The highest expressed GPCRs in PDAC tumors (as an example, this finding is generalizable to other tumor types) are generally overexpressed compared to normal tissue and include orphan receptors (e.g., GPRC5A and ADGRF4/GPR115) and GPCRs with known agonists (e.g., GPR68) (Fig 2A and 2C). This evidence concerns the gene GPR68 and neoplasm.