Damiani D, Michieli M, Ermacora A, Candoni A, Raspadori D, Geromin A, Stocchi R, Grimaz S, Masolini P, Michelutti A, Scheper R J, Baccarani M
Department of Medical and Morphological Research and Udine University Hospital, Udine, Italy.
Haematologica. 1998 Apr;83(4):290-7.
In cell lines, there is an ongoing debate about the role of the lung resistance-related protein (LRP) whereas the role played by P-glycoprotein (PGP) in determining a multidrug resistance is well known. The aim of this study was to evaluate the frequency and the role of a PGP and an LRP overexpression in affecting the intracellular daunorubicin accumulation (IDA) and in predicting the therapy outcome on a subset of overt secondary acute non lymphocytic leukemias (ANLL). An adjunctive point was to evaluate the efficacy of the reversal agent SDZ PSC 833 (PSC) in counteracting impaired IDA.
By flow cytometry, PGP and LRP expression and the IDA were evaluated on 54 overt secondary ANLL PGP and LRP overexpressions were respectively defined by an MRK-16 mean fluorescence index (MFI) > or = 6 (PGP+) and by an LRP-56 MFI > or = 5 i.e. by MRK-16 and LRP-56 MFIs higher than the one observed in normal leukocytes. The blasts' IDA was studied after a two-hour incubation in 1000 ng/mL daunorubicin in the presence or in the absence of the MDR reversal agent SDZ PSC 833 (PSC) 1.6 mumol.
A PGP overexpression was detected in 40/54 (74%) cases while an LRP overexpression was observed on 33/54 (61%) cases. No differences were found in terms of PGP and LRP expressions between ANLL developing after chemo/radiotherapy (therapy-related ANLL) or evolving from a myelodysplastic syndrome (MDS-related ANLL). Compared to the PGP-, the PGP+ cases showed a significantly lower mean IDA (DNR NMFI 196 +/- 46 vs. 267 +/- 53, p < 0.001). The co-incubation of DNR with the PSC significantly increased only the mean IDA of the PGP+ cases, that grew from a DNR NMFI of 196 +/- 46 to a DNR NMFI of 284 +/- 67 (p < 0.0001). With respect to normal leukocytes, even the PGP- cases had an impaired IDA suggesting that other mechanisms, including an LRP overexpression, could affect the IDA. A strongly negative correlation was observed between PGP overexpression and therapy outcome, in fact, 8/10 (80%) PGP- but only 2/27 (7%) PGP+ patients obtained complete remission (p = 0.0002). Moreover, 7/33 (21%) cases showing an impaired IDA (NMFI < 280) but 4/4 (100%) with NMFI > 280 had complete remission (p = 0.006). No correlation was found between therapy response and LRP or CD34 expression.
This data suggests that an important role in determining therapy outcome is played by PGP in secondary leukemias. Even if the LRP is frequently overexpressed in secondary leukemias and is likely to contribute to the reduction of the intracellular drug accumulation, the role played by LRP in determining the therapy-outcome has still to be cleared.
在细胞系中，关于肺耐药相关蛋白（LRP）的作用一直存在争议，而P-糖蛋白（PGP）在多药耐药中的作用已为人熟知。本研究旨在评估PGP和LRP过表达在影响柔红霉素细胞内蓄积（IDA）以及预测一组明显的继发性急性非淋巴细胞白血病（ANLL）治疗结果方面的频率和作用。另一个要点是评估逆转剂SDZ PSC 833（PSC）在对抗IDA受损方面的疗效。
通过流式细胞术，对54例明显的继发性ANLL患者评估PGP和LRP表达以及IDA。PGP和LRP过表达分别通过MRK-16平均荧光指数（MFI）≥6（PGP+）和LRP-56 MFI≥5来定义，即通过MRK-16和LRP-56 MFI高于正常白细胞中的观察值来定义。在存在或不存在1.6 μmol MDR逆转剂SDZ PSC 833（PSC）的情况下，将细胞在1000 ng/mL柔红霉素中孵育两小时后研究原始细胞的IDA。
40/54（74%）例检测到PGP过表达，33/54（61%）例观察到LRP过表达。化疗/放疗后发生的ANLL（治疗相关ANLL）或由骨髓增生异常综合征演变而来的ANLL（MDS相关ANLL）在PGP和LRP表达方面未发现差异。与PGP-病例相比，PGP+病例的平均IDA显著更低（DNR NMFI 196±46对267±53，p<0.001）。DNR与PSC共同孵育仅显著增加了PGP+病例的平均IDA，从DNR NMFI 196±46增加到DNR NMFI 284±67（p<0.0001）。与正常白细胞相比，即使是PGP-病例的IDA也受损，提示其他机制，包括LRP过表达，可能影响IDA。PGP过表达与治疗结果之间观察到强烈的负相关，实际上，8/10（80%）PGP-但仅2/27（7%）PGP+患者获得完全缓解（p = 0.0002）。此外，7/33（21%）例IDA受损（NMFI<280）但4/4（100%）NMFI>280的患者获得完全缓解（p = 0.006）。未发现治疗反应与LRP或CD34表达之间的相关性。
该数据表明PGP在继发性白血病治疗结果的决定中起重要作用。即使LRP在继发性白血病中经常过表达且可能导致细胞内药物蓄积减少，但LRP在决定治疗结果中的作用仍有待明确。
