Abstract: Objective We aimed to investigate the expression of Reg IV in breast cancer and specific molecular subtypes. The relationships between Reg IV and clinical pathological features were also analyzed. Methods 75 cases of normal breast tissues and 140 cases of malignant breast cancer, which including 30 cases of LA type, 50 cases of LB type, 30 cases of HER-2+ type, and 30 cases of TNBC type, were involved in the current study. EnVison immunohistochemistry was used to detect the expression of Reg IV. Real-time quantitative PCR and biological databases were used to analyze Reg IV protein mRNA and the association with clinical pathological features. Results The expression of Reg IV mRNA and protein was higher in malignant breast cancer compared with normal breast tissues (P＜0.05). The level of Reg IV in non TNBC was higher than that in TNBC (P＜0.05). Additionally, Reg IV up-regulation was related to positive ER, PR and HER-2 (P＜0.05), instead of Ki-67 and EGFR. Reg IV was also significantly associated with age, tumor size, TNM stage and prognosis (P＜0.05), but no significantly correlated with lymph node metastasis, histological grade and position. Conclusion Our research demonstrated that Reg IV may play an important role in malignant breast cancer, especially in non TNBC. Reg IV may be a promising biomarker for the prognosis of breast cancer patients.

Key words: breast neoplasms；carcinoma；regenerating islet-derived family member Ⅳ；prognosis, molecular subtypes；
clinical pathological features