Hormone-Driven Growth Signaling as a Therapeutic Target in Acute Myeloid Leukemia: Implications for Drug-Resistant Disease

Growth hormone-releasing hormone (GHRH) antagonists have displayed anti-neoplastic activity against a multitude of cancers in vitro, as well as in vivo, via xenografted tumors in nude mice. Following a successful demonstration of GHRH antagonists treating non-Hodgkin’s lymphoma and the discovery of GHRH mRNA and peptide products in immune cells, GHRH antagonism was explored in acute myeloid leukemia (AML), a disease characterized by a malignant expansion of immature myeloid progenitors, and poor 5-year survival. Targeted therapies have yielded breakthroughs in treatment response and overall survival, such as all-trans retinoic acid/arsenic trioxide (ATRA/ATO) for acute promyelocytic leukemia (APL), or FLT3 inhibitors, IDH inhibitors, and menin inhibitors for AML harboring actionable genetic lesions. However, therapeutic resistance remains a major barrier to durable remission. GHRH receptor (GHRH-R) has been reported in several experimental models of AML, including drug-resistant sublines. Significant time- and dose-dependent reduction in leukemic growth was observed in vitro and in vivo following MIA-602 treatment. FLT3 inhibitor resistance has been associated with activation of PI3K/AKT, ERK/MAPK, inflammatory, stromal, and apoptotic escape pathways. The documented effects of GHRH-R antagonism raise the possibility that it could influence signaling networks relevant to therapeutic resistance in AML. This hypothesis remains speculative; to date no studies have stratified AML by FLT3 status in the context of GHRH-R expression or GHRH antagonism, and there is currently no evidence that MIA-602 directly alters FLT3 receptor signaling or inhibitor sensitivity.