Low pH activates and triggers the secretion of proteolytic enzymes including matrix metalloproteinase‐2 (MMP‐2), MMP‐9, a tissue serine protease, adamalysin‐related membrane protease, cysteine protease, cathepsin and gelatinase leading to the degradation and remodelling of ECM, so as to promote tumour invasion and progression.72 Here, MMP2 is linked to neoplasm.