Abstract 236: Antiproliferative and proapoptotic effects of (-)-epigallocatechin-3-gallate encapsulated in chitosan nanoparticles on human prostate carcinoma cells

In preclinical animal models (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol of green tea, has shown excellent effects in preventing and/or treating many cancers including prostate cancer (PCa). Chemoprevention is a practical approach for cancer management however its applicability to humans has met with limited success due to several issues including its limited bioavailability. We recently employed the use of nanotechnology to improve the outcome of natural agents for cancer chemoprevention and termed the concept as ‘nanochemoprevention’. To demonstrate the proof-of-principle we encapsulated EGCG in PLA-PEG nanoparticles and showed that this formulation demonstrates greater than ten-fold dose advantage over non-encapsulated EGCG in human PCa PC3 cells both in vitro and in vivo. However, this nanoformulation is not suitable for oral delivery. We recently reported the synthesis, characterization and efficacy assessment of a nanotechnology-based formulation of chitosan encapsulating EGCG (chit-nanoEGCG) for treatment of PCa in a xenograft model. We now show the efficacy of chit-nanoEGCG in LNCaP (androgen responsive) and PC3 (androgen unresponsive) human PCa cells for induction of apoptosis and inhibition of cell growth. The effective dose of EGCG for inhibiting cell growth was reduced significantly when encapsulated in chitosan nanoparticles. The IC50 of chit-nanoEGCG was observed to be 4 μM as compared to 90 μM with native EGCG in PC3 cells. For LNCaP cells the IC50 of chit-nanoEGCG was observed to be 1 μM as compared to 45 μM of native agent. Further, we also observed a significant inhibition in the colony formation potential of these cells when treated with low doses of chit-nanoEGCG (2-4 μM) at which native EGCG had no effect. Our next goal was to determine if EGCG encapsulated in this nanoformulation retains its mechanistic identity. Treatment of LNCaP and PC3 with chit-nanoEGCG (1 and 2 μM) and (4 and 6 μM), respectively, for 48 hrs as compared with native EGCG (40 and 50 μM) and (80 and 100 μM) resulted in significant: i) induction of poly (ADP-ribose) polymerases cleavage (PARP), ii) increase of protein expression of Bax with concomitant decrease in Bcl2 and, iii) activation of cleaved caspases 3,7,8,9. To further confirm the induction of apoptosis, we performed annexin/PI staining and observed significant presence of annexin positive cells in chit-nanoEGCG treated PC3 and LNCaP cells. Further, we also observed that chit-nano EGCG treat