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Neoexpression or upregulation of placental cadherin (P-cadherin), a member of the classical cadherin family, has previously been described in several carcinomas, such as colorectal and bladder carcinomas. In this study, we combined two different approaches, immunohistochemistry of tumor samples and in vitro knockdown of P-cadherin, to gain a better insight into the role of P-cadherin in these types of cancer. First, we performed immunohistochemistry for P- and E-cadherins in a series of 52 colorectal adenocarcinomas, including well, moderately and poorly differentiated (WD, MD, and PD) tumors. Decrease or loss of P-cadherin neoexpression was significantly associated with a higher tumor grade and could discriminate WD from MD and/or PD tumors (p < 0.001). E-cadherin, on the other hand, was strongly expressed at the membrane of most WD (18 of 19) and MD tumors (15 of 19). Downregulation correlated significantly with the PD phenotype (p ≤ 0.001). In a second approach, we transiently or stably knocked down P-cadherin in HT-29 colon adenocarcinoma cells. This led to decreased intercellular adhesion and to an increased migratory and long-term invasive phenotype compared with control HT-29 cells, suggesting that P-cadherin acts as a proadhesive and anti-invasive/antimigratory molecule in colon carcinoma cells. Contrasting with these results and illustrating the context-specific function of P-cadherin were our results obtained in RT-112 bladder carcinoma cells. Stable knockdown of P-cadherin in RT-112 cells diminished invasion and migration, and promoted intercellular adhesion., (Copyright © 2010 UICC.)

Down-regulation of the epithelial cell-cell adhesion molecule E-cadherin is frequently associated with tumor formation and progression. Besides its role in physical cell-cell adhesion, E-cadherin is also thought to be involved in intracellular signaling in normal epithelial cells. In these cells, the Armadillo catenin p120ctn binds to the cytoplasmic domain of E-cadherin and stabilizes the adhesion complexes. On loss of E-cadherin, cytoplasmic p120ctn might accumulate and contribute to tumor malignancy. We used suppression subtractive hybridization to search for genes regulated by E-cadherin expression. We isolated human Nanos1 as a transcript of which levels decrease on E-cadherin reexpression in a human breast cancer cell line. The hNanos1 protein bears a COOH-terminal (CCHC)(2) zinc finger domain and belongs to an evolutionarily conserved protein family sharing functions in germ cell development in both vertebrates and invertebrates. We found an inverse correlation between E-cadherin and hNanos1 expression in various cell lines and under diverse conditions. Conditional expression of hNanos1 in human colorectal DLD1 cancer cells functionally abolished cell-cell adhesion. It induced cytoplasmic translocation of p120ctn, as well as strong migratory and invasive properties. We also found that the NH(2)-terminal domain of hNanos1, which is conserved only among mammals, interacts with p120ctn. hNanos1 counteracted the stimulatory effect of p120ctn on cell protrusion formation. Together, these findings describe a new function for hNanos1 as a downstream effector of E-cadherin loss contributing to tumor progression. Targeting hNanos1 might be a promising strategy in the treatment of E-cadherin-negative tumors in particular.

Malignant transformation of melanocytes frequently coincides with alterations in epithelial cadherin (E-cadherin) expression, switching on of neural cadherin (N-cadherin), and, when progressed to a metastatic stage, loss of membranous placental cadherin (P-cadherin). In vitro studies of melanoma cell lines have shown invasion suppressor and promoter roles for E-cadherin and N-cadherin, respectively. In the present study, we investigated the effect of P-cadherin on aggregation and invasion using melanoma cells retrovirally transduced with human P-cadherin. De novo expression of P-cadherin in P-cadherin-negative cell lines (BLM and HMB2) promoted cell-cell contacts and Ca2+-dependent cell-cell aggregation in two- and three-dimensional cultures, whereas it counteracted invasion. These effects were not observed following P-cadherin transduction of endogenously P-cadherin-positive MeWo cells. In addition, P-cadherin-transduced BLM cells coaggregated with keratinocytes and showed markedly reduced invasion in a reconstructed skin model. The proadhesive and anti-invasive effects of P-cadherin were abolished on targeted mutation of its intracellular juxtamembrane domain or its extracellular domain. For the latter mutation, we mimicked a known missense mutation in P-cadherin (R503H), which is associated with congenital hypotrichosis with juvenile macular dystrophy.

P-cadherin expression in breast carcinomas has been associated with tumors of high histologic grade and lacking estrogen receptor-alpha, suggesting a link between these proteins. In the MCF-7/AZ breast cancer cell line, blocking estrogen receptor-alpha signaling with the antiestrogen ICI 182,780 induced an increase of P-cadherin, which coincided with induction of in vitro invasion. Retroviral transduction of MCF-7/AZ cells, as well as HEK 293T cells, showed the proinvasive activity of P-cadherin, which requires the juxtamembrane domain of its cytoplasmic tail. This study establishes a direct link between P-cadherin expression and the lack of estrogen receptor-alpha signaling in breast cancer cells and suggests a role for P-cadherin in invasion, through its interaction with proteins bound to the juxtamembrane domain.

Matrix metalloproteases from the cell surface cleave an 80 kDa E-cadherin fragment (sE-CAD) that induces invasion of cancer cells into collagen type I and inhibits cellular aggregation. Conditioned media from MDCKts.srcCl2 cells at 40 degrees C and 35 degrees C, PCm.src5 and COLO-16 cells at 37 degrees C contained spontaneously released sE-CAD; these 48 h old conditioned media were capable of inhibiting E-cadherin functions in a paracrine way. Here we show direct cleavage of the extracellular domain of E-cadherin by the serine protease plasmin. sE-CAD released by plasmin inhibits E-cadherin functions as evidenced by induction of invasion into collagen type I and inhibition of cellular aggregation. This functional inhibition by sE-CAD was reversed by aprotinin or by immunoadsorption on protein Sepharose 4 fast flow beads with antibodies against the extracellular part of E-cadherin. Our results demonstrate that plasmin produces extracellular E-cadherin fragments which regulate E-cadherin function in cells containing an intact E-cadherin/catenin complex.

The E-cadherin/catenin complex is a powerful invasion suppressor in epithelial cells. It is expressed in the human MCF-7 breast cancer cell line family, but functionally defective in the invasive MCF-7/6 variant. Previous experiments have shown that IGF-I, tamoxifen, retinoic acid and tangeretin are able to upregulate the function of this complex in MCF-7/6 cells. We investigated the effect of 8-prenylnaringenin (8-PN), the phytoestrogen present in hops and beer, on aggregation, growth and invasion in MCF-7/6 cells. 8-PN was found to stimulate E-cadherin-dependent aggregation and growth of MCF-7/6 cells in suspension. These effects could be inhibited by the pure anti-estrogen ICI 182,780. 8-PN did not affect invasion of MCF-7/6 cells in the chick heart assay in vitro. In all these aspects 8-PN mimics the effects of 17beta-estradiol on MCF-7/6 cells.