The Role of Semaphorins in Lung Cancer

Advances in SEMA3F regulation of clinically high-incidence cancers

Cancer has become a leading cause of morbidity and mortality in recent years. Its high prevalence has had a severe impact on society. Researchers have achieved fruitful results in the causative factors, pathogenesis, treatment strategies, and cancer prevention. Semaphorin 3F (SEMA3F), a member of the signaling family, was initially reported in the literature to inhibit the growth, invasion, and metastasis of cancer cells in lung cancer. Later studies showed it has cancer-inhibiting effects in malignant tumors such as breast, colorectal, ovarian, oral squamous cell carcinoma, melanoma, and head and neck squamous carcinoma. In contrast, recent studies have reported that SEMA3F is expressed more in hepatocellular carcinoma than in normal tissue and promotes metastasis of hepatocellular carcinoma. We chose lung, breast, colorectal, and hepatocellular carcinomas with high clinical prevalence to review the roles and molecular mechanisms of SEMA3F in these four carcinomas. We concluded with an outlook on clinical interventions for patients targeting SEMA3F.

Neuroimmune Semaphorin 4A in Cancer Angiogenesis and Inflammation: A Promoter or a Suppressor?

Neuroimmune semaphorin 4A (Sema4A), a member of semaphorin family of transmembrane and secreted proteins, is an important regulator of neuronal and immune functions. In the nervous system, Sema4A primarily regulates the functional activity of neurons serving as an axon guidance molecule. In the immune system, Sema4A regulates immune cell activation and function, instructing a fine tuning of the immune response. Recent studies have shown a dysregulation of Sema4A expression in several types of cancer such as hepatocellular carcinoma, colorectal, and breast cancers. Cancers have been associated with abnormal angiogenesis. The function of Sema4A in angiogenesis and cancer is not defined. Recent studies have demonstrated Sema4A expression and function in endothelial cells. However, the results of these studies are controversial as they report either pro- or anti-angiogenic Sema4A effects depending on the experimental settings. In this mini-review, we discuss these findings as well as our data on Sema4A regulation of inflammation and angiogenesis, which both are important pathologic processes underlining tumorigenesis and tumor metastasis. Understanding the role of Sema4A in those processes may guide the development of improved therapeutic treatments for cancer.

Oncogenomics of c-Myc transgenic mice reveal novel regulators of extracellular signaling, angiogenesis and invasion with clinical significance for human lung adenocarcinoma

The c-Myc transcription factor is frequently deregulated in cancers. To search for disease diagnostic and druggable targets a transgenic lung cancer disease model was investigated. Oncogenomics identified c-Myc target genes in lung tumors. These were validated by RT-PCR, Western Blotting, EMSA assays and ChIP-seq data retrieved from public sources. Gene reporter and ChIP assays verified functional importance of c-Myc binding sites. The clinical significance was established by RT-qPCR in tumor and matched healthy control tissues, by RNA-seq data retrieved from the TCGA Consortium and by immunohistochemistry recovered from the Human Protein Atlas repository. In transgenic lung tumors 25 novel candidate genes were identified. These code for growth factors, Wnt/β-catenin and inhibitors of death receptors signaling, adhesion and cytoskeleton dynamics, invasion and angiogenesis. For 10 proteins over-expression was confirmed by IHC thus demonstrating their druggability. Moreover, c-Myc over-expression caused complete gene silencing of 12 candidate genes, including Bmp6, Fbln1 and Ptprb to influence lung morphogenesis, invasiveness and cell signaling events. Conversely, among the 75 repressed genes TNFα and TGF-β pathways as well as negative regulators of IGF1 and MAPK signaling were affected. Additionally, anti-angiogenic, anti-invasive, adhesion and extracellular matrix remodeling and growth suppressive functions were repressed. For 15 candidate genes c-Myc-dependent DNA binding and transcriptional responses in human lung cancer samples were confirmed. Finally, Kaplan-Meier survival statistics revealed clinical significance for 59 out of 100 candidate genes, thus confirming their prognostic value. In conclusion, previously unknown c-Myc target genes in lung cancer were identified to enable the development of mechanism-based therapies.

Suppression of miR-221 inhibits glioma cells proliferation and invasion via targeting SEMA3B

Background

Gliomas are the most common primary tumors in the central nervous system. Due to complicated signaling pathways involved in glioma progression, effective targets for treatment and biomarkers for prognosis prediction are still scant.

Results

In this study we revealed that a new microRNA (miR), the miR-221, was highly expressed in the glioma cells, and suppression of miR-221 resulted in decreased cellular proliferation, migration, and invasion in glioma cells. Mechanistic experiments validated that miR-221 participates in regulating glioma cells proliferation and invasion via suppression of a direct target gene, the Semaphorin 3B (SEMA3B). The rescue experiment with miR-221 and SEMA3B both knockdown results in significant reversion of miR-221 induced phenotypes.

Conclusion

Taken together, our findings highlight an unappreciated role for miR-221 and SEMA3B in glioma.

Semaphorin-plexin signalling genes associated with human breast tumourigenesis

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® 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 (p≤0.05) differentially expressed between grades I and II tumours 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.

Identification of potential therapeutic targets by gene-expression profiling in pancreatic endocrine tumors

BACKGROUND & AIMS

Prediction of biological behavior in pancreatic endocrine tumors (PET) is difficult on histologic criteria alone. The aim of this study was to characterize PET gene expression by complementary DNA (cDNA) microarray and identify specific differences in gene-expression profiles between nonmetastatic and metastatic tumors.

METHODS

We studied 24 well-differentiated PETs corresponding to 12 benign tumors and to 12 carcinomas with metastasis. Total RNAs were extracted followed by microarray hybridization, imaging scan procedure, and statistical anaylsis. PET tissue arrays were constructed from 129 archival tumors for immunohistochemical validation of microarray data.

RESULTS

A total of 123 transcripts were found to separate nonmetastatic from metastatic PETs (ie, 72 up-regulated and 51 down-regulated genes in malignant tumors). Some of these genes were involved in pathways related to (1) angiogenesis and remodeling (CD34, cadherin-5, E-selectin, semaphorin E, and fibrillin), (2) signal transduction through tyrosine kinases (tyrosine kinase-2, platelet-derived growth factor-Rbeta, MKK4, and discoidin domain receptor-1), (3) calcium-dependent cell signaling (transient receptor potential cation channel-1, calcium channel voltage-dependent beta2, neurocalcin delta, and GABA-A receptor gamma2), and (4) response to drug (MDR1 and carcinoembryonic antigen-related cell adhesion molecule 6). By using tissue arrays, we confirmed the differential expression of CD34 (P = .0008), E-selectin (P = .003), MKK4 (P = .0001), and MDR1 (P = .0003) in metastatic vs nonmetastatic PETs.

CONCLUSIONS

This study provides insight into tumorigenic pathways in PET. Some of the genes identified are potentially new molecular markers for the detection and treatment of these tumors.

Profiling estrogen-regulated gene expression changes in normal and malignant human ovarian surface epithelial cells

Estrogens regulate normal ovarian surface epithelium (OSE) cell functions but also affect epithelial ovarian cancer (OCa) development. Little is known about how estrogens play such opposing roles. Transcriptional profiling using a cDNA microarray containing 2400 named genes identified 155 genes whose expression was altered by estradiol-17beta (E2) in three immortalized normal human ovarian surface epithelial (HOSE) cell lines and 315 genes whose expression was affected by the hormone in three established OCa (OVCA) cell lines. All but 19 of the genes in these two sets were different. Among the 19 overlapping genes, five were found to show discordant responses between HOSE and OVCA cell lines. The five genes are those that encode clone 5.1 RNA-binding protein (RNPS1), erythrocyte adducin alpha subunit (ADD1), plexin A3 (PLXNA3 or the SEX gene), nuclear protein SkiP (SKIIP), and Rap-2 (rap-2). RNPS1, ADD1, rap-2, and SKIIP were upregulated by E2 in HOSE cells but downregulated by estrogen in OVCA cells, whereas PLXNA3 showed the reverse pattern of regulation. The estrogen effects was observed within 6-18 h of treatment. In silicon analyses revealed presence of estrogen response elements in the proximal promoters of all five genes. RNPS1, ADD1, and PLXNA3 were underexpressed in OVCA cell lines compared to HOSE cell lines, while the opposite was true for rap-2 and SKIIP. Functional studies showed that RNPS1 and ADD1 exerted multiple antitumor actions in OVCA cells, while PLXNA3 only inhibited cell invasiveness. In contrast, rap-2 was found to cause significant oncogenic effects in OVCA cells, while SKIIP promotes only anchorage-independent growth. In sum, gene profiling data reveal that (1) E2 exerts different actions on HOSE cells than on OVCA cells by affecting two distinct transcriptomes with few overlapping genes and (2) among the overlapping genes, a set of putative oncogenes/tumor suppressors have been identified due to their differential responses to E2 between the two cell types. These findings may explain the paradoxical roles of estrogens in regulating normal and malignant OSE cell functions.