Combination of nitric oxide and polymer based drug delivery system to improve the effectiveness of a peptide inhibitor in cancer therapy outcomes

The recent development in the field of nanotechnology offers the opportunity to alter the pharmacokinetic profiles of drugs, reducing off-target toxicity and improving therapeutic index, and ultimately patient outcome. This study aims to use a biodegradable and biocompatible material which is a modified form of the glucose polymer ‘dextran’. Aldehyde-functionalised dextran is the oxidised form of dextran to introduce aldehyde functionality for stably chemical loading therapeutic agents for its potential application in cancer treatment. Cancer is a heterogeneous disease caused by the progressive accumulation of genetic mutations in many biological processes such as apoptosis, cell cycle, cell growth and metabolic activities. Developing new therapies for cancer treatment to reduce the mortality rate is of utmost importance. Recently, cyclo-((2-Nal)-Leu-Ser-(2-Nal)-Arg) acetate pentapeptide (c2) which inhibits the enzyme involved in prostaglandin pathway has been implicated in glioblastoma, breast and prostate cancer therapy. It has passed clinical trials however poses bioavailability issues. This project addressed the solubility issue of c2 which was improved greatly using dextran-based platform as a nanocarrier system. In addition, to improve cytotoxic response of c2 in vitro, for the first time c2 was doped with small molecule nitric oxide donor (c2-NO). This project also explored the synergistic effects of c2 loaded dextran nanoparticles and nitric oxide donor molecules (c2-NO-DEX-CHO) in the treatment of glioblastoma, prostate and breast cancer cells using 2D monolayer and 3D tumor spheroids. The cytotoxicity was also assessed on the normal fetal lung fibroblast cells. In monolayers, cell viability was assessed using Alamar blue assay. Results showed a significant decrease in cell viability at higher concentrations for prostate, breast and brain cancer cell lines treated with c2 encapsulated dextran nanocarriers compared to c2 only. Moreover, there was a great reduction in cell viability and IC50 values for cells treated with c2 doped nitric oxide donor molecules and the combination of c2 conjugated dextran nanocarriers with nitric oxide compared to free c2 in glioblastoma, prostate and breast cells. This suggests that our novel formulations of modified c2 and its conjugated forms with dextran and nitric oxide donor were effective in improving its cytotoxicity in cell monolayers. The formulations were further assessed in 3D tumor spheroids, as a representative model for the tumor microenvironment over a period of 9 days. In MCF-7 tumor spheroids, a decrease in diameter was observed on day 9 with these novel formulations compared to untreated spheroids. In glioblastoma U87MG cells, the spheroid diameter gradually decreased in c2-NO and c2-NO-DEX-CHO treated cells compared to untreated cells. This shows that drug after being encapsulated in a polymeric dextran nanocarrier along with nitric oxide donor modification has been able to successfully reduce the tumor (size) meshwork and enhance its antitumor activity