Characterisation of duramycin as an anti-cancer agent

Broughton, Laura J.

Abstract

Duramycin is a relatively small (~2kDa) tetracyclic peptide that has a defined three-dimensional (3D) structure, this structure forms a stable binding pocket which specifically recognises the plasma membrane phospholipid phosphatidylethanolamine (PE). PE usually resides on the inner membrane layer though can become exposed on the outer membrane during physiological processes such as apoptotic cell death, cytokinesis and coagulation. Expression of cell surface PE has been observed on cancer cell lines, tumour endothelium and tumour-derived microparticles and observed in higher abundance in a variety of tumour xenografts compared to their normal tissue counterparts. There is a need in medical oncology for the development of novel, effective therapies and anti-cancer agents. A form of therapy that has gained interest is targeted anti-cancer therapy (TAT) which aims to bring about selective damage to tumour cells while limiting effect on surrounding normal tissue by utilising agents that recognise structures specific to tumours. Therefore, as duramycin had the potential to bind to PE exposed on cancer cell surfaces, it was theorised that it could be a promising targeted anti-cancer agent. Thus the aim of this project was to characterise duramycin’s anti-cancer properties and enhance its specificity to tumour cells. To achieve this a duramycin-porphyrin conjugate was developed as a novel photosensitiser and cancer cell lines were treated with photodynamic therapy (PDT). Duramycin was able to detect cell surface PE expression on cancer cell lines representing different cancer types including lymphoma, multiple myeloma and leukaemia and ovarian, pancreatic, breast and colon cancer. Duramycin was shown to have cytotoxic and anti-proliferative effects on cancer cell lines (ovarian and pancreatic), in both two-dimensional and 3D cell cultures, and a cytotoxic dose-dependent effect on a normal human endothelial cell line. Duramycin had been reported in the literature to have an effect on plasma membrane integrity and on a multitude of ion transport systems through the formation of membrane pores. Thus duramycin’s effect on cancer cell membranes was investigated along with a focus on whether the cytotoxic effect observed in the cancer cell lines was due to a form of calcium ion (Ca²⁺) overload. It was shown that duramycin treatment resulted in a concentration-dependent rise in intracellular Ca²⁺ concentration in cancer cell lines. The duramycin-porphyrin conjugate plus PDT light irradiation reduced cell proliferation of ovarian and pancreatic cancer cell lines in a dose-dependent manner and had a significantly enhanced effect over unconjugated duramycin and the free porphyrin. A preliminary investigation into the effect of duramycin-PDT treatment on tumour xenografts on the chorioallantoic membrane (CAM) of fertilised chicken eggs was undertaken with promising results. In summary, duramycin was shown to be an effective anti-cancer agent and was applicable to the PDT treatment of cancer in vitro and in a low level-in vivo tumour model and thus merits further studies.

Citation

Broughton, L. J. (2016). Characterisation of duramycin as an anti-cancer agent. (Thesis). Hull York Medical School, the University of Hull and the University of York. Retrieved from https://hull-repository.worktribe.com/output/4219417

• Thesis Type: Thesis
• Deposit Date: Jul 4, 2017
• Publicly Available Date: Feb 23, 2023
• Keywords: Medicine
• Public URL: https://hull-repository.worktribe.com/output/4219417
• Additional Information: Hull York Medical School, The University of Hull and University of York
• Award Date: Dec 1, 2016