Following genetic manipulation and recombination with embryonic rat bladder mesenchyme, tissue recombinants were inserted underneath the renal capsule as described in materials and methods. a–d Hematoxylin and eosin staining of T24 cells engineered to stably express empty vector (a) or TFAP2A (b), empty vector (c) or TFAP2C (d). e–h Hematoxylin and eosin staining of UMUC3 cells engineered to stably express empty vector (e) or TFAP2A (f), empty vector (g) or TFAP2C (h). Overexpression of TFAP2A in T24 had no significant effect on tumor volume in the tissue recombination assay (i), while overexpression of TFAP2C significantly increased tumor volume of T24 recombinants (j). Overexpression of TFAP2A (k) and TFAP2C (l) significantly increased tumor volume of UMUC3 recombinants. Data are expressed as the medians ± S.D. *p < 0.05, **p < 0.01, ns: not significant, Mann–Whitney U test.