van Ark-Otte J, Kedde M A, van der Vijgh W J, Dingemans A M, Jansen W J, Pinedo H M, Boven E, Giaccone G
University Hospital Vrije Universiteit, Department of Medical Oncology, Amsterdam, The Netherlands.
Br J Cancer. 1998 Jun;77(12):2171-6. doi: 10.1038/bjc.1998.362.
Irinotecan (CPT-11) is a semisynthetic camptothecin derivative with a broad spectrum of anti-tumour activity. Carboxylesterase (CE) catalyses the conversion of CPT-11 to SN-38 (7-ethyl-10-hydroxycamptothecin), the active form of CPT-11. The antiproliferative effects of CPT-11 and SN-38, CE-activity and topoisomerase I protein expression were investigated in five human small-cell lung cancer (SCLC) cell lines and four human non-small-cell lung cancer (NSCLC) cell lines. Antiproliferative activity, expressed as IC50 values, was determined using the MTT assay. CPT-11 was significantly more active in SCLC than in NSCLC cell lines (P = 0.0036), whereas no significant difference between histological types was observed with SN-38. A significant correlation (r2 = 0.52, P = 0.028) was observed between CE activity and chemosensitivity to CPT-11 but not to SN-38, and significantly higher CE activity was observed in SCLC compared with NSCLC cell lines (P = 0.025). Western blotting experiments showed topoisomerase I protein expressions within a factor of 2, and a granular nuclear staining was detectable in all cell lines by immunocytochemistry of cytospins. No correlation was observed between protein expression and sensitivity to CPT-11 or SN-38. Cellular and medium concentrations of CPT-11 and SN-38 were measured by high-performance liquid chromatography (HPLC) in one SCLC cell line with high CE activity and high sensitivity to CPT-11, and one NSCLC cell line with low sensitivity to CPT-11 and CE activity. Intracellular concentrations of CPT-11 and SN-38 were higher in the SCLC cell line, and this was associated with an increase in cellular uptake of CPT-11 compared with the medium, and an increased intracellular formation of SN-38. In conclusion, CE activity appears to be associated with higher sensitivity to CPT-11 in human lung cancer cell lines and may partly explain the difference in the in vitro sensitivity to CPT-11 between SCLC and NSCLC cells. The assessment of CE activity in clinical material of lung cancer patients undergoing treatment with CPT-11 may be warranted. However, other mechanisms may influence sensitivity to CPT-11, possibly including drug transport.
伊立替康（CPT - 11）是一种具有广泛抗肿瘤活性的半合成喜树碱衍生物。羧酸酯酶（CE）催化CPT - 11转化为SN - 38（7 - 乙基 - 10 - 羟基喜树碱），即CPT - 11的活性形式。在5种人小细胞肺癌（SCLC）细胞系和4种人非小细胞肺癌（NSCLC）细胞系中研究了CPT - 11和SN - 38的抗增殖作用、CE活性以及拓扑异构酶I蛋白表达。使用MTT法测定以IC50值表示的抗增殖活性。CPT - 11在SCLC细胞系中的活性显著高于NSCLC细胞系（P = 0.0036），而SN - 38在不同组织学类型之间未观察到显著差异。观察到CE活性与对CPT - 11而非SN - 38的化学敏感性之间存在显著相关性（r2 = 0.52，P = 0.028），并且与NSCLC细胞系相比，SCLC细胞系中观察到显著更高的CE活性（P = 0.025）。蛋白质印迹实验显示拓扑异构酶I蛋白表达在2倍范围内，通过细胞涂片免疫细胞化学在所有细胞系中均可检测到颗粒状核染色。未观察到蛋白表达与对CPT - 11或SN - 38的敏感性之间存在相关性。在一种具有高CE活性且对CPT - 11高度敏感的SCLC细胞系和一种对CPT - 11和CE活性低敏感的NSCLC细胞系中，通过高效液相色谱（HPLC）测量细胞和培养基中CPT - 11和SN - 38的浓度。SCLC细胞系中CPT - 11和SN - 38的细胞内浓度更高，这与CPT - 11相对于培养基的细胞摄取增加以及SN - 38细胞内形成增加有关。总之，CE活性似乎与人肺癌细胞系中对CPT - 11的更高敏感性相关，并且可能部分解释了SCLC和NSCLC细胞之间对CPT - 11体外敏感性的差异。对接受CPT - 11治疗的肺癌患者临床材料中的CE活性进行评估可能是必要的。然而，其他机制可能影响对CPT - 11的敏感性，可能包括药物转运。
