Connexin 26 is abnormally expressed in bladder cancer.

Abstract

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. 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. 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. 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.