Induction of apoptosis in non-small cell lung cancer by downregulation of MDM2 using pH-responsive PMPC-b-PDPA/siRNA complex nanoparticles.

Non-small cell lung cancer (NSCLC) accounts for the majority of lung cancer caused human death. In this work, we selected oncogene mouse double minute 2 (MDM2) as a therapeutic target for NSCLC treatment and proposed that sufficient MDM2 knockdown could inhibit tumor growth via induction of cell cycle arrest and cancer cell apoptosis. On this regard, a new pH-responsive diblock copolymer of poly(methacryloyloxy ethyl phosphorylcholine)-block-poly(diisopropanolamine ethyl methacrylate) (PMPC-b-PDPA)/siRNA-MDM2 complex nanoparticle with minimized surface charge and suitable particle size was designed and developed for siRNA-MDM2 delivery in vitro and in vivo. The experimental results showed that the nanoparticles were spherical with particle size around 50 nm. MDM2 knockdown in p53 mutant NSCLC H2009 cells induced significant cell cycle arrest, apoptosis and growth inhibition through upregulation of p21 and activation of caspase-3. Furthermore, the growth of H2009 xenograft tumor in nude mice was inhibited via repeated injection of PMPC-b-PDPA/siRNA-MDM2 complex nanoparticles. These results suggested that PMPC-b-PDPA/siRNA complex nanoparticles targeting a unique set of oncogenes could be developed into a new therapeutic approach for NSCLC treatment.