Tumour growth requires accompanying expansion of the host vasculature, with tumour progression often correlated with vascular density. Vascular endothelial growth factor (VEGF) is the best-characterized inducer of tumour angiogenesis. We report that VEGF dynamically regulates tumour endothelial expression of Delta-like ligand 4 (Dll4), which was previously shown to be absolutely required for normal embryonic vascular development. To define Dll4 function in tumour angiogenesis, we manipulated this pathway in murine tumour models using several approaches. Here we show that blockade resulted in markedly increased tumour vascularity, associated with enhanced angiogenic sprouting and branching. Paradoxically, this increased vascularity was non-productive-as shown by poor perfusion and increased hypoxia, and most importantly, by decreased tumour growth-even for tumours resistant to anti-VEGF therapy. Thus, VEGF-induced Dll4 acts as a negative regulator of tumour angiogenesis; its blockade results in a striking uncoupling of tumour growth from vessel density, presenting a novel therapeutic approach even for tumours resistant to anti-VEGF therapies.

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Anti-angiogenesis therapies have emerged as important treatment options for several types of tumours. To date, these therapies have focused on blocking the vascular endothelial growth factor (VEGF) pathway. A recent series of papers have shown that one ligand for the Notch receptors, Delta-like ligand 4 (DLL4), is normally induced by VEGF and is a negative-feedback regulator that restrains vascular sprouting and branching. Consistent with this role, the deletion or inhibition of DLL4 results in excessive, non-productive angiogenesis. This unrestrained angiogenesis unexpectedly and paradoxically decreases tumour growth, even in tumours resistant to anti-VEGF therapies. Can too much angiogenesis be bad for tumours but good for patients?

Development of the vascular system depends on the highly coordinated actions of a variety of angiogenic regulators. Several of these regulators are members of the tyrosine kinase superfamily, including VEGF receptors and angiopoietin receptors, Tie1 and Tie2. Tyrosine kinase signaling is counter-regulated by the activity of tyrosine phosphatases, including vascular endothelial protein tyrosine phosphatase (VE-PTP), which has previously been shown to modulate Tie2 activity. We generated mice in which VE-PTP is replaced with a reporter gene. We confirm that VE-PTP is expressed in endothelium and also show that VE-PTP is highly expressed in the developing outflow tract of the heart and later is expressed in developing heart valves. Vasculogenesis occurs normally in mice lacking VE-PTP; however, angiogenesis is abnormal. Angiogenic defects in VE-PTP-null mice were most pronounced in the yolk sac and include a complete failure to elaborate the primitive vascular scaffold into higher-order branched arteries, veins, and capillaries. VE-PTP continues to be expressed into adulthood in the vasculature and heart valves, suggesting later roles in vascular development or homeostasis. VE-PTP is also expressed in the vasculature of growing tumors, suggesting that VE-PTP may be a new potential target for angiogenic therapies.gene targeting ͉ tyrosine kinase ͉ Tie2

Background: Delta-like ligand 4 (Dll4) is a Notch ligand that is upregulated by hypoxia and vascular endothelial growth factor-A (VEGF-A) and is reported to have a role in tumor angiogenesis. Evidence from xenograft studies suggests that inhibiting Dll4–Notch signalling may overcome resistance to anti-VEGF therapy. The aim of this study was to characterise the expression of Dll4 in colon cancer and to assess whether it is associated with markers of hypoxia and prognosis. Method: In all, 177 colon cancers were represented in tissue microarrays. Immunohistochemistry was performed using validated antibodies against Dll4, VEGF, hypoxia-inducible factor (HIF)-1 α , HIF-2 α , prolyl hydroxylase (PHD)1, PHD2, PHD3 and carbonic anhydrase 9 (CA9). Results: The expression of Dll4 was observed preferentially in the endothelium of 71% (125 out of 175) of colon cancers, but not in the endothelium adjacent to normal mucosa (none out of 107, P <0.0001). The expression of VEGF was significantly associated with HIF-2 α ( P <0.0001) and Dll4 ( P =0.010). Only HIF-2 α had a significant multivariate prognostic effect (hazard ratio 1.61, 95% confidence interval 1.01–2.57). Delta-like ligand 4 was also expressed by neoplastic cells, particularly neoplastic goblet cells. Conclusion: Endothelial expression of Dll4 is not a prognostic factor, but is significantly associated with VEGF. Assessing endothelial Dll4 expression may be critical in predicting response to anti-VEGF therapies.

Delta-like ligand 4 (Dll4) is a Notch ligand that is predominantly expressed in the endothelium. Evidence from xenografts suggests that inhibiting Dll4 may overcome resistance to antivascular endothelial growth factor therapy. The aims of this study were to characterize the expression of Dll4 in breast cancer and assess whether it is associated with inflammatory markers and prognosis. We examined 296 breast adenocarcinomas and 38 ductal carcinoma in situ tissues that were represented in tissue microarrays. Additional whole sections representing 10 breast adenocarcinomas, 10 normal breast tissues, and 16 angiosarcomas were included. Immunohistochemistry was then performed by using validated antibodies against Dll4, CD68, CD14, Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN), CD123, neutrophil elastase, CD31, and carbonic anhydrase 9. Dll4 was selectively expressed by intratumoral endothelial cells in 73% to 100% of breast adenocarcinomas, 18% of in situ ductal carcinomas, and all lactating breast cases, but not normal nonlactating breast. High intensity of endothelial Dll4 expression was a statistically significant adverse prognostic factor in univariate (P ‫؍‬ 0.002 and P ‫؍‬ 0.01) and multivariate analyses (P ‫؍‬ 0.03 and P ‫؍‬ 0.04) of overall survival and relapse-free survival, respectively. Among the inflammatory markers, only CD68 and DC-SIGN were significant prognostic factors in univariate (but not multivariate) analyses of overall survival (P ‫؍‬ 0.01 and 0.002, respectively). In summary, Dll4 was expressed by endothelium associated with breast cancer cells. In these retrospective subset analyses, endothelial Dll4 expression was a statistically significant multivariate prognostic factor. (Am J Pathol

The Notch ligand delta-like 4 (Dll4)

8038 Background: Multiple myeloma (MM) predominantly affects older patients (pts) (median age at diagnosis 69 yrs) in whom comorbidities must be considered to manage the disease appropriately. Some anti-MM therapies can be associated with ocular toxicities and require careful attention when used among pts with pre-existing ocular comorbidities (OC). In 2018, 41% of Medicare enrollees had OC. Despite the potential implication on treatment decisions, information on pre-existing OC (e.g., disorders of lens, glaucoma) in MM pts is limited. This study aims to describe the prevalence of OCs among real-world pts with MM in 2011-2020 in the US. Methods: Adults with newly diagnosed MM (NDMM) with or without treatment, with 1L systemic therapy, and with relapsed/refractory MM (RRMM) who received up to 4 lines of systemic therapies (LOT) for MM were identified in the IQVIA PharMetrics Plus data. The index date was the date of initial MM diagnosis or a LOT initiation date. The prevalence of OC in each group was defined as the presence of any OC ICD 9/10 diagnosis codes in the 12 months prior to the index date. OCs (e.g., disorders of conjunctiva, lens, choroid, retina, glaucoma) were considered a potentially MM-related disease manifestation or MM treatment-related toxicity based on published literature and clinical expert opinion. Results: The median age at initial MM diagnosis was 64 yrs overall (N=49,814), and 63 yrs among treated pts (N=22,963). The median age was 63 yrs at 1L initiation and 64 yrs at 2L, 3L, and 4L initiation. The prevalence of OC at initial MM diagnosis was 39.0% overall and 35.2% among treated pts (Table). The OC prevalence was 35.8% prior to 1L initiation and higher in RRMM pts (42.1%, 44.9%, and 45.7% prior to 2L, 3L, and 4L initiation, respectively). This trend was observed across all OC categories, among MM-related OCs, and across all age groups. The prevalence of OC by MM stage was stable over the years. Conclusions: Approximately 40% of NDMM pts have a pre-existing OC, and the prevalence increases with the number of LOT in RRMM. While some OC may be due to aging, the impact of OC on treatment decisions for MM should be explored. [Table: see text]