Canine MDR1 gene mutations produce translated P-glycoprotein, an active drug efflux transporter, resulting in dysfunction or over-expression. The 4-base deletion at exon 4 of MDR1 at nucleotide position 230 (nt230[del4]) in exon 4 makes P-glycoprotein lose function, leading to drug accumulation and toxicity. The G allele of the c.-6-180T>G variation in intron 1 of MDR1 (single nucleotide polymorphism [SNP] 180) causes P-glycoprotein over-expression, making epileptic dogs resistant to phenobarbital treatment. Both of these mutations are reported to be common in collies. This study develops a more efficient method to detect these two mutations simultaneously, and clarifies the genotype association with the side effects of chemotherapy. Genotype distribution in Taiwan was also investigated. An oligonucleotide microarray was successfully developed for the detection of both genotypes and was applied to clinical samples. No 4-base deletion mutant allele was detected in dogs in Taiwan. However, the G allele variation of SNP 180 was spread across all dog breeds, not only in collies. The chemotherapy adverse effect percentages of the SNP 180 T/T, T/G, and G/G genotypes were 16.7%, 6.3%, and 0%, respectively. This study describes an efficient way for MDR1 gene mutation detection, clarifying genotype distribution, and the association with chemotherapy.
Alleles ; Animals ; Dogs ; Drug Therapy ; Exons ; Genotype ; Introns ; Methods ; Oligonucleotide Array Sequence Analysis ; P-Glycoprotein ; Phenobarbital ; Taiwan

BACKGROUND: P-glycoprotein (P-gp) transports many chemicals that vary greatly in their structure and function. It is normally expressed in renal proximal tubular cells. We hypothesized that P-gp expression influences light chain excretion. Therefore, we investigated whether renal tubular P-gp expression is altered in patients with plasma cell disorders. METHODS: We evaluated renal biopsy specimens from patients with plasma cell disorders (n = 16) and primary focal segmental glomerulosclerosis (the control group, n = 17). Biopsies were stained with an anti-P-gp antibody. Loss of P-gp expression was determined semi-quantitatively. Groups were compared for loss of P-gp expression, and clinical variables. RESULTS: P-gp expression loss was more severe in patients with plasma cell disorders than it was in those with glomerulonephritis (P = 0.021). In contrast, clinical and histological parameters including serum creatinine, level of urinary protein excretion, and interstitial fibrosis/tubular atrophy grade were not significantly different between the groups. P-gp expression loss increased with age in patients with plasma cell disorders (P = 0.071). This expression loss was not associated with serum creatinine, the level of urinary protein excretion or the interstitial fibrosis/tubular atrophy grade. There was no significant association between the severity of P-gp expression loss with the types and serum levels of light chains, isotypes and serum immunoglobulin levels. CONCLUSION: Renal tubular P-gp expression is significantly down-regulated in patients with plasma cell disorders characterized by nephrotic range proteinuria. Additional studies are needed to determine whether reintroduction of renal tubular P-gp expression would mitigate the proximal tubular injury that is caused by free-light chains.
Amyloidosis ; Atrophy ; Biopsy ; Creatinine ; Glomerulonephritis ; Glomerulosclerosis, Focal Segmental ; Humans ; Immunoglobulin Light Chains ; Immunoglobulins ; P-Glycoprotein ; Plasma Cells ; Plasma ; Proteinuria

PURPOSE: The DNA damage response (DDR) is a multi-complex network of signaling pathways involved in DNA damage repair, cell cycle checkpoints, and apoptosis. In the case of biliary tract cancer (BTC), the strategy of DDR targeting has not been evaluated, even though many patients have DNA repair pathway alterations. The purpose of this study was to test the DDR-targeting strategy in BTC using an ataxia-telangiectasia and Rad3-related (ATR) inhibitor. MATERIALS AND METHODS: A total of nine human BTC cell lines were used for evaluating anti-tumor effect of AZD6738 (ATR inhibitor) alone or combination with cytotoxic chemotherapeutic agents through MTT assay, colony-forming assays, cell cycle analyses, and comet assays. We established SNU478-mouse model for in vivo experiments to confirm our findings. RESULTS: Among nine human BTC cell lines, SNU478 and SNU869 were the most sensitive to AZD6738, and showed low expression of both ataxia-telangiectasia mutated (ATM) and p53. AZD6738 blocked p-Chk1 and p-glycoprotein and increased γH2AX, a marker of DNA damage, in sensitive cells. AZD6738 significantly increased apoptosis, G2/M arrest and p21, and decreased CDC2. Combinations of AZD6738 and cytotoxic chemotherapeutic agents exerted synergistic effects in colony-forming assays, cell cycle analyses, and comet assays. In our mouse models, AZD6738 monotherapy decreased tumor growth and the combination with cisplatin showed more potent effects on growth inhibition, decreased Ki-67, and increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling than monotherapy with each drug. CONCLUSION: In BTC, DDR targeting strategy using ATR inhibitor demonstrated promising antitumor activity alone or in combination with cytotoxic chemotherapeutic agents. This supports further clinical development of DDR targeting strategy in BTC.
Animals ; Apoptosis ; Ataxia Telangiectasia ; Biliary Tract Neoplasms ; Biliary Tract ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Line ; Cisplatin ; Comet Assay ; DNA Damage ; DNA Repair ; DNA ; Humans ; Mice ; P-Glycoprotein

Paclitaxel (PTX) is one of the most frequently used anticancer agent for treating refractory ovarian cancer, metastatic breast cancer and non-small cell lung cancer. However, its oral administration is impeded by very low bioavailability (<5%) due to the P-glycopprotein (P-gp) efflux pump effect. This study investigated in vitro and in vivo P-gp inhibitory effects of adamantyl derivatives AC-603 and AC-786 in rats. Two adamantyl derivatives tested in this study increased the cytotoxicity of daunomycin (DNM) in P-gp overexpressed cell line by inhibiting P-gp efflux function. Pharmacokinetics of PTX with orally co-administered P-gp inhibitors were assessed in rats to improve PTX absorption. The pharmacokinetic parameters of PTX were determined in rats after intravenous (2 mg/kg) or oral (25 mg/kg) administration in the presence or absence of verapamil (a positive control), AC-603 or AC-786 (0.5 mg/kg or 5 mg/kg). Compared to control group (PTX alone), experimental groups (PTX with AC-603 or AC-786) significantly increased the area under the plasma concentration-time curve of PTX following oral administration by 1.7–2.2 fold. The volume of distribution and total clearance of PTX were decreased, while other parameters were not significantly changed. In conclusion, co-administration of AC-603 or AC-786 enhanced the relative bioavailability of orally administered PTX as compared to control.
Absorption ; Administration, Oral ; Animals ; Biological Availability ; Breast Neoplasms ; Carcinoma, Non-Small-Cell Lung ; Cell Line ; Daunorubicin ; In Vitro Techniques ; Ovarian Neoplasms ; P-Glycoprotein ; Paclitaxel* ; Pharmacokinetics ; Plasma ; Rats* ; Verapamil

Oseltamivir is a substrate of P-glycoprotein, an efflux drug transporter encoded by ABCB1. The objective of this study was to assess the role of ABCB1 (c.1236C>T, c.2677G>T/A, and c.3435C>T) polymorphisms in the pharmacokinetics of oseltamivir and its active metabolite, oseltamivir carboxylate in humans. Nineteen healthy male subjects were enrolled, and their ABCB1 polymorphisms were evaluated. After the oral administration of 75 mg oseltamivir, the plasma concentrations of oseltamivir and oseltamivir carboxylate were measured. Pharmacokinetic analysis was carried out. Systemic exposure to oseltamivir and oseltamivir carboxylate was higher in the mutant group than in the wild-type and heterozygous groups. We suggest that ABCB1 polymorphisms affect the pharmacokinetics of oseltamivir in humans. Further studies in a large population are necessary to validate the results of this preliminary study (Clinical Trial Registration Information [CRIS] registry: http://cris.nih.go.kr, No. KCT0001903).
Administration, Oral ; Humans* ; Male ; Oseltamivir* ; P-Glycoprotein ; Pharmacokinetics* ; Plasma

OBJECTIVES: Banha-sasim-tang (BST), which consists of seven different herbs, is one of the most popular herbal formulae for treating gastrointestinal disorders in Eastern Asia. The commonly used herbal medicine is often co-administered with other therapeutic drugs, which raises the possibility of herb–drug interactions and may modify the clinical safety profile of therapeutic drugs. METHODS: We investigated the potential herb–drug interactions between BST extract and midazolam (MDZ) in mice. The area under the plasma concentration-time curve (AUC) of MDZ and 1ʹ-hydroxymidazolam (1ʹ-OH-MDZ) was evaluated for both oral and intraperitoneal administration of MDZ, following oral administration of BST (0.5 and 1 g/kg). RESULTS: It was found that the AUC of MDZ and 1ʹ-OH-MDZ was lower in case of oral administration of MDZ. Administration of BST extract was not associated with hepatic cytochrome P450 activity. BST extract induced a strong reduction in pH and it has been reported that oral mucosal absorption of MDZ is lower at low pH. The decreased absorption rate of MDZ might be caused by the ingredients of BST and may not be related to other factors such as increased excretion of MDZ by P-glycoprotein. CONCLUSIONS: The altered pharmacokinetics of midazolam caused by co-administration with BST in vivo could be attributed to a decrease in pH and subsequent reduction of MDZ absorption rate.
Absorption* ; Administration, Oral ; Animals ; Area Under Curve ; Cytochrome P-450 Enzyme System ; Far East ; Herb-Drug Interactions ; Herbal Medicine ; Hydrogen-Ion Concentration* ; Mice ; Midazolam* ; Oral Mucosal Absorption ; P-Glycoprotein ; Pharmacokinetics ; Plasma ; Stomach*

Cancer stem cells (CSCs) are a subset of tumor cells, which are characterized by resistance against chemotherapy and environmental stress, and are known to cause tumor relapse after therapy. A number of molecular mechanisms underlie the chemoresistance of CSCs, including high expression levels of drug efflux transporters. We investigated the role of the antioxidant transcription factor NF-E2-related factor 2 (NRF2) in chemoresistance development, using a CSC-enriched colonosphere system. HCT116 colonospheres were more resistant to doxorubicin-induced cell death and expressed higher levels of drug efflux transporters such as P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) compared to HCT116 monolayers. Notably, levels of NRF2 and expression of its target genes were substantially elevated in colonospheres, and these increases were linked to doxorubicin resistance. When NRF2 expression was silenced in colonospheres, Pgp and BCRP expression was downregulated, and doxorubicin resistance was diminished. Collectively, these results indicate that NRF2 activation contributes to chemoresistance acquisition in CSC-enriched colonospheres through the upregulation of drug efflux transporters.
Breast Neoplasms ; Cell Death ; Doxorubicin* ; Drug Therapy ; Neoplastic Stem Cells ; NF-E2-Related Factor 2 ; P-Glycoprotein ; Recurrence ; Transcription Factors ; Up-Regulation

PURPOSE: Traditional chemotherapy is the main adjuvant therapy for the treatment of non-small cell lung cancer (NSCLC). However, the emergence of multi-drug resistance (MDR) has greatly restricted the curative effect of chemotherapy. Therefore, it is necessary to find a method to treat MDR NSCLC clinically. It is worth investigating whether NSCLCs that are resistant to traditional chemotherapy can be effectively treated with tyrosine kinase inhibitors targeting epidermal growth factor receptor (EGFR). MATERIALS AND METHODS: The expression of P-glycoprotein (P-gp) and lung resistance-related protein (LRP) was detected by immunohistochemistry, and mutations in EGFR (exons 19 and 21) and Kirsten rat sarcoma viral oncogene homolog (KRAS) (exon 2) were detected by high-resolution melting analysis (HRMA) of surgical NSCLC specimens from 127 patients who did not undergo traditional chemotherapy or radiotherapy. A Pearson chi-square test was performed to analyze the correlations between the expression of P-gp and LRP and mutations in EGFR and KRAS. RESULTS: The expression frequencies of P-gp and LRP were significantly higher in adenocarcinomas from non-smoking patients; the expression frequency of LRP was significantly higher in cancer tissue from female patients. The frequency of EGFR mutations was significantly higher in well to moderately differentiated adenocarcinomas from non-smoking female patients. The frequency of EGFR mutations in the cancers that expressed P-gp, LRP, or both P-gp and LRP was significantly higher than that in cancers that did not express P-gp or LRP. CONCLUSION: NSCLCs expressing P-gp/LRP bear the EGFR mutation in exon 19 or 21 easily.
Aged ; Aged, 80 and over ; Carcinoma, Non-Small-Cell Lung/*genetics/surgery ; Exons/*genetics ; Female ; Humans ; Lung Neoplasms/*genetics/pathology/surgery ; Middle Aged ; Mutation ; P-Glycoprotein/*genetics ; Protein Kinase Inhibitors/therapeutic use ; Proto-Oncogene Proteins/*genetics ; Proto-Oncogene Proteins p21(ras) ; Receptor, Epidermal Growth Factor/*genetics ; Treatment Outcome ; Vault Ribonucleoprotein Particles/*genetics ; ras Proteins/*genetics

This study aimed to investigate the in vivo relevance of P-glycoprotein (P-gp) in the pharmacokinetics and adverse effect of phenformin. To investigate the involvement of P-gp in the transport of phenformin, a bi-directional transport of phenformin was carried out in LLC-PK1 cells overexpressing P-gp, LLC-PK1-Pgp. Basal to apical transport of phenformin was 3.9-fold greater than apical to basal transport and became saturated with increasing phenformin concentration (2-75 µM) in LLC-PK1-Pgp, suggesting the involvement of P-gp in phenformin transport. Intrinsic clearance mediated by P-gp was 1.9 µL/min while passive diffusion clearance was 0.31 µL/min. Thus, P-gp contributed more to phenformin transport than passive diffusion. To investigate the contribution of P-gp on the pharmacokinetics and adverse effect of phenformin, the effects of verapamil, a P-gp inhibitor, on the pharmacokinetics of phenformin were also examined in rats. The plasma concentrations of phenformin were increased following oral administration of phenformin and intravenous verapamil infusion compared with those administerd phenformin alone. Pharmacokinetic parameters such as Cmax and AUC of phenformin increased and CL/F and Vss/F decreased as a consequence of verapamil treatment. These results suggested that P-gp blockade by verapamil may decrease the phenformin disposition and increase plasma phenformin concentrations. P-gp inhibition by verapamil treatment also increased plasma lactate concentration, which is a crucial adverse event of phenformin. In conclusion, P-gp may play an important role in phenformin transport process and, therefore, contribute to the modulation of pharmacokinetics of phenformin and onset of plasma lactate level.
Administration, Oral ; Animals ; Area Under Curve ; Diffusion ; Intestinal Absorption ; Lactic Acid* ; LLC-PK1 Cells ; P-Glycoprotein* ; Pharmacokinetics ; Phenformin* ; Plasma* ; Rats ; Swine ; Verapamil

The fields of pharmacogenetics and pharmacogenomics have become increasingly promising regarding the clinical application of genetic data to aid in prevention of adverse reactions. Specific screening tests can predict which animals express modified proteins or genetic sequences responsible for adverse effects associated with a drug. Among the genetic variations that have been investigated in dogs, the multidrug resistance gene (MDR) is the best studied. However, other genes such as CYP1A2 and CYP2B11 control the protein syntheses involved in the metabolism of many drugs. In the present study, the MDR-1, CYP1A2 and CYP2B11 genes were examined to identify SNP polymorphisms associated with these genes in the following four canine breeds: Uruguayan Cimarron, Border Collie, Labrador Retriever and German Shepherd. The results revealed that several SNPs of the CYP1A2 and CYP2B11 genes are potential targets for drug sensitivity investigations.
Animals ; Aryl Hydrocarbon Hydroxylases/*genetics/metabolism ; Cytochrome P-450 CYP1A2/*genetics/metabolism ; Dogs/*genetics/metabolism ; P-Glycoprotein/*genetics/metabolism ; *Polymorphism, Single Nucleotide ; Steroid Hydroxylases/*genetics/metabolism