Selective delivery of arsenic trioxide to HPV positive cervical cancer cells with targeted liposomes

Infection with high risk human papilloma viruses (HPVs) is directly associated with the occurrence and development of cervical cancer, however, currently there is no specific anti-HPV drug available for cancer treatment. Arsenic trioxide (ATO) has been shown to induce apoptosis in HPV-infected cervical cancer cells in vitro but its wider clinical applications have been compromised by its toxicity and poor pharmacokinetics. This research explores an optimized drug delivery system for ATO using liposomal nanotechnology with the aim of enhancing its potential as a cervical cancer treatment. The size and surface charge of liposomes were optimised and 100nm neutral liposomes demonstrated maximum stability, least intrinsic toxicity and highest loading efficiency among all the tested formulations. Furthermore, both free and chosen liposomal-ATO were exposed to two cervical cancer cell lines (HeLa and HT-3, with and without HPV) and control cells. Liposomal-ATO was most effective in inducing toxic response in HPV+ ve HeLa cells, followed by HT-3 and control cells. These cells were then screened for different surface markers in order to identify the best ligand for selectively targeting HPV positive cells. Folate receptor (FR) was found as the most abundantly expressed receptor on HeLa cells, therefore, folic acid (FA) was chosen as the targeting ligand. FA-liposomal-ATO were synthesised by linking liposomal-ATO to FA using 5000kDa PEG spacer, which was shown to be most efficient and specific in enhancing the cellular uptake of ATO in FR positive cells. Finally, FA-liposomal-ATO were examined for their effectiveness in reducing HPV oncogenes and the possible mechanisms. Results showed that FA-liposomal-ATO induced higher cell death in HPV cells than free ATO per unit arsenic and also demonstrated higher selectivity and efficiency in inducing cell apoptosis, downregulating oncogenes and upregulating the tumour suppressors in HPV positive cells. These findings provide a promising therapeutic strategy in managing HPV-associated cancers.