Effects of insulin-like growth factor binding protein-3 and farnesyltransferase inhibitor SCH66336 on Akt expression and apoptosis on non-small-cell lung cancer cells

Background: Overexpression of insulin-like growth factor binding protein-3 (IGFBP-3) induces apoptosis in non-small-cell lung cancer (NSCLC) cells in vitro and in vivo. However, Ras-mediated signaling pathways could develop resistance to apoptotic activities of IGFBP-3 in NSCLC cells. We thus evaluated the therapeutic potential of the combination of IGFBP-3 and SCH66336, a farnesyltransferase inhibitor that blocks Ras activation, in NSCLC cell lines. Methods: The effects of the combination of adenoviral IGFBP-3 (Ad-IGFBP3) and SCH66336 on proliferation and apoptosis of NSCLC cell lines (H1299, H596, A549, H460, H358, H322, and H226B) were assessed in vitro and in vivo by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a How cytometry-based terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assay, western blot analyses, and an NSCLC xenograft tumor model. The specific effects of Ad-IGFBP 3 and SCH66336 on mitogen-activated protein kinase and Akt were assessed by using adenoviral vectors that express constitutively active MEK1 or constitutively active Akt. Synergy was assessed by median effect analysis. Results: The combination of Ad-IGFBP3 and SCH66336 had synergistic anti-proliferative effects in five cell lines (111299, H596, A549, H460, and H322). Antiproliferative effects were accompanied by increased apoptosis in H460 cells in vitro. Overexpression of a constitutively active Akt but not a constitutively active MEK-1 rescued H460 cells from apoptosis induced by single or combined treatment of Ad-IGFBP3 and SCH66336. In H1299 tumor xenografts, Ad-IGFBP3 and SCH66336 was associated with decreased tumor volume, increased apoptosis, and decreased Akt levels. Conclusions: The combination of Ad-IGFBP3 and SCH66336 decreased Akt expression and Simultaneous treatment with IGFBP-3 and SCH66336 may have the potential to be an effective therapeutic strategy in NSCLC.