Abstract 706: FUS1-mediated tumor suppression by inhibiting PDGF/ PDGFR signaling pathway in human lung cancer
Authors: Qing Liu, Guanglin Wu, Kai Xu, Jack A. Roth, Lin Ji
Journal: Cancer Research (2010)

Abstract Systemic treatment with FUS1-DOTAP:cholesterol (DC) nanoparticles shows a potent antitumor efficacy in preclinical lung cancer animal models and promising clinical benefits in advanced lung cancer patients. However, the currently available gene transfer protocols and techniques for cancer gene therapy are capable of transducing only a fraction of tumor cells in vivo, thus, relying on a bystander effect (killing of non-transduced cells by products of transduced cells) to achieve clinically-meaningful therapeutic efficacy. To determine the mechanism of FUS1-nanoparticle-induced bystander effect, we performed molecular profiling in conditioned medium (CM) prepared from human NSCLC cells transfected by FUS1 to identify the distinct soluble peptide molecules that are secreted by FUS1-transfection and could act as cytotoxic or apoptotic effectors. CMs were collected from FUS1-DC-transduced H1299 cells after 48 and 72 hr transfection or from ponasterone A (PA)-induced FUS1-expressing H1299 cells after 48 and 72 hr induction, respectively. The CMs from untransduced, or empty vector (EV) and mutant FUS1-transduced H1299 cells were used as controls. We performed multiplex analysis to quantitatively determine changes in cytokines, angiogenesis, apoptosis, and cell growth-associated factors secreted in these CMs. The multiplex assay revealed distinctive molecular profiles in multiple cytokines including IL-2Ra, IL3, IL-16, angiogenic, and apoptotic factors such as GRO-a, ICAM-1, MCP3, Trail, and VCAM-1 expression in FUS1-CM compared to those of control CMs. Interestingly, PDGF is one of the cytokines that showed a significantly reduced level in FUS1-CMs. The results from the multiplex cytokine assay were further confirmed by a PDGF-specific ELISA assay. We also examined PDGF-β and PDGFR expression in various lung cancer cell lines and found high expression of PDGF-β and PDGFRβ but not PDGF-α and PDGFRα in almost all cell lines tested. Immunoprecipitation and immunoblot analyses showed that FUS1 protein interacted directly with PDGFRβ but not with the PDGF ligands. Ectopic expression of wt-FUS1 by DC-mediated gene transfer in the PDGFRβ-expressing SCLC H128 and NSCLC H358 cell lines inactivated PDGFR, as evidenced by significant reductions in phospho-PDGFRβ relative to untransfected or lacZ-transfected controls. Levels of phospho-PI3-K and phospho-AKT proteins, downstream targets of the PDGF/PDGFR signaling pathway, were markedly reduced as well. Finally, combined treatment with FUS1-DC and the PTK inhibitor imatinib (Gleevec) synergistically inhibited growth and induced apoptosis in SCLC and NSCLC cell lines that contained highly activated phospho-PDGFRβ. Our results suggest that the FUS1-mediated tumor suppression and bystander tumor cell killing may be facilitated by inhibiting PDGF/PDGFR signaling pathway. (supported by NIH/NCI Grants SPORE P50CA070907 and RO1CA116322) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 706.