Inhibition of MMP-2-mediated cellular invasion by NF-κB inhibitor DHMEQ in 3D culture of breast carcinoma MDA-MB-231 cells: A model for early phase of metastasis.

The three-dimensional (3D) culture of cancer cells provides an environmental condition closely related to the condition in vivo. It would especially be an ideal model for the early phase of metastasis, including the detachment and invasion of cancer cells from the primary tumor. In one hand, dehydroxymethylepoxyquinomicin (DHMEQ), an NF-κB inhibitor, is known to inhibit cancer progression and late phase metastasis in animal experiments. In the present research, we studied the inhibitory activity on the 3D invasion of breast carcinoma cells. Breast carcinoma MDA-MB-231 cells showed the most active invasion from spheroid among the cell lines tested. DHMEQ inhibited the 3D invasion of cells at the 3D-nontoxic concentrations. The PCR array analysis using RNA isolated from the 3D on-top cultured cells indicated that matrix metalloproteinase (MMP)-2 expression is lowered by DHMEQ. Knockdown of MMP-2 and an MMP inhibitor, GM6001, both inhibited the invasion. DHMEQ was shown to inhibit the promoter activity of MMP-2 in the reporter assay. Thus, DHMEQ was shown to inhibit NF-κB/MMP-2-dependent cellular invasion in 3D-cultured MDA-MB-231 cells, suggesting that DHMEQ would inhibit the early phase of metastasis.