This study was undertaken to investigate the effect of arachidonic acid on apoptosis of bcr-abl transformed hematopoietic cells. Exposure of the bcr-ab!H7A54 cell line to arachidonic acid ( 10-100 M) for 24-72 hrs induced a dose and time dependent inhibition of cell proliferation. Inhibition of cell growth was associated with induction of apoptosis as assessed by morphological examination, DNA laddering and annexin V binding. The effect of arachidonic acid was also assessed in the parental cell line H7. Arachidonic acid ( 100 uM) induced 25 and 85 % inhibition of cell growth at 72 hrs of incubation in H7 and H7A54 cells, respectively, suggesting that the bcr-abl transformed cells are more sensitive to the inhibitory effect of the fatty acid as compared to their normal counterpart. To gain insights on the signaling pathway of arachidonate-induced apoptosis we performed experiments to explore the possibility that the effect of arachidonic acid on inhibition of cell proliferation and induction of apoptosis was mediated by activation of proteases. To test this possibility bcr-ab!H7A54 cells were preincubated with different concentrations (25-100 uM) of Ac-YVAD-CMK, an irreversible inhibitor of the interleukin-1 converting enzyme (ICE) or caspase 1 and subsequently exposed to arachidonic acid ( 50 u.M for 72 hrs). Preincubation of cells with Ac-YVAD-CMK blunted the ability of arachidonic acid to inhibit cell proliferation. Similarly, inibition of ICE also blocked the ability of arachidonic acid to induce apoptosis. Conversely preincubation of A54 cells with Ac-YVAD-CMK failed to overcome the inhibitory effect on cell proliferation of the tyrosine kinase inhibitor, genistein. We next determined whether arachidonic acid induced caspase 1 activation. Lysates from control and arachidonate-treated cells were assayed for proteolytic activity as determined by the cleavage of a GST tagged substrate containing the ICE cleavage from a lamin protein of 46 kDa. A 46 kDa protein was detected by Western blot analysis in lysates from control cells whereas in lysates from arachidonate-treated cells the appearance of a lower molecular weight protein ( 26 kDa) was observed indicating lamin cleavage upon exposure to arachidonic acid. These findings are consistent with the hypothesis that arachidonic acid induces apoptosis in bcr-abl transformed cells by a caspase-dependent signaling mechanism.
|Number of pages||1|
|Publication status||Published - 1998|
ASJC Scopus subject areas
- Cancer Research
- Cell Biology