Co-expression of Mesothelin and CA125/MUC16 Is a Prognostic Factor for Breast Cancer

Abstract Background: The expression of mesothelin correlates with a poor prognosis in patients with breast cancer. Since mesothelin plays a role in cancer metastasis in association with CA125, we herein examined the clinicopathological significance and prognostic implications of the co-expression of mesothelin and CA125 in breast cancer. Methods: The expression of mesothelin and CA125 was immunohistochemically examined in tissue samples collected from 478 breast cancer patients. The expression of these two molecules in more than 1% of tumor cells was defined as positive. The relationships between the co-expression of mesothelin and CA125, clinicopathological parameters, and clinical outcomes were analyzed by the chi-squared test and Cox’s univariate and multivariate proportional hazard model analyses. Results: Among 478 patients, mesothelin and CA125 were co-expressed in 48 (10%), mesothelin only in 75 (16%), CA125 only in 217 (45%), and neither in 234 (49%). A strong correlation was observed between the expression of mesothelin and CA125 (P =0.0004). The co-expression of mesothelin and CA125 correlated with unfavorable patient relapse-free survival (RFS) (P = 0.0001) and was identified as an independent predictor of RFS by Cox’s multivariate analysis. Conclusion: This is the first study to demonstrate the prognostic significance of the co-expression of mesothelin and CA125 in breast cancer. The co-expression of these two molecules may play a significant role in the acquisition of aggressive clinical behavior.