Prognostic significance of cytochemical analysis of leukemic M2 blasts

[Correlation between myeloperoxidase expression and gene alterations and prognosis in acute myeloid leukemia]

目的

观察髓过氧化物酶（MPO）在急性髓系白血病（AML）中的表达，探讨其与AML临床特征、基因突变、疗效和预后的关系。

方法

回顾性分析233例初诊AML患者骨髓中原始细胞MPO表达的阳性率，根据MPO表达率不同将其分为MPO低表达组（MPO≤70%）与MPO高表达组（MPO>70%），并对两组患者的临床特征、基因突变、疗效和预后进行比较。

结果

①233例AML患者中MPO低表达组121例（51.9%），MPO高表达组112例（48.1%）。NCCN预后良好组患者多为MPO高表达（χ²=32.773，P<0.001），而MPO低表达与预后不良核型相关（χ²=7.078，P=0.008）。②MPO低表达组DNMT3A基因（χ²=6.905，P=0.009）、RNA剪接复合物相关基因（SF3B1/SRSF2/U2AF1）（χ²=5.246，P=0.022）、RUNX1基因（χ²=4.577，P=0.032）、ASXL1基因（χ²=7.951，P=0.005）及TP53基因(P=0.004）突变发生率明显高于MPO高表达组，而C-KIT基因（χ²=8.936，P=0.003）及CEBPA基因（χ²=12.340，P<0.001）突变更多见于MPO高表达组，尤其CEBPA双位点突变。③MPO低表达组首次诱导治疗缓解（CR₁）率为38.8%，MPO高表达组为68.1%，差异有统计学意义（χ²=15.197，P<0.001）。多因素分析显示MPO低表达是影响患者CR₁的独立危险因素。④MPO低表达组患者的2年总生存（OS）率及无进展生存（PFS）率均明显低于高表达组（18.0%对89.4%和11.5%对56.7%），差异有统计学意义（χ²分别为15.212和17.016，P值均<0.001）。Cox模型多因素分析显示MPO低表达是影响患者OS及PFS的独立预后不良指标。⑤正常核型AML中，MPO低表达组患者OS和PFS差于MPO高表达组（2年OS率：31.1%对83.7%，χ²=2.895，P=0.089；2年PFS率：18.8%对45.8%，χ²=5.068，P=0.024）。

结论

不同MPO表达的AML具有独特的基因突变谱；MPO低表达是影响AML患者CR₁、OS和PFS的独立危险因素，细胞化学染色检测MPO表达可能为评估AML疗效和预后提供一种简单而有效的手段。

Myeloperoxidase expression in acute myeloid leukemia helps identifying patients to benefit from transplant

PURPOSE

Despite extensive study, the use of allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia (AML) vary considerably. The decision of which of these options to choose is complex and depends on both clinical and molecular variables as well as the availability and histocompatability of donor stem cells. So far there is no clear explanation on whether the expression of myeloperoxidase (MPO) relates to the prognosis of AML.

MATERIALS AND METHODS

We retrospectively analyzed the prognostic significance of the MPO expression in the 140 patients with diagnosed AML treated at a single institution.

RESULTS

In our study, MPO expression was associated with disease-free survival (DFS) and transplant was beneficial to overcome a negative prognostic effect of MPO-negative at diagnosis based upon the result that the DFS in patients received transplants are not significant between the MPO-positive group and MPO-negative group although DFS in all patients was different according to MPO expression.

CONCLUSION

MPO expression at diagnosis helps to choose therapy for each AML patient and can differentiate AML patients who need transplantation.

Myeloperoxidase Is a Key Regulator of Oxidative Stress–Mediated Apoptosis in Myeloid Leukemic Cells

PURPOSE

We reported previously that reactive oxygen species (ROS) are key mediators of apoptosis induced by a polyphenol, (-)-epigallocatechin-3-gallate (EGCG), in myeloid leukemic cells. This study aimed to further examine the mechanism of ROS-mediated apoptosis induced by EGCG and its relationship to the heme enzyme myeloperoxidase (MPO).

EXPERIMENTAL DESIGN

We established stably transfected K562 cells expressing wild-type and mutant MPO. Then, sensitivity against EGCG and other ROS-inducing agent was examined and further investigated the detailed molecular mechanism of ROS-inducing apoptosis in MPO-positive leukemic cells.

RESULTS

EGCG rapidly induced apoptosis in MPO-positive leukemia cells. Preincubation of myeloid leukemic cells with the MPO-specific inhibitor, 4-aminobenzoic acid hydrazide, and the heme biosynthesis inhibitor, succinylacetone, resulted in inhibition of the intracellular MPO activity, ROS production, and induction of apoptosis following addition of EGCG. Overexpression of MPO sensitized EGCG-resistant K562 cells to apoptosis induced by EGCG. In contrast, an enzymatically inactive MPO mutant-expressing K562 cell could not respond to EGCG, suggesting that MPO is important for determining the sensitivity to EGCG-induced oxidative stress. Hypochlorous acid scavengers and the hydroxyl radical (.OH) scavenger inhibited EGCG-induced apoptosis in myeloid leukemic cells. The fluorescence intensity of both aminophenyl fluorescein- and hydroxyphenyl fluorescein-loaded myeloid leukemic cells significantly increased on stimulation with EGCG, indicating that EGCG generated highly toxic ROS in myeloid leukemic cells.

CONCLUSIONS

These results indicated that highly toxic ROS such as .OH generated via the hydrogen peroxide/MPO/halide system induce apoptosis and that ROS may be the direct mediators of EGCG-induced apoptosis in MPO-positive leukemic cells.

The percentage of myeloperoxidase-positive blast cells is a strong independent prognostic factor in acute myeloid leukemia, even in the patients with normal karyotype

To examine whether the percentage of myeloperoxidase (MPO)-positive blast cells is useful as a prognostic factor for acute myeloid leukemia (AML), cytochemical analysis of MPO was performed in 491 patients who were registered to the Japan Adult Leukemia Study Group-AML92 study. Patients were divided into two using the percentage of MPO-positive blast (high [>or=50%] and low (<50%)). Complete remission rates were 85.4% in the former and 64.1% in the latter (P=0.001). The overall survival (OS) and the disease-free survival (DFS) were significantly better in the high MPO group (48.3 vs 18.7% for OS, and 36.3 vs 20.1% for DFS, P<0.001, respectively). Multivariate analysis showed that both karyotype and the percentage of MPO-positive blast cells were equally important prognostic factors. The high MPO group still showed a better survival even when restricted to the intermediate chromosomal risk group or the patients with normal karyotype (P<0.001). The OS of patients with normal karyotype in the high MPO group was almost equal with that of the favorable chromosomal risk group. The percentage of MPO-positive blast cells is a simple and highly significant prognostic factor for AML patients, and especially useful to stratify patients with normal karyotype.