[Characteristics and monitoring of minimal residual disease in patients with T acute lymphoid leukemia by flow cytometry with two 4-color combinations of fluorescent antibodies].

The purpose of this study was to establish a method for the monitoring of minimal residual disease (MRD) in bone marrow samples of the children with T acute lymphoid leukemia (T-ALL), and to evaluate its value in clinical application. The immuno-phenotype of the leukemic cells were detected by flow cytometry with two sets of 4-color combinations of antibodies against TdT/CD5/cCD3/HLA-DR(+)CD19(+)CD33 and CD34/CD5/cCD3/HLA-DR(+)CD19(+)CD33 in 32 cases of de novo T-ALL and were compared with the results in 10 normal controls. The antibody combination in regions of the two-parameter plots where the leukemic cells appeared were different from the normal cells was screened as the effective combination which was used to monitor MRD in the bone marrows of the T-ALL children after the inductive treatment. The results indicated that the respective effective frequencies of antibodies against TdT/CD5/cCD3/HLA-DR(+)CD19(+)CD33 and CD34/CD5/cCD3/HLA-DR(+)CD19(+)CD33 were 90.6% and 62.5%. 32 cases of childhood T-ALL were successively screened for antibodies combinations of interest and were identified in 100% (32/32) of these cases. After inductive treatment, the positive rate in 129 times of MRD monitoring was 19.4% (25/129) by flow cytometry and 5.43% (7/129) by FAB morphology. It is concluded that monitoring MRD in patients with T-ALL by flow cytometry with two 4 color combinations of fluorescent antibodies is an quick and effective method. The sensitivity of this method is high and it may be of important significance for the treatment and prognostic evaluation in childhood T-ALL.

[Relationship between asparagine synthetase expression level and cell sensitivity to L-asparaginase in human leukemic cell lines].

This study was purposed to explore the relationship between asparagine synthetase (AsnS) mRNA expression level and the sensitivity of leukemic cell lines to L-asparaginase. The AsnS mRNA expression level in 8 cell lines (Jurkat, HL-60, U937, NB4, THP-1, Namalwa, Karpas299 and K562) was determined by real-time quantitative PCR (RQ-PCR) based on fluorescence dye Eva Green before and after treatment with L-Asp, and the cell proliferation rates were analyzed by CCK-8 assay. The results showed that there was a significant disparity of AsnS expression level in 8 cell lines, and there were significant increases of AsnS expression level in cells co-cultured with L-Asp (p < 0.05). Of all these eight cell lines, cells sensitive to L-asparaginase had lower AsnS expression level and cells resistant to L-asparaginase had higher AsnS expression. U937 which was the most sensitive to L-asparaginase had the lowest AsnS expression level, while K562 was natural resistant to L-asparaginase and possessed of the highest AsnS level. It is concluded that the AsnS plays a critical role in regulating cellular biological behavior after depletion of asparagine, the AsnS mRNA expression level in cells reflects the sensitivity of cells to L-Asp. The results may imply the possibility for the use of L-asparaginase in leukemia with lower AsnS expression level.

[Long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2-strain)-a study on the result of 15 years' follow up].

OBJECTIVE: To evaluate the long-term immunogenicity and effectiveness of live attenuated hepatitis A (HA) vaccine (H2 strain) after one dose injection, through a 15 years' follow up observation. METHODS: A total of 220 children with negative anti-HAV antibody (aged 1-3 y) were involved and followed up in Jiaojiang district, Taizhou city, Zhejiang province. Indicators would include seroconversion and geometric mean titer (GMT) levels after inoculation the vaccine with single dose at 2 m, 12 m, 6 years, 10 years and 15 years. Epidemiological observation was carried out within the 15 years to evaluate the relationship between vaccine coverage, the incidence of HA and the overall effectiveness. In the studied population, serum was tested by ELISA (calibrated by WHO international reference) and ABBOTT Axsym HAVAB mEIA. RESULTS: Seroconversion rates were found to be 98.6% and 81.3% after 2 months and 15 years of inoculation and slowly decreased. GMT level was 128 mIU/ml after 15 years, significantly higher than the required protective level of 20 mIU/ml, recommended by WHO experts. Effectiveness through the 15-year follow up program showed a significant correlation between vaccine coverage and incidence of HA in 1-15 years aged group (Kendall-Rank test, τ =-0.931, P<0.01). There was no HA case seen among the observed accumulated 236 413 person-year vaccines, compared to 4 HA cases discovered in the 27 206 person-year of the non-vaccinees. The overall protective rate reached 100%. Through a mass vaccination program on children, the whole population established an immune-defence to enable the incidence of HA decreased by 96.7%. CONCLUSION: The long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2 strain) after one dose injection could last as long as 15 years.

[Relationship between immunological characteristics and prognosis in children with acute myeloid leukemia].

OBJECTIVE: The prognostic significance of immunophenotyping in acute myeloid leukemia (AML) has been controversial. This study investigated the relationship of immunophenotypes with French-American-British (FAB) subtypes and chromosomal abnormalities and assessed the prognostic value of immunophenotyping in children with AML. METHODS: From January 1998 to May 2003, 75 children with newly diagnosed AML were enrolled on protocol AML-XH-99. Immunophenotypes were measured with the flow cytometry. According to the McAbs used, the patients were classified into five groups: panmyeloid antigens (CD13, CD33, and MPO), myeloid-lineage associated antigens (CD14, CD15), lineage-specific antigens (CD41, GlyA), progenitor-associated antigens (CD34, HLA-DR) and lymphoid-associated antigens (CD19, CD7). The probability of event-free survival (EFS) was estimated by Kaplan-Meier analysis. The distributions of EFS were compared using the log-rank test. Chi-square analysis or Fisher exact test was used to compare the differences in the distribution of biologic presenting features. A Cox proportional hazards model was used to identify independent prognostic factors. RESULTS: At least one of panmyeloid antigens CD13, CD33 and MPO was expressed in 72 patents (97.3%). Two or more panmyeloid antigens were expressed in 45 patients (60.8%). The proportion of children with AML expressing one or more of the lymphoid-associated antigens was 24.3%. Lymphoid-associated antigen CD19 was expressed by blast cells in most of FAB M2 patients. The patients with acute promyelocytic leukemia were characterized by the absence of HLA-DR and lymphoid-associated antigens CD19 and CD7. Monovariate analysis showed immunophenotypes were not related to the complete remission rate after the first induction course and the 5-year-EFS. Multivariate analysis suggested immunophenotyping had no independent prognostic value in AML. CONCLUSIONS: Immunophenotyping can not be used independently in the evaluation of risk classification in children with AML. However, it is useful in the reorganization of special types of AML.

[Tandem application of flow cytometry and polymerase chain reaction for choice targets of minimal residual disease in childhood acute lymphoblastic leukemia].

OBJECTIVE: Minimal residual disease (MRD) is one of the most important prognostic factors in childhood acute lymphoblastic leukemia (ALL). Flow cytometry and PCR are two common techniques for examining MRD in ALL. This study aimed to identify MRD targets by tandem application of both techniques in children with ALL. METHODS: From September 2001 to October 2003, 126 children with newly diagnosed ALL were enrolled on the treatment protocol ALL-XH-99. Tandem application of flow cytometry and PCR was performed to identify MRD targets in these patients. RESULTS: 1. Using sets of combined antibodies, immunophenotypic expression of leukemia cells was observed in 95 of 106 B-lineage ALL cases (89.6%). Only one aberrant immunophenotype was observed in 11 cases (11.6%) and most patients with B-lineage ALL (88.4%) expressed at least two suitable targets. 2. Using PCR technique, T-cell receptor (TCR) or immunoglobulin gene rearrangements were identified in 26 of 27 patients (96.3%). Two or more monoclonal/ bi-allelic gene rearrangements were identified in 17 cases (65.4%). The majority (70%) of T-lineage ALL cases contained TCRVgammaI-Jgamma1.3/2.3. Cross-lineage TCR rearrangements were found in 57.1% of cases with B-lineage ALL. 3. Suitable MRD targets of immunophenotypic abnormalities or antigen receptor gene rearrangements were detected in 121 patients (96.0%). CONCLUSIONS: MRD targets were identified using tandem application of flow cytometry and PCR in almost of children with ALL. Cross-lineage TCR rearrangements and bi-allelic gene rearrangements were observed in many patients.

[Prognostic value of early treatment response in children with acute lymphoblastic leukemia: a single institution experience in Shanghai, China].

OBJECTIVE: Early response to therapy is one of the most important prognostic factors in childhood acute lymphoblastic leukemia (ALL). This study aimed to assess the prognostic value of morphological assessment of bone marrow blasts during remission induction and determination of minimal residual disease (MRD) after remission induction. METHODS: From January 1998 to May 2003, 193 children with newly diagnosed ALL were enrolled on the ALL-XH-99 protocol. Blast cell count in the bone marrow was examined on day 19 of remission induction and by the completion of remission induction. MRD was measured with the flow cytometry. Event-free survival (EFS) was estimated by Kaplan-Meier analysis and the distributions of EFS were compared using the log-rank test. A Cox proportional hazards model was used to identify independent prognostic factors. RESULTS: The 4-year EFS was significantly worse in patients with > or = 5% lymphoblasts in the bone marrow on day 19 as compared to those with <5% lymphoblasts on that date (42.59%+/- 14.28% vs 74.24%+/- 6.67%; p< 0.01). The 4-year EFS was significantly worse in patients with any amount of lymphoblasts in the bone marrow on the remission date as compared to that of other patients with no morphologically identifiable blasts (63.47%+/-9.23% vs 76.41%+/- 6.09%; p<0.05). The patients with MRD <0.01 had significantly better outcome than those with a level > or = 0.01% (15-month EFS:94.44%+/-5.40% vs 23.81%+/- 20.26%; p<0.01). CONCLUSIONS: Early treatment response as assessed by morphological examination or minimal residual leukemia determination by flow cytometry has important prognostic significance, and can be performed in a resource-poor patient population.

[Effect of pax5 gene blocked by RNAi on biological characteristics of B cell malignant lymphoma].

This study was aimed to investigate the biological characteristics of B hematological tumor cells such as proliferation, immunological phenotype and apoptosis by silencing pax5. The specific pax5 small hairpin RNA (shRNA) was synthesized by in vitro transcription. For evaluating the inhibition efficiency, the expression change at mRNA and protein levels were assessed by real-time RT-PCR and Western blot respectively. To detect the biological characteristics of pax5-silenced hematological tumor cells, the immunological phenotype, apoptosis and cell proliferation were measured by using real-time RT-PCR, MTT assay and flow cytometry respectively. The results showed that two shRNA were synthesized, both of which were effective to block pax5 expression. After being blocked by RNAi the immunological phenotype of pax5-silenced lymphoma cells was changed, the expressions of CD19 mRNA and protein were reduced, but the expression of IgM was not changed. As compared with control group, the effect on proliferation and apoptosis of lymphoma cells not could be detected after pax5 silencing. It is concluded that the pax5 plays important role in late differentiation of B cells, and may participate in signal transduction of lymphoma cells, but the effect on proliferation and apoptosis of lymphoma cells were not detected after RNAi, which need to be elucidated further.

[Clinical importance of minimal residual disease testing in the therapy of childhood B-cell acute lymphoblastic leukemia].

OBJECTIVE: To study the role of minimal residual disease (MRD) in the evaluation of therapeutic effectiveness of childhood B-cell acute lymphoblastic leukemia (ALL). METHODS: MRD testing was performed in 124 children with B-cell ALL, who were newly diagnosed and enrolled in the ALL-XH-99 treatment protocol from September 2001 to April 2005MRD was determined by 4-color flow cytometry in the different time points during the treatment period. RESULTS: After induction therapy, 103, 13 and 8 patients showed MRD <0.01%, 0.01%-0.1% and >0.1%, respectively. The 5-year relapse-free survival (RFS) in the patients with MRD <0.01%, 0.01%-0.1% and >0.1% was 88.9+/-3.9%, 70.0+/-14.5% and 0%, respectively and the 5-year event-free survival (EFS) was 82.4+/-4.4%, 21.2+/-18.0% and 0%, respectively. There were significant differences in the RFS and EFS among the patients with different MRD levels (P<0.01). Within half a year after induction remission, the 5-year RFS in patients with MRD negative (<0.01%) and positive was 87.7+/-4.1% and 58.3+/-14.2%, respectively (P<0.01) and the 5-year RFS was 80.7+/-4.6% and 25.6+/-13.8%, respectively (P<0.01). After half a year with induction remission, the patients with MRD negative and positive also showed statistical differences in the 5-year RFS (92.0+/-3.6% vs 48.5+/-15.5%; P<0.01) and EFS (85.6+/-4.5% vs 21.4+/-11.0%; P<0.01). Multivariate analysis confirmed that the MRD level after induction chemotherapy together with the reaction to prednisone, the bone marrow features on the 19th day of induction, and the fusion gene with BCR-ABL or MLL-AF4 had prognostic significance in childhood B-cell ALL. CONCLUSIONS: The MRD level in the whole course of therapy is an important outcome indicator in childhood B cell ALL.

Prognostic influence of minimal residual disease detected by flow cytometry and peripheral blood stem cell transplantation by CD34+ selection in childhood advanced neuroblastoma.

OBJECTIVE: To determine whether neuroblastoma (NB) minimal residual disease (MRD) in bone marrow (BM) detected by flow cytometry could predict prognosis and whether tumor cell purging by CD34(+) cell selection prior to transplantation will impact on disease-free survival. METHODS: NB MRD in BM was evaluated by flow cytometry with CD45-FITC-/CD81-PE+/CD56-PECy5+ monoclonal antibodies cocktail. Peripheral blood stem cell (PBSC) was enriched via positive CD34(+) cell selection by magnetic-activated cell separation system (MACS). RESULTS: Eleven of 31 patients with CD45(-)/CD81+/CD56+ cells by flow cytometry at diagnosis became negative after an average of four courses of chemotherapy. All 11 patients remained alive without evidence of disease. Thirteen of the 20 patients with positive MRD relapsed and 1 patient died from disease (mean 25.8 months). There was a significant difference between these two groups. MRD in BM was tested before PBSC transplantation (PBSCT) for 19 NB patients. Fourteen was negative, 4 of them relapsed and 10 patients remained alive without evidence of disease. Another 5 patients with positive MRD, all of them relapsed (mean 17 months after PBSCT) with a significant difference between these two groups. Fourteen of 19 PBSC were purged with CD34(+) selection procedure. Six of 14 relapsed (mean 18.43 months after PBSCT). Five patients did not purge for CD34(+) selection, and 3 of them relapsed with no significant difference between these two groups. CONCLUSIONS: Positive MRD in BM after an average of four courses of chemotherapy and before PBSCT is an unfavorable factor for stage IV NB. CD34(+) selection purging for PBSCT may not improve the prognosis for children with neuroblastoma in advanced stage.

[Expression of retinoblastoma protein in child acute leukemia cells and its clinical significance].

The research was aimed to detect the expression levels of retinoblastoma protein (pRb) in child acute leukemia cells, and to explore its possible association with leukemia cells cycle, the risk of disease, minimal residual disease (MRD) monitoring and prognosis of B-ALL. Flow cytometry (FCM) was used to detect the expression of pRb in 89 cases of acute leukemia (including 25 AML, 10 T-ALL and 54 B-ALL) and bone marrows from 7 normal children (control group). Meanwhile the cell cycle in some cases was analyzed. The results showed that (1) the FCM could accurately detect the expression of pRb in acute leukemia cells; (2) the high level of pRb expression was frequent in all types of child acute leukemias. In the same case, the expression of pRb was significantly increased in leukemia cells when compared with non-leukemia cells. And no detectable pRb protein was found in partial cases of acute leukemia; (3) there was a close relation between expression of pRb and the cell cycle of leukemia cells, the number of G(1) phase cells in pRb positive case of B-ALL was more than that in pRb negative case (92% vs 77%); (4) in B-ALL, the level of pRb expression in MRD positive group was significantly lower than that in MRD negative group (P < 0.05), but pRb expression was stable in non-leukemia cells during therapy; (5) pRb expression was related to the early response to therapy in B-ALL, the expression of pRb was significantly increased in sensitive group when compared with insensitive group (P < 0.05). It is concluded that high level or absence of pRb expression can be found in child acute leukemia cells. The expression of pRb is positively related to cell cycle of leukemia cells, MRD monitoring and the early response to therapy. In short, the detection of pRb expression level can guide the therapy and the evaluation of prognosis in B-ALL.

[Prognostic value of minimal residual disease in childhood B-cell acute lymphoblastic leukemia].

OBJECTIVE: To assess the prognostic value of minimal residual disease (MRD) in childhood B-cell acute lymphoblastic leukemia (ALL) after induction chemotherapy. METHODS: From September 2001 to October 2004, 102 patients with newly diagnosed B-ALL were enrolled in protocol ALL-XH-99. MRD after induction therapy, before high-dose methotrexate and early intensification as well as at 1 year and 2 year maintenance therapy was detected by multiparameter-flow-cytometry (MP-FCM). RESULTS: (1) The probability of 39-month event-free survival (EFS) for patients with a level of MRD < 10(-4), was significantly higher than for those with a higher MRD [(83.00 +/- 9.90)% vs 0.00%, P < 0.01]. (2) Univariate analysis indicated that the MRD level at achieving complete remission (CR) had no relationship with the biologic features at presentation (gender, age, white blood cells and cytogenetic abnormalities), but did with Philadelphia chromosome, the time reaching CR, ALL-XH-99 risk group and lymphoblasts in bone marrow on day 19 after induction therapy (P < 0.05). (3) Multivariate analysis suggested that MRD level after the first induction course was an independent prognostic factor (hazard ratio, 5.381; 95% CI 0.004 to 0.624; P < 0.05). CONCLUSION: The MRD level at achieving CR is one of important prognostic factor in the treatment of childhood B-cell ALL, and might be used to assess the early treatment response.

Persistent efficacy of live attenuated hepatitis A vaccine (H2-strain) after a mass vaccination program.

BACKGROUND: Live attenuated hepatitis A vaccine (H2 strain) is widely applied in prevention of hepatitis A epidemic in China and other countries now. It is essential to observe and confirm the vaccine immune efficacy, population antibody level and its persistent efficacy after mass immunization. METHODS: A total of 220 children with negative anti-HAV antibody (aged 1 - 3 years) were taken for follow-up assay to observe seroconversion and geometric mean titre (GMT) level 2 months, 12 months, 6 years, and 10 years after inoculation. Another survey sampled from subjects of different age groups (3, 6, 9, 15, 18, 25 and 35 years) to compare anti-HA antibody positive rate before and after inoculation performed 10 years previously. Epidemiological observations were taken for 10 years to evaluate the relationship between vaccine coverage and hepatitis A morbidity. Serum antibody to HAV was detected by enzyme linked immunoassay (ELISA, calibrated by WHO international reference) and ABBOTT Axsym HAVAB microparticle enzyme immunoassay. RESULTS: Seroconversion in follow-up assay 2 months and 10 years after inoculation was 98.6% and 80.2% respectively. For children, the vaccination anti-HA antibody positive rates were significantly different before and after 10 years, 7.69% cf 70.45% (aged 3 years) and 52.58% cf 71.78% (aged 18 years). When vaccine coverage rose from 57% to 74%, there were no any HA epidemics. When vaccine coverage reached 85%, there were no any HA cases. With vaccine coverage between 85% and 91%, there were no any HA cases in cohorts from the age of 1 year to 15 years during the 10 years. CONCLUSIONS: Live attenuated hepatitis A vaccine has an obvious long-term effectiveness in prevention and control of HA epidemics through mass vaccination.

[Apoptosis mechanism in human chronic myelogenous leukemia K562 cells induced by tetra-arsenic tetra-sulfide].

To explore the effects of tetra-arsenic tetra-sulfide (As(4)S(4)) in treatment of human chronic myelogenous leukemia K562 cells and its mechanism, trypan blue staining and microculture MTS assay were used to measure the effects of As(4)S(4) on growth inhibition of K562 cells; the morphologic change was determined by Wright's staining assay. The apoptosis rate and cell cycle were detected by flow cytometry; the changes of transcript and protein level were determined by real-time quantitative RT-PCR and Western blot analysis, respectively. The results indicated that As(4)S(4) had significant cytotoxicity on K562 cells. At the concentration of 0.5 micromol/L, the cell viability decreased significantly after being cultured with As(4)S(4) for 24 hours. When the concentration was lower than 0.1 micromol/L, As(4)S(4) had a little effect on K562 cells. The effect of As(4)S(4) on K562 was time- and concentration- dependent. After being cultured with As(4)S(4) at the concentration of 1.0 micromol/L for 24 to 48 hours, K562 cells displayed typical morphological changes of apoptosis. At a concentration greater than or equal to 1.0 micromol/L, As(4)S(4) could induce apoptosis significantly. After 12 hours of incubation with 1.0 micromol/L As(4)S(4), the apoptosis rate increased from (3.47 +/- 0.42)% to (6.16 +/- 0.98%). At the same time, the percentage of cells in G(1) phase decreased from (69.65 +/- 3.24)% to (50.53 +/- 2.86)%, whereas the percentage of cells in G(2)/M phase increased from (9.56 +/- 2.51)% to (12.91 +/- 2.13)%. The mRNA level of Bcl-X(L) and the protein level of pAkt were down-regulated after the inhibition of As(4)S(4), while the mRNA expression of Bcl-2, Bad and Bax had no change. Both of the transcript and protein level of bcr-abl had no change after incubation with As(4)S(4). It is concluded that As(4)S(4) can inhibit the growth of K562 cells efficiently through inducing apoptosis and cell cycle arrest. It seems that As(4)S(4) interferes with pAkt pathway and down-regulates Bcl-X(L), which may be involved in the response of K562 to this agent.

[Prognostic value of both detection of lymphoblasts in the period of early treatment and minimal residual disease in childhood acute lymphoblastic leukemia].

OBJECTIVE: To assess the prognostic value of both morphological persistent disease on day 19, on complete remission (CR) and minimal residual disease (MRD) in the bone marrow (BM) after multiagent remission induction therapy. METHODS: From January 1998 to May 2003, 193 patients with newly diagnosed ALL were enrolled on protocol of ALL-XH-99. BM blast counts on day 19 and on CR after induction therapy were examined. BM MRD at the end of induction therapy was detected by MP-FCM. RESULTS: (1) The probability of 5-year event-free survival (pEFS) was significantly worse for patients with > or = 0.050 BM lymphoblasts on day 19 than that with < 0.050 BM lymphoblasts [(42.59 +/- 14.28)% vs (74.24 +/- 6.67)%, P < 0.001]. (2) The 5-year pEFS was significantly worse for patients with a low percentage of lymphoblasts (< 0.050) in BM on CR as compared to those with no morphological persistent lymphoblasts [(63.47 +/- 9.23)% vs (76.41 +/- 6.09)%, P < 0.05]. (3) No significant difference was found in BM lymphoblasts between patients with MRD (> or = 10(-4) of nucleated bone marrow cells) and those without MRD (< 10(-4)) at the end of induction therapy (P > 0.05). The 22-month pEFS was significantly worse for patients with MRD as compared with those without MRD on CR [(23.81 +/- 20.26)% vs (94.44 +/- 5.40)%, P = 0.001]. CONCLUSIONS: BM lymphoblast > or = 0.050 on day 19 after induction therapy is an independent prognostic factor for childhood ALL; low percentage of lymphoblasts and minimal residual disease in BM on remission also do it. Patients with > or = 0.050 lymphoblast in BM on day 19 or with MRD > or = 10(-4) at the end of induction therapy should receive altered and more intensive chemotherapy.