Primary Study In The Expression And Modulation Of HLA And B7 In The Breast Cancer Cell Line MCF-7 And MCF-7/ADR

Objective: Multidrug resistance (MDR) and immune tolerance are the two major obstacles in cancer therapy. The over-expression of the multidrug resistance gene mdrl that encodes a 170-kDa membrane protein called P- glycoprotein (P-170) is known to mediate MDR in many cancers including human breast cancer. As observed with some tumor cells and cancer patients, down-expression of human leucocyte antigen (HLA) and/or lake of co- stimulatory molecular B7 are demonstrated the main mechanism of tumor immune escape. However, the expression of HLA and B7 in human breast cancer MDR phenotype and its relationship with MDR, the modulation effect of interferon (IFN) on the expression of HLA and B7, and its therapeutic effects on breast cancer MDR are unknown. Methods: The expression of HLA and B7 and P-170 on the human breast cancer cell line MCF-7 and its adramycin resistance subline MCF- 7/ADR were analyzed and compared by flow cytometer (FCM). The MDR phenotype MCF-7/ADR cells were treated with human reconstructive LFN- a 2b (rhIFN- a 2b) at different doses (100 lU/mi, 400 lU/mi, 800 IU/ml) and the expression of HLA, B7 and P-170 were determined at different time (12, 24 and 48 hours after treatment) by FCM and ACAS, and compared with non-treated cells. The alteration of drug sensitivity was tested by the MTT assay. All the data was analyzed by the SPSS 8.0 statistic computer program. Results: The MTT assay and FCM analysis indicated that the P-170 positive rate of the MCF-7/ADR cells was 85.5% and the 50 percent inhibition concentration (IC50) of the MCF-7/ADR cells to ADR, DDP and VCR were 49.5, 13.9 and 5.3 times of that of MCF-7 cells respectively. Compared with MCF-7 cells, significantly down-expression of HLA class I, up-expression of HLA class II and altered expression of B7 molecules were detected in MCF-7/ADR cells. FCM and ACAS analysis revealed that the MCF-7/ADR cells treated with rhIFN- a 2b had enhanced HLA (especially HLA- I ) and B7 expression in a dose-dependent and time-dependent fashion. The IC50 value of the MCF-7/ADR cells to ADR, DDP and VCR also decreased significantly by treatment of rhIFN- a 2b. The expression of P-i 70 did not altered significantly in the two cell lines treated with rhlFN- a 2b. Conclusions: Down-expression of HLA- I molecule in the MCF- 7/ADR cells may be one of the important mechanisms of immune tolerance. The rhIFN- a 2b at a dose of 100-400 lU/mi can effectively enhance the expression of HLA- I and II molecules suggesting that it may have a potentially therapeutic role in the reversion of immune tolerance of breast cancer with MDR phenotype. The rhIFN- a 2b at a high dose above 1000 IU/ml can increase chemosensitivity of the MCF-7/ADR cells, indicating that the local delivery of high doses of rhIFN- a 2b may be an effective method in the treatment of MDR cancers. This study also suggests that cytokine treatment may be a simple and effective method in the reversion of immune tolerance of cancer.