Analysis of breast cancer cells under normoxic and hypoxic conditions showed that 128 Kcr sites were changed due to hypoxia, among which phosphoglycerate kinase 1 (PGK1) K131cr, K156cr, and K220cr were significantly reduced during hypoxia, PGK1 plays a crucial role in glycolysis by catalyzing the conversion of 1,3-diphosphoglycerate (1,3-BPG) and ADP to 3-phosphoglycerate (3-PG) and ATP, which is the first ATP-generating step. This evidence concerns the gene CLEC4F and breast cancer.