Tissue transglutaminase links TGF-β, epithelial to mesenchymal transition and a stem cell phenotype in ovarian cancer

Tissue transglutaminase (TG2), an enzyme involved in cell proliferation, differentiation and apoptosis is overexpressed in ovarian carcinomas, where it modulates epithelial-to-mesenchymal transition (EMT) and promotes metastasis. Its regulation in ovarian cancer (OC) remains unexplored. Here, we show that transforming growth factor (TGF)-β, a cytokine involved in tumor dissemination is abundantly secreted in the OC microenvironment and induces TG2 expression and enzymatic activity. This is mediated at transcriptional level by SMADs and by TGF-β-activated kinase 1-mediated activation of the nuclear factor-κB complex. TGF-β-stimulated OC cells aggregate as spheroids, which enable peritoneal dissemination. We show that TGF-β-induced TG2 regulates EMT, formation of spheroids and OC metastasis. TG2 knock-down in OC cells decreases the number of cells harboring a cancer stem cell phenotype (CD44+/CD117+). Furthermore, CD44+/CD117+ cells isolated from human ovarian tumors express high levels of TG2. In summary, TGF-β-induced TG2 enhances ovarian tumor metastasis by inducing EMT and a cancer stem cell phenotype.

A modified hTERT promoter-directed oncolytic adenovirus replication with concurrent inhibition of TGFbeta signaling for breast cancer therapy

Our laboratory is interested to develop oncolytic adenoviral vectors that can be administered systemically for the treatment of breast cancer. To restrict viral replication in breast tumor cells, we have constructed mhTERTAd.sTβRFc, a 01/07 based adenoviral vector expressing the soluble form of TGFβ receptor II fused with human Fc IgG1 (sTGFβRIIFc) gene, in which viral replication is under the control of modified human telomerase reverse transcriptase (mhTERT) promoter. In addition, mhTERTAd.sTβRFc-mediated sTGFβRIIFc production would target growth factor-β (TGFβ) pathway known to contribute to the tumor progression breast cancer metastasis. We chose to use mhTERT promoter because it was found to be relatively more active (approximately 20-times) in breast cancer cells compared to normal human cells. We showed that infection of MDA-MB-231 and MCF-7 breast cancer cells for 48 hrs with mhTERTAd.sTβRFc produced high levels of sTGFβRIIFc (greater than 1 μg/ml) in the medium. Breast cancer cells produced nearly 6,000-fold increase in the viral titers during 48 hrs infection period. However, mhTERTAd.sTβRFc replication was attenuated in normal cells. Infection of breast cancer cells with a replication deficient virus Ad(E1^-).sTβRFc also produced high levels of sTGFβRIIFc, but under these conditions no detectable viral replication was observed. Adenoviral-mediated production of sTGFβRIIFc was shown to bind with TGFβ-1, and abolished the effects of TGFβ-1 on downstream SMAD-3 phosphorylation. The administration of mhTERTAd.sTβRFc intravenously into MDA-MB-231 human xenograft bearing mice resulted in significant inhibition of tumor growth, and production of sTGFβRIIFc in the blood. On the other hand, intravenous injection of Ad(E1^-).sTβRFc did not exhibit significant inhibition of the tumor growth, but resulted in the sTGFβRIIFc in the blood, suggesting that viral replication along with sTGFβRIIFc protein production play a critical role in inducing inhibition of tumor growth. These results warrant future investigation of mhTERTAd.sTβRFc as an anti-tumor agent in vivo.

RANKL plays a role in migration and invasion of the bone-seeking cell line MDA-MB-231-BO2 through human type I collagen by up-regulating MMP1

Abstract #2052

Background: Cancer-induced bone destruction is associated with increased osteoclastogenic activity induced by tumor cells, and an unbalanced bone remodelling cycle that favours bone osteolysis. In this proccess the RANK-RANKL signaling is crucial for both osteoclastogenesis and osteoclastic activity. Furthermore, breast cancer cells have been shown to also express the RANK receptor and to increase migration towards RANKL stimuli, however it is not known if RANK - RANKL interaction stimulates breast cancer cell to invade and degrade bone collagen. Objective: To determine if RANKL increases the ability of breast cancer cells to invade a type I collagen matrix and degrade bone collagen. Material and Methods: The influence of sRANKL on MDA-MB-231-BO2 cell migration or cell invasion (type I collagen) were assessed by Boyden-chamber chemotaxis assay. Binding of RANKL to BO2 cells, levels of RANK expression and levels of matrix metalloproteinases secreted during invasion were determined by RT-PCR and WB analysis. The activation of AKT signaling pathway was determined by WB against the phosphorylated form pAKT1/2/3(Ser473). Results: sRANKL influences the migration and invasion of RANK-expressing BO2 cells in a dose-dependent manner (dose range 0.75-2.5 ug/mL), while the neutralization of sRANKL with a specific antibody abrogated this effect. sRANKL stimuli activates AKT pathway downstream of RANK, while the pre-treatment of cells with 100 nM of wortmannin (a PI(3)K inhibitor) blocked this effect and impaired invasion. During invasion of type I collagen the levels MMP1 expression and of secreted MMP1 increase and are positively correlated with the increase in sRANKL concentration. Conclusions: Our data suggest that RANKL can trigger an increase in expression of MMP1 by breast cancer cells expressing RANK, contributing to invasion via degradation of matrix proteins directly by the cancer cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2052.

Low cell motility induced by hsp27 overexpression decreases osteolytic bone metastases of human breast cancer cells in vivo

The mechanisms controlling the formation of osteolytic bone metastases in patients with breast cancer are still poorly understood. To explore the role of motility in the establishment of osteolytic bone metastases, we have used a model of bone metastasis in which MDA-MB-231 breast cancer cells exhibiting low (hsp27-transfectants) and high (control-transfectant) endogenous cell motility were compared. We found that MDA-MB-231 cells exhibiting low cell motility were less capable of establishing osteolytic lesions. The number and the area of the osteolytic lesions in mice inoculated with low motility cells were both significantly smaller. Histomorphometry of bone lesions also demonstrated less tumor area in mice bearing hsp27 transfectants although there was no difference in the osteoclast number per square millimeter of tumor-bone interface. These data suggest that cell motility may be an important mechanism in the metastatic cascade of breast cancer cells to the bone and that controlling cell motility may be a useful target to prevent the establishment of osteolytic bone metastases.