[Effects of site-selective 8-Cl-cAMP on the growth regulation of human lung giant cell cancer].

Type I and type II cAMP receptor proteins participate in cell growth regulation, differentiation and neoplastic transformation of neoplasms. In this paper the growth regulatory effects of cAMP analogs, DBcAMP (non-site-selective) and 8-Cl-cAMP (site-selective) on a highly metastatic human lung cancer cell line PG were studied. By MTT assay, DBcAMP at 1mmol/L was found to inhibit PG growth by 30% on the day 8, while 8-CL-cAMP at 10-20 mumol/L inhibited the growth by 75%-80%. When phosphodiesterase inhibitor isobutyl-1-methyl-xanthine (IBMX) was added the inhibitory effect of 8-Cl-cAMP was not enhanced, whereas that of DBcAMP was significantly enhanced. The invasiveness and colony-forming ability of the treated cells decreased. The cAMP level as determined by RIA was much more increased in DBcAMP-treated than in 8-Cl-cAMP-treated PG cells. The result suggests that 8-Cl-cAMP and DBcAMP exert their effects on tumor cell growth and invasion by defferent mechanisms.