Abstract 3697: Inhibition of melanoma cell growth in vitro and in vivo by (−)-Epigallocatechin-3-gallate encapsulated in chitosan nanoparticles

We recently introduced a novel concept of nanochemoprevention (Cancer Res. 2009; 69(5): 1712-6.) by providing evidence of a dose advantage of PLA/PEG nanoparticles encapsulating green tea polyphenol epigallocatechin-3-galle (EGCG). We now developed a delivery system suitable for oral ingestion by employing a naturally occurring polymer ‘chitosan’ to nanoencapsulate EGCG (hereafter referred to as nano-EGCG). We first determined release kinetics of EGCG from nano-EGCG using simulated gastric and intestinal fluids. The data suggested that EGCG release peaked at 2 hours with 50% release in the intestinal fluid and 30% release in the gastric juice and the percent release thereafter was maintained at constant levels suggesting a sustained release phenomenon. Furthermore to ascertain oral bioavailability of EGCG, blood samples were collected from mice treated with EGCG and nano-EGCG and the levels of EGCG were determined. We observed a steady and sustained release of EGCG in the plasma of mice treated with nano-EGCG; detailed analysis indicated a significant longer half-life compared to non-encapsulated EGCG. Next, we determined the usefulness of this unique formulated nano-EGCG for its cytotoxic response against human melanoma Mel 928 cells in vitro. Data obtained showed that the cells treated with nano-EGCG produce remarkably superior cell growth inhibition with an IC50 of 2.0 μM compared to 50 μM when delivered in PBS. We next determined whether EGCG retains its mechanistic identity following encapsulation in chitosan nanoparticles. Treatment with nano-EGCG (1, 2 and 4 μM) to the Mel 928 cells resulted in a dose dependent (i) shift in Bax/Bcl-2 ratio in favor of apoptosis, (ii) increase in PARP cleavage, (iii) inhibition in caspase 3 and 9, (iv) marked induction of p21 and p27, and (v) s-phase cell cycle arrest. In sharp contrast, doses up to 10 μM of EGCG delivered in PBS were without any effect on any of these responses. Next, to establish the in vivo relevance of in vitro data, we compared the effect of nano-EGCG (100 μg/mouse) and EGCG in PBS (1 mg/mouse) on the growth of tumor xenografts implanted in nude mice. Data obtained demonstrated that at ∼21 days post-inoculation, the tumor volume in control mice was 1433 mm3 whereas in both treatment groups, a significant decrease in the tumor volume was observed (non-encapsulated EGCG, 834 mm3; nano-EGCG, 602 mm3). The time for tumors to reach the targeted volume of 1400 mm3 was significantly increased (non-encapsulated EGCG, 27 days; nano-EGCG, 32 days). These data confirm that to achieve similar tumor growth inhibition 10-fold lower dose of nano-EGCG was sufficient compared to that by non-encapsulated EGCG. Administration of these agents was also found to inhibit proliferation and induce apoptosis in tumors harvested from the treated mice. These observations warrant further in vivo efficacy studies in robust animal models of human melanoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3697. doi:10.1158/1538-7445.AM2011-3697