Nuclear and membrane expression of the angiogenesis regulator delta-like ligand 4 (DLL4) in normal and malignant human tissues

Endothelial Dll4 overexpression reduces vascular response and inhibits tumor growth and metastasization in vivo

BACKGROUND

The inhibition of Delta-like 4 (Dll4)/Notch signaling has been shown to result in excessive, nonfunctional vessel proliferation and significant tumor growth suppression. However, safety concerns emerged with the identification of side effects resulting from chronic Dll4/Notch blockade. Alternatively, we explored the endothelial Dll4 overexpression using different mouse tumor models.

METHODS

We used a transgenic mouse model of endothelial-specific Dll4 overexpression, previously produced. Growth kinetics and vascular histopathology of several types of solid tumors was evaluated, namely Lewis Lung Carcinoma xenografts, chemically-induced skin papillomas and RIP1-Tag2 insulinomas.

RESULTS

We found that increased Dll4/Notch signaling reduces tumor growth by reducing vascular endothelial growth factor (VEGF)-induced endothelial proliferation, tumor vessel density and overall tumor blood supply. In addition, Dll4 overexpression consistently improved tumor vascular maturation and functionality, as indicated by increased vessel calibers, enhanced mural cell recruitment and increased network perfusion. Importantly, the tumor vessel normalization is not more effective than restricted vessel proliferation, but was found to prevent metastasis formation and allow for increased delivery to the tumor of concomitant chemotherapy, improving its efficacy.

CONCLUSIONS

By reducing endothelial sensitivity to VEGF, these results imply that Dll4/Notch stimulation in tumor microenvironment could be beneficial to solid cancer patient treatment by reducing primary tumor size, improving tumor drug delivery and reducing metastization. Endothelial specific Dll4 overexpression thus appears as a promising anti-angiogenic modality that might improve cancer control.

Myeloid DLL4 Does Not Contribute to the Pathogenesis of Non-Alcoholic Steatohepatitis in Ldlr-/- Mice

Non-alcoholic steatohepatitis (NASH) is characterized by liver steatosis and inflammation. Currently, the underlying mechanisms leading to hepatic inflammation are not fully understood and consequently, therapeutic options are poor. Non-alcoholic steatohepatitis (NASH) and atherosclerosis share the same etiology whereby macrophages play a key role in disease progression. Macrophage function can be modulated via activation of receptor-ligand binding of Notch signaling. Relevantly, global inhibition of Notch ligand Delta-Like Ligand-4 (DLL4) attenuates atherosclerosis by altering the macrophage-mediated inflammatory response. However, the specific contribution of macrophage DLL4 to hepatic inflammation is currently unknown. We hypothesized that myeloid DLL4 deficiency in low-density lipoprotein receptor knock-out (Ldlr^-/-) mice reduces hepatic inflammation. Irradiated Ldlr^-/- mice were transplanted (tp) with bone marrow from wild type (Wt) or DLL4^f/fLysMCre^+/0 (DLL4^del) mice and fed either chow or high fat, high cholesterol (HFC) diet for 11 weeks. Additionally, gene expression was assessed in bone marrow-derived macrophages (BMDM) of DLL4^f/fLysMCre^WT and DLL4^f/fLysMCre^+/0 mice. In contrast to our hypothesis, inflammation was not decreased in HFC-fed DLL4^del-transplanted mice. In line, in vitro, there was no difference in the expression of inflammatory genes between DLL4-deficient and wildtype bone marrow-derived macrophages. These results suggest that myeloid DLL4 deficiency does not contribute to hepatic inflammation in vivo. Since, macrophage-DLL4 expression in our model was not completely suppressed, it can’t be totally excluded that complete DLL4 deletion in macrophages might lead to different results. Nevertheless, the contribution of non-myeloid Kupffer cells to notch signaling with regard to the pathogenesis of steatohepatitis is unknown and as such it is possible that, DLL4 on Kupffer cells promote the pathogenesis of steatohepatitis.

The Notch ligand DLL4 specifically marks human hematoendothelial progenitors and regulates their hematopoietic fate

Notch signaling is essential for definitive hematopoiesis, but its role in human embryonic hematopoiesis is largely unknown. We show that in hESCs the expression of the Notch ligand DLL4 is induced during hematopoietic differentiation. We found that DLL4 is only expressed in a sub-population of bipotent hematoendothelial progenitors (HEPs) and segregates their hematopoietic versus endothelial potential. We demonstrate at the clonal level and through transcriptome analyses that DLL4(high) HEPs are enriched in endothelial potential, whereas DLL4(low/-) HEPs are committed to the hematopoietic lineage, albeit both populations still contain bipotent cells. Moreover, DLL4 stimulation enhances hematopoietic differentiation of HEPs and increases the amount of clonogenic hematopoietic progenitors. Confocal microscopy analysis of whole differentiating embryoid bodies revealed that DLL4(high) HEPs are located close to DLL4(low/-) HEPs, and at the base of clusters of CD45+ cells, resembling intra-aortic hematopoietic clusters found in mouse embryos. We propose a model for human embryonic hematopoiesis in which DLL4(low/-) cells within hemogenic endothelium receive Notch-activating signals from DLL4(high) cells, resulting in an endothelial-to-hematopoietic transition and their differentiation into CD45+ hematopoietic cells.

The role of notch in the cardiovascular system: potential adverse effects of investigational notch inhibitors

Targeting the Notch pathway is a new promising therapeutic approach for cancer patients. Inhibition of Notch is effective in the oncology setting because it causes a reduction of highly proliferative tumor cells and it inhibits survival of cancer stem cells, which are considered responsible for tumor recurrence and metastasis. Additionally, since Delta-like ligand 4 (Dll4)-activated Notch signaling is a major modulator of angiogenesis, anti-Dll4 agents are being investigated to reduce vascularization of the tumor. Notch plays a major role in the heart during the development and, after birth, in response to cardiac damage. Therefore, agents used to inhibit Notch in the tumors (gamma secretase inhibitors and anti-Dll4 agents) could potentially affect myocardial repair. The past experience with trastuzumab and other tyrosine kinase inhibitors used for cancer therapy demonstrates that the possible cardiotoxicity of agents targeting shared pathways between cancer and heart and the vasculature should be considered. To date, Notch inhibition in cancer patients has resulted only in mild gastrointestinal toxicity. Little is known about the potential long-term cardiotoxicity associated to Notch inhibition in cancer patients. In this review, we will focus on mechanisms through which inhibition of Notch signaling could lead to cardiomyocytes and endothelial dysfunctions. These adverse effects could contrast with the benefits of therapeutic responses in cancer cells during times of increased cardiac stress and/or in the presence of cardiovascular risk factor.

Distinguishing Cancerous Liver Cells Using Surface-Enhanced Raman Spectroscopy

Raman spectroscopy has been widely used in biomedical research and clinical diagnostics. It possesses great potential for the analysis of biochemical processes in cell studies. In this article, the surface-enhanced Raman spectroscopy (SERS) of normal and cancerous liver cells incubated with SERS active substrates (gold nanoparticle) was measured using confocal Raman microspectroscopy technology. The chemical components of the cells were analyzed through statistical methods for the SERS spectrum. Both the relative intensity ratio and principal component analysis (PCA) were used for distinguishing the normal liver cells (QSG-7701) from the hepatoma cells (SMMC-7721). The relative intensity ratio of the Raman spectra peaks such as I937/I1209, I1276/I1308, I1342/I1375, and I1402/I1435 was set as the judge boundary, and the sensitivity and the specificity using PCA method were calculated. The results indicated that the surface-enhanced Raman spectrum could provide the chemical information for distinguishing the normal cells from the cancerous liver cells and demonstrated that SERS technology possessed the possible applied potential for the diagnosis of liver cancer.

A phase I dose escalation and expansion study of the anticancer stem cell agent demcizumab (anti-DLL4) in patients with previously treated solid tumors

PURPOSE

This phase I trial evaluated the safety, pharmacokinetics, and pharmacodynamics of demcizumab (OMP-21M18), a humanized IgG2 mAb targeting the Notch ligand DLL4 in adult patients with advanced malignancies.

EXPERIMENTAL DESIGN

Standard 3+3 design, with demcizumab 0.5, 1, 2.5, or 5 mg/kg weekly or 2.5, 5, or 10 mg/kg every other week, with an expansion cohort at 10 mg/kg every other week. Dose-limiting toxicities (DLT) were assessed during the first 28 days.

RESULTS

Fifty-five patients received demcizumab (15 weekly, 18 every other week, 21 expansion cohort, 1 loading dose). No more than one DLT was seen at any dose level. The MTD was not reached for either schedule. Treatment-related adverse events occurring in >10% of patients were hypertension or blood pressure increased (47%), fatigue (31%), anemia (22%), headache (20%), nausea (13%), hypoalbuminemia (11%), dizziness (11%), and dyspnea (11%). One patient dosed at 2.5 mg/kg developed reversible right-sided heart failure after 63 days on treatment and 4 dosed at 10 mg/kg developed congestive heart failure after ≥98 days on treatment. Five patients were hospitalized with bleeding episodes (2 episodes of tumor-associated bleeding). Sixteen of 25 (64%) evaluable patients at 10 mg/kg had evidence of stabilization of disease or response.

CONCLUSION

Demcizumab was generally well tolerated at doses ≤5 mg weekly with disease stabilization and decreases in tumor size demonstrating antitumor activity. Hypertension was the most common adverse event that was clearly related to treatment. Prolonged administration was associated with an increased risk of congestive heart failure.

Identification of putative ortholog gene blocks involved in gestant and lactating mammary gland development: a rodent cross-species microarray transcriptomics approach

The mammary gland (MG) undergoes functional and metabolic changes during the transition from pregnancy to lactation, possibly by regulation of conserved genes. The objective was to elucidate orthologous genes, chromosome clusters and putative conserved transcriptional modules during MG development. We analyzed expression of 22,000 transcripts using murine microarrays and RNA samples of MG from virgin, pregnant, and lactating rats by cross-species hybridization. We identified 521 transcripts differentially expressed; upregulated in early (78%) and midpregnancy (89%) and early lactation (64%), but downregulated in mid-lactation (61%). Putative orthologous genes were identified. We mapped the altered genes to orthologous chromosomal locations in human and mouse. Eighteen sets of conserved genes associated with key cellular functions were revealed and conserved transcription factor binding site search entailed possible coregulation among all eight block sets of genes. This study demonstrates that the use of heterologous array hybridization for screening of orthologous gene expression from rat revealed sets of conserved genes arranged in chromosomal order implicated in signaling pathways and functional ontology. Results demonstrate the utilization power of comparative genomics and prove the feasibility of using rodent microarrays to identification of putative coexpressed orthologous genes involved in the control of human mammary gland development.

Elevated DLL4 expression is correlated with VEGF and predicts poor prognosis of nasopharyngeal carcinoma

Delta-like ligand 4 (DLL4), one of the transmembranous Notch ligands, is upregulated at the site of tumor growth, particularly during tumor angiogenesis. Expression pattern of DLL4 in nasopharyngeal carcinoma (NPC) and the clinical and prognostic significance remain unclear. In this study, immunohistochemical analysis (IHC) was used to examine the protein level of DLL4 in NPC tissues from two independent cohorts. In the testing cohort (311 cases), we applied the X-tile program software able to assess the optimal cutoff points for biomarkers in order to accurately classify patients according to clinical outcome. In the validation cohort (113 cases), the cutoff score derived from X-title analysis was investigated to determine the association of DLL4 expression with disease-specific survival (DFS). Our results showed that high expression of DLL4 was observed in 134 of 313 (42.8 %) in the testing cohort and 58 of 113 (43.6 %) in the validation cohort. High expression of DLL4 independently predicted poorer disease-specific survival, as evidenced by univariate and multivariate analysis (P < 0.05). Moreover, DLL4 expression was significantly elevated in distant NPC metastases relative to primary NPC tumors (P = 0.001). Importantly, we found a significant positive relationship between DLL4 and vascular endothelial growth factor (VEGF) (P < 0.001). Patients with dual elevated DLL4 and VEGF expression displayed a significant overall survival disadvantage compared to those with dual low expression (P < 0.05). These findings provide evidence that high expression of DLL4 serves as an independent predictor of poor prognosis in NPC patients.

Delta like ligand 4 induces impaired chemo-drug delivery and enhanced chemoresistance in pancreatic cancer

The stubborn chemoresistance of pancreatic ductal adenocarcinoma (PDA) is simultaneously influenced by tumor parenchymal and stromal factors, and the ctritical role of Notch ligand Delta-like 4 (DLL4) in the regulation of tumor malignancies has been observed. DLL4 positive expression ratio between duct cells from clinical tumor and adjacent tissues was statistically significant, and the overactivation of DLL4/Notch pathway enhanced the phenotype of EMT and cancer stem cell, even can induce multi-chemoresistance in vitro. Notably, the accompanied defective angiogenesis directly induced inefficient chemo-drug delivery in vivo. Collectively, overexpressed DLL4 on neoplastic cells can enhance chemoresistance through angiogenesis-dependent/independent mechanisms in PDA.

Influence of vascular endothelial growth factor single nucleotide polymorphisms on non-small cell lung cancer tumor angiogenesis

Vascular endothelial growth factor (VEGF) plays an important role in tumor angiogenesis. Several studies have reported that genomic VEGF polymorphisms may influence VEGF synthesis. To evaluate the role of VEGF single nucleotide polymorphisms (SNPs), we examined the expression of several angiogenesis-related proteins [VEGF, hypoxia-inducible factor-1α (HIF-1α) and delta-like ligand 4 (Dll4)] and the spread of microvessels in resected non-small cell lung cancer (NSCLC). Blood and tumor tissue from 83 patients with NSCLC were examined for VEGF −460T/C (rs833061) and VEGF +405G/C (rs2010963) SNPs using the SNaPshot method. Immunohistochemical staining was performed to measure protein expression and microvessel density (MVD). VEGF −460T/C and +405G/C SNPs showed no association with VEGF or HIF-1α expression and MVD. Patients with VEGF −460TT and the TC genotype had significantly higher MVD compared to those with the CC genotypes. Furthermore, patients with the VEGF −460TT genotype had significantly higher Dll4 expression compared to those with the TC or CC genotypes, while the VEGF +405G/C SNP displayed no association with Dll4 expression and MVD. These findings indicate that the VEGF −460T/C SNP may have a functional influence on tumor angiogenesis in NSCLC. We hypothesize that VEGF SNPs may influence angiogenesis through Dll4.

Clinicopathological significance of altered Notch signaling in extrahepatic cholangiocarcinoma and gallbladder carcinoma

AIM: To investigate the role and clinicopathological significance of aberrant expression of Notch receptors and Delta-like ligand-4 (DLL4) in extrahepatic cholangiocarcinoma and gallbladder carcinoma.

METHODS: One hundred and ten patients had surgically resected extrahepatic cholangiocarcinoma (CC) and gallbladder carcinoma specimens examined by immunohistochemistry of available paraffin blocks. Immunohistochemistry was performed using anti-Notch receptors 1-4 and anti-DLL4 antibodies. We scored the immunopositivity of Notch receptors and DLL4 expression by percentage of positive tumor cells with cytoplasmic expression and intensity of immunostaining. Coexistent nuclear localization was evaluated. Clinicopathological parameters and survival data were compared with the expression of Notch receptors 1-4 and DLL4.

RESULTS: Notch receptor proteins showed in the cytoplasm with or without nuclear expression in cancer cells, as well as showing weak cytoplasmic expression in non-neoplastic cells. By semiquantitative evaluation, positive immunostaining of Notch receptor 1 was detected in 96 cases (87.3%), Notch receptor 2 in 97 (88.2%), Notch receptor 3 in 97 (88.2%), Notch receptor 4 in 103 (93.6), and DLL4 in 84 (76.4%). In addition, coexistent nuclear localization was noted [Notch receptor 1; 18 cases (18.8%), Notch receptor 2; 40 (41.2%), Notch receptor 3; 32 (33.0%), Notch receptor 4; 99 (96.1%), DLL4; 48 (57.1%)]. Notch receptor 1 expression was correlated with advanced tumor, node, metastasis (TNM) stage (P = 0.043), Notch receptor 3 with advanced T stage (P = 0.017), tendency to express in cases with nodal metastasis (P = 0.065) and advanced TNM stage (P = 0.052). DLL4 expression tended to be related to less histological differentiation (P = 0.095). Coexistent nuclear localization of Notch receptor 3 was related to no nodal metastasis (P = 0.027) and Notch receptor 4 with less histological differentiation (P = 0.036), while DLL4 tended to be related inversely with T stage (P = 0.053). Coexistent nuclear localization of DLL4 was related to poor survival (P = 0.002).

CONCLUSION: Aberrant expression of Notch receptors 1 and 3 play a role during cancer progression, and cytoplasmic nuclear coexistence of DLL4 expression correlates with poor survival in extrahepatic CC and gallbladder carcinoma.

Anti-DLL4, a cancer therapeutic with multiple mechanisms of action

DLL4 is a ligand for the Notch family of receptors. DLL4 has many important functions in normal development and tissue homeostasis, including roles in the immune system, the gastro-intestinal tract, and in vascular development. Because of the importance of Notch signaling in stem cell biology, DLL4 has been investigated for its role in the maintenance and proliferation of cancer stem cells (CSC). In addition, its important role in angiogenesis has been investigated for utility as an anti-angiogenic agent. Preclinical studies have highlighted that both anti-CSC and anti-angiogenic activities contribute to its anti-tumor efficacy, and have supported the clinical development of anti-DLL4 antibody for the treatment of cancer.

Prognostic impact of Notch ligands and receptors in nonsmall cell lung cancer: coexpression of Notch-1 and vascular endothelial growth factor-A predicts poor survival

BACKGROUND

Notch signaling plays a key role in embryonic vascular development and angiogenesis. The authors aimed to study the prognostic role of the angiogenesis-related Notch ligands and receptors and investigate the prognostic impact of the coexpression of vascular endothelial growth factor-A (VEGF-A) and Notch signaling.

METHODS

Tumor tissue samples from 335 resected patients with stage I to IIIA nonsmall cell lung cancer (NSCLC) were obtained, and tissue microarrays were constructed from duplicate cores of tumor cells and tumor-related stroma from each specimen. Immunohistochemistry was used to evaluate the expression of the molecular markers Notch-1, Notch-4, Delta-like ligand 4 (DLL4), and Jagged-1.

RESULTS

There were 191 squamous cell carcinomas (SCCs), 113 adenocarcinomas (ACs), and 31 large cell carcinomas. In AC, low tumor cell Delta-like ligand 4 expression was an independent negative prognostic factor (hazard ratio [HR], 2.9; 95% confidence interval [CI], 1.4-6.3 [P = .006]), whereas high tumor cell Notch-1 expression was an independent negative prognostic factor (HR, 2.2; 95% CI, 1.2-4.1 [P<.001]). In SCC, low stromal Delta-like ligand 4 expression was an independent indicator of poor prognosis (HR, 3.3; 95% CI, 1.8-6.1 [P<.001]). The coexpression of Notch-1 and VEGF-A had a significant prognostic impact (P<.001). For Notch-1 and VEGF-A, low/low (n = 142) versus high/high (n = 35) expression resulted in 5-year survival rates of 69% and 32%, respectively.

CONCLUSIONS

Delta-like ligand 4 and Notch-1 are independent prognostic factors in NSCLC, but have diverse impacts in SCC and AC. The coexpression of tumor cell Notch-1/VEGF-A has a major impact on survival.