GPRC5A and neoplasm: The controversial results obtained in RA and VD cancer chemoprevention [49] might, therefore, result from the balance between the multiple parallel and often opposing signalling pathways activated by GPRC5A in different tumours (e.g., EGFR inhibition [46] vs. HIF-[1,2GPRC5A-YAP [14], or GPRC5A-JAK2-STAT3-TNS4 [15]).