Laurencot C M, Andrews P A, Kennedy K A
Department of Pharmacology, George Washington University Medical Center, Washington, DC 20037, USA.
Oncol Res. 1995;7(7-8):363-9.
Previous results from this laboratory indicated that EMT6 cells treated with inhibitors of the intracellular pH (pHi) regulatory mechanisms were resistant to cisplatin (Laurencot, C.M.; Kennedy, K.A. The effect of low pH on the cytotoxicity of cisplatin in EMT6 mouse mammary tumor cells. Oncol. Res. 7:371-380; 1995.) This inhibitor-induced cisplatin resistance was independent of pH. The purpose of the research presented here was to characterize further cisplatin resistance observed in cells cultured with the Na+/H+ antiport inhibitor 5-(N,N hexamethylene) amiloride (NHMA) and the HCO3-/Cl- exchanger inhibitor 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). Using [195mPt]-DDP, the accumulation of cisplatin into EMT6 mouse mammary tumor cells treated with NHMA and SITS was not changed. Total DNA cross-link formation and DNA-interstrand cross-link formation, however, decreased in NHMA- and SITS-treated cells. Since cisplatin accumulation was unchanged in NHMA- and SITS-treated cells but the amount of DNA cross-links decreased, the intracellular activation of cisplatin appeared to be altered in the cisplatin-resistant cells. Because SITS interferes with chloride transport and chloride has been proposed to be involved in cisplatin activation, cisplatin toxicity in EMT6 cells was evaluated in chloride-deficient medium. EMT6 cells cultured in chloride-deficient medium were less sensitive to cisplatin than cells cultured in chloride-containing medium, but this sensitivity was not altered by NHMA and SITS. Furthermore, the resistance to cisplatin in cells treated with NHMA and SITS was similar in chloride-containing and chloride-deficient medium. These data suggest that the concentration of other ions, in addition to chloride, may be important for cisplatin toxicity.
该实验室之前的研究结果表明，用细胞内pH（pHi）调节机制抑制剂处理的EMT6细胞对顺铂具有抗性（劳伦科特，C.M.；肯尼迪，K.A. 低pH对顺铂在EMT6小鼠乳腺肿瘤细胞中细胞毒性的影响。肿瘤研究。7:371 - 380；1995年）。这种抑制剂诱导的顺铂抗性与pH无关。本文所述研究的目的是进一步表征在用Na⁺/H⁺反向转运体抑制剂5 -（N，N - 六亚甲基）氨氯吡脒（NHMA）和HCO₃⁻/Cl⁻交换体抑制剂4 - 乙酰氨基 - 4'-异硫氰酸基芪 - 2,2'-二磺酸（SITS）培养的细胞中观察到的顺铂抗性。使用[¹⁹⁵mPt]-顺铂，NHMA和SITS处理的EMT6小鼠乳腺肿瘤细胞中顺铂的积累没有变化。然而，在NHMA和SITS处理的细胞中，总DNA交联形成和DNA链间交联形成减少。由于NHMA和SITS处理的细胞中顺铂积累没有变化，但DNA交联量减少，顺铂抗性细胞中顺铂的细胞内活化似乎发生了改变。因为SITS干扰氯离子转运，并且有人提出氯离子参与顺铂活化，所以在缺氯培养基中评估了EMT6细胞对顺铂的毒性。在缺氯培养基中培养的EMT6细胞对顺铂的敏感性低于在含氯培养基中培养的细胞，但NHMA和SITS并未改变这种敏感性。此外，在含氯和缺氯培养基中，用NHMA和SITS处理的细胞对顺铂的抗性相似。这些数据表明，除了氯离子外，其他离子的浓度可能对顺铂毒性也很重要。
