ABT737 reverses cisplatin resistance by targeting glucose metabolism of human ovarian cancer cells

ABT‑737 increases cisplatin sensitivity through the ROS‑ASK1‑JNK MAPK signaling axis in human ovarian cancer cisplatin‑resistant A2780/DDP cells

Ovarian cancer is a gynecological malignant tumor with the highest mortality rate, and chemotherapy resistance seriously affects patient therapeutic outcomes. It has been shown that the high expression of anti‑apoptotic proteins Bcl‑2 and Bcl‑xL is closely related to ovarian cancer chemotherapy resistance. Therefore, reducing Bcl‑2 and Bcl‑xL expression levels may be essential for reversing drug resistance in ovarian cancer. ABT‑737 is a BH3‑only protein mimetic, which can effectively inhibit the expression of the anti‑apoptotic proteins Bcl‑xL and Bcl‑2. Although it has been shown that ABT‑737 can increase the sensitivity of ovarian cancer cells to cisplatin, the specific molecular mechanism remains unclear and requires further investigation. In the present study, the results revealed that ABT‑737 can significantly increase the activation levels of JNK and ASK1 induced by cisplatin in A2780/DDP cells, which are cisplatin‑resistant ovarian cancer cells. Inhibition of the JNK and ASK1 pathway could significantly reduce cisplatin cytotoxicity increased by ABT‑737 in A2780/DDP cells, while inhibiting the ASK1 pathway could reduce JNK activation. In addition, it was further determined that ABT‑737 could increase reactive oxygen species (ROS) levels in A2780/DDP cells induced by cisplatin. Furthermore, the inhibition of ROS could significantly reduce JNK and ASK1 activation and ABT‑737‑mediated increased cisplatin cytotoxicity in A2780/DDP cells. Overall, the current data identified that activation of the ROS‑ASK1‑JNK signaling axis plays an essential role in the ability of ABT‑737 to increase cisplatin sensitivity in A2780/DDP cells. Therefore, upregulation the ROS‑ASK1‑JNK signaling axis is a potentially novel molecular mechanism by which ABT‑737 can enhance cisplatin sensitivity of ovarian cancer cells. In addition, the present research can also provide new therapeutic strategies and new therapeutic targets for patients with cisplatin‑resistant ovarian cancer with high Bcl‑2/Bcl‑xL expression patterns.

Glucose metabolism reprogramming in gynecologic malignant tumors

The incidence and mortality of gynecological tumors are progressively increasing due to factors such as obesity, viral infection, unhealthy habits, as well as social and economic pressures. Consequently, it has emerged as a significant threat to women's health. Numerous studies have revealed the remarkable metabolic activity of tumor cells in glycolysis and its ability to influence malignant biological behavior through specific mechanisms. Therefore, it is crucial for patients and gynecologists to comprehend the role of glycolytic proteins, regulatory molecules, and signaling pathways in tumorigenesis, progression, and treatment. This article aims to review the correlation between abnormal glucose metabolism and gynecologic tumors including cervical cancer (CC), endometrial carcinoma (EC), and ovarian cancer (OC). The findings from this research will provide valuable scientific insights for early screening, timely diagnosis and treatment interventions while also aiding in the prevention of recurrence among individuals with gynecological tumors.

CRABP2 affects chemotherapy resistance of ovarian cancer by regulating the expression of HIF1α

Ovarian cancer is the most lethal malignancy among gynecologic cancers, and primary and secondary chemotherapy resistance is one of the important reasons for poor prognosis of ovarian cancer patients. However, the specifics of resistance to chemotherapy in ovarian cancer remain unclear. Herein, we find that the expression level of cellular retinoic acid binding protein 2 (CRABP2) is up-regulated in drug-resistant ovarian cancer tissues and cell lines, and the expression levels of CRABP2 in epithelial ovarian cancer tissues are closely related to tumor clinical stage and patients' prognosis, suggesting that CRABP2 plays an important role in the progression of ovarian cancer and the corresponding ability of tumor to chemotherapy. With the in-depth study, we demonstrates that CRABP2 is related to the high metabolic activity in drug-resistant cells, and all-trans retinoic acid exacerbates this activity. Further molecular mechanism exploration experiments show that CRABP2 not only up-regulates the expression level of HIF1α, but also increases the localization of HIF1α in the nucleus. In drug-resistant ovarian cancer cells, knocking down HIF1α can block the resistance of CRABP2 to chemotherapy drugs in ovarian cancer cells. Taken together, our findings suggest for the first time that CRABP2 affects chemotherapy resistance of ovarian cancer by regulating the expression of HIF1α. This study provides a possible molecular mechanism for drug resistance and a possible molecular target for clinical treatment of ovarian cancer.

A feedback loop of PPP and PI3K/AKT signal pathway drives regorafenib-resistance in HCC

BACKGROUND

Hepatocellular carcinoma (HCC) is a principal type of liver cancer with high incidence and mortality rates. Regorafenib is a novel oral multikinase inhibitor for second-line therapy for advanced HCC. However, resistance to regorafenib is gradually becoming a dilemma for HCC and the mechanism remains unclear. In this study, we aimed to reveal the metabolic profiles of regorafenib-resistant cells and the key role and mechanism of the most relevant metabolic pathway in regorafenib resistance.

METHODS

Metabolomics was performed to detect the metabolic alteration between drug-sensitive and regorafenib-resistant cells. Colony formation assay, CCK-8 assay and flow cytometry were applied to observe cell colony formation, cell proliferation and apoptosis, respectively. The protein and mRNA levels were detected by western blot and RT-qPCR. Cell lines of Glucose-6-phosphate dehydrogenase(G6PD) knockdown in regorafenib-resistant cells or G6PD overexpression in HCC cell lines were stably established by lentivirus infection technique. G6PD activity, NADPH level, NADPH/NADP+ ratio, the ratio of ROS positive cells, GSH level, and GSH/GSSG ratio were detected to evaluate the anti-oxidative stress ability of cells. Phosphorylation levels of NADK were evaluated by immunoprecipitation.

RESULTS

Metabonomics analysis revealed that pentose phosphate pathway (PPP) was the most relevant metabolic pathway in regorafenib resistance in HCC. Compared with drug-sensitive cells, G6PD enzyme activity, NADPH level and NADPH/NADP+ ratio were increased in regorafenib-resistant cells, but the ratio of ROS positive cells and the apoptosis rate under the conditions of oxidative stress were decreased. Furthermore, G6PD suppression using shRNA or an inhibitor, sensitized regorafenib-resistant cells to regorafenib. In contrast, G6PD overexpression blunted the effects of regorafenib to drug-sensitive cells. Mechanistically, G6PD, the rate-limiting enzyme of PPP, regulated the PI3K/AKT activation. Furthermore, PI3K/AKT inhibition decreased G6PD protein expression, G6PD enzymatic activity and the capacity of PPP to anti-oxidative stress possibly by inhibited the expression and phosphorylation of NADK.

CONCLUSION

Taken together, a feedback loop of PPP and PI3K/AKT signal pathway drives regorafenib-resistance in HCC and targeting the feedback loop could be a promising approach to overcome drug resistance.

Rewiring of mitochondrial metabolism in therapy-resistant cancers: permanent and plastic adaptations

Deregulation of tumor cell metabolism is widely recognized as a "hallmark of cancer." Many of the selective pressures encountered by tumor cells, such as exposure to anticancer therapies, navigation of the metastatic cascade, and communication with the tumor microenvironment, can elicit further rewiring of tumor cell metabolism. Furthermore, phenotypic plasticity has been recently appreciated as an emerging "hallmark of cancer." Mitochondria are dynamic organelles and central hubs of metabolism whose roles in cancers have been a major focus of numerous studies. Importantly, therapeutic approaches targeting mitochondria are being developed. Interestingly, both plastic (i.e., reversible) and permanent (i.e., stable) metabolic adaptations have been observed following exposure to anticancer therapeutics. Understanding the plastic or permanent nature of these mechanisms is of crucial importance for devising the initiation, duration, and sequential nature of metabolism-targeting therapies. In this review, we compare permanent and plastic mitochondrial mechanisms driving therapy resistance. We also discuss experimental models of therapy-induced metabolic adaptation, therapeutic implications for targeting permanent and plastic metabolic states, and clinical implications of metabolic adaptations. While the plasticity of metabolic adaptations can make effective therapeutic treatment challenging, understanding the mechanisms behind these plastic phenotypes may lead to promising clinical interventions that will ultimately lead to better overall care for cancer patients.

Pan-cancer analysis reveals that G6PD is a prognostic biomarker and therapeutic target for a variety of cancers

Background

Despite accumulating evidence revealing that Glucose-6-phosphate dehydrogenase (G6PD) is highly expressed in many tumor tissues and plays a remarkable role in cancer tumorigenesis and progression, there is still a lack of G6PD pan-cancer analysis. This study was designed to analyze the expression status and prognostic significance of G6PD in pan-cancer.

Methods

G6PD expression data were obtained from multiple data resources including the Genotype-Tissue Expression, the Cancer Genome Atlas, and the Tumor Immunity Estimation Resource. These data were used to assess the G6PD expression, prognostic value, and clinical characteristics. The ESTIMATE algorithms were used to analyze the association between G6PD expression and immune-infiltrating cells and the tumor microenvironment. The functional enrichment analysis was also performed across pan-cancer. In addition, the GDSC1 database containing 403 drugs was utilized to explore the relationship between drug sensitivity and G6PD expression levels. Furthermore, we also performed clinical validation and in vitro experiments to further validate the role of G6PD in hepatocellular carcinoma (HCC) cells and its correlation with prognosis. The R software was used for statistical analysis and data visualization.

Results

G6PD expression was upregulated in most cancers compared to their normal counterparts. The study also revealed that G6PD expression was a prognostic indicator and high levels of G6PD expression were correlated with worse clinical prognosis including overall survival, disease-specific survival, and progression-free interval in multiple cancers. Furthermore, the G6PD level was also related to cancer immunity infiltration in most of the cancers, especially in KIRC, LGG, and LIHC. In addition to this, G6PD expression was positively related to pathological stages of KIRP, BRCA, KIRC, and LIHC. Functional analysis and protein-protein interactions network results revealed that G6PD was involved in metabolism-related activities, immune responses, proliferation, and apoptosis. Drug sensitivity analysis showed that IC50 values of most identified anti-cancer drugs were positively correlated with the G6PD expression. Notably, in vitro functional validation showed that G6PD knockdown attenuated the phenotypes of proliferation in HCC.

Conclusion

G6PD may serve as a potential prognostic biomarker for cancers and may be a potential therapeutic target gene for tumor therapy.

Glucose-6-phosphate dehydrogenase: a therapeutic target for ovarian cancer

INTRODUCTION

Ovarian cancer (OC) is a gynecological tumor disease, which is usually diagnosed at an advanced stage and has a poor prognosis. It has been established that the glucose metabolism rate of cancer cells is significantly higher than that of normal cells, and the pentose phosphate pathway (PPP) is an important branch pathway for glucose metabolism. Glucose-6-phosphate dehydrogenase (G6PD) is the key rate-limiting enzyme in the PPP, which plays an important role in the initiation and development of cancer (such as OC), and has been considered as a promisinganti-cancer target.

AREAS COVERED

In this review, based on the structure and biological function of G6PD, recent research on the roles of G6PD in the progression, metastasis, and chemoresistance of OC are summarized and accompanied by proposed molecular mechanisms, which may provide a systematic understanding of targeting G6PD for the treatment of patients with OC.

EXPERT OPINION

Accumulating evidence demonstrates that G6PD is a promising target of cancer. The development of G6PD inhibitors for cancer treatment merits broad application prospects.

PI3K/AKT/mTOR pathway, hypoxia, and glucose metabolism: Potential targets to overcome radioresistance in small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive tumor type for which limited therapeutic progress has been made. Platinum-based chemotherapy with or without thoracic radiotherapy remains the backbone of treatment, but most patients with SCLC acquire therapeutic resistance. Given the need for more effective therapies, better elucidation of the molecular pathogenesis of SCLC is imperative. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is frequently activated in SCLC and strongly associated with resistance to ionizing radiation in many solid tumors. This pathway is an important regulator of cancer cell glucose metabolism, and its activation probably effects radioresistance by influencing bioenergetic processes in SCLC. Glucose metabolism has three main branches-aerobic glycolysis, oxidative phosphorylation, and the pentose phosphate pathway-involved in radioresistance. The interaction between the PI3K/AKT/mTOR pathway and glucose metabolism is largely mediated by hypoxia-inducible factor 1 (HIF-1) signaling. The PI3K/AKT/mTOR pathway also influences glucose metabolism through other mechanisms to participate in radioresistance, including inhibiting the ubiquitination of rate-limiting enzymes of the pentose phosphate pathway. This review summarizes our understanding of links among the PI3K/AKT/mTOR pathway, hypoxia, and glucose metabolism in SCLC radioresistance and highlights promising research directions to promote cancer cell death and improve the clinical outcome of patients with this devastating disease.

Gene co-expression network analysis revealed novel biomarkers for ovarian cancer

Ovarian cancer is the second most common gynecologic cancer and remains the leading cause of death of all gynecologic oncologic disease. Therefore, understanding the molecular mechanisms underlying the disease, and the identification of effective and predictive biomarkers are invaluable for the development of diagnostic and treatment strategies. In the present study, a differential co-expression network analysis was performed via meta-analysis of three transcriptome datasets of serous ovarian adenocarcinoma to identify novel candidate biomarker signatures, i.e. genes and miRNAs. We identified 439 common differentially expressed genes (DEGs), and reconstructed differential co-expression networks using common DEGs and considering two conditions, i.e. healthy ovarian surface epithelia samples and serous ovarian adenocarcinoma epithelia samples. The modular analyses of the constructed networks indicated a co-expressed gene module consisting of 17 genes. A total of 11 biomarker candidates were determined through receiver operating characteristic (ROC) curves of gene expression of module genes, and miRNAs targeting these genes were identified. As a result, six genes (CDT1, CNIH4, CRLS1, LIMCH1, POC1A, and SNX13), and two miRNAs (mir-147a, and mir-103a-3p) were suggested as novel candidate prognostic biomarkers for ovarian cancer. Further experimental and clinical validation of the proposed biomarkers could help future development of potential diagnostic and therapeutic innovations in ovarian cancer.

Crucial Role of RLIP76 in Promoting Glycolysis and Tumorigenesis by Stabilization of HIF-1α in Glioma Cells Under Hypoxia

Hypoxia is intimately associated with enhanced glycolysis in gliomas, and hypoxia-inducible factor 1α (HIF-1α) plays a critical role in this process. RLIP76 (Ral-interacting protein 76) functions as a multifunctional mediator and is aberrantly expressed in various malignant tumors, including glioma. However, the underlying mechanism of RLIP76 and HIF-1α in glioma glycolysis remains largely unclear. In the present study, we demonstrated that RLIP76 is a hypoxia-inducible molecule that contributes to facilitating glycolysis in glioma cells under hypoxic conditions. In addition, hypoxia-induced RLIP76 is a novel target of HIF-1α and enhances the two important HIF-1α-target glycolytic proteins glucose transporter type 1 (GLUT1) and lactate dehydrogenase A (LDHA) in hypoxia. Mechanistically, RLIP76 can directly bind to HIF-1α in the nucleus and regulate the stability of HIF-1α by alleviating HIF-1α ubiquitination and therefore activates GLUT1 and LDHA to accelerate glycolysis in hypoxia. Furthermore, the enhanced glycolysis is necessary for the role of RLIP76 to promote glioma development in vivo, confirming the ability of RLIP76 to regulate tumor cell glycolysis. Collectively, our results demonstrate a previously unappreciated function of RLIP76 in hypoxia-mediated glycolytic metabolism and implicate that RLIP76 might be a valuable therapeutic target for gliomas.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

A Redoxable Mn Porphyrin, MnTnBuOE-2-PyP5+, Synergizes with Carboplatin in Treatment of Chemoresistant Ovarian Cell Line

We have employed a redox-active MnP (MnTnBuOE-2-PyP⁵⁺, Mn(III) meso-tetrakis (N-n-butoxyethylpyridinium-2-yl) porphyrin) frequently identified as superoxide dismutase mimic or BMX-001, to explore the redox status of normal ovarian cell in relation to two ovarian cancer cell lines: OV90 human serous ovarian cancer cell and chemotherapy-resistant OV90 cell (OVCD). We identified that OVCD cells are under oxidative stress due to high hydrogen peroxide (H₂O₂) levels and low glutathione peroxidase and thioredoxin 1. Furthermore, OVCD cells have increased glycolysis activity and mitochondrial respiration when compared to immortalized ovarian cells (hTER7) and parental cancer cells (OV90). Our goal was to study how ovarian cell growth depends upon the redox state of the cell; hence, we used MnP (BMX-001), a redox-active MnSOD mimetic, as a molecular tool to alter ovarian cancer redox state. Interestingly, OVCD cells preferentially uptake MnP relative to OV90 cells which led to increased inhibition of cell growth, glycolytic activity, OXPHOS, and ATP, in OVCD cells. These effects were further increased when MnP was combined with carboplatin. The effects were discussed with regard to the elevation in H₂O₂ levels, increased oxidative stress, and reduced Nrf2 levels and its downstream targets when cells were exposed to either MnP or MnP/carboplatin. It is significant to emphasize that MnP protects normal ovarian cell line, hTER7, against carboplatin toxicity. Our data demonstrate that the addition of MnP-based redox-active drugs may be used (via increasing excessively the oxidative stress of serous ovarian cancer cells) to improve cancer patients' chemotherapy outcomes, which develop resistance to platinum-based drugs.

Mitochondrial Dysfunction Pathway Alterations Offer Potential Biomarkers and Therapeutic Targets for Ovarian Cancer

The mitochondrion is a very versatile organelle that participates in some important cancer-associated biological processes, including energy metabolism, oxidative stress, mitochondrial DNA (mtDNA) mutation, cell apoptosis, mitochondria-nuclear communication, dynamics, autophagy, calcium overload, immunity, and drug resistance in ovarian cancer. Multiomics studies have found that mitochondrial dysfunction, oxidative stress, and apoptosis signaling pathways act in human ovarian cancer, which demonstrates that mitochondria play critical roles in ovarian cancer. Many molecular targeted drugs have been developed against mitochondrial dysfunction pathways in ovarian cancer, including olive leaf extract, nilotinib, salinomycin, Sambucus nigra agglutinin, tigecycline, and eupatilin. This review article focuses on the underlying biological roles of mitochondrial dysfunction in ovarian cancer progression based on omics data, potential molecular relationship between mitochondrial dysfunction and oxidative stress, and future perspectives of promising biomarkers and therapeutic targets based on the mitochondrial dysfunction pathway for ovarian cancer.

Enhanced Intracellular Reactive Oxygen Species by Photodynamic Therapy Effectively Promotes Chemoresistant Cell Death

Anti-cancer chemo-drugs can cause a rapid elevation of intracellular reactive oxygen species (ROS) levels. An imbalance in ROS production and elimination systems leads to cancer cell resistance to chemotherapy. This study aimed to evaluate the mechanism and effect of ROS on multidrug resistance in various human chemoresistant cancer cells by detecting the changes in the amount of ROS, the expression of ROS-related and glycolysis-related genes, and cell death. We found that ROS was decreased while oxidative phosphorylation was increased in chemoresistant cells. We verified that the chemoresistance of cancer cells was achieved in two ways. First, chemoresistant cells preferred oxidative phosphorylation instead of anaerobic glycolysis for energy generation, which increased ATPase activity and produced much more ATP to provide energy. Second, ROS-scavenging systems were enhanced in chemoresistant cancer cells, which in turn decreased ROS amount and thus inhibited chemo-induced cell death. Our in vitro and in vivo photodynamic therapy further demonstrated that elevated ROS production efficiently inhibited chemo-drug resistance and promoted chemoresistant cell death. Taken together, targeting ROS systems has a great potential to treat cancer patients with chemoresistance.

Metabolic profiling of prostate cancer in skeletal microenvironments identifies G6PD as a key mediator of growth and survival

The spread of cancer to bone is invariably fatal, with complex cross-talk between tumor cells and the bone microenvironment responsible for driving disease progression. By combining in silico analysis of patient datasets with metabolomic profiling of prostate cancer cells cultured with bone cells, we demonstrate the changing energy requirements of prostate cancer cells in the bone microenvironment, identifying the pentose phosphate pathway (PPP) as elevated in prostate cancer bone metastasis, with increased expression of the PPP rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD) associated with a reduction in progression-free survival. Genetic and pharmacologic manipulation demonstrates that G6PD inhibition reduces prostate cancer growth and migration, associated with changes in cellular redox state and increased chemosensitivity. Genetic blockade of G6PD in vivo results in reduction of tumor growth within bone. In summary, we demonstrate the metabolic plasticity of prostate cancer cells in the bone microenvironment, identifying the PPP and G6PD as metabolic targets for the treatment of prostate cancer bone metastasis.

Revisiting therapeutic strategies for ovarian cancer by focusing on redox homeostasis

Recent advances in molecular genetics have expanded our understanding of ovarian cancer. High levels of reactive oxygen species (ROS) and upregulation of antioxidant genes are common characteristic features of human cancers. This review reconsiders novel therapeutic strategies for ovarian cancer by focusing on redox homeostasis. A literature search was performed for preclinical and clinical studies published between January 1998 and October 2021 in the PubMed database using a combination of specific terms. ROS serves a central role in tumor suppression and progression by inducing DNA damage and mutations, genomic instability, and aberrant anti- and pro-tumorigenic signaling. Cancer cells increase their antioxidant capacity to neutralize the extra ROS. Additionally, antioxidants, such as CD44 variant isoform 9 (CD44v9) and nuclear factor erythroid 2-related factor 2 (Nrf2), mediate redox homeostasis in ovarian cancer. Furthermore, studies conducted on different cancer types revealed the dual role of antioxidants in tumor progression and inhibition. However, in animal models, genetic loss of antioxidant capacity in the host cannot block cancer initiation and progression. Host-derived antioxidant systems are essential to suppress carcinogenesis, suggesting that antioxidants serve a pivotal role in suppressing cancer development. By contrast, antioxidant activation in cancer cells confers aggressive phenotypes. Antioxidant inhibitors can promote cancer cell death by enhancing ROS levels. Concurrent inhibition of CD44v9 and Nrf2 may trigger apoptosis induction, potentiate chemosensitivity and enhance antitumor activities through the ROS-activated p38/p21 pathway. Antioxidants may have tumor-promoting and -suppressive functions. Therefore, an improved understanding of the role of antioxidants in redox homeostasis and developing antioxidant-specific inhibitors is necessary for treating ovarian cancer.

Metabolic reprogramming in epithelial ovarian cancer

Cancer cells usually show adaptations to their metabolism that facilitate their growth, invasiveness, and metastasis. Therefore, reprogramming the energy metabolism is one of the current key foci of cancer research and treatment. Although aerobic glycolysis-the Warburg effect-has been thought to be the dominant energy metabolism in cancer, recent data indicate a different possibility, specifically that oxidative phosphorylation (OXPHOS) is the more likely form of energy metabolism in some cancer cells. Due to the heterogeneity of epithelial ovarian cancer, there are different metabolic preferences among cell types, study types (in vivo/in vitro), and invasiveness. Current knowledge acknowledges glycolysis to be the main energy provider in ovarian cancer growth, invasion, migration, and viability, so specific agents targeting the glycolysis or OXPHOS pathways have been used in previous studies to attenuate tumor progression and increase chemosensitization. However, chemoresistant cell lines exert various metabolic preferences. This review comprehensively summarizes the information from existing reports which could together provide an in-depth understanding and insights for the development of a novel targeted therapy which can be used as an adjunctive treatment to standard chemotherapy to decelerate tumor progression and decrease the epithelial ovarian cancer mortality rate.

The Role of Tumour Metabolism in Cisplatin Resistance

Cisplatin is a chemotherapy drug commonly used in cancer treatment. Tumour cells are more sensitive to cisplatin than normal cells. Cisplatin exerts an antitumour effect by interfering with DNA replication and transcription processes. However, the drug-resistance properties of tumour cells often cause loss of cisplatin efficacy and failure of chemotherapy, leading to tumour progression. Owing to the large amounts of energy and compounds required by tumour cells, metabolic reprogramming plays an important part in the occurrence and development of tumours. The interplay between DNA damage repair and metabolism also has an effect on cisplatin resistance; the molecular changes to glucose metabolism, amino acid metabolism, lipid metabolism, and other metabolic pathways affect the cisplatin resistance of tumour cells. Here, we review the mechanism of action of cisplatin, the mechanism of resistance to cisplatin, the role of metabolic remodelling in tumorigenesis and development, and the effects of common metabolic pathways on cisplatin resistance.

Elucidating Role of Reactive Oxygen Species (ROS) in Cisplatin Chemotherapy: A Focus on Molecular Pathways and Possible Therapeutic Strategies

The failure of chemotherapy is a major challenge nowadays, and in order to ensure effective treatment of cancer patients, it is of great importance to reveal the molecular pathways and mechanisms involved in chemoresistance. Cisplatin (CP) is a platinum-containing drug with anti-tumor activity against different cancers in both pre-clinical and clinical studies. However, drug resistance has restricted its potential in the treatment of cancer patients. CP can promote levels of free radicals, particularly reactive oxygen species (ROS) to induce cell death. Due to the double-edged sword role of ROS in cancer as a pro-survival or pro-death mechanism, ROS can result in CP resistance. In the present review, association of ROS with CP sensitivity/resistance is discussed, and in particular, how molecular pathways, both upstream and downstream targets, can affect the response of cancer cells to CP chemotherapy. Furthermore, anti-tumor compounds, such as curcumin, emodin, chloroquine that regulate ROS and related molecular pathways in increasing CP sensitivity are described. Nanoparticles can provide co-delivery of CP with anti-tumor agents and by mediating photodynamic therapy, and induce ROS overgeneration to trigger CP sensitivity. Genetic tools, such as small interfering RNA (siRNA) can down-regulate molecular pathways such as HIF-1α and Nrf2 to promote ROS levels, leading to CP sensitivity. Considering the relationship between ROS and CP chemotherapy, and translating these findings to clinic can pave the way for effective treatment of cancer patients.

Mitocans Revisited: Mitochondrial Targeting as Efficient Anti-Cancer Therapy

Mitochondria are essential cellular organelles, controlling multiple signalling pathways critical for cell survival and cell death. Increasing evidence suggests that mitochondrial metabolism and functions are indispensable in tumorigenesis and cancer progression, rendering mitochondria and mitochondrial functions as plausible targets for anti-cancer therapeutics. In this review, we summarised the major strategies of selective targeting of mitochondria and their functions to combat cancer, including targeting mitochondrial metabolism, the electron transport chain and tricarboxylic acid cycle, mitochondrial redox signalling pathways, and ROS homeostasis. We highlight that delivering anti-cancer drugs into mitochondria exhibits enormous potential for future cancer therapeutic strategies, with a great advantage of potentially overcoming drug resistance. Mitocans, exemplified by mitochondrially targeted vitamin E succinate and tamoxifen (MitoTam), selectively target cancer cell mitochondria and efficiently kill multiple types of cancer cells by disrupting mitochondrial function, with MitoTam currently undergoing a clinical trial.

Bcl‑2 family: Novel insight into individualized therapy for ovarian cancer (Review)

Chemoresistance to platinum‑based chemotherapy for ovarian cancer in the advanced stage remains a formidable concern clinically. Increasing evidence has revealed that apoptosis represents the terminal events of the anti‑tumor mechanisms of a number of chemical drugs and has a close association with chemoresistance in ovarian cancer. The B‑cell lymphoma‑2 (Bcl‑2) family plays a crucial role in apoptosis and has a close association with chemoresistance in ovarian cancer. Some drugs that target Bcl‑2 family members have shown efficacy in overcoming the chemoresistance of ovarian cancer. A BH3 profiling assay was found to be able to predict how primed a cell is when treated with antitumor drugs. The present review summarizes the role of the Bcl‑2 family in mediating cell death in response to antitumor drugs and novel drugs that target Bcl‑2 family members. The application of the new functional assay, BH3 profiling, is also discussed herein. Furthermore, the present review presents the hypothesis that targeting Bcl‑2 family members may prove to be helpful for the individualized therapy of ovarian cancer in clinical practice and in laboratory research.

Ilimaquinone Induces Apoptosis and Autophagy in Human Oral Squamous Cell Carcinoma Cells

In this study, the anti-tumor activity of ilimaquinone (IQ), a sesquiterpene quinone isolated from marine sponge Halichondria sp., in oral squamous cell carcinoma (OSCC) cells, was investigated. IQ suppressed the viability of the OSCC cell lines SCC4 and SCC2095 with IC₅₀ values of 7.5 and 8.5 μM, respectively. Flow cytometric analysis demonstrated that IQ induced caspase-dependent apoptosis in SCC4 cells and modulated the expression of several cell growth-related gene products, including Akt, p38, Mcl-1, and p53. Notably, p53 knockdown caused higher resistance to IQ’s anti-tumor activity. In addition, IQ increased reactive oxygen species generation, which was partially reversed by the addition of antioxidants. Furthermore, it triggered autophagy, as evidenced by acidic organelle formation and LC3B-II and Atg5 expression in SCC4 cells. Pretreatment with the autophagy inhibitor 3-methyladenine or chloroquine partially decreased IQ-induced apoptosis, suggesting that IQ induced protective autophagy. In summary, IQ has potential to be used in OSCC therapy.

Long-Term Glucose Restriction with or without β-Hydroxybutyrate Enrichment Distinctively Alters Epithelial-Mesenchymal Transition-Related Signalings in Ovarian Cancer Cells

The beneficial impacts of the ketogenic diet and metabolic reprograming were recently reported for ovarian cancer patients. In this study, the effects of glucose restriction with or without beta-hydroxybutyrate (bHB) enrichment were studied in drug-resistant CD133high A2780CP and CD133low SK-OV-3 ovarian cancer cells to scrutinize the impact of experimental ketosis on ATP production, epithelial to mesenchymal transition (EMT), and related signaling pathways including Wnt, Hippo, and Hedgehog. Cells were adapted and maintained for a month with restricted levels of glucose (250 mg/l) with or without the therapeutic concentration of bHB (5 mM). Quantitative PCR, Western blot analysis, flow cytometry, chemiluminescence, and wound healing assay were used in this study. Glucose restriction and bHB enrichment reduced the stemness marker and diminished In Vitro migration in both cell lines. Glucose restriction significantly reduced ATP levels in both cells, but bHB enrichment was partially compensated for the ATP levels solely in SK-OV-3 cells. Glucose restriction mainly inhibited the Wnt pathway in the CD133high A2780CP cells, but the Hedgehog pathway was the main target in CD133low SK-OV-3 cells. In Conclusion, Prior targeted evaluations of key genes' expression would help to predict the distinctive impacts of metabolic fuels and to optimize the efficacy of ketogenic diets.

The identification of six risk genes for ovarian cancer platinum response based on global network algorithm and verification analysis

Ovarian cancer is the most lethal gynaecological cancer, and resistance of platinum‐based chemotherapy is the main reason for treatment failure. The aim of the present study was to identify candidate genes involved in ovarian cancer platinum response by analysing genes from homologous recombination and Fanconi anaemia pathways. Associations between these two functional genes were explored in the study, and we performed a random walk algorithm based on reconstructed gene‐gene network, including protein‐protein interaction and co‐expression relations. Following the random walk, all genes were ranked and GSEA analysis showed that the biological functions focused primarily on autophagy, histone modification and gluconeogenesis. Based on three types of seed nodes, the top two genes were utilized as examples. We selected a total of six candidate genes (FANCA, FANCG, POLD1, KDM1A, BLM and BRCA1) for subsequent verification. The validation results of the six candidate genes have significance in three independent ovarian cancer data sets with platinum‐resistant and platinum‐sensitive information. To explore the correlation between biomarkers and clinical prognostic factors, we performed differential analysis and multivariate clinical subgroup analysis for six candidate genes at both mRNA and protein levels. And each of the six candidate genes and their neighbouring genes with a mutation rate greater than 10% were also analysed by network construction and functional enrichment analysis. In the meanwhile, the survival analysis for platinum‐treated patients was performed in the current study. Finally, the RT‐qPCR assay was used to determine the performance of candidate genes in ovarian cancer platinum response. Taken together, this research demonstrated that comprehensive bioinformatics methods could help to understand the molecular mechanism of platinum response and provide new strategies for overcoming platinum resistance in ovarian cancer treatment.

Inhibition of pyruvate dehydrogenase kinase‑1 by dicoumarol enhances the sensitivity of hepatocellular carcinoma cells to oxaliplatin via metabolic reprogramming

The Warburg effect is a unique metabolic feature of the majority of tumor cells and is closely related to chemotherapeutic resistance. Pyruvate dehydrogenase kinase 1 (PDK1) is considered a 'switch' that controls the fate of pyruvate in glucose metabolism. However, to date, to the best of our knowledge, there are only a few studies to available which had studied the reduction of chemotherapeutic resistance via the metabolic reprogramming of tumor cells with PDK1 as a target. In the present study, it was found dicoumarol (DIC) reduced the phosphorylation of pyruvate dehydrogenase (PDH) by inhibiting the activity of PDK1, which converted the metabolism of human hepatocellular carcinoma (HCC) cells to oxidative phosphorylation, leading to an increase in mitochondrial reactive oxygen species ROS (mtROS) and a decrease in mitochondrial membrane potential (MMP), thereby increasing the apoptosis induced by oxaliplatin (OXA). Furthermore, the present study elucidated that the targeting of PDK1 may be a potential strategy for targeting metabolism in the chemotherapy of HCC. In addition, DIC as an 'old drug' exhibits novel efficacy, bringing new hope for antitumor therapy.

Apigenin induces apoptosis and counteracts cisplatin-induced chemoresistance via Mcl-1 in ovarian cancer cells

Ovarian cancer (OC) is one of the prominent causes of mortality in female patients diagnosed with gynecologic malignancies. While it has previously been demonstrated that apigenin inhibits cell growth in colon and breast cancer cells, the effect of apigenin in OC cells is not fully understood. Therefore, the aim of the present study was to investigate the impact of apigenin on cell death and resistance to cisplatin in OC cells. It was found that apigenin inhibited proliferation, hindered cell cycle progression and promoted SKOV3 cell apoptosis. Moreover, these effects were also observed in cisplatin-resistant SKOV3/DDP cells. Furthermore, apigenin reduced the mitochondrial transmembrane potential, and elevated the ratios of cleaved caspase-3/caspase-3 and Bax/Bcl-2 in the two cell types. Reverse transcription-quantitative PCR and western blotting results demonstrated that apigenin significantly downregulated Mcl-1 at the transcriptional and translational levels in SKOV3 and SKOV3/DDP cells, which was responsible for its cytotoxic functions and chemosensitizing effects. Collectively, the present results identified the impact of apigenin on OC cell death and resistance to cisplatin, and the potential molecular mechanisms. However, additional studies are required to further elucidate the underlying mechanisms.

Phosphoproteomics Reveals Key Regulatory Kinases and Modulated Pathways Associated with Ovarian Cancer Tumors

Background

Ovarian cancer (OC) is the seventh most common cancer worldwide for women. However, there are no sufficient diagnostic methods and few treatment options available due to poor understanding of its pathogenic mechanisms.

Methods

To comprehensively analyze the phosphoproteomic characterization for OC, we took advantage of a quantitative global phosphoproteomics method, titanium(IV) immobilized metal affinity chromatography (Ti⁴⁺-IMAC) coupled to nanoscale liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (nanoLC/Q-TOF-MS/MS) on ovarian tissue samples obtained from five OC patients and five matched controls.

Results

A total of 722 phosphorylated sites corresponding to 534 proteins were significantly different (fold change ≥ 2, p < 0.01) between OC patients and the controls. Among them, 83 transcription factors mainly consisted of transcription cofactors, zf-C2H2, and chromatin remodeling factors and 29 kinases were included. Further functional analysis suggested significantly biological processes were highly enriched and involved in the pathogenesis of OC, especially fructose and mannose metabolism. Moreover, the regulatory roles of modulated pathways, including MAPK, ErbB, and GnRH signaling pathways were also identified as critical processes involved in OC. The results here highlighted key phosphorylated proteins, particularly kinases, and the corresponding cancer-related metabolic and signal pathways that played important roles in the development of OC. Additionally, the expression levels of two kinases, phosphorylated CDK (T14) and phosphorylated PRKCQ (S695), were validated by Western blot analysis in the other group of ovarian tissue samples.

Conclusion

Altogether, our data not only provided novel insights into the potential biomarkers and therapy options for OC but also extended our knowledge on its pathophysiological mechanism.

DGKA Provides Platinum Resistance in Ovarian Cancer Through Activation of c-JUN-WEE1 Signaling

PURPOSE

Although platinum compounds are the first-line treatment for ovarian cancer, the majority of patients relapse and develop resistance to treatment. However, the mechanism underlying resistance is unclear. The goal of our study is to decipher the mechanism by which a metabolic kinase, diacylglycerol kinase alpha (DGKA), confers platinum resistance in ovarian cancer.

EXPERIMENTAL DESIGN

Metabolic kinase RNAi synthetic lethal screening was used to identify a cisplatin resistance driver in ovarian cancer. DGKA variants were used to demonstrate the need for DGKA activity in cisplatin resistance. Phospho-proteomic and genomic screens were performed to identify downstream effectors of DGKA. Therapeutic efficacy of targeting DGKA was confirmed and clinical relevance of DGKA signaling was validated using ovarian cancer patient-derived tumors that had different responses to platinum-based therapy.

RESULTS

We found that platinum resistance was mediated by DGKA and its product, phosphatidic acid (PA), in ovarian cancer. Proteomic and genomic screens revealed that DGKA activates the transcription factor c-JUN and consequently enhances expression of a cell-cycle regulator, WEE1. Mechanistically, PA facilitates c-JUN N-terminal kinase recruitment to c-JUN and its nuclear localization, leading to c-JUN activation upon cisplatin exposure. Pharmacologic inhibition of DGKA sensitized ovarian cancer cells to cisplatin treatment and DGKA-c-JUN-WEE1 signaling positively correlated with platinum resistance in tumors derived from patients with ovarian cancer.

CONCLUSIONS

Our study demonstrates how the DGKA-derived lipid messenger, PA, contributes to cisplatin resistance by intertwining with kinase and transcription networks, and provides preclinical evidence for targeting DGKA as a new strategy in ovarian cancer treatment to battle cisplatin resistance.

The Drug-Resistance Mechanisms of Five Platinum-Based Antitumor Agents

Platinum-based anticancer drugs, including cisplatin, carboplatin, oxaliplatin, nedaplatin, and lobaplatin, are heavily applied in chemotherapy regimens. However, the intrinsic or acquired resistance severely limit the clinical application of platinum-based treatment. The underlying mechanisms are incredibly complicated. Multiple transporters participate in the active transport of platinum-based antitumor agents, and the altered expression level, localization, or activity may severely decrease the cellular platinum accumulation. Detoxification components, which are commonly increasing in resistant tumor cells, can efficiently bind to platinum agents and prevent the formation of platinum–DNA adducts, but the adducts production is the determinant step for the cytotoxicity of platinum-based antitumor agents. Even if adequate adducts have formed, tumor cells still manage to survive through increased DNA repair processes or elevated apoptosis threshold. In addition, autophagy has a profound influence on platinum resistance. This review summarizes the critical participators of platinum resistance mechanisms mentioned above and highlights the most potential therapeutic targets or predicted markers. With a deeper understanding of the underlying resistance mechanisms, new solutions would be produced to extend the clinical application of platinum-based antitumor agents largely.

The Pentose Phosphate Pathway and Its Involvement in Cisplatin Resistance

Cisplatin is the first-line treatment for different types of solid tumors, such as ovarian, testicular, bladder, cervical, head and neck, lung, and esophageal cancers. The main problem related to its clinical use is the onset of drug resistance. In the last decades, among the studied molecular mechanisms of cisplatin resistance, metabolic reprogramming has emerged as a possible one. This review focuses on the pentose phosphate pathway (PPP) playing a pivotal role in maintaining the high cell proliferation rate and representing an advantage for cancer cells. In particular, the oxidative branch of PPP plays a role in oxidative stress and seems to be involved in cisplatin resistance. In light of these considerations, it has been demonstrated that overexpression and higher enzymatic activity of different enzymes of both oxidative and non-oxidative branches (such as glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and transketolase) increase cisplatin resistance, and their silencing or combined treatment with cisplatin could restore cisplatin sensitivity. Moreover, drug delivery systems loaded with both PPP inhibitors and cisplatin give the possibility of reaching cancer cells selectively. In conclusion, targeting PPP is becoming a strategy to overcome cisplatin resistance; however, further studies are required to better understand the mechanisms.

Metabolic Symbiosis in Chemoresistance: Refocusing the Role of Aerobic Glycolysis

Cellular metabolic reprogramming is now recognized as a hallmark of tumors. Altered tumor metabolism determines the malignant biological behaviors and phenotypes of cancer. More recently, studies have begun to reveal that cancer cells generally exhibit increased glycolysis or oxidative phosphorylation (OXPHOS) for Adenosine Triphosphate(ATP)generation, which is frequently associated with drug resistance. The metabolism of drug-resistant cells is regulated by the PI3K/AKT/mTOR pathway which ultimately confer cancer cells drug resistance phenotype. The key enzymes involved in glycolysis and the key molecules in relevant pathways have been used as targets to reverse drug resistance. In this review, we highlight our current understanding of the role of metabolic symbiosis in therapeutic resistance and discuss the ongoing effort to develop metabolic inhibitors as anti-cancer drugs to overcome drug resistance to classical chemotherapy.

The TGFβ1-FOXM1-HMGA1-TGFβ1 positive feedback loop increases the cisplatin resistance of non-small cell lung cancer by inducing G6PD expression

Platinum-based chemotherapy is still widely applied for the treatment of advanced non-small cell lung cancer (NSCLC). However, acquired chemoresistance compromises the curative effect of this drug. In this study, we found that glucose-6-phosphate dehydrogenase (G6PD), a critical enzyme of the pentose phosphate pathway, contributed to cisplatin resistance in NSCLC. The experimental results showed that transforming growth factor beta 1 (TGFβ1) increased the expression of G6PD by activating the forkhead box protein M1-high mobility group AT-hook 1-G6PD (FOXM1-HMGA1-G6PD) transcriptional regulatory pathway, in which TGFβ1 inhibited the ubiquitination and degradation of FOXM1 protein. Additionally, HMGA1 induced TGFβ1 expression, and neutralized TGFβ1 in the culture medium downregulated HMGA1 levels, suggesting the existence of a TGFβ1-FOXM1-HMGA1-TGFβ1 positive feedback loop and its role in maintaining G6PD expression. Further investigations showed that exogenous TGFβ1 enhanced the cisplatin resistance of NSCLC cells, while disrupting the FOXM1-HMGA1-G6PD pathway, thereby sensitizing the cells to cisplatin. Consistently, the TGFβ1-FOXM1-HMGA1-G6PD axis was confirmed in NSCLC tissues, and overactivation of this axis predicted poor survival in NSCLC patients. Collectively, the results of this study demonstrate that the TGFβ1-FOXM1-HMGA1-TGFβ1 positive feedback loop plays a crucial role in the cisplatin resistance of NSCLC by upregulating the expression of G6PD, providing a potential therapeutic target to restore chemosensitivity in cisplatin-resistant NSCLC.

Mitochondrial determinants of chemoresistance

Chemoresistance constitute nowadays the major contributor to therapy failure in most cancers. There are main factors that mitigate cell response to therapy, such as target organ, inherent sensitivity to the administered compound, its metabolism, drug efflux and influx or alterations on specific cellular targets, among others. We now know that intrinsic properties of cancer cells, including metabolic features, substantially contribute to chemoresistance. In fact, during the last years, numerous reports indicate that cancer cells resistant to chemotherapy demonstrate significant alterations in mitochondrial metabolism, membrane polarization and mass. Metabolic activity and expression of several mitochondrial proteins are modulated under treatment to cope with stress, making these organelles central players in the development of resistance to therapies. Here, we review the role of mitochondria in chemoresistant cells in terms of metabolic rewiring and function of key mitochondria-related proteins.

Characterisation of an Isogenic Model of Cisplatin Resistance in Oesophageal Adenocarcinoma Cells

Cisplatin (cis-diamminedichloroplatinum) is widely used for the treatment of solid malignancies; however, the development of chemoresistance hinders the success of this chemotherapeutic in the clinic. This study provides novel insights into the molecular and phenotypic changes in an isogenic oesophageal adenocarcinoma (OAC) model of acquired cisplatin resistance. Key differences that could be targeted to overcome cisplatin resistance are highlighted. We characterise the differences in treatment sensitivity, gene expression, inflammatory protein secretions, and metabolic rate in an isogenic cell culture model of acquired cisplatin resistance in OAC. Cisplatin-resistant cells (OE33 Cis R) were significantly more sensitive to other cytotoxic modalities, such as 2 Gy radiation (p = 0.0055) and 5-fluorouracil (5-FU) (p = 0.0032) treatment than parental cisplatin-sensitive cells (OE33 Cis P). Gene expression profiling identified differences at the gene level between cisplatin-sensitive and cisplatin-resistant cells, uncovering 692 genes that were significantly altered between OE33 Cis R cells and OE33 Cis P cells. OAC is an inflammatory-driven cancer, and inflammatory secretome profiling identified 18 proteins secreted at significantly altered levels in OE33 Cis R cells compared to OE33 Cis P cells. IL-7 was the only cytokine to be secreted at a significantly higher levels from OE33 Cis R cells compared to OE33 Cis P cells. Additionally, we profiled the metabolic phenotype of OE33 Cis P and OE33 Cis R cells under normoxic and hypoxic conditions. The oxygen consumption rate, as a measure of oxidative phosphorylation, is significantly higher in OE33 Cis R cells under normoxic conditions. In contrast, under hypoxic conditions of 0.5% O₂, the oxygen consumption rate is significantly lower in OE33 Cis R cells than OE33 Cis P cells. This study provides novel insights into the molecular and phenotypic changes in an isogenic OAC model of acquired cisplatin resistance, and highlights therapeutic targets to overcome cisplatin resistance in OAC.

Iron granules in plasma cells

Resistance of cancer cells to chemotherapy is the first cause of cancer-associated death. Thus, new strategies to deal with the evasion of drug response and to improve clinical outcomes are needed. Genetic and epigenetic mechanisms associated with uncontrolled cell growth result in metabolism reprogramming. Cancer cells enhance anabolic pathways and acquire the ability to use different carbon sources besides glucose. An oxygen and nutrient-poor tumor microenvironment determines metabolic interactions among normal cells, cancer cells and the immune system giving rise to metabolically heterogeneous tumors which will partially respond to metabolic therapy. Here we go into the best-known cancer metabolic profiles and discuss several studies that reported tumors sensitization to chemotherapy by modulating metabolic pathways. Uncovering metabolic dependencies across different chemotherapy treatments could help to rationalize the use of metabolic modulators to overcome therapy resistance.