DKK1 and neoplasm: Intratumoral Ad-DKK1 injection into standard-sized tumors (approximately 100 mm3) significantly retarded tumor growth compared to Ad-Mock control construct-infected tumors [874 ± 162 vs. 2,277 ± 186 mm3, over 13 days of growth (p < 0.001)] (Fig. 1a, left panel).