489. Tumor-Targeted Hursirna-Nanoparticle Delivery Inhibits Lung Tumor Growth In Vitro and In Vivo

HuR, an mRNA binding protein regulates the stability of many oncoproteins associated with cell survival, proliferation, migration and angiogenesis. HuR overexpression is a marker for poor prognosis in patients diagnosed with cancer of lung, ovary, breast and colon. We hypothesized that the silencing of HuR using small interfering RNA (siRNA) could be a promising approach for lung cancer therapy. To test our hypothesis, we developed a tumor-targeted nanoparticle (NP) system that is targeted to transferrin receptor (TfR) for delivering HuRsiRNA (HuR-TfNP) in human lung cancer cells. Human lung cancer cells (A549, HCC827) and normal lung fibroblast (MRC-9) cell lines expressing varying levels of TfR were used in the present study. TfR expression was highest in A549, moderate in HCC827, and low to undetectable in MRC9 cells. In vitro studies demonstrated enhanced uptake of Tf-NP (51%) in TfR overexpressing A549 cells, compared to the non-targeted NP. Specificity studies using desferrioxamine (DFO; 100 µM), a stimulator of TfR, showed a two-fold increased uptake of Tf-NP whereas blocking TfR with exogenous transferrin (1 µg/well) reduced the uptake by 3 fold in A549 cells. Further, HuR-TfNP treatment reduced HuR expression and significantly suppressed cell proliferation at 24h and 48h compared to control siRNA containing NP (C-Tf-NP) in tumor cells but not in normal cells. Greatest inhibition was observed in A549 cells (23% and 30% inhibition at 24 and 48 h respectively) compared to 15% and 25% in HCC827. In MRC-9 cells, only 4% inhibition was observed. HuR-TfNP induced G1 cell-cycle arrest in tumor cells that correlated with marked reduction in Cyclin D1, and Cyclin E protein expression. Further, tumor cell migration and invasion was significantly inhibited in HuR-TfNP treated tumor cells compared to C-TfNP treatment (pu003c0.001). In-vivo, Tf-NP bio-distribution studies using indocyanine green (ICG) showed accumulation of the NP in tumor tissues over time with maximum accumulation at 24 h post NP injection. Efficacy studies in A549 tumor model demonstrated that systemic administration of HuR-TfNP significantly inhibited growth of both subcutaneous tumor growth and experimental lung metastasis compared to C-TfNP treatment (Pu003c0.05). Further, tumor growth delay was sustained over 70 days when compared to control groups. A marked reduction in the expression of HuR and HuR-regulated oncoproteins (Bcl2, Cyclin D1 and Cyclin E) with a concomitant increase in p27 expression was observed in HuR-TfNP-treated tumors compared to control tumors. Our study results demonstrate HuR-TfNP therapy suppressed lung tumor growth both in vitro and in vivo and is therapeutic target for lung cancer treatment.