IGF1 and cancer: Nevertheless, the observations that the GHRH(1-29)NH2 and GHRH agonist, MR-409, inhibited the expression of mRNA for IGF-1 as well as IGF-1 secretion by human and rat hepatocytes and human cancer cells in vitro, after stimulation with rhGH, imply that GHRH agonists may exert these effects by direct action on the cells.