Background and purpose: Resistance to antitumor agents is a major cause of treatment failure in patients with breast cancer. Research has shown that

tumor stem cell marker aldehyde dehydrogenase 1 (ALDH1) is related with some anticancer drugs (such as cyclophosphamide

cisplatin) resistance

and the content of ALDH1 in tu

mor cells after treatment is higher than that before treatment. Breast cancer resistance protein (BCRP) is not expressed in normal tissues

but high expressed in breast cancer of after treatment

it may be associated with the mechanism of tumor drug resistance. This study was to investigate the correlation between expression and the relationship between these two kinds of protein ALDH1

BCRP and clinical pathological characteristics. Methods: Immunohistochemistry was performed to detect the expression of ALDH1 and BCRP in breast infiltrating ductal carcinoma tissues

and whether there is a correlation between and explore their relationship with clinical pathological features and their expression. Results: The expression of ALDH1 protein and BCRP protein in breast cancer and paracarcinoma breast tissues has significant difference(χ

2

=14.685

P=0.000; χ

2

=12.243

P=0.000).The expression of ALDH1 with patients age

pathologic stage

axillary lymph node metastasis

histological grading

ER

PR

and HER-2 state were not relevant(P0.05). HER-2

BCRP protein

expression was higher in cancer tissue (χ

2

=5.289

P=0.021). There were no relevant with the expression of BCRP with patients age

pathologic stage

axillary lymph node metastasis and histological grading

estrogen receptor (ER)

progesterone receptor (PR)

human epidermal growth factor receptor (HER-2) (P0.05). Conclusion: ALDH1 proteins may be an independent factor compared with occur drug resistant protein

and participate breast cancer drug resistance in the chemotherapy and tumor invasion and metastasis of malignant biological behavior.