Genomic profiling of invasive melanoma cell lines by array comparative genomic hybridization

Expression pattern of osteopontin isoforms in malignant melanoma cell lines

Osteopontin (OPN) is a secreted integrin-binding protein that plays a role in inflammation, cellular viability, cell adhesion and migration, cancer development, and diabetes through different mechanisms. The splice variants of OPN can play essential roles in cancer development, progression, and metastasis formation; however, limited data are available about the role of OPN isoforms in human malignant melanoma. Our goal was to define the gene expression patterns of five OPN variants (OPN4, OPN5, OPNa, OPNb, and OPNc), integrin, and CD44 receptor genes in primary and metastatic melanoma-originated cell lines (n = 19), and to explore the association of the expression patterns with clinicopathological parameters. We evaluated the invasive property of the cell lines and investigated the potential association between the invasion and gene expression of OPN isoforms. We found a significant rise in the expression of OPNc in the invasive cell lines compared to the noninvasive cells and detected significantly higher expression of the OPN splice variants in melanoma cell lines originating from more advanced stages tumors than cell lines originating from early-stage melanomas. The correlation analysis revealed that all five OPN variants positively correlated with ITGB3 and ITGA9, whereas OPN5 positively correlated with ITGB1, ITGAV, ITGA6, and CD44. OPN can activate extracellular signal-regulated kinase signaling through binding to α9β1 integrin, promoting melanoma tumor cell migration. It is possible that such associations between OPN splice variants and integrin receptors may play a role in melanoma progression. In conclusion, our findings suggest that high expression of OPNc correlates with the invasive behavior of melanoma cells.

Molecular Alterations Associated with Acquired Drug Resistance during Combined Treatment with Encorafenib and Binimetinib in Melanoma Cell Lines

Combination treatment using BRAF/MEK inhibitors is a promising therapy for patients with advanced BRAF^V600E/K mutant melanoma. However, acquired resistance largely limits the clinical efficacy of this drug combination. Identifying resistance mechanisms is essential to reach long-term, durable responses. During this study, we developed six melanoma cell lines with acquired resistance for BRAFi/MEKi treatment and defined the molecular alterations associated with drug resistance. We observed that the invasion of three resistant cell lines increased significantly compared to the sensitive cells. RNA-sequencing analysis revealed differentially expressed genes that were functionally linked to a variety of biological functions including epithelial-mesenchymal transition, the ROS pathway, and KRAS-signalling. Using proteome profiler array, several differentially expressed proteins were detected, which clustered into a unique pattern. Galectin showed increased expression in four resistant cell lines, being the highest in the WM1617^E+BRes cells. We also observed that the resistant cells behaved differently after the withdrawal of the inhibitors, five were not drug addicted at all and did not exhibit significantly increased lethality; however, the viability of one resistant cell line (WM1617^E+BRes) decreased significantly. We have selected three resistant cell lines to investigate the protein expression changes after drug withdrawal. The expression patterns of CapG, Enolase 2, and osteopontin were similar in the resistant cells after ten days of "drug holiday", but the Snail protein was only expressed in the WM1617^E+BRes cells, which showed a drug-dependent phenotype, and this might be associated with drug addiction. Our results highlight that melanoma cells use several types of resistance mechanisms involving the altered expression of different proteins to bypass drug treatment.

Silencing Osteopontin Expression Inhibits Proliferation, Invasion and Induce Altered Protein Expression in Melanoma Cells

Osteopontin (OPN) is a multifunctional phosphoprotein that is expressed in different types of cancers, including melanoma. OPN overexpression is associated with tumor progression and metastasis formation; however, the role of OPN in cell invasion and metastasis formation is not completely understood. In this study we aimed to define OPN expression in melanoma tissues and cell lines and investigate the effect of OPN expression on cell proliferation and invasion after inhibiting OPN expression with small interfering RNA (siRNA). OPN gene expression was determined by qRT-PCR, while protein expression was examined using a Proteome Profiler Oncology Array. siRNA-mediated OPN knockdown led to decreased OPN expression in melanoma cell lines, which was associated with decreased cell proliferation and invasion. Proteome profile analysis revealed significantly different protein expression between the original and transfected cell lines. The altered expression of the differently expressed proteins was validated at the mRNA level. Furthermore, OPN-specific siRNA was able to reduce OPN expression and inhibit the invasiveness of melanoma cells. Our results revealed for the first time that silencing the OPN gene influences proliferation and invasion of melanoma cells by effecting EGFR, tenascin C, survivin, galectin-3 and enolase 2 expression. To predict protein-protein interactions along with putative pathways we used STRING analysis for the differentially expressed proteins. These proteins formed multiple clusters, including extracellular matrix organization, regulation of angiogenesis, cell death and cell migration, PI3K-Akt, MAPK and focal adhesion signaling pathways. Taken together these data suggest that OPN might be an ideal target for drug development and therapies.

SHARPIN: Role in Finding NEMO and in Amyloid-Beta Clearance and Degradation (ABCD) Pathway in Alzheimer's Disease?

SHANK- associated RH domain-interacting protein (SHARPIN) is a multifunctional protein associated with numerous physiological functions and many diseases. The primary role of the protein as a LUBAC-dependent component in regulating the activation of the transcription factor NF-κB accounts to its role in inflammation and antiapoptosis. Hence, an alteration of SHARPIN expression or genetic mutations or polymorphisms leads to the alteration of the above-mentioned primary physiological functions contributing to inflammation-associated diseases and cancer, respectively. However, there are complications of targeting SHARPIN as a therapeutic approach, which arises from the wide-range of LUBAC-independent functions and yet unknown roles of SHARPIN including neuronal functions. The identification of SHARPIN as a postsynaptic protein and the emerging studies indicating its role in several neurodegenerative diseases including Alzheimer's disease suggests a strong role of SHARPIN in neuronal functioning. This review summarizes the functional roles of SHARPIN in normal physiology and disease pathogenesis and strongly suggests a need for concentrating more studies on identifying the unknown neuronal functions of SHARPIN and hence its role in neurodegenerative diseases.

Progress in the correlation between PTPN12 gene expression and human tumors

BACKGROUND

The global morbidity of cancer is rising rapidly. Despite advances in molecular biology, immunology, and cytotoxic and immune-anticancer therapies, cancer remains a major cause of death worldwide. Protein tyrosine phosphatase non-receptor type 12 (PTPN12) is a new member of the cytoplasmic protein tyrosine phosphatase family, isolated from a cDNA library of adult colon tissue. Thus far, no studies have reviewed the correlation between PTPN12 gene expression and human tumors.

METHODS

This article summarizes the latest domestic and international research developments on how the expression of PTPN12 relates to human tumors. The extensive search in Web of Science and PubMed with the keywords including PTPN12, tumor, renal cell carcinoma, proto-oncogenes, tumor suppressor genes was undertaken.

RESULTS

More and more studies have shown that a tumor is essentially a genetic disease, arising from a broken antagonistic function between proto-oncogenes and tumor suppressor genes. When their antagonistic effect is out of balance, it may cause uncontrolled growth of cells and lead to the occurrence of tumors. PTPN12 is a tumor suppressor gene, so inhibiting its activity will lead directly or indirectly to the occurrence of tumors.

CONCLUSION

The etiology, prevention, and treatment of tumors have become the focus of research around the world. PTPN12 is a tumor suppressor gene. In the future, PTPN12 might serve as a novel molecular marker to benefit patients, and even the development of tumor suppressor gene activation agents can form a practical research direction.

Molecular alterations associated with acquired resistance to BRAFV600E targeted therapy in melanoma cells

Selective inhibition of the mutant BRAF protein is a highly promising therapeutic approach for melanoma patients carrying the BRAF mutation. Despite the remarkable clinical response, most patients develop resistance and experience tumour regrowth. To clarify the molecular background of BRAF inhibitor resistance, we generated four drug-resistant melanoma cell lines from paired primary/metastatic cell lines using a vemurafenib analogue PLX4720. Three of the resistant cell lines showed decreased proliferation after drug withdrawal, but the proliferation of one cell line (WM278) increased notably. Furthermore, we observed opposite phenomena in which a 'drug holiday' could not only be beneficial but also contribute to tumour progression. Using genomic and proteomic approaches, we found significantly different alterations between the sensitive and resistant cell lines, some of which have not been reported previously. In addition to several other changes, copy number gains were observed in all resistant cell lines on 8q24.11-q24.12 and 8q21.2. Gene expression analysis showed that most genes upregulated in the resistant cell lines were associated with cell motility and angiogenesis. Increased expression of six proteins (ANGPLT4, EGFR, Endoglin, FGF2, SerpinE1 and VCAM-1) and decreased expression of two proteins (osteopontin and survivin) were observed consistently in all resistant cell lines. In summary, we identified new genomic alterations and characterized the protein expression patterns associated with the resistant phenotype. Although several proteins have been shown to be associated with BRAF resistance, our study is the first to describe the association of VCAM-1 and osteopontin with BRAF resistance.

Combined mTOR and MEK inhibition is an effective therapy in a novel mouse model for angiosarcoma

Angiosarcoma is an aggressive malignancy of vascular origin that occurs de novo or in the context of previous cancer therapy. Despite multi-modal aggressive treatment including surgical resection, chemotherapy, and radiation, five-year overall survival remains poor at 35%. Due to its rarity, little is known about its molecular pathology and clinical trials have been extremely difficult to conduct. Development of animal models for rare diseases like angiosarcoma is critical to improve our understanding of tumorigenesis and to test novel treatment regimens. A genetically engineered mouse model for angiosarcoma was generated by conditional deletion of Trp53, Pten, and Ptpn12 in endothelial cells. Tumors arising from these mice recapitulate the histology and molecular pathology of the human disease including hyperactivation of the PI3K/mTOR and MAPK signaling pathways. Treatment of tumor-bearing mice with mTOR or MEK inhibitors effectively inactivated signaling and resulted in reduced proliferation and elevated apoptosis leading to tumor regression. The effect of treatment on tumor growth was transient and proliferation was restored after a period of dormancy. However, combined inhibition of mTOR and MEK resulted in profound tumor regression which was sustained for the duration of treatment. These results suggest that angiosarcoma may be effectively treated by this drug combination. 

The GDNF Family: A Role in Cancer?

The glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFLs) comprising of GDNF, neurturin, artemin, and persephin plays an important role in the development and maintenance of the central and peripheral nervous system, renal morphogenesis, and spermatogenesis. Here we review our current understanding of GFL biology, and supported by recent progress in the area, we examine their emerging role in endocrine-related and other non-hormone-dependent solid neoplasms. The ability of GFLs to elicit actions that resemble those perturbed in an oncogenic phenotype, alongside mounting evidence of GFL involvement in tumor progression, presents novel opportunities for therapeutic intervention.