EXPRESSION OF HUMAN METALLOTHIONEIN-III CONFERS PROTECTION AGAINST SERUM-FREE EXPOSURE OF STABLY TRANSFECTED CHINESE-HAMSTER OVARY CHO-K1 CELLS

The cloned human metallothionein (MT)-III coding region was permanentl y transfected in Chinese hamster ovary (CHO-K1) cells in order to inve stigate the growth regulatory effects of this brain-specific protein. Reverse transcription-polymerase chain reaction (RT-PCR) experiments d emonstrated stable expression of MT-III mRNA in CHO-K1/MT-III cells. W hereas in the presence of serum no differences were observed between t he cell growth of both CHO-K1/MT-III and CHO-K1/pcDNA3-plasmid transfe cted cells, cell survival was attenuated differently in serum-free med ium. CHO-K1/MT-III cells were more resistant (40 +/- 8%) to serum depr ivation than pcDNAS-plasmid transfected cells. Recovery of cell growth for both cell lines was obtained by supplementing serum (0.25%), alth ough with a different growth rate; half-maximal 3-(4,5-dimethylthiazol -2-yl)-2,5-diphenyl tetrazolium bromide (MTT)-conversion was observed between 5.1-5.7 and 4.2-4.5 days for CHO-K1/pcDNA3 and CHO-K1/MT-III c ells, respectively. These results suggest a protective role for cloned human MT-III, besides its reported inhibitory and stimulatory effects on cell survival.