Structure, function and regulation of P-glycoprotein and its clinical relevance in drug disposition

Overcoming Chemoresistance in Cancer: The Promise of Crizotinib

Chemoresistance is a major obstacle in cancer treatment, often leading to disease progression and poor outcomes. It arises through various mechanisms such as genetic mutations, drug efflux pumps, enhanced DNA repair, and changes in the tumor microenvironment. These processes allow cancer cells to survive despite chemotherapy, underscoring the need for new strategies to overcome resistance and improve treatment efficacy. Crizotinib, a first-generation multi-target kinase inhibitor, is approved by the FDA for the treatment of ALK-positive or ROS1-positive non-small cell lung cancer (NSCLC), refractory inflammatory (ALK)-positive myofibroblastic tumors (IMTs) and relapsed/refractory ALK-positive anaplastic large cell lymphoma (ALCL). Crizotinib exists in two enantiomeric forms: (R)-crizotinib and its mirror image, (S)-crizotinib. It is assumed that the R-isomer is responsible for the carrying out various processes reviewed here The S-isomer, on the other hand, shows a strong inhibition of MTH1, an enzyme important for DNA repair mechanisms. Studies have shown that crizotinib is an effective multi-kinase inhibitor targeting various kinases such as c-Met, native/T315I Bcr/Abl, and JAK2. Its mechanism of action involves the competitive inhibition of ATP binding and allosteric inhibition, particularly at Bcr/Abl. Crizotinib showed synergistic effects when combined with the poly ADP ribose polymerase inhibitor (PARP), especially in ovarian cancer harboring BRCA gene mutations. In addition, crizotinib targets a critical vulnerability in many p53-mutated cancers. Unlike its wild-type counterpart, the p53 mutant promotes cancer cell survival. Crizotinib can cause the degradation of the p53 mutant, sensitizing these cancer cells to DNA-damaging substances and triggering apoptosis. Interestingly, other reports demonstrated that crizotinib exhibits anti-bacterial activity, targeting Gram-positive bacteria. Also, it is active against drug-resistant strains. In summary, crizotinib exerts anti-tumor effects through several mechanisms, including the inhibition of kinases and the restoration of drug sensitivity. The potential of crizotinib in combination therapies is emphasized, particularly in cancers with a high prevalence of the p53 mutant, such as triple-negative breast cancer (TNBC) and high-grade serous ovarian cancer (HGSOC).

Enhancing of cerebral Abeta clearance by modulation of ABC transporter expression: a review of experimental approaches

Clearance of amyloid-beta (Aβ) from the brain is impaired in both early-onset and late-onset Alzheimer's disease (AD). Mechanisms for clearing cerebral Aβ include proteolytic degradation, antibody-mediated clearance, blood brain barrier and blood cerebrospinal fluid barrier efflux, glymphatic drainage, and perivascular drainage. ATP-binding cassette (ABC) transporters are membrane efflux pumps driven by ATP hydrolysis. Their functions include maintenance of brain homeostasis by removing toxic peptides and compounds, and transport of bioactive molecules including cholesterol. Some ABC transporters contribute to lowering of cerebral Aβ. Mechanisms suggested for ABC transporter-mediated lowering of brain Aβ, in addition to exporting of Aβ across the blood brain and blood cerebrospinal fluid barriers, include apolipoprotein E lipidation, microglial activation, decreased amyloidogenic processing of amyloid precursor protein, and restricting the entrance of Aβ into the brain. The ABC transporter superfamily in humans includes 49 proteins, eight of which have been suggested to reduce cerebral Aβ levels. This review discusses experimental approaches for increasing the expression of these ABC transporters, clinical applications of these approaches, changes in the expression and/or activity of these transporters in AD and transgenic mouse models of AD, and findings in the few clinical trials which have examined the effects of these approaches in patients with AD or mild cognitive impairment. The possibility that therapeutic upregulation of ABC transporters which promote clearance of cerebral Aβ may slow the clinical progression of AD merits further consideration.

Combination Treatment with EGFR Inhibitor and Doxorubicin Synergistically Inhibits Proliferation of MCF-7 Cells and MDA-MB-231 Triple-Negative Breast Cancer Cells In Vitro

The role of the epidermal growth factor receptor (EGFR) in tumor progression and survival is often underplayed. Its expression and/or dysregulation is associated with disease advancement and poor patient outcome as well as drug resistance in breast cancer. EGFR is often overexpressed in breast cancer and particularly triple-negative breast cancer (TNBC), which currently lacks molecular targets. We examined the synergistic potential of an EGFR inhibitor (EGFRi) in combination with doxorubicin (Dox) in estrogen-positive (ER+) MCF-7 and MDA-MB-231 TNBC cell lines. The exposure of MDA-MB-231 and MCF-7 to EGFRi produced an IC50s of 6.03 µM and 3.96 µM, respectively. Dox induced MDA-MB-231 (IC50 9.67 µM) and MCF-7 (IC50 1.4 µM) cytotoxicity. Combinations of EGFRi-Dox significantly reduced the IC50 in MCF-7 (0.46 µM) and MBA-MB 231 (0.01 µM). Synergistic drug interactions in both cell lines were confirmed using the Bliss independence model. Pro-apoptotic Caspase-3/7 activation occurred in MCF-7 at 0.1-10 µM of EGFRi and Dox single treatments, whilst 1 μM Dox yielded a more potent effect on MDA-MB-231. EGFRi and Dox individually and in combination downregulated the EGFR gene expression in MCF-7 and MDA-MB-231 (p < 0.001). This study demonstrates EGFRi's potential for eliciting synergistic interactions with Dox, causing enhanced growth inhibition, apoptosis induction, and downregulation of EGFR in both cell lines.

Evaluation of Antitumor Activity of Xanthones Conjugated with Amino Acids

Cancer is a complex disease characterized by several alterations, which confer, to the cells, the capacity to proliferate uncontrollably and to resist cellular death. Multiresistance to conventional chemotherapy drugs is often the cause of treatment failure; thus, the search for natural products or their derivatives with therapeutic action is essential. Chiral derivatives of xanthones (CDXs) have shown potential inhibitory activity against the growth of some human tumor cell lines. This work reports the screening of a library of CDXs, through viability assays, in different cancer cell lines: A375-C5, MCF-7, NCI-H460, and HCT-15. CDXs' effect was analyzed based on several parameters of cancer cells, and it was also verified if these compounds were substrates of glycoprotein-P (Pgp), one of the main mechanisms of resistance in cancer therapy. Pgp expression was evaluated in all cell lines, but no expression was observed, except for HCT-15. Also, when a humanized yeast expressing the human gene MDR1 was used, no conclusions could be drawn about CDXs as Pgp substrates. The selected CDXs did not induce significant differences in the metabolic parameters analyzed. These results show that some CDXs present promising antitumor activity, but other mechanisms should be triggered by these compounds.

Exploring the dynamics of the ABCB1 membrane transporter P-glycoprotein in the presence of ATP and active/non-active compounds through molecular dynamics simulations

P-glycoprotein (Pgp) is a member of the ATP-binding cassette family of transporters that confers multidrug resistance to cancer cells and is actively involved in the pharmacokinetics and toxicokinetics of a big variety of drugs. Extensive studies have provided insights into the binding of many compounds, but the precise mechanism of translocation across the membrane remains unknown; in this context, the major challenge has been to understand the basis for its polyspecificity. In this study, molecular dynamics (MD) simulations of human P-gp (hP-gp) in an explicit membrane-and-water environment were performed to investigate the dynamic behavior of the transporter in the presence of different compounds (active and inactive) in the binding pocket and ATP molecules within the nucleotide binding domains (NBDs). The complexes studied involve four compounds: cyclosporin A (CSA), amiodarone (AMI), pamidronate (APD), and valproic acid (VPA). While CSA and AMI are known to interact with P-gp, APD and VPA do not. The results highlighted how the presence of ATP notably contributed to increased flexibility of key residues in NBD1 of active systems, indicating potential conformational changes activating the translocation mechanism. MD simulations reveal how these domains adapt and respond to the presence of different substrates, as well as the influence of ATP binding on their flexibility. Furthermore, distinctive behavior was observed in the presence of active and inactive compounds, particularly in the arrangement of ATP between NBDs, supporting the proposed nucleotide sandwich dimer mechanism for ATP binding. This study provides comprehensive insights into P-gp behavior with various ligands and ATP, offering implications for drug development, toxicity assessment and demonstrating the validity of the results derived from the MD simulations.

TMEM97 knockdown inhibits 5-fluorouracil resistance by regulating epithelial-mesenchymal transition and ABC transporter expression via inactivating the Akt/mTOR pathway in 5-fluorouracil-resistant colorectal cancer cells

Resistance to 5-fluorouracil (5-FU) is still a primary setback to the success of colorectal cancer (CRC) chemotherapy. Transmembrane protein 97 (TMEM97) functions as an oncogene in CRC. However, the role and mechanism of TMEM97 in regulating 5-FU resistance in CRC cells remains unclear. TMEM97 expression in CRC samples was analyzed by GEPIA and human protein atlas (HPA) databases. TMEM97, E-cadherin, Vimentin, N-cadherin, P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1)/ABCC1, ABCC2, and the changes of protein kinase B/mammalian target of rapamycin (mTOR) pathway were explored by western blot analysis. IC50 value for 5-FU and cell viability was examined by MTT assay. Apoptosis was evaluated by flow cytometry. TMEM97 was highly expressed in colon adenocarcinoma (COAD) and rectum adenocarcinoma (READ) based on GEPIA and HPA databases. TMEM97 knockdown attenuated 5-FU resistance in HCT116/R and SW480/R cells, as evidenced by the reduced IC50 value for 5-FU and the increased apoptosis. TMEM97 knockdown suppressed epithelial-mesenchymal transition (EMT), expression of ATP-binding cassette (ABC) transporters, and the Akt/mTOR pathway. Mechanistically, activation of Akt/mTOR pathway abolished the inhibitory effects of TMEM97 knockdown on 5-FU resistance, EMT, and ABC transporter expression. In conclusion, TMEM97 knockdown inhibited 5-FU resistance in CRC by regulating EMT and ABC transporter expression via inactivating the Akt/mTOR pathway.

Effects of Aqueous Boundary Layers and Paracellular Transport on the Efflux Ratio as a Measure of Active Transport Across Cell Layers

The efflux ratio (ER), determined by Caco-2/MDCK assays, is the standard in vitro metric to establish qualitatively whether a compound is a substrate of an efflux transporter. However, others have also enabled the utilisation of this metric quantitatively by deriving a relationship that expresses the ER as a function of the intrinsic membrane permeability of the membrane (P0) as well as the permeability of carrier-mediated efflux (Ppgp). As of yet, Ppgp cannot be measured directly from transport experiments or otherwise, but the ER relationship provides easy access to this value if P0 is known. However, previous derivations of this relationship failed to consider the influence of additional transport resistances such as the aqueous boundary layers (ABLs) and the filter on which the monolayer is grown. Since single fluxes in either direction can be heavily affected by these experimental artefacts, it is crucial to consider the potential impact on the ER. We present a model that includes these factors and show both mathematically and experimentally that this simple ER relationship also holds for the more realistic scenario that does not neglect the ABLs/filter. Furthermore, we also show mathematically how paracellular transport affects the ER, and we experimentally confirm that paracellular dominance reduces the ER to unity and can mask potential efflux.

Quantification of P-glycoprotein function at the human blood-brain barrier using [18F]MC225 and PET

INTRODUCTION

P-glycoprotein (P-gp) is one of the most studied efflux transporters at the blood-brain barrier. It plays an important role in brain homeostasis by protecting the brain from a variety of endogenous and exogeneous substances. Changes in P-gp function are associated both with the onset of neuropsychiatric diseases, including Alzheimer's disease and Parkinson's disease, and with drug-resistance, for example in treatment-resistant depression. The most widely used approach to measure P-gp function in vivo is (R)-[11C]verapamil PET. (R)-[11C]verapamil is, however, an avid P-gp substrate, which complicates the use of this tracer to measure an increase in P-gp function as its baseline uptake is already very low. [18F]MC225 was developed to measure both increases and decreases in P-gp function.

AIM

The aim of this study was (1) to identify the pharmacokinetic model that best describes [18F]MC225 kinetics in the human brain and (2) to determine test-retest variability.

METHODS

Five (2 male, 3 female) of fourteen healthy subjects (8 male, 6 female, age 67 ± 5 years) were scanned twice (injected dose 201 ± 47 MBq) with a minimum interval of 2 weeks between scans. Each scanning session consisted of a 60-min dynamic [18F]MC225 scan with continuous arterial sampling. Whole brain grey matter data were fitted to a single tissue compartment model, and to reversible and irreversible two tissue-compartment models to obtain various outcome parameters (in particular the volume of distribution (VT), Ki, and the rate constants K1 and k2). In addition, a reversible two-tissue compartment model with fixed k3/k4 was included. The preferred model was selected based on the weighted Akaike Information Criterion (AIC) score. Test-retest variability (TRTV) was determined to assess reproducibility.

RESULTS

Sixty minutes post-injection, the parent fraction was 63.8 ± 4.0%. The reversible two tissue compartment model corrected for plasma metabolites with an estimated blood volume (VB) showed the highest AIC weight score of 34.3 ± 17.6%. The TRVT of the VT for [18F]MC225 PET scans was 28.3 ± 20.4% for the whole brain grey matter region using this preferred model.

CONCLUSION

[18F]MC225 VT, derived using a reversible two-tissue compartment model, is the preferred parameter to describe P-gp function in the human BBB. This outcome parameter has an average test-retest variability of 28%.

TRIAL REGISTRATION

EudraCT 2020-001564-28 . Registered 25 May 2020.

Molecular imaging of tumor hypoxia: Evolution of nitroimidazole radiopharmaceuticals and insights for future development

Though growing evidence has been collected in support of the concept of dose escalation based on the molecular level images indicating hypoxic tumor sub-volumes that could be radio-resistant, validation of the concept is still a work in progress. Molecular imaging of tumor hypoxia using radiopharmaceuticals is expected to provide the required input to plan dose escalation through Image Guided Radiation Therapy (IGRT) to kill/control the radio-resistant hypoxic tumor cells. The success of the IGRT, therefore, is heavily dependent on the quality of images obtained using the radiopharmaceutical and the extent to which the image represents the true hypoxic status of the tumor in spite of the heterogeneous nature of tumor hypoxia. Available literature on radiopharmaceuticals for imaging hypoxia is highly skewed in favor of nitroimidazole as the pharmacophore given their ability to undergo oxygen dependent reduction in hypoxic cells. In this context, present review on nitroimidazole radiopharmaceuticals would be immensely helpful to the researchers to obtain a birds-eye view on what has been achieved so far and what can be tried differently to obtain a better hypoxia imaging agent. The review also covers various methods of radiolabeling that could be utilized for developing radiotracers for hypoxia targeting applications.

Plasma lipidomic analysis to investigate putative biomarkers of P-glycoprotein activity in healthy volunteers

P-glycoprotein (P-gp) is an efflux transporter involved in the bioavailability of many drugs currently on the market. P-gp is responsible for several drug-drug interactions encountered in clinical practice leading to iatrogenic hospital admissions, especially in polypharmacy situations. ABCB1 genotyping only reflects an indirect estimate of P-gp activity. Therefore, it would be useful to identify endogenous biomarkers to determine the P-gp phenotype to predict in vivo activity prior to the initiation of treatment and to assess the effects of drugs on P-gp activity. The objective of this study was to assess changes in plasma lipidome composition among healthy volunteers selected on the basis of their ABCB1 genotype and who received clarithromycin, a known inhibitor of P-gp. Untargeted lipidomic analysis based on liquid chromatography-tandem mass spectrometry was performed before and after clarithromycin administration. Our results revealed changes in plasma levels of some ceramides (Cers) {Cer(d18:1/22:0), Cer(d18:1/22:1), and Cer(d18:1/20:0) by ~38% (p < 0.0001), 13% (p < 0.0001), and 13% (p < 0.0001), respectively} and phosphatidylcholines (PCs) {PC(17:0/14:1), PC(16:0/18:3), and PC(14:0/18:3) by ~24% (p < 0.001), 10% (p < 0.001), and 23.6% (p < 0.001)} associated with both ABCB1 genotype and clarithromycin intake. Through the examination of plasma lipids, our results highlight the relevance of untargeted lipidomics for studying in vivo P-gp activity and, more generally, to safely phenotyping transporters.

Advantages and potential limitations of applying AFM kymograph analysis to pharmaceutically relevant membrane proteins in lipid bilayers

Membrane proteins play critical roles in disease and in the disposition of many pharmaceuticals. A prime example is P-glycoprotein (Pgp) which moves a diverse range of drugs across membranes and out of the cell before a therapeutic payload can be delivered. Conventional structural biology methods have provided a valuable framework for comprehending the complex conformational changes underlying Pgp function, which also includes ATPase activity, but the lack of real-time information hinders understanding. Atomic force microscopy (AFM) is a single-molecule technique that is well-suited for studying active membrane proteins in bilayers and is poised to advance the field beyond static snapshots. After verifying Pgp activity in surface-support bilayers, we used kymograph analysis in conjunction with AFM imaging and simulations to study structural transitions at the 100 ms timescale. Though kymographs are frequently employed to boost temporal resolution, the limitations of the method have not been well characterized, especially for sparse non-crystalline distributions of pharmaceutically relevant membrane proteins like Pgp. Common experimental challenges are analyzed, including protein orientation, instrument noise, and drift. Surprisingly, a lateral drift of 75% of the protein dimension leads to only a 12% probability of erroneous state transition detection; average dwell time error achieves a maximum value of 6%. Rotational drift of proteins like Pgp, with azimuthally-dependent maximum heights, can lead to artifactual transitions. Torsional constraints can alleviate this potential pitfall. Confidence in detected transitions can be increased by adding conformation-altering ligands such as non-hydrolysable analogs. Overall, the data indicate that AFM kymographs are a viable method to access conformational dynamics for Pgp, but generalizations of the method should be made with caution.

Research Methods and New Advances in Drug-Drug Interactions Mediated by Renal Transporters

The kidney is critical in the human body's excretion of drugs and their metabolites. Renal transporters participate in actively secreting substances from the proximal tubular cells and reabsorbing them in the distal renal tubules. They can affect the clearance rates (CLr) of drugs and their metabolites, eventually influence the clinical efficiency and side effects of drugs, and may produce drug-drug interactions (DDIs) of clinical significance. Renal transporters and renal transporter-mediated DDIs have also been studied by many researchers. In this article, the main types of in vitro research models used for the study of renal transporter-mediated DDIs are membrane-based assays, cell-based assays, and the renal slice uptake model. In vivo research models include animal experiments, gene knockout animal models, positron emission tomography (PET) technology, and studies on human beings. In addition, in vitro-in vivo extrapolation (IVIVE), ex vivo kidney perfusion (EVKP) models, and, more recently, biomarker methods and in silico models are included. This article reviews the traditional research methods of renal transporter-mediated DDIs, updates the recent progress in the development of the methods, and then classifies and summarizes the advantages and disadvantages of each method. Through the sorting work conducted in this paper, it will be convenient for researchers at different learning stages to choose the best method for their own research based on their own subject's situation when they are going to study DDIs mediated by renal transporters.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood-brain barrier co-cultured with microglia

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer's (AD). Considered the brain's first line of defense, the Blood-Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aβ transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 μg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1β and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB's response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB's responses to this environmental chemical.

Simultaneous quantification of pirarubicin, doxorubicin, cyclophosphamide, and vincristine in human plasma of patients with non-Hodgkin's lymphoma by LC-MS/MS method

Pirarubicin (THP), doxorubicin (DOX), cyclophosphamide (CTX), and vincristine (VCR) are widely used in the treatment of patients with non-Hodgkin's Lymphoma. Herein, a precise and sensitive method was developed for the determination of THP, DOX, CTX and VCR in human plasma by high-performance liquid-chromatography-tandem mass spectrometry (LC-MS/MS). Liquid-liquid extraction was applied to extract THP, DOX, CTX, VCR, and the internal standard (IS, Pioglitazone) in plasma. Agilent Eclipse XDB-C18 (3.0 mm × 100 mm) was utilized and chromatographic separation was obtained in eight minutes. Mobile phases were composed of methanol and buffer (10 mM ammonium formate containing 0.1% formic acid). The method was linear within the concentration range of 1-500 ng/mL for THP, 2-1000 ng/mL for DOX, 2.5-1250 ng/mL for CTX, and 3-1500 ng/mL for VCR. The intra- and inter-day precisions of QC samples were found to be below 9.31 and 13.66%, and accuracy ranged from -0.2 to 9.07%, respectively. THP, DOX, CTX, VCR and the internal standard were stable in several conditions. Finally, this method was successfully utilized to simultaneously determine THP, DOX, CTX and VCR in human plasma of 15 patients with non-Hodgkin's Lymphoma after intravenous administration. Finally, the method was successfully employed in the clinical determination of THP, DOX, CTX, and VCR in patients with non-Hodgkin lymphoma after administration of RCHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) regimens.

Impact of Plastic-Related Compounds on P-Glycoprotein and Breast Cancer Resistance Protein In Vitro

Plastic in oceans degrades to microplastics and nanoplastics, causing various problems for marine fauna and flora. Recently, microplastic has been detected in blood, breast milk and placenta, underlining their ability to enter the human body with still unknown effects. In addition, plastic contains other compounds such as plasticizers, antioxidants or lubricants, whose impact on human health is also elusive. On the cellular level, two transporters involved in cell protection and detoxification of xenobiotic compounds are the ABC-transporters P-glycoprotein (P-gp, MDR1, ABCB1) and breast cancer resistance protein (BCRP, ABCG2). Despite the great importance of these proteins to maintain the correct cellular balance, their interaction with plastic and related products is evasive. In this study, the possible interaction between different plastic-related compounds and these two transporters was investigated. Applying virtual compound screening and molecular docking of more than 1000 commercially available plastic compounds, we identified candidates most probably interacting with these two transporters. Cytotoxicity and uptake assays confirmed their toxic interaction on P-glycoprotein-overexpressing CEM/ADR5000 and BCRP-overexpressing MDA-MD-231-BCRP cell lines. To specifically visualize the results obtained on the P-glycoprotein inhibitor 2,2’-methylenebis(6-tert-butyl-4-methylphenol), we performed live cell time-lapse microscopy. Confocal fluorescence microscopy was used to understand the behavior of the molecule and the consequences that it has on the uptake of the well-known substrate doxorubicin and, in comparison, with the known inhibitor verapamil. Based on the results, we provide evidence that the compound in question is an inhibitor of the P-glycoprotein. Moreover, it is also possible that 2,2’-methylenebis(6-tert-butyl-4-methylphenol), together with three other compounds, may also inhibit the breast cancer resistance protein. This discovery implies that plastic-related compounds can not only harm the human body but can also inhibit detoxifying efflux pumps, which increases their toxic potential as these transporters lose their physiological functions.

The ATP-binding cassette proteins ABCB1 and ABCC1 as modulators of glucocorticoid action

Responses to hormones that act through nuclear receptors are controlled by modulating hormone concentrations not only in the circulation but also within target tissues. The role of enzymes that amplify or reduce local hormone concentrations is well established for glucocorticoid and other lipophilic hormones; moreover, transmembrane transporters have proven critical in determining tissue responses to thyroid hormones. However, there has been less consideration of the role of transmembrane transport for steroid hormones. ATP-binding cassette (ABC) proteins were first shown to influence the accumulation of glucocorticoids in cells almost three decades ago, but observations over the past 10 years suggest that differential transport propensities of both exogenous and endogenous glucocorticoids by ABCB1 and ABCC1 transporters provide a mechanism whereby different tissues are preferentially sensitive to different steroids. This Review summarizes this evidence and the new insights provided for the physiology and pharmacology of glucocorticoid action, including new approaches to glucocorticoid replacement.

The Interaction between Four Polymorphisms and Haplotype of ABCB1, the Risk of Non-Small Cell Lung Cancer, and the Disease Phenotype

P-glycoprotein, product of the ABCB1 (ATP binding cassette subfamily B member 1) gene, has been reported to play an important role in multiple drug resistance during cancer therapy. However, its influence on non-small cell lung cancer (NSCLC) risk has not been clearly defined. The aim of the present study was to examine the association between clinicopathological factors and SNPs T-129C, C1236T, G2677T/A, and C3435T, as well as its haplotype, and to investigate the role of ABCB1 polymorphisms in NSCLC development. The study included 80 patients who suffered from NSCLC and underwent surgery to remove the tumour and 96 healthy controls. The tissues were genotyped by PCR-RFLP and sequencing methods, and the haplotype frequencies in both groups were estimated. The SNP C3435T was identified as a NSCLC risk factor. The presence of mutated allelic variant T (p=0.0103) or homozygote TT (p=0.0099) was observed significantly more often in cancer patients than in healthy controls. The two groups also demonstrated a highly significant difference in common haplotype frequency (p=0.01). The T_-129-T₁₂₃₆-T₂₆₇₇-T₃₄₃₅ haplotype was found to be most closely associated with NSCLC risk. Although the investigated polymorphisms were not related to demographic features, clinicopathological lung tumour characteristics, or blood morphology indices, marginally significant correlations were found with some variables: C1236T with age of disease onset (p=0.0410); C3435T with smoking status (p=0.0561). As the findings indicate, lung cancer and control groups demonstrate significantly different patterns of -129/1236/2677/3435 haplotype distribution; T-T-T-T haplotype contributes to NSCLC susceptibility, and this effect is probably mainly dependent on C3435T. So far, similar studies were published in other populations.

Translatability of in vitro Inhibition Potency to in vivo P-Glycoprotein Mediated Drug Interaction Risk

P-glycoprotein (P-gp) may limit oral drug absorption of substrate drugs due to intestinal efflux. Therefore, regulatory agencies require investigation of new chemical entities as possible inhibitors of P-gp in vitro. Unfortunately, inter-laboratory and inter-assay variability have hindered the translatability of in vitro P-gp inhibition data to predict clinical drug interaction risk. The current study was designed to evaluate the impact of potential IC₅₀ discrepancies between two commonly utilized assays, i.e., bi-directional Madin-Darby Canine Kidney-MDR1 cell-based and MDR1 membrane vesicle-based assays. When comparing vesicle- to cell-based IC₅₀ values (n = 28 inhibitors), non-P-gp substrates presented good correlation between assay formats, whereas IC₅₀s of P-gp substrates were similar or lower in the vesicle assays. The IC₅₀s obtained with a cell line expressing relatively low P-gp aligned more closely to those obtained from the vesicle assay, but passive permeability of the inhibitors did not appear to influence the correlation of IC₅₀s, suggesting that efflux activity reduces intracellular inhibitor concentrations. IC₅₀s obtained between two independent laboratories using the same assay type showed good correlation. Using the G-value (i.e., ratio of estimated gut concentration-to-inhibition potency) >10 cutoff recommended by regulatory agencies resulted in minimal differences in predictive performance, suggesting this cutoff is appropriate for either assay format.

Canine and feline P-glycoprotein deficiency: What we know and where we need to go

In 2001 the molecular genetic basis of so-called "ivermectin sensitivity" in herding breed dogs was determined to be a P-glycoprotein deficiency caused by a genetic variant of the MDR1 (ABCB1) gene often called "the MDR1 mutation." We have learned a great deal about P-glycoprotein's role in drug disposition since that discovery, namely that P-glycoprotein transports many more drugs than just macrocyclic lactones that P-glycoprotein mediated drug transport is present in more places than just the blood brain barrier, that some cats have a genetic variant of MDR1 that results in P-glycoprotein deficiency, that P-glycoprotein dysfunction can occur as a result of drug-drug interactions in any dog or cat, and that the concept of P-glycoprotein "inhibitors" versus P-glycoprotein substrates is somewhat arbitrary and artificial. This paper will review these discoveries and discuss how they impact drug selection and dosing in dogs and cats with genetically mediated P-glycoprotein deficiency or P-glycoprotein dysfunction resulting from drug-drug interactions.

Some New Aspects of Genetic Variability in Patients with Cutaneous T-Cell Lymphoma

AIM

Cutaneous T-cell lymphoma (CTCL) is a group of T-cell malignancies that develop in the skin. Though studied intensively, the etiology and pathogenesis of CTCL remain elusive. This study evaluated the survival of CTCL patients in the 1st Department of Dermatovenereology of St. Anne's University Hospital Brno. It included analysis of 19 polymorphic gene variants based on their expected involvement in CTCL severity.

MATERIAL AND METHODS

75 patients with CTCL, evaluated and treated at the 1st Department of Dermatovenereology of St. Anne´s University Hospital Brno, Faculty of Medicine, Masaryk University, were recruited for the study over the last 28 years (44 men and 31 women, average age 58 years, range 20-82 years). All patients were genotyped for 19 chosen gene polymorphisms by the conventional PCR method with restriction analysis. A multivariate Cox regression model was calculated to reveal genetic polymorphisms and other risk factors for survival.

RESULTS

The model identified MDR Ex21 2677 (rs2032582) as a significant genetic factor influencing the survival of the patients, with the T-allele playing a protective role. A multivariate stepwise Cox regression model confirmed the following as significant independent risk factors for overall survival: increased age at admission, clinical staging of the tumor, and male sex.

CONCLUSION

We showed that the TT genotype at position 2677 of the MDR1 gene exhibited statistically significant longer survival in CTCL patients. As such, the TT genotype of MDR1 confers a significant advantage for the CTCL patients who respond to treatment.

Analysis of P-Glycoprotein Transport Cycle Reveals a New Way to Identify Efflux Inhibitors

P-glycoprotein (P-gp) is found to be of considerable interest for the design of drugs capable of treating chemoresistant tumors. This transporter is an interesting target for which an efficient approach has not yet been developed in terms of computer simulation. In this work, we use a combination of docking, molecular dynamics, and metadynamics to fully explore the states that occur during the capture of a ligand and subsequent efflux by P-gp. The proposed approach allowed us to substantiate a number of experimentally established facts, as well as to develop a new criterion for identifying potential P-gp inhibitors.

Examination of the emerging role of transporters in the assessment of nephrotoxicity

INTRODUCTION

The kidney is vulnerable to various injuries based on its function in the elimination of many xenobiotics, endogenous substances and metabolites. Since transporters are critical for the renal elimination of those substances, it is urgent to understand the emerging role of transporters in nephrotoxicity.

AREAS COVERED

This review summarizes the contribution of major renal transporters to nephrotoxicity induced by some drugs or toxins; addresses the role of transporter-mediated endogenous metabolic disturbances in nephrotoxicity; and discusses the advantages and disadvantages of in vitro models based on transporter expression and function.

EXPERT OPINION

Due to the crucial role of transporters in the renal disposition of xenobiotics and endogenous substances, it is necessary to further elucidate their renal transport mechanisms and pay more attention to the underlying relationship between the transport of endogenous substances and nephrotoxicity. Considering the species differences in the expression and function of transporters, and the low expression of transporters in general cell models, in vitro humanized models, such as humanized 3D organoids, shows significant promise in nephrotoxicity prediction and mechanism study.

Clinical and genetic factors associated with self-reported cognitive deficits in women with breast cancer: the "CAGE-Cog" study

Background

Breast cancer patients undergoing chemotherapy treatment are at particular risk of experiencing acute cognitive impairment leading to daily challenges in decision-making and reduced quality of life and functional autonomy. The aim was to assess the relationship between clinical and genetic factors and cognitive function in a sample of patients with breast cancer undergoing chemotherapy.

Methods

A cross-sectional study was carried out between November 2017 and June 2019 on women (N = 112) treated for breast cancer by intravenous chemotherapy at the oncology outpatient unit of Hôtel-Dieu de France Hospital, Beirut. Patients were evaluated with the 37-item Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog). Other validated scales were also used to assess depression, anxiety, sleep disorders, pain, and fatigue. DNA was obtained by a buccal swab (FTA®technology) for genotyping of different genes (ABCB1, COMT, DRD2, OPRM1, CLOCK, CRY2, and PER2) using the Lightcycler®(Roche).

Results

The mean age of participants was 56.04 years. Multivariable analysis, taking the four FACT-Cog subscores as the dependent variables, showed that the mean cognitive score decreased with higher depression, anxiety, and insomnia scores. Patients with university education levels had better perceived cognitive abilities than those with primary education. Moreover, carrying the G allele for the OPRM1 polymorphism (c.118A > G;rs197791) was significantly associated with a better cognitive function compared to AA patients (B = 2.05; p = 0.038).

Conclusions

A comprehensive oncological care plan should include a personalized assessment of all factors related to cognitive functioning in cancer patients, particularly anxiety and depression, to achieve an optimal patient outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10077-6.

Inflammatory factor tumor necrosis factor-α (TNF-α) activates P-glycoprotein (P-gp) by phosphorylating c-Jun and thus promotes transportation in placental cells

BACKGROUND

P-glycoprotein (P-gp), encoded by the ABCB1 gene, actively pumps drugs and other xenobiotics from trophoblast cells back into the maternal circulation and thus acts as one of the most critical protectors of the fetus. The effect of tumor necrosis factor-α (TNF-α) on P-gp and molecule-transporting activity remains unknown. The goal of this study was to investigate the role of TNF-α in placental molecule-transporting activity and the underlies mechanisms.

METHODS

Cultured human placental choriocarcinoma cell lines, Bewo, JEG-3 and JAR, were used in this study. Cultured cells were incubated with 5, 10 and 20 ng/mL of recombinant TNF-α (rTNF-α) for 24 h, respectively, for follow-up experiments. The dimer form and expression of activator protein-1 (AP-1) family members were detected using Western blot (WB) and chromatin immunoprecipitation (ChIP). mRNA and protein expression of ABCB1 were detected using reverse transcriptional quantitative polymerase chain reaction (RT-qPCR) and WB, respectively. Double luciferase labeling was used to verify the concentration of digoxin. Electromobility shift assay (EMSA) and ChIP were used to identify the binding ability of c-Jun to ABCB1 gene promoter. Proliferation and apoptosis of Bewo cells were determined using flow cytometry. Digoxin concentration were determined using dual luciferase labeling method.

RESULTS

Administration of rTNF-α upregulated the expression of c-Jun but not JunB or JunD in a dose-dependent manner and promoted the binding of c-Jun to the ABCB1 promoter region in Bewo cells. rTNF-α also increased the uptake of two P-gp-specific substrates, Rh123 and DiOC₂(3), a function reversed by the addition of SP600125 and SR11302. We also found that rTNF-α increased the efflux ratio of digoxin, an outcome that was reversed, as expected, by inhibiting c-Jun and P-gp binding activities. Furthermore, we identified that rTNF-α tightly regulates the molecule-transporting activity of P-gp by promoting the phosphorylation of c-Jun.

CONCLUSIONS

TNF-α activates P-gp to promote placental molecule-transporting activity by directly upregulating c-Jun expression and phosphorylation. These findings demonstrate the clinical significance of TNF-α in modulating the placental barrier, which plays an important role in protecting fetus against harmful drugs.

Phytochemicals That Interfere With Drug Metabolism and Transport, Modifying Plasma Concentration in Humans and Animals

Phytochemicals (Pch) present in fruits, vegetables and other foods, are known to inhibit or induce drug metabolism and transport. An exhaustive search was performed in five databases covering from 2000 to 2021. Twenty-one compounds from plants were found to modulate CYP3A and/or P-gp activities and modified the pharmacokinetics and the therapeutic effect of 27 different drugs. Flavonols, flavanones, flavones, stilbenes, diferuloylmethanes, tannins, protoalkaloids, flavans, hyperforin and terpenes, reduce plasma concentration of cyclosporine, simvastatin, celiprolol, midazolam, saquinavir, buspirone, everolimus, nadolol, tamoxifen, alprazolam, verapamil, quazepam, digoxin, fexofenadine, theophylline, indinavir, clopidogrel. Anthocyanins, flavonols, flavones, flavanones, flavonoid glycosides, stilbenes, diferuloylmethanes, catechin, hyperforin, alkaloids, terpenes, tannins and protoalkaloids increase of plasma concentration of buspirone, losartan, diltiazem, felodipine, midazolam, cyclosporine, triazolam, verapamil, carbamazepine, diltiazem, aripiprazole, tamoxifen, doxorubicin, paclitaxel, nicardipine. Interactions between Pchs and drugs affect the gene expression and enzymatic activity of CYP3A and P-gp transporter, which has an impact on their bioavailability; such that co-administration of drugs with food, beverages and food supplements can cause a subtherapeutic effect or overdose. Therefore, it is important for the clinician to consider these interactions to obtain a better therapeutic effect.

Expression of the Stem Cell Marker ABCB5 in Normal and Tumor Tissues

BACKGROUND/AIM

The ATP-binding cassette subfamily B member 5 (ABCB5) transporter plays a pivotal role in melanocyte progenitor cell fusion and has been identified as a tumor-initiating cell marker. In this study, we determined ABCB5 expression in normal tissues among various species, i.e., Homo sapiens, Mus musculus (mouse), Rattus norvegicus (rat), Sus scrofa domesticus (pig), Gallus gallus (chicken), Anser anser (goose), Poecilia reticulata (Guppy fish), and Lumbricus terrestris (earthworm), as well as 426 biopsies of different human tumor types (colorectal, cervical, endometrium, vaginal, nasopharyngeal, kidney, breast, colon, prostate, pancreas, lung, gallbladder, bladder, brain, liver, skin, small intestine, testis, tonsil, uterus, thyroid, stomach, esophagus, fallopian, parotid, and ovary).

MATERIALS AND METHODS

Using immunohistochemical staining, ABCB5 expression was detected and evaluated in formalin-fixed, paraffin-embedded sections.

RESULTS

High ABCB5 expression was found in normal tissues in specialized cells with secretory and excretory functions, chorionic villi of the placenta, hepatocytes, and blood-tissue barrier sites in the brain and testis. Besides, heterogeneous expression of ABCB5 was also observed in many different tumor types derived from breast, endometrium, ovary, uterus, cervix, prostate, lung, brain, colon, liver, nasopharynx, and others.

CONCLUSION

The localization of ABCB5 in different normal tissues suggests that this protein has an excretory pumping role for physiological metabolites and xenobiotics. This physiological role highlighted its possible impact on the development of multidrug resistance in tumors. Further studies are required to establish the possible clinical significance of ABCB5 as a predictive marker for drug resistance and as a prognostic marker for patient survival.

Relevance of ABC Transporters in Drug Development

ATP-binding cassette (ABC) transporters play a critical role in protecting vital organs such as the brain and placenta against xenobiotics, as well as in modulating the pharmacological and toxicological profile of several drug candidates by restricting their penetration through cellular and tissue barriers. This review paper provides a description of the structure and function of ABC transporters as well as the role of P-glycoprotein, multidrug resistance-associated protein 2 and breast cancer resistance protein in the disposition of drugs. Furthermore, a review of the in vitro and in vivo techniques for evaluating the interaction between drugs and ABC transporters are provided.

P-glycoprotein: new insights into structure, physiological function, regulation and alterations in disease

The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.

Epifriedelanol enhances adriamycin-induced cytotoxicity towards K562/ADM cells by down regulating of P-gp and MRP2

1. Multidrug resistance (MDR) is a critical issue during chemotherapy of cancers. Epifriedelanol (Epi) is the effective compounds from the Root Bark of Ulmus davidiana. This study aims to investigate the effect of Epi on MDR and its potential mechanism in the adriamycin (Adr)-resistant K562/ADM cells.2. The effect of Epi on MDR, P-glycoprotein (P-gp) and multidrug resistance-associated proteins (MRPs) were investigated in the adriamycin (Adr)-resistant K562/ADM cells. In addition, the alterations of nuclear receptor pregnane X receptor (PXR) and constitutive androstane receptor (CAR) mRNA expression levels in K562/ADM cells after Epi treatment were also examined.3. Epi significantly enhanced Adr-induced cytotoxicity towards K562/ADM cells. Combination of Epi and Adr can significantly reduce the 50% inhibitory concentration (IC₅₀) of K562/ADM cells to Adr. The reversal fold was 1.83 and 3.64 after treated with Epi at 10 and 20 μM, respectively. The intracellular accumulation of Adr was significant increased after exposure to Epi at 5-20 μM compared with the control group. Furthermore, Epi treatment significantly decreased the mRNA and protein expression of P-gp and MRP2 in K562/ADM cells.4. The present study demonstrated that Epi could enhance Adr-induced cytotoxicity towards K562/ADM cells accompanied by the down-regulation of P-gp and MRP2.

The Resistance of Cancer Cells to Palbociclib, a Cyclin-Dependent Kinase 4/6 Inhibitor, is Mediated by the ABCB1 Transporter

Palbociclib was approved by the United States Food and Drug Administration for use, in combination with letrozole, as a first-line treatment for estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) postmenopausal metastatic breast cancer. However, recent studies show that palbociclib may be an inhibitor of the ABCB1 transporter, although this remains to be elucidated. Therefore, we conducted experiments to determine the interaction of palbociclib with the ABCB1 transporter. Our in vitro results indicated that the efficacy of palbociclib was significantly decreased in the ABCB1-overexpressing cell lines. Furthermore, the resistance of ABCB1-overexpressing cells to palbociclib was reversed by 3 μM of the ABCB1 inhibitor, verapamil. Moreover, the incubation of ABCB1-overexpressing KB-C2 and SW620/Ad300 cells with up to 5 μM of palbociclib for 72 h, significantly upregulated the protein expression of ABCB1. The incubation with 3 µM of palbociclib for 2h significantly increased the intracellular accumulation of [³H]-paclitaxel, a substrate of ABCB1, in ABCB1 overexpressing KB-C2 cells but not in the corresponding non-resistant parental KB-3-1 cell line. However, the incubation of KB-C2 cells with 3 μM of palbociclib for 72 h decreased the intracellular accumulation of [³H]-paclitaxel due to an increase in the expression of the ABCB1 protein. Palbociclib produced a concentration-dependent increase in the basal ATPase activity of the ABCB1 transporter (EC₅₀ = 4.73 μM). Molecular docking data indicated that palbociclib had a high binding affinity for the ABCB1 transporter at the substrate binding site, suggesting that palbociclib may compete with other ABCB1 substrates for the substrate binding site of the ABCB1. Overall, our results indicate that palbociclib is a substrate for the ABCB1 transporter and that its in vitro anticancer efficacy is significantly decreased in cancer cells overexpressing the ABCB1.

Clinical Significance and Potential Mechanisms of ATP Binding Cassette Subfamily C Genes in Hepatocellular Carcinoma

The purpose of this investigation was to assess the diagnostic and prognostic significance of ATP binding cassette subfamily C (ABCC) genes in hepatocellular carcinoma (HCC). The Student t-test was used to compare the expression level of ABCCs between HCC and paraneoplastic tissues. Receiver operating characteristic curve (ROC) analysis was applied for diagnostic efficiency assessment. The Kaplan-Meier method and Cox proportional hazards model were respectively applied for survival analysis. Genes with prognostic significance were subsequently used to construct prognostic models. From the perspective of genome-wide enrichment analysis, the mechanisms of prognosis-related ABCC genes were attempted to be elaborated by gene set enrichment analysis (GSEA). It was observed in the TCGA database that ABCC1, ABCC4, ABCC5, and ABCC10 were significantly upregulated in tumor tissues, while ABCC6 and ABCC7 were downregulated in HCC tissues. Receiver operating characteristic analysis revealed that ABCC7 might be a potential diagnostic biomarker in HCC. ABCC1, ABCC4, ABCC5, and ABCC6 were significantly related to the prognosis of HCC in the TCGA database. The prognostic significance of ABCC1, ABCC4, ABCC5, and ABCC6 was also observed in the Guangxi cohort. In the Guangxi cohort, both polymerase chain reaction and IHC (immunohistochemical) assays demonstrated higher expression of ABCC1, ABCC4, and ABCC5 in HCC compared to liver tissues, while the opposite was true for ABCC6. GSEA analysis indicated that ABCC1 was associated with tumor differentiation, nod-like receptor signal pathway, and so forth. It also revealed that ABCC4 might play a role in HCC by regulating epithelial-mesenchymal transition, cytidine analog pathway, met pathway, and so forth. ABCC5 might be associated with the fatty acid metabolism and KRT19 in HCC. ABCC6 might impact the cell cycle in HCC by regulating E2F1 and myc. The relationship between ABCC genes and immune infiltration was explored, and ABCC1,4,5 were found to be positively associated with infiltration of multiple immune cells, while ABCC6 was found to be the opposite. In conclusion, ABCC1, ABCC4, ABCC5, and ABCC6 might be prognostic biomarkers in HCC. The prognostic models constructed with ABCC1, ABCC4, ABCC5, and ABCC6 had satisfactory efficacy.

Natural Phaeosphaeride A Derivatives Overcome Drug Resistance of Tumor Cells and Modulate Signaling Pathways

In the present study, natural phaeosphaeride A (PPA) derivatives are synthesized. Anti-tumor studies are carried out on the PC3, K562, HCT-116, THP-1, MCF-7, A549, NCI-H929, Jurkat, and RPMI8226 tumor cell lines, and on the human embryonic kidney (HEK293) cell line. All the compounds synthesized turned out to have better efficacy than PPA towards the tumor cell lines listed. Among them, three compounds exhibited an ability to overcome the drug resistance of tumor cells associated with the overexpression of the P-glycoprotein by modulating the work of this transporter. Luminex xMAP technology was used to assess the effect of five synthesized compounds on the activation of intracellular kinase cascades in A431 cells. MILLIPLEX MAP Multi-Pathway Magnetic Bead 9-Plex was used, which allowed for the simultaneous detection of the following nine phosphorylated protein markers of the main intracellular signaling pathways: a universal transcription factor that controls the expression of immune-response genes, apoptosis and cell cycle NFκB (pS536); cAMP-dependent transcription factor (CREB (pS133); mitogen-activated kinase p38 (pT180/pY182); stress-activated protein kinase JNK (pT183/pY185); ribosomal SK; transcription factors STAT3 (pS727) and STAT5A/B (pY694/699); protein kinase B (Akt) (pS473); and kinase regulated by extracellular signals ERK1/2 (pT185/pY187). The effect of various concentrations of PPA derivatives on the cell culture was studied using xCelligence RTCA equipment. The compounds were found to modulate JNK, ERK1/2, and p38 signaling pathways. The set of activated kinase cascades suggests that oxidative stress is the main probable mechanism of the toxic action of PPA derivatives.

Evaluation of the effect of isobutyl paraben and 2-ethyl hexyl paraben on p-glycoprotein functional expression in rats: a pharmacokinetic study

BACKGROUND

Pharmaceutical excipients have been shown to influence drug disposition through modulating transport protein.

OBJECTIVES

This study assessed the effect of single dose administration of parabens on the pharmacokinetics (PK) of digoxin, a probe substrate of p-glycoprotein (p-gp), in vivo. Also, the effect of multiple dosing of parabens on p-gp expression was examined.

METHODS

Rats were randomized into four groups that received either the vehicle, 25mg/kg verapamil, 100mg/kg isobutyl paraben, or 100mg/kg 2-ethyl hexyl paraben, which was followed by giving 0.2mg/kg digoxin via oral gavage. Blood samples were collected at different time points, digoxin concentration was measured using LC/MS-MS, and digoxin PK parameters were estimated. Another set of rats received multiple doses of parabens for 14 days which was followed by measuring intestinal and hepatic mRNA expression of p-gp using qRT-PCR.

RESULTS

Single dose administration of verapamil significantly increased Cmax (by 60.4%) and AUC0-t (by 61.7%) of digoxin compared to the control group, while the PK parameters of digoxin in rats exposed to parabens were not significantly different from the control. Consistently, the mRNA expression of p-gp in intestine and liver was not affected by parabens treatment.

CONCLUSIONS

The lack of isobutylparaben and 2-ethylhexyl paraben effect on p-gp may suggest the insignificant interaction of parabens with p-gp drug substrates, which could be of safety considerations when designing pharmaceutical formulations.

Fatigue in breast cancer patients on chemotherapy: a cross-sectional study exploring clinical, biological, and genetic factors

Background

Cancer-related fatigue (CRF) is one of the most common and distressing complaints reported by cancer patients during chemotherapy considerably impacting all aspects of a patient’s life (physical, psychosocial, professional, and socioeconomic). The aim of this study was to assess the severity of cancer-related fatigue in a group of breast cancer patients undergoing chemotherapy and explore the association between fatigue scores and sociodemographic, clinical, biological, psychiatric, and genetic factors.

Methods

A cross-sectional pilot study carried out at the oncology outpatient unit of Hôtel-Dieu de France University Hospital recruited 67 breast cancer patients undergoing chemotherapy between November 2017 and June 2019 to evaluate fatigue using the EORTC QLQ-C30 scale (European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire). Genotyping for seven gene polymorphisms (COMT, DRD2, OPRM1, CLOCK, PER2, CRY2, ABCB1) was performed using the Lightcycler^® (Roche).

Results

The prevalence of fatigue was 46.3%. Multivariable analysis taking the fatigue score as the dependent variable showed that a higher number of cycles and a lower hemoglobin level were significantly associated with higher odds of exhibiting fatigue. Moreover, having at least one C allele for DRD2 SNP (vs. TT) was significantly associated with a 4.09 higher odds of expressing fatigue compared to TT patients. Finally, patients with at least one C allele for CLOCK SNP tended to display higher fatigue levels than TT patients.

Conclusions

Our study showed that anemic breast cancer patients with a high number of chemotherapy cycles and those carrying at least one C allele for DRD2 and CLOCK SNPs are at greater risk of exhibiting fatigue. Since no previous research has reported such genetic results, future studies are necessary to confirm our findings.

Structure-Function Relationships in the Human P-Glycoprotein (ABCB1): Insights from Molecular Dynamics Simulations

P-Glycoprotein (P-gp) is a transmembrane protein belonging to the ATP binding cassette superfamily of transporters, and it is a xenobiotic efflux pump that limits intracellular drug accumulation by pumping compounds out of cells. P-gp contributes to a reduction in toxicity, and has broad substrate specificity. It is involved in the failure of many cancer and antiviral chemotherapies due to the phenomenon of multidrug resistance (MDR), in which the membrane transporter removes chemotherapeutic drugs from target cells. Understanding the details of the ligand–P-gp interaction is therefore critical for the development of drugs that can overcome the MDR phenomenon, for the early identification of P-gp substrates that will help us to obtain a more effective prediction of toxicity, and for the subsequent outdesign of substrate properties if needed. In this work, a series of molecular dynamics (MD) simulations of human P-gp (hP-gp) in an explicit membrane-and-water environment were performed to investigate the effects of binding different compounds on the conformational dynamics of P-gp. The results revealed significant differences in the behaviour of P-gp in the presence of active and non-active compounds within the binding pocket, as different patterns of movement were identified that could be correlated with conformational changes leading to the activation of the translocation mechanism. The predicted ligand–P-gp interactions are in good agreement with the available experimental data, as well as the estimation of the binding-free energies of the studied complexes, demonstrating the validity of the results derived from the MD simulations.

The effect of photodynamic therapy on head and neck squamous cell carcinoma cell lines using spirulina platensis with different laser energy densities

BACKGROUND

Considering the anti-cancer properties of spirulina platensis (S. platensis), we aimed to investigate the effectiveness of this algae as a novel natural photosensitizer for photodynamic therapy (PDT) against oral and hypopharyngeal cancer cells. The appropriate laser energy density to apply during PDT was also determined.

METHODS AND MATERIALS

CAL-27, FaDu and HGF cell lines were exposed to S. platensis with concentrations of 0.3 g/l and 0.6 g/l and were irradiated with 635 nm diode laser using 2, 4, 12, and 24 J/cm² energy densities with constant power. MTT assay was performed to investigate cell viability and cytotoxicity after 24 h. The results were analyzed using two-way ANOVA and post hoc Tukey tests (P-value<0.05).

RESULTS

survival rate in CAL-27 (P-Value<0.001) and FaDu (P-Value<0.001) cell lines were significantly different following irradiation with various laser energy densities. Different concentrations of S. platensis had no significant effect on the viability of CAL-27 cells (P-Value=0.158) and FaDu cells (P-Value=0.072) and showed no significant cytotoxicity against HGF cells, with or without laser.

CONCLUSION

S. platensis could be considered as a novel safe and effective natural photosensitizer for cancer PDT with no cytotoxic effect on normal cells. When combined with laser using appropriate energy densities, it has the ability to induce death in oral and hypopharyngeal cancer cell lines.

Emerging nanotechnology based combination therapies of taxanes for multiple drug-resistant cancers

'One drug- one target' to 'multiple drug- multiple targets' paradigm shifted to produce combination therapies, have found great outcomes to overcome multiple drug resistance (MDR). MDR is a significant barrier to the delivery of taxane-based anticancer medicines such as docetaxel, paclitaxel, and cabazitaxel. Due to MDR induced by drug efflux transporters, clinical application of these medications is impeded. To date, nanoformulations such as liposomes, micelles, polymeric nanoparticles, and gold nanoparticles have been investigated to deliver taxanes alone and in combination to reverse drug resistance. Despite the fact that various groups have already looked into taxane nano formulations in the literature, there isn't much in the way of polypharmacology and advanced nanoformulations with a focus on MDR. In this overview, we briefly covered the insights regarding MDR, difficulties related to current pharmaceutical products of taxanes, combination therapies of taxanes to combat MDR, all of which can be used to delve into cancer treatment.

Cardamonin inhibits the expression of P-glycoprotein and enhances the anti-proliferation of paclitaxel on SKOV3-Taxol cells

Paclitaxel is widely used in the first-line treatment of ovarian cancer. Nevertheless, the development of acquired resistance to paclitaxel is a major obstacle for the therapy in clinic. Cardamonin is a novel anticancer chalcone which exhibits a wide range of pharmacological activities. However, the effect of cardamonin on paclitaxel-resistant ovarian cancer cells and its underlying molecular mechanisms are unknown. Here, we revealed whether cardamonin had a resensitivity for paclitaxel and furtherly explored the underlying mechanisms on SKOV3-Taxol cells. Our results showed that cardamonin combined with paclitaxel had a synergistic effect of anti-proliferation in SKOV3-Taxol cells, and CI was less than one. Cells apoptosis and G2/M phase arrest were enhanced by cardamonin with paclitaxel in a concentration-dependent way on SKOV3-Taxol cells (P < 0.05). Cardamonin significantly increased drug accumulation in SKOV3-Taxol cells (P < 0.05). Similar to verapamil, cardamonin decreased MDR1 mRNA and P-gp expression (P < 0.05). Cardamonin restrained NF-κB activation in SKOV3-Taxol cells (P < 0.05). Inhibitory effect of P-gp and NF-κB p65 (nuclear protein) expression was enhanced by cardamonin combined with PDTC, a NF-κB inhibitor. Cardamonin significantly inhibited the upregulation of NF-κB p65 (nuclear protein) and P-gp expression induced by TNF-α (P < 0.05). Taken together, cardamonin enhanced the effect of paclitaxel on inhibiting cell proliferation, inducing apoptosis and G2/M phase arrest, and then strengthened the cytotoxic effect of paclitaxel in SKOV3-Taxol cells. The mechanism might be involved in inhibition of P-gp efflux pump, reducing MDR1 mRNA and P-gp expression by cardamonin via suppression of NF-κB activation in SKOV3-Taxol cells.

Small extracellular vesicles in cancer

Extracellular vesicles (EV) are lipid-bilayer enclosed vesicles in submicron size that are released from cells. A variety of molecules, including proteins, DNA fragments, RNAs, lipids, and metabolites can be selectively encapsulated into EVs and delivered to nearby and distant recipient cells. In tumors, through such intercellular communication, EVs can regulate initiation, growth, metastasis and invasion of tumors. Recent studies have found that EVs exhibit specific expression patterns which mimic the parental cell, providing a fingerprint for early cancer diagnosis and prognosis as well as monitoring responses to treatment. Accordingly, various EV isolation and detection technologies have been developed for research and diagnostic purposes. Moreover, natural and engineered EVs have also been used as drug delivery nanocarriers, cancer vaccines, cell surface modulators, therapeutic agents and therapeutic targets. Overall, EVs are under intense investigation as they hold promise for pathophysiological and translational discoveries. This comprehensive review examines the latest EV research trends over the last five years, encompassing their roles in cancer pathophysiology, diagnostics and therapeutics. This review aims to examine the full spectrum of tumor-EV studies and provide a comprehensive foundation to enhance the field. The topics which are discussed and scrutinized in this review encompass isolation techniques and how these issues need to be overcome for EV-based diagnostics, EVs and their roles in cancer biology, biomarkers for diagnosis and monitoring, EVs as vaccines, therapeutic targets, and EVs as drug delivery systems. We will also examine the challenges involved in EV research and promote a framework for catalyzing scientific discovery and innovation for tumor-EV-focused research.

Oxygen transport to mammalian cell and bacteria using nano-sized liposomes encapsulating oxygen molecules

Hypoxic microenvironments emerge as tumor grow, leading to the over-expression and stabilization of hypoxia-inducible factor 1-alpha (HIF-1α). HIF-1α lowers the sensitization against chemotherapy, radiation therapy and photodynamic therapy in cancer. In this study, nano-sized oxygen carrier, namely oxygen dissolved nanoliposome (ODL) was synthesized, and oxygen was efficiently delivered to different types of mammalian cells to help relieve hypoxia. ODL confirmed that oxygen was released without inducing toxicity to cells. After artificially creating hypoxia in cancer cells, normal cells, and immune cells; various parameters such as cell morphology, HIF-1α expression, and degree of hypoxia were examined. The cellular environment was found to be altered by treatment with the ODL. Under hypoxia, the shape of the cells changed, and the cells began to die. After treatment with the ODL, the degree of hypoxia was reduced, indicating that HIF-1α expression and the rate of cell death decreased. Furthermore, bacteria proliferation was observed with the ODL. Therefore, ODL can be used for oxygen delivery platform in cancer therapy. ODL has a potential application in other microorganisms which needs future research.

Reduced physiologically-based pharmacokinetic model of dabigatran etexilate-dabigatran and its application for prediction of intestinal P-gp-mediated drug-drug interactions

BACKGROUND

Dabigatran etexilate (DABE) has been suggested as a clinical probe for intestinal P-glycoprotein (P-gp)-mediated drug-drug interaction (DDI) studies and, as an alternative to digoxin. Clinical DDI data with various P-gp inhibitors demonstrated a dose-dependent inhibition of P-gp with DABE. The aims of this study were to develop a joint DABE (prodrug)-dabigatran reduced physiologically-based-pharmacokinetic (PBPK) model and to evaluate its ability to predict differences in P-gp DDI magnitude between a microdose and a therapeutic dose of DABE.

METHODS

A joint DABE-dabigatran PBPK model was developed with a mechanistic intestinal model accounting for the regional P-gp distribution in the gastrointestinal tract. Model input parameters were estimated using DABE and dabigatran pharmacokinetic (PK) clinical data obtained after administration of DABE alone or with a strong P-gp inhibitor, itraconazole, and over a wide range of DABE doses (from 375 µg to 400 mg). Subsequently, the model was used to predict extent of DDI with additional P-gp inhibitors and with different DABE doses.

RESULTS

The reduced DABE-dabigatran PBPK model successfully described plasma concentrations of both prodrug and metabolite following administration of DABE at different dose levels and when co-administered with itraconazole. The model was able to capture the dose dependency in P-gp mediated DDI. Predicted magnitude of itraconazole P-gp DDI was higher at the microdose (predicted vs. observed median fold-increase in AUC_+inh/AUC_control (min-max) = 5.88 (4.29-7.93) vs. 6.92 (4.96-9.66) ) compared to the therapeutic dose (predicted median fold-increase in AUC_+inh/AUC_control = 3.48 (2.37-4.84) ). In addition, the reduced DABE-dabigatran PBPK model predicted successfully the extent of DDI with verapamil and clarithromycin as P-gp inhibitors. Model-based simulations of dose staggering predicted the maximum inhibition of P-gp when DABE microdose was concomitantly administered with itraconazole solution; simulations also highlighted dosing intervals required to minimise the DDI risk depending on the DABE dose administered (microdose vs. therapeutic).

CONCLUSIONS

This study provides a modelling framework for the evaluation of P-gp inhibitory potential of new molecular entities using DABE as a clinical probe. Simulations of dose staggering and regional differences in the extent of intestinal P-gp inhibition for DABE microdose and therapeutic dose provide model-based guidance for design of prospective clinical P-gp DDI studies.

3D organoids derived from the small intestine: An emerging tool for drug transport research

Small intestine in vitro models play a crucial role in drug transport research. Although conventional 2D cell culture models, such as Caco-2 monolayer, possess many advantages, they should be interpreted with caution because they have relatively poor physiologically reproducible phenotypes and functions. With the development of 3D culture technology, pluripotent stem cells (PSCs) and adult somatic stem cells (ASCs) show remarkable self-organization characteristics, which leads to the development of intestinal organoids. Based on previous studies, this paper reviews the application of intestinal 3D organoids in drug transport mediated by P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance protein 2 (MRP2). The advantages and limitations of this model are also discussed. Although there are still many challenges, intestinal 3D organoid model has the potential to be an excellent tool for drug transport research.

Intestinal Excretion, Intestinal Recirculation, and Renal Tubule Reabsorption Are Underappreciated Mechanisms That Drive the Distribution and Pharmacokinetic Behavior of Small Molecule Drugs

Drug reabsorption following biliary excretion is well-known as enterohepatic recirculation (EHR). Renal tubular reabsorption (RTR) following renal excretion is also common but not easily assessed. Intestinal excretion (IE) and enteroenteric recirculation (EER) have not been recognized as common disposition mechanisms for metabolically stable and permeable drugs. IE and intestinal reabsorption (IR:EHR/EER), as well as RTR, are governed by dug concentration gradients, passive diffusion, active transport, and metabolism, and together they markedly impact disposition and pharmacokinetics (PK) of small molecule drugs. Disruption of IE, IR, or RTR through applications of active charcoal (AC), transporter knockout (KO), and transporter inhibitors can lead to changes in PK parameters. The impacts of intestinal and renal reabsorption on PK are under-appreciated. Although IE and EER/RTR can be an intrinsic drug property, there is no apparent strategy to optimize compounds based on this property. This review seeks to improve understanding and applications of IE, IR, and RTR mechanisms.

Mastering the Gram-negative bacterial barrier - Chemical approaches to increase bacterial bioavailability of antibiotics

To win the battle against resistant, pathogenic bacteria, novel classes of anti-infectives and targets are urgently needed. Bacterial uptake, distribution, metabolic and efflux pathways of antibiotics in Gram-negative bacteria determine what we here refer to as bacterial bioavailability. Understanding these mechanisms from a chemical perspective is essential for anti-infective activity and hence, drug discovery as well as drug delivery. A systematic and critical discussion of in bacterio, in vitro and in silico assays reveals that a sufficiently accurate holistic approach is still missing. We expect new findings based on Gram-negative bacterial bioavailability to guide future anti-infective research.

Xanthones as P-glycoprotein modulators and their impact on drug bioavailability

Introduction: P-glycoprotein (P-gp) is an important efflux pump responsible for the extruding of many endogenous and exogenous substances out of the cells. P-gp can be modulated by different molecules - including xanthone derivatives - to surpass the multidrug resistance (MDR) phenomenon through P-gp inhibition, or to serve as an antidotal strategy in intoxication scenarios through P-gp induction/activation.Areas covered: This review provides a perspective on P-gp modulators, with particular focus on xanthonic derivatives, highlighting their ability to modulate P-gp expression and/or activity, and the potential impact of these effects on the pharmacokinetics, pharmacodynamics and toxicity of P-gp substrates.Expert opinion: Xanthones, of natural or synthetic origin, are able to modulate P-gp, interfering with its protein synthesis or with its mechanism of action, by decreasing or increasing its efflux capacity. These modulatory effects make the xanthonic scaffold a promising source of new derivatives with therapeutic potential. However, the mechanisms beyond the xanthones-mediated P-gp modulation and the chemical characteristics that make them more potent P-gp inhibitors or inducers/activators are still understudied. Furthermore, a new window of opportunity exists in the neuropathologies field, where xanthonic derivatives with potential to modulate P-gp should be further explored to optimize the prevention/treatment of brain pathologies.