Vascular Endothelial Growth Factor (VEGF) Signaling in Tumour Vascularization: Potential and Challenges

Angiogenesis is defined as the physiological process by which new blood vessels develop from pre-existing vessels; either by sprouting or intussusception. Inhibition of angiogenesis is one of the most encouraging strategies to manage the growth and metastasis of cancers. The functional and proliferative status of blood vessels is regulated by the balance between various key molecules that either stimulate or inhibit angiogenesis. During quiescence, the "angiogenic switch" is "off". However, during tumour development pro-angiogenic factors such as vascular endothelial growth factor (VEGF), basic and acidic fibroblast growth factor, tumour necrosis factor-α and interleukin-1 are pathologically enhanced. Persistent growth of tumour directed capillary networks creates a favourable microenvironment, promoting cancer growth, progression and metastasis. VEGF, particularly VEGF-A, is a key angiogenic factor. Targeting VEGF, its receptors and the downstream signaling cascade, is a viable strategy to prevent tumour growth and metastasis. The present review discusses the role of VEGF in tumour angiogenesis and the current understanding of anti-VEGF therapies as well as refractoriness of anti-angiogenesis cancer therapy.

Simvastatin Alleviates Pathology in a Rat Model of Preeclampsia Involving ERK/MAPK Pathway

Preeclampsia (PE) is a pregnancy-specific condition characterized by new-onset hypertension. There is evidence suggesting that imbalances of angiogenic factors, oxidative stress, and inflammation may be central to the pathogenesis of PE. We sought to investigate whether simvastatin would reduce mean arterial pressure, restore the angiogenic balance, and ameliorate inflammation and oxidative stress in a nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME)-induced rat model of PE. We found that blood pressure was significantly increased in the l-NAME group compared to normal pregnant dams ( P < .01), and simvastatin reduced this difference. In addition, dams from the l-NAME group showed lower vascular endothelial growth factor (VEGF) and interleukin (IL) 10 levels and higher plasma-soluble FMS-like tyrosine kinase 1 (sFlt-1), tumor necrosis factor α (TNF-α), and oxidative stress marker malondialdehyde (MDA) levels as compared to control dams ( P < .01, for all). Interestingly, simvastatin treatment significantly increased VEGF and IL-10 levels while decreased sFlt-1, TNF-α, and MDA levels compared to the untreated l-NAME group. Moreover, simvastatin treatment significantly upregulated protein expression of placental p-extracellular signal-regulated kinase (ERK1), p-p38 mitogen-activated protein kinase (MAPK), p-c-Jun N-terminal kinase, and p-protein kinase B compared to untreated l-NAME control. These results suggest that simvastatin treatment restores angiogenic balance and ameliorates inflammation and oxidative stress in a rat model of PE involving ERK/MAPK pathway.

Maternal circulating angiogenic factors in twin and singleton pregnancies

OBJECTIVE

The purpose of this study was to compare longitudinally sampled maternal angiogenic proteins between singleton and twin pregnancies.

STUDY DESIGN

Placental growth factor (PlGF), soluble feline McDonough sarcoma (fms)-like tyrosine kinase (sFlt)-1, and soluble endoglin from healthy pregnant women were quantified at 10, 18, 26, and 35 weeks' gestation (n=91), and during the third trimester (31-39 weeks) and at delivery (33-41 weeks; n=41). Geometric means and 95% confidence intervals were calculated for gestational age-adjusted angiogenic protein concentrations and compared between matched twin and singleton pregnancies.

RESULTS

Maternal sFlt-1 concentrations and the sFlt-1/PlGF ratio were higher in twins than singletons across pregnancy and at delivery, with the greatest differences at week 35 (sFlt-1: 36,916 vs 10,151 pg/mL; P<.0001; sFlt-1/PlGF: 168.4 vs 29.0; P<.0001). Maternal concentrations of soluble endoglin also were higher in the third trimester and delivery. Maternal PlGF concentrations were lower in twin than singleton pregnancies at week 35 only (219.2 vs 350.2 pg/mL; P<.0001). Placental weight appeared to be inversely correlated with maternal sFlt-1/PlGF ratio at the end of pregnancy in both twins and singletons.

CONCLUSION

Higher maternal antiangiogenic proteins in twin than singleton pregnancies does not appear to be due to greater placental mass in the former, and may be one explanation for the increased risk of preeclampsia in women carrying multiple gestations. Determining whether women with a history of multiple gestations have an altered cardiovascular disease and breast cancer risk, like those with a history of preeclampsia, is warranted.

Preeclampsia - Aetiology, Current Diagnostics and Clinical Management, New Therapy Options and Future Perspectives

Preeclampsia is a multisystem disease for which the exact causes have not yet been sufficiently clarified. However, in the past few years it has become clear that a placental imbalance between angiogenic and anti-angiogenic proteins is the decisive pathogenetic factor for the occurrence of preeclampsia. With the possibility to measure these angiogenic factors (sFlt-1/PlGF ratio) in maternal blood full new diagnostic possibilities have been opened that enable the certain diagnosis or exclusion of the diseases as well as a short-term prognosis to be made. In secondary prevention the current data situation for ASA confirms a moderate but measurable utility. The management concept depends on gestational age. In the case of early clinical manifestations (< 34th week of pregnancy) the clinical management in a perinatal centre remains unchanged with foeto-maternal monitoring and induction of pulmonary maturation, symptomatic therapy under careful blood pressure lowering and determination of the optimal delivery time. A balance must be made here between foetal immaturity and maternal risks upon prolongations. The pathomechanism of anti-angiogenic overload with sFlt-1 provides a starting point for first therapeutic interventions. The present article gives an overview of current diagnostic options and presents possible future therapeutic perspectives for discussion.