Abstract 2200: Omega-3 fatty acid conjugated paclitaxel dendrimers exhibit enhanced anticancer activity in various preclinical models of gastrointestinal cancers
Authors: Dichwalkar Tanmay , Bapat Samhita , Pancholi Priya , Yellepeddi V. K. , Sehdev Vikas 
Published: July 2016

Abstract
Background: Paclitaxel (PTX) is frequently used for the treatment of advanced gastrointestinal (GI) cancers. However, development of drug resistance, dose-dependent toxicity, and lack of oral bioavailability are some of the major limiting factors that impede the therapeutic use of PTX for treatment of GI cancers. Drug conjugates of dendrimers, such as poly (amidoamine) (PAMAM), have been reported to effectively overcome bioavailability and dose-dependent toxicity related limitations. Therefore, in this study we synthesized and investigated the anticancer potential of omega-3 fatty acid [docosahexanoic acid (DHA)]-poly (amido)amine (PAMAM)-paclitaxel conjugates in various in vitro models of gastrointestinal cancers. Methods: DHA was conjugated to amine-terminated PAMAMG4 dendrimers using coupling agents HOBt and HBTU. PAMAMG4-DHA was then conjugated to PTX using PTX-NHS-ester. The conjugates were purified by size exclusion chromatography and characterized using 1H-NMR, MALDI-TOF-MS and high-resolution ESI-MS. The percentage payload of PTX conjugated to PAMAMG4-DHA and in vitro stability of PAMAMG4-DHA-PTX were evaluated using HPLC. Cell viability, clonogenic cell survival, and western blot analyses were done to evaluate the cell viability, survival, and induction of apoptotic proteins (P53 and P21), respectively. The in vitro cytotoxicity and induction of apoptosis was investigated in AGS, FLO-1, and MIA PaCa-2 GI cancer cell lines after treatment with PTX or PAMAMG4-DHA-PTX. Results: The 1H-NMR, MALDI-TOF and high-resolution ESI mass spectra confirmed the conjugation of DHA to PAMAM and PTX to PAMAM-DHA. The in vitro stability data showed that PAMAM-DHA-PTX conjugate was stable in human plasma for 24 hours. The cell viability data indicated that treatment with PAMAMG4-DHA-PTX is significantly more potent than PTX at inhibiting proliferation of esophageal (FLO-1: PTX IC50: 3.8±0.68 nM, PAMAMG4-DHA-PTX IC50: 1.1±0.17 nM), gastric (AGS: PTX IC50: 5.1±0.58 nM, PAMAMG4-DHA-PTX IC50: 1.4±0.23 nM), and pancreatic (MIA PaCa: PTX IC50: 5.1±0.75 nM, PAMAMG4-DHA-PTX IC50: 1.8±0.35 nM) cancer cell lines. The clonogenic cell survival data shows a similar activity where treatment with PAMAMG4-DHA-PTX exhibited enhanced inhibition of long term survival of FLO-1, AGS, and MIA PaCa cells when compared to PTX. The protein expression data further showed that compared to PTX treatment with PAMAMG4-DHA-PTX induced higher expression of P53 and P21 pro-apoptotic protein in AGS gastric cancer cell line. Conclusions: Overall our findings indicate that paclitaxel was successfully conjugated with PAMAMG4-DHA resulting in the synthesis of a novel PAMAMG4-DHA-PTX conjugate that exhibits enhanced anticancer activity than PTX alone in various in vitro models of GI cancers.
Citation Format: Tanmay Dichwalkar, Samhita Bapat, Priya Pancholi, V. K. Yellepeddi, Vikas Sehdev. Omega-3 fatty acid conjugated paclitaxel dendrimers exhibit enhanced anticancer activity in various preclinical models of gastrointestinal cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2200.