ABCB1(1199G>A)基因多态性对多西他赛转运影响的分子机制

目的：在体外研究ABCB1（1199G>A）基因多态性对多西他赛转运影响的分子机制。方法：将ABCB1（1199G>A）野生型和突变型基因分别导入HEK293细胞,研究2种重组细胞株对多西他赛的摄取以及跨膜转运的差异。结果：在细胞毒性分析中,ABCB1_1199A/mut细胞对多西他赛表现出更强的耐药性。多西他赛在2种重组细胞中的含量均显著性的低于对照组细胞,证实了多西他赛是由P-糖蛋白介导转运的,并且在ABCB1_1199A/mut细胞中跨膜转运更高。ABCB1_1199A/mut细胞介导转运多西他赛的P-糖蛋白的活性较ABCB1_1199G/wt细胞的更强。结论：ABCB1（1199G>A）基因多态性能够显著性影响P-糖蛋白转运多西他赛的能力,由ABCB1突变型基因编码的P-糖蛋白能够更有效的转运多西他赛。因此ABCB1（1199G>A）基因多态性可能会影响P-糖蛋白的活性,并对药物的分布和消除产生影响,从而影响药物的治疗作用。     

ABCC2 (1249G > A) polymorphism implicates altered transport activity for sorafenib

1.?Multidrug resistance-associated protein 2 (MRP2), encoded by the ABCC2 gene, is an efflux transporter of several endogenous substrates and xenobiotics. Here, we investigated whether the 1249G?>?A (rs2273697) polymorphism in ABCC2 affects the ability of MRP2 to pump the multi-tumor drug sorafenib out of cells.

2.?Human embryonic kidney 293 (HEK 293) cell lines transfected with ABCC2-1249G and ABCC2-1249A were used to assess the sensitivity and accumulation to sorafenib. The isolated MRP2 were applied to estimate the ATPase activity.

3.?The HEK293 cell line overexpressing the ABCC2 1249A allele showed a significantly higher 50% inhibitory concentration (IC₅₀) than a cell line overexpressing ABCC2-1249G or a non-overexpressing control cell line. Intracellular accumulation of sorafenib was much lower in ABCC2-1249A cells than in ABCC2-1249G cells expressing comparable levels of MRP2. Isolated ABCC2-1249A protein showed higher ATPase activity than ABCC2-1249G protein.

4.?Our results suggest that the ABCC2 polymorphism 1249G?>?A increases the ATPase activity of MRP2, leading to greater efflux of sorafenib.     

ABCB1（1199G/A）基因多态性对甲磺酸伊马替尼转运的分子机制

摘 要 目的：探讨P 糖蛋白（P-gp）活性和所介导的甲磺酸伊马替尼胞内累积量及药物跨膜渗透性的影响。 方法: 将构建的ABCB1 1199G/wt和1199A/mut重组质粒分别转染HEK293细胞,利用RT-PCR法考察细胞中P-gp的mRNA表达水平。CCK-8法检测药物对细胞的毒性,高效液相色谱法（HPLC）检测细胞中药物浓度和胞内累积量,跨膜电阻实验考察药物跨膜渗透率,评价P-gp活性对药物转运的作用。结果: 细胞毒性实验表明,转染细胞内的药物浓度均低于对照组,证明P-gp具有介导药物转出胞外的作用。HPLC和跨膜电阻实验表明,与野生型ABCB1(1199G)细胞相比,突变型ABCB1(1199A)细胞抗甲磺酸伊马替尼的作用更强,P-gp对介导甲磺酸伊马替尼外排转运的作用较强且药物的跨膜渗透性也相应较强。结论:实验表明ABCB1（1199G/A）位点突变导致其编码蛋白P-gp活性改变,该位点多态性会导致甲磺酸伊马替尼清除率增加,抑制了药物在靶细胞中有效药物浓度,因此临床上应对ABCB1基因进行分型,指导甲磺酸伊马替尼的个体化用药。     

Structural Determinants of P-Glycoprotein-Mediated Transport of Glucocorticoids

PURPOSE: The aim of this study was to determine requisite structural features for P-glycoprotein-mediated transport of a series of structurally related glucocorticoids (GCs). METHODS: Transport experiments were conducted in wild-type and stably transfected MDRI LLC-PK cell line. Transport efficiency (Teff = Peff, B-->A / Peff, A-->B) in both cell lines was compared as a measure of passive diffusion and P-glycoprotein-mediated transepithelial transport for each steroid. Three-dimensional structure-activity relationships were built to determine how specific structural features within the steroids affect their P-gp-mediated efflux. RESULTS: Mean (+/- SD) Teff in LLC-PK cells was 1.1 +/- 0.17, indicating that differences in structure and partition coefficient did not affect drug flux in the absence of P-glycoprotein. Teff in L-MDRI cells ranged from 3.6 to 26.6, demonstrating the importance of glucocorticoid structure to P-glycoprotein transport. The rank order of Teff in MDR1 cells was: methylprednisolone> prednisolone > betamethasone > dexamethasone/prednisone > cortisol. There was no correlation between individual Teff values and partition coefficient. 3D-QSAR models were built using CoMFA and CoMSIA with a q2 (r2) of 0.48 (0.99) and 0.41 (0.95), respectively. CONCLUSIONS: Nonpolar bulky substituents around the C-6alpha position, as well as a hydrogen-bond donor at position C-11, enhance P-glycoprotein affinity and cellular efflux, whereas bulky substituents at C-16 diminish transporter affinity.     

Effects of MDR1 1236C > T-2677G > T-3435C > T polymorphisms on the intracellular accumulation of tacrolimus,cyclosporine A,sirolimus and everolimus

Abstract

1. Overexpression of P-glycoprotein (P-gp, encoded by MDR1) mediates resistance to multiple immunosuppressors. Several common MDR1 variants (1236C?>?T, 2677G?>?T, 3435C?>?T) impact the efflux activity of P-gp-mediated substrates. We assessed the effect of these polymorphisms on the sensitivity, intracellular accumulation, and efflux of tacrolimus, cyclosporine A, sirolimus and everolimus in transfected LLC-PK1 cells.

2. LLC-PK1 cell lines were transfected with empty vector (pcDNA3.1) and recombinant MDR1_T-T-T, MDR1_C-T-T, MDR1_C-G-T and MDR1_C-G-C vectors, respectively and further screened in the presence of puromycin. The IC₅₀ values, intracellular accumulation, and apparent permeability ratios of tacrolimus, cyclosporine A, sirolimus and everolimus were evaluated.

3. MDR1 overexpression increased the resistance of LLC-PK1 cells to tacrolimus, cyclosporine A, sirolimus and everolimus. The resistance of cells expressing MDR1_C-G-C wild-type haplotypes to tacrolimus were increased compared to MDR1_T-T-T, MDR1_C-T-T, MDR1_C-G-T variant haplotypes. The efflux ability of P-gp-mediated tacrolimus in cells transfected with MDR1_C-G-C was higher than cells overexpressing MDR1_T-T-T, MDR1_C-T-T, MDR1_C-G-T variant haplotypes. In addition, the resistance of cells expressing MDR1_C-G-C wild-type haplotypes to sirolimus were increased compared to MDR1_C-T-T, MDR1_C-G-T variant haplotypes. The efflux ability of P-gp-mediated sirolimus in cells overexpressing MDR1_C-G-C was higher than cells transfected with MDR1_C-T-T, MDR1_C-G-T variant haplotypes.

4. These findings indicate that wild-type MDR1 exports tacrolimus and sirolimus more efficiency than the MDR1_T-T-T, MDR1_C-T-T, MDR1_C-G-T variant protein. This observation indicates that 1236C?>?T, 2677G?>?T, 3435C?>?T variant haplotypes drastically decrease the efflux ability of P-gp-mediated tacrolimus and sirolimus in a substrate-specific manner.     

ABCB1(G1199A)基因稳定转染HEK293细胞株的建立

目的:将ABCB1(G1199A)突变型和野生型基因分别转入HEK293细胞,建立P-糖蛋白稳定表达细胞株。方法:以野生型ABCB1基因的cDNA为模板质粒,采用PCR点突变的方法合成突变的ABCB1(1199A)基因;在慢病毒的介导下,将实验室构建的pLVX-ABCB1-PGK-Puro和pLVX-ABCB1-mut-PGK-Puro重组质粒转染HEK293细胞,经嘌呤霉素筛选稳定表达的细胞;通过流式细胞术检测P-糖蛋白的表达、RT-PCR检测ABCB1基因的转录水平、CCK-8方法测定外源基因对HEK293细胞增殖的影响。结果:流式细胞术证实P-糖蛋白在HEK193细胞中稳定过表达,RT-PCR确定转染细胞中存在ABCB1(G1199A)基因mRNA的过表达,成果获得ABCB1(G1199A)野生型和突变型基因的稳定表达细胞株。结论:成功建立两种ABCB1(G1199A)稳定表达的HEK293细胞株,为该酶的功能研究奠定了基础。     

A novel MDR1 G1199T variant alters drug resistance and efflux transport activity of P-glycoprotein in recombinant Hek cells

The human multidrug resistance gene MDR1 encodes the protein product P-glycoprotein (P-gp). P-gp is an integral membrane protein which mediates ATP-dependent substrate efflux. We recently discovered a novel G --> T variant at 1199 nucleotide position of MDR1 which exhibits a 2.3% allelic frequency in leukemia patients. The functional effects of this MDR1-G1199T variant were evaluated with recombinant HEK cells that stably express the wild-type, G1199A, or G1199T variant of the MDR1 protein, P-gp, at comparable levels. A panel of cytotoxic P-gp substrates comprising doxorubicin, vinblastine, vincristine, paclitaxel, or topotecan (a poor P-gp substrate) was used to evaluate the functional impact of G1199 variations. Compared to MDR1(wt), MDR1(G1199A) exhibited an increased resistance to doxorubicin, paclitaxel, vinblastine, and vincristine. In contrast, MDR1(G1199T) reduced resistance to (1/4) that of MDR1(wt) for all drugs except topotecan. Expression of MDR1 exhibits some degree of resistance to topotecan, but 1199 variation has no impact. These data were consistent with the variation in intracellular doxorubicin concentrations measured in MDR1 recombinant cells. Our results suggest that patients with the novel MDR1-G1199T variant may exhibit a lower degree of MDR1 dependent chemoresistance, and those with the G1199A polymorphism may exhibit a higher degree of resistance, compared with MDR1 wild-type patients.     

The action of adrenal steroids on the pharmacological reactivity of the isolated vein of the rabbit ear

Summary 1. The isolated perfused central vein of the rabbit ear has been used to investigate potentiation by adrenal steroids of the actions of bradykinin, histamine and noradrenaline.2. Potentiation of all substances occurred when adrenal steroids in large doses were added to the perfusate but was neither large in magnitude nor constant in occurrence. Potentiation was seen with cortisol and dexamethasone and their potency was in the same relationship as their glucocorticoid activity. However aldosterone was roughly equi-potent with dexamethasone.3. Thus the potentiation by steroids in this preparation is non-specific in that BK and histamine as well as noradrenaline responses are affected. The potency of steroids does not parallel either glucocorticoid or mineralocorticoid activity and so these results do not suggest an effect of steroids on either specific receptors or membrane electrolyte distribution.Supported in part by Grant G377/206 from National Hearth Foundation of Australia.     

Motesanib (AMG706), a potent multikinase inhibitor,antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1

Cancer cells often become resistant to chemotherapy through a phenomenon known as multidrug resistance (MDR). Several factors are responsible for the development of MDR, preeminent among them being the accelerated drug efflux mediated by overexpression of ATP binding cassette (ABC) transporters. Some small molecule tyrosine kinase inhibitors (TKIs) were recently reported to modulate the activity of ABC transporters. Therefore, the purpose of this study was to determine if motesanib, a multikinase inhibitor, could reverse ABCB1-mediated MDR. The results showed that motesanib significantly sensitized both ABCB1-transfected and drug-selected cell lines overexpressing this transporter to its substrate anticancer drugs. Motesanib significantly increased the accumulation of [³H]-paclitaxel in ABCB1 overexpressing cells by blocking the efflux function of ABCB1 transporter. In contrast, no significant change in the expression levels and localization pattern of ABCB1 was observed when ABCB1 overexpressing cells were exposed to 3 μM motesanib for 72 h. Moreover, motesanib stimulated the ATPase activity of ABCB1 in a concentration-dependent manner, indicating a direct interaction with the transporter. Consistent with these findings, the docking studies indicated favorable binding of motesanib within the transmembrane region of homology modeled human ABCB1. Here, we report for the first time, motesanib, at clinically achievable plasma concentrations, antagonizes MDR by inhibiting the efflux activity of the ABCB1 transporter. These findings may be useful for cancer combination therapy with TKIs in the clinic.     

Differences in the expression of endogenous efflux transporters in MDR1-transfected versus wildtype cell lines affect P-glycoprotein mediated drug transport

Background and purpose:

P-glycoprotein (Pgp) efflux assays are widely used to identify Pgp substrates. The kidney cell lines Madin-Darby canine kidney (MDCK)-II and LLC-PK1, transfected with human MDR1 (ABCB1) are used to provide recombinant models of drug transport. Endogenous transporters in these cells may contribute to the activities of recombinant transporters, so that drug transport in MDR1-transfected cells is often corrected for the transport obtained in parental (wildtype) cells. However, expression of endogenous transporters may vary between transfected and wildtype cells, so that this correction may cause erroneous data. Here, we have measured the expression of endogenous efflux transporters in transfected and wildtype MDCK-II or LLC cells and the consequences for Pgp-mediated drug transport.

Experimental approach:

Using quantitative real-time RT-PCR, we determined the expression of endogenous Mdr1 mRNA and other efflux transporters in wildtype and MDR1-transfected MDCK-II and LLC cells. Transcellular transport was measured with the test substrate vinblastine.

Key results:

In MDR1-transfected MDCK cells, expression of endogenous (canine) Mdr1 and Mrp2 (Abcc2) mRNA was markedly lower than in wildtype cells, whereas MDR1-transfected LLC cells exhibited comparable Mdr1 but strikingly higher Mrp2 mRNA levels than wildtype cells. As a consequence, transport of vinblastine by human Pgp in efflux experiments was markedly underestimated when transport in MDR1-transfected MDCK cells was corrected for transport obtained in wildtype cells. This problem did not occur in LLC cells.

Conclusions and implications:

Differences in the expression of endogenous efflux transporters between transfected and wildtype MDCK cells provide a potential bias for in vitro studies on Pgp-mediated drug transport.     

GW583340 and GW2974, human EGFR and HER-2 inhibitors, reverse ABCG2- and ABCB1-mediated drug resistance

The overexpression of ATP binding cassette (ABC) transporters often leads to the development of multidrug resistance (MDR) and results in a suboptimal response to chemotherapy. Previously, we reported that lapatinib (GW572016), a human epidermal growth factor receptor (EGFR) and HER-2 tyrosine kinase inhibitor (TKI), significantly reverses MDR in cancer cells by blocking the efflux function of ABC subfamily B member 1 (ABCB1) and ABC subfamily G member 2 (ABCG2). In the present study, we conducted in vitro experiments to evaluate if GW583340 and GW2974, structural analogues of lapatinib, could reverse ABCB1- and ABCG2-mediated MDR. Our results showed that GW583340 and GW2974 significantly sensitized ABCB1 and ABCG2 overexpressing MDR cells to their anticancer substrates. GW583340 and GW2974 significantly increased the intracellular accumulation of [(3)H]-paclitaxel in ABCB1 overexpressing cells and [(3)H]-mitoxantrone in ABCG2 overexpressing cells respectively. In addition, GW583340 and GW2974 significantly inhibited ABCG2-mediated transport of methotrexate in ABCG2 overexpressing membrane vesicles. There was no significant change in the expression levels of ABCB1 and ABCG2 in the cell lines exposed to 5μM of either GW583340 or GW2974 for 3 days. In addition, a docking model predicted the binding conformation of GW583340 and GW2974 to be within the transmembrane region of homology modeled human ABCB1 and ABCG2. We conclude that GW583340 and GW2974, at clinically achievable plasma concentrations, reverse ABCB1- and ABCG2-mediated MDR by blocking the drug efflux function of these transporters. These findings may be useful in developing combination therapy for cancer treatment with EGFR TKIs.     

Glucocorticoids regulate the expression of angiotensin AT1 receptors,in the human hepatoma cell line,PLC-PRF-5

The effects of different steroids on the expression of angiotensin AT₁ receptors by the human hepatoma cell line, PLC-PRF-5 was studied. Dexamethasone and aldosterone decreased the specific binding of [³H]angiotensin II to intact PLC-PRF-5 cells by 57 ± 4% and 54 ± 2%, respectively, compared to control, untreated cells. EC₅₀ values for dexamethasone, cortisol and aldosterone were 1.8 ± 0.6, 40 ± 6, and 310 ± 20 nM, respectively, suggesting that these effects were mediated via a glucocorticoid receptor. Scatchard analysis revealed that dexamethasone decreased the number of angiotensin AT₁ receptors expressed (50 ± 4% relative to control) with no change in receptor affinity. Treating cells with dexamethosane in the presence of either an angiotensin converting enzyme inhibitor or an angiotensin II receptor antagonist did not prevent the reduction in angiotensin AT₁ receptor expression, ruling out a mechanism involving a dexamethasone induced increase in endogenous angiotensin II production. A ribonuclease protection assay established that the steady state level of angiotensin AT₁ receptor mRNA in dexamethasone treated cells was reduced to 34.7 ± 8.4% of untreated cells. The decrease in the number of angiotensin AT₁ receptors expressed on the cell surface after treatment with dexamethasone therefore seems likely to reflect the decreased steady state level of the mRNA coding for this receptor.     

Effects of CYP3A5 genotypes,ABCB1 C3435T and G2677T/A polymorphism on pharmacokinetics of Tacrolimus in Chinese adult liver transplant patients

Abstract

1.?The purpose of this study was to establish a population pharmacokinetic (PK) model of tacrolimus and evaluate the influence of clinical covariates, including the genetic polymorphisms of the cytochrome P450 3A5 gene (CYP3A5) and gene-encoding P-glycoprotein (ABCB1), on the PK parameters in Chinese adult liver transplant recipients.

2.?Details of drug dose, sampling times and concentrations were collected retrospectively from routine therapeutic drug monitoring data early after liver transplant. Tacrolimus PKs was studied by a non-linear mixed-effect modeling (NONMEM) method. CYP3A5 genotypes, ABCB1 C3435T and G2677T/A polymorphism and a number of clinical covariates were tested for their influence on TAC PKs.

3.?A one-compartment model with first-order absorption and elimination adequately described the data. Apparent clearance (CL/F) and apparent volumes of distribution (V/F) in final population model were 17.6?L/h and 225?L, respectively. The absorption rate constant (K_a) was fixed at 4.48?h^?1. The inter-individual variability in CL/F and V/F was 53.9 and 68%, respectively. In the final model, CYP3A5 genotype, post-operative day, alanine aminotransferase, total bilirubin, hematocrit and blood urea nitrogen were found to significantly influence the CL/F, whereas POD and HB influence V/F.

4.?Population PK analysis of tacrolimus in Chinese adult liver transplant patients resulted in identification of the CYP3A5 genotype, POD, BUN, ALP, HCT, TBIL and HB as significant covariates on the PK parameters of tacrolimus.     

Association study of ABCB1 and CYP3A5 gene polymorphisms with sirolimus trough concentration and dose requirements in Chinese renal transplant recipients

The objective of this study was to investigate the possible association of the ABCB1 gene C3435 T polymorphism and the CYP3A5 gene A6986G polymorphism with sirolimus (SRL) trough concentration and dose requirements in Chinese stable renal transplant recipients. Blood samples were collected from 105 healthy volunteers and 50 renal transplant patients, whose polymorphisms of the ABCB1 and CYP3A5 genes were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Plasma concentrations of SRL were determined with HPLC. The allele frequencies of the ABCB1 mutation in Chinese healthy volunteers and renal transplant recipients were 51.0% and 44.0% (p>0.05), while the allele frequencies of the CYP3A5 mutation were 72.9% and 71.0% (p>0.05). The SRL concentration/dose ratio (C/D) in patients with CYP3A5 (*)3/(*)3 were significantly higher than that of those with (*)1 allele (p<0.05). However, no significant differences were observed between C/D and ABCB1 SNPs (p>0.05). These results confirm that when treated with a SRL-based therapy and low-dose steroids, patients carrying the CYP3A5(*)1 allele required significantly more SRL to achieve adequate blood trough concentrations. In patients with SRL-based therapy, genotyping of the CYP3A5 genes may help to optimize the SRL management in renal transplant recipients.     

CYP3A5*3 and ABCB1 61A>G Significantly Influence Dose‐adjusted Trough Blood Tacrolimus Concentrations in the First Three Months Post‐Kidney Transplantation

Tacrolimus (TAC) is a first‐line immunosuppressant used to prevent organ rejection after kidney transplantation. There is large inter‐individual variability in its pharmacokinetics. Single nucleotide polymorphisms (SNPs) in genes encoding TAC metabolizing enzymes cytochromes P450 3A4/5 (CYP3A4/5), P‐glycoprotein efflux transporter (ABCB1), their expression regulator pregnane X receptor (NR1I2) and CYP3A co‐factor cytochrome P450 reductase (POR) have been studied for their effects on tacrolimus disposition. However, except for CYP3A5*3, controversies remain about their roles in predicting dose‐adjusted trough blood TAC concentrations (C₀/D). This study aimed to investigate the effects of ABCB1 (61A>G, 1199G>A, 1236C>T, 2677G>T and 3435C>T), CYP3A4*22, CYP3A5*3, NR1I2 (8055C>T, 63396C>T and ‐25385C>T) and POR*28 SNPs on TAC C₀/D. In total, 165 kidney transplant recipients were included in this study. SNPs were genotyped by probe‐based real‐time polymerase chain reaction. Associations between log‐transformed whole blood TAC C₀/D (measured at 1 and 3 months post‐transplant) and genotypes/haplotypes were assessed by linear mixed effects analysis, controlling for age, sex and haematocrit. It was observed that CYP3A5 expressors (*1/*1 + *1/*3) (p = 5.5 × 10⁻¹⁶) and ABCB1 61G allele carriers (p = 0.001) had lower log‐transformed TAC C₀/D (56% and 26% lower geometric mean TAC C₀/D, respectively) and accounted for approximately 30% and 4%, respectively, of log‐transformed TAC C₀/D variability in the first 3 months post‐transplant. In conclusion, CYP3A5*3 is a major, and ABCB1 61A>G is a novel, although minor, genetic factor affecting TAC C₀/D in kidney transplant recipients.     

Associations between the functional polymorphisms in the ABCB1 transporter gene and colorectal cancer risk: a case-control study in Turkish population

Abstract

Colorectal cancer is among the most common cancer types in the world and its etiology involves the interaction of genetic and environmental factors. ABCB1 is highly expressed in the apical surface of colonic epithelial cells and acts as an efflux pump by transporting toxic endogenous substances, drugs and xenobiotics out of cells. ABCB1 polymorphisms may either change its protein expression or alter its function. Several studies have reported a possible association between ABCB1 variants and colorectal cancer, but no consistent conclusion has been arrived at. Therefore, we aimed to investigate the relationship between colorectal cancer and the functional common variants of ABCB1 (1236C?>?T; 2677G?>?T/A; 3435C?>?T). The distributions of the variants were determined in 103 patients with colorectal cancer and 150 healthy volunteers using polymerase chain reaction–restriction fragment length polymorphism methods. ABCB1 1236C?>?T was statistically significantly associated with colorectal cancer risk (OR, odd ratio?=?1.91; 95% CI, confidence interval?=?1.09–3.35; p?=?0.034). In haplotype-based analysis, the proportion of individuals with the ABCB1 haplotype C₁₂₃₆-G₂₆₇₇-T₃₄₃₅ was significantly more common in patients than in controls (OR?=?11.96; 95% CI?=?2.59–55.32; p?=?0.0004). We believe that the findings may be beneficial to the development of efficacious preventive strategies and therapies for colorectal cancer.     

不同性激素对P-糖蛋白表达水平及甲磺酸伊马替尼转运的影响

目的：探讨在ABCB1（1199G/A）重组细胞模型中不同性激素对P-糖蛋白（P-gp）表达水平及甲磺酸伊马替尼转运的影响。方法：将构建的ABCB1_1199G/wt和ABCB1_1199A/mut重组质粒稳定转染入HEK293细胞中,采用RT-PCR和Western Blot分别检测不同性激素对P-gp mRNA和蛋白的表达水平;采用HPLC检测性激素对甲磺酸伊马替尼累积量的影响。结果：浓度梯度的性激素（雌酮、雌三醇雌二酮、黄体酮和睾酮）刺激ABCB1_1199G/wt 和ABCB1_1199A/mut重组细胞后,雌酮和雌三醇能刺激P-gp mRNA和蛋白表达水平,且雌三醇上调ABCB1_1199A/mut mRNA的表达水平显著高于ABCB1_1199G/wt;雌酮和雌三醇可降低甲磺酸伊马替尼在细胞内的累积量,产生对伊马替尼的耐药性。结论：雌酮和雌三醇增加了细胞内P-gp的表达,并促进P-gp介导甲磺酸伊马替尼的转运能力。     

基于ABCB1 （2677T>G）基因多态性指导阿托伐他汀与瑞舒伐他汀个体化用药的临床研究

目的 研究是否采纳基于ABCB1（2677T>G）基因多态性所给出的个体化用药建议对患者调脂疗效的影响。方法 回顾性选取2020年12月-2022年12月河南理工大学第一附属医院住院高脂血症患者85例作为研究对象,患者均经过阿托伐他汀或瑞舒伐他汀连续治疗4周,采用荧光原位杂交法测定ABCB1（2677T>G）基因多态性。按照是否采纳基于ABCB1（2677T>G）基因多态性所给出的个体化用药建议将85例患者分为采纳建议组和未采纳建议组,采纳建议组中TT、GT型患者均服用瑞舒伐他汀,GG型患者均服用阿托伐他汀;未采纳建议组中TT、GT型患者均服用阿托伐他汀,GG型患者均服用瑞舒伐他汀。比较两组患者治疗前后的血脂变化率,观察是否采纳基于ABCB1（2677T>G）基因多态性所给出的个体化用药建议对患者调降脂治疗的影响。结果 85例患者中ABCB1（2677T>G）基因频率分别为GG （25例）29.41%、GT （33例）38.82%、TT （27例）31.77%,ABCB1（2677T>G）基因型分布符合Hardy-Weinberg遗传平衡。治疗前,采纳建议组与未采纳建议组患者的总胆固醇（TC）、低密度脂蛋白-胆固醇（LDL-C）、高密度脂蛋白-胆固醇（HDL-C）没有显著差异。治疗后,两组患者的TC、LDL-C变化率有极显著差异（P<0.001）,而HDL-C变化率差异无统计学意义（P>0.05）。TT型患者治疗后的HDL-C变化率有显著差异（P<0.05）;GT型患者治疗后,TC、HDL-C变化率均有显著差异（P<0.05）,LDL-C变化率差异具有显著统计学意义（P<0.01）;GG型患者治疗后,TC变化率有显著差异（P<0.05）,LDL-C水平变化率的差异具有显著统计学意义（P<0.01）,但HDL-C水平变化率的差异不具有统计学意义（P>0.05）。结论 采纳基于ABCB1（2677T>G）基因多态性所给出的个体化用药建议的患者,其在降低TC、LDL-C水平方面的效果明显优于未采纳建议的患者。     

Nilotinib (AMN107, Tasigna) reverses multidrug resistance by inhibiting the activity of the ABCB1/Pgp and ABCG2/BCRP/MXR transporters

Nilotinib, a BCR-Abl tyrosine kinase inhibitor (TKI), was developed to surmount resistance or intolerance to imatinib in patients with Philadelphia positive chronic myelogenous leukemia. Recently, it was shown that several human multidrug resistance (MDR) ATP-binding cassette (ABC) proteins could be modulated by specific TKIs. MDR can produce cancer chemotherapy failure, typically due to overexpression of ABC transporters, which are involved in the extrusion of therapeutic drugs. Here, we report for the first time that nilotinib potentiates the cytotoxicity of widely used therapeutic substrates of ABCG2, such as mitoxantrone, doxorubicin, and ABCB1 substrates including colchicine, vincristine, and paclitaxel. Nilotinib also significantly enhances the accumulation of paclitaxel in cell lines overexpressing ABCB1. Similarly, nilotinib significantly increases the intracellular accumulation of mitoxantrone in cells transfected with ABCG2. Furthermore, nilotinib produces a concentration-dependent inhibition of the ABCG2-mediated transport of methotrexate (MTX), as well as E₂17βG a physiological substrate of ABCG2. Uptake studies in membrane vesicles overexpressing ABCG2 have indicated that nilotinib inhibits ABCG2 similar to other established TKIs as well as fumitremorgin C. Nilotinib is a potent competitive inhibitor of MTX transport by ABCG2 with a K_i value of 0.69 ± 0.083 μM as demonstrated by kinetic analysis of nilotinib. Overall, our results indicate that nilotinib could reverse ABCB1- and ABCG2-mediated MDR by blocking the efflux function of these transporters. These findings may be used to guide the design of present and future clinical trials with nilotinib, elucidating potential pharmacokinetic interactions. Also, these findings may be useful in clinical practice for cancer combination therapy with nilotinib.