EZH2 overexpression in different immunophenotypes of breast carcinoma and association with clinicopathologic features

Abstract

Background: Enhancer of zest homolog 2 (EZH2), a histone 3 methyltransferase, is associated with aggressive behavior of many tumors and is a promising target of molecular therapy.

Methods: To better elucidate the relevance of EZH2 in breast cancer subtypes, we evaluated EZH2 expression in 226 invasive breast carcinomas with four distinct immunophenotypes and in association with clinicopathological features.

Results: Of these cases, 138 (61.1 %) were defined as EZH2-overexpressing with a multiplicative score > 3. EZH2 expression was inversely related to the status of ER and PR (Chi-square, p < 0.001), and it was significantly associated with HER2 positivity, high proliferative index, and high histologic grade (Chi-square, p < 0.05). ER-positive breast carcinoma with low proliferative index (Ki67 < 14 %) showed the lowest expression and triple-negative breast carcinoma showed the highest overexpression of EZH2, 18.5 % (10/54) versus 90.9 % (50/55) (Chi-square, p < 0.001). Intriguingly, 88 % (44/50) cases of grade 3 triple-negative breast carcinoma showed uniformly strong EZH2 expression with a multiplicative score of 9. The percentage of EZH2 overexpression in ER-positive breast carcinoma with a high proliferative index or HER2-positive cases were 61.2 and 74 %, respectively. Furthermore, EZH2 expression was significantly elevated in high-grade DCIS compared to benign lesions (90 % versus 0, p < 0.001). However, there is no association between EZH2 expression and the status of histone 3 lysine 27 trimethylation or other clinicopathologic features.

Conclusion: In summary, triple-negative breast carcinoma showed the highest overexpression of EZH2. EZH2 overexpression is associated aggressive pathologic features including high nuclear grade, high proliferative index, and positivity of HER2 of breast carcinoma.

Keywords: EZH2 overexpression; High nuclear grade; Immunophenotype; Proliferative index; Triple-negative breast carcinoma.

Fig. 1

Immunostaining of EZH2 in invasive breast carcinoma of different nuclear grade with variable intensity and quantity were shown. Low grade tubular carcinoma showed bland morphology with well formed tubules and mild atypia (a). A low level of EZH2 expression with only scattered positive cells was observed in tubular carcinoma (d). Invasive carcinoma, not otherwise specific type of nuclear grade 2 (b) with moderate atypia showed moderate expression of EZH2 (e). Poorly differentiated carcinoma of nuclear grade 3 was characterized with obvious atypia and solid growth pattern (c). Homogeneously strong expression of EZH2 was detected in poorly differentiated carcinoma (f). (Magnification × 100)

Fig. 2

Triple-negative breast carcinoma showed diffusely strong positivity for EZH2. Typical histologic features such as high grade tumor cells arranged in cords and nest with prominent necrosis and pushing border were shown in HE stained section (a, Magnification × 100). The tumor cells were negative for HER2, ER, and PR (b, c, d, Magnification × 400), and showed high tumor proliferative index Ki67 (e, Magnification × 100). Strong overexpression of EZH2 was observed in high grade triple-negative breast carcinoma (f, Magnification × 400)

Fig. 3

EZH2 overexpressed in breast carcinoma and association with immunophenotype. Triple- negative breast carcinoma showed the highest percentage of EZH2 overexpression: 90.9 % (50/55) were defined as EZH2 overexpression with a multiplicative score of intensity and percentage > 3, and 88 % (44/50) among them showed strong overexpression of EZH2 with a maximum multiplicative score of 9. Low-grade ER-positive cases with low Ki67 index (<14 %) showed the lowest percentage of EZH2 overexpression, with only 18.5 % (10/54) having a multiplicative score >3, and no case garnered a maximum multiplicative score

Fig. 4

Immunostaining of EZH2 in benign lesions and high grade DCIS associated with triple-negative invasive breast carcinoma. Breast lobules, and UDH which showed benign proliferation of epithelial and myoepithelial cells without any atypia were shown (a and b). Breast lobules, and UDH expressed EZH2 in a low level, and only occasional EZH2 positive cells were observed (d and e). Representative high-grade DCIS associated with invasive triple-negative breast carcinoma showed solid growth pattern and central necrosis (c) (Magnification × 100). EZH2 was strongly overexpressed in high grade DCIS (f) (Magnification × 400)