HIF1A and digestive system neoplasm: However, many studies have shown that although HIF-1α expression in some digestive system tumors shows no statistical differences in the GEPIA database; in fact, HIF-1α has been reported to be highly expressed in almost all malignant tumors of the digestive system and negatively correlated with survival time, which is far from the phenomenon described in the bioinformatics database (Table 1).