Theyer G, Schirmböck M, Thalhammer T, Sherwood E R, Baumgartner G, Hamilton G
Department of Urology, Wilhelminenspital, Vienna, Austria.
J Urol. 1993 Nov;150(5 Pt 1):1544-7. doi: 10.1016/s0022-5347(17)35838-x.
The treatment of advanced metastatic prostate cancer by hormone manipulation or orchiectomy is frequently followed by the appearance of hormone-insensitive and highly chemoresistant tumor cells. In this study we have investigated the contribution of the P-glycoprotein-mediated drug efflux (multidrug-resistance; MDR) to the cellular resistance of prostate carcinoma-derived cell lines to diverse cytotoxic drugs by detection of P-glycoprotein (P-gp) measurement of P-gp-mediated drug transport and reversal of MDR by chemosensitizers. The in vitro chemosensitivity of three prostate cancer cell lines (PC-3, DU-145 and LNCaP) to doxorubicin was measured in a thymidine incorporation proliferation assay. Growth of the partially hormone-sensitive cell line LNCaP is inhibited by low doses of doxorubicin (IC50:27 ng./ml.), but PC-3 and DU-145 are highly resistant to the drug, with IC50 values of 10 micrograms./ml. and 7.5 micrograms./ml., respectively. The chemosensitivity of the PC-3 and DU-145 cells is increased in response to 1 microM. verapamil, 1 micrograms./ml. cyclosporine A and 2 microM. tamoxifen, which are known to partially reverse the MDR phenotype in other resistant tumors. A verapamil-sensitive drug efflux has been demonstrated for the PC-3 and Du-145, but not for the LNCaP, cell lines, using flow cytometric measurements of the P-gp substrate rhodamine 123 efflux from preloaded cells. In agreement with the functional measurements, the expression of the P-glycoprotein was detected in the PC-3 and Du-145 cell lines in Western blots using the monoclonal C 219 antibody. In conclusion, the chemoresistant and hormone-insensitive PC-3 and Du-145 cell lines express P-gp and exhibit verapamil-sensitive drug efflux, indicative of MDR. However, the low MDR-reversal rates observed in these cell lines in response to chemosensitizers in clinically achievable concentrations (approximately 2- to 3-fold reversal), point to non-MDR-associated cellular mechanisms as dominant factors of chemoresistance in prostate cancer.
通过激素调控或睾丸切除术治疗晚期转移性前列腺癌后，常常会出现激素不敏感且高度耐化疗的肿瘤细胞。在本研究中，我们通过检测P-糖蛋白（P-gp）、测量P-gp介导的药物转运以及用化学增敏剂逆转多药耐药（MDR），研究了P-糖蛋白介导的药物外排（多药耐药；MDR）对前列腺癌衍生细胞系对多种细胞毒性药物的细胞耐药性的影响。在一项胸苷掺入增殖试验中，测定了三种前列腺癌细胞系（PC-3、DU-145和LNCaP）对阿霉素的体外化疗敏感性。低剂量的阿霉素（IC50：27 ng./ml.）可抑制部分激素敏感的细胞系LNCaP的生长，但PC-3和DU-145对该药物高度耐药，IC50值分别为10 μg./ml.和7.5 μg./ml.。PC-3和DU-145细胞对1 μM维拉帕米、1 μg./ml环孢素A和2 μM他莫昔芬的化疗敏感性增加，已知这些药物可部分逆转其他耐药肿瘤中的MDR表型。使用流式细胞术测量预加载细胞中P-gp底物罗丹明123的外排，已证明PC-3和Du-145细胞系存在维拉帕米敏感的药物外排，但LNCaP细胞系不存在。与功能测量结果一致，使用单克隆C 219抗体的Western印迹法在PC-3和Du-145细胞系中检测到了P-糖蛋白的表达。总之，化疗耐药且激素不敏感的PC-3和Du-145细胞系表达P-gp并表现出维拉帕米敏感的药物外排，表明存在MDR。然而，在这些细胞系中，对临床可达到浓度的化学增敏剂的MDR逆转率较低（约2至3倍逆转），这表明非MDR相关的细胞机制是前列腺癌化疗耐药的主要因素。
