ABCG2 and familial pancreatic carcinoma: AFAP1-AS1, actin filament-associated protein 1 antisense RNA 1; PC, pancreatic cancer; RT-qPCR, reverse transcription quantitative polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; ACVR1, activin receptor A type I; ABCG2, ATP-binding cassette subfamily G member 2.