Anti-VEGF : une avancée thérapeutique dans la maladie de Rendu-Osler

An in vitro study on the effect of bevacizumab on endothelial cell proliferation and VEGF concentration level in patients with hereditary hemorrhagic telangiectasia

Previous studies have demonstrated that vascular endothelial growth factor (VEGF) is upregulated in patients with hereditary hemorrhagic telangiectasia (HHT). The use of Bevacizumab as an anti-angiogenic treatment agent seems promising. The purpose of the present in vitro study was to determine the efficacy and potential toxicity levels of bevacizumab on cell proliferation and VEGF concentrations in endothelial cells of HHT patients. In this in vitro study, endothelial cells from patients with HHT and HUVECs (control) were incubated with different concentration levels of bevacizumab (2, 4, 6, 8 or 10 mg/ml). After 24, 48 or 72 h, the cell proliferation was assessed by Alamar Blue^® Assay and the VEGF levels in the cell culture supernatants were measured by VEGF-ELISA. All endothelial cells incubated with bevacizumab showed an initial decrease in cell proliferation. Cell proliferation recovered within 72 h in cell cultures incubated with concentration levels of up to 4 mg/ml bevacizumab, whereas those incubated with higher concentration levels showed a continuous decline in cell proliferation. VEGF expression decreased after 24 h in cell cultures incubated with bevacizumab concentration levels of 2 and 4 mg/ml but increased again after 48 h. Cell cultures incubated with bevacizumab concentration levels of 10 mg/ml showed a constant decline in VEGF expression without any tendency for recovery. Translating these results into daily clinical practice, the present study suggests that the intranasal submucosal injection of bevacizumab in HHT patients should not exceed a concentration level of 4 mg/ml. Overall, higher bevacizumab concentration levels not only reduce VEGF expression but pose a higher risk of toxic effects on endothelial cells as they jeopardize cell proliferation.

[Bevacizumab: a new success in hereditary hemorrhagic telangiectasia]

INTRODUCTION

Hereditary hemorrhagic telangiectasia (HHT), is a rare, hereditary vascular dysplasia, characterized by recurrent epistaxis, mucocutaneous telangiectasias and visceral arteriovenous malformations. The vascular endothelial growth factor VEGF seems to play a crucial role in the pathogenesis of this disease. Recently bevacizumab, a humanized monoclonal VEGF inhibitor, has shown promise in treating patients with HHT.

CASE REPORT

A 66-year-old man, having HHT since the age of 30 years with recurrent epistaxis related to telangiectasia at the nasal septum and chronic iron deficiency anemia requiring frequent blood transfusions with iron infusions. The assessment of his disease showed septal perforation, telangiectasis in the proximal jejunum and terminal ileum, and pulmonary arteriovenous malformations. There was no improvement, despite iron infusions, repeated blood transfusions and cauterization. The patient was treated with bevacizumab at a dose of 5mg/kg/infusion every 2 weeks and was given 6 cycles. Bevacizumab, was effective without side effects.

DISCUSSION

It has been hypothesized that HHT is related to an imbalanced state between antiangiogenic factors and proangiogenic factors. Mutations of 3 genes are actually identified in HHT: ENG, ACVRL1, MADH4. The management of patients with HHT currently based on screening for visceral arteriovenous malformations and symptomatic measures are often disappointing. However, the angiogenic nature of this disease suggests an interesting therapy by using angiogenesis inhibitor. Therefore, bevacizumab was introduced as a potential therapy for HHT. Some clinical cases or small series report the efficacy of bevacizumab, in HHT with recurrent epistaxis, refractory iron deficiency anemia, gastrointestinal bleeding and also in liver vascular malformations with high cardiac output failure.

CONCLUSION

The use of modulators of angiogenesis such as bevacizumab is a possible therapeutic target in HHT.