It is noticeable that HL60 cells were selleckchem 17-DMAG more sensitive at 24 h than control cells. The Namalwa and Raji lines are mutant for p53 Namalwa cells are p53 double mutant cells that contain two non synonymous mutations in exon 7 of p53 gene, while Raji cells contain mutations in exon 6. Nevertheless, the mutated proteins are stabilized in these cells and can accu mulate to relatively high levels. As shown in Figure 6C, Namalwa cells were highly susceptible to DRB induced death within the 40 100 M range in a dose dependent manner and the death mechanism was apoptosis, as demonstrated by their pos itive staining for active caspase 3 and cell surface annexin V expression. It is noticeable that Namalwa cells were more sensitive at 24 h than control cells.

Raji cells were also susceptible to DRB induced cytotoxicity, albeit with some differences in the death pathway and kinetics DRB induced death occurred only after 48 hr and apoptosis was not the solely mechanism of death, as caspase 3 activation and cell surface annexin V expression were only detectable after 48 hr and in a low percentage of cells. Blast cells from a primary AML sample are highly sensitive to DRB treatment Lastly, the effect of DRB on cell viability and apoptosis induction was studied in a human primary AML sample. Leukemic blasts, selected through SSC CD45 parameters accounted for about 60% of total cells. To define the sensitivity of both tumour blasts and non malignant cells to this drug, we assessed the viability of treated cells in a dose response experiment using CD45 PI staining and flow cytometry.

Blast cells were susceptible to DRB induced death within the 10 100 M range in a dose dependent manner and the death mechanism Batimastat was apoptosis. Interestingly, blast cells were significantly more sensitive to DRB than non malignant cells at all doses analysed. Discussion Here we show that the cyclin dependent kinase inhibitor DRB efficiently leads normal and leukemic cells to apop tosis in a DNA replication and DNA damage independ ent manner. In T cells expressing wild type p53, DRB mia lymphomaDRB induced apoptosis in prototypic leukae induced a cytosolic p53 response that led the cells to apoptosis through Bax activation. Nevertheless, apoptosis was also induced in p53 deficient mutated leukemic cells through alternative pathways, possibly involving p73. Overall, the transcription stress response imposed by DRB is very powerful in inducing apoptosis independently of a cells p53 status, and could provide an attractive approach to the treatment of some forms of cancer.