10507

SEMA4D

sema domain, immunoglobulin domain (Ig), transmembrane domain (TM) and short cytoplasmic domain, (semaphorin) 4D;SEMA4D;sema domain, immunoglobulin domain (Ig), transmembrane domain (TM) and short cytoplasmic domain, (semaphorin) 4D

A8|BB18|GR3|sema domain, immunoglobulin domain (Ig), transmembrane domain (TM) and short cytoplasmic domain, 4D|semaphorin-4D

9q22.2

protein-coding

INTRODUCTION: Gene expression profiling has enabled us to demonstrate the heterogeneity of breast cancers. The potential of a tumour to grow and metastasise is partly dependant on its ability to initiate angiogenesis or growth and remodelling of new blood vessels, usually from a pre-existing vascular network, to ensure delivery of oxygen, nutrients, and growth factors to rapidly dividing transformed cells along with access to the systemic circulation. Cell-cell signalling of semaphorin ligands through interaction with their plexin receptors is important for the homeostasis and morphogenesis of many tissues and has been widely studied for a role in neural connectivity, cancer, cell migration and immune responses. This study investigated the role of four semaphorin/plexin signalling genes in human breast cancers in vivo and in vitro. MATERIALS AND METHODS: mRNA was extracted from formalin fixed paraffin embedded archival breast invasive ductal carcinoma tissue samples of progressive grades (grades I-III) and compared to tissue from benign tumours. Gene expression profiles were determined by microarray using the Affymetrix GeneChip(R) Human Genome U133 Plus 2.0 Arrays and validated by Q-PCR using a Corbett RotorGene 6000. Following validation, the gene expression profile of the identified targets was correlated with those of the human breast cancer cell lines MCF-7 and MDA-MD-231. RESULTS: The array data revealed that 888 genes were found to be significantly (ptumours and 563 genes between grade III and benign tumours. From these genes, we identified four genes involved in semaphorin-plexin signalling including SEMA4D which has previously been identified as being involved in increased angiogenesis in breast cancers, and three other genes, SEMA4F, PLXNA2 and PLXNA3, which in the literature were associated with tumourigenesis, but not directly in breast tumourigenesis. The microarray analysis revealed that SEMA4D was significantly (P=0.0347) down-regulated in the grade III tumours compared to benign tumours; SEMA4F, was significantly (P=0.0159) down-regulated between grades I and II tumours; PLXNA2 was significantly (P=0.036) down-regulated between grade III and benign tumours and PLXNA3 significantly (P=0.042) up-regulated between grades I and II tumours. Gene expression of SEMA4D was validated using Q-PCR, demonstrating the same expression profile in both data sets. When the sample set was increased to incorporate more cases, SEMA4D continued to follow the same expression profile, including statistical significance for the differences observed and small standard deviations. In vitro the same pattern was present where expression for SEMA4D was significantly higher in MDA-MB-231 cells when compared to MCF-7 cells. The expression of SEMA4F, PLXNA2 and PLXNA3 could not be validated using Q-PCR, however in vitro analysis of these three genes revealed that both SEMA4F and PLXNA3 followed the microarray trend in expression, although they did not reach significance. In contrast, PLXNA2 demonstrated statistical significance and was in concordance with the literature. DISCUSSION: We, and others, have proposed SEMA4D to be a gene with a potentially protective effect in benign tumours that contributes to tumour growth and metastatic suppression. Previous data supports a role for SEMA4F as a tumour suppressor in the peripheral nervous system but our data seems to indicate that the gene is involved in tumour progression in breast cancer. Our in vitro analysis of PLXNA2 revealed that the gene has higher expression in more aggressive breast cancer cell types. Finally, our in vitro analysis on PLXNA3 also suggest that this gene may have some form of growth suppressive role in breast cancer, in addition to a similar role for the gene previously reported in ovarian cancer. From the data obtained in this study, SEMA4D may have a role in more aggressive and potentially metastatic breast tumours. CONCLUSIONS: Semaphorins and their receptors, the plexins, have been implicated in numerous aspects of neural development, however their expression in many other epithelial tissues suggests that the semaphorin-plexin signalling system also contributes to blood vessel growth and development. These findings warrant further investigation of the role of semaphorins and plexins and their role in normal and tumour-induced angiogenesis in vivo and in vitro. This may represent a new front of attack in anti-angiogenic therapies of breast and other cancers.

This study aimed to explore Semaphrin4D (Sema4D) expression and clinical significance in non-small cell lung cancer (NSCLC), and to define the roles and mechanisms of Sema4D in regulating the malignant behaviors of A549 cells by small interfering RNA (siRNA). Firstly, immunohistochemistry revealed that Sema4D was more frequently expressed in NSCLC than in lung benign lesion (P<0.05) and its overexpression was associated with low differentiation (P<0.05), poor pTNM staging (P<0.05) and occurrence of lymph node (LN) metastasis (P<0.05). Endogenous Sema4D expression was suppressed by Sema4D siRNA in A549 cells overexpressing Sema4D. Protein levels of Sema4D, total Akt and p-Akt were examined by Western blotting. Cell proliferation, migration and invasion abilities were measured by MTT assay and Transwell assay respectively. Results showed that Sema4D siRNA significantly suppressed phosphorylation of AKT in A549 cells, but it did not alter total AKT expression. In addition, efficient down-regulation of SemaD significantly inhibit cell proliferation (P<0.05), migration (P<0.05) and invasion (P<0.05) in A549 cells. These findings suggest that Sema4D might serve as a reliable tool for early prediction of NSCLC poor prognosis. Sema4D could play an important role in promoting tumor proliferation, migration and metastasis in the NSCLC, by influencing the Akt protein phosphorylation. Inhibition of Sema4D may be a useful approach for the treatment of NSCLC.