Expression Of Some Multidrug Resistant Gene And Protein In Breast Cancer Cases

BACKGROUND: Breast cancer is one of the most common malignant tumors in woman. An important fact which lead to failure in treating breast cancer is the multidrug resistance of cancer cell. Breast cancer resistant protein (BCRP) is a newly identified multidrug resistance gene. Recent research of BCRP was concentrated on cancer cell line. It might play a role in clinic breast cancer chemotherapy. Objective: To clone BCRP cDNA fragment. To evaluate the relevance of the BCRP expression in breast cancer cases. To study the relationship between multidrug resistance and biological characteristics of breast cancer via clinic data reviewing. METHODS: The fragment of BCRP cDNA was synthesized by reverse transcription(RT)-PCR. Northern blot analysis was used to detect the BCRP mRNA in primary and recurrence fresh breast cancer specimens. Those recurrence cases were treated by doxorubicin before. The relationships between p-glycoprotein and lymph node stage as well as ER or PR were analyzed. RESULTS: A fragment of BCRP cDNA was synthesized from clinic breast cancer specimens successfully. Northern blot analysis showed that BCRP was expressed at a low level in primary breast cancer cases, while at a relatively high level in recurrent cases. The BCRP positive rate was 16.67% and 33.33% in primary and recurrent cases respectively. There is no significant statistically difference between them. In the condition of same tumor size stage, p-glycoprotein overexpressing level had no significant statistic difference in different ER or PR stage, while the result suggested that p-glycoprotein positive level is associated with lymph node metastasis stage. CONCLUSIONS: BCRP exists in clinic breast cancer cases. BCRP expression in recurrent breast cancer cases which were receiveddoxorubicin before was higher than in primary cases. BCRP plays a role in drug resistance in clinical chemotherapy. And the different expression of resistant proteins is related to the degree of malignancy in breast cancer tissue. This might account for why chemotherapy often failed in advanced breast cancer.