RNAi-mediated downregulation of urokinase plasminogen activator receptor and matrix metalloprotease-9 in human breast cancer cells results in decreased tumor invasion, angiogenesis and growth

The serine protease urokinase-type plasminogen activator (uPA) plays a significant role in tumor cell invasion and metastasis when bound to its specific receptor, uPAR (also known as CD87). In addition to the uPA-uPAR system, matrix metalloproteinases (MMPs) are involved in tumor cell invasion and metastasis. In this study, we achieved specific inhibition of uPAR and MMP-9 using RNAi technology. We introduced small interfering RNA to downregulate the expression of uPAR and MMP-9 (pUM) in breast cancer cell lines (MDA MB 231 and ZR 75 1). In vitro angiogenesis studies indicated a decrease in the angiogenic potential of the treated cells; in particular, a remarkable decrease was observed in the cells treated with bicistronic construct (pUM) in comparision to the controls. Additionally, bicistronic construct inhibited the formation of capillary-like structures in in vivo models of angiogenesis. Similarly, the invasive potential and migration decreased dramatically when treated with the bicistronic construct as shown by matrigel invasion and migration assays. These results suggest a synergistic effect from the simultaneous downregulation of uPAR and MMP-9. We also assessed the levels of phosphorylated forms of MAPK, ERK and AKT signaling pathway molecules and found reduction in the levels of these molecules in cells treated with the bicistronic construct as compared to the control cells. Furthermore, targeting both uPAR and MMP-9 totally regressed orthotopic breast tumors in nude mice. In conclusion, our results provide evidence that the simultaneous downregulation of uPAR and MMP-9 using RNAi technology may provide an effective tool for breast cancer therapy.

Overexpression of Urinary Plasminogen Activator (uPA) Protein and mRNA in Thyroid Carcinogenesis

OBJECTIVE

Urinary plasminogen activator (uPA), a protease, is one of the critical components of tumor invasion and metastasis. Its expression in thyroid carcinoma and potential role in thyroid tumorigenesis are unknown. The objective of this study was to determine whether uPA is differentially expressed in benign and malignant thyroid tumors.

DESIGN

uPA expression was evaluated by immunohistochemistry (IHC) in 20 thyroid tumors (six classic papillary thyroid cancers (PTC) and three tall cell variants (TCV) and 11 adenomas). To validate IHC results, in situ hybridization was performed on both adenomas and cancer tissues to explore the expression of uPA at the mRNA level. The Fisher exact test was used to compare protein as well as mRNA expressions in adenomas and thyroid cancer.

RESULTS

Intense granular cytoplasmic staining for uPA was observed in five of nine (56%) of thyroid cancers: 2/6 classic PTC (33%) and all tall cell variant PTC. Furthermore, uPA mRNA expression was found in the malignant thyroid epithelium but not in adjacent normal thyroid follicles or the stromal elements. None of the adenomas expressed uPA (P = .008). uPA staining was absent in histologically normal follicles adjacent to malignant thyroid follicles.

CONCLUSIONS

uPA is expressed in thyroid carcinoma but not in benign adenomas or normal adjacent follicles. The selective expression of uPA in thyroid carcinoma provides evidence that uPA is useful in distinguishing benign and malignant thyroid neoplasms. More importantly, uPA may represent molecular target for therapeutic treatment of this malignancy.

Proteinase suppression by E-cadherin-mediated cell-cell attachment in premalignant oral keratinocytes

The expression and activity of epithelial proteinases is under stringent control to prevent aberrant hydrolysis of structural proteins and disruption of tissue architecture. E-cadherin-dependent cell-cell adhesion is also important for maintenance of epithelial structural integrity, and loss of E-cadherin expression has been correlated with enhanced invasive potential in multiple tumor models. To address the hypothesis that there is a functional link between E-cadherin and proteinase expression, we have examined the role of E-cadherin in proteinase regulation. By using a calcium switch protocol to manipulate junction assembly, our data demonstrate that initiation of de novo E-cadherin-mediated adhesive contacts suppresses expression of both relative matrix metalloproteinase-9 levels and net urinary-type plasminogen activator activity. E-cadherin-mediated cell-cell adhesion increases both phosphatidylinositol 3'-kinase (PI3-kinase)-dependent AKT phosphorylation and epidermal growth factor receptor-dependent MAPK/ERK activation. Pharmacologic inhibition of the PI3-kinase pathway, but not the epidermal growth factor receptor/MAPK pathway, prevents E-cadherin-mediated suppression of proteinases and delays junction assembly. Moreover, inhibition of junction assembly with a function-blocking anti-E-cadherin antibody stimulates proteinase-dependent Matrigel invasion. As matrix metalloproteinase-9 and urinary-type plasminogen activator potentiate the invasive activity of oral squamous cell carcinoma, these data suggest E-cadherin-mediated signaling through PI3-kinase can regulate the invasive behavior of cells by modulating proteinase secretion.