Discovery and characterization of OC144-093, a novel inhibitor of P-glycoprotein-mediated multidrug resistance

OC144-093 is a novel substituted diarylimidazole (Mr 495) generated using the OntoBLOCK system, a solid-phase combinatorial chemistry technology, in combination with high-throughput cell-based screening. OC144-093 reversed multidrug resistance (MDR) to doxorubicin, paclitaxel, and vinblastine in human lymphoma, breast, ovarian, uterine, and colorectal carcinoma cell lines expressing P-glycoprotein (P-gp) with an average EC50 of 0.032 microM. Inhibition of MDR by OC144-093 was reversible, but the effect persisted for at least 12 h after removal of compound from the culture medium. OC144-093 had no effect on the response to cytotoxic agents by cells in vitro lacking P-gp expression or expressing a multidrug resistance-associated protein (MRP-1). OC144-093 was not cytotoxic by itself against 15 normal, nontransformed, or tumor cell lines, regardless of P-gp status, with an average cytostatic IC50 of >60 microM. OC144-093 blocked the binding of [3H]azidopine to P-gp and inhibited P-gp ATPase activity. The compound was >50% p.o. bioavailable in rodents and dogs and did not alter the plasma pharmacokinetics of i.v.-administered paclitaxel. OC144-093 increased the life span of doxorubicin-treated mice engrafted with MDR P388 leukemia cells by >100% and significantly enhanced the in vivo antitumor activity of paclitaxel in MDR human breast and colon carcinoma xenograft models, without a significant increase in doxorubicin or paclitaxel toxicity. The results demonstrate that OC144-093 is an orally active, potent, and nontoxic inhibitor of P-gp-mediated multidrug resistance that exhibits all of the desired properties for treatment of P-gp-mediated MDR, as well as for prevention of MDR prior to selection and/or induction of refractory disease.     

Effect of ifosfamide on intracellular glutathione levels in peripheral blood lymphocytes and its correlation with therapeutic response in patients with advanced ovarian cancer

 The successful outcome of ovarian cancer therapy with alkylating agents and cisplatin is seriously hampered by the development of acquired drug resistance. An increase in intracellular glutathione (GSH) levels in cancer cells is one of the major mechanisms involved. Depletion of GSH overcomes drug resistance and restores the chemosensitivity of malignant cells. Ifosfamide (IFEX), an alkylating agent, has been demonstrated to decrease intracellular GSH levels in vitro in malignant cell lines and in vivo in peripheral blood lymphocytes (PBL) obtained from patients with cancer. We studied the effect of IFEX on intracellular GSH levels in PBL isolated from patients with advanced ovarian cancer who were receiving chemotherapy. A total of 14 patients received IFEX plus mesna as a continuous infusion (1 g/m² per day) for 6 consecutive days and cisplatin (100 mg/m²) as a 24-h continuous infusion on the 6th day. PBL were isolated prior to the initiation of chemotherapy and on the 3rd and 6th days of IFEX infusion. Intracellular GSH levels were determined by a modification of Tietze’s method. IFEX caused a 20% or greater suppression of intracellular GSH levels in nine patients, eight of whom achieved complete remission of their disease. Six patients responded poorly to this chemotherapeutic regimen, five of whom showed no significant suppression of GSH levels. These data suggest that IFEX suppresses intracellular GSH levels in PBL from patients with ovarian cancer and that this suppression correlates closely with the subsequent clinical outcome. Received: 16 March 1996 / Accepted: 25 July 1996     

Determination of vinca alkaloids in human plasma by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

 A sensitive assay was developed for the quantitation of vinblastine, desacetylvinblastine and vincristine using liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). Analyses were performed on an Ultrasphere C₁₈ microbore column using ammonium acetate as mobile phase. The calibration curves were linear across the range of 0.51–4.00 ng/ml (0.63–4.93 nM) for vinblastine, 0.74–3.93 ng/ml (0.96–5.11 nM) for desacetylvinblastine and 0.30–3.95 ng/ml (0.36–4.79 nM) for vincristine. Vinca alkaloid concentrations were measured with an accuracy and precision within 11%. This assay could be implemented to determine the plasma concentrations for pharmacokinetic studies of vinblastine, desacetylvinblastine and vincristine in conjunction with clinical trials. Received: 15 December 1995 / Accepted: 16 June 1996     

Plasma concentrations of polysorbate 80 measured in patients following administration of docetaxel or etoposide

 Docetaxel (Taxotere, Rhone-Poulenc Rorer) and etoposide are water-insoluble drugs formulated with polysorbate 80 for intravenous administration. We have previously reported that surfactants, including polysorbate 80 and Cremophor EL, can reverse the multidrug resistance (MDR) phenotype in an experimental system and that plasma Cremophor EL concentrations measured following a 3-h infusion of paclitaxel were ≥1 μl/ml, sufficient to modulate MDR in vitro. The purpose of this study was to measure polysorbate 80 plasma concentrations in patients following intravenous administration of etoposide or docetaxel using a bioassay in which MDR-expressing cells are incubated with daunorubicin (DNR) plus 50/50 growth medium/plasma and equilibrium intracellular DNR fluorescence is measured by flow cytometry. In vitro experiments show maximal reversal of MDR at concentrations of 1.0–2.0 μl/ml and 50% reversal at 0.2–0.3 μl/ml. Patients received docetaxel at 75 mg/m² (five patients) or 100 mg/m² (four patients) (total dose 125–178 mg, containing 3.12–4.45 ml polysorbate 80) over 60 min. The median end-infusion polysorbate 80 concentration was 0.1 μl/ml (range 0.07–0.41 μl/ml). Only one patient had a level of >0.2 μl/ml. Five patients received intravenous etoposide at 120 mg/m² over 45–120 min (total dose 180–250 mg, containing 0.67–0.93 ml polysorbate 80). In the end-infusion plasma sample, polysorbate 80 was not detectable (<0.06 μl/ml) in any patient. Plasma polysorbate 80 levels following an intravenous infusion of 120 mg/m² etoposide or of docetaxel at doses used in Phase II trials, are insufficient to show modulation of MDR in vitro. Received: 21 July 1996 / Accepted: 4 November 1996     

Fulvestrant,a selective estrogen receptor down-regulator,sensitizes estrogen receptor negative breast tumors to chemotherapy

Drug resistance frequently results in poor prognosis and high 5-year recurrence rate in estrogen receptor-negative (ER−) breast cancer patients. Herein, we examined the reversal effects of fulvestrant on multidrug resistance (MDR) in ER− breast cancer cells. Co-administration of fulvestrant significantly sensitized ER− MDR tumors to paclitaxel both in vitro and in vivo. Further analyses indicated that fulvestrant did not affect P-gp expression, but could inhibit P-gp function and subsequently reverse P-gp mediated drug resistance in ER− breast cancer cells. These results showed that combination of fulvestrant and chemotherapeutic agents might provide an effective treatment for ER− MDR breast cancers.     

联合检测MDR1/P-gp、C-erbB-2在乳腺癌中的表达及临床意义

目的 :联合检测乳腺癌患者中MDR1/P gp、及C erbB 2的表达 ,并探讨MDR1/P gp与C erbB 2的相关性。方法 :采用荧光定量RT PCR(FQ RT PCR)法检测 5 7例乳腺癌、2 0例对照组 (包括 10例乳腺良性疾病、10例癌旁正常组织 )中MDR1基因的表达 ,同时采用免疫组化法检测上述标本中P gp及C erbB 2蛋白的表达。 结果 :乳腺癌患者中MDR1基因扩增率及P gp蛋白阳性率分别为 5 0 .88% (2 9/ 5 7)和 4 2 .11% (2 4 / 5 7) ,与正常对照组相比均具有显著性差异 (P <0 .0 1)。MDR1基因扩增率高于P gp蛋白表达 ,二者呈高度相关 ,但并不完全相符 ;乳腺癌中C erbB 2过表达率为 2 8.0 7% (16 / 5 7) ,正常对照组中无C erbB 2蛋白过表达。MDR1/P gp阳性率与C erbB 2过表达呈正相关。结论 :乳腺癌中存在多药耐药基因MDR1及原癌基因C erbB 2的共表达 ,且其表达呈正相关。上述二种基因的表达 ,与乳腺癌的多药耐药有关。     

Augmentation of vincristine cytotoxicity by megestrol acetate

 Purpose: To determine the effect of a semisynthetic progesterone, megestrol acetate (MA), on the cytotoxicity of various chemotherapeutic agents including vincristine, doxorubicin, actinomycin-D, taxol, vinblastine and colchicine in cell lines with or without P-gp expression. Methods: Three cell lines with high P-gp expression (two colon cancer and one leukemia), and a control cell line with no P-gp expression were exposed to chemotherapeutic agents in the presence or absence of MA and drug sensitivity was determined using the MTT colorimetric assay. P-gp-170 expression was detected by flow cytometry using JSB-1 monoclonal antibody and the functionality of MDR expression was tested by rhodamine-123 uptake studies. In vitro drug accumulation studies were performed using [³H]-vincristine. The results were subjected to paired t-test analysis and 95% confidence intervals were determined in cytotoxicity tests. Results: MA augmented the cytotoxicity of vincristine, but not doxorubicin, actinomycin-D, taxol, vinblastine or colchicine in the three P-gp-expressing cell lines, whereas verapamil augmented the cytotoxicity of doxorubicin and vincristine. MA did not augment the cytotoxicity of vincristine in the P-gp-negative HUT-102 cell line. Conclusion: MA augmented vincristine cytotoxicity in P-gp-expressing cell lines. However, this phenomenon did not occur with the other classic MDR drugs. Therefore, the augmentation of vincristine cytotoxicity by MA can be explained either by involvement of a different mechanism that coexists with the mdr-1 phenotype or by the presence of a different affinity or binding site on the P-gp molecule for MA compared to that for the other classic MDR drugs and verapamil. Received: 8 September 1995 / Accepted: 3 June 1996     

Drug resistance in chemotherapy for breast cancer

Recent developments with chemotherapy for breast cancer have improved patient survival. However, there continue to be nonresponders to conventional anticancer agents. Multidrug resistance (MDR) is caused by the expression of P-glycoprotein (P-gp) on the cell membrane. The expression of P-gp is encoded by MDR1 mRNA in tumors and is associated with clinical drug resistance. Since P-gp appears to be involved in both acquired and congenital MDR in human cancers, P-gp could be an important target for improving the efficacy of chemotherapy. Recently, we have focused on a therapeutic approach to reduce drug resistance in chemotherapy for breast cancer. Dofequidar fumarate (Dof) is a novel, orally active quinoline derivative that reverses multidrug resistance. In preclinical studies, the inhibition of doxorubicin-resistant cancer cell lines was observed in the presence of Dof + doxorubicin. We conducted clinical trials including Dof + cyclophosphamide (C), doxorubicin (A), and fluorouracil therapy (F) for patients with advanced or recurrent breast cancer. We compared the efficacy and tolerability of Dof + CAF with CAF alone. In this randomized, placebo-controlled trial, all patients were treated with six cycles of CAF therapy. Patients received Dof (900 mg p.o.) 30 min before doxorubicin. The primary endpoint was overall response rate (partial or complete response). In total, 221 patients were evaluable. The overall response rate was 42.6% for CAF alone versus 53.1% for Dof + CAF. Although the response rate improved by more than 10% with the combination of Dof + CAF, it was not statistically significant. Initially, we were expecting more than 20% improvement in the overall response rate. However, Dof significantly improved progression-free survival in patients who were premenopausal (P=0.046), who had received no prior therapy (P<0.01), or patients with advanced (stage IV) primary tumors (P=0.017). In addition, treatment with Dof did not affect the plasma concentration of doxorubicin in patients. These clinical studies indicate that Dof was well tolerated and displayed promising efficacy in patients who had not received prior therapy. The antiestrogens, tamoxifen, and toremifene, may moderate P-gp-related drug resistance in vitro. Toremifene demonstrated a synergistic effect in combination with paclitaxel on various human breast cancer cell lines. Furthermore, a synergistic effect was observed on a multidrug-resistant cell line. This synergistic effect was more potent when paclitaxel was combined with toremifene than with tamoxifen. Clinical benefits in some patients with recurrent breast cancer were reported.     

A phase I and pharmacokinetic study of oral uracil,ftorafur, and leucovorin in patients with advanced cancer

 A phase I and pharmacokinetic study of oral uracil, ftorafur, and leucovorin was performed in patients with advanced cancer. Uracil plus ftorafur (UFT) was given in a 4:1 molar ratio in three divided doses for 28 consecutive days. Patient cohorts were treated at 200, 250, 300, and 350 mg/m² of UFT daily. For all patients, 150 mg of leucovorin was given daily in three oral doses. A 1-week rest period followed each 28-day treatment course. Gastrointestinal toxicity, characterized by diarrhea, nausea, and vomiting, was dose-limiting at 350 mg/m² UFT in patients who had received prior chemotherapy. Mild fatigue and transient hyperbilirubinemia were also common. In previously untreated patients, UFT at 350 mg/m² was well-tolerated, suggesting this as an acceptable phase II dose in this schedule with leucovorin. Two of eight previously untreated patients with advanced colorectal cancer had partial responses with UFT (350 mg/m²) plus leucovorin. Pharmacokinetic parameters [ftorafur, uracil, 5-fluorouracil (5-FU), 5-methyltetrahydrofolate] showed wide interpatient variations. Plasma levels of 5-FU (C_max 1.4±1.9 μM) were comparable to those achieved with protracted venous infusions, and folate levels (C_max 6.1±3.6 μM) were sufficient for biochemical modulation. Ongoing study will determine if this convenient oral regimen will compare favorably in terms of efficacy, toxicity, and cost with intravenous fluoropyrimidine programs. Received: 20 January 1995/Accepted: 29 June 1995     

A phase I/II study of high-dose cyclophosphamide,cisplatin, and thioTEPA followed by autologous bone marrow and granulocyte colony-stimulating factor-primed peripheral-blood progenitor cells in patients with advanced malignancies

 The purpose of the present study was to determine the maximally tolerated dose of thioTEPA given with fixed high-dose cyclophosphamide (CPA) and cisplatin (cDDP) followed by autologous bone marrow (ABM) with or without granulocyte colonystimulating factor (G-CSF)-primed peripheral-blood progenitor cells (PBPCs) in patients with advanced malignancies. Patients were required to have histologically documented malignancies and adequate renal, hepatic, pulmonary, and cardiac function. CPA was given at 1,875 mg/m² per day as a 1-h i.v. infusion for 3 consecutive days, and cDDP was given at 55 mg/m² per day as a 24-h continuous i.v. infusion over 3 days concurrently with CPA. ThioTEPA was given once as a 1-h i.v. infusion (300–900 mg/m²) either following (the first 13 patients) or prior to CPA and cDDP. In all, 31 patients received PBPCs. A total of 46 patients were treated. There were 6 deaths among the 15 patients who did not receive PBPCs (13 received thioTEPA following CPA and cDDP). Among the other 31 patients who received PBPCs (all of whom also received thioTEPA prior to CPA and cDDP), there were 4 deaths, all involving patients with refractory ovarian carcinoma. The main toxicities were mucositis, esophagitis, hepatotoxicity, and nephrotoxicity. The median time required to achieve an absolute neutrophil count of 500 μl was 10 days (range, 9–12 days) for those who received PBPCs and 15 days (range, 15–34 days) for those who did not receive PBPCs. Altogether, 47% of the major organ toxicities (grades 3 and 4 renal, hepatic, and cardiac toxicities) occurred among the 15 patients who did not receive PBPCs, although these patients received thioTEPA at the lowest 2 dose levels. There were 3 complete responses and 22 partial responses among 35 evaluable patients (overall response rate, 71%), with the median duration of response being 3.5 months (range, 2–17 months). The maximally tolerated dose of thioTEPA was 600 mg/m² given as a 1-h i.v. infusion on the day prior to CPA and cDDP administration. The combination of high-dose CPA, cDDP, and thioTEPA is a well-tolerated regimen when thioTEPA is given prior to CPA and cDDP and when the combination also includes PBPCs in addition to ABM. This regimen is active in a variety of malignancies. Received: 15 February 1995/Accepted: 22 May 1995     

Mitoxantrone, etoposide, and cytarabine plus cyclosporine for patients with relapsed or refractory acute myeloid leukemia: an Eastern Cooperative Oncology Group pilot study

BACKGROUND: One potential mechanism of drug resistance to chemotherapy is the overexpression of multidrug resistance (MDR) genes coding for P-glycoprotein (P-gp), which leads to reduced intracellular retention of chemotherapy. This study tested the efficacy and toxicity of mitoxantrone, etoposide, and intermediate dose cytarabine (MEC) with cyclosporine (CSP) as an MDR modulator in patients with recurrent and refractory acute myeloid leukemia, and also correlated P-gp expression in leukemia cells with response. METHODS: Thirty-eight eligible patients who were in first recurrence after < 6 months of complete remission (CR) (11 patients), refractory to initial induction therapy or to one attempt at reinduction after recurrence (18 patients), in second recurrence (4 patients), or in recurrence after either allogeneic or autologous bone marrow transplantation (5 patients) received either MEC alone (13 patients) or MEC-CSP (25 patients). CSP was given as a loading dose of 6 mg/kg for 2 hours intravenously (i.v.) starting 2 hours before the first dose of etoposide, followed by a continuous i.v. infusion of 18 mg/kg/day for 98 hours. RESULTS: Three of the 13 patients (23%) who received MEC achieved CR, as did 6 of the 25 patients (24%) who received MEC-CSP. The median remission duration for all patients who achieved CR was 149 days (range, 26-466 days), 91 days (range, 81-172 days) for the 3 patients who received MEC, and 189.5 days (range, 26-466 days) for the patients treated with MEC-CSP. The median survival for the patients treated with MEC and MEC-CSP was 104 and 72 days, respectively. CONCLUSIONS: No significant association was found between P-gp expression and response. No apparent benefit in the CR rate, remission duration, or survival was observed with the addition of CSP to MEC.     

TAM对非小细胞肺癌经NVB-DDP方案诱导耐药性逆转的临床观察

目的:以大剂量三苯氧胺(Tamoxifen,TAM)逆转非小细胞肺癌经多次长春瑞滨-顺铂方案治疗后所产生的多药耐药性,提高疗效。方法:研究前均以流式细胞技术检测患者外周血淋巴细胞(PBL)中P-gp的表达。将72例对长春瑞滨-顺铂方案治疗产生耐药性的非小细胞肺癌患者随机分成两组,每组36例。A组为三苯氧胺治疗组,B组为对照组。A组患者在本次研究中每次化疗前3天及化疗第1、2天口服TAM100mg,每日2次,化疗方案为长春瑞滨25mg/m2,iv,d1,8;顺铂40mg/m2ivd1～3,每28天重复,不少于2周期。B组不服用TAM,仅进行化疗,方案同A组。每周期结束后均检测P-gp的表达并评价临床疗效。结果:两组患者在本研究前PBL中P-gp均呈阳性,A组的总有效率为33.3%(12/36),并有47.2%(17/36)P-gp转阴或显著降低;B组总有效率为13.9%(5/36),P-gp无转阴或显著下降者。经统计学处理,两组临床有效率P<0.01,P-gp转阴率P<0.01,其差异均具有显著性。结论:大剂量TAM对经多次长春瑞滨-顺铂方案治疗后产生了耐药性的患者有较好的逆转作用,可使疗效再次提高。     

Plasma alcohol concentrations in patients following paclitaxel infusion

 Paclitaxel is formulated in 50% Cremophor EL and 50% ethanol such that patients receiving paclitaxel also receive a significant amount of each of these solvents. The aim of this study was to measure the plasma alcohol levels in patients treated with paclitaxel. A total of 12 patients who were enrolled in phase II trials of non-small-cell lung cancer, breast cancer or ovarian cancer received 175 mg/m² paclitaxel given as a 3-h infusion. Blood samples were obtained prior to and immediately following the infusion, and plasma ethanol concentrations were measured enzymatically. The dose of ethanol delivered with the paclitaxel ranged from 20.0 to 28.9 ml. No alcohol was detected in pre-dose plasma, but 8 of 12 patients had detectable levels in post-infusion plasma, with 0.033 g/dl being the highest concentration. The elimination rate of alcohol approximates the infusion rate when paclitaxel is given over 3 h, resulting in low or undetectable levels in most patients. However, in patients receiving an equivalent dose of paclitaxel given as a 1-h infusion, the plasma alcohol levels will likely be high enough for significant pharmacological effects to occur. Received 14 May 1995/Accepted: 4 August 1995     

Sipholenol A, a marine-derived sipholane triterpene, potently reverses P-glycoprotein (ABCB1)-mediated multidrug resistance in cancer cells

Through extensive screening of marine sponge compounds, the authors have found that sipholenol A, a sipholane triterpene isolated from the Red Sea sponge, Callyspongia siphonella, potently reversed multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp). In experiments, sipholenol A potentiated the cytotoxicity of several P-gp substrate anticancer drugs, including colchicine, vinblastine, and paclitaxel, but not the non-P-gp substrate cisplatin, and significantly reversed the MDR of cancer cells KB-C2 and KB-V1 in a concentration-dependent manner. Furthermore, sipholenol A had no effect on the response to cytotoxic agents in cells lacking P-gp expression or expressing MDR protein 1 or breast cancer resistance protein. Sipholenol A (IC(50) > 50 microM) is not toxic to all the cell lines that were used, regardless of their membrane transporter status. Accumulation and efflux studies with the P-gp substrate [(3)H]-paclitaxel demonstrated that sipholenol A time-dependently increased the intracellular accumulation of [(3)H]-paclitaxel by directly inhibiting P-gp-mediated drug efflux. In addition, sipholenol A did not alter the expression of P-gp after treating KB-C2 and KB-V1 cells for 36 h and 72 h. However, it efficaciously stimulated the activity of ATPase of P-gp and inhibited the photolabeling of this transporter with its transport substrate [(125)I]-iodoarylazidoprazosin. Overall, the present results indicate that sipholenol A efficiently inhibits the function of P-gp through direct interactions, and sipholane triterpenes are a new class of potential reversing agents for treatment of MDR in P-gp-overexpressing tumors.     

Inhibition of etoposide elimination in the isolated perfused rat liver by Cremophor EL and Tween 80

 Cremophor EL, a surfactant used in the clinical formulation of cyclosporine and paclitaxel, will reverse the multidrug resistance (MDR) phenotype in vitro. As other MDR modulators can alter the pharmacokinetics of cytotoxic drugs, the aim of this study was to examine the effect of Cremophor and another MDR-reversing surfactant, Tween 80, on the hepatic elimination and biliary excretion of etoposide. Using the isolated perfused rat-liver model with 80 ml recirculating perfusate containing 20% red blood cells and 4% bovine serum albumin, etoposide (1.6 mg) with and without Cremophor (800 or 80 mg) or Tween 80 (80 mg) was given into the perfusate reservoir, and perfusate and bile samples were collected for 3 h. Etoposide was measured by high-performance liquid chromatography (HPLC) and Cremophor was measured using a bioassay. Both surfactants changed the etoposide elimination profile from biphasic to monophasic. High-dose Cremophor increased the AUC (from 334±23 to 1540±490 μg min ml^-1, P<0.05) and decreased the total clearance (from 4.8±0.3 to 1.1±0.3 ml/min, P<0.05) and biliary clearance (from 2.6±1.1 to 0.5±0.2 ml/min, P<0.05) but decreased the elimination half-life (from 62±17 to 40±5 min, P<0.05) and volume of distribution (from 424±85 to 65±19 ml, P<0.05). Low-dose Cremophor and Tween 80 caused intermediate effects on these parameters that were statistically significant for total clearance, half-life, and volume of distribution. Cremophor had no adverse effect on liver function, whereas Tween 80 caused haemolysis and cholestasis. The initial high-dose Cremophor perfusate concentration was 0.8 mg/ml, which previous studies have shown to be clinically relevant and close to the optimal level for MDR reversal in vitro (1.0 mg/ml). Cremophor may be a clinically useful MDR modulator, but it may alter the pharmacokinetics of the cytotoxic drug. Received: 5 January 1995/Accepted: 25 August 1995     

多药耐药基因MDR1及P-gp蛋白在乳腺癌组织中的表达及临床意义

目的检测乳腺癌组织中多药耐药基因MDR1及P-gp蛋白的表达,并探讨其表达与临床病理因素的关系及MDR1与P-gp的相关性。方法采用荧光定量RT-PCR(FQ-RT-PCR)法检测61例乳腺癌、22例对照组(包括11例乳腺良性疾病、11例癌旁正常组织)中MDR1基因的表达,同时采用免疫组化法检测上述标本中P-gp蛋白的表达。结果乳腺癌组织中MDR1基因扩增率为50.82%(31/61),与正常对照组相比差异有统计学意义,P=0.0006。乳腺癌中P-gp蛋白阳性率为42.62%(26/61),其表达与年龄、肿瘤大小、淋巴结转移、ER、PR、月经状况无关;MDR1基因扩增率高于P-gp蛋白表达,二者呈高度相关,但并不完全相符。结论乳腺癌中存在多药耐药基因MDR1及P-gp蛋白的表达,且其表达呈正相关。检测上述基因及其蛋白的表达,可预测乳腺癌的多药耐药。     

The role of the MDR1 gene in the development of multidrug resistance in human hepatoblastoma: clinical course and in vivo model

BACKGROUND: The P-glyprotein (P-gp), which is a membrane channel encoded by the MDR1 gene, represents a possible explanation for multidrug resistance in human hepatoblastoma (HB). P-gp shows up-regulation in tumor cells after chemotherapy; however, to date, its exact role in HB has not been described. The authors investigated the role of the MDR1 gene in the clinical course of patients with HB and in an in vivo model of HB. They also studied the effects of the MDR1 antagonizer PSC 833 on chemotherapy in mice xenotransplanted with HB. METHODS: Resected tumor specimens, including both primary tumors and recurrent tumors, from a child suffering from HB were investigated histologically. Cell suspensions from the originally removed tumor were incorporated subcutaneously into nude mice. Animals were treated with cisplatin (CDDP) plus PSC 833. MDR1 gene expression levels in the different resected tumors from the patient and in the xenotransplants after treatment were determined with polymerase chain reaction analysis. RESULTS: MDR1 gene expression was increased in the patient's tumors after every course of chemotherapy from 30% to > 190%. In the xenotransplants, MDR1 gene expression was enhanced significantly after chemotherapy (P(CDDP) = 0.008; P(CDDP+PSC) = 0.002). Tumor volumes (P < 0.001) and serum alpha-fetoprotein levels (P = 0.0002) were significantly lower in the animals that were treated with CDDP + PSC compared with the animals that were treated with CDDP alone. CONCLUSIONS: The current results suggest that MDR1 gene expression and P-gp are a potential mechanism of drug resistance in HB. The chemosensitizer PSC 833 significantly improved the effects of chemotherapy in animals xenotransplanted with HB. These data encourage further studies concerning the role of chemosensitizers in overcoming multidrug resistance in patients with HB.