Fast apoptosis and erythroid differentiation induced by imatinib mesylate in JURL‐MK1 cells

Abstract

We compare the effects of Imatinib mesylate (Glivec) on chronic myeloid leukemia derived cell lines K562 and JURL-MK1. In both cell lines, the cell cycle arrests in G(1)/G(0) phase within 24 h after the addition of 1 microM Imatinib. This is followed by a decrease of Ki-67 expression and the induction of apoptosis. In JURL-MK1 cells, the apoptosis is faster in comparison with K562 cells: the caspase-3 activity reaches the peak value (20 to 30 fold of the control) after about 40 h and the apoptosis proceeds to its culmination point, the DNA fragmentation, within 48 h following 1 microM Imatinib addition. Unlike K562 cells, JURL-MK1 cells possess a probably functional p53 protein inducible by TPA (tetradecanoyl phorbol acetate) or UV-B irradiation. However, no increase in p53 expression was observed in Imatinib-treated JURL-MK1 cells indicating that the difference in the apoptosis rate between the two cell lines is not due to the lack of p53 in K562 cells. Imatinib also triggers erythroid differentiation both in JURL-MK1 and K562 cells. Glycophorin A expression occurred simultaneously with the apoptosis, even at the single cell level. In K562 cells, but not in JURL-MK1 cells, the differentiation process involved increased hemoglobin synthesis. However, during spontaneous evolution of JURL-MK1 cells in culture, the effects produced by Imatinib progressively changed from the fast apoptosis to the more complete erythroid differentiation. We suggest that the apoptosis and the erythroid differentiation are parallel effects of Imatinib and their relative contributions, kinetics and completeness are related to the differentiation stage of the treated cells.

Isoform‐specific cleavage of 14‐3‐3 proteins in apoptotic JURL‐MK1 cells

“…We have previously shown that Imatinib mesylate treatment induces apoptosis in JURL-MK1 cells [Kuželová et al, 2005]. Figure 2 shows the kinetics of Imatinib-induced caspase-3 activation measured using the fluorogenic caspase-3 substrate (panel A) and apoptotic DNA fragmentation detected by TUNEL method (panel B).…”

Changes in cell adhesivity and cytoskeleton‐related proteins during imatinib‐induced apoptosis of leukemic JURL‐MK1 cells

“…1S). We have previously shown that imatinib mesylate induces apoptosis including a marked caspase‐3 activation and DNA fragmentation in JURL‐MK1 cells [Kuželová et al , 2005].…”

Labeling of apoptotic JURL‐MK1 cells by fluorescent caspase‐3 inhibitor FAM‐DEVD‐fmk occurs mainly at site(s) different from caspase‐3 active site

“…This compound induces cell cycle arrest followed by complete apoptosis including the mitochondrial apoptotic antigen 7A6 expression, caspases activation, and DNA fragmentation (20). Careful analysis of the effects of unlabeled caspase inhibitors z-DEVD-fmk and z-VAD-fmk on FLICA staining led us to conclude that, in our experimental system, the fluorescent signal of FLICA originates mainly, if not exclusively, from still unspecified sites that differ from the caspase active sites.…”

“…Up to 30-fold increase in caspase-3 activity over the control values was observed in cell lysates using fluorogenic substrate Ac-DEVD-AFC, within 40-50 h following Imatinib addition (20). In the present work, we employed the fluorochromelabeled caspase-3 inhibitor FAM-DEVD-fmk (hereafter referred to as FLICA) to monitor the caspase activation in individual cells by means of flow cytometry.…”