[Clinical significance of MDR gene expression in malignant pleural effusion and ascites and solid tumors].

OBJECTIVE: To discuss the guiding significance of multidrug resistance (MDR) gene expression for monitoring the clinical effectiveness of chemotherapy upon cancer, and to analyze the MDR1 and glutnthione-s-transferase(GST-pi) mRNA expression rates in primary breast cancer, and their correlation with the clinical outcome and prognosis. METHODS: The mRNA expression levels of MDR1 in 16 cases with malignant pleural effusion and ascites and 102 cases of solid tumors were measured using semiquantitative RT-PCR assay. The MDR1 and GST-pi mRNA expression rates in 84 cases of breast cancer, out of the 102 cases of solid tumors, were also studied in the same way. RESULTS: (1) An average coincidence rate of 84.5% was found between the mRNA expression level of MDR1 and the clinical response to chemotherapy in the 16 cases with malignant pleural effusion and ascites and 18 cases of solid tumors. (2) The positive rate of MDR1 mRNA expression in primary breast cancer tissue was 79.7%, with the medium and high levels as high as 33.3%, while the positive rate of GST-pi mRNA expression was 33.3%, with the medium and high expression levels being as low as 4.8%. There was a highly significant difference between the two groups (P < 0.01). The positive rates of MDR1 mRNA in the group having received chemotherapy before surgery and the group not receiving chemotherapy before surgery were 87.8% and 68.6% respectively, showing a lymph nodes and in the group without metastases in axillary lymph nodes were 89.1% and 68.4% respectively, indicating a significant difference (P < 0.05). The positive rates of GST-pi mRNA in the group suffering distant metastases and the group not suffering distant metastases were 71.4% and 20.6% respectively, showing a significant difference (P < 0.05). The GST-pi mRNA expression rates in the estrogen receptor (ER)- and progesterone receptor (PR)-positive groups were higher than those in the ER- and PR-negative groups, indicating a significant difference (P < 0.05) . CONCLUSION: The mRNA expression level of MDR1 has a relatively high correlation with the clinical response to chemotherapy, and thus can be used to monitor the effectiveness of chemotherapy. MDR1 is the main drug resistance mechanism in breast cancer. Chemotherapy before surgery induces MDR1 mRNA expression. MDR1 e xpression and GST-pi mRNA expression serve as a significant prognostic indicator for breast cancer, thus having guiding significance for assessing prognosis.