The strong inhibitory effect of C-phycocyanin contained in Spirulina platensis protein extracts on the activity of human gelatinases MMP-2 (by 55.13%) and MMP-9 (by 57.9%) as well as the drop in the mRNA expression of both gelatinases has been documented in the hepatocellular cancer cell line HepG2. The gene discussed is MMP9; the disease is hepatocellular carcinoma.