For deveplopment and function of the lung, progesterone (Prog) fulfils important roles. In a recent report, immunolocalization of Prog and estrogen receptors in non-small cell lung carcinomas were examined and it was shown that the Prog receptor might be a potent prognostic factor. In the present study, a cell line with the sensitivity to Prog was established from a human lung cancer and the growth mechanism was analyzed. The proliferation of established SN96-42 cells was sensitive to Prog and antiprogesterone RU38486 inhibited their proliferation stimulated by Prog. Exposure of these cells to Prog resulted in a decreased formation of leukotriene (LT). The 5-lipoxygenase inhibitor (5-LOX), AA861, effectively stimulated SN96-42 cell proliferation and 5-LOX-catalyzed product(s), especially LTC4, inhibited SN96-42 cell proliferation caused by Prog. Prog-sensitive enhancement of SN96-42 cell proliferation is at least partly mediated through an inhibition of LT formation and these data suggest that 5-LOX and LTs play important roles in SN96-42 cell proliferation stimulated by Prog.

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