Abstract 2102: Nanochemoprevention: Introducing a novel concept in cancer chemoprevention with a proof of principle for superior activity of green tea polyphenol epigallocatechin-3-gallate encapsulated in PLGA/PVA nanoparticles

Abstract

Abstract Despite extensive efforts that have been put to prevent cancer through chemoprevention, lack of delivery of desired levels of bioactive agents thus limiting their bioavailability, remains a challenging issue for effective clinical outcome. Thus, there is a strong unmet need in the biomedical technology community to find novel tools for making chemoprevention a success. Because most biological processes including those that are cancer-related occur at nanoscale, nanoparticulate technology has emerged as a potential tool to diagnose and treat cancer. We considered that nanoparticulate technology can prove to be very useful in cancer chemoprevention by allowing for effective and targeted delivery of chemopreventive agents. This delivery system could overcome many biological, biophysical and biomedical barriers that the body stages. Here, for the first time we introduce a concept of ‘nanochemoprevention’. To demonstrate the proof of principle we selected green tea polyphenol epigallocatechin-3-gallate (EGCG) with which we have considerable experience. We encapsulated EGCG in Poly (DL-lactide-co-glycolide acid) (PLGA)/Polyvinyl alcohol (PVA) nanoparticles, hereafter referred to as nano-EGCG, and evaluated it for cytotoxic response against human prostate cancer (PCa) PC3, DU145, 22Rν1 and LNCaP cells. MTT assay showed that treatment of cells with PLGA/PVC nanoparticles alone had negligible effect on cell growth. Interestingly, nano-EGCG, compared to EGCG in PBS, produced remarkably superior effects. For PC3 cells, the IC50 value at 24 hours of nano-EGCG was 3.75 μM compared to 40 μM of EGCG in PBS; 3.75 μM of EGCG in PBS had no effect. These differential effects were persistent at 48 and 72 hours. Similar effects of nano-EGCG were observed in 22Rν1, LNCaP and DU145, other human PCa cells. EGCG in PBS treatment to cells is known to result in induction of apoptosis and inhibition of colony formation which is considered essential for its chemopreventive effects. Next series of experiments were conducted to determine the effect of nano-EGCG on apoptosis and colony formation potential of PC3 cells. Treatment of the cells for 48 hours with nano-EGCG led to significant induction of PARP cleavage in a dose dependent manner and modulation of bax and bcl2 ratio that favored apoptosis. Further, nano-EGCG treatment also led to a dramatic increase in the levels of annexin V, an early marker of apoptosis. We then performed a 2-dimensional colony formation assay to evaluate the effect of nano-EGCG on the cellular growth pattern of PC3 cells and observed a marked decrease in colony number. Validation of these cell culture data to animal model systems could pave way for developing new avenues for cancer chemoprevention.