Tissue microarray analysis of connexin-26 and Drg-1 in urinary bladder cancer
Authors: Loleta D. Harris, Tomas Tuziak, Jorge De La Cerda, Daniel Rosen, Lianchun Xiao, Yu Shen, Anita Sabichi, Bogdan Czerniak, H. Barton Grossman
Journal: Cancer Research (2006)

Proc Amer Assoc Cancer Res, Volume 47, 2006

920 

Tissue microarray analysis of Connexin-26 and Drg-1 in Bladder Cancer. Tissue microarrays (TMAs) are an excellent method to examine protein expression and to perform rapid profiling of molecular tumor markers. We have evaluated the expression of Cx-26 and Drg-1 on a TMA of bladder cancer specimens to determine the significance of these proteins in bladder cancer. Cx-26 is a component of the gap junction intercellular communication (GJIC) network. GJIC provides intercellular communication which is necessary for cell growth, proliferation and differentiation. The loss of expression of connexins and gap junction assembly has been found in a variety of cancers. Recent data suggests Cx-26 plays a role specifically in bladder carcinogenesis. Several human bladder cancer cell lines either lack or have low Cx-26 expression. Drg-1 is also implicated in cancer. Its function is relatively unknown, but it was found upregulated in differentiation induced colon cancer cells. Data suggests Drg-1 is regulated by the tumor-suppressor gene PTEN. Recent IHC analysis found that PTEN expression correlated with Drg-1 in prostate and breast cancers. We recently completed TMA analysis with PTEN and wanted to determine if this correlation also existed in bladder cancer. IHC probing of a TMA consisting of 251 human transitional cell carcinomas of the bladder was performed using antibodies to Cx-26 and Drg-1. Four tumor types were examined: nonpapillary invasive grade (G) 3, papillary invasive G3, papillary noninvasive G3, and papillary noninvasive G2. The slides were scanned and analyzed using Applied Images automated system and software. Both Cx-26 and Drg-1 had moderate expression in most of the four tumor types. The staining pattern of Cx-26 and Drg-1 was altered in the bladder cancer specimens. Cx-26 expression in normal urothelium was focused and punctate, whereas in cancer tissues the staining was diffuse throughout the cytoplasm. We found Drg-1 expression among some cancer specimens to be membraneous as well as cytoplasmic where there was only cytoplasmic staining in the normal urothelium. Among the tumor types, Drg-1 exhibited the lowest expression in nonpapillary invasive G3 (p<0.0001). The expression of Cx-26 was lower in papillary invasive G3 than in nonpapillary invasive (p=0.003). Our analysis also identified a moderate negative correlation between Cx-26 and Drg-1 expression (Spearman correlation coefficient = -0.19 (p=0.04)). However, we did not find a significant correlation between Drg-1 and PTEN. Survival analysis was performed and a Cox proportional hazards model including T-stage and Drg-1 as prognostic factors suggested that Drg-1 was a marginally significant predictor to recurrence free survival (HR=1.54, p=0.05). This tissue microarray analysis demonstrated that the expression of Cx-26 and Drg-1 are altered, suggesting that these molecules should be studied further to determine their role in bladder cancer progression.