HIF1A and cancer: Previously, we proposed the concept that three major transcription factors, SP1, HIF1A, and MYC, collaborated together to promote the development of cancers, based on comprehensive investigations of various system analyses of cancer-related genes and promoter analyses of the SP1, MYC, and HIF1A genes, and that combination treatment with inhibitors of SP1, HIF1A, and MYC should suppress the expression of various genes associated with the regulation of cancer stem cells, which have key roles in the maintenance and progression of cancer cells, and should induce strong anticancer activity [15].