In the current study, we investigated the mechanism relating down−regulation of MKK4 expression to development of ovarian cancer. Over−expression of the MKK4 gene in TOV−21 G cells, a line with homozygous deletion of MKK4, resulted in morphologic changes in which cells growing in a scattered, fibroblast−like pattern formed tightly packed colonies. Based on a wound healing assay and a Matrigel invasion assay, we determined that both motility and invasiveness of MKK4−transfected TOV−21G cells were significantly reduced compared to control vector−transfected cells. To confirm that MKK4 expression related to tumor invasion resulted from an epithelial to mesenchymal transition (EMT)−like morphological change, we used two independent but complementary approaches. MKK4 gene knockdown in MDAH 2774 cells over−expressing MKK4 increased invasion activity. Additionally, engineered expression of MKK4 in SKOV3 cells, a line with low endogenous MKK4 expression, produced a phenotype similar to that of TOVG−21G. Interestingly, we found that MKK4 up−regulation caused down−regulation of phosphorylated NF−kappaB and Twist, as well as up−regulation of E−cadherin, in TOVG−21G and SKOV3 cells. Reciprocal results were obtained in MDAH 2774 cells with MKK4 knockdown. Our results suggest that MKK4 down−regulation causes increased phosphorylation NF−kappaB. This promotes Twist over−expression, resulting in E−cadherin down−regulation that induces EMT in ovarian cancer. © 2010 UICC.

PMID: 20309881 [PubMed − as supplied by publisher] Source: National Library of Medicine.