By activating a transcription factor hypoxia-inducible factor 1 (HIF-1), cancer cells induce the expression of various genes responsible for not only the “adaptation of cellular metabolism to hypoxia (switch from oxidative to anoxic respiration) [53]”, “escape from hypoxia (invasion and metastasis of cancer cells) [49,54]”, and “improvement of severe hypoxic conditions (angiogenesis) [55,56]” but also “resistance to chemotherapy and radiation therapy”. This evidence concerns the gene HIF1A and cancer.