For example, studies on RCC have demonstrated that increased expression of matrix metalloproteinase-9 (MMP-9) or phosphorylated extracellular signal-regulated kinase (ERK) correspond to RCC severity, which is correlated with tumour size, TMN stage, invasion, distant metastasis, and cancer-specific survival [18,19]. The gene discussed is MMP9; the disease is renal cell carcinoma.