4-Hydroxyphenyl Retinamide Preferentially Targets FLT3 Mutated Acute Myeloid Leukemia via ROS Induction and NF-κB Inhibition.

FMS-like tyrosine kinase 3 (FLT3) mutation is strongly associated with poor prognosis in acute myeloid leukemia (AML). Though many FLT3 inhibitors have been developed for clinical application with 34%-56% complete remission rate, patients would develop resistance sooner or later after initial response to tyrosine kinase inhibitors (TKIs), such as gilteritinib. And increasing studies have shown that several resistance related mutations of FLT3 emerged during the AML progression. Thus, further investigation is warranted for these FLT3mut AML patients to achieve a better treatment outcome. 4-Hydroxyphenyl retinamide (4-HPR) has been investigated extensively in animal models and clinical trials as an anticancer/chemopreventive agent and is currently used for protection against cancer development/recurrence, with minimal side effects. In this study, we performed gene-set enrichment analysis and found that down-regulated genes induced by 4-HPR were associated with FLT3-ITD gene sets. CD34+ AML stem/progenitor cells separated from 32 AML samples were treated with 4-HPR. Correlation analysis showed that AML cells with FLT3-ITD genetic alteration were more sensitive to 4-HPR treatment than those without FLT3-ITD. Next, we treated 22 primary AML cells with 4-HPR and found that 4-HPR was more toxic to AML cells with FLT3-ITD. These results indicated that 4-HPR was preferentially cytotoxic to all FLT3-ITD AML+ cells irrespective of stem/progenitor cells or blast cells. 4-HPR-induced reactive oxygen species (ROS) production and NF-κB inhibition might be the reason of 4-HPR selectivity on FLT3 mutated AML cells.

[Detecting phospho-signaling protein of bone marrow leukemia cells by phospho-signaling flow cytometry].

The purpose of this study was to establish the phospho-specific flow cytometry (phospho-flow) to detect the phosphorylated signaling proteins of leukemia cells and to evaluate its useful value in leukemia study. The bone marrow of leukemia children was collected, and treated by phospho-flow of extracted mononuclear cells (MNC) and phospho-flow of directly fixed bone marrow (BM) respectively. In phospho-flow of extracted MNC, the MNC extracted from BM were fixed and permeabilized, then were cultured with P-AKT and P-ERK1/2, finally were analyzed by flow cytometry. In phospho-flow of directly fixed BM, the BM was treated with fixation/lysis buffer and 90% methanol, then were incubated with the surface CD antibody, P-AKT and P-ERK1/2, finally the treated BM cells were analyzed by flow cytometry. The results showed that the positive rates of P-AKT and P-ERK1/2 in MNC treated by phospho-flow of extracted MNC of 26 leukemia children were 46.2% and 30.8% respectively, while the positive rates of P-AKT and P-ERK1/2 in BM treated by phospho-flow of directly fixed BM were 50.0% and 38.5% respectively. The comparison of positive rates of P-AKT and P-ERK1/2 between the 2 treatment protocol showed no difference (p > 0.05). It is concluded that the phospho-flow of directly fixed BM established by our laboratory can be used to analyze the signaling proteins of leukemia cells.

[Effects of acute lymphoblastic leukemia children bone marrow mesenchymal stem cells on drug resistance of K562/A02 cell line].

The aim of study was to investigate the effect of acute lymphoblastic leukemia (ALL) children bone marrow mesenchymal stem cells (MSC) on resistance of K562/A02 cells and its mechanism. MSC obtained from bone marrow of AL children were cultured and identified. The co-culture of MSC and K562/A02 and the culture of K562/A02 cell suspension alone was performed, of which 2 kinds of cells were treated with same concentration of adriamycin (ADM), and the rate of apoptosis was detected by flow cytometry, bcl-2 and bax of K562/A02 were detected by RT-PCR, while mdr1 gene level was detected by FQ-PCR. The results indicated that the MSC separation and proliferation were viable and steady. The apoptosis rate of the K562/A02 cells co-cultured with MSC was 1.97 ± 0.11%, while apoptosis rate of the K562/A02 cells cultured alone was 8.38 ± 0.29%, there was significant difference (p < 0.05). As compared with the K562/A02 cells cultured alone, the bcl-2 gene expression in K562/A02 cells co-cultured with MSC obviously increased; ratio of bcl-2/bax was obviously enhanced. The mdr1 gene level in K562/A02 co-cultured with MSC was no statistical different from K562/A02 cultured alone (p > 0.05), which suggested that adhesion co-cultured with MSC did not induce mdr1 expression higher than the culture of suspension. It is concluded that the MSC of ALL children can escape the leukemia cells from proapoptotic effect of drugs, the resistance of K562/A02 to ADM may be involved in enhancement of bcl-2 gene expression of K562/A02 cells co-cultured with MSC, but not in relation to mdr1 gene in K562/A02 cells themselves.

[Change of CD4(+) CD25(+) regulatory T cells and NK Cells in peripheral blood of children with acute leukemia and its possible significance in tumor immunity].

This study was purposed to investigate the changes of CD4(+) CD25(+) regulatory T cells and NK cells in peripheral blood of acute leukemia children at different stages, the function of immune system and the possible roles of the CD4(+) CD25(+) regulatory T cells as well as NK cells in leukemia immunity. The number and proportion of CD4(+) CD25(+) regulatory T cells and NK cells were detected by flow cytometry in the peripheral blood of 53 acute leukemia children, including 25 patients in new diagnosis and 28 patients in continuous complete remission (CCR), and were compared with that of 20 normal children. The results indicated that the mean proportion of CD4(+) CD25(+) CD127(+) in CD4(+) T cells of peripheral blood in newly diagnosed patients, patients with CCR and normal children were (9.55 +/- 2.41)%, (8.54 +/- 2.51)% and (6.25 +/- 0.85)% respectively, the mean proportions of CD4(+)CD25(+)CD127(+) in newly diagnosed patients and patients with CCR were higher than that in normal children, the mean proportion of CD4(+)CD25(+)CD127(+) in newly diagnosed patients were higher than that in patients with CCR (p < 0.05). At the same time, the NK cell count in patients with acute leukaemia decreased as compared with normal control, while after achieving CCR, the NK cell count in patients were also less than that in normal control (4.11 +/- 3.87% and 10.41 +/- 7.20% vs 14.06 +/- 5.95%, p < 0.05). It is concluded that the application of CD4(+), CD25(+) and CD127(+) to detect regulatory T cells is a simple, reproductive and accurate method, and the CD4(+) CD25(+) CD127(+) T cells can better reflect the proportion of CD4(+)CD25(+) regulatory T cells. The increase of regulatory T cells and decrease of NK cells in pediatric patients with acute leukemia indicate that the function of NK cells may be depressed. Treg T cells play a role in occurrence and development of leukemia, and are involved in down-regulating NK cell function.

[Preliminary study on the safety and pharmacodynamic action of low dose L-asparaginase].

OBJECTIVE: To investigate the safety and therapeutic effect of low dose (1000 U/m(2)) L-asparaginase (L-Asp) in the treatment of children with acute lymphoblastic leukemia (ALL). METHODS: Six patients were treated with low dose L-Asp after previously suffered severe side effects from standard dose L-Asp (5000 - 10,000 U/m(2)). Twenty-eight blood samples were obtained randomly from 5 of them. Plasma asparagine concentration was detected by reverse phase-high performance liquid chromatography (RP-HPLC). RESULTS: All the patients treated with low dose L-Asp showed no any toxic symptoms. The plasma asparagine levels in the patients were all above 5 micromol/L except case 4 (4.91 micromol/L) before receiving L-Asp, and were all decreased below 0.5 micromol/L five days after receiving low dose L-Asp, except case 3 (3.70 micromol/L), the results being like that of receiving standard dose L-Asp. CONCLUSION: Low dose L-Asp has definite efficacy for childhood ALL, while avoids serious side effects from standard dose L-Asp.

[Research on the pharmacokinetics and pharmacodynamics of L-asparaginase during its treatment of childhood acute lymphoblastic leukemia].

OBJECTIVE: To investigate the changes in the activity of Escherichia coli asparaginase (L-asp) and the concentration of asparagines (ASN) in the plasma of the acute lymphoblastic leukemia (ALL) children receiving L-asp containing chemotherapeutic protocol to explore more reasonable usage of L-asp in the treatment of childhood ALL. METHODS: L-asp containing hemotherapy regimen of VDLP was used, in which L-asp (10,000 U/m(2)) was administered intravenously every other day for 10 doses in 15 children with ALL. A total of 340 peripheral blood samples were collected at scheduled time points during the therapy and plasma L-asp activity (by spectrophotometric assay) and asparagines concentration (by RP-HPLC) were measured. RESULTS: During the administration of L-asp, the plasma L-asp activity was increasing gradually peaked after eight doses and then decreased gradually, while the plasma concentration of asparagines maintained in complete or nearly complete depletion status. After the therapy courses finished, a plasma L-asp activity above 100 U/L with asparagines almost complete depletion status was lasting for about seven days. CONCLUSION: The current L-asp containing chemotherapeutic protocols in which L-asp was administered in a dose of 10 000/m(2) intravenously every other day, are efficient enough for the depletion of plasma ASN.