13086 Background: 101F6 is a candidate tumor suppressor gene on chromosome 3p21.3, a site of allele loss and genomic alterations were frequently found in many human cancers. We previously showed that enforced expression of wt-101F6 by adenoviral virus significantly inhibited tumor cell growth in 3p21.3-deficient NSCLC cells in vitro and in vivo. How 101F6 exerts this effect is largely unknown. Using a computer-aided structural and functional modeling, we recently identified 101F6 as a member of cytochrome b-561 protein family, which is involved in the regeneration of vitamin C. We hypothesized that under normal physiologic conditions, 101F6 protects cells from oxidative damage by regenerating antioxidant vitamin C and that in 101F6-deficient tumor cells, exogenous 101F6 facilitates vitamin C-mediated cytotoxic H2O2 formation. Methods and Results: We examined endogenous 101F6 expression in human NSCLC cell lines and tissue samples. All normal lung bronchial epithelial cells and fibroblasts but few lung cancers expressed 101F6. We investigated the combined effect of 101F6 and vitamin C on the cell growth: a nanoparticle-mediated wt-101F6 gene transfer plus a sub-pharmacologic concentration of vitamin C synergistically inhibited 3p21.3-deficient NSCLC cell growth but did not affect normal cell growth. We also used a human NSCLC H322 orthotopic lung tumor xenograft mouse model to evaluate the therapeutic efficacy of systemic injection of 101F6 nanoparticles and intraperitoneal injection of vitamin C. The growth of lung tumors was synergistically inhibited by the combination treatment (p<0.001). Furthermore, exogenous 101F6 promoted intracellular vitamin C uptake, leading to the vitamin C-mediated accumulation of H2O2 in the tumor cells, and these two agents synergistically killed the cells through caspase-independent apoptosis and autophagy cell death pathways. Conclusions: The synergistic and selective antitumor effect of 101F6 nanoparticles plus vitamin C may offer a useful tool for lung cancer prevention and intervention. This abstract is supported by grants from NCI (SPORE P50CA70907) and DOD (TARGET, DAMD17002–1-0706). No significant financial relationships to disclose.
The Neurofibromatosis Type 1 Tumor Suppressor Controls Cell Growth by Regulating Signal Transducer and Activator of Transcription-3 Activity In vitro and In vivo
