Preconditioning methods influence tumor property in an orthotopic bladder urothelial carcinoma rat model.

Urothelial carcinoma (UC) is an extremely common type of cancer that occurs in the bladder. It has a particularly high rate of recurrence. Therefore, preclinical studies using animal models are essential to determine effective forms of treatment. In the present study, in order to establish an ortho- topic bladder UC animal model with clinical relevance, the effects of preconditioning methods on properties of the devel- oped tumor were evaluated. The bladder cavity was pretreated with phosphate-buffered saline (PBS), acid‑base, trypsin (TRY) or poly (L‑lysine) (PLL) and then rat UC cells (AY‑27) (4x10 6 cells) were inoculated. The results demonstrated that, two weeks later, the tumorigenic rate (88%) and tumor count (2.3 per rat) were not significantly different among the precon- ditioning methods, whereas tumor volume and invasion depth into bladder tissue were significantly different. Average tumor volumes were >50 mm 3 in the PBS and acid‑base‑treated groups and <10 mm 3 in the TRY- and PLL‑treated groups. The percentage of invasive tumors (T2 or more advanced stage) was ~75% of total tumors in the PBS- and acid‑base‑treated groups, whereas the percentages were reduced in the TRY- and PLL‑treated groups (58 and 32%, respectively). Non-invasive tumors (Ta or T1) accounted for 54% of tumors in the PLL‑treated group, which was 2‑5‑fold higher than the percentages in the remaining groups. Properties of the devel- oped tumor in the rat orthotopic UC model were different depending on preconditioning methods. Therefore, different animal models suitable for a discrete preclinical examination may be established by using the appropriate preconditioning condition.