VNN1 and cancer: However, elevated GPRC5A expression has been reported in colorectal cancer (CRC), where it promotes tumour progression through VNN1 (Vanin 1)-induced oxidative stress [13] and facilitates cancer cell adaptation to hypoxia through the HIF (hypoxia-inducible factor), GPRC5A, and YAP (YES proto-oncogene 1-associated transcriptional regulator) axis [14], suggesting that GPRC5A may also act as a tumour promoter.