Abstract 3505: EGFR-targeted hybrid plasmonic magnetic nanoparticles induce autophagy and apoptosis through DNA damage in non-small cell lung cancer cells
Authors: Kuroda Shinji , Yokoyama Tomohisa , Tam Justina , Scott Ailing W. , Shanker Manish , Correa Arlene M. , Roth Jack A. , Sokolov Konstantin , Ramesh Rajagopal 
Published: February 2011

Nanoparticles represent a novel class of agents for cancer treatment. In the present study, we examined the effects of epidermal growth factor receptor (EGFR)-targeted hybrid plasmonic magnetic nanoparticles (NP) on non-small cell lung cancer (NSCLC) cells. The nanoparticles (NP) consisted of a paramagnetic iron core that is surrounded by a gold layer and is functionalized with monoclonal anti-EGFR antibody (C225) or control rabbit IgG antibody (IgG). The nanoparticles were tested against a panel of human lung cancer cells that were mutant (HCC827, H1819), wild-type (H1299) or null (H520) for EGFR and compared to EGFR-positive normal fibroblasts (MRC9, WI38) and normal human bronchial epithelial (NHBE) cells. Treatment of tumor cells with C225-NP resulted in a strong and significant inhibitory effect of cell growth compared to normal cells. C225-NP-mediated inhibitory effect was observed only in EGFR-positive tumor cells (HCC827, H1819, H1299) but not in EGFR-null H520 cells. EGFR-mutant cells (HCC827) were the most sensitive to C225-NP. No significant growth inhibitory effects were observed in IgG-NP-treated cells when compared to untreated cells. Molecular analysis showed C225-NP selectively inhibited phosphorylated p-EGFR protein expression and EGFR-mediated signal transduction resulting in induction of autophagy followed by apoptosis. Autophagy occurred as early as twenty-four hours after treatment with an increase in LC3-II content and autophagic vacuoles observed by Western blotting and electron microscopy respectively. Apoptosis as determined by flow cytometry and Western blotting showed an increase in the number of sub-G1 population cells and cleavage of caspase-3 and PARP in C225-NP-treated cells. Optical images determined by dark-field microscopy showed an increase in the concentration of C225-NP bound to EGFR-expressing NSCLC cells but not EGFR-null NSCLC cells. C225-NP exhibited 2-7 fold higher efficiency in induction of cell killing in comparison with the same amount of free C225 antibody. Free C225 antibody did not induce autophagy in cells. Investigation into how C225-NP but not C225 antibody or NP-alone triggers autophagy and initiates apoptosis showed induction of a DNA damage response as evidenced by the formation of γH2AX foci in C225-NP-treated cells. Minimal to no γH2AX foci were observed in cells that were untreated, treated with C225 antibody or NP-alone or treated with IgG-NP. Our data show that EGFR specific NP selectively induced cytotoxic effects in EGFR-expressing lung cancer cells via a novel cell-death mechanism that is not characteristic of the free antibody thus increasing efficacy of therapy.

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 3505.