Growth hormone-releasing hormone (GHRH) and its agonists inhibit hepatic and tumoral secretion of IGF-1

The cover for issue 47 of Oncotarget features Figure 6, "MR-409 down-regulates IGF-1 expression in cancer cells," by Cui, et al.

It is difficult to envision that GHRH could be involved in the pathophysiologic control of IGF-1 secretion since the circulating levels of hypothalamic GHRH are very low.

Nobel Prize winner Dr. Andrew V. Schally from the Veterans Affairs Medical Center and University of Miami, Miami, FL, USA said "This paper describes our investigations of the effects of GHRH and its agonists on the synthesis and release of IGF-l in normal liver tissue and in tumors."

During the past years, his research group reported the synthesis of multiple antagonistic analogs of growth hormone releasing hormone and the biological evaluation of their inhibitory effects on growth of various tumors.

Although for many years the sole role of GHRH was thought to be the regulation of the release of growth hormone from the pituitary, these findings show that GHRH and its analogs can also exert direct effects on extra-pituitary cells/tissues.

Dr. Tengjiao Cui, who did the experimental work on this study and who is the first author of the article concluded "Insulin-like growth factor 1, plays an essential physiological role on the growth and development and further studies are required to investigate the possible physiopathological role of GHRH in the control of secretion of IGF-1."

Full text - https://www.oncotarget.com/article/25676/text/

Correspondence to - Andrew V. Schally - andrew.schally@va.gov

Keywords - IGF-1, GHRH agonists, hepatocytes, tumor, JAK2/STAT5 signaling