We propose that the growth profiles observed in the HIF-1+ and HIF-2+ tumors that we have studied may be mediated by HIF-1α inhibition of the c-Myc oncoprotein (slowing HIF-1+ growth) whilst HIF-2α potentiates c-Myc transcriptional activity (HIF-2+) and promotes tumor growth by an adaptive change to a more oxidative phenotype. This evidence concerns the gene EPAS1 and neoplasm.