A Reduced Oxygen Enhancement Ratio for X-ray Survival of HeLa Cells in vitro, after Treatment with ‘Methotrexate’

Abstract

THE importance of anoxic cells within human tumours as a potential cause of failure when these tumours are treated by X- or γ-ray therapy has been realized for more than ten years^1,2. Clinical attempts have been made to render all tumour cells well-oxygenated by irradiating patients while they are breathing pure oxygen under increased pressure in a tank, and radiations of higher ionization density such as some fast neutrons, which are relatively independent in their effects of the presence or absence of oxygen, have passed the stage of preliminary trials^3,4. A similar clinical result, however, might be obtained by using a chemical modifier of radiation effects which produced greater potentiation of X-ray cell-killing under anoxic conditions than under well-oxygenated conditions⁵.