Effect of transforming growth factor α overexpression on urogenital organ development in mouse

Transforming growth factor-α (TGFα) promotes cell proliferation by binding to the epidermal growth factor receptor (EGFR). TGFα and EGFR overexpression have been reported in various human cancers. However, whether TGFα induces cancer by itself is unknown in urogenital organs. To investigate whether TGFα overexpression induces carcinogenesis in urogenital organs, we analyzed the phenotypes of urogenital organs in male TGFα transgenic (TG) mice of the CD1 strain. Urogenital organs including the kidney, bladder, prostate, seminal vesicles, testes, and epididymis were isolated from 4- to 48-week-old TGFα TG and wild-type (WT) CD1 mice. Prostates were separated into anterior prostate (AP), dorsolateral prostate (DLP), and ventral prostate (VP). Neither tumor formation nor epithelial hyperplasia was observed in the TGFα TG mouse urogenital organs that we have investigated. Histopathologically, in prostate, we found an increased number of p63-positive basal epithelial cells in the TGFα TG mice AP and DLP. There was no morphological change in the stromal component, such as hypercellular stroma or fibrosis. However, bladder weight was greater in TGFα TG mice than that in WT mice, and distended bladders were observed macroscopically in 19 of 20 TGFα TG mice over 20 weeks of age. Ki67 labeling index was increased significantly in the TGFα TG mouse urethral epithelium, whereas neither epithelial hyperplasia nor hypertrophy was observed. In conclusion, our results suggest that TGFα overexpression in mouse urogenital organs alone may not be responsible for tumor formation and epithelial hyperplasia, but is involved in bladder outlet obstruction.