The overexpression of both inorganic pyrophosphatase (PPA1) and tubulin α1c (TUBA1C) in response to the variation of exogenous zinc in MCF-7 cells (Table 1) suggests that high intracellular zinc promotes the metabolic activity of breast cancer cells, since inorganic pyrophosphatase is involved in cell metabolism, and tubulin α1c promotes glycolysis in breast cancer [75–77]. Here, PPA1 is linked to breast cancer.