Mechanism for the reduction of tumour hypoxia by nicotinamide and the clinical relevance for radiotherapy.

Nicotinamide (1000 mg/kg; i.p.) enhanced the radiation response of the SCCVII tumour, producing an ER of almost 1.5 in a growth delay assay. Separating tumour cells as a function of fluorescent labelling with Hoechst 33342, suggested that this enhancement may be primarily a result of the elimination of acutely hypoxic cells in tumours. Nicotinamide also decreased mean arterial blood pressure in mice. These results are discussed with respect to their clinical applicability.