ABSTRACT
Radiation and cell kill Ionising radiation causes wide-ranging molecular damage throughout cells by the production of ionised atoms, which cause breakage of chemical bonds, production of free radicals and damage to DNA. Most clinically significant effects of radiotherapy are due to irreparable DNA lesions which result in sterilisation – a loss of proliferative cells’ ability for sustained cell division. In tumours, loss of proliferative ability by all the cells of the tumour is a necessary condition for tumour cure. Partial sterilisation of the tumour cell population results in tumour stasis or regression, giving a clinical remission, followed by regrowth of the tumour from those cells which have retained their proliferative ability. In self-renewing normal tissues, sterilisation of proliferative cells leaves the tissues unable to provide replacements for cells that are ordinarily being lost at a constant rate from the tissue, and initiates a rundown of the mature cells of the tissue. Proliferative sterilisation is often referred to as cell kill, with those cells that retain long-term proliferative ability being described as survivors.
