Interleukin-1 beta-mediated metallothionein induction and cytoprotection against cadmium and...

Metallothioneins (MTs) are major intracellular protein thiols that have been associated with resistance to the cytotoxicity of heavy metals and some cytotoxic anticancer drugs. The accumulation and subcellular location of MT and its functionality were examined in a human hormone-independent prostatic tumor cell line (DU-145) exposed to cytokines that participate in autocrine growth and the acute phase response. Incubation of DU-145 cells with interleukin-1 beta (IL-1 beta) caused a concentration-dependent increase in MT protein reaching a 2- to 3-fold maximum increase 24 to 48 hr after treatment with 10 U of IL-1 beta/ml; smaller increases were seen with human recombinant IL-1 alpha and tumor necrosis factor alpha. DU-145 cells constitutively expressed only MT-IIa and MT-Ie mRNA and the IL-1 beta-mediated increase in MT protein was preceded by a marked elevation solely in MT-IIa mRNA. Basal MT was immunolocalized by confocal microscopy primarily to the nucleus of DU-145 cells with some granular deposits near the cell surface. IL-1 beta treatment increased nuclear MT. DU-145 cells pretreated with IL-1 beta were 2- to 3-fold resistant to the toxicity of CdCl2 and cis-diamminedichloroplatinum(II) (cisplatin). Both MT induction and cytoprotection against CdCl2 and cisplatin were blocked by concomitant incubation with a recombinant human IL-1 receptor antagonist protein. These results suggest the responsiveness of human prostatic tumor cells to cytotoxic electrophilic anticancer drugs can be diminished by direct exposure to the cytokine IL-1 beta, possibly by a mechanism involving MT.