A Study Of DLK1 Gene Expression And Its Significance In Acute Leukemia

Acute Leukemia,a group of malignant clone's diseases generating from hematopoietic stem cells,which is threatening human health significantly,have an increasing morbidity and mortality in recent years. It is also one of common malignant cancers.Multigenetic factors and many events contribute to Leukemia,the activation of oncogene and inactivation of antioncogene are involved in such process,Therefore,an understanding of the molecular pathogenesis must be very important to prevention and treatment.The DLK1 located 14q32,the full-length of it's cDNA is 1557bp and it's coding sequence(CDS) includes 1152 nucleotide which can be code 383 amino acid residue.The level of DLK1 genes are upregulation in several tumors,such as pheochromocytomas,neuroblas- tomas,small lung carcinoma,brain neurospongioma,but down- regulation in adenocarcinoma of kidney.It seems like that all the tumors which overexpress DLK1 have neuroendocrine character,but futher studies of the DLK1 expression should be performed.Objectives:To investigate the expression of DLK1 gene in acute lekeamia and the relationship between the genes and the quantity of white corpuscle and platelet,as well as the function during erythroid differentiation.To explore DLK1 gene expression and the role in acute leukemia.Methods:1.To detect the expression of DLK1 gene in different acute leukeamia categories with RT-PCR and western blotting,then analyze the relationship between its expression and the clinical feature.2.The K562 cell line was induced to erythroid differentiation by hemin,then draw-off RNA at different time point to determine DLK1 gene expression and observe the relationship between it's expression and erythroid differentiation.Results: 1.A 252bp prospective cDNA were produced from both the RNA of 65 acute leukemia cases and 34 control cases,which indicates that both leukemia cells and normal marrow cells can express DLK1.The level of DLK1 which expressed in acute leukemia cells and normal marrow cells are 0.575±0.173 and 0.488±0.160 respectively.Acute lymphoblastic leukemia cells and acute myelogenous leukemia expressed respectively 0.579±0.172 and 0.571±0.175.The expression of DLK1 in patients is higher than that of the test cases,and the significance exists between test groups and control group.(t=-2.406,P=0.018;t= -2.023,P=0.048;t=-2.146,P=0.035) while there is no significance between acute lymphoblastic leukemia and acute myelogenous leukemia (P＞0.05).2.The WBC and platelet counts from 65 acute leukemia cases were performed which indicates that the expression of DLK1 has no relation with the WBC and platelet counts statistically(P=0.120).3.Western blotting was used to detect the protein expression of DLK1 from mononuclear cells in 20 patients with acute leukemia,we found that DLK1 protein was low-expressing in 6/16 AML and 2/4 ALL patients as well as awfully low-expressing in 1/13 controls.The difference between acute leukemia and controls has statistical significance(χ~2=4.146,P=0.042).DLK1 protein expressed in K562 cells but not in HL-60 cells.4.K562 cells expressed a 252bp cDNA band of RT-PCR product that indicated DLK1 was expressed in K562 cells while HL-60 cells have no band which suggestes no expression of DLK1.To explore changes of DLK1 gene hemin-induced expression at each time point during erythroid differentiation,indicating that DLK1 mRNA decreased gradually along with K562 cells towards erythroid differentiation.Conclusions:1.DLK1 was expressed in both normal bone marrow mononuclear cells and leukemia cells,but up-regulated in acute Leukemia cells.2.DLK1 gene is involved in leukemia,but the mRNA level of DLK1 has no significance with the WBC and platelet counts in patients with acute leukemia at onset. 3.The level of DLK1 protein in leukemia cells is higher than that in the control cells,which is coincident with the mRNA expression.4.DLK1 is possibly involved in the process of erythroid differentiation of K562 cells,the present study shows it may inhibit the process.