Disclosed are novel methods for the therapeutic treatment of cancer and angiogenesis. The enzyme Ape1/Ref-1, via its redox function, enhances the DNA binding activity of transcription factors that are associated with the progression of cancer. The present disclosure describes the use of agents to selectively inhibit the redox function of Ape1/Ref-1 and thereby reduce tumor cell growth, survival, migration and metastasis. In addition, Ape1/Ref-1 inhibitory activity is shown to augment the therapeutic effects of other therapeutics and protect normal cells against toxicity. Further, Ape1/Ref-1 inhibition is shown to decrease angiogenesis, for use in the treatment of cancer as well other pathologic conditions of which altered angiogenesis is a component.