14-3-3ζ promoted invasion and lymph node metastasis of breast invasive ductal carcinoma with HER2 overexpression

HER2 was a recognized oncogene that promoted the development and metastasis of breast cancer, but its positive expression rate in invasive ductal carcinoma (IDC) was much lower than that in ductal carcinoma in situ (DCIS). The correlation between the occurrence and development of breast cancer and the amplification and overexpression of HER2 gene alone was still controversial. 14-3-3ζ had a strong protein binding ability and a variety of functions, mainly through the interaction with other proteins to exert its unique biological activities. However, influence and interaction relationship of the two proteins on the development of IDC was not clear. Furthermore, the mutual effect mechanism of synergy effect on lymph node metastasis of IDC was not known well too.Immunohistochemistry experiment was performed to detect expression status of 14-3-3ζ, HER2, TGF-β, p53 and Gli2 in paraffin-embedded samples respectively, including 30 cases of normal breast tissue, 30 cases of usual ductal hyperplasia (UDH), 30 cases of atypical ductal hyperplasia (ADH), 30 cases of DCIS and 120 cases of IDC.The positive expression rates of 14-3-3ζ/HER2 in Normal group, UDH group, ADH group, DCIS group and IDC group were 30%/0.00%, 26.7%/0.00%, 53.3%/33.3%, 46.7%/53.3% and 50%/24.2%, respectively. Compared with Normal group or UDH group, the expression of 14-3-3ζ was significantly increased in ADH, DCIS and IDC groups. 14-3-3ζ was overexpressed in only 4 of the 16 DCIS cases with HER2 overexpression (25.0%, 4/16), but it was overexpressed in 7 of the 9 IDC cases with DCIS (77.8%, 7/9). Among HER2 overexpression cases, 14-3-3ζ overexpression was significantly different between DCIS group and IDC with DCIS group (P = 0.017). In 18 IDC cases with lymph node metastasis and HER2 overexpression, 14-3-3ζ was overexpressed in 15 cases (83.3%, 15/18), while in the 11 IDC cases without lymph node metastasis, 14-3-3ζ and HER2 were overexpressed in only 5 cases (45.5%, 5/11). Co-overexpression of 14-3-3ζ and HER2 was positively correlated with occurrence of lymph node metastasis (P = 0.048). TGF-β was overexpressed in both precancerous lesion group and IDC group compared with normal group. Compared with the IDC group without lymph node metastasis, TGF-β expression was significantly increased in the IDC group with lymph node metastasis (P = 0.015). In IDC cases with 14-3-3ζ and HER2 co-overexpression, the expression of p53 in IDC with lymph node metastasis was significantly decreased (P = 0.010), while the expression of Gli2 was significantly increased compared with IDC cases without lymph node metastasis (P = 0.038). The co-overexpression of 14-3-3ζ and HER2 was positively correlated with ER negative expression (P < 0.001) and PR negative expression (P = 0.038), respectively.14-3-3ζ synergistic with HER2 could promote the occurrence and development of breast IDC and induce the lymph node metastasis of IDC, suggesting that combined overexpression of 14-3-3ζ and HER2 would lead to higher invasion and metastasis risk of breast cancer. It was speculated that the combined detection of 14-3-3ζ and HER2 would be one of the key factors affecting the clinical treatment decision and prognosis.