RXRB and familial pancreatic carcinoma: Interest in the role of vitamin A in tumor therapy and specifically PDAC therapy is reinforced by the finding that, although human pancreatic cancer cell lines express the nuclear receptors RARα, RARβ, RXRα, and RXRβ necessary for vitamin A action [46,47], these are often downregulated in PDAC tissue compared to healthy tissue [48].