〔Abstract〕 Objective To investigate the expression of(heat shock protein a member 8,HSPA8) in breast cancer and its effect on tumor biological behaviors.Methods Bioinformatics analysis and immunohistochemistry assays were used to detect the expression of HSPA8 in breast cancer and adjacent non-tumor breast tissues,and the relationship between its expression and clinicopathological characteristics of breast cancer patients was analyzed.Correlation between HSPA8 expression and prognosis of breast cancer patients was analyzed by Kaplan-Meier Plotter database.HSPA8 knockdown and over expression breast cancer stabilized cells were constructed,respectively.CCK-8,clone formation,Transwell,cell scratch,Western blot and immunofluorescence assay were used to detect the effects of HSPA8 on the proliferation,invasion and migration of breast cancer cells,and its effect on epithelial-mesenchymal transition(EMT).Results Bioinformatics analysis and immunohistochemistry assay revealed that the expression of HSPA8 in breast cancer tissues was higher than that in adjacent non-tumour tissues(P<0.05),and its expression level of the protein was significantly and positively correlated with the tumor size,histological grade,lymph node metastasis and Ki-67 proliferation index(P<0.05).The Kaplan-Meier survival curve showed that high expression of HSPA8 was significantly associated with poor prognosis in breast cancer patients(P<0.05).CCK-8,clone formation,transwell,cell scratch,Western blot and immunofluorescence assay showed that knockdown of HSPA8 expression could significantly inhibit the proliferation,invasion,migration function and EMT of breast cancer cells(P<0.05),while overexpression of HSPA8 could significantly promote the proliferation,invasion,migration function and EMT of breast cancer cells(P<0.05).Conclusion HSPA8 is highly expressed in breast cancer tissues,which is closely related to disease progression and the malignant phenotype of breast cancer,suggesting that HSPA8 may be a potential biological target for breast cancer treatment.