From viruses to cancer stem cells: dissecting the pathways to malignancy

Cancer is a disease of all vertebrate species and has been well documented throughout history with fossil records indicating that dinosaurs of the Jurassic period suffered from the disease. The Greek physician, Galen is accredited with describing human tumours as having the shape of a crab, with leg like tendrils invading deep into surrounding tissues--hence the term cancer. Today cancer can be defined as any malignant growth or tumour caused by abnormal and uncontrolled cell division that is able to invade tissues locally and spread to other parts of the body through the lymphatic system or the blood stream. This is obviously a simplistic attempt at describing a complex disease that can utilize a myriad of biological pathways to sustain growth and proliferation. Dissecting these pathways has been the challenge of cancer researchers for decades in the search for new treatment strategies. This review attempts to condense our understanding of cancer and to offer insights into an alternative theory regarding the existence of true cancer stem cells and how this will inform the development of new therapeutics.