunosuppressive phenotype in bladder cancer. This energetic interplay between tumour and immune cells leads to metabolic competition in the tumour ecosystem, limiting nutrient availability and leading to microenvironmental acidosis, which hinders immune cell function. Thus, molecular hallmarks of cancer cell metabolism are potential therapeutic targets, not only to eliminate malignant cells but also to boost the efficacy of immunotherapy. In this sense, integrating the targeting of tumour metabolism into immunotherapy design seems a rational approach to improve the therapeutic efficacy of ICIs.

Transcription factor Nrf2 induces the up-regulation of lncRNA TUG1 to promote progression and adriamycin resistance in urothelial carcinoma of the bladder

Background

Taurine-upregulated gene 1 (TUG1) has been documented to be implicated in carcinogenesis and chemoresistance in solid tumors. Here, we explored the biological role and regulatory mechanism of TUG1 in progression and chemoresistance of urothelial carcinoma of the bladder (UCB).

Methods

Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) mRNA and TUG1 expression was determined by quantitative reverse transcription polymerase chain reaction. Western blot was performed to determine the protein levels of Nrf2, p-glycoprotein (p-gp), Ki-67 (Ki67), matrix metalloproteinase (MMP)-2 and MMP-9 and cleaved caspase-3. The effects of either Nrf2 or TUG1 knockdown on the proliferation, invasion, apoptosis and adriamycin (ADM) resistance of UCB cells were evaluated by CCK-8 assay, transwell invasion assay and flow cytometry analysis. Xenograft tumor assay was carried out to confirm the role of Nrf2 and TUG1 in ADM resistance of UCB cells in vivo.

Results

Nrf2 and TUG1 were upregulated in UCB tissues and cell lines. A positive correlation between Nrf2 and TUG1 expression was discovered in UCB tissues. Moreover, Nrf2 and TUG1 expression levels were higher in ADM-resistant cells compared with those in parental cells. Furthermore, Nrf2 positively regulated the expression of TUG1 in UCB cells. Knockdown of either Nrf2 or TUG1 led to the inhibition of cell proliferation and invasion and promotion of cell apoptosis, accompanying with down-regulation of Ki67, MMP-2 and MMP-9 and up-regulation of cleaved caspase-3. Knockdown of either Nrf2 or TUG1 enhanced the sensitivity of BIU-87/ADM and T24/ADM cells to ADM, as indicated by decreased expression of p-gp. Besides, knockdown of either Nrf2 or TUG1 inhibited tumor growth in the absence or presence of ADM in vivo.

Conclusions

Nrf2 induces the up-regulation of TUG1 to promote progression and ADM resistance in UCB.

Co-Delivery of Metformin Enhances the Antimultidrug Resistant Tumor Effect of Doxorubicin by Improving Hypoxic Tumor Microenvironment

Doxorubicin (DOX) is a first-line chemo drug for cancer therapy, yet it fails to treat multi-drug-resistant tumors. Hypoxia is a major causative factor leading to chemotherapy failure. Particularly, hypoxia up-regulates its responsive transcription factor-hypoxia-inducible factors (HIF)-to induce the overexpression of drug resistant genes. Metformin (MET) is recently found to cooperate with DOX against multiple tumors. As a mitochondrial inhibitor, MET could suppress tumor oxygen consumption, and thereby modulate the hypoxic tumor microenvironment. In this study, we used cationic liposomes to codeliver both DOX and MET for treating multi-drug-resistant breast cancer cells-MCF7/ADR. Faster release of MET enhanced the cytotoxicity of DOX through attenuating hypoxic stress both in vivo and in vitro. MET diminished the cellular oxygen consumption and inhibited HIF1α and P-glycoprotein (Pgp) expression in vitro. In addition, the dual-drug-loaded liposomes increased tumor targeting and intratumoral blood oxygen saturation, which suggested that the tumor reoxygenation effect of MET facilitated the exertion of its synergistic activity with DOX against MCF7/ADR xenografts. In general, our study represents a feasible strategy to boost the therapeutic effect in treating multi-drug-resistant cancer by improving the hypoxic tumor microenvironment.

Digoxin sensitizes gemcitabine-resistant pancreatic cancer cells to gemcitabine via inhibiting Nrf2 signaling pathway

Chemoresistance is a major therapeutic obstacle in the treatment of human pancreatic ductal adenocarcinoma (PDAC). As an oxidative stress responsive transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the expression of cytoprotective genes. Nrf2 not only plays a critical role in chemoprevention, but also contributes to chemoresistance. In this study, we found that digoxin markedly reversed drug resistance of gemcitabine by inhibiting Nrf2 signaling in SW1990/Gem and Panc-1/Gem cells. Further research revealed that digoxin regulated Nrf2 at transcriptional level. In in vivo study, we found that digoxin and gemcitabine in combination inhibited tumor growth more substantially when compared with gemcitabine treatment alone in SW1990/Gem-shControl cells-derived xenografts. In the meantime, SW1990/Gem-shNrf2 cells-derived xenografts responded to gemcitabine and combination treatment similarly, suggesting that digoxin sensitized gemcitabine-resistant human pancreatic cancer to gemcitabine, which was Nrf2 dependent. These results demonstrated that digoxin might be used as a promising adjuvant sensitizer to reverse chemoresistance of gemcitabine-resistant pancreatic cancer to gemcitabine via inhibiting Nrf2 signaling.

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Digoxin could reverse drug resistance of gemcitabine in gemcitabine-resistant pancreatic cancer cells.

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Digoxin significantly inhibited Nrf2 signaling in gemcitabine-resistant pancreatic cancer cells.

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Digoxin-mediated reversing drug resistance of gemcitabine in gemcitabine-resistant pancreatic cancer cells was Nrf2 dependent.

HIF Inhibitors: Status of Current Clinical Development

PURPOSE OF REVIEW

In this review, the importance of the hypoxia inducible factor (HIF) pathway in tumorigenesis and cancer treatment outcomes will be discussed. The outcomes of phase II and III clinical trials of direct HIF inhibitors in the treatment of cancer will be reviewed.

RECENT FINDINGS

The HIF signaling pathway is activated by tumor-induced hypoxia or by inactivating mutations of the VHL gene. HIF is a transcription factor which regulates the expression of genes involved in adjusting mechanisms to hypoxia such as angiogenesis or apoptosis as well as tumor growth, invasion, and metastasis. The HIF pathway has a key role in development of resistance to different treatment modalities and higher expression of the HIF molecule is associated with poor prognosis. Clinical studies of the HIF inhibitors in patients with advanced/refractory cancers suggest benefit and warrant further studies of the HIF inhibitors either as a single agent or in combination with other therapeutic agents.

Hypoxia Mediates Tumor Malignancy and Therapy Resistance

Hypoxia is a hallmark of the tumor microenvironment and contributes to tumor malignant phenotypes. Hypoxia-inducible factor (HIF) is a master regulator of intratumoral hypoxia and controls hypoxia-mediated pathological processes in tumors, including angiogenesis, metabolic reprogramming, epigenetic reprogramming, immune evasion, pH homeostasis, cell migration/invasion, stem cell pluripotency, and therapy resistance. In this book chapter, we reviewed the causes and types of intratumoral hypoxia, hypoxia detection methods, and the oncogenic role of HIF in tumorigenesis and chemo- and radio-therapy resistance.

Millepachine showed novel antitumor effects in cisplatin-resistant human ovarian cancer through inhibiting drug efflux function of ATP-binding cassette transporters

Millepachine (MIL), a bioactive natural chalcone from Chinese herbal medicine Millettia pachycarpa Benth, exhibits strong antitumor effects against many human cancer cells both in vitro and in vivo. In this study, we found that MIL significantly inhibited the proliferation of cisplatin-resistant A2780CP cells via inducing obvious G2/M arrest and apoptosis and down-regulating the activity of topoisomerase II protein. We further found that the mechanism by which MIL showed good antitumor effects in cisplatin-resistant human ovarian cancer was associated with inhibiting the expression of ATP-binding cassette transporters in cisplatin-resistant A2780CP cells. Importantly, MIL did not only significantly inhibit the tumor growth in cisplatin-sensitive A2780S xenograft model, with an inhibitory rate of 73.21%, but also inhibited the tumor growth in the cisplatin-resistant A2780CP xenograft model, with an inhibitory rate of 65.68% (p < 0.001 vs. control; p < 0.001 vs. DDP). In addition, MIL did not induce acquired drug resistance in A2780S tumor-bearing mice with an inhibitory rate of 60.03%. The promising in vitro and in vivo performance indicated that MIL exhibited potential significance for drug research and development.

Pharmacogenomic considerations in the treatment of muscle-invasive bladder cancer

Recent advances in next-generation sequencing techniques have greatly improved our understanding of the genomic alterations in bladder cancer. Cisplatin-based chemotherapy provides a viable treatment option in the neoadjuvant, adjuvant and metastatic setting in a selected group of patients, but chemoresistance is a major problem. The underlying mechanisms of treatment resistance are poorly understood and elucidating these pathways will subsequently lead to improved patient selection, less unnecessary drug-related toxicity, improved patient outcome and decreased healthcare costs. This review provides an overview of mechanisms of chemoresistance and describes the current knowledge on how the genomic landscape influences therapy outcome in muscle-invasive bladder cancer patients.

Strange Bedfellows: Nuclear Factor, Erythroid 2-Like 2 (Nrf2) and Hypoxia-Inducible Factor 1 (HIF-1) in Tumor Hypoxia

The importance of the tumor microenvironment for cancer progression and therapeutic resistance is an emerging focus of cancer biology. Hypoxia, or low oxygen, is a hallmark of solid tumors that promotes metastasis and represents a significant obstacle to successful cancer therapy. In response to hypoxia, cancer cells activate a transcriptional program that allows them to survive and thrive in this harsh microenvironment. Hypoxia-inducible factor 1 (HIF-1) is considered the main effector of the cellular response to hypoxia, stimulating the transcription of genes involved in promoting angiogenesis and altering cellular metabolism. However, growing evidence suggests that the cellular response to hypoxia is much more complex, involving coordinated signaling through stress response pathways. One key signaling molecule that is activated in response to hypoxia is nuclear factor, erythroid 2 like-2 (Nrf2). Nrf2 is a transcription factor that controls the expression of antioxidant-response genes, allowing the cell to regulate reactive oxygen species. Nrf2 is also activated in various cancer types due to genetic and epigenetic alterations, and is associated with poor survival and resistance to therapy. Emerging evidence suggests that coordinated signaling through Nrf2 and HIF-1 is critical for tumor survival and progression. In this review, we discuss the distinct and overlapping roles of HIF-1 and Nrf2 in the cellular response to hypoxia, with a focus on how targeting Nrf2 could provide novel chemotherapeutic modalities for treating solid tumors.

Sphingosine Kinase-1 Involves the Inhibitory Action of HIF-1α by Chlorogenic Acid in Hypoxic DU145 Cells

Hypoxia enhances cancer development in a solid tumor. Hypoxia-inducible factor-1 α (HIF-1α) is a transcription factor that is dominantly expressed under hypoxia in solid tumor cells and is a key factor that regulates tumor. HIF-1α regulates several target genes involved in many aspects of cancer progression, including angiogenesis, metastasis, anti-apoptosis and cell proliferation as well as imparts resistance to cancer treatment. In this study, we assessed Crataegus Pinnatifida Bunge var. typical Schneider ethanol extract (CPE) for its anti-cancer effects in hypoxia-induced DU145 human prostate cancer cell line. CPE decreased the abundance of HIF-1α and sphingosine kinase-1 (SPHK-1) in hypoxia-induced prostate cancer DU145 cells. CPE decreased HIF-1α and SPHK-1 as well as SPHK-1 activity. Chlorogenic acid (CA) is one of four major compounds of CPE. Compared to CPE, CA significantly decreased the expression of HIF-1α and SPHK-1 as well as SPHK-1 activity in hypoxia-induced DU145 cells. Furthermore, CA decreased phosphorylation AKT and GSK-3β, which are associated with HIF-1α stabilization and affected SPHK-1 in a concentration-dependent manner. We confirmed the mechanism of CA-induced inhibition of HIF-1α by SPHK-1 signaling pathway using SPHK-1 siRNA and SPHK inhibitor (SKI). CA decreased the secretion and cellular expression of VEGF, thus inhibiting hypoxia-induced angiogenesis. Treatment of DU145cells with SPHK1 siRNA and CA for 48 h decreased cancer cell growth, and the inhibitory action of SPHK siRNA and CA on cell growth was confirmed by decrease in the abundance of Proliferating cell nuclear antigen (PCNA).

AEG-1 is associated with hypoxia-induced hepatocellular carcinoma chemoresistance via regulating PI3K/AKT/HIF-1alpha/MDR-1 pathway

Hypoxia is a common characteristic of hepatocellular carcinoma (HCC) associated with reduced response to chemotherapy, thus increasing the probability of tumor recurrence. Astrocyte elevated gene-1 (AEG-1) has been involved in a wide array of cancer progression including proliferation, chemoresistance, angiogenesis and metastasis, but its effect on HCC chemoresistance induced by hypoxia is unclear. In this study, expression of AEG-1 and multiple drug resistance (MDR-1) were examined in HCC using immunohistochemical staining and RT-PCR. Furthermore, their expression levels were detected in HCC HepG2 cells in normoxia or hypoxia via RT-PCR and Western blot assays. Specific shRNAs were used to silence AEG-1 expression in HepG2 cells. Results showed AEG-1 and MDR-1 expression were higher in HCC tissues than in adjacent normal tissues. Incubation of HepG2 cells in hypoxia increased expression of AEG-1 and MDR-1, compared to incubation in normoxia. Exposure to hypoxia blunted sensitivity of HepG2 cells to Adriamycin, 5-fluorouracil and cis-platinum, as evidenced by modest alterations in cell viability and apoptosis rate, however the sensitivity was elevated with AEG-1 knockdown. PI3K/AKT/HIF-1/MDR-1 pathway was attenuated following AEG-1 knockdown in hypoxia. Based on these data, it was suggested that AEG-1 is associated with hypoxia-induced hepatocellular carcinoma chemoresistance via regulating PI3K/AKT/HIF-1/MDR-1 pathway. This study uncovered a novel potential target for development of an effective therapy against hypoxia-induced HCC chemoresistance.