Regulation of membrane-type 1 matrix metalloproteinase expression by zonula occludens-2 in human lung cancer cells.

During tumor invasion, tumor epithelial cells acquire migratory and invasive properties involving important phenotypic alterations. Among these changes, one can observe reorganization or a loss of cell-cell adhesion complexes such as tight junctions (TJs). TJs are composed of transmembrane proteins (occludin, claudins) linked to the actin cytoskeleton through cytoplasmic adaptor molecules including those of the zonula occludens family (ZO-1, -2, -3). We here evaluated the potential role of ZO-2 in the acquisition of invasive properties by tumor cells. In vivo, we showed a decrease of ZO-2 expression in bronchopulmonary cancers, with a preferential localization in the cytoplasm. In addition, in vitro, the localization of ZO-2 varied according to invasive properties of tumor cells, with a cytoplasmic localization correlating with invasion. In addition, we demonstrated that ZO-2 inhibition increases invasive and migrative capacities of invasive tumor cells. This was associated with an increase of MT1-MMP. These results suggest that ZO-2, besides its structural role in tight junction assembly, can act also as a repressor of tumor progression through its ability to reduce the expression of tumor-promoting genes in invasive tumor cells

The E-cadherin-repressed hNanos1 gene induces tumor cell invasion by upregulating MT1-MMP expression

In this study, we examined the role of the E-cadherin-repressed gene human Nanos1 (hNanos1) in tumor invasion process. First, our in vivo study revealed that hNanos1 mRNAs were overexpressed in invasive lung carcinomas. Moreover, hNanos1 was co-localized with MT1-MMP (membrane type 1-matrix metalloproteinase) in E-cadherin-negative invasive lung tumor clusters. Using an inducible Tet-on system, we showed that induction of hNanos1 expression in DLD1 cells increased their migratory and invasive abilities in a three-dimensional migration and in a modified Boyden chamber assay. Accordingly, we demonstrated that hNanos1 upregulated MT1-MMP expression at the mRNA and protein levels. Inversely, using an RNA interference strategy to inhibit hNanos1 expression in invasive Hs578T, BT549 and BZR cancer cells, we observed a downregulation of MT1-MMP mRNA and protein and concomitantly a decrease of the invasive capacities of tumor cells in a modified Boyden chamber assay. Taken together, our results demonstrate that hNanos1, by regulating MT1-MMP expression, plays an important role in the acquisition of invasive properties by epithelial tumor cells