Patterns of spread in an orthotopic mouse model of bladder cancer

Purpose: To develop an orthotopic model of muscle‐invasive transitional cell carcinoma (TCC) of the bladder which models primary tumour growth and metastasis.Methodology: Cell lines were derived from the TCC cell line T24 (Tsu‐Pr1) using in vivo selection for metastatic ability (Chaffer et al. Clin Exp Metastasis 2005; 22(2): 115–25). Each of these cell lines (Tsu‐Pr1 and sub‐lines, B1 and B2) was then injected intramurally into the mouse bladder wall (n = 25 × 3). The cell lines were also injected intravesically and intraperitoneally (n = 15 × 3 in each group).Results: There were no differences between the three sub‐lines in primary tumour formation, presence of macroscopic metastases and survival. This model produced more macroscopic and lymph node metastases in comparison with other orthotopic models reported in the literature. After intraperitoneal injection, the B2 cell line produced a higher number of discrete intra‐abdominal masses in comparison with the parental line. This is likely to be related to the phenotype of the cells with parental cells being more mesenchymal, versus the B2 sub‐line, which has more epithelial characteristics.Conclusion: The TSU‐Pr1 series is a useful, clinically relevant model of muscle‐invasive TCC. In addition, this model may also provide insights into the role of mesenchymal‐epithelial transition in the metastatic process.