HIF1A and esophageal cancer: The expression of TWIST1 and other functionally related genes, such as E-Cad, SNAIL, SLUG and HIF-1α, has also been studied in relation to survival in several tumor types, such as esophageal cancer [31], head and neck [32], [33] and bladder [34] carcinoma, with these relationships increasing when any of these genes are also overexpressed, as well as TWIST1. It is possible that a stage-by-stage analysis in some of these series would also provide results similar to ours.