Browsing School of Dentistry by Subject "Semaphorin 4D"
Now showing items 1-2 of 2
Expression of MT1-MMP in Head and Neck Squamous Cell Carcinomas (HNSCCs) and Endothelial Cells is Regulated by Hypoxia and Semaphorin 4D (Sema4D)Membrane type 1 matrix metalloproteinase (MT1-MMP) is an integral membrane protein that is important in tumor growth, migration, and invasion. It has the ability to degrade ECM, non-matrix proteins such as CD44 and integrin, and activate MMP2. Semaphorin 4D (Sema4D), a membrane-bound semaphorin, is highly expressed in malignancies such as head and neck squamous cell carcinoma (HNSCC) and is known to be pro-angiogenic, promoting the growth of blood vessels into a developing tumor by acting as a chemoattractant when bound to its receptor, Plexin-B1 (PB1), on endothelial cells. Our central hypothesis is that tumor hypoxia causes an increase in Sema4D, which acts in an autocrine and paracrine manner on tumor cells to induce the overexpression of MT1-MMP, which, in turn, cleaves Sema4D and increases availability to the tumor microenvironment to promote tumor-induced angiogenesis and invasion. Using immunoblots and flow cytometry, we demonstrate that MT1-MMP increases in HNSCC cells in a Sema4D and Plexin-B1-dependent manner in hypoxia. Also, we show that RhoA and NF-?B (downstream effectors of Plexin-B1) are important in the regulation of cell surface MT1-MMP expression under hypoxic conditions. Consequently, tumor-induced invasion and angiogenesis are enhanced. Soluble Sema4D diffuses out from the tumor and acts as a chemoattractant for endothelial cells, which also upregulate MT1-MMP on their surface to facilitate migration through the extracellular matrix. We conclude that Sema4D controls its own availability and, therefore, its own pro-angiogenic potential through autocrine/paracrine regulation of MT1-MMP.
The Role of Semaphorin 4D (Sema4D) in Bone MetastasisThe Role of Semaphorin 4D (Sema4D) in Bone Metastasis Background: Bone metastasis is a catastrophic endpoint of many neoplastic diseases, but especially for patients with advanced breast cancer. Despite the continuous advances in pharmacological and cancer research, bone loss and subsequent bone complications are seen in 70% of females diagnosed with breast cancer. Semaphorin 4D (Sema4D), a protein originally described to regulate the immune response, is now known to have a novel role in bone regulation. Sema4D is also found to be highly expressed by many tumor cells including those of breast cancer. In this study we focus on the role of Sema4D produced by tumor cells on their ability to metastasize to bone. Materials and methods: The osteoblast cell line MC3T3 was treated under different osteogenic conditions to examine the effects of Sema4D on bone differentiation in vitro. We also used tumor cells with silenced Sema4D to investigate the effects of tumor-derived Sema4D on their ability to metastasize to bone in vivo. Results: Sema4D produced by the breast cancer cell line MDA-231 inhibited bone matrix formation and mineralization in vitro. In vivo, however, MDA-231 tend to spread to bone only when Sema4D was highly expressed by these cells and not when it was silenced. Conclusion: Over-expression of Sema4D by breast cancer cells inhibits bone formation in vitro and tends to increase the ability of these cells to metastasize to bone in vivo and establish osteolytic lesions characterized by this tumor type. Our findings may serve as a solid starting point to investigate the role of anti-Sema4D therapy in tumor metastasis. Further in vivo studies are strongly encouraged to clinically determine their effects.