[Clinical significance of expression of multidrug resistance gene in breast cancer tissue].

OBJECTIVES

To investigate the role of expression of multidrug resistance gene (mdr-1 gene) in chemotherapeutic resistance of breast cancer and to determine if expression of mdr-1 gene may act as an index for predicting chemotherapy response and prognosis.

METHODS

Using reverse transcription-polymerase chain reaction (RT-PCR) technique, we determined the levels of mdr-1 mRNA in 82 breast cancer samples.

RESULTS

Positive expressions of mdr-1 gene were 34.3% in 35 cases of untreated primary breast cancer and 59.0% in 47 cases of relapsed metastatic breast cancer, separately, and the difference was statistically significant (P < 0.05). In 28 cases of relapsed metastatic breast cancer of mdr-1 gene positive expression, 22(78.6%) were ever treated with MDR related drugs. Levels of mdr-1 gene expression of all 7 cases were higher after chemotherapy than before chemotherapy. Positive expressions were 16.7% and high grade positive expressions were 5.6% in 18 sensitive cases. Positive expressions were 71.4% and high grade positive expressions were 50.0% in 14 resistant cases. The difference was statistically significant (P < 0.01). There were no relations between expression of mdr-1 gene and ages, menopause status, lymphnode involvements, clinical stages, and estrogen receptor levels.

CONCLUSION

The results indicated that retreated metastatic breast cancer is more extensively resistant than untreated primary breast cancer and acquired drug resistance is an important reason. Expression of mdr-1 gene seems to be a reference index for predicting response of chemotherapy.