Quantitative detection of circulating nucleophosmin mutations DNA in the plasma of patients with acute myeloid leukemia.

OBJECTIVE: The aim of this study was to quantify the copies of circulating nucleophosmin (NPM) mutations DNA in the plasma of patients with acute myeloid leukemia (AML) and to explore the association of circulating NPM mutation levels with clinical characteristics. DESIGN AND METHODS: The presence of NPM mutations in 100 Chinese patients newly diagnosed with AML were identified by RT-PCR and sequencing analysis. Copies of circulating NPM mutation A (NPM mut.A) DNA in the plasma of mutation-positive cases were quantified by real-time quantitative PCR (qRT-PCR). Furthermore, the association of circulating NPM mutation levels and clinical characteristics was analyzed. RESULTS: NPM mutations were identified in 37 of the 100 patients and all cases were NPM mut.A. The circulating NPM mut.A levels ranged from 0.35×10(8) copies/ml to 6.0×10(8) copies/ml in the 37 mutation-positive cases. The medium and quartile M (P25, P75) of the circulating NPM mut.A levels in patients classified as M2, M4 and M5 morphological subtypes were 1.35×10(8) (0.76×10(8), 1.91×10(8)) copies/ml, 1.81×10(8) (1.47×10(8), 2.2×10(8)) copies/ml and 2.50×10(8) (2.42×10(8), 3.05×10(8)) copies/ml, respectively. Circulating NPM mut.A levels were significantly higher in patients with the M5 subtype of AML compared to patients with the M2 and M4 subtypes (p=0.000, p=0.046). In addition, circulating NPM mut.A copies were significantly associated with a higher white blood cell count, platelet count and bone marrow blast percentage (p<0.05). CONCLUSION: Our results suggest that circulating NPM mutations DNA assay serves as a complementary to the routine investigative protocol of NPM-mutated leukemia.

Nucleophosmin gene mutations promote NIH3T3 cell migration and invasion through CXCR4 and MMPs.

Nucleophosmin (NPM1) plays key roles in ribosome biogenesis, centrosome duplication, and maintenance of genomic integrity. NPM1 mutations have been recently identified as the most frequent genetic alteration in acute myeloid leukemia and are related to leukemogenesis. NPM1 mutations are involved in the regulation of cell proliferation, cell cycle, and apoptosis. However, the oncogenic potential of NPM1 mutations is not fully understood. Here, we investigated the change of cell migration and invasion in vitro and the role of NPM1 mutations in this process. In our study, NIH3T3 cells were transfected with plasmids encoding NPM1 mutation A (NPM1 mA), and the cell chemotactic response in vitro was evaluated by cell migration and invasion assays. In addition, the expression levels of MMP-2, MMP-9 and CXCR4 were assayed by quantitative real-time PCR and western blotting. Our findings suggested that the migration and invasion of NIH3T3 cells were significantly enhanced after transfection with NPM1 mA (p<0.01). Furthermore, there was greater expression of MMP-9 and CXCR4 (p<0.01), but a lower expression of MMP-2 in the NPM1 mA group. These results demonstrate that NPM1 mutations may promote cell migration and invasion in vitro, and MMP-9 and CXCR4 may be involved in the regulation of cell invasion. Thus, this study sheds new light on the effect of NPM1 mutations on leukemogenesis.

Monoclonal antibodies against nucleophosmin mutants: potentials for the detection of acute myeloid leukemia.

Nucleophosmin (NPM1) gene mutations resulting in cytoplasmic delocalization of Nucleophosmin (NPMc+) are the most common genetic alteration in acute myeloid leukemia (AML). Here, we attempted to prepare monoclonal antibodies (mAbs) against NPM1 mutation A (NPM-mA) and investigated the mAbs' clinical utility in immunohistochemical detection of NPMc+AML. The pET-32a-NPM-mA vector with the whole open reading frame of the NPM-mA gene was constructed. E.coli BL21 transformed with the vector were induced to express the NPM-mA recombinant protein. BALB/c mice were immunized with the recombinant NPM-mA. Positive clones were selected by indirect ELISA and the mAbs were obtained. Immunohistochemistry was performed to detect the NPMc+ in bone marrow smears from 10 AML patients with NPM-mA. The results showed that the pET-32a-NPM-mA vector was successfully constructed and the NPM-mA recombinant protein was used to immunize the mice. Two positive clones (2G3 and 3F9) were selected. The mAbs against NPM-mA were raised, but did cross-react with wild type NPM1. The mAbs can be used to detect the cytoplasmic dislocation of NPM1 in all AMLs carrying NPM-mA. Our results show that anti-NPM-mA mAbs were produced. Though they would cross-react with wild type NPM1, the mAbs may still have potential in the detection of NPMc+AMLs.

Increased integrity of circulating cell-free DNA in plasma of patients with acute leukemia.

BACKGROUND: Increased cell-free DNA (cf-DNA) and the integrity of cf-DNA in plasma of patients with cancer has been described. We investigated the clinical utility of cf-DNA in the detection and monitoring of progression of leukemia. METHODS: Plasma samples from 60 patients with acute leukemia were analyzed in comparison to plasma from 30 healthy controls. Plasma DNA was determined by quantitative PCR (qPCR) by amplifying the ß-actin gene (ACTB). The DNA integrity index was calculated as the ratio of qPCR results (ACTB384/106). Paired diagnostic/complete remission (CR)/relapse samples from eight of 60 patients were analyzed, and the minimum residual disease (MRD) situations were monitored. RESULTS: DNA concentrations (median: 8.80 ng/mL, p=0.004) and DNA integrity (median: 0.51, p<0.001) in cancer patients were significantly higher. Receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve of DNA and DNA integrity were 0.79 and 0.88, respectively. DNA integrity at CR had a distinct reduction and then an increase at relapse. DNA integrity in CR cases was higher than that observed in healthy controls. CONCLUSIONS: Our preliminary data suggest that plasma DNA integrity is increased in acute leukemia and may be a potential biomarker for monitoring MRD. However, more work is needed.

Mixed lineage leukaemia histone methylases 1 collaborate with ERα to regulate HOXA10 expression in AML.

HOXA10, a homeobox-containing gene involved in definitive haematopoiesis, which implicated in the pathogenesis of AML (acute myeloid leukaemia), has been studied extensively. But the regulatory mechanism that drives HOXA10 expression is still unclear. In the present paper, HOXA10 regulated by MLL1 (mixed lineage leukaemia histone methylase 1) with an epigenetic way has been demonstrated. The HOXA10 promoter contains several EREs (oestrogen response elements), including ERE1 and ERE2, which are close to the transcription start site, and are associated with E2-mediated activation of HOXA10. It has been shown that knockdown of the ERα (oestrogen receptor α) suppresses E2-mediated activation of HOXA10. Similarly, knockdown of MLL1 suppresses activation of HOXA10 and is bound to the ERE of HOXA10 promoter in an E2-dependent manner by forming complex with ERα. Knockdown of ERα affects the E2-dependent binding of MLL1 into HOXA10 EREs, suggesting critical roles of ERα in recruiting MLL on the HOXA10 promoter. More interestingly, the methylation status of histone protein H3K4 (H3 at lysine 4) with E2 is much higher than without E2 treatment in leukaemia cell. On the contrary, the methylation status of HOXA10 promoter with E2 treatment is much lower, which elevate the HOXA10 expression. Moreover, with ERα knockdown, the H3K4 methylation level is also decrease in myeloid cell. Overall, it has been clearly demonstrated that HOXA10 is transcriptionally regulated by MLL1, which, in coordination with ERα, plays a critical role in this process with epigenetic way and suggests a potential anti-E2 treatment of AML.