Elevated expression of both MDR1 and MMP-2 genes in metastasized lymph node of invasive ductal breast cancer

There is emerging evidence that matrix metalloproteinase (MMP)-2 plays a crucial role in cancer invasion/metastasis. However, little evidence is available about the connections of multidrug resistance protein 1 (MDR1) and cancer invasion/metastasis so far.

To investigate the expression of MDR1 and MMP2 in primary breast tumors and their corresponding metastasized lymph nodes.

Only lymph nodes which were pathologically identified as metastases were included in this study to compare with the corresponding primary tumor. We determined the expression of MDR1 and MMP2 in primary breast tumor and its metastasized lymph node specimens of 21 patients. The quantitative real-time polymerase chain reaction (Q-RT-PCR) technique was used to assess the MDR1 and MMP2 RNA expression levels in primary breast tumor and lymph nodal specimens. Target gene copies were normalized using beta-actin (beta-actin) gene copies. Tumor characteristics and number of metastatic lymph nodes were gathered from the pathology reports.

The Q-RT-PCR data showed that MDR1 expression in metastasized lymph node was higher than that of their corresponding primary tumors (p < 0.05), MMP2 expression in metastasized lymph nodes was also even higher compared with their matched primary tumors (p < 0.01). But SPSS bivariate correlation analysis revealed that MDR1 expression in lymph node was not correlated with MMP-2 expression in lymph node, number of metastasized lymph nodes and tumor size (p > 0.05). MDR1 expression in primary tumors was highly correlated with in corresponding lymph node metastases (p < 0.01 r = 0.795).

All those indicated that MMP-2 should play an important role in the lymph node metastasis. However, further clinical studies with larger sample size need to be performed to verify these findings.