EFFECTS OF ANTISENSE DNA ON POMC MESSENGER-RNA AND ACTH LEVELS IN CULTURED HUMAN CORTICOTROPH ADENOMA CELLS

Antisense oligonucleotides have been investigated in recent years as p otential new therapeutic agents because of their ability to shut off g ene expression. Antisense DNA and RNA oligomers can bind specifically to mRNA preventing protein translation. We have studied the ability of an antisense POMC oligomer to reduce the expression of POMC in human ACTH-secreting pituitary adenoma cells cultured from 2 uncommon ACTH-s ecreting macroadenomas. In separate experiments, tumor tissue was enzy matically dispersed, cultured for 4 days, and treated with and without an antisense POMC oligonucleotide for 18 hours. In addition, cells fr om one tumor were treated with dexamethasone and cells from the other tumor were treated with an unrelated oligomer as controls. RNA was pre pared from cultured cells and POMC mRNA was quantitated in a RNase pro tection assay using a human POMC RNA probe. ACTH in the media was quan titated by RIA. Tumor cells responded to 250 nmol/L dexamethasone with diminished POMC mRNA and ACTH levels 18 hours after treatment (decrea sed by 28% and 67% of control respectively). In both tumors, a POMC an tisense oligomer at a concentration of 50 mu mol/L lowered POMC mRNA l evels and detectable ACTH levels in the media 18 hours after treatment , with mRNA levels decreased by 76% and 62% of control and ACTH levels decreased by 58% and 48% of control. Conversely, tumor cells treated with an unrelated oligomer at a 50 mu mol/L concentration showed minim al effect on POMC mRNA and ACTH levels 18 hours after treatment (decre ased by 2.3% and 1.5% of control respectively). Our findings confirm t he effects of antisense oligonucleotides in other systems and suggest that therapeutic investigations using these techniques may have applic ation to syndromes of hormone excess.