ATP-binding Cassette Sub-family G Member 2 Expression Research Articles

ABCG2-Expressing Clonal Repopulating Endothelial Cells Serve to Form and Maintain Blood Vessels.

Most organs are maintained lifelong by resident stem/progenitor cells. During development and regeneration, lineage-specific stem/progenitor cells can contribute to the growth or maintenance of different organs, whereas fully differentiated mature cells have less regenerative potential. However, it is unclear whether vascular endothelial cells (ECs) are also replenished by stem/progenitor cells with EC-repopulating potential residing in blood vessels. It has been reported recently that some EC populations possess higher clonal proliferative potential and vessel-forming capacity compared with mature ECs. Nevertheless, a marker to identify vascular clonal repopulating ECs (CRECs) in murine and human individuals is lacking, and, hence, the mechanism for the proliferative, self-renewal, and vessel-forming potential of CRECs is elusive. We analyzed colony-forming, self-renewal, and vessel-forming potential of ABCG2 (ATP binding cassette subfamily G member 2)-expressing ECs in human umbilical vessels. To study the contribution of Abcg2-expressing ECs to vessel development and regeneration, we developed Abcg2CreErt2;ROSA TdTomato mice and performed lineage tracing during mouse development and during tissue regeneration after myocardial infarction injury. RNA sequencing and chromatin methylation chromatin immunoprecipitation followed by sequencing were conducted to study the gene regulation in Abcg2-expressing ECs. In human and mouse vessels, ECs with higher ABCG2 expression (ABCECs) possess higher clonal proliferative potential and in vivo vessel-forming potential compared with mature ECs. These cells could clonally contribute to vessel formation in primary and secondary recipients after transplantation. These features of ABCECs meet the criteria of CRECs. Results from lineage tracing experiments confirm that Abcg2-expressing CRECs (AbcCRECs) contribute to arteries, veins, and capillaries in cardiac tissue development and vascular tissue regeneration after myocardial infarction. Transcriptome and epigenetic analyses reveal that a gene expression signature involved in angiogenesis and vessel development is enriched in AbcCRECs. In addition, various angiogenic genes, such as Notch2 and Hey2, are bivalently modified by trimethylation at the 4th and 27th lysine residue of histone H3 (H3K4me3 and H3K27me3) in AbcCRECs. These results are the first to establish that a single prospective marker identifies CRECs in mice and human individuals, which holds promise to provide new cell therapies for repair of damaged vessels in patients with endothelial dysfunction.

Abstract 4232: Exploring chemotherapy resistance in pancreatic cancer: Insights from a 3D organoid model

Abstract Pancreatic cancer is marked by a dismal prognosis, with a 5-year survival rate at approximately 10%. A key contributor to its lethality is the development of chemotherapy resistance, followed by early metastasis. However, studies elucidating the mechanisms behind chemotherapy resistance in pancreatic cancer are limited. Previous research has relied on 2D cell line models, which present limitations, such as uniform cell types that fail to capture tumor heterogeneity and an inaccurate representation of clinical realities, wherein resistance often develops gradually rather than through continuous exposure to high drug concentrations. In this study, we developed a more sophisticated organoid model of chemotherapy resistance. Six organoids from three patients were matched to study chemotherapy resistance in a personalized context. Comprehensive whole-exome sequencing and transcriptomic analyses were performed, along with an examination of chemotherapy resistance protein expression and EMT-related markers. Notably, differential expression levels of CK19 and Vimentin were observed between samples. Our analysis also focused on the expression of the ATP-Binding Cassette Subfamily G Member 2 (ABCG2) gene in chemoresistant organoids. Western blot analysis indicated a significant increase in ABCG2 expression in these organoids compared to controls. According to the Moffitt RNA signature, the primary and corresponding chemoresistant organoids retained their molecular subtype classifications both before and after developing chemoresistance. Gene set enrichment analysis uncovered significant upregulation of pathways related to DNA repair and cell cycle regulation, particularly the G2M checkpoint, in chemoresistant organoids. Furthermore, gene ontology functional analysis suggested a notable overrepresentation of activities related to amino acid transmembrane transport and extracellular matrix constituents, underscoring their potential role in the chemoresistance phenotype. Citation Format: Hee Seung Lee. Exploring chemotherapy resistance in pancreatic cancer: Insights from a 3D organoid model [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 4232.

Exposure to anticancer drugs modulates the expression of ACSL4 and ABCG2 proteins in adrenocortical carcinoma cells

Adrenocortical carcinoma (ACC) is a rare and malignant disease, with more than 50 % of patients developing hormone-secreting tumors. These tumors are genetically heterogeneous and potentially lethal, as metastasis is often underway at the time of diagnosis. While chemoresistance can be multifactorial, Acyl CoA synthetase 4 (ACSL4) is known to contribute to the generation of highly aggressive cellular phenotypes, while increased expression and activity of multidrug transporters such as ATP-binding cassette subfamily G member 2 (ABCG2) are known to play a key role. Therefore, the objective of this work was to determine changes in the expression of ACSL4 and ABCG2 in ACC cell lines after exposure to antitumor drugs. Bioinformatics analysis of public database GSE140818 revealed higher ACSL4 and ABCG2 expression in HAC15 cells resistant to mitotane when compared to wild type cells. In addition, our studies revealed an increase in ACSL4 and ABCG2 expression in lowly aggressive H295R cells undergoing early treatment with non-lethal concentrations of mitotane, doxorubicin and cisplatin. Comparable results were obtained in lowly aggressive breast cancer cells MCF-7. The increase in ACSL4 and ABCG2 expression favored tumor cell viability, proliferation and compound efflux, an effect partially offset by ACSL4 and ABCG2 inhibitors. These results provide relevant data on the undesired molecular effects of antitumor drugs and may fuel future studies on patients’ early response to antitumor treatment.

Study on the mechanism of Orthosiphon aristatus (Blume) Miq. in the treatment of hyperuricemia by microbiome combined with metabonomics

Ethnopharmacological relevanceGrowing evidence indicates that hyperuricemia is closely associated with gut microbiota dysbiosis. Orthosiphon aristatus (Blume) Miq. (O. aristatus), as a traditional Chinese medicine, has been widely used to treat hyperuricemia in China. However, the mechanism by which O. aristatus treats hyperuricemia has not been clarified. Aim of the studyIn this study, we investigated whether the molecular mechanism underlying the anti-hyperuricemia effect of O. aristatus is related to the regulation of gut microbiota by 16S rDNA gene sequencing combined with widely targeted metabolomics. Materials and methodsHyperuricemia was induced in rats by administration of 10% fructose and 20% yeast, and the uricosuric effect was assessed by measuring the uric acid (UA) levels in serum and cecal contents. Intestinal morphology was observed by hematoxylin and eosin (HE) staining. To explore the effects of O. aristatus on the gut microbiota and its metabolites, we utilized 16S rDNA gene sequencing combined with widely targeted metabolomics. Furthermore, metabolic pathway enrichment analysis was performed on the screened differential metabolites. The real time quantitative polymerase chain reaction (RT-PCR) and western blotting (WB) were used to detect the expression of relevant proteins in the key pathway. ResultsOur results indicated that O. aristatus intervention decreased serum UA levels and increased the UA levels in cecal contents in hyperuricemic rats. Additionally, O. aristatus improved intestinal morphology and altered the composition of the gut microbiota and its metabolites. Specifically, 16S rDNA revealed that O. aristatus treatment significantly reduced the abundance of unidentified-Ruminococcaceae and Lachnospiraceae-NK4A136-group. Meanwhile, widely targeted metabolomics showed that 17 metabolites, including lactose, 4-oxopentanoate and butyrate, were elevated, while 55 metabolites, such as flavin adenine dinucleotide and xanthine, were reduced. Metabolic pathway enrichment analysis found that O. aristatus was mainly involved in purine metabolism. Moreover, RT-PCR and WB suggested that O. aristatus could significantly up-regulate the expression of UA excretion transporter ATP-binding cassette subfamily G member 2 (ABCG2) in the intestine. ConclusionO. aristatus exerts UA-lowering effect by regulating the gut microbiota and ABCG2 expression, indicating that this herb holds great promise in the treatment of hyperuricemia.

Photodynamic therapy with zinc phthalocyanine enhances the anti-cancer effect of tamoxifen in breast cancer cell line: Promising combination treatment against triple-negative breast cancer?

Photodynamic therapy (PDT) is a light-based anti-neoplastic therapeutic approach. Growing evidence indicates that combining conventional anti-cancer therapies with PDT can be a promising approach to treat malignancies. Herein, we aimed to investigate anti-cancer effects of the combination treatment of zinc phthalocyanine (ZnPc)-PDT with tamoxifen (TA) on MDA-MB-231 cells (as a triple-negative breast cancer (TNBC) cell line). For this purpose, we investigated the cytotoxicity of TA and ZnPc-PDT on MDA-MB-231 cells performing the MTT assay. The effect of TA and ZnPc-PDT on the apoptosis of MDA-MB-231 cells was studied using Annexin V/PI and DAPI staining. The wound-healing assay, and colony formation assay were performed to study the effect of TA and ZnPc-PDT on the migration, and clonogenicity of MDA-MB-231 cells, respectively. The qRT-PCR was done to study the gene expression of caspase-8, caspase-9, caspase-3, ZEB1, ROCK1, SNAIL1, CD133, CD44, SOX2, and ABCG2 (ATP-binding cassette sub-family G member 2). Based on our results, monotherapies with TA and ZnPc-PDT can remarkably increase cell cytotoxicity effects, stimulate apoptosis via downregulating Bcl-2 and upregulating caspase-3 and caspase-9, inhibit migration via downregulating SNAIL1 and ZEB1, and suppress clonogenicity via downregulating SOX2 and CD44 in MDA-MB-231 cells. Besides, these monotherapies can downregulate the expression of ABCG2 in MDA-MB-231 cells. Nevertheless, the combination treatment can potentiate the above-mentioned anti-cancer effects compared to monotherapy with TA. Of interest, the combined treatment of TA with ZnPc-PDT can synergically increase cell cytotoxicity effects on MDA-MB-231 cells. In fact, synergistic effects were estimated by calculation of Combination Index (CI); that synergistic outcomes were observed in all groups. Also, this combination treatment can significantly upregulate the caspase-8 gene expression and downregulate ROCK1 and CD133 gene expression in MDA-MB-231 cells. Overall, our results show that ZnPc-PDT can more sensitize the MDA-MB-231 cells to TA treatment. Based on our knowledge and experiment, the synergistic effects of ZnPc-PDT and TA deserve further evaluation in cancer research.

Pyroglutamylproline purified from fermented barley extract increases ABCG2 expression in Caco-2 cells

Fermented barley extract P (FBEP) prepared from barley shochu distillation by-product has been reported to lower serum uric acid (UA) by increasing urinary excretion of UA. ATP-binding cassette subfamily G member 2 (ABCG2) is a transporter responsible for UA efflux from the intestinal tract and kidneys. This study aimed to identify, among the compounds isolated from FBEP using high-performance liquid chromatography, the components that promote ABCG2 expression in Caco-2 cells. Pyroglutamylproline (pEP) increased the expression of ABCG2 in Caco-2 cells at the gene and protein levels. These results suggest that the pEP contained in FBEP may decrease serum UA levels by increasing the expression of urate efflux transporters in the intestinal epithelium and promoting UA excretion.

A Pan-Cancer Landscape of ABCG2 across Human Cancers: Friend or Foe?

Emerging evidence from research or clinical studies reported that ABCG2 (ATP-binding cassette sub-family G member 2) interrelates with multidrug resistance (MDR) development in cancers. However, no comprehensive pan-cancer analysis is available at present. Therefore, we explore multiple databases, such as TCGA to investigate the potential therapeutic roles of ABCG2 across 33 different tumors. ABCG2 is expressed on a lower level in most cancers and shows a protective effect. For example, a lower expression level of ABCG2 was detrimental to the survival of adrenocortical carcinoma (TCGA-ACC), glioblastoma multiforme (GBM), and kidney renal clear cell carcinoma (KIRC) patients. Distinct associations exist between ABCG2 expression and stemness scores, microenvironmental scores, microsatellite instability (MSI), and tumor mutational burden (TMB) of tumor patients. We observed a significant positive correlation between the ABCG2 mutation site and prognosis in uterine corpus endometrial carcinoma (UCEC) patients. Moreover, transmembrane transporter activity and hormone biosynthetic-associated functions were found to be involved in the functionality of ABCG2 and its related genes. The cDNAs of cancer cell lines were collected to detect exon mutation sequences and to analyze ABCG2 mRNA expression. The mRNA expression level of ABCG2 showed a significant difference among spheres and drug-resistant cancer cell lines compared with their corresponding adherent cancer cell lines in six types of cancer. This pan-cancer study provides, for the first time, a comprehensive understanding of the multifunctionality of ABCG2 and unveils further details of the potential therapeutic role of ABCG2 in pan-cancer.

NRBP1 modulates uric acid transporter ABCG2 expression by activating the Wnt/β-catenin pathway in HK-2 cells

BackgroundNuclear receptor binding protein 1 (NRBP1) and ATP-binding cassette subfamily G member 2 (ABCG2) was the gout risk gene and high-capacity urate exporter respectively. However, the relationship between NRBP1 and ABCG2 and the underlying molecular mechanism contributing to these associations are unknown. MethodsFirstly, the efficiency of the overexpression and knockdown of NRBP1 was confirmed by western blot. Next, the effect of NRBP1 overexpression and knockdown on the expression of ABCG2, organic anion transporter 1 (OAT1), glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) was detected by qRT-PCR and western blot. At the same time, the cellular location of ABCG2 and its expression after NRBP1 overexpression and knockdown was tested by immunofluorescence (IF) staining. Then, the mechanism of NRBP1 modulates ABCG2 expression was evaluated by western blot with or without the β-catenin inhibitor (21H7). ResultsThe lentivirus system was used to generate stable NRBP1 overexpression, while the plasmids carrying a NRBP1 siRNA was generated to knockdown NRBP1 expression in HK-2 cells. Meanwhile, the overexpression of NRBP1 significantly decreased the mRNAs and proteins expression of GLUT9 and URAT1, while the knockdown of NRBP1 increased the mRNAs and proteins expression of ABCG2 significantly. In addition, the NRBP1 modulates the expression of ABCG2 was by ctivating the Wnt/β-catenin pathway in HK-2 cells according to the IF and western blot results. ConclusionTaken together, our study demonstrated that NRBP1 inhibition played an essential role in attenuating hyperuricemia and gout by upregulation of ABCG2 via Wnt/β-catenin signaling pathway in HK-2 cells.

Quinacrine and Curcumin in combination decreased the breast cancer angiogenesis by modulating ABCG2 via VEGF A.

Cancer stem cells (CSCs) cause drug resistance in cancer due to its extensive drug efflux, DNA repair and self-renewal capability. ATP binding cassette subfamily G member 2 (ABCG2) efflux pump afford protection to CSCs in tumors, shielding them from the adverse effects of chemotherapy. Although the role of ABCG2 in cancer progression, invasiveness, recurrence are known but its role in metastasis and angiogenesis are not clear. Here, using in vitro (CSCs enriched side population [SP] cells), ex vivo (patient derived primary cells), in ovo (fertilized egg embryo) and in vivo (patient derived primary tissue mediated xenograft (PDX)) system, we have systematically studied the role of ABCG2 in angiogenesis and the regulation of the process by Curcumin (Cur) and Quinacrine (QC). Cur + QC inhibited the proliferation, invasion, migration and expression of representative markers of metastasis and angiogenesis. Following hypoxia, ABCG2 enriched cells released angiogenic factor vascular endothelial growth factor A (VEGF A) and induced the angiogenesis via PI3K-Akt-eNOS cascade. Cur + QC inhibited the ABCG2 expression and thus reduced the angiogenesis. Interestingly, overexpression of ABCG2 in SP cells and incubation of purified ABCG2 protein in media induced the angiogenesis but knockdown of ABCG2 decreased the vascularization. In agreement with in vitro results, ex vivo data showed similar phenomena. An induction of vascularization was noticed in PDX mice but reduction of vascularization was also observed after treatment of Cur + QC. Thus, data suggested that in hypoxia, ABCG2 enhances the production of angiogenesis factor VEGF A which in turn induced angiogenesis and Cur + QC inhibited the process by inhibiting ABCG2 in breast cancer.

ABCG2, CD44 and SOX9 are increased with the acquisition of drug resistance and involved in cancer stem cell activities in head and neck squamous cell carcinoma cells.

Cancer stem cells are a sub-population of cancer cells with self-renewal activity that play key roles in tumor resistance to chemotherapy and radiation. Several cancer stem cell markers have been identified to correlate with clinical prognosis. However, which marker is associated with which cancer stem cell characteristic is unclear. The present study aimed to clarify the relationship between cancer stem cell markers associated with drug resistance acquisition and the characteristics of cancer stem cells. We generated cisplatin-resistant head and neck squamous cell carcinoma cells by culturing cells in increasing concentrations of cisplatin. The cisplatin-resistant head and neck squamous cell carcinoma cells also acquired multidrug resistance and were named resistant HSC-3 (R HSC-3) cells. R HSC-3 showed no differences in cell proliferation or cell cycle distributions compared with parental cells. R HSC-3 cells showed increased drug excretion ability and elevated expression of ATP-binding cassette subfamily G member 2 (ABCG2), a drug excretion pump. R HSC-3 cells also highly expressed CD44, a cancer stem cell marker, and exhibited enhanced cell invasion and spheroid formation abilities. Furthermore, the stem cell-related factor SRY-box transcription factor 9 (SOX9) was identified as increased in R HSC-3 cells by microarray analysis. Knockdown experiments showed that SOX9 and ABCG2 were involved in the drug excretion ability of R HSC3 cells and ABCG2 was involved in the spheroid formation ability of R HSC-3 cells. These results indicate that CD44, SOX9 and ABCG2 expression levels were enhanced in head and neck squamous cell carcinoma cells that acquired multidrug resistance and that these molecules are important for maintaining cancer stem cell characteristics. Overall, regulating CD44, SOX9 and ABCG2 may be a strategy to inhibit cancer stem cells.

Combinatorial Anticancer Drug Screen Identifies Off-Target Effects of Epigenetic Chemical Probes.

Anticancer drug response is determined by genetic and epigenetic mechanisms. To identify the epigenetic regulators of anticancer drug response, we conducted a chemical epigenetic screen using chemical probes that target different epigenetic modulators. In this screen, we tested 31 epigenetic probes in combination with 14 mechanistically diverse anticancer agents and identified 8 epigenetic probes that significantly potentiate the cytotoxicity of TAK-243, a first-in-class ubiquitin-activating enzyme (UBA1) inhibitor evaluated in several solid and hematologic malignancies. These probes are TP-472, GSK864, A-196, UNC1999, SGC-CBP30, and PFI-4 (and its related analogues GSK6853 and GSK5959), and they target BRD9/7, mutant IDH1, SUV420H1/2, EZH2/1, p300/CBP, and BRPF1B, respectively. In contrast to epigenetic probes, negative control compounds did not have a significant impact on TAK-243 cytotoxicity. Potentiation of TAK-243 cytotoxicity was associated with reduced ubiquitylation and induction of apoptosis. Mechanistically, these epigenetic probes exerted their potentiation by inhibiting the efflux transporter ATP-binding cassette subfamily G member 2 (ABCG2) without inducing significant changes in the ubiquitylation pathways or ABCG2 expression levels. As assessed by docking analysis, the identified probes could potentially interact with ABCG2. Based on these data, we have developed a cell-based assay that can quantitatively evaluate ABCG2 inhibition by drug candidates. In conclusion, our study identifies epigenetic probes that profoundly potentiate TAK-243 cytotoxicity through off-target ABCG2 inhibition. We also provide experimental evidence that several negative control compounds cannot exclude a subset of off-target effects of chemical probes. Finally, potentiation of TAK-243 cytotoxicity can serve as a quantitative measure of ABCG2-inhibitory activity.

Perphenazine and prochlorperazine decrease glioblastoma U‑87 MG cell migration and invasion: Analysis of the ABCB1 and ABCG2 transporters, E‑cadherin, α‑tubulin and integrins (α3, α5, and β1) levels

Glioblastoma multiforme is the most frequent type of malignant brain tumor, and is one of the most lethal and untreatable human tumors with a very poor survival rate. Therefore, novel and effective strategies of treatment are required. Integrins play a crucial role in the regulation of cellular adhesion and invasion. Integrins and α-tubulin are very important in cell migration, whereas E-cadherin plays a main role in tumor metastasis. Notably, drugs serve a crucial role in glioblastoma treatment; however, they have to penetrate the blood-brain barrier (BBB) to be effective. ABC transporters, including ATP binding cassette subfamily B member 1 (ABCB1) and ATP binding cassette subfamily G member 2 (ABCG2), are localized in the brain endothelial capillaries of the BBB, have a crucial role in the development of multidrug resistance and are modulated by phenothiazine derivatives. The impact of perphenazine and prochlorperazine on the motility of human Uppsala 87 malignant glioma (U87-MG) cells was evaluated using a wound-healing assay, cellular migration and invasion were assessed by Transwell assay, and the protein expression levels of ABCB1, ABCG2, E-cadherin, α-tubulin and integrins were determined by western blotting. The present study explored the effects of perphenazine and prochlorperazine on the levels of ABCB1, ABCG2, E-cadherin, α-tubulin and integrins (α3, α5, and β1), as well as on the migratory and invasive ability of U87-MG cells. The results suggested that perphenazine and prochlorperazine may modulate the expression levels of multidrug resistance proteins (they decreased ABCB1 and increased ABCG2 expression), E-cadherin, α-tubulin and integrins, and could impair the migration and invasion of U-87 MG cells. In conclusion, the decrease in migratory and invasive ability following treatment with phenothiazine derivatives due to the increase in ABCG2 and E-cadherin expression, and decrease in α-tubulin and integrins expression, may suggest that research on perphenazine and prochlorperazine in the treatment of glioblastoma is worth continuing.

Methionine restriction enhances the chemotherapeutic sensitivity of colorectal cancer stem cells by miR-320d/c-Myc axis.

Chemotherapy resistance of colorectal cancer stem cells (CRC-SCs) has become a major challenge in clinical treatment of cancer. Methionine restriction (MR) enhances the therapeutic effect of chemotherapeutic agents. The aim of this study was to explore the molecular pathways that MR affects the chemotherapeutic sensitivity of CRC-SCs. CD133+ and CD133- SW480 or SW620 cells were isolated by magnetic-activated cell sorting (MACS). Mouse xenograft tumor model was established by subcutaneous inoculation of CD133+ SW480. MTT assay was used to detect cell viability. Phase distribution of cell cycle was detected by flow cytometry. Western blotting was used to detect drug-resistant related protein expression. miR-320d and transcription factor c-Myc expressions were detected by qRT-PCR. The interaction between miR-320d and c-Myc was verified by luciferase assay. CD133+ SW480 and SW620 cells were more resistant to 5-fluorouracil (5-FU) than CD133- cells. In vitro and in vivo experiments showed that 5-FU and MR combined therapy further inhibited CD133+ cell activity and ATP binding cassette subfamily G member 2 (ABCG2) expression, and reduced tumor volume compared with drug administration alone. Interference with miR-320d or overexpression of c-Myc reversed the increased chemotherapeutic sensitivity of CRC-SCs induced by synergistic therapy with 5-FU and MR. miR-320d can target and regulate c-Myc. Interference with c-Myc could reverse the increase in cell viability and ABCG2 expression caused by down-regulation of miR-320d. In conclusion, the combined chemotherapy with MR can enhance the chemotherapeutic sensitivity of CRC-SCs by up-regulation of miR-320d to inhibit c-Myc expression, which lays a molecular basis for MR regulation of chemotherapeutic sensitivity of CRC-SCs.

The Cisplatin, 5-fluorouracil, Irinotecan, and Gemcitabine Treatment in Resistant 2D and 3D Model Triple Negative Breast Cancer Cell Line: ABCG2 Expression Data.

Chemotherapeutics have been commonly used in cancer treatment. In this study, the effects of Cisplatin, 5-fluorouracil, Irinotecan, and Gemcitabine have been evaluated on two-dimensional (2D) (sensitive and resistance) cell lines and three dimensional (3D) spheroid structure of MDA-MB- 231. The 2D cell culture lacks a natural tissue-like structural so, using 3D cell culture has an important role in the development of effective drug testing models. Furthermore, we analyzed the ATP Binding Cassette Subfamily G Member 2 (ABCG2) gene and protein expression profile in this study. We aimed to establish a 3D breast cancer model that can mimic the in vivo 3D breast cancer microenvironment. The 3D spheroid structures were multiplied (globally) using the three-dimensional hanging drop method. The cultures of the parental cell line MDA-MB-231 served as the controls. After adding the drugs in different amounts, we observed a clear and well-differentiated spheroid formation for 24 h. The viability and proliferation capacity of 2D (sensitive and resistant) cell lines and 3D spheroid cell treatment were assessed by the XTT assay. Cisplatin, Irinotecan, 5-Fu, and Gemcitabine-resistant MDA-MB-231 cells were observed to begin to disintegrate in a three-dimensional clustered structure at 24 hours. Additionally, RT-PCR and protein assay showed overexpression of ABCG2 when compared to the parental cell line. Moreover, MDA-MB-231 cells grown in 3D showed decreased sensitivity to chemotherapeutics treatment. More resistance to chemotherapeutics and altered gene expression profile were shown in 3D cell cultures when compared with the 2D cells. These results might play an important role to evaluate the efficacy of anticancer drugs to explore the mechanisms of MDR in the 3D spheroid forms.

NRBP1 modulates uric acid transporter ABCG2 expression by activating the Wnt/β-catenin pathway in HK-2 cells

BackgroundNuclear receptor binding protein 1 (NRBP1) and ATP-binding cassette subfamily G member 2 (ABCG2) was the gout risk gene and high-capacity urate exporter respectively. However, the relationship between NRBP1 and ABCG2 and the underlying molecular mechanism contributing to these associations are unknown. MethodsFirstly, the efficiency of the overexpression and knockdown of NRBP1 was confirmed by western blot. Next, the effect of NRBP1 overexpression and knockdown on the expression of ABCG2, organic anion transporter 1 (OAT1), glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) was detected by qRT-PCR and western blot. At the same time, the cellular location of ABCG2 and its expression after NRBP1 overexpression and knockdown was tested by immunofluorescence (IF) staining. Then, the mechanism of NRBP1 modulates ABCG2 expression was evaluated by western blot with or without the β-catenin inhibitor (21H7). ResultsThe lentivirus system was used to generate stable NRBP1 overexpression, while the plasmids carrying a NRBP1 siRNA was generated to knockdown NRBP1 expression in HK-2 cells. Meanwhile, the overexpression of NRBP1 significantly decreased the mRNAs and proteins expression of GLUT9 and URAT1, while the knockdown of NRBP1 increased the mRNAs and proteins expression of ABCG2 significantly. In addition, the NRBP1 modulates the expression of ABCG2 was by ctivating the Wnt/β-catenin pathway in HK-2 cells according to the IF and western blot results. ConclusionTaken together, our study demonstrated that NRBP1 inhibition played an essential role in attenuating hyperuricemia and gout by upregulation of ABCG2 via Wnt/β-catenin signaling pathway in HK-2 cells.

Good response to methotrexate is associated with a decrease in the gene expression of ABCG2, a drug transporter, in patients with rheumatoid arthritis

Objectives Methotrexate (MTX) is used as an anchor drug in the treatment of rheumatoid arthritis (RA), although more than a half of the patients with RA require additional treatments. We designed a prospective study involving two medical centers in Japan to examine the association between the expression of MTX-related genes including a drug transporter ATP-binding cassette sub-family G member 2 (ABCG2) gene and the clinical response to MTX in MTX-naive patients with RA. Methods The primary endpoint of this study was good response based on the European League Against Rheumatism (EULAR) response criteria by Disease Activity Score using 28-joint count (DAS28). We evaluated the association between the baseline expression of six genes involved in the intracellular pharmacokinetics of MTX, including ABCG2, as well as their temporal changes, and the clinical response at week 12 from the initiation of MTX. Results Based on the clinical response at 12 weeks after the initiation of MTX, 24 patients were classified into good responders (n = 9) and non-good responders (n = 15; 10 moderate responders and 5 non-responders) groups. A univariate logistic regression analysis of the baseline gene expression levels to predict the EULAR good response at week 12 showed a significant association with ABCG2 expression alone. Furthermore, the rate of baseline expression of ABCG2 mRNA above the cut-off value determined using a receiver operating characteristic curve was higher in good responders than in non-good responders (p = .012). Moreover, ABCG2 expression decreased in almost all good responders, but not in non-good responders, after MTX treatment for 12 weeks (median −76% vs. +41% from baseline, respectively; p = .011). The ABCG2 expression level did not correlate with DAS28 at baseline or week 12. Conclusions Our study revealed that good response to MTX is associated with a decrease in the expression of ABCG2 in patients with RA.

A Combined Bioinformatic and Nanoparticle-Based Study Reveal the Role of ABCG2 in the Drug Resistant Breast Cancer.

ATP-Binding Cassette subfamily G member 2 (ABCG2) is a semi-transport protein that plays a key role in human diseases, including bladder cancer and lung cancer, and maybe resistant to chemotherapy drugs. The present study aimed to determine the role and underlying mechanisms of breast cancer resistance protein (ABCG2) in breast cancer and to study the reversal effect of inhibiting ABCG2 expression on the drug resistance of breast cancer cells and provide new ideas for gene-targeted therapy of breast cancer. The structure and genomic alterations of ABCG2 were systematically investigated using GeneCards and cBioPortal to reveal the genetic alterations (including amplification and deep deletions) of ABCG2. We performed the correlation between ABCG2 expression and clinicopathological parameters using the data in bc-GenExMiner 4.4. Then, the protein-protein interaction and functional enrichment analysis of ABCG2 were performed based on the STRING, bc-GenExMiner 4.4, and Enrichr databases. Besides, we analyzed the pathway activity of genes that interact with ABCG2 using GSCALite and PharmGKB. Using magnetic nanoparticles polyMAG as the carrier of ABCG2-siRNA, polyMAG-ABCG2-siRNA was transfected into the Doxorubicin (DOX)-resistant breast cancer cell line MCF-7/ADR and directly into the tumors in nude mice. Patent US20150328485 points out that magnetic nanoparticles can be attached to an anti-cancer drug, such as an antibody-based anti-cancer drug. We found a statistically significant correlation between ABCG2 expression and clinicopathological parameters, such as Estrogen Receptor (ER), Progesterone Receptor (PR), and human epidermal growth factor receptor-2 (HER2), and nodal status in breast cancer patients. ABCG2 is closely related to SLC2A9, KIT, ABCG1, and MRPS7, which suggests that these proteins may be functional partners of breast cancer. The expression of ABCG2 is correlated with the activation or inhibition of multiple oncogenic pathways. Moreover, we found that ABCG2 is involved in the DOX signaling pathway. The small interfering RNA (siRNA) carried by magnetic nanoparticles can reduce the expression of ABCG2, thereby significantly improving the therapeutic effect of DOX on tumors. Our findings provide a more in-depth understanding of ABCG2 as a biomarker for predicting DOX-resistance and insights into the development of related therapeutic targets in breast cancer.

Estradiol regulates intestinal ABCG2 to promote urate excretion via the PI3K/Akt pathway

ObjectivesThe study of sex differences in hyperuricemia can provide not only a theoretical basis for this clinical phenomenon but also new therapeutic targets for urate-lowering therapy. In the current study, we aimed to confirm that estradiol can promote intestinal ATP binding cassette subfamily G member 2 (ABCG2) expression to increase urate excretion through the PI3K/Akt pathway.MethodsThe estradiol levels of hyperuricemia/gout patients and healthy controls were compared, and a hyperuricemia mouse model was used to observe the urate-lowering effect of estradiol and the changes in ABCG2 expression in the kidney and intestine. In vivo and in vitro intestinal urate transport models were established to verify the urate transport function regulated by estradiol. The molecular pathway by which estradiol regulates ABCG2 expression in intestinal cells was explored.ResultsThe estradiol level of hyperuricemia/gout patients was significantly lower than that of healthy controls. Administering estradiol benzoate (EB) to both male hyperuricemic mice and female mice after removing the ovaries confirmed the urate-lowering effect of estradiol, and hyperuricemia and estradiol upregulated the expression of intestinal ABCG2. Estradiol has been confirmed to promote urate transport by upregulating ABCG2 expression in intestinal urate excretion models in vivo and in vitro. Estradiol regulates the expression of intestinal ABCG2 through the PI3K/Akt pathway.ConclusionOur study revealed that estradiol regulates intestinal ABCG2 through the PI3K/Akt pathway to promote urate excretion, thereby reducing serum urate levels.

Dihydrotestosterone Induces Chemo-Resistance of Triple-Negative Breast MDA-MB-231 Cancer Cells Towards Doxorubicin Independent of ABCG2 and miR-328-3p.

Androgens potentially have an important role in the biology of breast cancer, particularly triple-negative breast cancer (TNBC). Androgen receptor (AR) may offer a novel therapeutic strategy, including the use of microRNA (miRNA) molecules. We have previously shown that AR agonist, dihydrotestosterone (DHT), increases the expression of miR-328-3p in the TNBC MDA-MB-231 cells. One target of the latter miRNA is ATP-binding cassette subfamily G member 2 (ABCG2), which modulates the chemo-response of cancer cells by pumping out xenobiotics. Using MDA-MB-231 cells as a model system for TNBC, we hypothesized that DHT would induce cell sensitivity towards doxorubicin via increasing levels of miR-328-3p and, consequently, reducing ABCG2 levels. Chemo-response of cells towards doxorubicin, tamoxifen, and mitoxantrone was evaluated using cell viability MTT assay. Cells were transfected with both miR-328-3p mimic or antisense molecules. Real-time PCR was utilized to assess RNA levels and immunoblotting was performed to investigate levels of ABCG2 protein. PCR arrays were used to assess changes in the expression of drug response regulatory genes. Contrary to our hypothesis, treating MDA-MB-231 cells with DHT no effect towards tamoxifen or mitoxantrone, increased cell resistance towards doxorubicin was noted, concomitant with decreased expression of ABCG2. This under-expression of ABCG2 was also found in MCF-7 and MDA-MB-453 cells treated with DHT. Although miR-328-3p decreased ABCG2 mRNA and protein levels, the miRNA did not alter the chemo-response of cells towards doxorubicin and did not affect DHT-induced chemo-resistance. AR activation slightly decreased the expression of 5 genes, including insulin-like growth factor 1 receptor that may explain the mechanism of DHT-induced chemo-resistance of cells. DHT regulates chemo-response via a mechanism independent of ABCG2 and miR-328-3p.

Investigation of MRP1 and ABCG2 Gene Expression in Chronic Myeloid Leukemia (CML) Patients

Background: This study evaluated and compared the quantitative expression of multidrug resistance-associated protein 1 (MRP1) and ATP-binding cassette subfamily G member 2 (ABCG2), two Multidrug Resistance (MDR) related genes, in 30 CML patients and 27 normal subjects.
 Methods: Total RNA was isolated from peripheral blood mononuclear cells (MNCs) using the Trizol reagent. Then cDNAs were synthesized. Gene expression was quantified using Real-Time PCR System. The relative expression of target genes was calculated using the 2-ΔΔCt method.
 Results: High expression of MRP1 and ABCG2 mRNAs were detected in the patient group. Intra-group comparisons also revealed increased expression of ABCG2 in Accelerated Phase (AP)-Blastic Crisis (BC) patients compared to Chronic Phase (CP) patients. At the same time, the increased expression of MRP1 in AP-BC patients was not statistically significant.
 Conclusion: Considering the broad spectrum of ATP Binding Cassette (ABC) transporter superfamily substrates, they can play an essential role in cell fate determination. High expression of MRP1 and ABCG2 genes can result in the efflux of therapeutic agents and subsequent reduction in their intracellular concentration. This mechanism finally protects cells from the therapeutic effects of medications. On the other hand, these transporters can export growth factors out of the cell. Such exported molecules may have a growth-inducing effect on adjacent cells. These are the possible mechanisms for the participation of MRP1 and ABCG2 genes in conferring drug resistance to CML cells.