Double trouble - dual outflow tract obstruction in congenital heart disease: a case report.

BACKGROUND: Double chambered right ventricle is a rare congenital heart disease that is characterised by the presence of an anomalous muscle bundle that divides the right ventricle into a low pressure superior (distal) chamber and a high pressure inferior (proximal) chamber. It is found in association with a ventricular septal defect in 90% cases with other associations being tetralogy of Fallot, transposition of great vessels, atrial septal defect and Ebstein's anomaly. On the other hand, subaortic membrane is a form of discrete subaortic stenosis that is characterised by a membranous diaphragm in the subvalvular location of the left ventricular outflow tract. Both of these entities are responsible for causing subvalvular outflow tract obstruction. The occurrence of double chambered right ventricle in association with subaortic membrane is an extremely rare entity with only a few case reports available in the literature. CASE REPORT: A 13-year-old male child with history of chest pain and palpitations presented to the outpatient department of a tertiary care center. Transthoracic echocardiography revealed a subaortic membrane producing a pressure gradient across the left ventricular outflow tract with dilatation of the right atrium and right ventricle which could not be fully evaluated on echocardiography. Cardiac computed tomography was then performed which additionally revealed an anomalous muscle bundle coursing across the right ventricle from the septum to the subinfundibular region creating a double chambered right ventricle. The patient was then taken up for reconstruction of right ventricular outflow tract and resection of subaortic membrane. CONCLUSION: Right and left outflow tract obstructions are rare congenital lesions which when seen in combination, become even more infrequent. Echocardiography is a robust tool that detects turbulent flow to identify such lesions. However, poor acoustic window may sometimes result in missing these lesions and computed tomography in such situations can play an important role in detection as well as complete preoperative imaging evaluation.

Quantifying collective intelligence in human groups.

Collective intelligence (CI) is critical to solving many scientific, business, and other problems, but groups often fail to achieve it. Here, we analyze data on group performance from 22 studies, including 5,279 individuals in 1,356 groups. Our results support the conclusion that a robust CI factor characterizes a group's ability to work together across a diverse set of tasks. We further show that CI is predicted by the proportion of women in the group, mediated by average social perceptiveness of group members, and that it predicts performance on various out-of-sample criterion tasks. We also find that, overall, group collaboration process is more important in predicting CI than the skill of individual members.

Incidence and Factors Associated With Acne in Transgender Adolescents on Testosterone: A Retrospective Cohort Study.

OBJECTIVE: This retrospective cohort study aimed to assess incidence and predictors of acne among transgender adolescents receiving testosterone. METHODS: We analyzed records of patients aged <18 years, assigned female at birth, seen at Children's Healthcare of Atlanta Pediatric Endocrinology clinic for testosterone initiation between January 1, 2016, and January 1, 2019, with at least 1-year follow-up documented. Bivariable analyses to determine the association of clinical and demographic factors with new acne diagnosis were performed. RESULTS: Of 60 patients, 46 (77%) did not have baseline acne, but of those 46 patients, 25 (54%) developed acne within 1 year of testosterone initiation. Overall incidence proportion was 70% at 2 years; patients who used progestin prior to or during follow-up were more likely to develop acne than nonusers (92% vs 33%, P <.001). CONCLUSION: Transgender adolescents starting testosterone, particularly those taking progestin, should be monitored for acne development and treated proactively by hormone providers and dermatologists.

Targeting the untargetable: RB1-deficient tumours are vulnerable to Skp2 ubiquitin ligase inhibition.

Proteins that regulate the cell cycle are accumulated and degraded in a coordinated manner during the transition from one cell cycle phase to the next. The rapid loss of a critical protein, for example, to allow the cell to move from G1/G0 to S phase, is often regulated by its ubiquitination and subsequent proteasomal degradation. Protein ubiquitination is mediated by a series of three ligases, of which the E3 ligases provide the specificity for a particular protein substrate. One such E3 ligase is SCFSkp1/Cks1, which has a substrate recruiting subunit called S-phase kinase-associated protein 2 (Skp2). Skp2 regulates cell proliferation, apoptosis, and differentiation, can act as an oncogene, and is overexpressed in human cancer. A primary target of Skp2 is the cyclin-dependent kinase inhibitor p27 (CDKN1b) that regulates the cell cycle at several points. The RB1 tumour suppressor gene regulates Skp2 activity by two mechanisms: by controlling its mRNA expression, and by an effect on Skp2's enzymatic activity. For the latter, the RB1 protein (pRb) directly binds to the substrate-binding site on Skp2, preventing protein substrates from being ubiquitinated and degraded. Inactivating mutations in RB1 are common in human cancer, becoming more frequent in aggressive, metastatic, and drug-resistant tumours. Hence, RB1 mutation leads to the loss of pRb, an unrestrained increase in Skp2 activity, the unregulated decrease in p27, and the loss of cell cycle control. Because RB1 mutations lead to the loss of a functional protein, its direct targeting is not possible. This perspective will discuss evidence validating Skp2 as a therapeutic target in RB1-deficient cancer.

Potassium Concentrations in Transgender Women Using Spironolactone: A Retrospective Chart Review.

OBJECTIVE: To assess the incidence of hyperkalemia in transgender women using spironolactone. METHODS: This was a retrospective chart review of transgender women who received gender-affirming hormone therapy that included spironolactone between January 2000 and September 2018. Forty-four participants who had paired potassium concentrations documented and were on spironolactone were included and analyzed. Study outcomes included the incidence of hyperkalemia (serum potassium concentrations > 5.0 mmol/L), the relationship between the duration of treatment and degree of hyperkalemia, and difference between serum potassium concentrations at the beginning of spironolactone treatment versus last serum potassium concentrations. RESULTS: The median age of the participants was 36.5 years. The cohort was predominantly non-Hispanic White (32/44). No serum potassium concentration was >5.5 mmol/L, and all participants had serum creatinine level of <2 mg/dL. Median duration of treatment was 25 months (range 2-92 months) and 140 potassium measurements were available. The mean potassium concentration (3.87 mmol/L) before the initiation of spironolactone was lower than the mean potassium concentration (4.03 mmol/L) while on spironolactone (mean difference, 0.16 mmol/L, P = .013). The regression ß, that is, the average change in potassium concentration per 1 additional month of treatment duration, was -.001 (95% CI [-.004, .001]; P = .255) signifying no relation between treatment duration and spironolactone use. CONCLUSION: No participant had laboratory evidence of significant hyperkalemia (K > 5.5 mmol/L) after initiation of spironolactone. Frequent measurement of potassium concentrations might be unnecessary in transgender women taking spironolactone in patients with serum creatinine levels of <2 mg/dL.

Theory and Least Squares Fitting of CW ESR Saturation Spectra Using the MOMD Model.

CW saturation experiments are widely used in ESR studies of relaxation processes in proteins and lipids. We develop the theory of saturation in ESR spectra in terms of its close relation with that of 2D-ELDOR. Our treatment of saturation is then based on the microscopic order macroscopic disorder (MOMD) model and can be used to fit the full CW saturation spectrum, rather than fitting just the peak-peak amplitude as a function of microwave field B 1 as is commonly done. This requires fewer experiments to yield effects on T 1, as well as provides a more extensive dynamic structural picture, for example, for scanning experiments on different protein sites. The code is released as a publicly available software package in Python that can be used to fit CW saturation spectra from biological samples of interest.

MG53 suppresses tumor progression and stress granule formation by modulating G3BP2 activity in non-small cell lung cancer.

BACKGROUND: Cancer cells develop resistance to chemotherapeutic intervention by excessive formation of stress granules (SGs), which are modulated by an oncogenic protein G3BP2. Selective control of G3BP2/SG signaling is a potential means to treat non-small cell lung cancer (NSCLC). METHODS: Co-immunoprecipitation was conducted to identify the interaction of MG53 and G3BP2. Immunohistochemistry and live cell imaging were performed to visualize the subcellular expression or co-localization. We used shRNA to knock-down the expression MG53 or G3BP2 to test the cell migration and colony formation. The expression level of MG53 and G3BP2 in human NSCLC tissues was tested by western blot analysis. The ATO-induced oxidative stress model was used to examine the effect of rhMG53 on SG formation. Moue NSCLC allograft experiments were performed on wild type and transgenic mice with either knockout of MG53, or overexpression of MG53. Human NSCLC xenograft model in mice was used to evaluate the effect of MG53 overexpression on tumorigenesis. RESULTS: We show that MG53, a member of the TRIM protein family (TRIM72), modulates G3BP2 activity to control lung cancer progression. Loss of MG53 results in the progressive development of lung cancer in mg53-/- mice. Transgenic mice with sustained elevation of MG53 in the bloodstream demonstrate reduced tumor growth following allograft transplantation of mouse NSCLC cells. Biochemical assay reveals physical interaction between G3BP2 and MG53 through the TRIM domain of MG53. Knockdown of MG53 enhances proliferation and migration of NSCLC cells, whereas reduced tumorigenicity is seen in NSCLC cells with knockdown of G3BP2 expression. The recombinant human MG53 (rhMG53) protein can enter the NSCLC cells to induce nuclear translation of G3BP2 and block arsenic trioxide-induced SG formation. The anti-proliferative effect of rhMG53 on NSCLC cells was abolished with knockout of G3BP2. rhMG53 can enhance sensitivity of NSCLC cells to undergo cell death upon treatment with cisplatin. Tailored induction of MG53 expression in NSCLC cells suppresses lung cancer growth via reduced SG formation in a xenograft model. CONCLUSION: Overall, these findings support the notion that MG53 functions as a tumor suppressor by targeting G3BP2/SG activity in NSCLCs.

Plasminogen activator inhibitor (PAI) trap3, an exocellular peptide inhibitor of PAI-1, attenuates the rearrangement of F-actin and migration of cancer cells.

BACKGROUND: The protein plasminogen activator inhibitor-1 (PAI-1), an inhibitor specific for urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA), has been shown to have a key role in cancer metastases. Currently, it is unknown as to whether the exocellular inhibition of PAI-1 can inhibit the migration of cancer cells. METHODS: By fusing the mutated serine protease domain (SPD) of uPA and human serum albumin (HSA), PAItrap3, a protein that traps PAI-1, was synthesized and experiments were conducted to determine if exocellular PAItrap3 attenuates PAI-1-induced cancer cell migration in vitro. RESULTS: PAItrap3 (0.8 µM) significantly inhibited the motility of MCF-7, MDA-MB-231, HeLa and 4T1 cancer cells, by 90%, 50%, 30% and 20%, respectively, without significantly altering their proliferation. The PAI-1-induced rearrangement of F-actin was significantly inhibited by PAItrap3, which produced a decrease in the number of cell protrusions by at least 20%. CONCLUSIONS: In vitro, PAItrap3 inhibited PAI-1-induced cancer cell migration, mainly through inhibiting the rearrangement of F-actin. Overall, these results, provided they can be extrapolated to humans, suggest that the PAItrap3 protein could be used as an exocellular inhibitor to attenuate cancer metastases.

Microsecond dynamics in proteins by two-dimensional ESR. II. Addressing computational challenges.

Two-dimensional electron-electron double resonance (2D-ELDOR) provides extensive insight into molecular motions. Recent developments permitting experiments at higher frequencies (95 GHz) provide molecular orientational resolution, enabling a clearer description of the nature of the motions. In previous work, we provided simulations for the case of domain motions within proteins that are themselves slowly tumbling in a solution. In order to perform these simulations, it was found that the standard approach of solving the relevant stochastic Liouville equation using the efficient Lanczos algorithm for this case breaks down, so algorithms were employed that rely on the Arnoldi iteration. While they lead to accurate simulations, they are very time-consuming. In this work, we focus on a variant known as the rational Arnoldi algorithm. We show that this can achieve a significant reduction in computation time. The stochastic Liouville matrix, which is of very large dimension, N, is first reduced to a much smaller dimension, m, e.g., from N ∼ O(104) to m ∼ 60, that spans the relevant Krylov subspace from which the spectrum is predicted. This requires the selection of the m frequency shifts to be utilized. A method of adaptive shift choice is introduced to optimize this selection. We also find that these procedures help in optimizing the pruning procedure that greatly reduces the dimension of the initial N dimensional stochastic Liouville matrix in such subsequent computations.

An Active Inference Model of Collective Intelligence.

Collective intelligence, an emergent phenomenon in which a composite system of multiple interacting agents performs at levels greater than the sum of its parts, has long compelled research efforts in social and behavioral sciences. To date, however, formal models of collective intelligence have lacked a plausible mathematical description of the relationship between local-scale interactions between autonomous sub-system components (individuals) and global-scale behavior of the composite system (the collective). In this paper we use the Active Inference Formulation (AIF), a framework for explaining the behavior of any non-equilibrium steady state system at any scale, to posit a minimal agent-based model that simulates the relationship between local individual-level interaction and collective intelligence. We explore the effects of providing baseline AIF agents (Model 1) with specific cognitive capabilities: Theory of Mind (Model 2), Goal Alignment (Model 3), and Theory of Mind with Goal Alignment (Model 4). These stepwise transitions in sophistication of cognitive ability are motivated by the types of advancements plausibly required for an AIF agent to persist and flourish in an environment populated by other highly autonomous AIF agents, and have also recently been shown to map naturally to canonical steps in human cognitive ability. Illustrative results show that stepwise cognitive transitions increase system performance by providing complementary mechanisms for alignment between agents' local and global optima. Alignment emerges endogenously from the dynamics of interacting AIF agents themselves, rather than being imposed exogenously by incentives to agents' behaviors (contra existing computational models of collective intelligence) or top-down priors for collective behavior (contra existing multiscale simulations of AIF). These results shed light on the types of generic information-theoretic patterns conducive to collective intelligence in human and other complex adaptive systems.

Microsecond dynamics in proteins by two-dimensional ESR: Predictions.

Two-dimensional electron-electron double resonance (2D-ELDOR) provides extensive insight into molecular motions. Recent developments permitting experiments at higher frequencies (95 GHz) provide molecular orientational resolution, enabling a clearer description of the nature of the motions. In this work, simulations are provided for the example of domain motions within proteins that are themselves slowly tumbling in solution. These show the nature of the exchange cross-peaks that are predicted to develop in real time from such domain motions. However, we find that the existing theoretical methods for computing 2D-ELDOR experiments over a wide motional range begin to fail seriously when applied to very slow motions characteristic of proteins in solution. One reason is the failure to obtain accurate eigenvectors and eigenvalues of the complex symmetric stochastic Liouville matrices describing the experiment when computed by the efficient Lanczos algorithm in the range of very slow motion. Another, perhaps more serious, issue is that these matrices are "non-normal," such that for the very slow motional range even rigorous diagonalization algorithms do not yield the correct eigenvalues and eigenvectors. We have employed algorithms that overcome both these issues and lead to valid 2D-ELDOR predictions even for motions approaching the rigid limit. They are utilized to describe the development of cross-peaks in 2D-ELDOR at 95 GHz for a particular case of domain motion.

Modulating ROS to overcome multidrug resistance in cancer.

The successful treatment of cancer has significantly improved as a result of targeted therapy and immunotherapy. However, during chemotherapy, cancer cells evolve and can acquire "multidrug resistance" (MDR), which significantly limits the efficacy of cancer treatment and impacts patient survival and quality of life. Among the approaches to reverse MDR, modulating reactive oxidative species (ROS) may represent a strategy to kill MDR cancer cells that are mechanistically diverse. ROS in cancer cells play a central role in regulating and inducing apoptosis, thereby modulating cancer cells proliferation, survival and drug resistance. The levels of ROS and the activity of scavenging/anti-oxidant enzymes in drug resistant cancer cells are typically increased compared to non-MDR cancer and normal cells. Consequently, MDR cancer cells may be more susceptible to alterations in ROS levels. Numerous studies suggest that compounds modulating cellular ROS levels can enhance MDR cancer cell death and sensitize MDR cancer cells to certain chemotherapeutic drugs. In the current review, we discuss the critical and targetable redox-regulating enzymes, including mitochondrial electron transport chain (ETC) complexes, NADPH oxidases (NOXs), enzymes related to glutathione metabolism, glutamate/cystine antiporter xCT, thioredoxin reductases (TrxRs), nuclear factor erythroid 2-related factor 2 (Nrf2), and their roles in regulating cellular ROS levels, drug resistance as well as their clinical significance. We also discuss and summarize the findings in the past decade regarding the efficacy of ROS modulators for the treatment of MDR cancer alone or as sensitizing compounds. Compounds that are efficacious in modulating ROS generation represent a prominent class of drug candidates that warrants evaluation in clinical trials for patients harboring MDR cancers.

Ciprofloxacin Enhances the Chemosensitivity of Cancer Cells to ABCB1 Substrates.

ABCB1 is one of the major drug efflux transporters that is known to cause multidrug resistance (MDR) in cancer patients receiving chemotherapy for the treatment of solid tumors and hematological malignancies. Inhibition of ABCB1 efflux function is important for maintaining the intracellular concentration of chemotherapeutic drugs. Here, we evaluated ciprofloxacin for its ability to reverse MDR caused by the overexpression of ABCB1. Cytotoxicity of ciprofloxacin was determined by the MTT assay. The chemosensitizing effects of ciprofloxacin were determined in combination with ABCB1 substrates. The intracellular accumulation and efflux of ABCB1 substrates was measured by a scintillation counter, and protein expression was determined by the Western blotting. Vanadate-sensitive ATPase assay was performed to determine the effect of ciprofloxacin on the ATPase activity of ABCB1, and docking analysis was done to determine the interaction of ciprofloxacin with ABCB1. Ciprofloxacin significantly potentiated the cytotoxic effects of ABCB1 substrates in ABCB1-overexpressing cells. Furthermore, ciprofloxacin increased the intracellular accumulation and decreased the efflux of [³H]-paclitaxel without altering the expression of ABCB1. Ciprofloxacin stimulated the ATPase activity of ABCB1 in a concentration-dependent manner. Our findings showed that ciprofloxacin potently inhibits the ABCB1 efflux function and it has potential to be developed as a combination anticancer therapy.

Chk1 Inhibitor MK-8776 Restores the Sensitivity of Chemotherapeutics in P-glycoprotein Overexpressing Cancer Cells.

P-glycoprotein (P-gp), which is encoded by the ATP-binding cassette (ABC) transporter subfamily B member 1 (ABCB1) gene, is one of the most pivotal ABC transporters that transport its substrates across the cell membrane. Its overexpression is one of the confirmed causes of multidrug resistance (MDR), which results in the failure of cancer treatment. Here, we report that checkpoint kinase (Chk) 1 inhibitor MK-8776, a drug candidate in clinical trial, can restore the sensitivity of chemotherapeutics that are substrates of P-gp in KB-C2, SW620/Ad300 cells and human embryonic kidney (HEK)293/ABCB1 cells that overexpress P-gp. MK-8776 remarkably enhanced the cellular [3H]-paclitaxel accumulation and suppressed the efflux function of P-gp without reducing its expression and affecting its cellular localization in cancer cells. Furthermore, MK-8776 (0-40 µM) stimulated the activity of ATPase in P-gp, which was 4.1-fold greater than the control. In addition, MK-8776 formed a cation-π bond and π-π interaction with key residues of the substrate-binding site in P-gp, as indicated by computer-aided molecular docking study. Our study indicated that MK-8776 may significantly enhance the sensitivity of chemotherapeutics that are substrates of P-gp, providing important information for its application in the reversal of MDR.

Tetrandrine Interaction with ABCB1 Reverses Multidrug Resistance in Cancer Cells Through Competition with Anti-Cancer Drugs Followed by Downregulation of ABCB1 Expression.

The overexpression of ABC transporters induced by anticancer drugs has been found to be the main cause of multidrug resistance. It is actually also a strategy by which cancer cells escape being killed. Tetrandrine is a natural product extracted from the stem of Tinospora crispa. In this study, tetrandrine showed synergistic cytotoxic activity in combinational use with chemotherapeutic drugs, such as Doxorubicin, Vincristine, and Paclitaxel, in both drug-induced and MDR1 gene-transfected cancer cells that over-expressed ABCB1/P-glycoprotein. Tetrandrine stimulated P-glycoprotein ATPase activity, decreased the efflux of [3H]-Paclitaxel and increased the intracellular accumulation of [3H]-Paclitaxel in KB-C2 cells. Furthermore, SW620/Ad300 and KB-C2 cells pretreated with 1 µM tetrandrine for 72 h decreased P-glycoprotein expression without changing its cellular localization. This was demonstrated through Western blotting and immunofluorescence analysis. Interestingly, down-regulation of P-glycoprotein expression was not correlated with gene transcription, as the MDR1 mRNA level exhibited a slight fluctuation in SW620/Ad300 and KB-C2 cells at 0, 24, 48, and 72 h treatment time points. In addition, molecular docking analysis predicted that tetrandrine had inhibitory potential with the ABCB1 transporter. Our results suggested that tetrandrine can antagonize MDR in both drug-selected and MDR1 gene-transfected cancer cells by down regulating the expression of the ABCB1 transporter, followed by increasing the intracellular concentration of chemotherapeutic agents. The combinational therapy using tetrandrine and other anticancer drugs could promote the treatment efficiency of drugs that are substrates of ABCB1.

Voruciclib, a Potent CDK4/6 Inhibitor, Antagonizes ABCB1 and ABCG2-Mediated Multi-Drug Resistance in Cancer Cells.

BACKGROUND/AIMS: The overexpression of ATP-Binding Cassette (ABC) transporters has known to be one of the major obstacles impeding the success of chemotherapy in drug resistant cancers. In this study, we evaluated voruciclib, a CDK 4/6 inhibitor, for its chemo-sensitizing activity in ABCB1- and ABCG2- overexpressing cells. METHODS: Cytotoxicity and reversal effect of voruciclib was determined by MTT assay. The intracellular accumulation and efflux of ABCB1 and ABCG2 substrates were measured by scintillation counter. The effects on expression and intracellular localization of ABCB1 and ABCG2 proteins were determined by Western blotting and immunofluorescence, respectively. Vanadate-sensitive ATPase assay was done to determine the effect of voruciclib on the ATPase activity of ABCB1 and ABCG2. Flow cytometric analysis was done to determine the effect of voruciclib on apoptosis of ABCB1 and ABCG2-overexpressing cells and docking analysis was done to determine the interaction of voruciclib with ABCB1 and ACBG2 protein. RESULTS: Voruciclib significantly potentiated the effect of paclitaxel and doxorubicin in ABCB1-overexpressing cells, as well as mitoxantrone and SN-38 in ABCG2-overexpressing cells. Voruciclib moderately sensitized ABCC10- overexpressing cells to paclitaxel, whereas it did not alter the cytotoxicity of substrates of ABCC1. Furthermore, voruciclib increased the intracellular accumulation and decreased the efflux of substrate anti-cancer drugs from ABCB1- or ABCG2-overexpressing cells. However, voruciclib did not alter the expression or the sub-cellular localization of ABCB1 or ABCG2. Voruciclib stimulated the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner. Lastly, voruciclib exhibited a drug-induced apoptotic effect in ABCB1- or ABCG2- overexpressing cells. CONCLUSION: Voruciclib is currently a phase I clinical trial drug. Our findings strongly support its potential use in combination with conventional anti-cancer drugs for cancer chemotherapy.

The development of anticancer ruthenium(ii) complexes: from single molecule compounds to nanomaterials.

Cancer is rapidly becoming the top killer in the world. Most of the FDA approved anticancer drugs are organic molecules, while metallodrugs are very scarce. The advent of the first metal based therapeutic agent, cisplatin, launched a new era in the application of transition metal complexes for therapeutic design. Due to their unique and versatile biochemical properties, ruthenium-based compounds have emerged as promising anti-cancer agents that serve as alternatives to cisplatin and its derivertives. Ruthenium(iii) complexes have successfully been used in clinical research and their mechanisms of anticancer action have been reported in large volumes over the past few decades. Ruthenium(ii) complexes have also attracted significant attention as anticancer candidates; however, only a few of them have been reported comprehensively. In this review, we discuss the development of ruthenium(ii) complexes as anticancer candidates and biocatalysts, including arene ruthenium complexes, polypyridyl ruthenium complexes, and ruthenium nanomaterial complexes. This review focuses on the likely mechanisms of action of ruthenium(ii)-based anticancer drugs and the relationship between their chemical structures and biological properties. This review also highlights the catalytic activity and the photoinduced activation of ruthenium(ii) complexes, their targeted delivery, and their activity in nanomaterial systems.

GSK1904529A, a Potent IGF-IR Inhibitor, Reverses MRP1-Mediated Multidrug Resistance.

Overexpression of multidrug-resistant efflux transporters is one of the major causes of chemotherapy failure. MRP1, a 190 kDa efflux transporter, confers resistance to a wide of range of chemotherapeutic drugs. Here we study the cellular effects of GSK1904529A in reversing MRP1-mediated drug resistance. Cytotoxicity of GSK1904529A was determined by MTT assay. Reversal effects of GSK1904529A in combination with MRP1 substrates were determined. The intracellular accumulation and efflux of MRP1 substrate was measured by scintillation counter and protein expression was determined by Western blotting analysis. Cell cycle effects of GSK1904529A in combination with MRP1 substrates were determined by flow cytometric analysis. GSK1904529A, at non-toxic concentrations, enhanced the cytotoxicity of MRP1 substrates in HEK293/MRP1 cells. Furthermore, GSK1904529A increased the intracellular accumulation of [3 H]-vinblastine by inhibiting the efflux function of MRP1. GSK1904529A did not alter the expression level of MRP1, induced a G0/G1 phase cell cycle arrest. Our results indicated that GSK1904529A significantly increased the sensitivity of MRP1 overexpressing cells to chemotherapeutic agents. Furthermore, GSK1904529A enhanced the efficacy of chemotherapeutic drugs that are substrates of MRP1. J. Cell. Biochem. 118: 3260-3267, 2017. © 2017 Wiley Periodicals, Inc.

Design, synthesis and biological evaluation of benzamide and phenyltetrazole derivatives with amide and urea linkers as BCRP inhibitors.

Breast cancer resistant protein (BCRP/ABCG2), a 72kDa plasma membrane transporter protein is a member of ABC transporter superfamily. Increased expression of BCRP causes increased efflux and therefore, reduced intracellular accumulation of many unrelated chemotherapeutic agents leading to multidrug resistance (MDR). A series of 31 benzamide and phenyltetrazole derivatives with amide and urea linkers has been synthesized to serve as potential BCRP inhibitors in order to overcome BCRP-mediated MDR. The target derivatives were tested for their cytotoxicity and reversal effects in human non-small cell lung cancer cell line H460 and mitoxantrone resistant cell line H460/MX20 using the MTT assay. In the benzamide series, compounds 6 and 7 exhibited a fold resistance of 1.51 and 1.62, respectively at 10µM concentration which is similar to that of FTC, a known BCRP inhibitor. Compounds 27 and 31 were the most potent analogues in the phenyltetrazole series with amide linker with a fold resistance of 1.39 and 1.32, respectively at 10µM concentration. For the phenyltetrazole series with urea linker, 38 exhibited a fold resistance of 1.51 which is similar than that of FTC and is the most potent compound in this series. The target compounds did not exhibit reversal effect in P-gp overexpressing resistant cell line SW620/Ad300 suggesting that they are selective BCRP inhibitors.

The modulation of ABC transporter-mediated multidrug resistance in cancer: a review of the past decade.

ATP-binding cassette (ABC) transporters represent one of the largest and oldest families of membrane proteins in all extant phyla from prokaryotes to humans, which couple the energy derived from ATP hydrolysis essentially to translocate, among various substrates, toxic compounds across the membrane. The fundamental functions of these multiple transporter proteins include: (1) conserved mechanisms related to nutrition and pathogenesis in bacteria, (2) spore formation in fungi, and (3) signal transduction, protein secretion and antigen presentation in eukaryotes. Moreover, one of the major causes of multidrug resistance (MDR) and chemotherapeutic failure in cancer therapy is believed to be the ABC transporter-mediated active efflux of a multitude of structurally and mechanistically distinct cytotoxic compounds across membranes. It has been postulated that ABC transporter inhibitors known as chemosensitizers may be used in combination with standard chemotherapeutic agents to enhance their therapeutic efficacy. The current paper reviews the advance in the past decade in this important domain of cancer chemoresistance and summarizes the development of new compounds and the re-evaluation of compounds originally designed for other targets as transport inhibitors of ATP-dependent drug efflux pumps.