Insulin-like growth factor-I receptor in proliferation and motility of pancreatic cancer

AIM: To develop a molecular therapy for pancreatic cancer, the insulin-like growth factor-I (IGF-I) signaling pathway was analyzed. METHODS: Pancreatic cancer cell lines (MIA-Paca2, NOR-P1, PANC-1, PK-45H, PK-1, PK-59 and KP-4) were cultured in media with 10 mL/L fetal bovine serum. Western blotting analysis was performed to clarify the expression of IGF-I receptor (IGF-IR). Picropodophyllin (PPP), a specific inhibitor of IGF-IR, LY294002, a specific inhibitor of phosphatidylinositol 3 kinase (PI3K), and PD98059, a specific inhibitor of mitogen-activated protein kinase, were added to the media. After 72 h, a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay was performed to analyze cell proliferation. A wound assay was performed to analyze cell motility with hematoxylin and eosin (HE) staining 48 h after addition of each inhibitor. RESULTS: All cell lines clearly expressed not only IGF-IR but also phosphorylated IGF-IR. PPP significantly suppressed proliferation of MIA-Paca2, NOR-P1, PANC-1, PK-45H, PK-1, PK-59 and KP-4 cells to 36.9% +/- 2.4% (mean +/- SD), 30.9% +/- 5.5%, 23.8% +/- 3.9%, 37.1% +/- 5.3%, 10.4% +/- 4.5%, 52.5% +/- 4.5% and 22.6% +/- 0.4%, at 2 micromol/L, respectively (P < 0.05). LY294002 significantly suppressed proliferation of MIA-Paca2, NOR-P1, PANC-1, PK-45H, PK-1, PK-59 and KP-4 cells to 44.4% +/- 7.6%, 32.9% +/- 8.2%, 53.9% +/- 8.0%, 52.8% +/- 4.0%, 32.3% +/- 4.2%, 51.8% +/- 4.5%, and 30.6% +/- 9.4%, at 50 micromol/L, respectively (P < 0.05). PD98059 did not significantly suppress cell proliferation. PPP at 2 micromol/L suppressed motility of MIA-Paca2, NOR-P1, PANC-1, PK-45H, PK-1, PK-59 and KP-4 cells to 3.0% +/- 0.2%, 0%, 0%, 2.0% +/- 0.1%, 5.0% +/- 0.2%, 3.0% +/- 0.1%, and 5.0% +/- 0.2%, respectively (P < 0.05). LY294002 at 50 micromol/L suppressed motility of MIA-Paca2, NOR-P1, PANC-1, PK-45H, PK-1, PK-59 and KP-4 to 3.0% +/- 0.2%, 0%, 3.0% +/- 0.2%, 0%, 0%, 0% and 3% +/- 0.1%, respectively (P < 0.05). PD980509 at 20 micromol/L did not suppress motility. Cells were observed by microscopy to analyze the morphological changes induced by the inhibitors. Cells in medium treated with 2 micromol/L PPP or 50 micromol/L LY294002 had pyknotic nuclei, whereas those in medium with 20 micromol/L PD98059 did not show apoptosis. CONCLUSION: IGF-IR and PI3K are good candidates for molecular therapy of pancreatic cancer.