Expression Of Death Receptor In Leukemia Cells And Its Clinical Significance And The Synergistic Apoptosis-induction Roles Of RhTRAIL And Arac In HL-60 Cells

Widely existent cell apoptosis has played important biological roles in prophylaxis of diseases, especially blocking the forming of malignancy. Apoptosis is governed by a plethora of relevant genes and gene products that either dictate cell death or prolong cell survival. A great deal of studies of apoptosis relevant genes have step by step illustrated the corrlationship between apoptosis and tumor occurrence, and have initiated the new field on the study of tumor induced apoptosis. Recent attention has been focused on function and significance of an important apoptosis-inducing factor named TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and its receptors. TRAIL is a potent death gene that favours the killing of various types of cancer cells, but not in most normall cells. Like FasL, TRAIL is a member of the TNF family with significant similarity to FasL. Members of the TNF family have similar biological actions, including T cell co-stimulation, induction of B cell proliferation and differentiation, and macrophase activation. Apoptosis inducing rule of TRAIL appears to act via its receptors that is distinct from FasL/Fas, TNFnT>JFR, suggesting that its biological role is better than the other two. TRAIL and its receptors have participated in physiological and pathological process of hematopoietic origin. The expressions of death receptor 4 and 5 in hematopoiesis have participated in adjusting the cell renovation in right-5-conditions. The expression and abnormity function have relationship with the tumor proliferation under pathological conditions, such as Leukemia. To think highly of the relationship of TRAIL and its receptors, there were reports about apoptosis-induction of TRAIL and its receptors in some tumors, but the actions have not been reported in acute leukemia.In the first part of present work, acute leukemia cell lines HL-60, Jurkat, NB4 and K562 cells, as well as bone marrow specimens from 20 patients with acute nonlymphocytic leukemia (ANLL) were used. We examined the expression rate of DR4 and DR5 positive cells by using immunocytochemistry, observed its relationship with that the percents of leukemia cells in bone marrow from 20 patients before chemotherapy, and the complete remission rate after chemotherapy in ANLL; In the second part, leukemia cell line HL-60 cells were used. Four internationally accepted criteria for monitoring apoptosis were adopted, including trypan blue test, MTT assays, transmission electron microscopic examination of morphology and ultrastructural changes, agarose gel DNA electrophoresis for detection of DNA Ladder, and fluorescence-activated cell sorter (FACS) to explore the mechanisms of apoptosis recombinant human (rh) TRAIL, and synergistic apoptosis-induction roles of combination of chemotherapeutic agent AraC with rhTRAEL in ANLL cells. The results were as follows:(1) The positive expression rates of DR4 and DR5 were higher in HL-60, Jurkat and NB4 cells, and relatively lower in K562 cells. The expressions were located mainly in cell membrane and cytoplasm.(2) The expression of DR4 and DR5 were different obviously in 20 patients of ANLL, and the positive rates were negatively related with the percents of leukemia cells before chemotherapy, and the rates were related with the rates of complete remission after chemotherapy in ANLL, and the positive rates was not significantly correlated with clinical types of ANLL.The positive rate of the lesion groups was-6-lower than that of normal control groups.(3) RhTRAIL could trigger apoptosis obviously of HL-60 cells. The apoptosis-induction of rhTRAIL was concentration-dependent. The optimal apoptosis-inducing concentration of rhTRAIL was lOOng/ml.(4) The synergistic apoptosis-inducing action of combination of rhTRAIL and AraC appeared significantly stronger than that of rhTRAIL alone. FACS analysis indicated that the apoptotic cells were accordingly increased with concentration incerasing in certain dose range. These results indicated tha...