Long-term in vitro treatment of human glioblastoma cells with temozolomide increases resistance in vivo through up-regulation of GLUT transporter and aldo-keto reductase enzyme AKR1C expression

Cisplatin-Resistant Urothelial Bladder Cancer Cells Undergo Metabolic Reprogramming beyond the Warburg Effect

Advanced urothelial bladder cancer (UBC) patients are tagged by a dismal prognosis and high mortality rates, mostly due to their poor response to standard-of-care platinum-based therapy. Mediators of chemoresistance are not fully elucidated. This work aimed to study the metabolic profile of advanced UBC, in the context of cisplatin resistance. Three isogenic pairs of parental cell lines (T24, HT1376 and KU1919) and the matching cisplatin-resistant (R) sublines were used. A set of functional assays was used to perform a metabolic screening on the cells. In comparison to the parental sublines, a tendency was observed towards an exacerbated glycolytic metabolism in the cisplatin-resistant T24 and HT1376 cells; this glycolytic phenotype was particularly evident for the HT1376/HT1376R pair, for which the cisplatin resistance ratio was higher. HT1376R cells showed decreased basal respiration and oxygen consumption associated with ATP production; in accordance, the extracellular acidification rate was also higher in the resistant subline. Glycolytic rate assay confirmed that these cells presented higher basal glycolysis, with an increase in proton efflux. While the results of real-time metabolomics seem to substantiate the manifestation of the Warburg phenotype in HT1376R cells, a shift towards distinct metabolic pathways involving lactate uptake, lipid biosynthesis and glutamate metabolism occurred with time. On the other hand, KU1919R cells seem to engage in a metabolic rewiring, recovering their preference for oxidative phosphorylation. In conclusion, cisplatin-resistant UBC cells seem to display deep metabolic alterations surpassing the Warburg effect, which likely depend on the molecular signature of each cell line.

P2X7 receptor antagonism by AZ10606120 significantly reduced in vitro tumour growth in human glioblastoma

Glioblastomas are highly aggressive and deadly brain tumours, with a median survival time of 14-18 months post-diagnosis. Current treatment modalities are limited and only modestly increase survival time. Effective therapeutic alternatives are urgently needed. The purinergic P2X7 receptor (P2X7R) is activated within the glioblastoma microenvironment and evidence suggests it contributes to tumour growth. Studies have implicated P2X7R involvement in a range of neoplasms, including glioblastomas, although the roles of P2X7R in the tumour milieu remain unclear. Here, we report a trophic, tumour-promoting role of P2X7R activation in both patient-derived primary glioblastoma cultures and the U251 human glioblastoma cell line, and demonstrate its inhibition reduces tumour growth in vitro. Primary glioblastoma and U251 cell cultures were treated with the specific P2X7R antagonist, AZ10606120 (AZ), for 72 h. The effects of AZ treatment were also compared to cells treated with the current first-line chemotherapeutic drug, temozolomide (TMZ), and a combination of both AZ and TMZ. P2X7R antagonism by AZ significantly depleted glioblastoma cell numbers compared to untreated cells, in both primary glioblastoma and U251 cultures. Notably, AZ treatment was more effective at tumour cell killing than TMZ. No synergistic effect between AZ and TMZ was observed. AZ treatment also significantly increased lactate dehydrogenase release in primary glioblastoma cultures, suggesting AZ-induced cellular cytotoxicity. Our results reveal a trophic role of P2X7R in glioblastoma. Importantly, these data highlight the potential for P2X7R inhibition as a novel and effective alternative therapeutic approach for patients with lethal glioblastomas.

Functional importance of glucose transporters and chromatin epigenetic factors in Glioblastoma Multiforme (GBM): possible therapeutics

Glioblastoma Multiforme (GBM) is an aggressive brain cancer affecting glial cells and is chemo- and radio-resistant. Glucose is considered the most vital energy source for cancer cell proliferation. During metabolism, hexose molecules will be transported into the cells via transmembrane proteins known as glucose transporter (GLUT). Among them, GLUT-1 and GLUT-3 play pivotal roles in glucose transport in GBM. Knockdown studies have established the role of GLUT-1, and GLUT-3 mediated glucose transport in GBM cells, providing insight into GLUT-mediated cancer signaling and cancer aggressiveness. This review focussed on the vital role of GLUT-1 and GLUT-3 proteins, which regulate glucose transport. Recent studies have identified the role of GLUT inhibitors in effective cancer prevention. Several of them are in clinical trials. Understanding and functional approaches towards glucose-mediated cell metabolism and chromatin epigenetics will provide valuable insights into the mechanism of cancer aggressiveness, cancer stemness, and chemo-resistance in Glioblastoma Multiforme (GBM). This review summarizes the role of GLUT inhibitors, micro-RNAs, and long non-coding RNAs that aid in inhibiting glucose uptake by the GBM cells and other cancer cells leading to the identification of potential therapeutic, prognostic as well as diagnostic markers. Furthermore, the involvement of epigenetic factors, such as microRNAs, in regulating glycolytic genes was demonstrated.

Molecular Mechanisms of Noncoding RNA in the Occurrence of Castration-Resistant Prostate Cancer

Although several therapeutic options have been shown to improve survival of most patients with prostate cancer, progression to castration-refractory state continues to present challenges in clinics and scientific research. As a highly heterogeneous disease entity, the mechanisms of castration-resistant prostate cancer (CRPC) are complicated and arise from multiple factors. Among them, noncoding RNAs (ncRNAs), the untranslated part of the human transcriptome, are closely related to almost all biological regulation, including tumor metabolisms, epigenetic modifications and immune escape, which has encouraged scientists to investigate their role in CRPC. In clinical practice, ncRNAs, especially miRNAs and lncRNAs, may function as potential biomarkers for diagnosis and prognosis of CRPC. Therefore, understanding the molecular biology of CRPC will help boost a shift in the treatment of CRPC patients. In this review, we summarize the recent findings of miRNAs and lncRNAs, discuss their potential functional mechanisms and highlight their clinical application prospects in CRPC.

When cancer drug resistance meets metabolomics (bulk, single-cell and/or spatial): Progress, potential, and perspective

Resistance to drug treatment is a critical barrier in cancer therapy. There is an unmet need to explore cancer hallmarks that can be targeted to overcome this resistance for therapeutic gain. Over time, metabolic reprogramming has been recognised as one hallmark that can be used to prevent therapeutic resistance. With the advent of metabolomics, targeting metabolic alterations in cancer cells and host patients represents an emerging therapeutic strategy for overcoming cancer drug resistance. Driven by technological and methodological advances in mass spectrometry imaging, spatial metabolomics involves the profiling of all the metabolites (metabolomics) so that the spatial information is captured bona fide within the sample. Spatial metabolomics offers an opportunity to demonstrate the drug-resistant tumor profile with metabolic heterogeneity, and also poses a data-mining challenge to reveal meaningful insights from high-dimensional spatial information. In this review, we discuss the latest progress, with the focus on currently available bulk, single-cell and spatial metabolomics technologies and their successful applications in pre-clinical and translational studies on cancer drug resistance. We provide a summary of metabolic mechanisms underlying cancer drug resistance from different aspects; these include the Warburg effect, altered amino acid/lipid/drug metabolism, generation of drug-resistant cancer stem cells, and immunosuppressive metabolism. Furthermore, we propose solutions describing how to overcome cancer drug resistance; these include early detection during cancer initiation, monitoring of clinical drug response, novel anticancer drug and target metabolism, immunotherapy, and the emergence of spatial metabolomics. We conclude by describing the perspectives on how spatial omics approaches (integrating spatial metabolomics) could be further developed to improve the management of drug resistance in cancer patients.

Allopregnanolone: Metabolism, Mechanisms of Action, and Its Role in Cancer

Allopregnanolone (3α-THP) has been one of the most studied progesterone metabolites for decades. 3α-THP and its synthetic analogs have been evaluated as therapeutic agents for pathologies such as anxiety and depression. Enzymes involved in the metabolism of 3α-THP are expressed in classical and nonclassical steroidogenic tissues. Additionally, due to its chemical structure, 3α-THP presents high affinity and agonist activity for nuclear and membrane receptors of neuroactive steroids and neurotransmitters, such as the Pregnane X Receptor (PXR), membrane progesterone receptors (mPR) and the ionotropic GABA_A receptor, among others. 3α-THP has immunomodulator and antiapoptotic properties. It also induces cell proliferation and migration, all of which are critical processes involved in cancer progression. Recently the study of 3α-THP has indicated that low physiological concentrations of this metabolite induce the progression of several types of cancer, such as breast, ovarian, and glioblastoma, while high concentrations inhibit it. In this review, we explore current knowledge on the metabolism and mechanisms of action of 3α-THP in normal and tumor cells.

Metabolic-imaging of human glioblastoma live tumors: A new precision-medicine approach to predict tumor treatment response early

Background

Glioblastoma (GB) is the most severe form of brain cancer, with a 12-15 month median survival. Surgical resection, temozolomide (TMZ) treatment, and radiotherapy remain the primary therapeutic options for GB, and no new therapies have been introduced in recent years. This therapeutic standstill is primarily due to preclinical approaches that do not fully respect the complexity of GB cell biology and fail to test efficiently anti-cancer treatments. Therefore, better treatment screening approaches are needed. In this study, we have developed a novel functional precision medicine approach to test the response to anticancer treatments in organoids derived from the resected tumors of glioblastoma patients.

Methods

GB organoids were grown for a short period of time to prevent any genetic and morphological evolution and divergence from the tumor of origin. We chose metabolic imaging by NAD(P)H fluorescence lifetime imaging microscopy (FLIM) to predict early and non-invasively ex-vivo anti-cancer treatment responses of GB organoids. TMZ was used as the benchmark drug to validate the approach. Whole-transcriptome and whole-exome analyses were performed to characterize tumor cases stratification.

Results

Our functional precision medicine approach was completed within one week after surgery and two groups of TMZ Responder and Non-Responder tumors were identified. FLIM-based metabolic tumor stratification was well reflected at the molecular level, confirming the validity of our approach, highlighting also new target genes associated with TMZ treatment and identifying a new 17-gene molecular signature associated with survival. The number of MGMT gene promoter methylated tumors was higher in the responsive group, as expected, however, some non-methylated tumor cases turned out to be nevertheless responsive to TMZ, suggesting that our procedure could be synergistic with the classical MGMT methylation biomarker.

Conclusions

For the first time, FLIM-based metabolic imaging was used on live glioblastoma organoids. Unlike other approaches, ex-vivo patient-tailored drug response is performed at an early stage of tumor culturing with no animal involvement and with minimal tampering with the original tumor cytoarchitecture. This functional precision medicine approach can be exploited in a range of clinical and laboratory settings to improve the clinical management of GB patients and implemented on other cancers as well.

Inhibition of AMPK/PFKFB3 mediated glycolysis synergizes with penfluridol to suppress gallbladder cancer growth

BACKGROUND

Penfluridol (PF) is an FDA-approved antipsychotic drug that has recently been shown to have anticancer activity. However, the anticancer effects and underlying mechanisms of PF are not well-established in gallbladder cancer (GBC).

METHODS

The anticancer efficacy of PF on GBC was investigated via a series of cell functions experiments, including cell viability, colony formation, apoptosis assays, and so on. The corresponding signaling changes after PF treatment were explored by western blotting. Then, nude mice were utilized to study and test the anticancer activity of PF in vivo. Besides, glucose consumption and lactic production assays were used to detect the glycolysis alteration.

RESULTS

In this study, we discovered that PF greatly inhibited the proliferation and invasion ability of GBC cells (GBCs). The glucose consumption and lactic generation ability of GBCs were dramatically elevated following PF treatment. Additionally, we discovered that inhibiting glycolysis could improve PF's anticancer efficacy. Further studies established that the activation of the AMPK/PFKFB3 signaling pathway medicated glycolysis after PF treatment. We proved mechanistically that inhibition of AMPK/PFKFB3 singling pathway mediated glycolysis was a potential synergetic strategy to improve the anticancer efficacy of PF on GBC.

CONCLUSIONS

By inhibiting AMPK, the anticancer effects of PF on GBCs were amplified. As a result, our investigations shed new light on the possibility of repurposing PF as an anticancer drug for GBC, and AMPK inhibition in combination with PF may represent a novel therapeutic strategy for GBC. Video abstract.

Allopregnanolone Promotes Migration and Invasion of Human Glioblastoma Cells through the Protein Tyrosine Kinase c-Src Activation

Glioblastomas (GBs) are the most aggressive and common primary malignant brain tumors. Steroid hormone progesterone (P4) and its neuroactive metabolites, such as allopregnanolone (3α-THP) are synthesized by neural, glial, and malignant GB cells. P4 promotes cellular proliferation, migration, and invasion of human GB cells at physiological concentrations. It has been reported that 3α-THP promotes GB cell proliferation. Here we investigated the effects of 3α-THP on GB cell migration and invasion, the participation of the enzymes involved in its metabolism (AKR1C1-4), and the role of the c-Src kinase in 3α-THP effects in GBs. 3α-THP 100 nM promoted migration and invasion of U251, U87, and LN229 human-derived GB cell lines. We observed that U251, LN229, and T98G cell lines exhibited a higher protein content of AKR1C1-4 than normal human astrocytes. AKR1C1-4 silencing did not modify 3α-THP effects on migration and invasion. 3α-THP activated c-Src protein at 10 min (U251 cells) and 15 min (U87 and LN229 cells). Interestingly, the pharmacological inhibition of c-Src decreases the promoting effects of 3α-THP on cell migration and invasion. Together, these data indicate that 3α-THP promotes GB migration and invasion through c-Src activation.

Targeting oncometabolism to maximize immunotherapy in malignant brain tumors

Brain tumors result in significant morbidity and mortality in both children and adults. Recent data indicates that immunotherapies may offer a survival benefit after standard of care has failed for malignant brain tumors. Modest results from several late phase clinical trials, however, underscore the need for more refined, comprehensive strategies that incorporate new mechanistic and pharmacologic knowledge. Recently, oncometabolism has emerged as an adjunct modality for combinatorial treatment approaches necessitated by the aggressive, refractory nature of high-grade glioma and other progressive malignant brain tumors. Manipulation of metabolic processes in cancer and immune cells that comprise the tumor microenvironment through controlled targeting of oncogenic pathways may be utilized to maximize the efficacy of immunotherapy and improve patient outcomes. Herein, we summarize preclinical and early phase clinical trial research of oncometabolism-based therapeutics that may augment immunotherapy by exploiting the biochemical and genetic underpinnings of brain tumors. We also examine metabolic pathways related to immune cells that target tumor cells, termed ‘tumor immunometabolism’. Specifically, we focus on glycolysis and altered glucose metabolism, including glucose transporters, hexokinase, pyruvate dehydrogenase, and lactate dehydrogenase, glutamine, and we discuss targeting arginase, adenosine, and indoleamine 2,3-dioxygenase (IDO), and toll-like receptors. Lastly, we summarize future directions targeting metabolism in combination with emerging therapies such as oncolytic virotherapy, vaccines, and chimeric antigen receptor T cells.

Investigation of the potential of bile acid methyl esters as inhibitors of aldo-keto reductase 1C2: insight from molecular docking, virtual screening, experimental assays and molecular dynamics

Human aldo-keto reductase 1C isoforms catalyze reduction of endogenous and exogenous compounds, including therapeutic drugs, and are associated with chemotherapy resistance. AKR1C2 is involved in metastatic processes and is a target for the treatment of various cancers. Here we used molecular docking to explore a series of bile acid methyl esters as AKR1C2 inhibitors. Autodock 4.2 ranked 10 of 11 test compounds above decoys based on ursodeoxycholate, an AKR1C2 inhibitor, while 5 ranked above 94% of decoys in Autodock Vina. Seven inactives reported not to inhibit AKR1C2 ranked below the decoy threshold. Virtual screen of a natural product library in Autodock Vina using the same parameters, identified steroidal derivatives, bile acids, and other AKR1C ligands in the top 5%. In experiments, 6 out of 11 tested bile acid methyl esters inhibited >50% of AKR1C2 activity, while 2 compounds were AKR1C3 inhibitors. The top ranking compound showed dose-dependent inhibition of AKR1C2 (IC50 ~3.6 µM). Molecular dynamics was used to explore interactions between a bile acid methyl ester and the AKR1C2 active site. Our molecular docking results identify AKR1C2 as a target for bile acid methyl esters, which combined with virtual screening results provides new directions for the synthesis of AKR1C inhibitors.

Kaempferol Can Reverse the 5-Fu Resistance of Colorectal Cancer Cells by Inhibiting PKM2-Mediated Glycolysis

Resistance to 5-Fluorouracil (5-Fu) chemotherapy is the main cause of treatment failure in the cure of colon cancer. Therefore, there is an urgent need to explore a safe and effective multidrug resistance reversal agent for colorectal cancer, which would be of great significance for improving clinical efficacy. The dietary flavonoid kaempferol plays a key role in the progression of colorectal cancer and 5-Fu resistance. However, the molecular mechanism of kaempferol in reversing 5-Fu resistance in human colorectal cancer cells is still unclear. We found that kaempferol could reverse the drug resistance of HCT8-R cells to 5-Fu, suggesting that kaempferol alone or in combination with 5-Fu has the potential to treat colorectal cancer. It is well known that aerobic glycolysis is related to tumor growth and chemotherapy resistance. Indeed, kaempferol treatment significantly reduced glucose uptake and lactic acid production in drug-resistant colorectal cancer cells. In terms of mechanism, kaempferol promotes the expression of microRNA-326 (miR-326) in colon cancer cells, and miR-326 could inhibit the process of glycolysis by directly targeting pyruvate kinase M2 isoform (PKM2) 3'-UTR (untranslated region) to inhibit the expression of PKM2 or indirectly block the alternative splicing factors of PKM mRNA, and then reverse the resistance of colorectal cancer cells to 5-Fu. Taken together, our data suggest that kaempferol may play an important role in overcoming resistance to 5-Fu therapy by regulating the miR-326-hnRNPA1/A2/PTBP1-PKM2 axis.

Ferroptosis-Related Gene Contributes to Immunity, Stemness and Predicts Prognosis in Glioblastoma Multiforme

Ferroptosis, a recently discovered regulated programmed cell death, is associated with tumorigenesis and progression in glioblastoma. Based on widely recognized ferroptosis-related genes (FRGs), the regulation of ferroptosis patterns and corresponding characteristics of immune infiltration of 516 GBM samples with GSE13041, TCGA-GBM, and CGGA-325 were comprehensively analyzed. Here, we revealed the expression, mutations, and CNV of FRGs in GBM. We identified three distinct regulation patterns of ferroptosis and found the hub genes of immunity and stemness among DEGs in three patterns. A prognostic model was constructed based on five FRGs and verified at the mRNA and protein level. The risk score can not only predict the prognosis but also the degree of immune infiltration and ICB responsiveness by functional annotation. The overall assessment of FRGs in GBM patients will guide the direction of improved research and develop new prognostic prediction tools.

The role of AKR1 family in tamoxifen resistant invasive lobular breast cancer based on data mining

Background

Tamoxifen (TAM) resistance to invasive lobular cell carcinoma is a challenge for breast cancer treatment. This study explored the role of Aldo-keto reductase family 1 (AKR1) family in tamoxifen-resistant aggressive lobular breast cancer based on data mining.

Methods

TAM-resistant invasive lobular breast cancer gene chip was downloaded from the Gene Expression Omnibus (GEO) database (accession-numbered as GSE96670). The online analytical tool GEO2R was used to screen for differentially expressed genes in TAM-resistant invasive lobular breast cancer cells and TAM-sensitive counterparts. A protein-protein interaction (PPI) networks were constructed using the STRING online platform and the Cytoscape software. GeneMANIA and GSCALite online tools were used to reveal the potential role of these hub genes in breast cancer progression and TAM resistance development. And the used the GSE67916 microarray data set to verify the differentially expression of these hub genes in breast cancer. The protein expression levels of AKR1C1, AKR1C2 and AKR1C3 in TAM-sensitive and resistant breast cancer cells were compared. The TAM sensitivity of breast cancer cells with or without AKR1C1, AKR1C2 or AKR1C3 gene manipulation was evaluated by cell viability assay.

Results

A total of 184 differentially expressed genes were screened. Compared with TAM sensitive breast cancer cells, 162 were up-regulated and 22 were down-regulated. The study identified several hub genes in the PPI network that may be involved in the development of TAM resistance of breast cancer, including signal transducer and activator of transcription 1 (STAT1), estrogen receptor alpha (ESR1), fibronectin1 (FN1), cytochrome P4501B1 (CYP1B1), AKR1C1, AKR1C2, AKR1C3 and uridine diphosphate glucuronosyltransferase (UGT) 1A family genes (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10). Compared with TAM-sensitive counterparts, the expression levels of AKR1C1, AKR1C2, and AKR1C3 were up-regulated in TAM-resistant breast cancer cells.

Conclusions

Overexpression of each of these three genes significantly increased the resistance of breast cancer cells to TAM treatment, while their knockdown showed opposite effects, indicating that they are potential therapeutic target for the treatment of TAM-resistant breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09040-8.

Overview of human 20 alpha-hydroxysteroid dehydrogenase (AKR1C1): Functions, regulation, and structural insights of inhibitors

Human aldo-keto reductase family 1C1 (AKR1C1) is an important enzyme involved in human hormone metabolism, which is mainly responsible for the metabolism of progesterone in the human body. AKR1C1 is highly expressed and has an important relationship with the occurrence and development of various diseases, especially some cancers related to hormone metabolism. Nowadays, many inhibitors against AKR1C1 have been discovered, including some synthetic compounds and natural products, which have certain inhibitory activity against AKR1C1 at the target level. Here we briefly reviewed the physiological and pathological functions of AKR1C1 and the relationship with the disease, and then summarized the development of AKR1C1 inhibitors, elucidated the interaction between inhibitors and AKR1C1 through molecular docking results and existing co-crystal structures. Finally, we discussed the design ideals of selective AKR1C1 inhibitors from the perspective of AKR1C1 structure, discussed the prospects of AKR1C1 in the treatment of human diseases in terms of biomarkers, pre-receptor regulation and single nucleotide polymorphisms, aiming to provide new ideas for drug research targeting AKR1C1.

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.

Olaparib Is a Mitochondrial Complex I Inhibitor That Kills Temozolomide-Resistant Human Glioblastoma Cells

Glioblastoma represents the highest grade of brain tumors. Despite maximal resection surgery associated with radiotherapy and concomitant followed by adjuvant chemotherapy with temozolomide (TMZ), patients have a very poor prognosis due to the rapid recurrence and the acquisition of resistance to TMZ. Here, initially considering that TMZ is a prodrug whose activation is pH-dependent, we explored the contribution of glioblastoma cell metabolism to TMZ resistance. Using isogenic TMZ-sensitive and TMZ-resistant human glioblastoma cells, we report that the expression of O6-methylguanine DNA methyltransferase (MGMT), which is known to repair TMZ-induced DNA methylation, does not primarily account for TMZ resistance. Rather, fitter mitochondria in TMZ-resistant glioblastoma cells are a direct cause of chemoresistance that can be targeted by inhibiting oxidative phosphorylation and/or autophagy/mitophagy. Unexpectedly, we found that PARP inhibitor olaparib, but not talazoparib, is also a mitochondrial Complex I inhibitor. Hence, we propose that the anticancer activities of olaparib in glioblastoma and other cancer types combine DNA repair inhibition and impairment of cancer cell respiration.

Polygodial and Ophiobolin A Analogues for Covalent Crosslinking of Anticancer Targets

In a search of small molecules active against apoptosis-resistant cancer cells, including glioma, melanoma, and non-small cell lung cancer, we previously prepared α,β- and γ,δ-unsaturated ester analogues of polygodial and ophiobolin A, compounds capable of pyrrolylation of primary amines and demonstrating double-digit micromolar antiproliferative potencies in cancer cells. In the current work, we synthesized dimeric and trimeric variants of such compounds in an effort to discover compounds that could crosslink biological primary amine containing targets. We showed that such compounds retain the pyrrolylation ability and possess enhanced single-digit micromolar potencies toward apoptosis-resistant cancer cells. Target identification studies of these interesting compounds are underway.

MicroRNAs and Metabolism: Revisiting the Warburg Effect with Emphasis on Epigenetic Background and Clinical Applications

Since the well-known hallmarks of cancer were described by Hanahan and Weinberg, fundamental advances of molecular genomic technologies resulted in the discovery of novel puzzle pieces in the multistep pathogenesis of cancer. MicroRNAs are involved in the altered epigenetic pattern and metabolic phenotype of malignantly transformed cells. They contribute to the initiation, progression and metastasis-formation of cancers, also interacting with oncogenes, tumor-suppressor genes and epigenetic modifiers. Metabolic reprogramming of cancer cells results from the dysregulation of a complex network, in which microRNAs are located at central hubs. MicroRNAs regulate the expression of several metabolic enzymes, including tumor-specific isoforms. Therefore, they have a direct impact on the levels of metabolites, also influencing epigenetic pattern due to the metabolite cofactors of chromatin modifiers. Targets of microRNAs include numerous epigenetic enzymes, such as sirtuins, which are key regulators of cellular metabolic homeostasis. A better understanding of reversible epigenetic and metabolic alterations opened up new horizons in the personalized treatment of cancer. MicroRNA expression levels can be utilized in differential diagnosis, prognosis stratification and prediction of chemoresistance. The therapeutic modulation of microRNA levels is an area of particular interest that provides a promising tool for restoring altered metabolism of cancer cells.

The Mechanism of Warburg Effect-Induced Chemoresistance in Cancer

Although chemotherapy can improve the overall survival and prognosis of cancer patients, chemoresistance remains an obstacle due to the diversity, heterogeneity, and adaptability to environmental alters in clinic. To determine more possibilities for cancer therapy, recent studies have begun to explore changes in the metabolism, especially glycolysis. The Warburg effect is a hallmark of cancer that refers to the preference of cancer cells to metabolize glucose anaerobically rather than aerobically, even under normoxia, which contributes to chemoresistance. However, the association between glycolysis and chemoresistance and molecular mechanisms of glycolysis-induced chemoresistance remains unclear. This review describes the mechanism of glycolysis-induced chemoresistance from the aspects of glycolysis process, signaling pathways, tumor microenvironment, and their interactions. The understanding of how glycolysis induces chemoresistance may provide new molecular targets and concepts for cancer therapy.

A High Epigenetic Risk Score Shapes the Non-Inflamed Tumor Microenvironment in Breast Cancer

Background: Epigenetic dysregulation via aberrant DNA methylation has gradually become recognized as an efficacious signature for predicting tumor prognosis and response to therapeutic targets. However, reliable DNA methylation biomarkers describing tumorigenesis remain to be comprehensively explored regarding their prognostic and therapeutic potential in breast cancer (BC).

Methods: Whole-genome methylation datasets integrated from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database were profiled (n = 1,268). A three-stage selection procedure (discovery, training, and external validation) was utilized to screen out the prominent biomarkers and establish a robust risk score from more than 300,000 CpG sites after quality control, rigorous filtering, and reducing dimension. Moreover, gene set enrichment analyses guided us to systematically correlate this epigenetic risk score with immunological characteristics, including immunomodulators, anti-cancer immunity cycle, immune checkpoints, tumor-infiltrating immune cells and a series of signatures upon modulating components within BC tumor microenvironment (TME). Multi-omics data analyses were performed to decipher specific genomic alterations in low- and high-risk patients. Additionally, we also analyzed the role of risk score in predicting response to several treatment options.

Results: A 10-CpG-based prognostic signature which could significantly and independently categorize BC patients into distinct prognoses was established and sufficiently validated. And we hypothesize that this signature designs a non-inflamed TME in BC based on the evidence that the derived risk score is negatively correlated with tumor-associated infiltrating immune cells, anti-cancer immunity cycle, immune checkpoints, immune cytolytic activity, T cell inflamed score, immunophenoscore, and the vast majority of immunomodulators. The identified high-risk patients were characterized by upregulation of immune inhibited oncogenic pathways, higher TP53 mutation and copy number burden, but lower response to cancer immunotherapy and chemotherapy.

Conclusion: Our work highlights the complementary roles of 10-CpG-based signature in estimating overall survival in BC patients, shedding new light on investigating failed events concerning immunotherapy at present.

Synergistic Effect of Gefitinib and Temozolomide on U87MG Glioblastoma Angiogenesis

One of the most common and deadly brain tumors is Glioblastoma multiforme (GBM). Due to recent advances in angiogenesis and its related key factors, this process as a hallmark in glioblastoma has attracted more consideration from the research community. Temozolomide (TMZ) as the first-line treatment used to treat GBM but, resistance to TMZ limits its effectiveness and the need for better treatments is still felt. Therefore, we aimed to examine the Synergistic effects of Gefitinib (GFI) in combination with Temozolomide on VEGF and MMPs in glioma cell line (U87MG). Our results displayed that GFI could induce cytotoxic effects in U87MG with IC50 values of 11 μM. U87MG cells produced large amounts of VEGF without any stimuli, and the results showed that GFI in combination with TMZ caused a significant decrease in VEGF production in these cells. In this study, we demonstrated that after treating with TMZ and GFI, there was more decrease in the levels of MMP 2 and 9 secretions in cells than treatment with GFI and TMZ doses alone. This study indicates synergistic effects of GFI plus TMZ against glioma are mediated by the potentiated anti-angiogenesis. Therefore, it can be considered as a promising plan for future studies.

Regulation of Cancer Metabolism by Deubiquitinating Enzymes: The Warburg Effect

Cancer is a disorder of cell growth and proliferation, characterized by different metabolic pathways within normal cells. The Warburg effect is a major metabolic process in cancer cells that affects the cellular responses, such as proliferation and apoptosis. Various signaling factors down/upregulate factors of the glycolysis pathway in cancer cells, and these signaling factors are ubiquitinated/deubiquitinated via the ubiquitin-proteasome system (UPS). Depending on the target protein, DUBs act as both an oncoprotein and a tumor suppressor. Since the degradation of tumor suppressors and stabilization of oncoproteins by either negative regulation by E3 ligases or positive regulation of DUBs, respectively, promote tumorigenesis, it is necessary to suppress these DUBs by applying appropriate inhibitors or small molecules. Therefore, we propose that the DUBs and their inhibitors related to the Warburg effect are potential anticancer targets.

From Laboratory Studies to Clinical Trials: Temozolomide Use in IDH-Mutant Gliomas

In this review, we discuss the use of the alkylating agent temozolomide (TMZ) in the treatment of IDH-mutant gliomas. We describe the challenges associated with TMZ in clinical (drug resistance and tumor recurrence) and preclinical settings (variabilities associated with in vitro models) in treating IDH-mutant glioma. Lastly, we summarize the emerging therapeutic targets that can potentially be used in combination with TMZ.

Aldo-Keto Reductase 1C3 Mediates Chemotherapy Resistance in Esophageal Adenocarcinoma via ROS Detoxification

Simple Summary

The multidrug resistance of EAC is one of the major obstacles to chemotherapeutic efficiency. Our study aims to explore the molecular mechanism of AKR1C3 as a novel therapeutic target to overcome chemotherapy resistance for EAC patients. We demonstrate that AKR1C3 renders chemotherapy resistance through controlling cellular ROS levels via AKT signaling in EAC cells. Modulation of intracellular GSH levels by AKR1C3 could scavenge the intracellular ROS, thus regulating apoptosis. Targeting AKR1C3 may represent a novel strategy to sensitize EAC cells to conventional chemotherapy treatment and benefit the overall survival of patients diagnosed with EAC.

Abstract

Esophageal adenocarcinoma (EAC) is one of the most lethal malignancies, and limits promising treatments. AKR1C3 represents a therapeutic target to combat the resistance in many cancers. However, the molecular mechanism of AKR1C3 in the chemotherapy resistance of EAC is still unclear. We found that the mRNA level of AKR1C3 was higher in EAC tumor tissues, and that high AKR1C3 expression might be associated with poor overall survival of EAC patients. AKR1C3 overexpression decreased cell death induced by chemotherapeutics, while knockdown of AKR1C3 attenuated the effect. Furthermore, we found AKR1C3 was inversely correlated with ROS production. Antioxidant NAC rescued chemotherapy-induced apoptosis in AKR1C3 knockdown cells, while the GSH biosynthesis inhibitor BSO reversed a protective effect of AKR1C3 against chemotherapy. AKT phosphorylation was regulated by AKR1C3 and might be responsible for eliminating over-produced ROS in EAC cells. Intracellular GSH levels were modulated by AKR1C3 and the inhibition of AKT could reduce GSH level in EAC cells. Here, we reported for the first time that AKR1C3 renders chemotherapy resistance through controlling ROS levels via AKT signaling in EAC cells. Targeting AKR1C3 may represent a novel strategy to sensitize EAC cells to conventional chemotherapy.

Contemporary Mouse Models in Glioma Research

Despite advances in understanding of the molecular pathogenesis of glioma, outcomes remain dismal. Developing successful treatments for glioma requires faithful in vivo disease modeling and rigorous preclinical testing. Murine models, including xenograft, syngeneic, and genetically engineered models, are used to study glioma-genesis, identify methods of tumor progression, and test novel treatment strategies. Since the discovery of highly recurrent isocitrate dehydrogenase (IDH) mutations in lower-grade gliomas, there is increasing emphasis on effective modeling of IDH mutant brain tumors. Improvements in preclinical models that capture the phenotypic and molecular heterogeneity of gliomas are critical for the development of effective new therapies. Herein, we explore the current status, advancements, and challenges with contemporary murine glioma models.

A Selective Competitive Inhibitor of Aldehyde Dehydrogenase 1A3 Hinders Cancer Cell Growth, Invasiveness and Stemness In Vitro

Simple Summary

The aldehyde dehydrogenases enzymes (ALDHs) are promising drug targets in cancer therapy. ALDHs are members of an enzymatic superfamily composed by 19 isoforms involved in the oxidation of aldehydes, with a scavenger role. Among them, the isoform ALDH1A3 is a cancer biomarker since it is highly expressed in cancer stem cells characterized by a marked drug resistance and the capacity to promote self-renewal, clonogenic growth and tumour-initiating capacity. In this paper, we present the first highly potent and selective ALDH1A3 inhibitor able to induce cytotoxic effects and to reduce cell migration and stemness of ALDH1A3-positive cancer cells. We propose the targeting of the ALDH1A3 enzyme as a promising approach for improving the treatments outcomes of patients affected by ALDH1A3-positive cancers.

Abstract

Aldehyde dehydrogenase 1A3 (ALDH1A3) belongs to an enzymatic superfamily composed by 19 different isoforms, with a scavenger role, involved in the oxidation of a plethora of aldehydes to the respective carboxylic acids, through a NAD+-dependent reaction. Previous clinical studies highlighted the high expression of ALDH1A3 in cancer stem cells (CSCs) correlated to a higher risk of cancer relapses, chemoresistance and a poor clinical outcome. We report on the structural, biochemical, and cellular characterization of NR6, a new selective ALDH1A3 inhibitor derived from an already published ALDH non-selective inhibitor with cytotoxic activity on glioblastoma and colorectal cancer cells. Crystal structure, through X-Ray analysis, showed that NR6 binds a non-conserved tyrosine residue of ALDH1A3 which drives the selectivity towards this isoform, as supported by computational binding simulations. Moreover, NR6 shows anti-metastatic activity in wound healing and invasion assays and induces the downregulation of cancer stem cell markers. Overall, our work confirms the role of ALDH1A3 as an important target in glioblastoma and colorectal cells and propose NR6 as a promising molecule for future preclinical studies.

Glycolysis-induced drug resistance in tumors-A response to danger signals?

Tumor cells often switch from mitochondrial oxidative metabolism to glycolytic metabolism even under aerobic conditions. Tumor cell glycolysis is accompanied by several nonenzymatic activities among which induction of drug resistance has important therapeutic implications. In this article, we review the main aspects of glycolysis-induced drug resistance. We discuss the classes of antitumor drugs that are affected and the components of the glycolytic pathway (transporters, enzymes, metabolites) that are involved in the induction of drug resistance. Glycolysis-associated drug resistance occurs in response to stimuli, either cell-autonomous (e.g., oncoproteins) or deriving from the tumor microenvironment (e.g., hypoxia or pseudohypoxia, mechanical cues, etc.). Several mechanisms mediate the induction of drug resistance in response to glycolytic metabolism: inhibition of apoptosis, induction of epithelial-mesenchymal transition, induction of autophagy, inhibition of drug influx and increase of drug efflux. We suggest that drug resistance in response to glycolysis comes into play in presence of qualitative (e.g., expression of embryonic enzyme isoforms, post-translational enzyme modifications) or quantitative (e.g., overexpression of enzymes or overproduction of metabolites) alterations of glycolytic metabolism. We also discern similarities between changes occurring in tumor cells in response to stimuli inducing glycolysis-associated drug resistance and those occurring in cells of the innate immune system in response to danger signals and that have been referred to as danger-associated metabolic modifications. Eventually, we briefly address that also mitochondrial oxidative metabolism may induce drug resistance and discuss the therapeutic implications deriving from the fact that the main energy-generating metabolic pathways may be both at the origin of antitumor drug resistance.

Power of two: combination of therapeutic approaches involving glucose transporter (GLUT) inhibitors to combat cancer

Cancer research of the Warburg effect, a hallmark metabolic alteration in tumors, focused attention on glucose metabolism whose targeting uncovered several agents with promising anticancer effects at the preclinical level. These agents' monotherapy points to their potential as adjuvant combination therapy to existing standard chemotherapy in human trials. Accordingly, several studies on combining glucose transporter (GLUT) inhibitors with chemotherapeutic agents, such as doxorubicin, paclitaxel, and cytarabine, showed synergistic or additive anticancer effects, reduced chemo-, radio-, and immuno-resistance, and reduced toxicity due to lowering the therapeutic doses required for desired chemotherapeutic effects, as compared with monotherapy. The combinations have been specifically effective in treating cancer glycolytic phenotypes, such as pancreatic and breast cancers. Even combining GLUT inhibitors with other glycolytic inhibitors and energy restriction mimetics seems worthwhile. Though combination clinical trials are in the early phase, initial results are intriguing. The various types of GLUTs, their role in cancer progression, GLUT inhibitors, and their anticancer mechanism of action have been reviewed several times. However, utilizing GLUT inhibitors as combination therapeutics has received little attention. We consider GLUT inhibitors agents that directly affect glucose transporters by binding to them or indirectly alter glucose transport by changing the transporters' expression level. This review mainly focuses on summarizing the effects of various combinations of GLUT inhibitors with other anticancer agents and providing a perspective on the current status.

Clinical and Biological Significances of a Ferroptosis-Related Gene Signature in Glioma

Ferroptosis is a form of cell death characterized by non-apoptosis induced by small molecules in tumors. Studies have demonstrated that ferroptosis regulates the biological behaviors of tumors. Therefore, genes that control ferroptosis can be a promising candidate bioindicator in tumor therapy. Herein, functions of ferroptosis-related genes in glioma were investigated. We systematically assessed the relationship between ferroptosis-related genes expression profiles and prognosis in glioma patients based on The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) RNA sequencing datasets. Using the non-negative matrix factorization (NMF) clustering method, 84 ferroptosis-related genes in the RNA sequencing data were distinctly classified into two subgroups (named cluster 1 and cluster 2) in glioma. The least absolute shrinkage and selection operator (LASSO) was used to develop a 25 gene risk signature. The relationship between the gene risk signature and clinical features in glioma was characterized. Results show that the gene risk signature associated with clinical features can be as an independent prognostic indicator in glioma patients. Collectively, the ferroptosis-related risk signature presented in this study can potentially predict the outcome of glioma patients.

5alpha-dihydroprogesterone promotes proliferation and migration of human glioblastoma cells

Glioblastomas (GBMs) are the most common and deadliest intracranial tumors. Steroid hormones, such as progesterone (P4), at physiological concentrations, promote proliferation, and migration of human GBM cells in vivo and in vitro. Neuronal and glial cells, but also GBMs, metabolize P4 and synthesize different active metabolites such as 5α-dihydroprogesterone (5α-DHP). However, their contribution to GBM malignancy remains unknown. Here, we determined the 5α-DHP effects on the number of cells, proliferation, and migration of the U87 and U251 human GBM-derived cell lines. Of the tested concentrations (1 nM-1 µM), 5α-DHP 10 nM significantly increased the number of U87 and U251 cells from day 2 of treatment, and proliferation (at day 3) in a similar manner as P4 (10 nM). The treatment with the progesterone receptor (PR) antagonist RU486 (mifepristone), blocked the effects of 5α-DHP on the number of cells and proliferation. Besides, in U251 and LN229 GBM cells, 5α-DHP promoted cell migration (from 12 to 24 h). We also determined that GBM cells expressed the 3α-hydroxysteroid oxidoreductases (3α-HSOR), which reversibly reduce 5α-DHP to allopregnanolone (3α-THP). These data indicate that 5α-DHP induces proliferation and migration of human GBM through the activation of PR.

Targeting Metabolism in Cancer Cells and the Tumour Microenvironment for Cancer Therapy

Targeting altered tumour metabolism is an emerging therapeutic strategy for cancer treatment. The metabolic reprogramming that accompanies the development of malignancy creates targetable differences between cancer cells and normal cells, which may be exploited for therapy. There is also emerging evidence regarding the role of stromal components, creating an intricate metabolic network consisting of cancer cells, cancer-associated fibroblasts, endothelial cells, immune cells, and cancer stem cells. This metabolic rewiring and crosstalk with the tumour microenvironment play a key role in cell proliferation, metastasis, and the development of treatment resistance. In this review, we will discuss therapeutic opportunities, which arise from dysregulated metabolism and metabolic crosstalk, highlighting strategies that may aid in the precision targeting of altered tumour metabolism with a focus on combinatorial therapeutic strategies.

Glucose-coated Berberine Nanodrug for Glioma Therapy through Mitochondrial Pathway

Introduction

Glioma is the primary malignant brain tumor with poor prognosis. Berberine (BBR) was the potential drug for anti-tumor in glioma cells. Based on its limitation of poor aqueous solubility and instability, little information of BBR nanoparticles is reported in glioma.

Methods

Different solutions including 5% glucose, 1*PBS, ddH₂O, 0.9% NaCl, cell culture medium were selected, and only 5% glucose and ddH₂O exhibited BBR-related nanoparticles. After heating for a longer time or adding a higher concentration of glucose solution, BBR nanoparticles were detected by TEM analysis. The uptake of BBR-Glu or BBR-Water nanoparticles were detected by immunofluorescence analysis for BBR autofluorescence. Cell viability was measured by MTT assay and Western blotting analysis. Apoptosis was performed with flow cytometric analysis and was detected by cleaved caspase-3 immuno-fluorescent staining. Cell cycle was used by flow cytometric analysis. Cytoskeleton was observed by confocal analysis using the neuron specific Class III ß-tubulin and ß-tubulin antibodies. Mitochondrial-related proteins were detected by Western blotting analyses and mito-tracker staining in live cells. Mitochondrion structures were observed by TEM analysis. ROS generation and ATP production were detected by related commercial kits. The tracking of BBR-Glu or BBR-Water nanoparticles into blood–brain barrier was observed in primary tumor-bearing models. The fluorescence of BBR was detected by confocal analyses in brains and gliomas.

Results

BBR-Glu nanoparticles became more homogenized and smaller with dose- and time-dependent manners. BBR-Glu nanoparticles were easily absorbed in glioma cells. The IC₅₀ of BBR-Glu in U87 and U251 was far lower than that of BBR-Water. BBR-Glu performed better cytotoxicity, with higher G2/M phase arrest, decreased cell viability by targeting mitochondrion. In primary U87 glioma-bearing mice, BBR-Glu exhibited better imaging in brains and gliomas, indicating that more BBR moved across the blood–brain tumor barrier.

Discussion

BBR-Glu nanoparticles have better solubility and stability, providing a promising strategy in glioma precision treatment.

MP-Pt(IV): A MAOB-Sensitive Mitochondrial-Specific Prodrug for Treating Glioblastoma

We have previously reported the in vitro and in vivo efficacy of N,N-bis(2-chloroethyl)-2-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)propenamide (MP-MUS), a prodrug that targeted the mitochondria of glioblastoma (GBM). The mitochondrial enzyme, monoamine oxidase B (MAOB), is highly expressed in GBM and oxidizes an uncharged methyl-tetrahydropyridine (MP-) moiety into the mitochondrially targeted cationic form, methyl-pyridinium (P⁺-). Coupling this MAOB-sensitive group to a nitrogen mustard produced a prodrug that damaged GBM mitochondria and killed GBM cells. Unfortunately, the intrinsic reactivity of the nitrogen mustard group and low solubility of MP-MUS precluded clinical development. In our second-generation prodrug, MP-Pt(IV), we coupled the MP group to an unreactive cisplatin precursor. The enzymatic conversion of MP-Pt(IV) to P⁺-Pt(IV) was tested using recombinant human MAOA and rhMAOB. The generation of cisplatin from Pt(IV) by ascorbate was studied optically and using mass spectroscopy. Efficacy toward primary GBM cells and tumors was studied in vitro and in an intracranial patient-derived xenograft mice GBM model. Our studies demonstrate that MP-Pt(IV) is selectively activated by MAOB. MP-Pt(IV) is highly toxic toward GBM cells in vitro MP-Pt(IV) toxicity against GBM is potentiated by elevating mitochondrial ascorbate and can be arrested by MAOB inhibition. In in vitro studies, sublethal MP-Pt(IV) doses elevated mitochondrial MAOB levels in surviving GBM cells. MP-Pt(IV) is a potent chemotherapeutic in intracranial patient-derived xenograft mouse models of primary GBM and potentiates both temozolomide and temozolomide-chemoradiation therapies. MP-Pt(IV) was well tolerated and is highly effective against GBM in both in vitro and in vivo models.

Expedient synthesis and anticancer evaluation of dual-action 9-anilinoacridine methyl triazene chimeras

The efficient synthesis of molecular hybrids including a DNA-intercalating 9-anilinoacridine (9-AnA) core and a methyl triazene DNA-methylating moiety is described. Nucleophilic aromatic substitution (S_N Ar) and electrophilic aromatic substitution (EAS) reactions using readily accessible starting materials provide a quick entry to novel bifunctional anticancer molecules. The chimeras were evaluated for their anticancer activity. Chimera 7b presented the highest antitumor activity at low micromolar IC₅₀ values in antiproliferative assays performed with various cancer cell lines. In comparison, compound 7b outperformed DNA-intercalating drugs like amsacrine and AHMA. Mechanistic studies of chimera 7b suggest a dual mechanism of action: methylation of the DNA-repairing protein MGMT associated with the triazene structural portion and Topo II inhibition by intercalation of the acridine core.

Considering the Experimental use of Temozolomide in Glioblastoma Research

Temozolomide (TMZ) currently remains the only chemotherapeutic component in the approved treatment scheme for Glioblastoma (GB), the most common primary brain tumour with a dismal patient's survival prognosis of only ~15 months. While frequently described as an alkylating agent that causes DNA damage and thus-ultimately-cell death, a recent debate has been initiated to re-evaluate the therapeutic role of TMZ in GB. Here, we discuss the experimental use of TMZ and highlight how it differs from its clinical role. Four areas could be identified in which the experimental data is particularly limited in its translational potential: 1. transferring clinical dosing and scheduling to an experimental system and vice versa; 2. the different use of (non-inert) solvent in clinic and laboratory; 3. the limitations of established GB cell lines which only poorly mimic GB tumours; and 4. the limitations of animal models lacking an immune response. Discussing these limitations in a broader biomedical context, we offer suggestions as to how to improve transferability of data. Finally, we highlight an underexplored function of TMZ in modulating the immune system, as an example of where the aforementioned limitations impede the progression of our knowledge.

LncRNA TTN-AS1 Regulates miR-524-5p and RRM2 to Promote Breast Cancer Progression

Background

Recent studies suggest many long non-coding RNAs (lncRNAs) are crucial oncogenes or tumor suppressors. This study intended to investigate the biological function and mechanism of lncRNA TTN antisense RNA 1 (TTN-AS1) in the progression of breast cancer (BC).

Materials and Methods

BC tissue samples were collected. The expression of TTN-AS1 in BC tissues and adjacent tissues was detected by qRT-PCR, and the relationship between pathological indicators and TTN-AS1 expression was analyzed by chi-square test. BC cell lines T47D and BT549 were utilized as cell models. CCK-8 assay and BrdU assay were used to detect the effect of TTN-AS1 on BC cell proliferation. Transwell assay was used to detect the effects of TTN-AS1 on cell migration and invasion. In addition, dual-luciferase reporter gene assay was used to confirm the targeting relationship between miR-524-5p and TTN-AS1. Western blot was used to detect the function of TTN-AS1 on regulating ribonucleotide reductase subunit 2 (RRM2) and survivin. Additionally, subcutaneous xenotransplanted tumor model and tail vein injection model were constructed in vivo.

Results

The expression of TTN-AS1 in BC tissues was significantly higher than that in normal tissues, and its high expression was correlated with adverse pathological indicators. Overexpression of TTN-AS1 significantly promoted the proliferation, migration and invasion of BC cells. TTN-AS1 knockdown suppressed the malignant phenotypes of BC cells. TTN-AS1 overexpression significantly impeded the expression of miR-524-5p, but increased the expression of RRM2.

Conclusion

TTN-AS1 exerts oncogenic function in BC by repressing miR-524-5p and increasing the expression of RRM2.

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 SIRT2-mediated deacetylation of AKR1C1 is required for suppressing its pro-metastasis function in Non-Small Cell Lung Cancer

Aldo-keto reductase family 1 member C1 (AKR1C1) promotes malignancy of Non-Small Cell Lung Cancer (NSCLC) by activating Signal Transducer and Activator of Transcription 3 (STAT3) pathway. However, how the pro-metastatic functions of AKR1C1 are switched on/off remains unknown. Methods: Immunoprecipitation and LC-MS/MS analyses were performed to identify the acetylation on AKR1C1 protein, and the functional analyses (in vitro and in vivo) were performed to depict the contribution of acetylation to the pro-metastatic effects of AKR1C1. Results: Here we report that acetylated AKR1C1 on two lysine residues K185 & K201 is critical to its pro-metastatic role. The acetylation modification has no impact on the canonical enzymatic activity of AKR1C1, while it is required for the interaction between AKR1C1 to STAT3, which triggers the downstream transduction events, ultimately mobilizing cells. Importantly, the deacetylase Sirtuin 2 (SIRT2) is capable of deacetylating AKR1C1, inhibiting the transactivation of STAT3 target genes, thus suppressing the migration of cells. Conclusion: Acetylation on Lysines 185 and 201 of AKR1C1 dictates its pro-metastatic potential both in vitro and in vivo, and the reverting of acetylation by Sirtuin 2 provides potential therapeutic targets for treatment against metastatic NSCLC patients with high AKR1C1 expression.

Oxidized Vitamin C (DHA) Overcomes Resistance to EGFR-targeted Therapy of Lung Cancer through Disturbing Energy Homeostasis

Switching aerobic respiration to anaerobic glycolysis of cancer cells plays an important role in development and progression of acquired resistance. Since vitamin C enabled the inhibition of glycolysis of cancer cells, and erlotinib-resistant sub-line of HCC827 (ER6 cells) switched its metabolic features to higher glycolysis for survival, we hypothesize that vitamin C is able to inhibit glycolysis of ER6 cells. In this study, we found that both reduced vitamin C and oxidized vitamin C (DHA) could selectively suppress the viability of ER6 cells. DHA was efficient in inhibiting glycolysis and leading to energy crisis, which could be one mechanism for overcoming drug resistance to erlotinib of ER6 cells. Our data suggest that applying DHA could be a novel treatment strategy for NSCLC with acquired resistance to targeted therapy.

miR-222/GAS5 is involved in DNA damage and cytotoxic effects induced by temozolomide in T98G cell line

Temozolomide (TMZ), a therapeutic DNA alkylator that can cause lethal DNA damage in cancer cells, is widely used for the standard chemotherapy against glioblastoma. However, long-term treatment with TMZ often causes drug resistance and poor prognosis, the mechanism of which remains largely unclear. This study aimed to investigate the possible role of miR-222/GAS5 axis on DNA damage and cytotoxic effects induced by TMZ in glioblastoma cells (T98G). Data suggest that the DNA comet tail length of T98G is positively correlated with the levels of miR-222 (R²  = 0.9808, P < 0.05), and negatively correlated with the levels of GAS5 (R²  = 0.8903, P < 0.05). The optical density value of T98G is negatively correlated with the levels of miR-222 (R²  = 0.7848, P < 0.05), and positively correlated with the levels of GAS5 (R²  = 0.6886, P < 0.05). Furthermore, comet tail length and optical density value are negatively and positively correlated with the levels of O-6-methylguanine-DNA methyltransferase, respectively (R²  = 0.8462, P < 0.05; R²  = 0.7018, P < 0.05). In conclusion, miR-222/GAS5 is involved in DNA damage and cytotoxic effects induced by TMZ, which means that miR-222/GAS5 may have great potential of being used as a biomarker for screening of chemotherapeutic alkylators.

Rare Stochastic Expression of O6-Methylguanine- DNA Methyltransferase (MGMT) in MGMT-Negative Melanoma Cells Determines Immediate Emergence of Drug-Resistant Populations upon Treatment with Temozolomide In Vitro and In Vivo

The chemotherapeutic agent temozolomide (TMZ) kills tumor cells preferentially via alkylation of the O6-position of guanine. However, cells that express the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), or harbor deficient DNA mismatch repair (MMR) function, are profoundly resistant to this drug. TMZ is in clinical use for melanoma, but objective response rates are low, even when TMZ is combined with O6-benzylguanine (O6BG), a potent MGMT inhibitor. We used in vitro and in vivo models of melanoma to characterize the early events leading to cellular TMZ resistance. Melanoma cell lines were exposed to a single treatment with TMZ, at physiologically relevant concentrations, in the absence or presence of O6BG. Surviving clones and mass cultures were analyzed by Western blot, colony formation assays, and DNA methylation studies. Mice with melanoma xenografts received TMZ treatment, and tumor tissue was analyzed by immunohistochemistry. We found that MGMT-negative melanoma cell cultures, before any drug treatment, already harbored a small fraction of MGMT-positive cells, which survived TMZ treatment and promptly became the dominant cell type within the surviving population. The MGMT-negative status in individual cells was not stable, as clonal selection of MGMT-negative cells again resulted in a mixed population harboring MGMT-positive, TMZ-resistant cells. Blocking the survival advantage of MGMT via the addition of O6BG still resulted in surviving clones, although at much lower frequency and independent of MGMT, and the resistance mechanism of these clones was based on a common lack of expression of MSH6, a key MMR enzyme. TMZ treatment of mice implanted with MGMT-negative melanoma cells resulted in effective tumor growth delay, but eventually tumor growth resumed, with tumor tissue having become MGMT positive. Altogether, these data reveal stochastic expression of MGMT as a pre-existing, key determinant of TMZ resistance in melanoma cell lines. Although MGMT activity can effectively be eliminated by pharmacologic intervention with O6BG, additional layers of TMZ resistance, although considerably rarer, are present as well and minimize the cytotoxic impact of TMZ/O6BG combination treatment. Our results provide rational explanations regarding clinical observations, where the TMZ/O6BG regimen has yielded mostly disappointing outcomes in melanoma patients.

AKR1C enzymes sustain therapy resistance in paediatric T-ALL

Background

Despite chemotherapy intensification, a subgroup of high-risk paediatric T-cell acute lymphoblastic leukemia (T-ALL) patients still experience treatment failure. In this context, we hypothesised that therapy resistance in T-ALL might involve aldo-keto reductase 1C (AKR1C) enzymes as previously reported for solid tumors.

Methods

Expression of NRF2-AKR1C signaling components has been analysed in paediatric T-ALL samples endowed with different treatment outcomes as well as in patient-derived xenografts of T-ALL. The effects of AKR1C enzyme modulation has been investigated in T-ALL cell lines and primary cultures by combining AKR1C inhibition, overexpression, and gene silencing approaches.

Results

We show that T-ALL cells overexpress AKR1C1-3 enzymes in therapy-resistant patients. We report that AKR1C1-3 enzymes play a role in the response to vincristine (VCR) treatment, also ex vivo in patient-derived xenografts. Moreover, we demonstrate that the modulation of AKR1C1-3 levels is sufficient to sensitise T-ALL cells to VCR. Finally, we show that T-ALL chemotherapeutics induce overactivation of AKR1C enzymes independent of therapy resistance, thus establishing a potential resistance loop during T-ALL combination treatment.

Conclusions

Here, we demonstrate that expression and activity of AKR1C enzymes correlate with response to chemotherapeutics in T-ALL, posing AKR1C1-3 as potential targets for combination treatments during T-ALL therapy.

Inhibition of Glycolysis and Glutaminolysis: An Emerging Drug Discovery Approach to Combat Cancer

Cancer cells have a very different metabolism from that of normal cells from which they are derived. Their metabolism is elevated, which allows them to sustain higher proliferative rate and resist some cell death signals. This phenomenon, known as the "Warburg effect", has become the focus of intensive efforts in the discovery of new therapeutic targets and new cancer drugs. Both glycolysis and glutaminolysis pathways are enhanced in cancer cells. While glycolysis is enhanced to satisfy the increasing energy demand of cancer cells, glutaminolysis is enhanced to provide biosynthetic precursors for cancer cells. It was recently discovered that there is a tyrosine phosphorylation of a specific isoform of pyruvate kinase, the M2 isoform, that is preferentially expressed in all cancer cells, which results in the generation of pyruvate through a unique enzymatic mechanism that is uncoupled from ATP production. Pyruvate produced through this unique enzymatic mechanism is converted primarily into lactic acid, rather than acetyl-CoA for the synthesis of citrate, which would normally then enter the citric acid cycle. Inhibition of key enzymes in glycolysis and glutaminolysis pathways with small molecules has provided a novel but emerging area of cancer research and has been proven effective in slowing the proliferation of cancer cells, with several inhibitors being in clinical trials. This review paper will cover recent advances in the development of chemotherapeutic agents against several metabolic targets for cancer therapy, including glucose transporters, hexokinase, pyruvate kinase M2, glutaminase, and isocitrate dehydrogenase.

Enhanced B-Raf-mediated NRF2 gene transcription and HATs-mediated NRF2 protein acetylation contributes to ABCC1-mediated chemoresistance and glutathione-mediated survival in acquired topoisomerase II poison-resistant cancer cells

Nuclear factor erythroid-2-related factor 2 (NRF2) mainly regulates transcriptional activation through antioxidant-responsive elements (AREs) present in the promoters of NRF2 target genes. Recently, we found that NRF2 was overexpressed in a KB-derived drug-resistant cancer cell panel. In this panel, KB-7D cells, which show acquired resistance to topoisomerase II (Top II) poisons, exhibited the highest NRF2 activation. To investigate whether NRF2 directly contributed to acquired resistance against Top II poisons, we manipulated NRF2 by genetic and pharmacological approaches. The result demonstrated that silencing of NRF2 by RNA interference increased the sensitivity and treatment with NRF2 activator decreased the sensitivity of KB and KB-7D cells toward Top II poisons. Further, increased B-Raf-mediated NRF2 gene transcription and HATs-mediated NRF2 protein acetylation activated NRF2 signaling in KB-7D cells. Moreover, increased binding of NRF2 to an ARE in the promoter of ATP-binding cassette subfamily C member 1 (ABCC1) directly contributed to Top II poison resistance. In addition, activation of NRF2 increased glutathione level and antioxidant capacity in KB-7D cells compared with that in KB cells; moreover, high glutathione level provided survival advantage to KB-7D cells. Our study is the first to show that aberrant NRF2 activation is via increased B-Raf-mediated NRF2 gene transcription and HATs-mediated NRF2 protein acetylation, which increases the acquired resistance and promote the survival of Top II poison-resistant cancer cells. Importantly, NRF2 downstream effectors ABCC1 and glutathione directly contribute to acquired resistance and survival, respectively. These results suggest that blockade of NRF2 signaling may enhance therapeutic efficacy and reduce the survival of Top II poison-refractory tumors in clinical.

Combined Inhibitions of Glycolysis and AKT/autophagy Can Overcome Resistance to EGFR-targeted Therapy of Lung Cancer

Efficacy of EGFR-targeted tyrosine kinase inhibitors (TKIs), such as erlotinib, to treat human non-small cell lung cancers (NSCLCs) with activating mutations in EGFR is not persistent due to drug resistance. Reprogramming in energy (especially glucose) metabolism plays an important role in development and progression of acquired resistance in cancer cells. We hypothesize that glucose metabolism in EGFR-TKI sensitive HCC827 cells and erlotinib-resistant sub-line of HCC827 (which we name it as erlotinib-resistant 6, ER6 cells in this study) is different and targeting glucose metabolism might be a treatment strategy for erlotinib-resistant NSCLCs. In this study, we found increased glucose uptakes, significant increase in glycolysis rate and overexpression of glucose transporter 1 in ER6 cells compared to its parental cells HCC827. We also found AKT and autophagy of ER6 cells were more activated than HCC827 cells after glucose starvation. Combining glucose deprivation and AKT or autophagy inhibitor could synergize and overcome the acquired resistance against EGFR-targeted therapy for NSCLCs. Our data suggest that the combinations of inhibitors of AKT or autophagy together with glucose deprivation could be novel treatment strategies for NSCLC with acquired resistance to targeted therapy.

Hormetic potential of methylglyoxal, a side-product of glycolysis, in switching tumours from growth to death

Metabolic reprogramming toward aerobic glycolysis unavoidably favours methylglyoxal (MG) and advanced glycation end products (AGEs) formation in cancer cells. MG was initially considered a highly cytotoxic molecule with potential anti-cancer value. However, we have recently demonstrated that MG enhanced tumour growth and metastasis. In an attempt to understand this dual role, we explored MG-mediated dicarbonyl stress status in four breast and glioblastoma cancer cell lines in relation with their glycolytic phenotype and MG detoxifying capacity. In glycolytic cancer cells cultured in high glucose, we observed a significant increase of the conversion of MG to D-lactate through the glyoxalase system. Moreover, upon exogenous MG challenge, glycolytic cells showed elevated amounts of intracellular MG and induced de novo GLO1 detoxifying enzyme and Nrf2 expression. Thus, supporting the adaptive nature of glycolytic cancer cells to MG dicarbonyl stress when compared to non-glycolytic ones. Finally and consistent with the pro-tumoural role of MG, we showed that low doses of MG induced AGEs formation and tumour growth in vivo, both of which can be reversed using a MG scavenger. Our study represents the first demonstration of a hormetic effect of MG defined by a low-dose stimulation and a high-dose inhibition of tumour growth.

AKR1C1 as a Biomarker for Differentiating the Biological Effects of Combustible from Non-Combustible Tobacco Products

Smoking has been established as a major risk factor for developing oral squamous cell carcinoma (OSCC), but less attention has been paid to the effects of smokeless tobacco products. Our objective is to identify potential biomarkers to distinguish the biological effects of combustible tobacco products from those of non-combustible ones using oral cell lines. Normal human gingival epithelial cells (HGEC), non-metastatic (101A) and metastatic (101B) OSCC cell lines were exposed to different tobacco product preparations (TPPs) including cigarette smoke total particulate matter (TPM), whole-smoke conditioned media (WS-CM), smokeless tobacco extract in complete artificial saliva (STE), or nicotine (NIC) alone. We performed microarray-based gene expression profiling and found 3456 probe sets from 101A, 1432 probe sets from 101B, and 2717 probe sets from HGEC to be differentially expressed. Gene Set Enrichment Analysis (GSEA) revealed xenobiotic metabolism and steroid biosynthesis were the top two pathways that were upregulated by combustible but not by non-combustible TPPs. Notably, aldo-keto reductase genes, AKR1C1 and AKR1C2, were the core genes in the top enriched pathways and were statistically upregulated more than eight-fold by combustible TPPs. Quantitative real time polymerase chain reaction (qRT-PCR) results statistically support AKR1C1 as a potential biomarker for differentiating the biological effects of combustible from non-combustible tobacco products.