Overexpression Of Transporters Research Articles

Abstract LB260: Overexpression of ABCC1 and ABCG2 confers resistance to talazoparib, a poly polymerase inhibitor

Abstract Aims: The overexpression of ABC transporters on cancer cell membranes is one of the most common causes of multidrug resistance (MDR). This study investigates the impact of ABCC1 and ABCG2 on the resistance to talazoparib (BMN-673), a potent poly (ADP-ribose) polymerase (PARP) inhibitor, in ovarian cancer treatment. Methods: The cell viability test was used to indicate the effect of talazoparib in different cell lines. Computational molecular docking analysis was conducted to simulate the interaction between talazoparib and ABCC1 or ABCG2. The mechanism of talazoparib resistance was investigated by constructing talazoparib-resistant subline A2780/T4 from A2780 through drug selection with gradually increasing talazoparib concentration. Results: Talazoparib cytotoxicity decreased in drug-selected or gene-transfected cell lines overexpressing ABCC1 or ABCG2 but can be restored by ABCC1 or ABCG2 inhibitors. Talazoparib competitively inhibited substrate drug efflux activity of ABCC1 or ABCG2. Upregulated ABCC1 and ABCG2 protein expression on the plasma membrane of A2780/T4 cells enhances resistance to other substrate drugs, which could be overcome by the knockout of either gene. In vivo experiments confirmed the retention of drug-resistant characteristics in tumor xenograft mouse models. Conclusions: The therapeutic efficacy of talazoparib in cancer may be compromised by its susceptibility to MDR, which is attributed to its interactions with the ABCC1 or ABCG2 transporters. The overexpression of these transporters can potentially diminish the therapeutic impact of talazoparib in cancer treatment. Citation Format: Shuo Fang, Xiaona Fang. Overexpression of ABCC1 and ABCG2 confers resistance to talazoparib, a poly polymerase inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB260.

Membrane-Fusing Vehicles for Re-Sensitizing Transporter-Mediated Multiple-Drug Resistance in Cancer.

Reversing the multiple drug resistance (MDR) arising from the overexpression of the efflux transporters often fails mainly due to the high toxicity or the poor water solubility of the inhibitors of these transporters. Here, we demonstrate the delivery of an inhibitor targeting three ABC transporters (ABCB1, ABCC1 and ABCG2) directly to the cell membrane using membrane-fusing vehicles (MFVs). Three different transfected MDCK II cell lines, along with parental cells, were used to investigate the inhibitory effect of cyclosporine A (CsA) in solution versus direct delivery to the cell membrane. CsA-loaded MFVs successfully reversed MDR for all three investigated efflux transporters at significantly lower concentrations compared with CsA in solution. Results showed a 15-fold decrease in the IC50 value for ABCB1, a 7-fold decrease for ABCC1 and an 11-fold decrease for ABCG2. We observed binding site specificity for ABCB1 and ABCG2 transporters. Lower concentrations of empty MFVs along with CsA contribute to the inhibition of Hoechst 33342 efflux. However, higher concentrations of CsA along with the high amount of MFVs activated transport via the H-binding site. This supports the conclusion that MFVs can be useful beyond their role as delivery systems and also help to elucidate differences between these transporters and their binding sites.

Abstract 7193: ABCB1-mediated chemotherapeutic drug resistance is reversed by a potent p53-MDM2 inhibitor NVP-HDM201

Abstract The failure of chemotherapy in cancer persists as a result of overexpression of various ATP-binding cassette (ABC) transporters. ABCB1 is one such transporter that actively pumps out chemotherapeutic drugs and it is one of the reasons for multidrug resistance (MDR). In the last few years, activation of p53 has been targeted as a therapeutic strategy in the treatment of cancers. Siremadlin (NVP-HDM201) is a potent and selective inhibitor of p53-MDM2 interaction. The objective of this study was to explore the ability of HDM201 to reverse tumor MDR attributable to overexpression of ABC transporters. According to our findings, HDM201 significantly increased the sensitivity of ABCB1-overexpressing cells to ABCB1 substrates, such as colchicine and doxorubicin. We found that HDM201 reverses ABCB1-mediated MDR by interacting with ABCB1 and blocking its function without affecting the expression and cellular localization of ABCB1. Moreover, HDM201 promoted the accumulation of paclitaxel in cell lines that overexpress ABCB1. At both high and low doses, HDM201 increased the ATPase activity of ABCB1. The computational support for the cross-reactivity of this p53 inhibitor with human ABCB1 comes from docking simulation results that align with the binding conformation of HDM201 within the vast cavity of the transmembrane region of ABCB1. In conclusion, by blocking the transport function of ABCB1, HDM201 can reverse ABCB1-mediated MDR in vitro. Citation Format: Harsh Patel, Chaoyun Cai, Zhuoxun Wu, Qiuxu Teng, Hanli Li, Zhe-Sheng Chen. ABCB1-mediated chemotherapeutic drug resistance is reversed by a potent p53-MDM2 inhibitor NVP-HDM201 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7193.

Abstract 5875: Upregulation of the RNA binding protein HuR by cancer-secreted exosome to mediate multidrug resistance

Abstract Background and Aim: Multidrug resistance (MDR) is an unresolved obstacle to cancer chemotherapy. It is usually caused by overexpression of drug efflux transporters including ABCG2. Exosomes are extracellular lipid vesicles released from all cells upon the fusion of multivesicular bodies with plasma membrane. Tumor-derived exosomes have been shown to mediate cell-to-cell transfer of oncogenic materials to promote drug resistance. Human antigen R (HuR) is an extensively studied RNA binding protein that regulates the stability, translation, and nucleus-to-cytoplasm shuttling of mRNAs. Numerous HuR-targeting mRNAs play crucial roles in tumorigenesis, invasion and metastasis. We have previously reported the induction of ABCG2 and MDR phenotype by HuR overexpression in colon cancer. HuR overexpression is linked with high-grade malignancy and poor prognosis in cancer patients. This study investigated the enrichment of HuR inducing microRNAs (miRNAs) in exosomes secreted from MDR colon cancer and its intracellular transfer to drive MDR. Method: Cancer exosome-mediated transfer of miRNAs from ABCG2-overexpressing resistant colon cancer cells S1M1-80 to a few sensitive colon cell lines was evaluated. Exosomes were isolated from S1M1-80 conditioned medium by differential centrifugation method. The uptake of fluorescence-labeled exosome from donor MDR cancer cells by recipient sensitive cells was visualized by fluorescence microscopy. MiRNA microarray was conducted to identify differentially expressed miRNAs in drug sensitive cells after incubation with S1M1-80-secreted exosomes. Western blot and qPCR analysis were conducted to measure HuR and ABCG2 expression. Result: Exosomes were isolated from resistant S1M1-80 cells, whose purity was confirmed by the presence of exosomal markers (Tsg101 and Alix) but absence of cellular marker (GRP78) by Western blot analysis. These exosomes reduced the apoptotic effect of SN-38 or 5-fluorouracil in sensitive colon cancer cell lines (HCT116, S1, and SW480) by inducing both HuR and ABCG2. A common upregulated miRNA (miR-155-5p) was identified by miRNA microarray in the sensitive cell lines after incubation with S1M1-80-derived exosomes. MiR-155-5p was found to induce HuR expression by promoting its translation. MiR-155-5p inhibitor was shown to reverse the upregulation of HuR in HCT116 cells after exosome incubation, which subsequently suppressed ABCG2 expression and the MDR phenotype. Furthermore, inhibition of exosome uptake by dynasore was found to prevent the induction of HuR/ABCG2, and re-sensitize the exosome-treated sensitive cells to SN38. Conclusion: MDR cells-derived exosomes may spread the drug resistance phenotype by transferring a miR-155-5p/HuR/ABCG2 regulatory machinery to sensitive cells. Inhibition of this exosomal transfer of regulatory materials may prevent the spread of MDR and sensitize cancer cells to chemotherapy. Citation Format: Kenneth K.W. To. Upregulation of the RNA binding protein HuR by cancer-secreted exosome to mediate multidrug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5875.

Abstract 4648: Metabolic vulnerabilities of drug-resistant melanoma with therapeutic potential

Abstract Melanoma has been at the center of revolutions in both targeted BRAF therapy and immune therapy. However, the resistance to current therapeutic drugs has been a formidable obstacle to continuing benefit to patients. Overcoming resistance and new therapeutic agents and strategies are the primary goals of current cancer research. We currently found that metabolic pathways altered significantly in BRAFi-resistant melanoma. We hypothesized that BRAFi-resistant melanoma rewires its metabolic routes to reach its needs in energy and biosynthetic precursors, both essential for escaping the BRAFi attack. We found that five amino acids transporters and metabolic enzymes (ASNS, slc7a11, slc7a5, slc3a2, slc4a7) were the significant increase in resistant melanoma. Knockdown by shRNA or knockout by crispr/cas9 of these amino acids transporters or/and metabolic enzymes enhanced the sensitivity of BRAFi resistant melanoma to BRAFi. In contrast, overexpression of these amino acid transporters or/and metabolic enzymes promoted the ability of resistance of BRAFi in parent melanoma cells. Moreover, the inhibition of these amino acid transporters and metabolic enzymes by small molecular inhibitors significantly attenuated the resistance of the BRAFi-resistant melanoma whereas less affected the parent melanoma. Notably, we confirmed that blocking these amino acid transporters and metabolic enzymes by shRNA and/or small molecular inhibitors could rescue the sensitivity of resistant melanoma cells and inhibit resistant-melanoma cell growth in the preclinical mouse model in vivo. Importantly, we found that overexpression of slc7a11, slc7a5 and slc3a2 correlated with worse survival in melanoma in SK-TCGA data. Our findings uncovered the mechanism of how metabolic reprogramming fueled melanoma cell growth and proliferation for escaping drug attacks and offered a rational strategy to guide clinical treatment. The identified novel molecular proteins represented a promising therapeutic target for BRAF mutant melanoma patients with resistance to current therapy. Citation Format: Yanlin Yu, Lei Huang, Weiping Chen, Glenn Merlino. Metabolic vulnerabilities of drug-resistant melanoma with therapeutic potential [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4648.

A Review of Approaches to Potentiate the Activity of Temozolomide against Glioblastoma to Overcome Resistance.

A glioblastoma (GBM) is one of the most aggressive, infiltrative, and treatment-resistant malignancies of the central nervous system (CNS). The current standard of care for GBMs include maximally safe tumor resection, followed by concurrent adjuvant radiation treatment and chemotherapy with the DNA alkylating agent temozolomide (TMZ), which was approved by the FDA in 2005 based on a marginal increase (~2 months) in overall survival (OS) levels. This treatment approach, while initially successful in containing and treating GBM, almost invariably fails to prevent tumor recurrence. In addition to the limited therapeutic benefit, TMZ also causes debilitating adverse events (AEs) that significantly impact the quality of life of GBM patients. Some of the most common AEs include hematologic (e.g., thrombocytopenia, neutropenia, anemia) and non-hematologic (e.g., nausea, vomiting, constipation, dizziness) toxicities. Recurrent GBMs are often resistant to TMZ and other DNA-damaging agents. Thus, there is an urgent need to devise strategies to potentiate TMZ activity, to overcome drug resistance, and to reduce dose-dependent AEs. Here, we analyze major mechanisms of the TMZ resistance-mediated intracellular signaling activation of DNA repair pathways and the overexpression of drug transporters. We review some of the approaches investigated to counteract these mechanisms of resistance to TMZ, including the use of chemosensitizers and drug delivery strategies to enhance tumoral drug exposure.

Baicalein induces apoptosis by inhibiting the glutamine-mTOR metabolic pathway in lung cancer

IntroductionBaicalein, a bioactive component of Scutellaria baicalensis Georgi, has been shown to promote apoptosis in non-small cell lung cancer cells. However, previous studies have not determined if baicalein exerts proapoptotic effects by modulating the metabolic pathways. ObjectiveTo investigate if baicalein induces apoptosis in lung cancer cells by modulating the glutamine-mTOR metabolic pathway. MethodsThe in vivo anti-lung cancer activity of baicalein (50, 100, and 200 mg/kg) was evaluated using a xenograft model. In vitro experiments were used to assess the efficacy of baicalein (for H1299: 12.5, 25, and 50 μM; for A549: 10, 20, and 40 μM) on lung cancer cell proliferation, colony formation, and apoptosis. Metabolomics analysis was performed using liquid chromatography-mass spectrometry. The binding of baicalein to glutamine transporters and glutaminase was examined using molecular docking. The overexpression of glutamine transporters was validated using qRT–PCR and western blot analyses. The levels of ASCT2, LAT1, GLS1, p-mTOR, mTOR, and apoptosis-related proteins were evaluated using western blot analysis. ResultsBaicalein inhibited lung cancer xenograft tumor growth in vivo and suppressed proliferation and promoted apoptosis in lung cancer cells in vitro. Additionally, baicalein altered amino acid metabolites, especially glutamine metabolites, in H1299 and A549 cells. Mechanistically, baicalein interacted with glutamine transporters as well as glutaminase and inhibited their activation. The expression of mTOR, an apoptosis-related protein and downstream target of glutamine metabolism, was also inhibited by baicalein treatment. Importantly, we next demonstrated the suppression of mTOR signaling and the induction of apoptosis by baicalein were achieved by regulating glutamine metabolism. ConclusionBaicalein inhibited the mTOR signaling pathway and induced apoptosis by downregulating glutamine metabolism. The potential of baicalein to induce apoptosis in lung cancer cells by selectively targeting the glutamine-mTOR pathway suggests an encouraging approach for treating lung cancer.

Unraveling the Genetic Adaptations in Cell Surface Composition and Transporters of Lactiplantibacillus plantarum for Enhanced Acid Tolerance.

This study employed adaptive laboratory evolution to improve the acid tolerance of Lactiplantibacillus plantarum, a vital strain in food fermentation and a potential probiotic. Phenotype and genomic analyses identified the overexpression of stress response proteins, ATP synthases, and transporters as pivotal in conferring acid tolerance to the evolved strains. These adaptations led to a shorter lag phase, improved survival rates, and higher intracellular pH values compared to the wild-type strain under acid stress conditions. Additionally, the evolved strains showed an increased expression of genes in the fatty acid synthesis pathway, resulting in a higher production of unsaturated fatty acids. The changes in cell membrane composition possibly prevented H+ influx, while mutant genes related to cell surface structure contributed to observed elongated cells and thicker cell surface. These alterations in cell wall and membrane composition, along with improved transporter efficiency, were key factors contributing to the enhanced acid tolerance in the evolved strains.

Understanding Cancer's Defense against Topoisomerase-Active Drugs: A Comprehensive Review.

In recent years, the emergence of cancer drug resistance has been one of the crucial tumor hallmarks that are supported by the level of genetic heterogeneity and complexities at cellular levels. Oxidative stress, immune evasion, metabolic reprogramming, overexpression of ABC transporters, and stemness are among the several key contributing molecular and cellular response mechanisms. Topo-active drugs, e.g., doxorubicin and topotecan, are clinically active and are utilized extensively against a wide variety of human tumors and often result in the development of resistance and failure to therapy. Thus, there is an urgent need for an incremental and comprehensive understanding of mechanisms of cancer drug resistance specifically in the context of topo-active drugs. This review delves into the intricate mechanistic aspects of these intracellular and extracellular topo-active drug resistance mechanisms and explores the use of potential combinatorial approaches by utilizing various topo-active drugs and inhibitors of pathways involved in drug resistance. We believe that this review will help guide basic scientists, pre-clinicians, clinicians, and policymakers toward holistic and interdisciplinary strategies that transcend resistance, renewing optimism in the ongoing battle against cancer.

Drug Resistance in Hepatocellular Carcinoma: Theoretical Basis and Therapeutic Aspects.

Primary liver cancer is one of the most common malignant tumors with high mortality and increasing incidence worldwide. Currently, chemotherapy is an important comprehensive treatment for moderate or advanced liver cancer. Despite the effective therapeutic effects initially achieved by chemotherapy, the high phenotypic and molecular heterogeneity of liver cancer cells facilitates resistance to conventional chemotherapy or targeted therapy and even leads to multidrug resistance (MDR), which is one of the major obstacles for clinical chemotherapy. Drug resistance exhibits multiple and complex molecular mechanisms to antagonize therapy under pharmacological pressure, including overexpression of drug efflux transporters, downstream adaptive response (such as apoptosis, autophagy, and endoplasmic reticulum stress), dysfunction of DNA damage repair (DDR), epigenetic modification, tumor microenvironment (TME) as well as extracellular matrix (ECM). In this paper, we summarize the recent research progress and intervention strategies for drug resistance in hepatocellular carcinoma (HCC), which will provide a promising therapeutic strategy for overcoming MDR in liver cancer.

Fertility protection: a novel approach using pretreatment with mesenchymal stem cell exosomes to prevent chemotherapy–induced ovarian damage in a mouse model

BackgroundPrimary ovarian insufficiency (POI) refers to the loss of ovarian functionbefore the age of 40 years and results in amenorrhea and infertility. POI has diverse causes, but a common cause is exposure to gonadotoxic chemotherapy for cancer treatment. Due to the risk of developing POI, patients who want to preserve their fertility may consider various procedures for fertility preservation. However, current fertility preservation options are highly invasive, carry substantial risks, and have uncertain success rates. Recent studies from our group and others reported that mesenchymal stem cells (MSCs) and MSC-derived exosomes can restore ovarian functions in preclinical models of POI by restoring damaged cells and inhibiting apoptosis. Although the restorative effect of MSC-derived exosomes has been well reported in previous studies, the potential of MSC-derived exosomes for preventing ovarian damage has not been fully elucidated. ObjectiveWe hypothesized that the antiapoptotic potential of MSC-derived exosomes may protect ovarian tissue from chemotherapy-induced damage. Study designIn this study, we delivered MSC-derived exosomes directly into mouse ovaries before chemotherapy. Sixty mice were divided into three groups (20 per group), which were labeled the control, CTx (chemotherapy), and FP (fertility protection) groups. Only the FP group mice received exosomes, while the control and CTx group mice received saline. After exosome injection, the CTx and FP groups of mice were subjected to chemotherapy treatment to induce ovarian damage. After chemotherapy, we evaluated the protective effects of exosome treatment on ovarian function, such as estrus cyclicity, serum hormone levels, and the fertility rate, by comparing these outcomes between the CTx and FP groups. These outcomes were also compared with those of the control group for comparison with outcomes under healthy conditions. ResultsAfter intraovarian injection of exosomes before chemotherapy, the mice were able to maintain their estrus cycle (4–5-day cyclicity), serum AMH level (66.06±26.40 ng/ml, not significantly different from that of the healthy controls), folliculogenesis (32.2±11.3 in the CTx group/46.4±14.1 in the FP group, p<0.05), steroidogenesis marker StAR gene expression (0.44±0.11-fold in the CTx group and 0.88±0.31-fold in the FP group, p<0.05), and fertility (2 of 8 in the CTx group and 5 of 8 in the FP group), preventing chemotherapy-induced damage. We found that exosome treatment before chemotherapy can preserve ovarian function and protect fertility through the overexpression of ABC transporters, such as ABCB1b (10.17±17.75-fold in the CTx group and 44.14±33.25-fold in the FP group; p<0.05), and ABCC10 (3.25±0.59-fold in the CTx group and 5.36±1.86-fold in the FP group; p<0.05). ConclusionIn this study, we present a novel fertility protection method using MSC-derived exosomes. We conclude that MSC-derived exosomes are a promising simple treatment option for fertility protection in reproductive-age patients receiving gonadotoxic chemotherapy.

Comparative transcriptome analysis reveals the contribution of amino acid transporters to acid tolerance in Lactococcus lactis

AbstractAmino acid transporters are promising targets for engineering acid‐tolerant strains of Lactococcus lactis. However, the simple overexpression of transporters alone is insufficient to achieve a highly acid‐resistant phenotype. This study investigated the effects of amino acid transporters on the acid‐stress tolerance of L. lactis. Here, we first verified the contribution of amino acid transporters to acid tolerance by overexpressing the ctrA, glnP, and glnQ genes in L. lactis. Transcriptome analysis revealed that most genes associated with specific amino acid transport, pyrimidine metabolism, and functional proteins, were upregulated in the overexpression strains. Among them, arginine biosynthesis (argG and argH), amino acid transport (yjeM and azlC), and pyrimidine metabolism were considered to be the most important regulatory mechanisms. Importantly, metabolite profiling revealed that the overexpression strains had higher intracellular levels of amino acids, particularly aspartate, glutamate, and arginine at low pH, as well as higher intracellular ATP levels, which was consistent with the corresponding gene‐expression levels. Finally, the simultaneous overexpression of glnP and glnQ led to a further improvement of acid tolerance in L. lactis. This study reveals the regulatory mechanisms of amino acid transporters, and provides a novel strategy for achieving higher acid tolerance via positive tandem expression approaches.

Nanomaterials as targeted delivery system of therapeutics for inhibition of cancer

Cancer, a disease with complex pathological process, is the principal cause of mortality and morbidity throughout the world. Conventional chemotherapy faces drawbacks regarding its low bioavaiability, insolubility, high dose requirements, low therapeutic indices, cytotoxicity, multiple drug resistance-development, biological barriers related obstruction, and non-specific targeting. Cancer drug resistance includes over-expression of drug efflux transporters, hypoxic environment, and defective apoptotic pathways. To overcome these discrepancies, a lot of nanomaterials (NMs), as emerging delivery system, have attracted attention for carrying and delivering therapeutics to the desired sites of interest. For improving the targeting potential of the anticancer cargos, NMs are optimized for their sizes, shapes, and surfaces for enhancing their circulation time and targeting efficiency. The NMs through encapsulation or conjugation of cargos with ligands may target them to the cancer site/s with enhanced therapeutic efficacy in a controlled release manner. Generally, NMs, as cancer therapy, are utilized to target cancer cells, tumor microenvironment, and immune system mainly through enhanced permeability and retention (EPR) effect¸­ stimuli-responsive targeting or modifying their surfaces with targeting ligands such as transferin, integrins, sugar, folic acid and antibodies for the enhancement of tissue targeting recognition and their internalization. This review demonstrates mainly the biomedical applications of NMs as delivery vehicles or systems functionalized with ligands and therapeutic agents to target cancer cells / tissues passively, actively or physically with higher inhibitory therapeutic efficacies against cancer.&#x0D; Keywords: Cancer; Conventional chemotherapy; Nanomaterials; Biomedical applications; Therapeutic targeting; Inhibitory therapeutic efficacies

PH-Responsive Polypropylene Sulfide Magnetic Nanocarrier-Mediated Chemo-Hyperthermia Kills Breast Cancer Stem Cells by Long-Term Reversal of Multidrug Resistance and Chemotherapy Resensitization.

Cancer stem cells (CSCs) present a formidable challenge in cancer treatment due to their inherent resistance to chemotherapy, primarily driven by the overexpression of ABC transporters and multidrug resistance (MDR). Despite extensive research on pharmacological small-molecule inhibitors, effectively managing MDR and improving chemotherapeutic outcomes remain elusive. On the other hand, magnetic hyperthermia (MHT) holds great promise as a cancer therapeutic, but there is limited research on its potential to reverse MDR in breast CSCs and effectively eliminate CSCs through combined chemo-hyperthermia. To address these gaps, we developed tumor microenvironment-sensitive, drug-loaded poly(propylene sulfide) (PPS)-coated magnetic nanoparticles (PPS-MnFe). These nanoparticles were employed to investigate hyperthermia sensitivity and MDR reversion in breast CSCs, comparing their performance to that of small-molecule inhibitors. Additionally, we explored the efficacy of combined chemo-hyperthermia in killing CSCs. CSC-enriched breast cancer cells were subjected to low-dose MHT at 42 °C for 30 min and then treated with the chemical MDR inhibitor salinomycin (SAL). The effectiveness of each treatment in inhibiting MDR was assessed by measuring the efflux of the MDR substrate, rhodamine 123 (R123) dye. Notably, MHT induced a prolonged reversal of MDR activity compared with SAL treatment alone. After successfully inhibiting MDR, the breast CSCs were exposed to chemotherapy using paclitaxel to trigger synergistic cell death. The combination of MHT and chemotherapy demonstrated remarkable reductions in stemness properties, MDR reversal, and the effective eradication of breast CSCs in this innovative dual-modality approach.

Overexpression of astrocytic glutamate transporters alleviates hyperexcitability in mouse model of Alzheimer’s Disease

AbstractBackgroundAstrocytes are the main cells responsible for clearing glutamate from the synapse; their glutamate transporters quickly and efficiently clear glutamate within the synaptic cleft, preventing neuronal excitotoxicity. In mouse models and human cases of Alzheimer’s Disease (AD), the astrocyte‐specific glutamate transporter (Glt1 in rodents and EAAT2 in humans) is decreased. Our goal is to study the effects of decreased glutamate transporters on synaptic measures of function and plasticity.MethodUsing a 5XFAD mouse model of amyloid pathology, we utilized an adeno‐associated virus (AAV) to over‐express Glt1 in the hippocampus. Electrophysiological field recordings examined the role of astrocyte‐specific glutamate transporters in synaptic plasticity and hyperexcitability. Animals received injections of AAV‐Luciferase (control) in one hippocampus, and AAV‐Glt1a in the contralateral hippocampus. Field recordings were performed to assess excitatory postsynaptic potentials in the hippocampal CA1 stratum radiatum elicited by stimulation of CA3 axons.ResultCompared to control (AAV‐Luciferase), AAV‐Glt1 significantly increased the expression of glutamate transporters in hippocampal tissue. We then compared measures of neuronal hyperexcitability, synaptic strength, and long‐term synaptic potentiation. Results indicate that there is more hyperexcitability in control tissues compared to AAV‐Glt injections, as evident by decreased population spike thresholds.ConclusionOthers have reported hippocampal hyperexcitability may lead to memory impairment; in human cases of AD it is thought to encourage epileptic episodes. By using our AAV‐directed technique to increase glutamate transporters, and thus reduce network hyperexcitability, we will be able to examine how reactive astrocytes and their loss of glutamate transporters contribute to memory or cognition loss. Ongoing studies will do exactly this‐ use a mouse model of AD with and without AAV Glt1 overexpression to determine changes in behavioral cognitive outcome measures that may be attributed to hyperexcitability in neuronal networks.

Overexpression of ABCC1 and ABCG2 confers resistance to talazoparib, a poly (ADP-Ribose) polymerase inhibitor

AimsThe overexpression of ABC transporters on cancer cell membranes is one of the most common causes of multidrug resistance (MDR). This study investigates the impact of ABCC1 and ABCG2 on the resistance to talazoparib (BMN-673), a potent poly (ADP-ribose) polymerase (PARP) inhibitor, in ovarian cancer treatment. MethodsThe cell viability test was used to indicate the effect of talazoparib in different cell lines. Computational molecular docking analysis was conducted to simulate the interaction between talazoparib and ABCC1 or ABCG2. The mechanism of talazoparib resistance was investigated by constructing talazoparib-resistant subline A2780/T4 from A2780 through drug selection with gradually increasing talazoparib concentration. ResultsTalazoparib cytotoxicity decreased in drug-selected or gene-transfected cell lines overexpressing ABCC1 or ABCG2 but can be restored by ABCC1 or ABCG2 inhibitors. Talazoparib competitively inhibited substrate drug efflux activity of ABCC1 or ABCG2. Upregulated ABCC1 and ABCG2 protein expression on the plasma membrane of A2780/T4 cells enhances resistance to other substrate drugs, which could be overcome by the knockout of either gene. In vivo experiments confirmed the retention of drug-resistant characteristics in tumor xenograft mouse models. ConclusionsThe therapeutic efficacy of talazoparib in cancer may be compromised by its susceptibility to MDR, which is attributed to its interactions with the ABCC1 or ABCG2 transporters. The overexpression of these transporters can potentially diminish the therapeutic impact of talazoparib in cancer treatment.

Sucralose regulates postprandial blood glucose in mice through intestinal sweet taste receptors Tas1r2/Tas1r3.

Non-nutritive sweeteners (such as sucralose) bind to sweet receptors Tas1r2/Tas1r3 on intestinal endocrine L cells after diets to upregulate blood glucose. However, the mechanism by which sucralose regulates postprandial blood glucose (PBG) has not been clarified to date. We hypothesized that the gut sweet taste receptor was one of the targets for sucralose to regulate PBG. The aim of this study was to examine the effect of sucralose on PBG based on the gut sweet taste receptor signaling pathway and to explore the mechanism. Therefore, we examined PBG, genes, and proteins associated with the gut sweet receptor pathway in sucralose-exposed mice. The results showed that after 12 weeks of sucralose exposure the PBG of mice increased significantly, and the expression of intestinal sweet taste receptors increased correspondingly. Within the concentration range of this experiment, a significant increase of PBG was observed in mice fed on sucralose with a concentration equal to or higher than 0.33 g L-1 . Long-term consumption of sucralose may increase body weight and the risk of elevated PBG, resulting in overexpression of sweetness receptors and glucose transporters. The mechanism of these effects might be the result of non-nutritive sweeteners binding to sweetness receptors Tas1r2/Tas1r3 in gut endocrine cells and upregulating Slc5a1 and Slc2a2. But we cannot rule out that the rise in PBG is the result of a combination of sweet receptors and gut microbes. Therefore, the effect of gut microbes on PBG needs to be studied further. © 2023 Society of Chemical Industry.

Exploring imidazo[4,5-g]quinoline-4,9-dione derivatives as Acinetobacter baumannii efflux pump inhibitor: an in silico approach

Antimicrobial resistance (AMR) is fast becoming a medical crisis affecting the entire global population. World Health Organization (WHO) statistics show that globally 0.7 million people are dying yearly due to the emergence of AMR. By 2050, the expected number of lives lost will be 10 million per year. Acinetobacter baumannii is a dreadful nosocomial pathogen that has developed multidrug resistance (MDR) to several currently prescribed antibiotics worldwide. Overexpression of drug efflux transporters (DETs) is one of the mechanisms of multidrug resistance (MDR) in Acinetobacter baumannii. Therefore, blocking the DET can raise the efficacy of the existing antibiotics by increasing their residence time inside the bacteria. In silico screening of five synthetic compounds against three drug efflux pump from A. baumannii has identified KSA5, a novel imidazo[4,5-g]quinoline-4,9-dione derivative, to block the efflux of antibiotics. Molecular docking and simulation results showed that KSA5 could bind to adeB, adeG, and adeJ by consistently interacting with ligand-binding site residues. KSA5 has a higher binding free energy and a lower HOMO-LUMO energy gap than PAβN, suggesting a better ability to interact and inhibit DETs. Further analysis showed that KSA5 is a drug-like molecule with optimal physicochemical and ADME properties. Hence, KSA5 could be combined with antibiotics to overcome antimicrobial resistance. Communicated by Ramaswamy H. Sarma

I-CBP112 declines overexpression of ATP-binding cassette transporters and sensitized drug-resistant MDA-MB-231 and A549 cell lines to chemotherapy drugs

Despite extensive efforts and ongoing progress in personalized anticancer approaches, chemotherapy remains the first line or the only treatment for some tumors that may develop resistance to chemotherapeutics in time due to inter alia overexpression of ATP-binding cassette transporters. Using clinically-relevant resistant models of triple negative breast cancer (MDA-MB-231; TNBC) as well as non-small cell lung cancer (A549; NSCLC), we tested the efficacy of I-CBP112 – CBP/EP300 bromodomain inhibitor to overcome drug resistance by declining ABC gene transcription. I-CBP112 significantly reduced ABCB1, ABCC1, ABCC2, ABCC3, ABCC5 and ABCG2 in all resistant lines, as well as ABCC10 in TNBC and ABCC4 in paclitaxel-resistant NSCLC, thereby increasing intracellular drug accumulation and cytotoxicity in 2D and 3D cultures. This was phenocopied only by the joint effect of ABC inhibitors such as tariquidar (ABCB1 – P-glycoprotein and ABCG2) and MK-571 (ABCC), whereas single inhibition of ABCB1/ABCG2 or ABCC proteins did not affect drug accumulation, thereby implying the need of simultaneous deficiency in activity of majority of drug pumps for enhanced drug retention. I-CBP112 failed to directly inhibit activity of ABCB1, ABCG2 and ABCC subfamily members at the same time. Importantly, I-CBP112 treated cancer cells polarized human macrophages into proinflammatory phenotypes. Moreover, I-CBP112 remained non-toxic to primary cell lines, nor did it enhance anticancer drug toxicity to blood-immune cells. In silico assay of ADMET properties confirmed the desired pharmacokinetic features of I-CBP112. The results suggest that the CBP/p300 inhibitor is a promising co-adjuvant to chemotherapy in drug-resistant cancer phenotypes, capable of decreasing ABC transporter expression.

Glycolipids from Sargassum filipendula, a Natural Alternative for Overcoming ABC Transporter-Mediated MDR in Cancer.

Chemotherapy is a widely used strategy to treat cancer, a disease that causes millions of deaths each year. However, its efficacy is reduced by the overexpression of ABC transporters, which are proteins that expel the drugs used in chemotherapy and involved in the multidrug resistance (MDR). Glycolipids have been identified as potential inhibitors of ABC transporters. Algae of the genus Sargassum contain high levels of glycolipids, making them a promising therapeutic alternative against the MDR phenotype. Sargassum filipendula glycolipids were obtained by exhaustive maceration with chloroform/methanol, purified by column and thin layer chromatography, and then characterized by FTIR, NMR, and LC-MS. Cell viability by PI labeling and inhibition of ABC transporters were analyzed by flow cytometry. Assessment of resistance reversal was determined by MTT assay. Ten sulfoquinovosylglycerol-type compounds were found, and six of them are reported for the first time. In particular, moiety 4 (GL-4) showed strong and moderate inhibitory activity against ABCC1 and ABCB1 transporters respectively. Treatment of GL-4 in combination with the antineoplastic drug vincristine sensitized Lucena-1 cell model to drug and reversed the MDR phenotype. This is the first report of glycolipids isolated from S. filipendula capable of inhibiting ABC transporters and thus overcoming acquired drug resistance.