This study aimed to determine whether and how the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide affects the chemoresistance and chemosensitivity of pancreatic cancer cells to gemcitabine in vitro and in vivo. The GLP-1R and protein kinase A (PKA) levels were compared between the human pancreatic cancer cell line PANC-1 and the gemcitabine-resistant cell line PANC-GR. The in vitro effects of liraglutide on the cell proliferation and apoptosis as well as the nuclear factor-kappa B NF-κB expression levels of PANC-GR cells were evaluated. In addition, a mouse xenograft model of human pancreatic cancer was established by s.c. injection of PANC-1 cells, and the effects of liraglutide on the chemosensitivity were evaluated in vitro and in vivo. In contrast to PANC-1 cells, PANC-GR cells exhibited lower expression levels of GLP-1R and PKA. Incubation with liraglutide dose dependently inhibited the growth, promoted the apoptosis, and increased the expression of GLP-1R and PKA of PANC-GR cells. Similar effects of liraglutide were observed in another human pancreatic cancer cell line MiaPaCa-2/MiaPaCa-2-GR. Either the GLP-1R antagonist Ex-9, the PKA inhibitor H89, or the NF-κB activator lipopolysaccharide (LPS) could abolish the antiproliferative and proapoptotic activities of liraglutide. Additionally, each of these agents could reverse the expression of NF-κB and ABCG2, which was decreased by liraglutide treatment. Furthermore, liraglutide treatment increased the chemosensitivity of pancreatic cancer cells to gemcitabine, as evidenced by in vitro and in vivo experiments. Thus, GLP-1R agonists are safe and beneficial for patients complicated with pancreatic cancer and diabetes, especially for gemcitabine-resistant pancreatic cancer.
Supplementary Figure 1 The GLP-1R expression and the effects of liraglutide on the cell growth and apoptosis of MiaPaCa-2-GR cells. (A–B) The expression levels of GLP-1R (A) and PKA (B) by western blot (top), and the GAPDH-corrected band intensities (bottom). (C–G) MiaPaCa-2-GR cells were treated with Lira at 0 nM (control), 10 nM, 100 nM, or 1000 nM for specified durations. The expression of GLP-1R (C) and PKA (D) in MiaPaCa-2-GR cells by western blot (top), and their band intensities relative to GAPDH (bottom). (E) Cell proliferation was evaluated at 24 h and 48 h by using the Cell Counting Kit-8 assay. #P < 0.05 (10 nM vs. control); $P < 0.05 (100 nM vs. control); &P < 0.05 (1000 nM vs. control). The expression of Bax (F) and caspase-3 (G) as detected by western blot (top), and their band intensities relative to GAPDH (bottom). *P < 0.05 vs. control. Lira, liraglutide.
Supplementary Figure 2 The expression levels of NF-κB and ABCG2 in PANC-GR cells versus PANC-1 cells. PANC-GR cells exhibited higher expression levels of NF-κB and ABCG2. (A–B) Top, the expression level of NF-κB by RT-PCR (A) and western blot (B); Bottom, GAPDH-corrected band intensities. (C–D) Top, the expression level of ABCG2 by RT-PCR (C) and western blot (D); Bottom, GAPDH-corrected band intensities.