Purpose: Connexin 26 is the major gap junction protein in urothelial and mammary epithelial cells, and a putative tumor suppressor gene. We evaluated connexin 26 expression in normal urothelium and in bladder cancer.
Materials and methods: A total of 40 formalin fixed, paraffin embedded bladder tumors and 5 normal urothelial specimens were analyzed by immunohistochemistry. Two observers visually scored connexin 26 expression in these specimens.
Results: Normal urothelium expressed connexin 26 in a punctate staining pattern with limited expression in the basal layer. Decreased connexin 26 expression was observed in 28 of 40 tumors (70%). Connexin 26 was diffusely expressed in 5 of 18 low grade, noninvasive tumors (28%), whereas loss of expression was observed in heterogeneous (30% to 70% positive staining) or extensive (less than 30% positive staining) fashion in 8 (44%) and 5 (28%), respectively. Seven of 22 high grade or invasive tumors (32%) showed diffuse connexin 26 expression, whereas expression was decreased in a heterogeneous or extensive pattern in 9 (41%) and 6 (27%), respectively. Intracytoplasmic localization of connexin 26 was also observed.
Conclusions: Expression of connexin 26 is altered in bladder cancer. These aberrant patterns of connexin 26 expression may contribute to the malignant phenotype of this disease.