Fighting skin cancer with prodrugs

Skin cancer manifests itself in three forms: basal cell and squamous cell carcinomas or malignant melanoma. The carcinomas begin in the skin or in the cells that line internal organs. Basal cells are found in the lower part or base of the epidermis, the outer layer of the skin; squamous cells are found in the tissue that forms the surface of the skin. Malignant melanoma begins in the melanocytes, the pigment (melanin) producing cells which are evenly distributed in the basal epidermal layer of the skin (Fig 1) and which give skin its colour variations, including tanning and freckles. The prognosis for patients suffering from basal cell and squamous cell carcinomas is generally good, because these cancers rarely spread to other sites (metastasise) and form secondary tumours. Usually, the tumour is successfully removed by surgery and no chemotherapy is needed. In contrast, malignant melanoma readily spreads to secondary sites and is therefore much more difficult to treat effectively. During the early stages, diagnosis leads to treatment by surgical removal but at the moment there is no effective treatment for advanced stage melanoma so delayed diagnosis can be fatal. Although malignant melanoma accounts for just 10 per cent of all skin cancers (currently, around 132,000 melanoma skin cancers occur globally each year), it is responsible for more than 90 per cent of skin cancer deaths.¹