Publication Date:
2009-11-20
Description:
Abstract 189 Imatinib mesylate (IM) treatment has primarily anti-proliferative effects on CML progenitors, and only modest induction of apoptosis is observed. Quiescent, primitive progenitors are especially insensitive to IM induced apoptosis. Identification and targeting of mechanisms of resistance to IM is required to allow enhanced elimination of residual CML progenitors in IM treated patients. SIRT1 is a NAD+ dependent deacetylase that regulates activity of several proteins involved in stress responses. We have observed significantly increased expression of SIRT1 mRNA and protein in CML compared to normal CD34+ progenitors. Here we investigated the effect of inhibition of SIRT1 expression on growth, survival and IM sensitivity of CML progenitors. CML and normal CD34+ cells were transduced with lentivirus vectors expressing SIRT1 shRNAs (Si-1 or Si-2) or control shRNA (Ctrl). Inhibition of SIRT1 expression in Si-1 (95% inhibition) and Si-2 (80% inhibition) transduced CD34+ cells was confirmed on Western blotting. SIRT1 inhibition resulted in modest increase in apoptosis of CML progenitors (Si-1 16±9%, Si-2 10±5% and Ctrl 8±4% apoptosis), and significantly enhanced sensitivity of CML progenitors to IM (2.5μM) induced apoptosis (Si-1, 27±12%, Si-2, 15±4% and Ctrl, 14±5%, Si-1 versus Ctrl, p=0.04, n=4). SIRT1 inhibition did not induce apoptosis in normal progenitors or increase their sensitivity to IM (Si-1 14±3%, Si-2, 13±4% and Ctrl, 11±2% without IM; and Si-1, 14±2%, Si-2, 12±3% and Ctrl, 12±2% with IM). Importantly SIRT1 inhibition significantly enhanced apoptosis of non-dividing (CFSE bright) CML progenitors treated with IM (Si-1, 49±16% and Ctrl, 33±4%, p=0.02, n=4). SIRT1 knock down inhibited proliferation of CML progenitors measured by CFSE labeling (Si-1, 46±5% and Si-2, 14±3% inhibition versus Ctrl, p
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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