Squamous cell carcinoma related oncogene regulates angiogenesis through vascular endothelial growth factor-A

A comprehensive review on DCN1 protein, inhibitors and their therapeutic applications

DCN1, a critical co-E3 ligase in the neddylation process, mediates the activation of Cullin-RING Ligases (CRLs) by selectively catalyzing cullin neddylation, further regulating the activity of substrate proteins. It has been identified as an important target for human diseases, including cancers, fibrotic diseases, and cardiovascular disorders. This work aims to provide a perspective for the discovery of novel DCN1 inhibitors by the analysis of biological roles, protein structures, structure-activity relationships and design strategy disclosed in recent years. Additionally, we will discuss the current status, challenges and opportunities in hope of offering insights into the development of DCN1 inhibitors for human diseases.

Endoplasmic reticulum stress impedes regulated secretion by governing key exocytotic and granulogenic molecular switches

Dense core vesicles (DCVs) and synaptic vesicles are specialised secretory vesicles in neurons and neuroendocrine cells, and abnormal release of their cargo is associated with various pathophysiologies. Endoplasmic reticulum (ER) stress and inter-organellar communication are also associated with disease biology. To investigate the functional status of regulated exocytosis arising from the crosstalk of a stressed ER and DCVs, ER stress was modelled in PC12 neuroendocrine cells using thapsigargin. DCV exocytosis was severely compromised in ER-stressed PC12 cells and was reversed to varying magnitudes by ER stress attenuators. Experiments with tunicamycin, an independent ER stressor, yielded similar results. Concurrently, ER stress also caused impaired DCV exocytosis in insulin-secreting INS-1 cells. Molecular analysis revealed blunted SNAP25 expression, potentially attributed to augmented levels of ATF4, an inhibitor of CREB that binds to the CREB-binding site. The effects of loss of function of ATF4 in ER-stressed cells substantiated this attribution. Our studies revealed severe defects in DCV exocytosis in ER-stressed cells for the first time, mediated by reduced levels of key exocytotic and granulogenic switches regulated via the eIF2α (EIF2A)-ATF4 axis.

DCUN1D1, a new molecule involved in depigmentation via upregulating CXCL10

CD8⁺ T cells in the lesioned site play a crucial role in the pathogenesis of vitiligo. The chemokine CXCL10 secreted by keratinocytes regulates the migration of CD8⁺ T cells into the skin. In our previous study, we found that DCUN1D1 expression in vitiligo lesions positively correlates with Cxcl10 expression. In this study, the regulatory effect of DCUN1D1 on CXCL10 and cell function was investigated. DCUN1D1 protein expression was significantly higher in the skin tissue from vitiligo lesions compared with samples from healthy controls. High expression of DCUN1D1 in keratinocytes caused local hair depigmentation in mice, reduced melanin content, high infiltration of CD8⁺ T cells and increased CXCL10 expression. This suggested that DCUN1D1 may regulate CD8⁺ T-cell infiltration and depigmentation through CXCL10. Inhibition of DCUN1D1 expression in HaCaT cells abolished the IFN-γ-induced upregulation of p-JAK1, p-STAT1 and CXCL10, suppressed the H₂ O₂ -induced ROS generation and apoptosis, and upregulated tyrosinase expression in melanocytes. Collectively, these results show that DCUN1D1 is an important regulator of CXCL10 and may be a new target for the treatment of vitiligo.

Evaluation of HZX-960, a novel DCN1-UBC12 interaction inhibitor, as a potential antifibrotic compound for liver fibrosis

Liver fibrosis is a very common health problem and currently lacks effective treatments. Cullin ring E3 ligases (CRLs) regulate the turnover of ~20% of mammalian cell proteins. Neddylation, the process by which NEDD8 is covalently attached to cullin proteins through sequential enzymatic reactions, is critical for the activation of CRLs and was recently found to be elevated in liver fibrosis. NEDD8-activating enzyme E1-specific inhibition led to the reduced liver damage characterized by decreased apoptosis, inflammation and fibrosis. However, the relevance of a co-E3 ligase, DCN1, in liver fibrosis remains unclear. Here, a novel and potent DCN1-UBC12 interaction inhibitor HZX-960 was discovered with an IC50 value of 9.37nM, which could inhibit the neddylation of cullin3. Importantly, we identified that HZX-960 treatment could attenuate TGFβ-induced liver fibrotic responses by reducing the deposition of collagen I and α-SMA, and upregulating cellular NRF2, HO-1 and NQO1 level in two hepatic stellate cell lines. Additionally, DCN1 was shown to be unregulated in CCl4-induced mice liver tissue, and liver fibrotic signaling in mice was reduced by HZX-960. Therefore, our data demonstrated that HZX-960 possessed anti-liver fibrosis ability, and DCN1 may be a potential therapeutic target for liver fibrosis treatment.

Development of phenyltriazole thiol-based derivatives as highly potent inhibitors of DCN1-UBC12 interaction

Defective in cullin neddylation 1(DCN1) is a co-E3 ligase that is important for cullin neddylation. Dysregulation of DCN1 highly correlates with the development of various cancers. Herein, from the initial high-throughput screening, a novel hit compound 5a containing a phenyltriazole thiol core (IC₅₀ value of 0.95 μM for DCN1-UBC12 interaction) was discovered. Further structure-based optimization leads to the development of SK-464 (IC₅₀ value of 26 nM). We found that SK-464 not only directly bound to DCN1 in vitro, but also engaged cellular DCN1, suppressed the neddylation of cullin3, and hindered the migration and invasion of two DCN1-overexpressed squamous carcinoma cell lines (KYSE70 and H2170). These findings indicate that SK-464 may be a novel lead compound targeting DCN1-UBC12 interaction.

Discovery of Novel Pyrazolo-pyridone DCN1 Inhibitors Controlling Cullin Neddylation

Chemical control of cullin neddylation is attracting increased attention based largely on the successes of the NEDD8-activating enzyme (E1) inhibitor pevonedistat. Recently reported chemical probes enable selective and time-dependent inhibition of downstream members of the neddylation trienzymatic cascade including the co-E3, DCN1. In this work, we report the optimization of a novel class of small molecule inhibitors of the DCN1-UBE2M interaction. Rational X-ray co-structure enabled optimization afforded a 25-fold improvement in potency relative to the initial screening hit. The potency gains are largely attributed to additional hydrophobic interactions mimicking the N-terminal acetyl group that drives binding of UBE2M to DCN1. The compounds inhibit the protein-protein interaction, block NEDD8 transfer in biochemical assays, engage DCN1 in cells, and selectively reduce the steady-state neddylation of Cul1 and Cul3 in two squamous carcinoma cell lines harboring DCN1 amplification.

Potent 5-Cyano-6-phenyl-pyrimidin-Based Derivatives Targeting DCN1-UBE2M Interaction

Neddylation of the Cullin-RING E3 ligases (CRLs) regulates the homeostasis of approximately 20% of cellular proteins. Defective in cullin neddylation 1 (DCN1), as a co-E3 ligase, interacts with UBE2M to enhance the activation of CRLs, and this interaction is emerging as a therapeutic target for human diseases. Here, we present a series of pyrimidin-based small molecular inhibitors targeting DCN1-UBE2M interaction. After finding a novel inhibitor DC-1 with IC₅₀ = 1.2 μM, we performed a series of chemical optimizations, which finally led to the discovery of a potent thiazole containing 5-cyano-6-phenylpyrimidin-based inhibitor DC-2 (IC₅₀ = 15 nM). Next, using protein and cellular thermal shift assays, coimmunoprecipitation, molecular docking, and site-specific mutation experiments, we further proved that DC-2 specifically inhibited the interaction of UBE2M and DCN1 at molecule and cellular levels, resulting in the decrease of cullin3 neddylation and accumulation of its substrate, NRF2. Our findings indicate that DC-2 may serve as a novel lead compound for specific derivatives targeting DCN1-UBE2M interaction.

Discovery of an Orally Bioavailable Inhibitor of Defective in Cullin Neddylation 1 (DCN1)-Mediated Cullin Neddylation

We previously reported the discovery, validation, and structure-activity relationships of a series of piperidinyl ureas that potently inhibit the DCN1-UBE2M interaction. We demonstrated that compound 7 inhibits both the DCN1-UBE2M protein-protein interaction and DCN1-mediated cullin neddylation in biochemical assays and reduces levels of steady-state cullin neddylation in a squamous carcinoma cell line harboring DCN1 amplification. Although compound 7 exhibits good solubility and permeability, it is rapidly metabolized in microsomal models (CL_int = 170 mL/min/kg). This work lays out the discovery of an orally bioavailable analogue, NAcM-OPT (67). Compound 67 retains the favorable biochemical and cellular activity of compound 7 but is significantly more stable both in vitro and in vivo. Compound 67 is orally bioavailable, well tolerated in mice, and currently used to study the effects of acute pharmacologic inhibition of the DCN1-UBE2M interaction on the NEDD8/CUL pathway.

Vascular Endothelial Growth Factor-A (VEGF-A) Single Nucleotide Polymorphisms and Endometriosis: Still a Controversial Issue

Endometriosis is a chronic, multifactorial, polygenic gynecological disease. Endometrium has a high angiogenic potential and endometriotic lesions involve large areas with a rich blood supply. Angiogenesis is controlled by numerous inducers, including the vascular endothelial growth factor (VEGF) family. Endometrium undergoes cyclical growth and regression during the menstrual cycle, which depends on ovarian steroid levels and is a rich source of angiogenic growth factors, including VEGF-A. The VEGF-A gene is located on chromosome 6p21.3 and it is highly polymorphic with more than 20 different variants. This article critically reviews the published data concerning the relationships between some of the VEGF-A single nucleotide polymorphisms and the risk, pathogenesis and stage of endometriosis. Contrasting results have been published in the literature - probably due to the different ethnic background and the number of patients enrolled in clinical trials. However, the increasing interest in the use of antiangiogenic drugs (eg anti-VEGF-A drugs) in the therapy of endometriosis may suggest carrying out further genetic and pharmacogenetic studies of this disease because the stratification of patients at risk of endometriosis can lead to early diagnosis and optimal treatment choice.

Immunohistochemical Expression of DCUN1D1 in Non-small Cell Lung Carcinoma: Its Relation to Brain Metastasis

PURPOSE

Non-small cell lung carcinoma (NSCLC) comprises 75-85% of all lung cancers, and approximately 25% of all NSCLC patients develop brain metastasis. There are no reliable markers for predicting in which patients this metastasis will occur. DCUN1D1, also known as squamous cell carcinoma-related oncogene, is associated with tumor progression and poor outcomes in NSCLC. The objective of this study was to investigate the role of DCUN1D1 expression in cases of brain metastasis due to NSCLC.

MATERIALS AND METHODS

Primary tumor samples from a total of 71 cases of NSCLC, either with (n=40) or without (n=31) brain metastasis, were evaluated for DCUN1D1 expression by immunohistochemistry analysis.

RESULTS

DCUN1D1 expression was detected in 16 patients (23%) and tended to correlate with T classification (15% of T1-2 tumors vs. 30% of T3-4 tumors, p=0.083). DCUN1D1 expression was significantly associated with tumor stage. It was observed in none of the patients with stage I disease, 10% of those with stage II disease, and 29% with stage III disease (p=0.009). In addition, 14 of 16 DCUN1D1-positive patients resulted in brain metastasis (p=0.01). The odds ratio of brain metastasis for patients with DCUN1D1 expression was 3.112 (p=0.009).

CONCLUSION

DCUN1D1 expression may play a role in tumor progression and development of brain metastasis in patients with NSCLC. Evaluation of DCUN1D1 expression may provide assistance in identifying those patients who are at higher risk for brain metastasis.

SCCRO promotes glioma formation and malignant progression in mice

Originally identified as an oncogene activated by amplification in squamous cell carcinomas, several lines of evidence now suggest that squamous cell carcinoma-related oncogene (SCCRO; aka DCUN1D1) may play a role in the pathogenesis of a wide range of human cancers including gliomas. SCCRO's oncogenic function is substantiated by its ectopic expression, resulting in transformation of cells in culture and xenograft formation in nude mice. The aim of this study was to assess the in vivo oncogenicity of SCCRO in a murine model. Ubiquitous expression of SCCRO resulted in early embryonic lethality. Because SCCRO overexpression was detected in human gliomas, its in vivo oncogenic activity was assessed in an established murine glioma model. Conditional expression of SCCRO using a replication-competent ASLV long terminal repeat with splice acceptor/nestin-(tumor virus-A) tv-a model system was not sufficient to induce tumor formation in a wild-type genetic background, but tumors formed with increasing frequency and decreasing latency in facilitated background containing Ink4a deletion alone or in combination with PTEN loss. Ectopic expression of SCCRO in glial progenitor cells resulted in lower-grade gliomas in Ink4a(-/-) mice, whereas its expression in Ink4a(-/-)/PTEN(-/-) background produced high-grade glioblastoma-like lesions that were indistinguishable from human tumors. Expression of SCCRO with platelet-derived growth factor-beta (PDGF-beta) resulted in an increased proportion of mice forming glioblastoma-like tumors compared with those induced by PDGF-beta alone. This work substantiates SCCRO's function as an oncogene by showing its ability to facilitate malignant transformation and carcinogenic progression in vivo and supports a role for SCCRO in the pathogenesis of gliomas and other human cancers.

Pathophysiology of age-related diseases

A Symposium regarding the Pathophysiology of Successful and Unsuccessful Ageing was held in Palermo, Italy on 7-8 April 2009. Three lectures from that Symposium by G. Campisi, L. Ginaldi and F. Licastro are here summarized. Ageing is a complex process which negatively impacts on the development of various bodily systems and its ability to function. A long life in a healthy, vigorous, youthful body has always been one of humanity's greatest dreams. Thus, a better understanding of the pathophysiology of age-related diseases is urgently required to improve our understanding of maintaining good health in the elderly and to program possible therapeutic intervention.

3q26 Amplification and polysomy of chromosome 3 in squamous cell lesions of the lung: a fluorescence in situ hybridization study

PURPOSE

An overlapping area of gain at 3q26 has been reported in lung squamous cell carcinoma (SCC), but whether this also occurs in preneoplastic/preinvasive squamous cell proliferations and early-stage invasive carcinomas of the lung is still unknown.

EXPERIMENTAL DESIGN

We evaluated the prevalence and the clinicopathologic implications of 3q26 amplification and polysomy of chromosome 3 in 31 preneoplastic/preinvasive squamous cell lesions of the bronchial mucosa and in 139 early-stage invasive pulmonary SCC, both of limited growth within the bronchial wall [early hilar SCC (EHSCC)] and involving the pulmonary parenchyma [parenchyma-infiltrating SCC (PISCC)]. Moreover, mRNA expression of two candidate genes (h-TERC and SKI-like), both mapping to the minimal common amplification region, was also studied by quantitative real-time reverse transcription-PCR.

RESULTS

3q26 amplification and polysomy of chromosome 3 were confined to malignant samples, with 37% of invasive SCC, and 27% of severe dysplasias/in situ carcinomas showing these chromosomal abnormalities. Amplification (with minimal common amplification region at 3q26.2), polysomy 3, concurrent amplification and polysomy 3, or other changes (monosomy) were found in 25 SCC and 1 dysplasia, 24 and 2, 2 and 0, and 1 and 0, respectively. Amplification was significantly associated with EHSCC, polysomy 3 with PISCC. 3q26 amplification correlated with increased tumor diameter and a history of smoking, whereas polysomy 3 correlated with tumor diameter, pT class, and p53, p21, and fascin immunoreactivity. No relationship of either 3q26 gain or polysomy was found with patients' survival. Overexpression of h-TERC or SKI-like mRNA was found in 3q26-amplified or polysomic SCC, with higher levels of h-TERC in the former and of SKI-like in the latter.

CONCLUSIONS

3q26 amplification and chromosome 3 polysomy may be related to the development of invasive SCC, with differential distribution in tumor subsets, despite substantial histologic uniformity. Both h-TERC and SKI-like may be involved in tumor progression.

The ratio of membrane-bound form Flt-1 mRNA to VEGF mRNA correlates with tumor angiogenesis and prognosis in non-small cell lung cancer

Fms-like tyrosine kinase 1 (Flt-1), a receptor for vascular endothelial growth factor (VEGF), have two isoforms: membrane-bound form (mFlt-1) and soluble form. In the present study, we quantitatively evaluated expression level of mFlt-1 mRNA and VEGF mRNA in non-small cell lung cancer, and demonstrated the clinical significance of the ratio of mFlt-1 mRNA to VEGF mRNA (mFlt-1/VEGF). High mFlt-1/VEGF tumor showed a significantly lower microvessel density (P=0.004), and patients with high mFlt-1/VEGF tumor had a significantly favorable survival (P=0.037). Thus, the ratio of mFlt-1 mRNA to VEGF mRNA was inversely correlated with tumor angiogenesis, and was a significant prognostic factor.

Vascular endothelial growth factor pharmacogenetics: a new perspective for anti-angiogenic therapy

The pharmacogenetic approach to anti-angiogenic therapy should be considered a possible strategy for many pathological conditions with high incidence in Western countries, including solid tumors, age-related macular degeneration or endometriosis. While pharmacogenetic studies are building stronger foundations for the systematic investigations of phenotype–genotype relationships in many research and clinical fields of medicine, pharmacogenetic data regarding anti-angiogenic drugs are still lacking. Here we review preclinical and clinical genetic studies on angiogenic determinants such as vascular endothelial growth factor and vascular endothelial growth factor receptor-2. We suggest that pharmacogenetic profiling of patients who are candidates for the currently available anti-angiogenic agents targeting vascular endothelial growth factor and vascular endothelial growth factor receptor-2 may aid the selection of patients on the basis of their likelihood of responding to the drugs or suffering from toxicity.

Chromosomal aberrations in squamous cell carcinomas of the upper aerodigestive tract: biologic insights and clinical opportunities

Oncogenesis results from a progressive accumulation of genetic aberrations consequent to a complex interplay between carcinogenic factors and innate infidelity of DNA surveillance mechanisms. Although the development of genetic aberrations is random, those conferring survival advantages are selected for in a Darwinian manner, thus allowing continuous adaptation to selection pressures. Chromosomal aberrations are a prominent manifestation of genetic damage, which can be closely linked with tumor behavior and outcome as exemplified by curative treatment of chronic myelogenous leukemia resulting from targeting the BCR-ABL translocation. In the case of head and neck squamous cell carcinomas (HNSCC), chromosomal changes are detectable at all stages of tumor development, providing excellent opportunities for genomic prognostication and therapy. Several studies have shown that the overall genomic profile of HNSCC is highly consistent, but individual tumors vary significantly in their complement of genetic alterations, thereby confounding clinical correlation. The application of modern genetic and bioinformatic analytic approaches has facilitated the identification of critical genomic changes in HNSCC, many of which have been linked to clinical outcome. These genetic aberrations represent excellent targets for novel therapeutics, but require validation. The initiation of phase III trials evaluating the therapeutic utility of genetic aberrations suggests a promising future for genome-based treatment of HNSCC.

Apigenin Inhibits Expression of Vascular Endothelial Growth Factor and Angiogenesis in Human Lung Cancer Cells: Implication of Chemoprevention of Lung Cancer

Apigenin is a natural dietary flavonoid. It has recently been shown to have anticancer effects on prostate and ovarian cancer cells. However, the molecular basis of the effect of apigenin on cancer cells remains to be elucidated. In this study, we found that apigenin inhibited A549 lung cancer cell proliferation and vascular endothelial growth factor (VEGF) transcriptional activation in a dose-dependent manner. In an attempt to understand the mechanism of apigenin-inhibited VEGF expression, we found that apigenin inhibited VEGF transcriptional activation through the hypoxia-inducible factor 1 (HIF-1) binding site and specifically decreased HIF-1alpha but not HIF-1beta subunit expression in the cells. In our efforts to understand the signaling pathway that mediates VEGF transcriptional activation, we found that apigenin inhibited AKT and p70S6K1 activation. When testing the effect of apigenin in vivo, we found that apigenin significantly inhibited tumor growth in nude mice. Apigenin inhibited HIF-1alpha and VEGF expression in the tumor tissues, suggesting an inhibitory effect of apigenin on angiogenesis. To confirm this, we showed that apigenin inhibited angiogenesis in nude mice using the Matrigel assay. HIF-1alpha and VEGF are well known inducers of angiogenesis. Our data suggested that apigenin may inhibit human lung cancer angiogenesis by inhibiting HIF-1alpha and VEGF expression, thus providing a novel explanation for the anticancer action of apigenin.

Gene expression profiling allows distinction between primary and metastatic squamous cell carcinomas in the lung

Lung neoplasms commonly develop in patients previously treated for head and neck carcinomas. The derivation of these tumors, either as new primary lung cancers or as metastatic head and neck cancers, is difficult to establish based on clinical or histopathologic criteria since both are squamous cell carcinomas and have identical features under light microscopy. However, this distinction has significant treatment and prognostic implications. Gene expression profiling was performed on a panel of 52 sequentially collected patients with either primary lung (n = 21) or primary head and neck (n = 31) carcinomas using the Affymetrix HG_U95Av2 high-density oligonucleotide microarray. Unsupervised hierarchical clustering with Ward linkage and the Pearson correlation metric was performed. To assess robustness, bootstrap resampling was performed with 1,000 iterations. A t test of the normalized values for each gene was used to determine the genes responsible for segregating head and neck from lung primary carcinomas, and those with the most differential expression were used for later analyses. In the absence of a large "test" set of tumors, we used a supervised leave-one-out cross-validation to test how well we could predict the tumor origin. Once a gene expression profile was established, 12 lung lesions taken from patients with previously treated head and neck cancers were similarly analyzed by gene expression profiling to determine their sites of origin. Unsupervised clustering analysis separated the study cohort into two distinct groups which reliably remained segregated with bootstrap resampling. Group 1 consisted of 30 tongue carcinomas. Group 2 consisted of 21 lung cancers and 1 tongue carcinoma. The clustering was not changed even when normal lung or tongue profiles were subtracted from the corresponding carcinomatous lesions, and a leave-one-out cross-validation showed a 98% correct prediction (see Supplementary Data 1). A minimum set of 500 genes required to distinguish these groups was established. Given the ability to segregate these lesions using molecular profiling, we analyzed the lung tumors of undetermined origin. All cases clearly clustered with either lung or tongue tumor subsets, strongly supporting our hypothesis that this technique could elucidate the tissue of origin of metastatic lesions. Although histologically similar, squamous cell carcinomas have distinct gene expression profiles based on their anatomic sites of origin. Accordingly, the application of gene expression profiling may be useful in identifying the derivation of lung nodules and consequently enhances treatment planning.

Constitutive activation of GSK3 down-regulates glycogen synthase abundance and glycogen deposition in rat skeletal muscle cells

The effects of inhibition or constitutive activation of glycogen synthase kinase-3 (GSK3) on glycogen synthase (GS) activity, abundance, and glycogen deposition in L6 rat skeletal muscle cells were investigated. GS protein expression increased approximately 5-fold during differentiation of L6 cells (comparing cells at the end of day 5 with those at the beginning of day 3). However, exposure of undifferentiated myoblasts (day 3) to 50 microM SB-415286, a GSK3 inhibitor, led to a significant elevation in GS protein that was not accompanied by changes in the abundance of GLUT4, another late differentiation marker. In contrast, stable expression of a constitutively active form of GSK3beta (GSK3S9A) led to a significant reduction (approximately 80%) in GS protein that was antagonized by SB-415286. Inhibition of GSK3 or expression of the constitutively active GSK3S9A did not result in any detectable changes in GS mRNA abundance. However, the increase in GS protein in undifferentiated myoblasts or that seen following incubation of cells expressing GSK3S9A with GSK3 inhibitors was blocked by cycloheximide suggesting that GSK3 influences GS abundance possibly via control of mRNA translation. Consistent with the reduction in GS protein, cells expressing GSK3S9A were severely glycogen depleted as judged using a specific glycogen-staining antibody. Inhibiting GSK3 in wild-type or GSK3S9A-expressing cells using SB-415286 resulted in an attendant activation of GS, but not that of glucose transport. However, GS activation alone was insufficient for stimulating glycogen deposition. Only when muscle cells were incubated simultaneously with insulin and SB-415286 or with lithium (which stimulates GS and glucose transport) was an increase in glycogen accretion observed. Our findings suggest that GSK3 activity is an important determinant of GS protein expression and that while glycogen deposition in muscle cells is inherently dependent upon the activity/expression of GS, glucose transport is a key rate-determining step in this process.