UBC and neoplasm: All remnant tumors (6 of 6; 100%) that we reviewed in immune-competent BALB/cBy mice had detectable CK18+ tumor cell foci (Fig. 2A, inset 1), whereas only 2 of 6 (33%) UBC-GFP mice contained any remaining tumor cells (p = 0.06, Fisher exact test, two-tailed).