HIGH EXPRESSION OF WNT7B IN HUMAN SUPERFICIAL BLADDER-CANCER VS INVASIVE BLADDER-CANCER

Aberrant Wnt gene expression is involved in the development of breast cancer, but its role in other tumours is unknown. Wnts regulate cadher in function, previously shown to be more commonly deregulated in invas ive bladder cancer. This study investigated whether factors upstream o f cadherins were aberrantly expressed in superficial bladder cancer. T he expression of one transforming (Wnt7b) and one non-transforming (Wn t5a) Wnt gene in four human bladder carcinoma cell lines, and in norma l human bladder tissues (n = 8) and bladder cancers (n = 48) were anal ysed by ribonuclease protection analysis. All cell lines expressed an approximately equal level of Wnt7b mRNA. Wnt5a and Wnt7b mRNAs were bo th expressed in normal bladder tissues and bladder tumours. The median expression of Wnt7b was fourfold higher in superficial tumours (n = 2 9) than in normal tissues (n = 8, P = 0.002) and five fold higher than in invasive tumours (n = 17, P = 0.003). There was no significant dif ference between normal tissues and invasive tumours (P = 0.3). The exp ression of Wnt5a did not vary significantly between normal tissues and superficial tumours (P = 0.4), normal tissues and invasive tumours (P = 0.3) or superficial tumours and invasive tumours (P = 0.2). The dif ferential expression of Wnt7b suggests a role in the early events of s uperficial bladder tumorigenesis involving cell adhesion and provides further evidence of different pathways of evolution of superficial and invasive cancer.