الفهرس 
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Abstract
Acute myelogenous leukemia (AML) is a malignant disease of the bone marrow in which hematopoietic precursors are arrested in an early stage of development resulting in accumulation of undifferentiated and functionally heterogeneous populations of cells that interfere with the production of normal blood cells.
During normal developmental progression from stem cell to progenitor cell to mature cell, mutations may potentially occur at any point during this evolution, giving rise to a malignant entity. A mutation in a normal stem cell might give rise to a unit that could be considered as leukemic stem cells (LSCs).
LSCs initiate and sustain the clonal growth in AML. The poor response to therapy in AML patients raises the expectations that the presence of LSCs in quiescent state, resembling the normal stem cells, may add to the resistance to conventional chemotherapy. An enormous effort has been taken to identify specific surface markers in order to differentiate between normal and leukemic stem cells.
Our study aimed to assess the expression of CD96 and CD123 in leukemic stem cells and its correlation to prognosis in adult patients with acute myeloid leukemia
Using multi-color flowcytometry, we analyzed the expression of CD96, CD123 within CD34+/CD38- cells in bone marrow samples of 40 AML patients at diagnosis and at day 28 . In addition, 16 bone marrow samples from patients with non-haematological malignancies were examined as a control group.
At diagnosis, CD96 had a mean expression of 22.5% with a range falling between 2.6% and 58.3%. Whilst, CD123 mean expression was 19.4 % ranging from 0% to 54.6%.
Repetition of the tests on day 28 revealed that CD96 had a mean expression of 26.6% by that time ranging from 7.74 % to 65%. However, CD123 expression ranged from 0.01% to 65.21% with a mean at 19.9 %.
It is evident that the median expressions of both markers were much higher in the patients’ group at diagnosis (being 20.3% for CD96 and 19.7% for CD123) as compared to control group (having a median expression of CD96 at 2.6% and for CD123 at 3.3%). Upon comparing the readings on day 28, it is noticeable that the median expressions of both markers were still much higher than those of the controls with median of 23.75 for CD96 and 19.28 for CD123 .
CD96 exhibited negative correlation to both peripheral blood as well as bone marrow blast percentages either at diagnosis or on day 28 post-induction. Also,CD96 expression on day 28 was positively correlated to its expression on day 0 as well as to CD123 expression at diagnosis.
AML with differentiation (M2,3,4,5) was predominant FAB type in CD96 and CD123 positive cases at D0 & D28
Most of our positive cases for both markers at D0 &D28 have no extramedullary disease but this is not statistically significant ,moreover most of CD96 &CD123 positive patients has unfavorable cytogenetics but without any significance with P-values exceeding 0.05 .
CD96 expression on day 28 was positively correlated to its expression on day 0 as well as to CD123 expression at diagnosis with P-values of <0.001 and 0.034 respectively.
Relating CD96 expression to therapy outcome post-induction revealed no statistical significance between positive and negative cases at diagnosis and D28 (p ≥0.05),moreover comparing the risk of disease recurrence among the CD96 positive and negative cases failed to yield a statistical significant relationship. However, the rate of recurrence was more among CD96 positive patient at D0. We found also CD96 positive expressors at diagnosis exhibited shorter PFS as compared to negative expressors, and shorter median overall survival but neither differences culminated into statistical significance.