Experimental hypoxia does not influence gene expression and protein synthesis of Eph receptors and ephrin ligands in human melanoma cells in vitro

Therapeutic Potential of Nitric Oxide‒Releasing Selective Estrogen Receptor Modulators in Malignant Melanoma

Malignant melanoma has a steadily increasing incidence, but treatment options are still limited, and the prognosis for patients, especially for men, is poor. To investigate whether targeting estrogen receptor (ER) signaling is a valid therapeutic approach, we retrospectively analyzed ER gene expression profiles in 448 patients with melanoma. High ERα gene (ESR1) expression was associated with improved overall survival (hazard ratio = 0.881; 95% confidence interval = 0.793-0.979; P = 0.018) and increased with tumor stage, whereas ERβ gene (ESR2) expression did not change with tumor progression. This seemingly protective function of ERα led us to speculate that specific targeting of ERβ has a therapeutic benefit in malignant melanoma. An ERβ-selective ER modulator with nitric oxide‒releasing moiety (nitric oxide‒releasing selective ER modulator 4d [NO-SERM 4d]) significantly reduced the prometastatic behavior of two melanoma cell lines (A2058 and MEL-JUSO). Epithelial‒mesenchymal transition in melanoma is consistent with a switch from E- to N-cadherin expression, mediating the invasive phenotype. NO-SERM 4d reduced N-cadherin expression and impaired spheroid formation in A2058 cells. In addition, the growth of A2058 spheroids was significantly reduced, confirming the antitumorigenic potential of NO-SERM 4d. Targeting ERβ signaling combined with targeted nitric oxide release represents a promising therapeutic approach in malignant melanoma that has the potential to prevent metastatic spread and reduce tumor growth.

CRISPR/Cas9 Mediated Knockout of Cyclooxygenase-2 Gene Inhibits Invasiveness in A2058 Melanoma Cells

The inducible isoenzyme cyclooxygenase-2 (COX-2) is an important hub in cellular signaling, which contributes to tumor progression by modulating and enhancing a pro-inflammatory tumor microenvironment, tumor growth, apoptosis resistance, angiogenesis and metastasis. In order to understand the role of COX-2 expression in melanoma, we investigated the functional knockout effect of COX-2 in A2058 human melanoma cells. COX-2 knockout was validated by Western blot and flow cytometry analysis. When comparing COX-2 knockout cells to controls, we observed significantly reduced invasion, colony and spheroid formation potential in cell monolayers and three-dimensional models in vitro, and significantly reduced tumor development in xenograft mouse models in vivo. Moreover, COX-2 knockout alters the metabolic activity of cells under normoxia and experimental hypoxia as demonstrated by using the radiotracers [¹⁸F]FDG and [¹⁸F]FMISO. Finally, a pilot protein array analysis in COX-2 knockout cells verified significantly altered downstream signaling pathways that can be linked to cellular and molecular mechanisms of cancer metastasis closely related to the enzyme. Given the complexity of the signaling pathways and the multifaceted role of COX-2, targeted suppression of COX-2 in melanoma cells, in combination with modulation of related signaling pathways, appears to be a promising therapeutic approach.

The differential expression of EPHB4 and ephrin B2 in cutaneous squamous cell carcinoma according to the grade of tumor differentiation: a clinicopathological study

BACKGROUND

EPHB4 and its ligand, ephrin B2, which are receptor tyrosine kinases of the erythropoietin-producing hepatocellular (EPH) family, are known to be linked to several human cancers. The aim of this study was to investigate their expression patterns in cutaneous squamous cell carcinoma (CSCC) in association with tumor differentiation and other variable clinical characteristics.

MATERIALS AND METHODS

Immunohistochemical staining for EPHB4 and ephrin B2 was performed in 32 cases of CSCC with different histologic grades. The clinical characteristics and histologic grades of CSCC were evaluated in association with EPHB4 and ephrin B2 expression patterns.

RESULTS

EPHB4 and ephrin B2 expression levels were significantly inversely proportional to the grade of differentiation of CSCC (P < 0.001 and P < 0.001, respectively).

CONCLUSION

These results indicated that EPHB4 and ephrin B2 can be useful markers for poorly differentiated CSCC.

Three-Dimensional Cell Culture Systems in Radiopharmaceutical Cancer Research

In preclinical cancer research, three-dimensional (3D) cell culture systems such as multicellular spheroids and organoids are becoming increasingly important. They provide valuable information before studies on animal models begin and, in some cases, are even suitable for reducing or replacing animal experiments. Furthermore, they recapitulate microtumors, metastases, and the tumor microenvironment much better than monolayer culture systems could. Three-dimensional models show higher structural complexity and diverse cell interactions while reflecting (patho)physiological phenomena such as oxygen and nutrient gradients in the course of their growth or development. These interactions and properties are of great importance for understanding the pathophysiological importance of stromal cells and the extracellular matrix for tumor progression, treatment response, or resistance mechanisms of solid tumors. Special emphasis is placed on co-cultivation with tumor-associated cells, which further increases the predictive value of 3D models, e.g., for drug development. The aim of this overview is to shed light on selected 3D models and their advantages and disadvantages, especially from the radiopharmacist's point of view with focus on the suitability of 3D models for the radiopharmacological characterization of novel radiotracers and radiotherapeutics. Special attention is paid to pancreatic ductal adenocarcinoma (PDAC) as a predestined target for the development of new radionuclide-based theranostics.

Evaluation of Fluorine-18-Labeled α1(I)-N-Telopeptide Analogs as Substrate-Based Radiotracers for PET Imaging of Melanoma-Associated Lysyl Oxidase

Accumulating evidence suggests an unequivocal role of lysyl oxidases as key players of tumor progression and metastasis, which renders this enzyme family highly attractive for targeted non-invasive functional imaging of tumors. Considering their function in matrix remodeling, malignant melanoma appears as particularly interesting neoplasia in this respect. For the development of radiotracers that enable PET imaging of the melanoma-associated lysyl oxidase activity, substrates derived from the type I collagen α1 N-telopeptide were labeled with fluorine-18 using N-succinimidyl 4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) as prosthetic reagent. With regards to potential crosslinking to tumor-associated collagen in vivo, their interaction with triple-helical type I collagen was studied by SPR. A mouse model of human melanoma was established on the basis of the A375 cell line, for which the expression of the oncologically relevant lysyl oxidase isoforms LOX and LOXL2 was demonstrated in Western blot and immunohistochemical experiments. The radiopharmacological profiles of the peptidic radiotracers were evaluated in normal rats and A375 melanoma-bearing mice by ex vivo metabolite analysis, whole-body biodistribution studies and dynamic PET imaging. Out of three ¹⁸F-labeled telopeptide analogs, the one with the most favorable substrate properties has shown favorable tumor uptake and tumor-to-muscle ratio. Lysyl oxidase-mediated tumor uptake was proven by pharmacological inhibition using β-aminopropionitrile and by employing negative-control analogs of impeded or abolished targeting capability. The latter were obtained by substituting the lysine residue by ornithine and norleucine, respectively. Comparing the tumor uptake of the lysine-containing peptide with that of the non-functional analogs indicate the feasibility of lysyl oxidase imaging in melanoma using substrate-based radiotracers.

Bridging from Brain to Tumor Imaging: (S)-(-)- and (R)-(+)-[18F]Fluspidine for Investigation of Sigma-1 Receptors in Tumor-Bearing Mice

Sigma-1 receptors (Sig1R) are highly expressed in various human cancer cells and hence imaging of this target with positron emission tomography (PET) can contribute to a better understanding of tumor pathophysiology and support the development of antineoplastic drugs. Two Sig1R-specific radiolabeled enantiomers (S)-(-)- and (R)-(+)-[18F]fluspidine were investigated in several tumor cell lines including melanoma, squamous cell/epidermoid carcinoma, prostate carcinoma, and glioblastoma. Dynamic PET scans were performed in mice to investigate the suitability of both radiotracers for tumor imaging. The Sig1R expression in the respective tumors was confirmed by Western blot. Rather low radiotracer uptake was found in heterotopically (subcutaneously) implanted tumors. Therefore, a brain tumor model (U87-MG) with orthotopic implantation was chosen to investigate the suitability of the two Sig1R radiotracers for brain tumor imaging. High tumor uptake as well as a favorable tumor-to-background ratio was found. These results suggest that Sig1R PET imaging of brain tumors with [18F]fluspidine could be possible. Further studies with this tumor model will be performed to confirm specific binding and the integrity of the blood-brain barrier (BBB).

Overexpression of Receptor Tyrosine Kinase EphB4 Triggers Tumor Growth and Hypoxia in A375 Melanoma Xenografts: Insights from Multitracer Small Animal Imaging Experiments

Experimental evidence has associated receptor tyrosine kinase EphB4 with tumor angiogenesis also in malignant melanoma. Considering the limited in vivo data available, we have conducted a systematic multitracer and multimodal imaging investigation in EphB4-overexpressing and mock-transfected A375 melanoma xenografts. Tumor growth, perfusion, and hypoxia were investigated by positron emission tomography. Vascularization was investigated by fluorescence imaging in vivo and ex vivo. The approach was completed by magnetic resonance imaging, radioluminography ex vivo, and immunohistochemical staining for blood and lymph vessel markers. Results revealed EphB4 to be a positive regulator of A375 melanoma growth, but a negative regulator of tumor vascularization. Resulting in increased hypoxia, this physiological characteristic is considered as highly unfavorable for melanoma prognosis and therapy outcome. Lymphangiogenesis, by contrast, was not influenced by EphB4 overexpression. In order to distinguish between EphB4 forward and EphrinB2, the natural EphB4 ligand, reverse signaling a specific EphB4 kinase inhibitor was applied. Blocking experiments show EphrinB2 reverse signaling rather than EphB4 forward signaling to be responsible for the observed effects. In conclusion, functional expression of EphB4 is considered a promising differentiating characteristic, preferentially determined by non-invasive in vivo imaging, which may improve personalized theranostics of malignant melanoma.

Paradoxes of the EphB1 receptor in malignant brain tumors

Eph receptors are a subfamily of receptor tyrosine kinases. Eph receptor-mediated forward and ephrin ligand-mediated reverse signalings are termed bidirectional signaling. Increasing evidence shows that Eph/ephrin signaling regulates cell migration, adhesion, morphological changes, differentiation, proliferation and survival through cell–cell communication. Some recent studies have started to implicate Eph/ephrin signaling in tumorigenesis, metastasis, and angiogenesis. Previous studies have shown that EphB1 receptor and its ephrin ligands are expressed in the central nervous system. EphB1/ephrin signaling plays an important role in the regulation of synapse formation and maturation, migration of neural progenitors, establishment of tissue patterns, and the development of immune organs. Besides, various recent studies have detected the abnormal expression of EphB1 receptor in different brain tumors. However, the underlying molecular mechanisms of EphB1/ephrins signaling in the development of these tumors are not fully understood. This review focuses on EphB1 that has both tumor-suppressing and -promoting roles in some brain tumors. Understanding the intracellular mechanisms of EphB1 in tumorigenesis and metastasis of brain tumors might provide a foundation for the development of EphB1-targeted therapies.

Expression of ephrinB2 and EphB4 in a neonatal rat model of periventricular white matter damage

BACKGROUND

Periventricular white matter damage (PWMD), also termed periventricular leukomalacia, is the predominant neurologic lesion in preterm infants. It appears to relate in part to the development of the vascular supply to the cerebral white matter. We investigated whether, in case of severe hypoxia-ischemia, the vascular system would be subject to severe damage or remodeled.

AIMS

To evaluate microvessel density (MVD) and the use of ephrinB2 and its receptor EphB4 to mark arterioles and venules to establish the correct anatomic assignment of the remodeled vessels in a hypoxia-induced PWMD rat model.

METHODS

Postnatal day 3 rats underwent permanent ligation of the right common carotid artery followed by 6% O2 for 4 h (hypoxia-ischemia) or sham operation and normoxic exposure (sham). MVD and levels of ephrinB2 and EphB4, which are respectively regarded as relatively specific molecular markers of arteries and veins, were determined at postnatal day 7.

RESULTS

Compared with sham rats, MVD, ephrinB2 and EphB4 levels were higher in the brains of hypoxic-ischemic rats. Similar percentages of vessels expressed ephrinB2 and EphB4 in sham rats, but expression of ephrinB2 was greater in brains injured by hypoxia-ischemia.

CONCLUSIONS

Following hypoxic-ischemic injury to the rat brain, microvessels were remodeled and more arterioles than venules were acquired.

Coculture of stem cells from apical papilla and human umbilical vein endothelial cell under hypoxia increases the formation of three-dimensional vessel-like structures in vitro

The success of bioengineered dental pulp depends on two principles, (1) whether the transplanted tissue can develop its own vascular endothelial tubule network and (2) whether the host vasculature can be induced to penetrate the bioengineered pulp replacement and conjoin. Major inductive molecules that participate in laying down blood vessels include vascular endothelial growth factor (VEGF), ephrinB2, and hypoxia-inducible factor 1α (HIF-1α). Being able to modulate the genes encoding these angiogenic molecules is a therapeutic target in pulp regeneration for endogenous blood vessel formation, prevention of graft rejection, and exclusion of infection. Once implanted inside the root canal, bioengineered pulp is subjected to severe hypoxia that causes tissue degeneration. However, short-term hypoxia is known to stimulate angiogenesis. Thus, it may be feasible to prime dental cells for angiogenic activity before implantation. Stem cells from apical papilla (SCAP) are arguably one of the most potent and versatile dental stem cell populations for bioengineering pulp in vitro. Our study aimed to investigate whether coculture of SCAP and human umbilical vein endothelial cells (HUVECs) under hypoxia promotes the formation of endothelial tubules and a blood vessel network. In addition, we clarified the interplay between the genes that orchestrate these important angiogenic molecules in SCAP under hypoxic conditions. We found that SCAP cocultured with HUVEC at a 1:5 ratio increased the number of endothelial tubules, tubule lengths, and branching points. Fluorescence staining showed that HUVEC formed the trunk of tubular structures, whereas SCAP located adjacent to the endothelial cell line, resembling the pericyte location. When we used CoCl2 (0.5 mM) to induce hypoxic environment, the expression of proteins, HIF-1α and VEGF, and transcript of ephrinB2 in SCAP was upregulated. However, minimal VEGF levels in supernatants of HUVEC and coculture Petri dishes were detected, suggesting that VEGF secreted by SCAP might be used by HUVEC to accelerate the formation of vessel-like structures. Taken together, we revealed that artificial hypoxia stimulates angiogenic responses in SCAP for possible use in engineering dental pulp replacements. Our results may help to delineate the optimal therapeutic target to promote angiogenesis so that future bioengineered pulp replacements integrate faster and permanently within the host.

EPHB4 tyrosine-kinase receptor expression and biological significance in soft tissue sarcoma

Soft tissue sarcomas (STS) are heterogeneous malignant tumors of mesenchymal origin. Due to low incidence and high number of different histological subtypes, their pathogenesis and thus potential targets for their therapy remain barely investigated. Several studies revealed significant higher EPHB4 expression in malignancies such as prostate and colorectal cancer showing survival advantages for these tumor cells. Therefore we studied the expression of EPHB4 in a total of 46 clinical human specimens of different STS and human fibroblasts. EPHB4 mRNA and protein expression were significantly increased in synovial sarcoma. After targeting EPHB4 in fibrosarcoma, synovial sarcoma, liposarcoma and MFH sarcoma cell lines by siRNA or by inhibition of autophosphorylation using the specific EPHB4 kinase inhibitor NVP-BHG712 a decreased proliferation rate/vitality of synovial- and fibrosarcoma cells was observed. Silencing of EPHB4 significantly reduced the transmigration of synovial sarcoma cells towards fibroblasts and endothelial cells. In addition, we assessed the anti-metastatic effect of EPHB4 inhibition in vivo by intraperitoneal administration of the EPHB4 inhibitor in an appropriate sarcoma lung metastasis xenograft model. As result 43% of NVP-BHG712 treated mice (n = 3/7) developed pulmonary metastases whereas all control mice (n = 5) revealed lung metastases. The residual 57% of mice (n = 4/7) showed only small local tumor cell spots. Size measurements of the Vimentin positive area explained significant decrease in lung metastasis formation (p < 0.05) after EPHB4 kinase inhibition. In summary, these data provide first evidence of the importance of EPHB4 in the tumorigenesis of synovial sarcoma and present EPHB4 as a potential target in the therapy of this malignancy.

IL-17A promotes the migration and invasiveness of cervical cancer cells by coordinately activating MMPs expression via the p38/NF-κB signal pathway

Objective

IL-17A plays an important role in many inflammatory diseases and cancers. We aimed to examine the effect of IL-17A on the invasion of cervical cancer cells and study its related mechanisms.

Methods

Wound healing and matrigel transwell assays were used to examine the effect of IL-17A on cervical cancer cell migration and invasion by a panel of cervical cancer cell lines. The levels of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) were investigated using western blotting. The activity of p38 and nuclear factor-kappa B (NF-κB) signal pathway was detected too.

Results

Here, we showed that IL-17A could promote the migration and invasion of cervical cancer cells. Further molecular analysis showed that IL-17A could up-regulate the expressions and activities of MMP2 and MMP9, and down-regulate the expressions of TIMP-1 and TIMP-2. Furthermore, IL-17A also activates p38 signal pathway and increased p50 and p65 nuclear expression. In addition, treatment of cervical cancer cells with the pharmacological p38/NF-κB signal pathway inhibitors, SB203580 and PDTC, potently restored the roles of invasion and upregulation of MMPs induced by IL-17A.

Conclusion

IL-17A could promote the migration and invasion of cervical cancer cell via up-regulating MMP2 and MMP9 expression, and down-regulating TIMP-1 and TIMP-2 expression via p38/NF-κB signal pathway. IL-17A may be a potential target to improve the prognosis for patients with cervical cancer.