RESUMO
<p><b>OBJECTIVE</b>To investigate the expression of Notch gene in chronic lymphocytic leukemia cells and to explore the change of Notch protein after the therapy with cytosine arabinoside or dexmethasone, and the mechanism of Notch mediated anti-apoptosis and drug-resistance in chronic lymphocytic leukemia cells.</p><p><b>METHODS</b>The mononuclear cells from bone marrow or peripheral blood of chronic lymphocytic leukemia patients (24 cases) and healthy donors (14 cases) were collected, then the expression of Notch gene, BCL-2, as well as NF-κB gene were detected by real-time fluorescent quantitative PCR (qRT-PCR) at the level of transcription. The change of Notch protein in L1210 cell lines after therapy with cytosine arabinoside and dexmethasone was determined by Western blot.</p><p><b>RESULTS</b>mRNA expression levels of Notch1, Notch2, BCL-2 and NF-κB gene in CLL group were significantly higher than those in healthy control group (0.8556 ± 0.8726 vs 0.6731 ± 0.5334, P = 0.0182; 1.2273 ± 0.8207 vs 0.6577 ± 0.6424, P < 0.0001; 8.0960 ± 7.5661 vs 0.5969 ± 0.4976, P < 0.0001; 1.0966 ± 0.6925 vs 0.5373 ± 0.7180, P < 0.0001, respectively), but no significant difference was found between Notch3 and Notch4 gene (1.1914 ± 2.4219 vs 0.8713 ± 0.7937, P = 0.3427; 0.8174 ± 1.0869 vs 0.9752 ± 1.3446, P = 0.2402, respectively). Notch1 protein expression in L1210 cells were significantly decreased after treating with cytosine arabinoside of low and middle concentrations, but increased after treating with cytosine arabinoside of high concentration or prolonging time of cytosine arabinoside of middle con-centration. Notch1 protein expression in L1210 cells dereased after treating with dexamethasone, but did not be changed with the different concentrations and different times of dexmethason.</p><p><b>CONCLUSION</b>The transcription level of Notch gene in CLL patients significantly higher than that in normal controls. The Notch1 protein expression is down-regulated in process of inhibiting L1210 cell proliferation by Ara-C and dexmethason. Notch signaling pathway may mediated anti-apoptosis and drug resistance of CLL cells. Notch molecule possibly plays an important role in the anti-apoptosis and drug-resistance of CLL cells.</p>