Leukotriene B4 receptor antagonist LY293111 inhibits proliferation and induces apoptosis in human pancreatic cancer cells.

PURPOSE The effects of leukotriene (LT) B4 and its receptor antagonist LY293111 on proliferation and apoptosis of human pancreatic cancer cells were investigated, both in vitro and in vivo. EXPERIMENTAL DESIGN Six human pancreatic cancer cell lines (MiaPaCa-2, HPAC, Capan-1, Capan-2, PANC-1, and AsPC-1) were used. Expression of LTB4 receptors, BLT1 and BLT2, was measured by reverse transcription-PCR. Cell proliferation was measured by [methyl-(3)H]thymidine incorporation and cell number counting. Extracellular signal-regulated kinase (ERK) 1/2 activation was measured by Western blotting. Apoptosis was assessed by morphology, terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, and poly(ADP-ribose) polymerase cleavage. The effect of LY293111 on growth of AsPC-1 and HPAC cell xenografts was assessed in BALB/c nu/nu athymic mice. RESULTS Both LTB4 receptor types were found to be expressed in human pancreatic cancer cells. The LTB4 receptor antagonist LY293111 caused both time- and concentration-dependent inhibition of proliferation of all six human pancreatic cancer cell lines studied. In contrast, LTB4 stimulated proliferation of these cell lines and induced ERK1/2 phosphorylation. The growth-stimulatory effect and ERK1/2 phosphorylation induced by LTB4 were inhibited by LY293111. Coincident with growth inhibition, LY293111 induced apoptosis in these pancreatic cancer cell lines, as indicated by morphology, TUNEL assay, and poly(ADP-ribose) polymerase cleavage. In studies using AsPC-1 and HPAC cell xenografts in athymic mice, LY293111 treatment markedly inhibited tumor growth over a 24-day treatment period, as measured by both tumor volume and tumor weight. In situ tissue TUNEL assay showed massive apoptosis in LY293111-treated tumor tissues. CONCLUSIONS LTB4 can directly regulate the growth of human pancreatic cancer cells and control their survival. Additional studies will clarify the underlying mechanisms of LTB4-regulated pancreatic cancer cell growth and apoptosis. LTB4 receptor blockade and inhibition of the downstream signal pathway are likely to be valuable for the treatment of human pancreatic cancer.