MMP9 and hepatocellular carcinoma: Given that IL-8 upregulates the expression of genes involved in tumor growth (EGFR, MMP2, MMP9), angiogenesis (VEGF), and cell proliferation through a metalloproteinase dependent pathway [32–34, 55, 56], its activation at 12 months post 56Fe and16O irradiation is in line with the tumor growth and spontaneous incidences of HCC seen previously [4, 32–34, 56].