MKI67 and neoplasm: To determine the underlying molecular basis by which DFE inhibited the C4-2 tumor burdens in mice, immunohistochemical (IHC) staining of c-caspase-3 (a marker of apoptosis) and Ki67 (a marker of cell proliferation) in C4-2 tumor specimens collected from the DFE-treated and the vehicle control mice was performed.