Introduction: Cytogenetically normal acute myeloid leukemia (CN-AML) accounts for 40 to 50 percent of all AML and shows significant heterogeneity in clinical outcomes. Despite the advancements in the molecular pathophysiology of CN-AML, clinical outcome of this leukemia remains to be elucidated. Prohibitin (PHB) were typically known to have the potential act as a tumor suppressor, anti-proliferative regulator of cell-cycle in normal cells. However, our previous study discovered that high expression of PHB in AML cells was involved in escaping apoptosis process. In this study, we investigated the clinical significance of expression levels of PHB1 and PHB2 genes in patients with CN-AML.
Methods: We developed quantitative reverse transcription PCR (qRT-PCR) detection system for mRNA expression status for PHB1 and PHB2.The expression levels was analyzed in 69 CN-AML patients. Total RNA was extracted from bone marrow samples at the diagnosis using InvitrogenRNAqueous Total RNA Isolation Kit (Thermo Fisher Scientific, USA). The concentration of isolated total RNA was measured by Micro UV-VIS spectrophotometer (Malcom, Japan). Quantification of mRNA of PHBs were performed in CFX96 Touch Real-Time PCR system (BIO-RAD, USA) using our laboratory-developed, customized primers and probes.The gene expression levels werenormalized compared to those of ABL1 gene.Survival analysis was performed compared with other prognostic factors: age, NPM1 mutation, and FLT3-ITD. FLT3-ITD was tested by PCR & fragment analysis (LeukoStrat FLT3 Mutation kit; Invivoscribe, USA) and NPM1 mutation was tested using qRT-PCR kit (ipsogen NPM1 MutaQuant; Qiagen, Germany). All statistical computations and graphical process were performed using R version 3.5.1. A P value ≤ 0.05 (for 95% confidence interval) was considered statistically significant.
Results: The median age of enrolled patients was 68 (ranged 23-85) at the diagnosis. The ratio of male and female was 1:0.86 (37:32). There was no significant difference in age, sex, WBC count in peripheral blood, blast percentage of peripheral blood and bone marrow, the achievement rate of complete remission, and the enforcement of stem cell transplant according to expression status of PHB1 and PHB2. Using 0.61 as cutoff, PHB1 high-expressed group showed superior overall survival (OS) (47.7% vs 15.1%; P = 0.014) and low hazard ratio (0.43 [95% CI: 0.215-0.861]; P = 0.017) compared to PHB1 low-expressed group. In PHB2, using a cutoff 2.39, high-expressed group showed as inferior OS (17.5% vs 40.0%; P = 0.16) and high hazard ratio (1.93 [95% CI:0.739-5.042]; P = 0.18) compared to low expressed group.
Conclusions: PHB1 expression status was associated with favorable clinical outcome. In contrast, those of PHB2 was related with poor prognosis in CN-AML.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.