Abstract: Objective: To explore the expressions of microRNA(miR)-125b and its target gene semaphorin4C(SEMA4C) in breast cancer tissue(BRCR) and adjacent normal tissue(NCT),and analyze its correlation with clinicopathologic features and significance.Methods: The expressions of miR-125b in 24 BRCR and NCT were detected using Real-time quantitative PCR,and the expressions of SEMA4C in 40 BRCR and NCT were detected by immunohistochemistry.The relationships between the expressions of miR-125b and SEMA4C and clinico-pathological parameters including age,clinical staging,lymph node metastasis,estrogen receptor,progesterone and human epidermal growth factor receptor -2(cerbB-2) were analyzed.Results: The expression of SEMA4C in BRCR was higher than that in NCT,the difference between the expression of SEMA4C and cerbB-2 in lymph node metastasis tissue was statistically significant(P<0.01 and P<0.05).The differences of the age,histological grading,clinical staging,and estrogen and progesterone receptors were not statistically significant(P>0.05).The expression of miR-125b in BRCR was lower than that in NCT(P<0.05),the differences between the expression of SEMA4C and cerbB-2 in lymph node metastasis tissue were statistically significant(P=0.034 to P=0.022).Conclusions: The expressions of miR-125b and SEMA4C in breast invasive ductal carcinoma increase and decrease,respectively,which is associated with lymph node metastasis and cerbB-2 level.The SEMA4C is one target gene of miR-125b,and miR-125b may serve as a potential breast cancer marker.