Impacts of ABCG2 loss of function variant (p. Gln141Lys, c.421 C > A, rs2231142) on lipid levels and statin efficiency: a systematic review and meta-analysis.

BACKGROUND: The latest evidence indicates that ATP-binding cassette superfamily G member 2 (ABCG2) is critical in regulating lipid metabolism and mediating statin or cholesterol efflux. This study investigates whether the function variant loss within ABCG2 (rs2231142) impacts lipid levels and statin efficiency. METHODS: PubMed, Cochrane Library, Central, CINAHL, and ClinicalTrials.gov were searched until November 18, 2023. RESULTS: Fifteen studies (34,150 individuals) were included in the analysis. The A allele [Glu141Lys amino acid substitution was formed by a transversion from cytosine (C) to adenine (A)] of rs2231142 was linked to lower levels of high-density lipoprotein cholesterol (HDL-C), and higher levels of low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC). In addition, the A allele of rs2231142 substantially increased the lipid-lowering efficiency of rosuvastatin in Asian individuals with dyslipidemia. Subgroup analysis indicated that the impacts of rs2231142 on lipid levels and statin response were primarily in Asian individuals. CONCLUSIONS: The ABCG2 rs2231142 loss of function variant significantly impacts lipid levels and statin efficiency. Preventive use of rosuvastatin may prevent the onset of coronary artery disease (CAD) in Asian individuals with dyslipidemia.

Extracellular Vesicles as Surrogates for the Regulation of the Drug Transporters ABCC2 (MRP2) and ABCG2 (BCRP).

Drug efflux transporters of the ATP-binding-cassette superfamily play a major role in the availability and concentration of drugs at their site of action. ABCC2 (MRP2) and ABCG2 (BCRP) are among the most important drug transporters that determine the pharmacokinetics of many drugs and whose overexpression is associated with cancer chemoresistance. ABCC2 and ABCG2 expression is frequently altered during treatment, thus influencing efficacy and toxicity. Currently, there are no routine approaches available to closely monitor transporter expression. Here, we developed and validated a UPLC-MS/MS method to quantify ABCC2 and ABCG2 in extracellular vesicles (EVs) from cell culture and plasma. In this way, an association between ABCC2 protein levels and transporter activity in HepG2 cells treated with rifampicin and hypericin and their derived EVs was observed. Although ABCG2 was detected in MCF7 cell-derived EVs, the transporter levels in the vesicles did not reflect the expression in the cells. An analysis of plasma EVs from healthy volunteers confirmed, for the first time at the protein level, the presence of both transporters in more than half of the samples. Our findings support the potential of analyzing ABC transporters, and especially ABCC2, in EVs to estimate the transporter expression in HepG2 cells.

Clinical assessment of momelotinib drug-drug interactions via CYP3A metabolism and transporters.

Momelotinib-approved for treatment of myelofibrosis in adults with anemia-and its major active metabolite, M21, were assessed as drug-drug interaction (DDI) victims with a strong cytochrome P450 (CYP) 3A4 inhibitor (multiple-dose ritonavir), an organic anion transporting polypeptide (OATP) 1B1/1B3 inhibitor (single-dose rifampin), and a strong CYP3A4 inducer (multiple-dose rifampin). Momelotinib DDI perpetrator potential (multiple-dose) was evaluated with CYP3A4 and breast cancer resistance protein (BCRP) substrates (midazolam and rosuvastatin, respectively). DDI was assessed from changes in maximum plasma concentration (Cmax), area under the concentration-time curve (AUC), time to reach Cmax, and half-life. The increase in momelotinib (23% Cmax, 14% AUC) or M21 (30% Cmax, 24% AUC) exposure with ritonavir coadministration was not clinically relevant. A moderate increase in momelotinib (40% Cmax, 57% AUC) and minimal change in M21 was observed with single-dose rifampin. A moderate decrease in momelotinib (29% Cmax, 46% AUC) and increase in M21 (31% Cmax, 15% AUC) were observed with multiple-dose rifampin compared with single-dose rifampin. Due to potentially counteracting effects of OATP1B1/1B3 inhibition and CYP3A4 induction, multiple-dose rifampin did not significantly change momelotinib pharmacokinetics compared with momelotinib alone (Cmax no change, 15% AUC decrease). Momelotinib did not alter the pharmacokinetics of midazolam (8% Cmax, 16% AUC decreases) or 1'-hydroxymidazolam (14% Cmax, 16% AUC decreases) but increased rosuvastatin Cmax by 220% and AUC by 170%. Safety findings were mild in this short-term study in healthy volunteers. This analysis suggests that momelotinib interactions with OATP1B1/1B3 inhibitors and BCRP substrates may warrant monitoring for adverse reactions or dose adjustments.

ABCG2 polymorphisms and susceptibility to ARV-associated hepatotoxicity.

BACKGROUND: The ABCG2 421C/A polymorphism contributes significantly to the distribution and absorption of antiretroviral (ARV) regimens and is associated with the undesirable side effects of efavirenz. METHODS: To investigate this, we examined ABCG2 34G/A (rs2231137) and 421C/A (rs2231142) genetic variations in 149 HIV-infected patients (116 without hepatotoxicity, 33 with ARV-induced hepatotoxicity) and 151 healthy controls through the PCR-restriction fragment length polymorphism (PCR-RFLP) technique. RESULTS AND DISCUSSION: The ABCG2 34GA genotype and 34A allele indicated a risk for antiretroviral therapy-associated hepatotoxicity development (p = 0.09, OR = 1.58, 95% CI: 0.93-2.69; p = 0.06, OR = 1.50, 95% CI: 0.98-2.30). The haplotype GA was associated with hepatotoxicity (p = 0.042, OR = 2.37, 95% CI: 1.04-5.43; p = 0.042, OR = 2.49, 95% CI: 1.04-5.96). Moreover, when comparing HIV patients with hepatotoxicity to healthy controls, the haplotype GA had an association with an elevated risk for the development of hepatotoxicity (p = 0.041, OR = 1.73, 95% CI: 1.02-2.93). Additionally, the association of the ABCG2 34GA genotype with the progression of HIV (p = 0.02, OR = 1.97, 95% CI: 1.07-3.63) indicated a risk for advanced HIV infection. Furthermore, the ABCG2 421AA genotype was linked to tobacco users and featured as a risk factor for the progression of HIV disease (p = 0.03, OR = 11.07, 95% CI: 1.09-270.89). CONCLUSION: The haplotype GA may enhance the risk of hepatotoxicity development and its severity. Individuals with the ABCG2 34A allele may also be at risk for the development of hepatotoxicity. Additionally, individuals with an advanced stage of HIV and the ABCG2 34GA genotype may be at risk for disease progression.

IFN­Î³ induces apoptosis in gemcitabine­resistant pancreatic cancer cells.

Pancreatic ductal adenocarcinoma (PDAC) is the most prevalent and aggressive form of pancreatic cancer. Gemcitabine (GEM), the first­line treatment for PDAC, which alleviates symptoms and enhances the quality of life of patients. However, it is prone to lead to the development of drug resistance during treatment. Interferon (IFN)­Î³ exhibits antitumor and immunomodulatory properties. The present study aimed to explore the impact of IFN­Î³ on the viability, migration and apoptosis of GEM­resistant pancreatic cancer cells. Firstly, a GEM­resistant pancreatic cancer cell line, named PANC­1/GEM, was constructed. Hematoxylin and eosin staining analyzed the cell morphology, whereas reverse transcription­quantitative PCR (RT­qPCR) assessed the expression levels of the drug­resistance genes multidrug resistance­associated protein (MRP) and breast cancer resistance protein (BCRP). The MTT assay and cell counting techniques were used to determine the appropriate concentration of IFN­y and its effects on cell viability. The IFN­Î³­induced apoptosis of PANC­1/GEM cells was assessed using an Apoptosis Detection Kit, whereas the impact of IFN­Î³ on the migration of these cells was evaluated using a wound­healing assay. The MTT assay revealed a resistance index of 22.4 in the PANC­1/GEM cell line. RT­qPCR indicated that, compared with in wild­type cells, the PANC­1/GEM resistant strain exhibited lower MRP and higher BCRP mRNA expression levels. The optimal concentration of IFN­Î³ for affecting PANC­1/GEM cells was determined to be 0.3 µg/ml. At this concentration, IFN­Î³ induced PANC­1/GEM cell apoptosis, along with a notable reduction in migration. Following treatment of PANC­1/GEM cells with IFN­Î³, MRP expression increased whereas BCRP mRNA expression decreased, indicating a reversal in their drug­resistance gene expression. In conclusion, IFN­Î³ exhibited antitumor immune properties by upregulating MRP and downregulating BCRP expression, reversing drug­resistance gene expression, and reducing cell viability and migration, while promoting apoptosis in PANC­1/GEM cells. IFN­Î³ could potentially serve as a treatment option for patients with GEM­resistant pancreatic cancer.

Clinical Analysis and in Vitro Correlation of BCRP-Mediated Drug-Drug Interaction in the Gastrointestinal Tract.

Breast cancer resistance protein (BCRP) is a drug efflux transporter expressed on the epithelial cells of the small intestine and on the lateral membrane of the bile duct in the liver; and is involved in the efflux of substrate drugs into the gastrointestinal lumen and secretion into bile. Recently, the area under the plasma concentration-time curve (AUC) of rosuvastatin (ROS), a BCRP substrate drug, has been reported to be increased by BCRP inhibitors, and BCRP-mediated drug-drug interaction (DDI) has attracted attention. In this study, we performed a ROS uptake study using human colon cancer-derived Caco-2 cells and confirmed that BCRP inhibitors significantly increased the intracellular accumulation of ROS. The correlation between the cell to medium (C/M) ratio of ROS obtained by the in vitro study and the absorption rate constant (ka) ratio obtained by clinical analysis was examined, and a significant positive correlation was observed. Therefore, it is suggested that the in vitro study using Caco-2 cells could be used to quantitatively estimate BCRP-mediated DDI with ROS in the gastrointestinal tract.

ABCG2 Expression as a Potential Survival Predictor in Human Gliomas.

Gliomas are notably challenging to treat due to their invasive nature and resistance to conventional therapies. The ABCG2 protein has attracted attention for its role in multidrug resistance, complicating treatment effectiveness. This study scrutinized the relationship between ABCG2 expression and glioma grade and the role of ABCG2 in the process of glioma progression, aiming to evaluate ABCG2 expression as a predictive factor of tumor progression and patient survival. Conducted at Dubrava University Hospital, Zagreb, Croatia, the study analyzed 152 glioma specimens from 2013 to 2022, assessing ABCG2 expression alongside standard clinical markers. A significant association was found between patients' survival and the ABCG2 profile (p = 0.003, r = 0.24), separately for patients who underwent chemotherapy (p = 0.0004, r = 0.32) and radiotherapy (p = 0.003, r = 0.29). Furthermore, the ABCG2 profile was significantly associated with disease progression (p = 0.007, r = 0.23), tumor grade (p = 0.0002, r = 0.31), and Ki67 expression (p = 0.0004, r = 0.31). ABCG2-positive tumor cells only showed association with Ki67 expression (p = 0.002, r = 0.28). The ABCG2 profile was found to affect the overall patient survival (p = 0.02) and represent a moderate indicator of tumor progression (p = 0.01), unlike the percentage of ABCG2-positive tumor cells. ABCG2 may serve as a marker of angiogenesis and vascular abnormalities within tumors, predicting glioma progression and treatment response. Targeting ABCG2 could enhance chemoradiotherapy efficacy and improve patient outcomes, which highlights its value in assessing tumor aggressiveness and designing treatment strategies.

The ABCG2 protein in vitro transports the xenobiotic thiabendazole and increases the appearance of its residues in milk.

Thiabendazole (TBZ) is a broad-spectrum anthelmintic and fungicide used in humans, animals, and agricultural commodities. TBZ residues are present in crops and animal products, including milk, posing a risk to food safety and public health. ABCG2 is a membrane transporter which affects bioavailability and milk secretion of xenobiotics. Therefore, the aim of this work was to characterize the role of ABCG2 in the in vitro transport and secretion into milk of 5-hydroxythiabendazole (5OH-TBZ), the main TBZ metabolite. Using MDCK-II polarized cells transduced with several species variants of ABCG2, we first demonstrated that 5OH-TBZ is efficiently in vitro transported by ABCG2. Subsequently, using Abcg2 knockout mice, we demonstrated that 5OH-TBZ secretion into milk was affected by Abcg2, with a more than 2-fold higher milk concentration and milk to plasma ratio in wild-type mice compared to their Abcg2-/- counterpart.

Magnolol derivatives as specific and noncytotoxic inhibitors of breast cancer resistance protein (BCRP/ABCG2).

The breast cancer resistance protein (BCRP/ABCG2) transporter mediates the efflux of numerous antineoplastic drugs, playing a central role in multidrug resistance related to cancer. The absence of successful clinical trials using specific ABCG2 inhibitors reveals the urge to identify new compounds to attend this critical demand. In this work, a series of 13 magnolol derivatives was tested as ABCG2 inhibitors. Only two compounds, derivatives 10 and 11, showed partial and complete ABCG2 inhibitory effect, respectively. This inhibition was selective toward ABCG2, since none of the 13 compounds inhibited neither P-glycoprotein nor MRP1. Both inhibitors (10 and 11) were not transported by ABCG2 and demonstrated a low cytotoxic profile even at high concentrations (up to 100 µM). 11 emerged as the most promising compound of the series, considering the ratio between cytotoxicity (IG50) and ABCG2 inhibition potency (IC50), showing a therapeutic ratio (TR) higher than observed for 10 (10.5 versus 1.6, respectively). This derivative showed a substrate-independent and a mixed type of inhibition. The effect of compound 11 on the ABCG2 ATPase activity and thermostability revealed allosteric protein changes. This compound did not affect the expression levels of ABCG2 and increased the binding of the conformational-sensitive antibody 5D3. A docking study showed that 11 did not share the same binding site with ABCG2 substrate mitoxantrone. Finally, 11 could revert the chemoresistance to SN-38 mediated by ABCG2.

Abcg2a is the functional homolog of human ABCG2 expressed at the zebrafish blood-brain barrier.

BACKGROUND: A principal protective component of the mammalian blood-brain barrier (BBB) is the high expression of the multidrug efflux transporters P-glycoprotein (P-gp, encoded by ABCB1) and ABCG2 (encoded by ABCG2) on the lumenal surface of endothelial cells. The zebrafish P-gp homolog Abcb4 is expressed at the BBB and phenocopies human P-gp. Comparatively little is known about the four zebrafish homologs of the human ABCG2 gene: abcg2a, abcg2b, abcg2c, and abcg2d. Here we report the functional characterization and brain tissue distribution of zebrafish ABCG2 homologs. METHODS: To determine substrates of the transporters, we stably expressed each in HEK-293 cells and performed cytotoxicity and fluorescent efflux assays with known ABCG2 substrates. To assess the expression of transporter homologs, we used a combination of RNAscope in situ hybridization probes and immunohistochemistry to stain paraffin-embedded sections of adult and larval zebrafish. RESULTS: We found Abcg2a had the greatest substrate overlap with ABCG2, and Abcg2d appeared to be the least functionally similar. We identified abcg2a as the only homolog expressed at the adult and larval zebrafish BBB, based on its localization to claudin-5 positive brain vasculature. CONCLUSIONS: These results demonstrate the conserved function of zebrafish Abcg2a and suggest that zebrafish may be an appropriate model organism for studying the role of ABCG2 at the BBB.

Experimental and Computational Methods to Assess Central Nervous System Penetration of Small Molecules.

In CNS drug discovery, the estimation of brain exposure to lead compounds is critical for their optimization. Compounds need to cross the blood-brain barrier (BBB) to reach the pharmacological targets in the CNS. The BBB is a complex system involving passive and active mechanisms of transport and efflux transporters such as P-glycoproteins (P-gp) and breast cancer resistance protein (BCRP), which play an essential role in CNS penetration of small molecules. Several in vivo, in vitro, and in silico methods are available to estimate human brain penetration. Preclinical species are used as in vivo models to understand unbound brain exposure by deriving the Kp,uu parameter and the brain/plasma ratio of exposure corrected with the plasma and brain free fraction. The MDCK-mdr1 (Madin Darby canine kidney cells transfected with the MDR1 gene encoding for the human P-gp) assay is the commonly used in vitro assay to estimate compound permeability and human efflux. The in silico methods to predict brain exposure, such as CNS MPO, CNS BBB scores, and various machine learning models, help save costs and speed up compound discovery and optimization at all stages. These methods enable the screening of virtual compounds, building of a CNS penetrable compounds library, and optimization of lead molecules for CNS penetration. Therefore, it is crucial to understand the reliability and ability of these methods to predict CNS penetration. We review the in silico, in vitro, and in vivo data and their correlation with each other, as well as assess published experimental and computational approaches to predict the BBB penetrability of compounds.

An acute herb-drug interaction of Magnoliae Officinalis Cortex with methotrexate via inhibiting multidrug resistance-associated protein 2.

Magnoliae Officinalis Cortex (MOC), an herbal drug, contains polyphenolic lignans mainly magnolol (MN) and honokiol (HK). Methotrexate (MTX), a critical drug for cancers and autoimmune deseases, is a substrate of multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP). This study investigated the effect of coadministration of MOC on the pharmacokinetics of MTX and relevant mechanisms. Sprague-Dawley rats were orally administered MTX alone and with single dose (2.0 and 4.0 g/kg) and repeated seven doses of MOC (2.0 g/kg thrice daily for 2 days, the 7th dose given at 0.5 h before MTX). The serum concentrations of MTX were determined by a fluorescence polarization immunoassay. The results showed that a single dose of MOC at 2.0 g/kg significantly increased the AUC0-t and MRT of MTX by 352% and 308%, and a single dose at 4.0 g/kg significantly enhanced the AUC0-t and MRT by 362% and 291%, respectively. Likewise, repeated seven doses of MOC at 2.0 g/kg significantly increased the AUC0-t and MRT of MTX by 461% and 334%, respectively. Mechanism studies indicated that the function of MRP2 was significantly inhibited by MN, HK and the serum metabolites of MOC (MOCM), whereas BCRP was not inhibited by MOCM. In conclusion, coadministration of MOC markedly enhanced the systemic exposure and mean residence time of MTX through inhibiting the MRP2-mediated excretion of MTX.

ABCG2 transporter reduces protein aggregation in cigarette smoke condensate-exposed A549 lung cancer cells.

Cigarette smoke-induced protein aggregation damages the lung cells in emphysema and COPD; however, lung cancer cells continue to thrive, evolving to persist in the toxic environment. Here, we showed that upon the cigarette smoke condensate exposure, A549 lung cancer cells exhibit better survival and reduced level of protein aggregation when compared to non-cancerous Beas-2B and H-6053 cells. Our data suggests that upregulation of efflux pumps in cancer cells assists in reducing smoke toxicity. Specifically, we demonstrated that inhibition of the ABCG2 transporter in A549 by febuxostat or its downregulation by shRNA-mediated RNA interference resulted in a significant increase in protein aggregation due to smoke exposure.

Adipocyte­rich microenvironment promotes chemoresistance via upregulation of peroxisome proliferator­activated receptor gamma/ABCG2 in epithelial ovarian cancer.

The effects of adipocyte­rich microenvironment (ARM) on chemoresistance have garnered increasing interest. Ovarian cancer (OVCA) is a representative adipocyte­rich associated cancer. In the present study, epithelial OVCA (EOC) was used to investigate the influence of ARM on chemoresistance with the aim of identifying novel targets and developing novel strategies to reduce chemoresistance. Bioinformatics analysis was used to explore the effects of ARM­associated mechanisms contributing to chemoresistance and treated EOC cells, primarily OVCAR3 cells, with human adipose tissue extracts (HATES) from the peritumoral adipose tissue of patients were used to mimic ARM in vitro. Specifically, the peroxisome proliferator­activated receptor Î³ (PPARγ) antagonist GW9662 and the ABC transporter G family member 2 (ABCG2) inhibitor KO143, were used to determine the underlying mechanisms. Next, the effect of HATES on the expression of PPARγ and ABCG2 in OVCAR3 cells treated with cisplatin (DDP) and paclitaxel (PTX) was determined. Additionally, the association between PPARγ, ABCG2 and chemoresistance in EOC specimens was assessed. To evaluate the effect of inhibiting PPARγ, using DDP, a nude mouse model injected with OVCAR3­shPPARγ cells and a C57BL/6 model injected with ID8 cells treated with GW9662 were established. Finally, the factors within ARM that contributed to the mechanism were determined. It was found that HATES promoted chemoresistance by increasing ABCG2 expression via PPARγ. Expression of PPARγ/ABCG2 was related to chemoresistance in EOC clinical specimens. GW9662 or knockdown of PPARγ improved the efficacy of chemotherapy in mice. Finally, angiogenin and oleic acid played key roles in HATES in the upregulation of PPARγ. The present study showed that the introduction of ARM­educated PPARγ attenuated chemoresistance in EOC, highlighting a potentially novel therapeutic adjuvant to chemotherapy and shedding light on a means of improving the efficacy of chemotherapy from the perspective of ARM.

Mass Spectrometry Investigation of Some ATP-Binding Cassette (ABC) Proteins.

Drug resistance remains one of the main causes of poor outcome in cancer therapy. It is also becoming evident that drug resistance to both chemotherapy and to antibiotics is driven by more than one mechanism. So far, there are at least eight recognized mechanisms behind such resistance. In this review, we choose to discuss one of these mechanisms, which is known to be partially driven by a class of transmembrane proteins known as ATP-binding cassette (ABC) transporters. In normal tissues, ABC transporters protect the cells from the toxic effects of xenobiotics, whereas in tumor cells, they reduce the intracellular concentrations of anticancer drugs, which ultimately leads to the emergence of multidrug resistance (MDR). A deeper understanding of the structures and the biology of these proteins is central to current efforts to circumvent resistance to both chemotherapy, targeted therapy, and antibiotics. Understanding the biology and the function of these proteins requires detailed structural and conformational information for this class of membrane proteins. For many years, such structural information has been mainly provided by X-ray crystallography and cryo-electron microscopy. More recently, mass spectrometry-based methods assumed an important role in the area of structural and conformational characterization of this class of proteins. The contribution of this technique to structural biology has been enhanced by its combination with liquid chromatography and ion mobility, as well as more refined labelling protocols and the use of more efficient fragmentation methods, which allow the detection and localization of labile post-translational modifications. In this review, we discuss the contribution of mass spectrometry to efforts to characterize some members of the ATP-binding cassette (ABC) proteins and why such a contribution is relevant to efforts to clarify the link between the overexpression of these proteins and the most widespread mechanism of chemoresistance.

Dietary gallic acid as an antioxidant: A review of its food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions.

Gallic acid (GA), a dietary phenolic acid with potent antioxidant activity, is widely distributed in edible plants. GA has been applied in the food industry as an antimicrobial agent, food fresh-keeping agent, oil stabilizer, active food wrap material, and food processing stabilizer. GA is a potential dietary supplement due to its health benefits on various functional disorders associated with oxidative stress, including renal, neurological, hepatic, pulmonary, reproductive, and cardiovascular diseases. GA is rapidly absorbed and metabolized after oral administration, resulting in low bioavailability, which is susceptible to various factors, such as intestinal microbiota, transporters, and metabolism of galloyl derivatives. GA exhibits a tendency to distribute primarily to the kidney, liver, heart, and brain. A total of 37 metabolites of GA has been identified, and decarboxylation and dihydroxylation in phase I metabolism and sulfation, glucuronidation, and methylation in phase Ⅱ metabolism are considered the main in vivo biotransformation pathways of GA. Different types of nanocarriers, such as polymeric nanoparticles, dendrimers, and nanodots, have been successfully developed to enhance the health-promoting function of GA by increasing bioavailability. GA may induce drug interactions with conventional drugs, such as hydroxyurea, linagliptin, and diltiazem, due to its inhibitory effects on metabolic enzymes, including cytochrome P450 3A4 and 2D6, and transporters, including P-glycoprotein, breast cancer resistance protein, and organic anion-transporting polypeptide 1B3. In conclusion, in-depth studies of GA on food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions have laid the foundation for its comprehensive application as a food additive and dietary supplement.

Roles of breast cancer resistance protein and organic anion transporting polypeptide 2B1 in gastrointestinal toxicity induced by SN-38 under inflammatory conditions.

Drug transporters are among the factors that determine the pharmacokinetic profiles after drug administration. In this study, we investigated the roles of drug transporters involved in transport of SN-38, which is an active metabolite of irinotecan, in the intestine under inflammatory conditions in vitro and determined their functional consequences. The expression alterations of breast cancer resistance protein (BCRP) and organic anion transporting polypeptide (OATP) 2B1 were determined at the mRNA and protein levels, and the subsequent functional alterations were evaluated via an accumulation study with the representative transporter substrates [prazosin and dibromofluorescein (DBF)] and SN-38. We also determined the cytotoxicity of SN-38 under inflammatory conditions. Decreased BCRP expression and increased OATP2B1 expression were observed under inflammatory conditions in vitro, which led to altered accumulation profiles of prazosin, DBF, and SN-38, and the subsequent cytotoxic profiles of SN-38. Treatment with rifampin or novobiocin supported the significant roles of BCRP and OATP2B1 in the transport and cytotoxic profile of SN-38. Collectively, these results suggest that BCRP and OATP2B1 are involved in the increased cytotoxicity of SN-38 under inflammatory conditions in vitro. Further comprehensive research is warranted to completely understand SN-38-induced gastrointestinal cytotoxicity and aid in the successful treatment of cancer with irinotecan.

Foretinib, a c-MET receptor tyrosine kinase inhibitor, tackles multidrug resistance in cancer cells by inhibiting ABCB1 and ABCG2 transporters.

BACKGROUND: ABC transporter-mediated multidrug resistance (MDR) remains a major obstacle for cancer pharmacological treatment. Some tyrosine kinase inhibitors (TKIs) have been shown to reverse MDR. The present study was designed to evaluate for the first time whether foretinib, a multitargeted TKI, can circumvent ABCB1 and ABCG2-mediated MDR in treatment-resistant cancer models. METHODS: Accumulation of fluorescent substrates of ABCB1 and ABCG2 in ABCB1-overexpressing MES-SA/DX5 and ABCG2-overexpressing MCF-7/MX and their parenteral cells was evaluated by flow cytometry. The growth inhibitory activity of single and combination therapy of foretinib and chemotherapeutic drugs on MDR cells was examined by MTT assay. Analysis of combined interaction effects was performed using CalcuSyn software. RESULTS: It was firstly proved that foretinib increased the intracellular accumulation of rhodamine 123 and mitoxantrone in MES-SA/DX5 and MCF-7/MX cancer cells, with accumulation ratios of 12 and 2.2 at 25 µM concentration, respectively. However, it did not affect the accumulation of fluorescent substrates in the parental cells. Moreover, foretinib synergistically improved the cytotoxic effects of doxorubicin and mitoxantrone. The means of combination index (CI) values at fraction affected (Fa) values of 0.5, 0.75, and 0.9 were 0.64 ± 0.08 and 0.47 ± 0.09, in MES-SA/DX5 and MCF-7/MX cancer cells, respectively. In silico analysis also suggested that the drug-binding domain of ABCB1 and ABCG2 transporters could be considered as potential target for foretinib. CONCLUSION: Overall, our results suggest that foretinib can target MDR-linked ABCB1 and ABCG2 transporters in clinical cancer therapy.