Study On Expression Of Notch Gene And Its Role Of Anti-apoptosis And Drug-resistance Of Cells In Chronic Lymphocytic Leukemia

Background：Chronic lymphocytic leukemia (CLL), a kind of B indolentlymphocyte tumor, is more common in older adults in western countries. Although theincidence of CLL is obviously lower in China, it’s increasing yearly with ourcountry’s big popuation base，the coming of aging society and the increasing level ofdiagnosis. CLL is still an incurable disease at present. Studies had found that Notchsignaling pathway was involved in the cells’ survival, anti-apoptosis anddrug-resistance in CLL, while its concrete mechanism has not been fully elucidated.So study on the pathogenesis of CLL, especially the drug-resistant mechanism forexploring novel targeted therapy has an important clinical significance.Objective： Aimed to investigate Notch gene’s expression in chroniclymphocytic leukemia cells and to research the change of Notch gene after the therapywith cytosine arabinoside or dexmethasone, then to explore the mechanism of Notchmediated anti-apoptosis and drug-resistance in chronic lymphocytic leukemia cells.Methods: The mononuclear cells from bone marrow or peripheral blood ofchronic lymphocytic leukemia patients (12cases), acute leukemia patients (12cases)and healthy donors (8cases) were collected, then the expression of Notch molecularwas detected by flow cytometry (FCM) respectively; The mononuclear cells frombone marrow or peripheral blood of chronic lymphocytic leukemia patients (24cases),and healthy donors (14cases) were collected,then the expression of Notch gene, Bcl-2,as well as NF-κB gene were detected respectively by real-time fluorescentquantitative PCR (qRT-PCR) at the level of transcription. Investigating the change ofNotch molecule at the level of mRNA or protein in L1210cell lines after therapy withcytosine arabinoside and dexmethasone, was performed by qRT-PCR and Westernblot assay respectively. Results:1.Compared with control group, there is no significant difference in theexpression of Notch molecule on the surface of cells of CLL or AL groups;2.TheNotch1, Notch2, Bcl-2and NF-κB gene at the level of mRNA of CLL group aresignificantly higher than healthy control group (0.8556±0.8726vs.0.6731±0.5334,P=0.0182;1.2273±0.8207vs.0.6577±0.6424, P﹤0.0001;8.0960±7.5661vs.0.5969±0.4976, P﹤0.0001;1.0966±0.6925vs.0.5373±0.7180, P﹤0.0001,respectively), but no significant difference were found between Notch3and Notch4gene;3.The changes of expression of Notch and NF-κB gene at the level oftranscription had not been observed with the therapy of cytosine arabinoside anddexmethasone in L1210cell lines;4.Notch1protein were significantly decreased after24h treatment with low concentration of cytosine arabinoside in L1210cell lines, butincreased with a high concentration and with time-dependent pattern in the lowconcentration of cytosine arabinoside; Notch1protein were significantly decreasedafter24h treatment with dexmethasone in L1210cell lines, but it did not depend ondrug concentration and action time.Conclusion:1. The expression of Notch gene at the level of transcription ishigher in Chronic lymphocytic leukemia cells than that in normal cells.2. Notch1protein is downregulated in the process of apoptosis mediated by the cytosinearabinoside or dexmethasone. Thus, Notch molecule maybe play an important role inthe anti-apoptosis and drug-resistance of chronic lymphocytic leukemia cells.