Co-expression of mesothelin and CA125/MUC16 is a prognostic factor for breast cancer, especially in luminal-type breast cancer patients.

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 expression of mesothelin and CA125, and the clinicopathological meaning and prognosis of the co-expression of mesothelin and CA125 in breast cancer. Our results showed that 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 high correlation was observed between the expression of mesothelin and CA125 (P =0.0004). The co-expression of mesothelin and CA125 correlated with poor patient relapse-free survival (RFS) (P = 0.0001) and was identified as an independent predictor of RFS by Cox's multivariate analysis. In conclusion, this is the first to report the prognostic significance of the co-expression of mesothelin and CA125 in breast cancer. The co-expression of mesothelin and CA125 may be clinically useful for prognostication after surgical therapy in patients with breast cancer.