Inhibitory effect of PPL on the proliferation of liver cancer cells by the inhibition of ADRB2. (A) ADRB1 and ADRB2 were localized on the cell membrane of the three cell lines, as demonstrated by immunofluorescence. Scale bar, 50 µm. (B) The expression of ADRB1and ADRB2 on HepG2 and HepG2.2.15 cells was higher than HL-7702 cells. The expression of ADRB2 was higher than ADRB1 on all three cell lines. (C) PPL decreased the expression of ADRB1 and ADRB2, particularly ADRB2, on liver cancer cells, as demonstrated by immunofluorescence. (D) PPL treatment decreased the expression of ADRB1 and 2 in liver cancer cells, as demonstrated by western blotting. (E) ADRB2 mRNA expression was determined with reverse transcription-quantitative polymerase chain reaction. PPL decreased ADRB2 expression in a concentration-dependent manner in the HepG2 and HepG2.2.15 cells. *P<0.05. PPL, propranolol hydrochloride; ADRB1, adrenergic receptor β-1; ADRB2, adrenergic receptor β-2.