A human in vitro model of bladder tumour cell invasion.

To study invasion of transitional cell cancer three-dimensional coculture assay consisting of living human tissues has been developed. Multicellular spheroids initiated from an invasive human bladder tumour cell line (Hu-1703He) were confronted with precultured fragments derived from normal human bladder mucosa. The fragments consisted of a surface epithelium and a central stroma. An intact epithelium prevented adhesion of the tumour cells to the fragments. By removing the surface epithelium prior to confrontation, tumour cells rapidly adhered to, migrated on and invaded the bladder fragments. This process was demonstrated by an inverted confocal laser scanning microscope on live tissue pre-incubated with fluorescent dyes. The coculture model enables the study of factors regulating different steps of tumour invasion in human bladder.