Effects of Cortactin Expression on Prognosis in Patients with Breast Cancer

Background: Cortactin is overexpressed in several types of invasive cancers. However, the role of cortactin expression in breast cancer prognosis has not been sufficiently elucidated. Therefore, we investigated the clinicopathological significance of cortactin in breast cancer. Methods: Tissue microarrays were prepared from a cohort of 506 patients with breast cancer, and cortactin expression was evaluated using immunohistochemistry. The cortactin immunoreactivity score (IRS) was quantified as the product of the intensity score and the percentage of immunoreactive cells. Cortactin expression was classified as low or high using the IRS (IRS ≤ 4 as a cortactin-low value and IRS > 4 as a cortactin-high value). We compared cortactin expression and clinicopathological factors according to the molecular subtypes of breast cancer. Results: Of 506 breast cancer cases, 333 and 173 showed high and low cortactin expression, respectively. Of the 333 patients with high cortactin expression, 204, 58, and 71 had luminal, HER2, and triple-negative breast cancer (TNBC), respectively. In the univariate and multivariate analyses of patients with TNBC, cortactin expression was found to be a significant prognostic factor for overall survival (OS). However, in all patients with non-TNBC, cortactin expression had no significant association with prognosis or overall survival. Survival curves revealed that among patients with TNBC, the high-cortactin group had a better prognosis in disease-free survival and OS. Conclusions: Cortactin expression may be a good biomarker for predicting the prognosis of patients with TNBC.