Claudin-3 and Claudin-4 Expression in Ovarian Epithelial Cells Enhances Invasion and Is Associated with Increased Matrix Metalloproteinase-2 Activity

Abstract

Claudin proteins form a large family of integral membrane proteins crucial for tight junction formation and function. Our previous studies have revealed that claudin-3 and claudin-4 proteins are highly overexpressed in ovarian cancer. To clarify the roles of claudins in ovarian tumorigenesis, we have generated human ovarian surface epithelial (HOSE) cells constitutively expressing wild-type claudin-3 and claudin-4. Expression of these claudins in HOSE cells increased cell invasion and motility as measured by Boyden chamber assays and wound-healing experiments. Conversely, small interfering RNA (siRNA)-mediated knockdown of claudin-3 and claudin-4 expression in ovarian cancer cell lines reduced invasion. Claudin expression also increased cell survival in HOSE cells but did not significantly affect cell proliferation. Moreover, the claudin-expressing ovarian epithelial cells were found to have increased matrix metalloproteinase-2 (MMP-2) activity indicating that claudin-mediated increased invasion might be mediated through the activation of MMP proteins. However, siRNA inactivation of claudins in ovarian cancer cell lines did not have a significant effect on the high endogenous MMP-2 activity present in these cells, showing that malignant cells have alternative or additional pathways to fully activate MMP-2. Taken together, our results suggest that claudin overexpression may promote ovarian tumorigenesis and metastasis through increased invasion and survival of tumor cells. (Cancer Res 2005; 65(16): 7378-85)

Phosphorylation of claudin-4 by PKCε regulates tight junction barrier function in ovarian cancer cells

“…Previous work has suggested that claudin-3 and claudin-4 overexpression in ovarian and other cancers may promote invasion and survival, but overexpression of claudins was not found correlated with barrier function [20]. Our current findings suggest that post-translation modifications of the overexpressed claudins may inhibit their TJ-related function while allowing other pro-oncogenic effects.…”

“…Mutant claudin-4 expression constructs were generated by PCR using the pCiNeo-CLDN4 expression plasmid previously described [20]. Point mutations of the serine or threonine residues in the consensus PKC site were introduced using the Quik-Change site-directed mutagenesis kit (Stratagene, La Jolla, CA).…”

“…So far, claudin-1,3,4,5,7,10,16 have been shown altered in various cancers [5]. The functions of these proteins in tumorigenesis are still being elucidated, but they may have important roles in cell survival, motility, and invasion of cancer cells [18][19][20]. The mechanisms leading to the overexpression of claudins in cancer as well as the mechanisms of post-translational regulation/ modification of these proteins in cancer are not well understood.…”

Claudin-1 and claudin-5 expression patterns differentiate lung squamous cell carcinomas from adenocarcinomas

“…This could be due to an increased mRNA or protein stability. CLDN-3 and CLDN-4 are upregulated in ovarian and uterine cancers, 10,17,35,36 and CLDN-4 expression has been exploited for therapeutic purposes. 24 CLDN-7 expression is decreased in breast carcinomas, 13,37 but Adenocarcinoma vs bronchial cell (n ¼ 6) upregulated in gastric carcinomas.…”

Toward an Integrative Analysis of the Tumor Microenvironment in Ovarian Epithelial Carcinoma

“…Claudin-3 and claudin-4 are frequently expressed in OEC, as they aid in altering membrane permeability to facilitate invasion. Both of these proteins have been implicated in gelatinase activation [75,76].…”