Professor Roger Reddel has made major contributions to the understanding of cellular immortalisation, a hallmark of cancer and potential target for novel anti-cancer therapeutics. He is known for discoveries regarding the role of the tumour suppressor proteins, p53, and p16INK4a, in immortalisation, and for studies of telomerase, including purification and mass spectroscopic analysis of its components. Dr Reddel and his team are best known for discovering the DNA recombination-based Alternative Lengthening of Telomeres (ALT) mechanism in human cell lines and tumours, and for a substantial body of work analysing its mechanism and significance in cancer.