Introduction Neoadjuvant chemotherapy (NAC) is the standard treatment for locally advanced breast cancer. However, some tumors will not respond to this treatment due to histological and molecular features. The protein EZH2 (enhancer of zest homolog 2) is a histone methyltransferase that is correlated with poorly differentiated breast carcinomas and aggressive tumor behavior. Purpose The present study evaluated the association between EZH2 expression and response to NAC, and its correlation with HER2 overexpression, estrogen and progesterone receptors (ER, PR) and Ki-67 proliferation index. Methods A total of 60 patients with locally advanced breast cancer treated with NAC were selected for this study. Twenty-three paraffin blocks had not enough material for tissue resection, and were not evaluated. A tissue microarray based in immunohistochemistry (IHC) analysis of EZH2 was performed for the remaining 37 specimens. Patients were divided into two groups based on response to NAC. Results EZH2 expression was significantly associated with markers of poor prognosis such as ER negativity (p = 0.001), PR negativity (p = 0.042) and high Ki-67 proliferation index (p = 0.002). High EZH2 expression was not correlated with the response to NAC. Conclusions Our data suggested that EZH2 protein expression may not correlate with the clinical response to NAC. Other studies with more patients are needed to confirm this observation.
INTRODUCTION:Neoadjuvant chemotherapy is the treatment of choice for patients with locally advanced breast cancer, however, because of tumor heterogeneity, not all tumors will respond to this treatment. In this context, we evaluated the EZH2 protein (Enhancer of Zest Homolog 2), a histone methyltransferase. EZH2 catalyses the trimethylation of lysine 27 of histone H3. The purposes of this study were to evaluate the expression of EZH2 for predicting tumor response to neoadjuvant chemotherapy in locally advanced breast cancer and its relation to usual prognostic markers (HER2, Ki-67, hormonal receptors of estrogen and progesterone -ER and PR) and p53. METHODS: Thirty-seven paraffin-embedded tumor blocks from different patients with stages IIb and IIIa invasive breast cancer. All of them have received neoadjuvant anthracycline-containing chemotherapy. The patients belonged to two different groups. Group 1 comprised 19 patients with objective response to chemotherapy, and Group 2, comprised 18 patients with no response to treatment. A TMA-based (tissue microarray) immunohistochemical analysis of HER2, Ki-67, p53, estrogen and progesterone receptors and EZH2 was performed. RESULTS: The group of patients who did not achieve a response had higher age (56.5 years) than the patients with response to chemotherapy (46.5 years), but the groups did not differ from the number of cycles of chemotherapy, and from the values of hormone receptors and HER2, Ki-67 and EZH2. The analysis of age, number of cycles of chemotherapy and biological tumor markers did not show a significant difference between the two groups. There was a negative linear relationship between EZH2 values and age, number of cycles of chemotherapy and hormone receptors. There was a positive linear relationship between EZH2 and HER2 and Ki-67. There was no association between EZH2 expression and response to chemotherapy. CONCLUSIONS: EZH2 protein is negatively correlated with hormonal receptors (ER and PR), and positively correlated with HER2 and Ki-67. There was no correlation between EZH2 expression and response to neoadjuvant anthracyclinecontaining chemotherapy.
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