BMI-1 and the HOXA9 Gene in Children with Acute Leukemia Peripheral Blood and Their Clinical Significance
|Keywords||BMI-1 gene HOXA9 gene children acute leukemia RT-PCR|
Leukemia is a malignant disease of hematopoietic system, which is one of the top ten high incidence of malignant tumors, characterized by a certain type of hematopoietic tissue cells in the bone marrow of leukemia or other blood-forming tissue in the incidence of malignant hyperplasia,and infiltration in vivo every organs, organizations, leading to normal hematopoietic cells being inhibited, resulting in a variety of symptoms. Acute leukemia is a blood disease in acute and danger severe case for some cases because of resistance to chemotherapy,results are poor, many complications those who comparatively are poor prognosis.With the development and progress of medicine, acute leukemia treatment level has also been greatly improved, and an active preventive treatment for complications and improving the body’s resistance to diseases, can save patient’s life. Methods of treatment of leukemia chemotherapy, combines Chinese and Western medicine treatment, bone marrow transplant, bio-regulators and so on, and the present field of gene therapy for leukemia research, one of the difficult and hot. Leukemia patients in China is about 3～4/10 million people, childhood ’s malignant tumor is the highest incidence of leukemia. Because of the pathogenesis of leukemia has not yet entirely clear, troubled by the clinical treatment, thus to clarify the pathogenesis of leukemia, to further study the effectiveness of genes in the pathogenesis of leukemia in children, to utilize genes to achieve goals of treatment is a new way.Proto-oncogene BMI-1 (B-cell specific moloney leukemia virus insertion site 1, BMI-1) belongs to PcG (Polycomb group, PcG) family of PRCI composite system, together with other PcG proteins through the formation of multi-protein complexes involved in homeobox(homobox,HOX)gene transcription regulation, the maintenance of HOX the inhibitory state. HOX orientation in determining cell differentiation and proliferation, regulation of body tissues and organs and development play a decisive role.BMI-1 gene expression in abnormal expression lead to HOX gene inhibition or activation abnormalities, affecting the normal function of HOX genes play. Epigenetic PcG-mediated gene silencing is a local event, does not affect a broader range of chromatin regions. regulating gene expression in the central link is the BMI-1, the other PcG proteins has little effect.. Research suggests that PcG family of the BMI-1 and Ring1B is core subunits in PRC1 complex and the complex regulate HOX gene expression, X chromosome inactivation, tumorigenesis and stem cell self-renewal, to play an important role. More and more evidences suggest that, HOX genes in leukemia formation has played an important role. HOX family genes are divided into two broad categories:HOX genes and non-HOX genes. HOX family of HOXA9, HOXA10, HOXB3, HOXB4, HOXB6 in a number of acute myeloid leukemia (AML) can be detected frequently in patients with high levels of expression. HOXA9 expression in AML is more common.In addition to FAB classification of M3 type AML things are highly expressed and chronic myeloegenous leukemia. (CML) and myelodysplastic syndrome-primitive cells increased type (MDS-RAEB) also has expressed. In the 24 leukemia cell lines,eight myeloid leukemia cell lines except HL60, TMM can be detected the HOXA9 expression, HOXA9 in mouse bone marrow cells in the unrestricted expression of 3 to 10 months, will inevitably lead to the occurrence of leukemia.To hint that AML have occurred prior to genetic changes.BMI-1 gene can maintain the stem cell pool.It is one of necessary self-renewal genes for adult stem cells and leukemia stem cells, as a cancer-causing gene, BMI-1 closely correlate the development of hematopoietic malignancies and solid tumors of the genesis. BMI-1 gene is expected to be one of new indicators of progress for cancer diagnosis,disease assessment,and judge the prognosis of patients with malignant tumors.BMI-1 is highly specific static son of HOX gene,and BMI-1 gene introducted into lymphocytic leukemia or lymphoma cells,which can down-regulate HOX target genes in lymphoid progenitor cells.In recent years,the study found that BMI-1 and/or HOX highly expressed in a variety of tumors, suggesting that BMI-1/HOX may have a high potential value in the study of directions of pathogenesis and treatment and so on. BMI-1, as a cancer gene abnormally expressed in a variety of tumors, along with the progress of research into gene therapy in the future gene therapy of human tumors widelly used. It is envisaged that BMI-1 gene and/or HOX genes will be increased and/or missinged, as a target for the treatment of leukemia caused by the upstream or downstream from the genetic changes. But at present after the, There is little study of concerning HOX genes change caused by BMI-1 in tumor cells over-expression or reducing.Thus the experiment is designed to observe the BMI-1mRNA, HOXA9mRNA in children with leukemia and healthy children peripheral blood expressed in order to explore the expression of these two genes and the possible relevance of their interaction, to further explore the pathogenesis of leukemia and provide clues to gene therapy for leukemia.Objective1. To observe BMI-1 and the HOXA9 gene expression in children with acute leukemia (acute leukemia, AL) peripheral blood, and explore the clinical significance of the expression of these two genes in the AL.2. To explore the possible correlation of the BMI-1 and the HOXA9 gene in the AL peripheral blood.3. To explore the pathogenesis of leukemia, and provide clues to gene therapy for leukemia. Materials and methodsIn June 2008 to June 2009 in the Third Affiliated Hospital of Zhengzhou University and other hospitals, Zhengzhou City, diagnosis and treatment for children with acute leukemia and good health children peripheral blood are collected as samples. Combined with chemotherapy in newly diagnosed patients by the 19th day review to determine whether the bone marrow complete remission (CR). The diagnosis, CR and relapse criteria for judging are in line with the Chinese Medical Association 2006 revised diagnostic criteria of acute leukemia. Children with acute leukemia specimens of 57 cases, male to female ratio of 35:22 (1.59:1), aged 3 months to 14 years old, with a median age of 5 years old. With acute lymphoblastic leukemia (ALL) 38 cases (B-type 27 cases; T-type 11 cases), acute myeloid leukemia (AML) 19 cases (M1 3 cases, M2 5 cases; M3 6 cases; M4 2 cases; M5 3 cases), the diagnosis is confirmed after bone marrow cell morphology, flow cytometry, immunophenotype, chromosomes. By age 3 months to 12 years old, with a median age of 6 years of good health 30 cases of children in the control group, male (18 cases):female (12 cases) ratio:(1.50:1). Of all age groups, sex difference was not statistically significant. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) method is used to detect 30 cases of good health of children and 57 cases of childhood AL in patients with BMI-1 and HOXA9 gene expression and to track follow-up of the above-mentioned gene positive and negative patients with remission rates and survival. SPSS 13.0 statistical software is used for analysis, all the raw data are for normal distribution and test of homogeneity of variance. Experimental data indicate by x±s comparision of a variety of the mean is with the single-factor analysis of variance, correlation analysis uses linear correlation pearson analysis, a=0.05 level for the test.Results1. The level of BMI-1/HOXA9 gene’expression in children with acute leukemia peripheral blood was significantly higher than that of control group (p<0.05).2. We found part of the BMI-1 gene expression or weak expression in children with myelogenous leukemia peripheral blood, while universal expression was found in various types of B-lymphocytic leukemia, and higher than that in myelocytic leukemia group (p<0.05).3.The children in the HOXA9 gene expression in acute myeloid leukemia peripheral blood is more common, HOXA9 mRNA expression was significantly higher than in children with acute lymphoblastic leukemia patients,the comparision of the two statistically significant (P<0.01).4. The level of expression in chemotherapy non-remission groups was higher than that in remission group, but the difference was not statistically significant(p>0.05).After complete remission,BMI-1mRNA/HOXA9 mRNA were not detected in the two groups;Compared with the complete remission group,expression of BMI-1mRNA/HOXA9 mRNA in the untreated group and the recurrence group was significantly higher (p<0.05);and expression of BMI-1mRNA/HOXA9 mRNA in the former two was significantly different from that in the control group(p<0.05);while there was no significant difference between the complete remission group and the control group(p>0.05).5. In the research,to track follow-up of remission rates and survival of the above-mentioned gene positive and negative patients.we observed 23 cases children with acute leukemia specimens of 57 ones, remission ratio is 0.85 (19/23).HOXA9 gene expression these whose level was carry out a variable linear correlation analysis. results suggest that clinical outcomes/survival and HOXA9mRNA expression was negatively correlated.concerned with tumor cell load,high level expression those who were most poor clinical outcomes and prognosis, the expression levels of HOXA9mRNA were significantly inversely correlated with clinical outcomes and survival(r=-0.857,P<0.01).6. The levels of BMI-1 and HOXA9 gene’expression in children with acute leukemia was carry out a variable linear correlation analysis, results suggest that BMI-1 and HOXA9 mRNA expression was negatively correlated, The higher expression level of BMI-1mRNA, the lower expression levels of HOXA9mRNA;on the contrary BMI-1mRNA reduce the level of expression, HOXA9mRNA increased expression levels. The correlation coefficient r=-0.667,by t test P<0.01. Conclusion1. BMI-1 gene has a lymphoid lineage-specific,HOXA9 has a myeloid lineage-specific, can serve as a distinction between lymphoblastic leukemia and myelogenous leukemia one of gene symbol.2. BMI-1 gene and HOXA9 gene may be used as one of indicators of the incidence of children with acute leukemia, relapse and treatment and prognosis.3.The HOXA9 expression level is related to tumor cell burden,the higher levels of expression, the poor treatment and prognosis poor.4. BMI-1 and HOXA9 expression levels have significantly negative correlation between the two.