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    Class-3 semaphorins are secreted axon guidance factors. Some of these semaphorins have recently been characterized as suppressors of tumor progression. To determine if class-3 semaphorins can be used to inhibit the development of glioblastoma-multiforme tumors, we expressed recombinant sema-3A, 3B, 3D, 3E, 3F or 3G in U87MG glioblastoma cells. Sema3A and sema3B expressing cells contracted and changed shape persistently while cells expressing other semaphorins did not. Sema3A and sema3F differed from other semaphorins including sema3B as they also inhibited the proliferation of the cells and the formation of soft agar colonies. With the exception of sema3G and sema3B, expression of these semaphorins in U87MG cells inhibited significantly tumor development from subcutaneously implanted cells. Strong inhibition of tumor development was also observed following implantation of U87MG cells expressing each of the class-3 semaphorins in the cortex of mouse brains. Sema3D and sema3E displayed the strongest inhibitory effects and their expression in U373MG or in U87MG glioblastoma cells implanted in the brains of mice prolonged the survival of the mice by more then two folds. Furthermore, most of the mice that died prior to the end of the experiment did not develop detectable tumors and many of the mice survived to the end of the experiment. Most of the semaphorins that we have used here with the exception of sema3D were characterized previously as inhibitors of angiogenesis. Our results indicate that sema3D also functions as an inhibitor of angiogenesis and suggest that the anti-tumorigenic effects are due primarily to inhibition of tumor angiogenesis. These results indicate that class-3 semaphorins such as sema3D and sema3E could perhaps be used to treat glioblastoma patients.
    SEMA3A
    Plexin
    Background Previously, we reported that Sema3A, one of the secreted repulsive axon guidance molecules, CRMP (collapsin response mediator protein)‐2, a putative intracellular signalling molecule for Sema3A and Sema3A receptor neuropilin‐1 are expressed in the developing lung. Sema3A inhibits branching morphogenesis of embryonic lung in organ culture. Results We examined the gene expression of Sema3A, Sema3C, Sema3F and their receptors, NP‐1, NP‐2 and plexin‐A1 by in situ hybridization. Transcripts of all six genes were detected in mouse lung from embryonic day E11.5 to E17.5, and displayed highly specific spatiotemporal distributions. The distribution of the receptor genes was detected in patterns which were consistent with known receptor usage of the semaphorins. In contrast to Sema3A, we found that the other class 3 semaphorins, Sema3C and Sema3F, stimulated branching morphogenesis. This stimulatory effect of Sema3C or Sema3F was accompanied by a moderate increase in the incorporation of bromodeoxyuridine (BrdU) into DNA in the terminal epithelial cells. Conclusion The coordinated expression patterns of different semaphorins and their receptors, together with the specific activities affecting branching morphogenesis, suggest that the semaphorins act as both positive and negative regulators of branching morphogenesis in the developing lung.
    Branching (polymer chemistry)
    Secreted class 3 semaphorins (Sema3), which signal through holoreceptor complexes that are formed by different subunits, such as neuropilins (Nrps), proteoglycans, and plexins, were initially characterized as fundamental regulators of axon guidance during embryogenesis. Subsequently, Sema3A, Sema3C, Sema3D, and Sema3E were discovered to play crucial roles in cardiovascular development, mainly acting through Nrp1 and Plexin D1, which funnels the signal of multiple Sema3 in vascular endothelial cells. Mechanistically, Sema3 proteins control cardiovascular patterning through the enzymatic GTPase-activating-protein activity of the cytodomain of Plexin D1, which negatively regulates the function of Rap1, a small GTPase that is well-known for its ability to drive vascular morphogenesis and to elicit the conformational activation of integrin adhesion receptors.
    Plexin
    SEMA3A
    Neuropilin
    Growth cone
    Sal-like protein 4 (SALL4) is a zinc finger transcription factor that has been reported to be aberrantly expressed in several human malignancies and identified as an oncogene. However, the potential role of SALL4 in osteosarcoma remains to be elucidated. In this study, we explored the biological functions of SALL4 in osteosarcoma. We found that SALL4 was overexpressed in osteosarcoma tissues and cell lines. Knockdown of SALL4 inhibited osteosarcoma cell proliferation, migration, and invasion in vitro. In addition, SALL4 knockdown suppressed osteosarcoma growth and metastasis in vivo. We also showed that SALL4 knockdown decreased the protein expression of Wnt3a and β-catenin in osteosarcoma cells. Taken together, our study showed that SALL4 plays an important role in regulating the proliferation, migration, and invasion of osteosarcoma cells. Thus, SALL4 may represent a potential therapeutic target in the treatment of osteosarcoma.
    Class 3 semaphorins (Sema3s) regulate axon guidance, angiogenesis, tumor growth, and tumor metastasis. Neuropilins (NRPs; NRP1 and NRP2) are the cell surface receptors for the Sema3s. However, to signal, interaction of Sema3s and NRPs with plexins is obligatory. In this issue of the JCI, Casazza and colleagues report data that challenge the conventional wisdom about the role of Sema3s in tumor metastasis. As a rule, Sema3B and Sema3F, for example, are inhibitors of tumor angiogenesis, progression, and metastasis. However, Casazza et al. found that Sema3E inhibited tumor growth but atypically promoted invasiveness and metastasis. This metastatic potential was dependent on Plexin D1 expression but was independent of NRP expression. Of clinical importance, Sema3E and Plexin D1 were found to be upregulated in human colon cancer, liver metastasis, and melanoma progression.
    Plexin
    Tumor progression
    Citations (17)