Prognostic value of galectin-1 and galectin-3 expression in localized urothelial bladder cancer

Background: Galectin-1 (Gal-1) and Galectin-3 (Gal-3) are carbohydrate binding proteins with a wide range of biological activity, including regulation of cellular adhesion, proliferation, and apoptosis in solid tumors. Prior small studies have reported that Gal-3 expression is associated with progression of disease in urothelial carcinoma (UC), from non-muscle invasive UC progression to muscle invasive UC. We assessed Gal-1 and Gal-3 protein expression H-score utilizing a tissue microarray (TMA) created from 301 cystectomy specimens.

Methods: Immunohistochemistry for Gal-1 and Gal-3 was performed on TMA generated from tumor blocks from chemotherapy naïve cystectomy specimens. The variable of interest, H-score, was defined as the product of the percentage of cells staining positive (0-100) and intensity score (0-3) scored by a single pathologist. Survival end points were analyzed using Kaplan-Meier and Cox Proportional Hazards methods. Clinical data including Charlson Comorbidity Index (CCI), pathologic tumor (T) stage, tumor size, node stage, and surgical margins, were included in multivariable analysis.

Results: We found that Gal-1 and Gal-3 expression correlated with intratumoral T stage (median Gal-1 H-score was 0 across non-invasive tissue types and 200 in invasive, P<0.01 and median Gal-3 score was 270 across non-invasive tissue types and 70 in invasive, P<0.01). However, the highest intratumoral H-score per cystectomy core did not independently predict for recurrence-free survival (RFS) (Gal-1: HR =1.02, P=0.44, Gal-3: HR =1.01, P=0.65) or OS (Gal-1: HR =1.02, P=0.44, Gal-3: HR =1.01, P=0.72) in this cohort. Significant intratumoral heterogeneity was present for both Gal-1 and Gal-3, with an average difference between the highest and lowest H score was 95 for Gal-1 and 109 for Gal-3 for cystectomy specimens with more than one biopsy.

Conclusions: Gal-1 and Gal-3 H-score per bladder did not independently predict for RFS or OS. Intra-tumoral Gal-1/Gal-3 heterogeneity complicates the use of Gal-1 and Gal-3 expression as a prognostic biomarker. Future studies should consider the evaluation of serum and urinary galectins as an approach to mitigate tumor heterogeneity.