Zhou D C, Hallam S J, Lee S J, Klein R S, Wiernik P H, Tallman M S, Gallagher R E
Department of Oncology, Montefiore Medical Center and Albert Einstein Cancer Center, Bronx, New York 10467, USA.
Cancer Res. 1998 Dec 15;58(24):5770-6.
The up-regulation of cellular retinoic acid binding protein-II (CRABP-II) has been invoked as an important mechanism of clinically acquired resistance to all-trans retinoic acid (RA) therapy in acute promyelocytic leukemia (APL). To test this hypothesis, we used quantitative reverse transcription-PCR and fast performance liquid chromatography procedures to examine the levels of CRABP-II mRNA and RA binding activity in APL patient samples. We found that CRABP-II mRNA in APL cells from pretreatment patients (n = 36) was constitutively expressed at relatively high levels (median, 0.92; range, 0.16-4.13) relative to the level in CRABP-H protein-expressing NB4 cells (arbitrarily set at 1.0 unit). Consistent with this finding, the RA binding activity of CRABP in APL cells from three pretreatment cases (range, 27.2-53.2 fmol/mg protein) was similar to that of NB4 cells (22.6 +/- 5.4 fmol/mg protein). Furthermore, in the pretreatment samples, there was no association between CRABP-H mRNA expression level and APL cellular sensitivity to RA-induced differentiation in vitro. After 45 days of remission induction therapy on Eastern Cooperative Oncology Group protocol E2491, CRABP-II mRNA was modestly increased from day 0 values in patients treated with either RA (median increase, 0.41) or chemotherapy (median increase, 0.56), and there was no significant difference between the two treatment groups (P = 0.91). In patients studied after relapse from RA therapy (n = 7), there was a significant decline in APL cell sensitivity to RA-induced differentiation in vitro compared with patients after relapse from chemotherapy (n = 5; P = 0.015-0.055 at three RA concentrations tested), but in the RA relapse cases, there was no change from pretreatment levels of CRABP-II mRNA (median, 0.98) or, in three relapse cases studied, of RA protein binding activity (range, 22.1-70.7 fmol/mg protein). Taken together, our data strongly imply that variations in CRABP-II expression and RA binding activity are not causally related to the development of clinically acquired APL cellular RA resistance, but rather, they suggest that constitutive expression of CRABP-II could have a facilitative role in the response of APL cells to RA.
细胞视黄酸结合蛋白II（CRABP-II）的上调被认为是急性早幼粒细胞白血病（APL）临床获得性全反式维甲酸（RA）治疗耐药的重要机制。为验证该假说，我们采用定量逆转录PCR和快速高效液相色谱法检测APL患者样本中CRABP-II mRNA水平和RA结合活性。我们发现，与表达CRABP-II蛋白的NB4细胞（任意设定为1.0单位）相比，预处理患者（n = 36）的APL细胞中CRABP-II mRNA以相对较高水平组成性表达（中位数为0.92；范围为0.16 - 4.13）。与此发现一致，来自3例预处理病例的APL细胞中CRABP的RA结合活性（范围为27.2 - 53.2 fmol/mg蛋白）与NB4细胞（22.6 ± 5.4 fmol/mg蛋白）相似。此外，在预处理样本中，CRABP-II mRNA表达水平与APL细胞体外对RA诱导分化的敏感性之间无关联。按照东部肿瘤协作组E2491方案进行45天缓解诱导治疗后，接受RA治疗（中位数增加0.41）或化疗（中位数增加0.56）的患者，其CRABP-II mRNA较第0天的值略有增加，且两组治疗之间无显著差异（P = 0.91）。在接受RA治疗后复发的患者（n = 7）中，与化疗后复发的患者（n = 5；在三个测试的RA浓度下P = 0.015 - 0.055）相比，APL细胞体外对RA诱导分化的敏感性显著下降，但在RA复发病例中，CRABP-II mRNA的水平（中位数为0.98）与预处理时无变化，在三个复发病例中，RA蛋白结合活性（范围为22.1 - 70.7 fmol/mg蛋白）也无变化。综上所述，我们的数据强烈表明，CRABP-II表达和RA结合活性的变化与临床获得性APL细胞RA耐药的发生无因果关系，相反，它们提示CRABP-II的组成性表达可能在APL细胞对RA的反应中起促进作用。
