Differential Gene Expression of Primary Cultured Lymphatic and Blood Vascular Endothelial Cells12

Blood vascular endothelial cells (BECs) and the developmentally related lymphatic endothelial cells (LECs) create complementary, yet distinct vascular networks. Each endothelial cell type interacts with flowing fluid and circulating cells, yet each vascular system has evolved specialized gene expression programs and thus both cell types display different phenotypes. BECs and LECs express distinct genes that are unique to their specific vascular microenvironment. Tumors also take advantage of the molecules that are expressed in these vascular systems to enhance their metastatic potential. We completed transcriptome analyses on primary cultured LECs and BECs, where each comparative set was isolated from the same individual. Differences were resolved in the expression of several major categories, such as cell adhesion molecules (CAMs), cytokines, and cytokine receptors. We have identified new molecules that are associated with BECs (e.g., claudin-9, CXCL11, neurexin-1, neurexin-2, and the neuronal growth factor regulator-1) and LECs (e.g., claudin-7, CD58, hyaluronan and proteoglycan link protein 1 (HAPLN1), and the poliovirus receptor-related 3 molecule) that may lead to novel therapeutic treatments for diseases of lymphatic or blood vessels, including metastasis of cancer to lymph nodes or distant organs

Merlin/NF2 Regulates Angiogenesis in Schwannomas through a Rac1/Semaphorin 3F-Dependent Mechanism1

Neurofibromatosis type 2 (NF2) is an autosomal-dominant multiple neoplasia syndrome that results from mutations in the NF2 tumor suppressor gene. Patients with NF2 develop hallmark schwannomas that require surgery or radiation, both of which have significant adverse effects. Recent studies have indicated that the tumor microenvironment—in particular, tumor blood vessels—of schwannomas may be an important therapeutic target. Furthermore, although much has been done to understand how merlin, the NF2 gene product, functions as a tumor suppressor gene in schwannoma cells, the functional role of merlin in the tumor microenvironment and the mechanism(s) by which merlin regulates angiogenesis to support schwannoma growth is largely unexplored. Here we report that the expression of semaphorin 3F (SEMA3F) was specifically downregulated in schwannoma cells lacking merlin/NF2. When we reintroduced SEMA3F in schwannoma cells, we observed normalized tumor blood vessels, reduced tumor burden, and extended survival in nude mice bearing merlin-deficient brain tumors. Next, using chemical inhibitors and gene knockdown with RNA interference, we found that merlin regulated expression of SEMA3F through Rho GTPase family member Rac1. This study shows that, in addition to the tumor-suppressing activity of merlin, it also functions to maintain physiological angiogenesis in the nervous system by regulating antiangiogenic factors such as SEMA3F. Restoring the relative balance of proangiogenic and antiangiogenic factors, such as increases in SEMA3F, in schwannoma microenvironment may represent a novel strategy to alleviate the clinical symptoms of NF2-related schwannomas

Cancer Cell-Associated MT1-MMP Promotes Blood Vessel Invasion and Distant Metastasis in Triple-Negative Mammary Tumors.

Functional roles for the cancer cell-associated membrane type I matrix metalloproteinase (MT1-MMP) during early steps of the metastatic cascade in primary tumors remain unresolved. In an effort to determine its significance, we determined the in vivo effects of RNAi-mediated downregulation in mammary cancer cells on the migration, blood and lymphatic vessel invasion (LVI), and lymph node and lung metastasis. We also correlated the expression of cancer cell MT1-MMP with blood vessel invasion (BVI) in 102 breast cancer biopsies. MT1-MMP downregulation in cancer cells decreased lung metastasis without affecting primary tumor growth. The inhibition of lung metastasis correlated with reduced cancer cell migration and BVI. Furthermore, cancer cell-expressed MT1-MMP upregulated the expression of MT1-MMP in vascular endothelial cells, but did not affect MT1-MMP expression in lymphatic endothelial cells, LVI, or lymph node metastasis. Of clinical importance, we observed that elevated MT1-MMP expression correlated with BVI in biopsies from triple-negative breast cancers (TNBC), which have a poor prognosis and high incidence of distant metastasis, relative to other breast cancer subtypes. Together, our findings established that MT1-MMP activity in breast tumors is essential for BVI, but not LVI, and that MT1-MMP should be further explored as a predictor and therapeutic target of hematogenous metastasis in TNBC patients. Cancer Res; 71(13); 4527-38. ©2011 AACR