Colorectal cancer (CRC) is the second most common cause of cancer deaths in the United States. Current research is shifting the focus from chemotherapy to chemoprevention. The purpose of this study was to use combinations of chemopreventive agents (aspirin, calcium and folic acid) at low concentrations to evaluate synergistic effects on cell viability of two colon cancer cell lines used as surrogate biomarkers. Subsequently, these chemoprevetive agents were encapsulated into polymer nanoparticles for targeted delivery directly into the colon. Cell lines were tested according to published protocols. Briefly, upon 75-80% confluence, a measured amount of cells (5X103) were transferred into each well of a 96-well microplate and incubated with individual drugs or drug combinations for 24-48 h. Using an XTT assay method, cell viability was measured and synergistic effects were assessed based on the absorbance readings at 450 nm. Aspirin and folic acid nanoparticles were prepared using water/oil/water (w/o/w) emulsion processes of solvent evaporation, respectively. Particle size analysis was conducted. In vitro controlled release studies were carried out for aspirin nanoparticle formulations in silanized tubes wherein the nanoparticles were suspended and incubated in a simulated colonic environment, sampled at fixed intervals and replaced with fresh buffer. Results from studies in both SW-480 and HT-29 cell lines showed that dual combinations of chemopreventive agents exhibit synergistic efficacies at low concentrations in comparison with effects of individual agents. Aspirin (15 mM) when combined with calcium (30 mM) showed a 61% decrease in cell viability of SW-480 cells, as compared to the individual concentrations of the same agents after a 48 h incubation period. Similarly, aspirin (5mM) combined with folic acid (0.5 mM) and tested on SW-480 cell lines showed a 22% decrease in cell viability as compared to the individual concentrations after 24 h of incubation. With HT-29 cell lines, after 48 h incubation, aspirin (15 mM) and calcium (30 mM) showed a 52% decrease in cell viability. Results from formulation studies showed the size of aspirin and folic acid nanoparticles in polylactide-co-glycolide (PLGA) 50:50 co-polymer ranged from 111 - 122 nm. Encapsulation efficiency of aspirin and folic acid within the polymer nanoparticles was observed to be 83 - 91%. In vitro release studies showed approximately 60% encapsulated aspirin was released within the first 48 h. In conclusion, aspirin, folic acid and calcium are currently being investigated individually as chemopreventive agents in clinical trials. Significant synergism achieved by combining these agents and the ability to deliver them directly to the colon using nanotechnology provides a solid foundation for developing novel chemopreventive strategies in the fight against colon cancer.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA