We have previously shown that the
leukotriene B4 receptor antagonist,
LY293111 inhibits proliferation and induces apoptosis in human
pancreatic cancer cells both in vitro and in vivo. In the current study, we investigated the molecular mechanisms of LY293111-induced apoptosis and cell cycle arrest. Two human
pancreatic cancer cell lines were used in this study, MiaPaCa-2 and AsPC-1. Cell cycle analysis by flow cytometry showed a dramatic increase in the percentage of apoptotic cells as well as S-phase arrest
after treatment with 250 nmol/l
LY293111 for up to 48 h. Western blotting indicated that
LY293111 treatment induced
cytochrome c release from the mitochondria into the cytosol, accompanied by
caspase-9,
caspase-7 and
caspase-3 activation, and cleavage of
poly ADP-ribose polymerase.
Caspase-8 was not activated by
LY293111. A decrease was found in the expression of the antiapoptotic
proteins, Bcl-2 and Mcl-1, and an increase in the proapoptotic
protein, Bax.
LY293111 reduced the expression of CDK2,
cyclin A and
cyclin E, consistent with the S-phase arrest observed in these cells. The expression of
cyclin-dependent kinase inhibitors, p21 and p27 was not affected by
LY293111 treatment. In conclusion,
LY293111 induces apoptosis in human
pancreatic cancer cells through the mitochondria-mediated pathway.
LY293111 also induces S-phase arrest with downregulation of CDK2,
cyclin A and
cyclin E. Blockade of
leukotriene B4 metabolic pathway may provide a novel treatment for human
pancreatic cancer.