High expression of endoglin in primary breast cancer may predict response to neoadjuvant chemotherapy.

Neoadjuvant chemotherapy (NAC) is a widely‑used treatment for breast cancer, as it may render unresecta-ble breast tumors to become resectable. In addition, NAC provides the unique opportunity to assess response to treatments within months rather than years of follow‑up. However, predictive markers of tumor response to NAC are lacking. Therefore, the present study aimed to investigate the expression of endoglin, a marker of angiogenesis, and its association with pathologic responses to NAC. Samples from 34 breast cancer patients were obtained prior to and following NAC treatment. Immunohistochemical staining for endoglin and the mechanistic target of rapamycin (mTOR) was performed, and the correlation between the expression of these markers and pathologic response was examined. The overall response rate to NAC of these 34 patients was 67.6%. A mean microvascular density value of 14 served as a threshold score for the increased expression of endoglin. Increased expression of endoglin in primary tumors prior to NAC correlated with improved response in primary tumors (P=0.019) or in primary tumors and regional lymph nodes (P=0.014), when compared with reduced expression of endoglin. Increased expression of mTOR following NAC was additionally correlated with improved response to NAC. The results of the present study demonstrated that the expression of endoglin in breast tumor samples prior to NAC may be a predictor of treatment response. Long‑term follow‑up of clinical outcome is required to explain the elevation of mTOR expression levels following NAC treatment in responsive tumors.