Modification of the hypoxic fraction of a xenografted human colon tumor by differentiation-inducing agents.

Xenografted tumors were produced in nude mice by injection of HCT-15 human colon tumor cells. The hypoxic fractions of control tumors as determined from x-ray survival curves were approximately 18%. Other tumors were treated (every day X 9) with daily injections of N-methylformamide (150 mg/kg) or sodium butyrate (2,000 mg/kg). For both agents, it was found that the hypoxic fractions were less than 0.05% and less than 1.7%, respectively. These data indicate that selected differentiation-inducing agents could be of value for treatment of human solid tumors that contain hypoxic cells.