Characterization of aspects of leukemia biology and association with patient prognosis
In this thesis, molecular features of childhood acute lymphoblastic leukemia (ALL) samples were addressed in order to characterize potential prognostic markers associated with NOD/SCID/huALL (non-obese diabetic/severe combined immunodeficiency/human acute lymphoblastic leukemia) engraftment phenotypes. Apoptosis signaling, which is known to be important for treatment response and outcome of leukemia patients was investigated. In accordance with previous findings of our research group, we found an up-regulation of the anti-apoptotic molecule PDE4A (phosphodiesterase 4A) and down-regulation of pro-apoptotic DAPK1 (death-associated protein kinase 1) in ALL samples with accelerated NOD/SCID engraftment (time to leukemia short, TTLshort). We did not detect significant differences on transcript and protein levels of BCL-2 (B-cell lymphoma 2), MCL-1 (myeloid cell leukemia sequence 1), XIAP (X-linked inhibitor of apoptosis protein) and LIVIN (also known as BIRC7, baculoviral IAP repeat containing 7). In order to investigate apoptosis signaling at a functional level, two key steps of the apoptosis pathway, cytochrome c release and caspase-3 activation were analyzed in ALL xenograft samples. This study demonstrated a correlation of prolonged NOD/SCID engraftment of ALL cells to parameters reflecting proficient apoptosis signaling and superior relapse free survival in the corresponding patients showing intact apoptosis signaling. In order to identify further differentially expressed molecules in TTLshort or TTLlong, a reverse phase protein array (RPPA) and subsequent western blot (WB) analyses were performed. Comparison of the protein levels between the two groups revealed CYCLIN B to be over-expressed in TTLshort. Further, RPPA analysis and subsequent WB analyses revealed PKC (protein kinase C) alpha to be down-regulated in TTLshort. These findings in conjunction with other studies have implications for further characterization of CYCLIN B and PKC alpha in ALL patients.
Subject HeadingsApoptosis [GND]