HIF-dependent Neuropeptide Y Receptor Y1 and Y5 expression sensitizes hypoxic cells to NPY stimulation
Neuropeptide Y (NPY) is an abundant neurohormone in the central and peripheral nervous system involved in feeding behavior, energy balance, nociception, and anxiety. Several NPY receptor (NPYR) subtypes display elevated expression in many cancers including in breast cancer where this is exploited for imaging and diagnosis. Here, we show that NPY1R and NPY5R mRNA abundance is induced by hypoxia in a Hypoxia Inducible Factor (HIF)-dependent manner in breast cancer cell lines MCF7 and MDA-MB-231. The HIFs bind to several genomic regions upstream of the NPY1R and NPY5R transcription start sites. The MAPK/ERK pathway is activated more rapidly upon NPY5R stimulation in hypoxic cells compared to normoxic cells. This pathway requires IGF1R activity in normoxia, but not in hypoxic cells where they display resistance to the radiosensitizer and IGF1R inhibitor AG1024. Hypoxic cells proliferate and migrate more when stimulated with NPY relative to normoxic cells, with a more robust response observed with a Y5-specific agonist. Our data suggest that hypoxia induced NPYRs render hypoxic cells more sensitive to NPY stimulation. Considering that breast tissue receives a constant supply of NPY, and hypoxia is a common feature of the tumor microenvironment, breast tumors are the perfect storm for hyperactive NPYR. This study not only highlights a new relationship between the HIFs and NPYR expression and activity, but may inform the use of chemotherapeutics targeting NPYRs and hypoxic cells.