الفهرس 
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Abstract
Acute lymphoblastic leukemia (ALL) is a heterogeneous group of lymphoid disorders that result from a monoclonal proliferation and expression of immature lymphoid cells in the bone marrow, blood and other groups. A better understanding of the biology of ALL has led to changes in the pathologic classification of the disease, the emergence of new therapies, and the institution of risk adapted therapies.
Adhesion molecule CD44 is a cell surface transmembrane glycoprotein encoded by single gene, involved in lymphocyte activation, recirculation and homing, adhesion of extracellular matrix, angiogenesis, cell proliferation, cell differentiation and cell migration as a receptor for hyaluronic acid. All these biologic prosperities are essential to the physiological activities of normal cells, but they are also associated with the pathological activities of tumor cells.
Elevated CD44 expression was correlated with poor prognosis in many malignancies, such as lung cancer, gastrointestinal, neuroendocrine tumour and so on. In recent years, scholar pay more attention to the association with CD44 and hematological malignancies.
The CD95 is a transmembrane receptor, is a member of tumour necrosis factor/nerve surface molecules, some researchers demonstrated that Fas was expressed on majority of human leukemia cells, although the intensity of expression was variable.
Physiological apoptosis can be induced by a multitude of stimulants, including withdrawal of growth factors, hormones, and activation of death receptors such as CD95. Defects in Fas-Fas ligand pathway (usually Fas but occasionally Fas germline mutations) cause autoimmune lymphoproliferative syndrome, a rare childhood disorder associated with B cell lymphomas, classic Hodgkin’s lymphoma, and nodular lymphocyte predominant Hodgkin’s lymphoma, polymorphisms in Fas or FasL. Associated with increased risk of autoimmune hepatitis, increased risk of type II diabetes.
The CD95 receptor /ligand (CD95/CD95L) system has been involved in regulation of apoptosis in several cell types. The Fas receptor contains aconserved cytosolic domain known as death domain that is responsible for recruiting adaptor proteins such as FADD (Fas associated protein and Death domain) to the receptor complex after binding of the ligand. The FADD protein binds certain caspases prodomains such as caspase-8 and -10. Processing of caspase releases the activated protease into cytosol, where it can cleave and activate other downstream procaspases.
There are many prognostic factors as age, sex, white blood cell count, the presence of mediastinal mass and central nervous system involvement at diagnosis etc. Assessment of these factors is mandatory for therapy assignment.
The present study aimed to estimate the pretreatment level of CD44 and CD95 in children with acute lymphoblastic leukemia and to evaluate their role as additional prognostic markers.
The current study was carried out on 30 newly diagnosed children with ALL and 20 apparently healthy children served as control group.