Single-cell transcriptional signature-based drug repurposing and in vitro evaluation in colorectal cancer

BACKGROUND

The need for intelligent and effective treatment of diseases and the increase in drug design costs have raised drug repurposing as one of the effective strategies in biomedicine. There are various computational methods for drug repurposing, one of which is using transcription signatures, especially single-cell RNA sequencing (scRNA-seq) data, which show us a clear and comprehensive view of the inside of the cell to compare the state of disease and health.

METHODS

In this study, we used 91,103 scRNA-seq samples from 29 patients with colorectal cancer (GSE144735 and GSE132465). First, differential gene expression (DGE) analysis was done using the ASAP website. Then we reached a list of drugs that can reverse the gene signature pattern from cancer to normal using the iLINCS website. Further, by searching various databases and articles, we found 12 drugs that have FDA approval, and so far, no one has reported them as a drug in the treatment of any cancer. Then, to evaluate the cytotoxicity and performance of these drugs, the MTT assay and real-time PCR were performed on two colorectal cancer cell lines (HT29 and HCT116).

RESULTS

According to our approach, 12 drugs were suggested for the treatment of colorectal cancer. Four drugs were selected for biological evaluation. The results of the cytotoxicity analysis of these drugs are as follows: tezacaftor (IC10 = 19 µM for HCT-116 and IC10 = 2 µM for HT-29), fenticonazole (IC10 = 17 µM for HCT-116 and IC10 = 7 µM for HT-29), bempedoic acid (IC10 = 78 µM for HCT-116 and IC10 = 65 µM for HT-29), and famciclovir (IC10 = 422 µM for HCT-116 and IC10 = 959 µM for HT-29).

CONCLUSIONS

Cost, time, and effectiveness are the main challenges in finding new drugs for diseases. Computational approaches such as transcriptional signature-based drug repurposing methods open new horizons to solve these challenges. In this study, tezacaftor, fenticonazole, and bempedoic acid can be introduced as promising drug candidates for the treatment of colorectal cancer. These drugs were evaluated in silico and in vitro, but it is necessary to evaluate them in vivo.

Epigenetic disruption of histone deacetylase-2 accelerated apoptotic signaling and retarded malignancy in gastric cells

Background: The objective of this research was to determine whether HDAC2 function is associated with gastric cancer progression. Methods: HDAC2 was knocked out in EPG85.257 cells using CRISPR/Cas9 and tumorigenesis pathways were evaluated. Results: Cell proliferation, colony formation, wound healing and transwell invasion were inhibited in ΔHDAC2:EPG85.257 cells. Quantitative analyses revealed a significant downregulation of MMP1, p53, Bax, MAPK1, MAPK3, pro-Caspase3, ERK1/2, p-ERK1/2, AKT1/2/3, p-AKT1/2/3, p-NF-κB (p65), Twist, Snail and p-FAK transcripts/proteins, while SIRT1, PTEN, p21 and Caspase3 were upregulated in ΔHDAC2:EPG85.257 cells. Conclusion: These results indicated that HDAC2 enhanced migration, colony formation and transmigration ability. HDAC2 inhibition may improve gastric cancer chemotherapy pathways.

Engineered mesoporous silica nanoparticles, new insight nanoplatforms into effective cancer gene therapy

The use of nucleic acid to control the expression of genes relevant to tumor progression is a key therapeutic approach in cancer research. Therapeutics based on nucleic acid provide novel concepts for untreatable targets. Nucleic acids as molecular medications must enter the target cell to be effective and obstacles in the systemic delivery of DNA or RNA limit their use in a clinical setting. The creation of nucleic acid delivery systems based on nanoparticles in order to circumvent biological constraints is advancing quickly. The ease of synthesis and surface modification, biocompatibility, biodegradability, cost-effectiveness and high loading capability of nucleic acids have prompted the use of mesoporous silica nanoparticles (MSNs) in gene therapy. The unique surface features of MSNs facilitate their design and decoration for high loading of nucleic acids, immune system evasion, cancer cell targeting, controlled cargo release, and endosomal escape. Reports have demonstrated successful therapeutic outcomes with the administration of a variety of engineered MSNs capable of delivering genes to tumor sites in laboratory animals. This comprehensive review of studies about siRNA, miRNA, shRNA, lncRNA and CRISPR/Cas9 delivery by MSNs reveals engineered MSNs as a safe and efficient system for gene transfer to cancer cells and cancer mouse models.

DeeP4med: deep learning for P4 medicine to predict normal and cancer transcriptome in multiple human tissues

BACKGROUND

P4 medicine (predict, prevent, personalize, and participate) is a new approach to diagnosing and predicting diseases on a patient-by-patient basis. For the prevention and treatment of diseases, prediction plays a fundamental role. One of the intelligent strategies is the design of deep learning models that can predict the state of the disease using gene expression data.

RESULTS

We create an autoencoder deep learning model called DeeP4med, including a Classifier and a Transferor that predicts cancer's gene expression (mRNA) matrix from its matched normal sample and vice versa. The range of the F1 score of the model, depending on tissue type in the Classifier, is from 0.935 to 0.999 and in Transferor from 0.944 to 0.999. The accuracy of DeeP4med for tissue and disease classification was 0.986 and 0.992, respectively, which performed better compared to seven classic machine learning models (Support Vector Classifier, Logistic Regression, Linear Discriminant Analysis, Naive Bayes, Decision Tree, Random Forest, K Nearest Neighbors).

CONCLUSIONS

Based on the idea of DeeP4med, by having the gene expression matrix of a normal tissue, we can predict its tumor gene expression matrix and, in this way, find effective genes in transforming a normal tissue into a tumor tissue. Results of Differentially Expressed Genes (DEGs) and enrichment analysis on the predicted matrices for 13 types of cancer showed a good correlation with the literature and biological databases. This led that by using the gene expression matrix, to train the model with features of each person in a normal and cancer state, this model could predict diagnosis based on gene expression data from healthy tissue and be used to identify possible therapeutic interventions for those patients.

CRISPR/Cas9 as precision and high-throughput genetic engineering tools in gastrointestinal cancer research and therapy

Gastrointestinal cancer (GI) is one of the most serious and health-threatening diseases worldwide. Many countries have encountered an escalating prevalence of shock. Therefore, there is a pressing need to clarify the molecular pathogenesis of these cancers. The use of high-throughput technologies that allow the precise and simultaneous investigation of thousands of genes, proteins, and metabolites is a critical step in disease diagnosis and cure. Recent innovations have provided easy and reliable methods for genome investigation, including TALENs, ZFNs, and the CRISPR/Cas9 (clustered regularly interspaced palindromic repeats system). Among these, CRISPR/Cas9 has been revolutionary tool in genetic research. Recent years were prosperous years for CRISPR by the discovery of novel Cas enzymes, the Nobel Prize, and the development of critical clinical trials. This technology utilizes comprehensive information on genes associated with tumor development, provides high-throughput libraries for tumor therapy by developing screening platforms, and generates rapid tools for cancer therapy. This review discusses the various applications of CRISPR/Cas9 in genome editing, with a particular focus on genome manipulation, including infection-related genes, RNAi targets, pooled library screening for identification of unknown driver mutations, and molecular targets for gastrointestinal cancer modeling. Finally, it provides an overview of CRISPR/Cas9 clinical trials, as well as the challenges associated with its use.

Silencing of α-N-acetylgalactosaminidase in the gastric cancer cells amplified cell death and attenuated migration, while the multidrug resistance remained unchanged

Although the elevated level of the α-N-acetylgalactosaminidase enzyme (encoded by the NAGA gene) is a well-recognized feature of cancer cells; little research works have been undertaken on the cancer malignancy mechanisms. The effects of NAGA gene downregulation on cancer cells' features such as drug resistance, impaired programmed cell death, and migration were analyzed in this study. The cells grew exponentially with a doubling time of 30 h in an optimal condition. Toxicity of daunorubicin chemotherapy drug on NAGA-transfected EPG85.257RDB cells was evaluated in comparison to control cells and no significant change was recorded. Quantitative transcript analyses and protein levels revealed that the MDR1 pump almost remained unchanged during the study. Moreover, the NAGA gene downregulation enhanced the late apoptosis rate in EPG85.257RDB cells at 24 h posttransfection. The investigated expression level of genes and proteins involved in the TNFR2 signaling pathway, related to cancer cell apoptosis, showed considerable alterations after NAGA silencing as well. MAP3K14 and CASP3 genes were downregulated while IL6, RELA, and TRAF2 experienced an upregulation. Also, NAGA silencing generally diminished the migration ability of EPG85.257RDB cells and the MMP1 gene (as a critical gene in metastasis) expression decreased significantly. The expression of the p-FAK protein, which is located in the downstream of the α₂ β₁ integrin signaling pathway, was reduced likewise. It could be concluded that despite drug resistance, NAGA silencing resulted in augmentative and regressive effects on cell death and migration.

siRNA delivery using intelligent chitosan-capped mesoporous silica nanoparticles for overcoming multidrug resistance in malignant carcinoma cells

Although siRNA is a promising technology for cancer gene therapy, effective cytoplasmic delivery has remained a significant challenge. In this paper, a potent siRNA transfer system with active targeting moieties toward cancer cells and a high loading capacity is introduced to inhibit drug resistance. Mesoporous silica nanoparticles are of great potential for developing targeted gene delivery. Amino-modified MSNs (NH₂-MSNs) were synthesized using a modified sol–gel method and characterized by FTIR, BET, TEM, SEM, X-ray diffraction, DLS, and ¹H-NMR. MDR1-siRNA was loaded within NH₂-MSNs, and the resulting negative surface was capped by functionalized chitosan as a protective layer. Targeting moieties such as TAT and folate were anchored to chitosan via PEG-spacers. The loading capacity of siRNA and the protective effect of chitosan for siRNA were determined by gel retardation assay. MTT assay, flow cytometry, real-time PCR, and western blot were performed to study the cytotoxicity, cellular uptake assay, targeting evaluation, and MDR1 knockdown efficiency. The synthesized NH₂-MSNs had a particle size of ≈ 100 nm and pore size of ≈ 5 nm. siRNA was loaded into NH₂-MSNs with a high loading capacity of 20% w/w. Chitosan coating on the surface of siRNA-NH₂-MSNs significantly improved the siRNA protection against enzyme activity compared to naked siRNA-NH₂-MSNs. MSNs and modified MSNs did not exhibit significant cytotoxicity at therapeutic concentrations in the EPG85.257-RDB and HeLa-RDB lines. The folate-conjugated nanoparticles showed a cellular uptake of around two times higher in folate receptor-rich HeLa-RDB than EPG85.257-RDB cells. The chitosan-coated siRNA-NH2-MSNs produced decreased MDR1 transcript and protein levels in HeLa-RDB by 0.20 and 0.48-fold, respectively. The results demonstrated that functionalized chitosan-coated siRNA-MSNs could be a promising carrier for targeted cancer therapy. Folate-targeted nanoparticles were specifically harvested by folate receptor-rich HeLa-RDB and produced a chemosensitized phenotype of the multidrug-resistant cancer cells.

Pharmacodynamic mechanisms of anti-inflammatory drugs on the chemosensitization of multidrug-resistant cancers and the pharmacogenetics effectiveness

Drug resistance as a remarkable issue in cancer treatment is associated with inflammation which occurs through complex chemical reactions in the tumor microenvironment. Recent studies have implicated that glucocorticoids and NSAIDs are mainly useful combinations for inflammatory response modulation in chemotherapeutic protocols for cancer treatment. Immunosuppressive actions of glucocorticoids and NSAIDs are mainly mediated by the transrepression or activation regulation of inflammatory genes with different DNA-bound transcription factors including AP-1, NFAT, NF-κB, STAT and also, varying functions of COX enzymes in cancer cells. Interestingly, many investigations have proved the benefits of these anti-inflammatory agents in the quenching of multidrug resistance pathways. Numerous analyses on the ABC transporter promoters showed conserved nucleotide sequences with several DNA response elements that participate in transcriptional regulation. Furthermore, genetic variations in nucleotide sequences of membrane transporters were strongly associated with changes in these transporters' expression or function and a substantial impact on systemic drug exposure and toxicity. It appeared that several polymorphisms in MDR transporter genes especially MDR1 have influenced the regulatory mechanisms and explained differences in glucocorticoid responses.

Genetically modified Pichia pastoris, a powerful resistant factory for gold and palladium bioleaching and nanostructure heavy metal biosynthesis

A metal-resistant engineered Pichia pastoris was developed here to fulfil the metal bioleaching in aqueous conditions. Parent and recombinant yeasts were grown in YPD medium containing different concentrations of ion metals. XRD, electron microscopy and particle size analyser were used for the characterisation and the nanoparticle analyses. The nanoparticle production kinetics were studied by ICP-OES. The cytotoxicity of nanoparticles was assayed against human cell lines. Media colours changed to a range from purplish-brown to grey during early fermentation stages. The maximum biosorption capacities were recorded 81.23 and 493.35 mg/g for gold and palladium in batch conditions, respectively. Various physical investigations proved monodispersed spherical nanoparticles around 100 nm in size. Pure palladium nanoparticles and PdCl₂ represented the least cytotoxic potency towards T47D and EPG85.257 cells. The results demonstrated that the genetically modified yeast is a cost-effective, high-throughput, robust, and facile system for metal biosorption.

Inflammatory pathway interactions and cancer multidrug resistance regulation

Multidrug resistances against chemotherapeutics are among the major challenges related to cancer treatment. Recent studies have demonstrated that different conditions may tune the expression and activity of MDR transporters. For instance, inflammation occurs through a complex cytological process and chemical reactions in the most tumor microenvironment; it can play a critical role in cancer development and is capable of altering the expression and function of MDR transporters. Cytokines, interleukins, and prostaglandins are potent inflammatory mediators that can modulate the expression of MDRs at transcriptional and post-transcriptional levels in the most human cancer cells and tissues and potentially contribute to balance bioavailability of chemotherapeutic agents. Since cancer cases are usually accompanied by inflammatory responses, glucocorticoids and NSAIDs are the primary useful combination chemotherapies in a variety of cancer treatment protocols. In addition to the anti-inflammatory activities of these agents, they exert diverse modulatory effects on MDR-mediated drug resistance via specific mechanisms. Several factors, including cell and MDR-protein types, pharmacokinetics, and pharmacogenetics, mainly influence the regulatory mechanisms. Uncovering the networks between inflammation and multidrug resistance will be clinically helpful in the treatment of malignant cancers and decreasing the cancer mortality rates.

Intelligent TAT-coupled anti-HER2 immunoliposomes knock downed MDR1 to produce chemosensitize phenotype of multidrug resistant carcinoma

Gene therapy using biocompatible cationic liposomes is amongst promising approaches that decreases death from cancers. Here an invasive multidrug resistant cell model has been developed by lentiviral transfection. In parallel phospholipids have been covalently conjugated to TAT, MMP2, and Herceptin. The functional lipids have been mixed to generate intelligent liposome harboring small interfering RNA (siRNA) with high efficiency. The final liposomal complex was uniformly monodisperse and particle dimension and zeta-potential were respectively around 200 nm and -42.21 mV. Minimal cytotoxic effects have been reported for nanocarriers due to good biocompatibility of the selected phospholipids. Flourescence-activated cell sorter (FACS) analyses have been represented that surface trastuzumab and TAT specifically promote cellular uptake of liposomes in the malignant tumor cells. Assessment of MDR1 transcript and protein expression has been exhibited maximum significant downregulation around of 128-fold and 50-fold, respectively after 48 hr of liposome exposure. As it has been concluded, targeted liposomes may become a potential tool in gene delivery for improving chemotherapeutic efficiency in cancer treatment.

Unlike Butylcycloheptylprodigiosin, Isolated Undecylprodigiosin from Streptomyces parvulus Is Not a MDR1 and BCRP Substrate in Multidrug-Resistant Cancers

The search for new chemotherapeutics unaffected by efflux pumps would significantly increase life expectancy in patients with malignant cancers. In this study, butylcycloheptylprodigiosin and undecylprodigiosin were HPLC-purified and verified, using nuclear magnetic resonance spectroscopy. Cell cytotoxicity and transportation kinetics on multiple-drug resistance (MDR) cells were evaluated. Daunorubicin and butylcycloheptylprodigiosin were less toxic in the MDR1 overexpressing line, but undecylprodigiosin revealed potent toxicity toward MDR1 and BCRP expressing malignant cells. There was no noticeable change in MDR1 and BCRP transcripts during 3 days of treatment with prodiginines. While daunorubicin and mitoxantrone uptake from the cell environment significantly decreased with increasing multidrug resistance up to 46% and 62%, respectively, the accumulation of undecylprodigiosin and to a lesser extent butylcycloheptylprodigiosin in the resistance cells occurred cell- and dose-dependently via a passive diffusion process and were almost equally sensitive to the parent lines. The efflux of xenobiotics commenced immediately with different kinetics in various cells. A greater amount of daunorubicin and mitoxantrone were rapidly thrown out of their corresponding MDR cells in the absence of the specific inhibitor (3.01 and 1.81 dF/min, respectively) and represented functional efflux pumps. MDR pumps did not apparently influence undecylprodigiosin efflux patterns; but butylcycloheptylprodigiosin was partially removed from EPG85.257RDB cells at the rate of 2.66 and 1.41 dF/min in the absence and presence of verapamil, respectively.

Broad blocking of MDR efflux pumps by acetylshikonin and acetoxyisovalerylshikonin to generate hypersensitive phenotype of malignant carcinoma cells

Cytotoxic activities of acetylshikonin and acetoxyisovalerylshikonin alone and in combination with chemotherapeutic agents against parental and drug resistant cell lines were determined using the MTT assay. Effects of Shikonin derivatives on BCRP, MDR1 and MRP transcript and protein levels were relatively measured. Finally, accumulation and efflux kinetics were conducted. The results revealed cell- and concentration-dependency of the cell cytotoxicity. Acetylshikonin and acetoxyisovalerylshikonin transiently made the mRNA ocean turbulent, but FACS analyses using fluorescent-labeled antibodies showed no significant change in the MDR-protein levels. Functional kinetics revealed significant block of MDR1, BCRP and MRP transporter in the presence of shikonin derivatives. Maximum accumulation fold changes was quantified to be 4.4 and consequently, acetoxyisovalerylshikonin pretreated EPG85.257RDB cells was chemosensitized to daunorubicin tension 3.1-fold. Although, the MDR blockage was reported to follow time- and cell-dependent patterns, MDR1, BCRP and MRP2 responses to the shikonins are concentration-independent. These data suggest uncompetitive transporter blockage behavior of these agents. The results indicated that shikonin derivatives stimulate uptake and reduce efflux of chemotherapeutic agents in the malignant cancer cells, suggesting that chemotherapy in combination with shikonin compounds may be beneficial to cancer cells that overexpress multidrug resistance transporters.

ABC-transporter blockage mediated by xanthotoxin and bergapten is the major pathway for chemosensitization of multidrug-resistant cancer cells

Furanocoumarins derived from herbal and citrus extracts can act as antibacterial, antioxidant, immunomodulator, apoptotic, and selective anticancer agents, prompting a biological investigation to determine and predict their clinical therapeutic significance. Here, the cell cytotoxic effects of bergapten and xanthotoxin were analyzed alone and in combination with standard chemotherapeutics on three multidrug resistant cells and their nonresistant parental counterparts. The furanocoumarins modulatory effects on MDR1, BCRP, and MRP pump expression and function were investigated. Although quantitative real time PCR demonstrated that the MDR transcript level changes in a time dependent manner, flow cytometric analyses using fluorescent-labeled antibodies have indicated that bergapten and xanthotoxin had no significant effect on the protein levels. FACS analyses indicated that these prominent anticancer agents significantly blocked MDR1, BCRP, and MRP transporter function. Maximum furanocoumarin-mediated pump activity blockage in the MDR-resistant cells was quantified as 87% of normal and consequently, chemotherapeutic accumulation increased up to 2.7-fold and cytotoxicity tension increased 104-fold. MDR1 efflux kinetics also revealed that the maximum velocity and the pump affinity to daunorubicin were uncompetitively decreased. We conclude that bergapten and xanthotoxin are cytotoxic agents capable of preventing daunorubicin, mitoxantrone, and cisplatin binding to ABC-transporters and subsequently inhibiting their efflux out of cells and they may be a potential combination therapy for malignant cancers.

High-throughput bioaccumulation, biotransformation, and production of silver and selenium nanoparticles using genetically engineered Pichia pastoris

A genetically modified Pichia pastoris strain overexpressing a metal-resistant variant of cytochrome b5 reductase enzyme was developed for silver and selenium biosorption and for nanoparticle production. The maximum recombinant enzyme expression level was approximately 31 IU/ml in the intercellular fluid after 24 h of incubation, and the capacity of the recombinant biomass for the biosorption of silver and selenium in aqueous batch models were measured as 163.90 and 63.71 mg/g, respectively. The ions were reduced in the presence of enzyme, leading to the formation of stable 70-180 nm metal nanoparticles. Various instrumental analyses confirmed the well-dispersed and crystalline nature of the spherical nanometals. The purified silver and selenium nanoparticles exhibited at least 10-fold less cytotoxicity toward HDF, EPG85-257, and T47D cells than silver nitrate and selenium dioxide. These results revealed that the engineered Pichia strain is an eco-friendly, rapid, high-throughput, and versatile reduction system for nanometal production.

Celecoxib Up Regulates the Expression of Drug Efflux Transporter ABCG2 in Breast Cancer Cell Lines

Elevated expression of the drug efflux transporter ABCG2 seems to correlate with multidrug resistance of cancer cells. Specific COX-2 inhibitor celecoxib has been shown to enhance the sensitivity of cancer cells to anticancer drugs. To clarify whether ABCG2 inhibition is involved in the sensitizing effect of celecoxib, we investigated whether the expression of ABCG2 in breast cancer cell lines, could be modulated by celecoxib. The expression of the multidrug resistant gene (ABCG2) at mRNA and protein level was detected by real-time quantitative reverse transcription-polymerase chain reaction and flow cytometry analysis, respectively. Among three human breast cancer cell lines ABCG2 and COX-2 were highly expressed in MCF7-MX and MDA-MB-231 cells, respectively. The COX-2 inhibitor celecoxib up-regulated the expression of ABCG2 mRNA in MCF-7 and MCF7-MX cells, which was accompanied by increased ABCG2 protein expression. While celecoxib was able to block the 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated increase in COX-2 expression in MDA-MB-231 cells, it increased the expression of ABCG2 up to 4.27 times to the control level at mRNA level and with less intensity at protein level. Our findings provide evidence that celecoxib up-regulates ABCG2 expression in human breast cancer cells and proposed that ABCG2 is not involved in chemosensitizing effects of celecoxib.

The cell cycle arrest and the anti-invasive effects of nitrogen-containing bisphosphonates are not mediated by DBF4 in breast cancer cells

Recent work has shown that a DBF4 analog in yeast may be a target of nitrogen-containing bisphosphonates. DBF4 is an essential protein kinase required for DNA replication from primary eukaryotes to humans and appears to play a critical role in the S-phase checkpoint. It is also required for cell migration and cell surface adhesion. The effects of Pamidronate, risedronate, or zoledronate on cell viability and DBF4 expression were measured via MTT assays and western blotting. In addition, FACS cell cycle analyses and invasion assays were conducted in cells in the presence of nitrogen-containing bisphosphonates to identify any correlations between DBF4 expression and S-phase arrest or anti-invasive effects of the bisphosphonates. Zoledronate transiently down-regulated DBF4 expression in all three cell lines in the first 24 h of the experiment, but after 72 h, DBF4 expression returned to the control levels in all treated cells. Following treatment of the tumor cells with the bisphosphonates, the number of cells in S-phase was increased. Pamidronate and zoledronate showed anti-invasive effects in BT20 cells. The anti-invasive effects of pamidronate, risedronate and zoledronate appeared after 48 h of exposure. In MDA-MB231 cells a reduction of invasiveness was only observed after 72 h of the pamidronate exposure. We finally concluded that the anti-invasive and cell cycle arrest-inducing effects of nitrogen-containing bisphosphonates are not DBF4 mediated, and other mediators are therefore needed to explain the observed complex behaviors.

The anticancer agent prodigiosin is not a multidrug resistance protein substrate

The brilliant red pigments prodiginines are natural secondary metabolites that are produced by select species of Gram-negative and Gram-positive bacteria. These molecules have received significant attention due to their reported antibacterial, antifungal, immunosuppressive, and anticancer activities. In this study, a Serratia marcescens SER1 strain was isolated and verified using 16s rDNA. The prodigiosin was purified using silica chromatography and was analyzed by (1)H-NMR spectroscopy. The cell cytotoxic effects of the purified prodigiosin on multiple drug resistant cell lines that overexpress MDR1, BCRP, or MRP2 pumps were analyzed. Prodigiosin had nearly identical cytotoxic effects on the resistant cells in comparison to their parental lines. In agreement with the same prodigiosin cytotoxicity, FACS analysis of prodigiosin accumulation and efflux in MDR overexpressing cell lines also indicated that this pro-apoptotic agent operates independently of the presence of the MDR1, BCRP, or MRP transporter and may be a potential treatment for malignant cancer cells that overexpress multidrug resistance transporters.

Phorbol ester TPA modulates chemoresistance in the drug sensitive breast cancer cell line MCF-7 by inducing expression of drug efflux transporter ABCG2

Recent studies have indicated a link between levels of cyclooxygenase-2 (COX-2) and development of the multidrug resistance (MDR) phenotype. The ATP-binding cassette sub-family G member 2 (ABCG2) is a major MDR-related transporter protein that is frequently overexpressed in cancer patients. In this study, we aimed to evaluate any positive correlation between COX-2 and ABCG2 gene expression using the COX-2 inducer 12-O-tetradecanoylphorbol-13-acetate (TPA) in human breast cancer cell lines. ABCG2 mRNA and protein expression was studied using real-time RT-PCR and flow cytometry, respectively. A significant increase of COX-2 mRNA expression (up to 11-fold by 4 h) was induced by TPA in MDA-MB-231 cells, this induction effect being lower in MCF-7 cells. TPA caused a considerable increase up to 9-fold in ABCG2 mRNA expression in parental MCF-7 cells, while it caused a small enhancement in ABCG2 expression up to 67 % by 4 h followed by a time-dependent decrease in ABCG2 mRNA expression in MDA-MB-231 cells. TPA treatment resulted in a slight increase of ABCG2 protein expression in MCF-7 cells, while a time-dependent decrease in ABCG2 protein expression was occurred in MDA-MB-231 cells. In conclusion, based on the observed effects of TPA in MDA-Mb-231 cells, it is proposed that TPA up-regulates ABCG2 expression in the drug sensitive MCF-7 breast cancer cell line through COX-2 unrelated pathways.

Human cytochrome b5 reductase: structure, function, and potential applications

Cytochrome b5 reductase is a flavoprotein that is produced as two different isoforms that have different localizations. The amphipathic microsomal isoform, found in all cell types with the exception of erythrocytes, consists of one hydrophobic membrane-anchoring domain and a larger hydrophilic flavin catalytic domain. The soluble cytochrome b5 reductase isoform, found in human erythrocytes, is a truncated protein that is encoded by an alternative transcript and consists of the larger domain only. Cytochrome b5 reductase is involved in the transfer of reducing equivalents from the physiological electron donor, NADH, via an FAD domain to the small molecules of cytochrome b5. This protein has received much attention from researchers due to its involvement in many oxidation and reduction reactions, such as the reduction of methemoglobin to hemoglobin. Autosomal cytochrome b5 reductase gene deficiency manifests with the accumulation of oxidized Fe+3 and recessive congenital methemoglobinemia in humans. In this article, we provide a comprehensive overview of the structure and function of cytochrome b5 reductase from different eukaryotic sources and its potential use in the food industry, biosensor, and diagnostic areas.

Evaluation of indomethacin and dexamethasone effects on BCRP-mediated drug resistance in MCF-7 parental and resistant cell lines

Breast cancer resistance protein is a member of the ATP-binding cassette transporter G family that extrudes xenotoxins from cells, mediating drug resistance, and has been recognized as a major cause of failure of various carcinoma chemotherapies. In this study, the modulatory effects of dexamethasone and indomethacin on the cell cytotoxicity of mitoxantrone and on the BCRP protein activity in breast cancer cell lines were examined. MCF cells were seeded at 1 x 10(4) cells per well in 96-well flat-bottomed microplates for 48 hours and treated with increasing doses of dexamethasone, indomethacin, and novobiocin alone or preincubated with increasing doses of the drugs and then coexposed to mitoxantrone. Cell viability was measured after 1-4 days, using the MTT assay. BCRP activity was determined flow cytometrically by measuring mitoxantrone accumulation in the absence and presence of the inhibitor, novobiocin. Cotreatment of mitoxantrone with different concentrations of dexamethasone and indomethacin sensitized parental and resistant MCF-7 cells to mitoxantrone cytotoxicity. Dexamethasone increased the accumulation of mitoxantrone in the MCF-7/MX cell line, indicating an inhibition of BCRP. In spite of increased levels of mitoxantrone cytotoxicity in the presence of indomethacin, the accumulation of mitoxantrone was not increased in indomethacin-treated MCF cells.

Dexamethasone downregulates BCRP mRNA and protein expression in breast cancer cell lines

It is hypothesized that anti-inflammatory drugs regulate breast cancer resistance protein (BCRP) expression. Hence, we examined the effects of indomethacin and dexamethasone on BCRP expression in MCF cells. For evaluation of BCRP mRNA expression, relative quantitative PCR and comparative C1 method was exploited. BCRP protein expression was measured flow cytometrically with the monoclonal antibody (mAb) BXP-21. Dexamethasone showed a dose-independent and a time-dependent effect on decreasing the mRNA level of BCRP gene in comparison with control in MCF-7 and MCF-7/MX breast cancer cell lines, whereas no changes were noted in the presence of indomethacin. The level of BCRP protein, expressed as a ratio of the corresponding control, was decreased in dexamethasone-treated MCF-7/MX cells. These results could be of great importance when combination therapy protocols with cytotoxic agents and dexamethasone regimens are considered in breast cancer patients.