Concentration- and schedule-dependent effects of chemotherapy on the angiogenic potential and drug sensitivity of vascular endothelial cells

Eddy Pasquier,Diane Braguer,Maria Kavallaris,Maria-Pia Tuset,Karen L Mackenzie,Nicolas Andre,Snega Sinnappan,Janine Street

doi:10.1007/s10456-012-9321-x

Abstract

The anti-angiogenic activity of chemotherapy is both dose- and schedule-dependent. While conventional maximum tolerated dose (MTD) chemotherapy exerts only mild and reversible anti-angiogenic effects, low-dose metronomic (LDM) chemotherapy was developed to specifically target tumour angiogenesis. However, the long-term effects of either MTD or LDM chemotherapy on vascular endothelial cells have never been investigated. Here, we demonstrated that repeated exposure to MTD and LDM chemotherapy differentially impact on the angiogenic potential and chemosensitivity of immortalized endothelial cells. Repeated MTD vinblastine treatment of vascular endothelial cells led to an increased proliferation rate and resistance to paclitaxel. In contrast, repeated LDM treatment with vinblastine or etoposide impaired the angiogenic potential of endothelial cells and increased their chemosensitivity. This effect was associated with a significant decrease in βII- and βIII-tubulin expression. Functional analysis using siRNA showed that silencing the expression of βIII-tubulin in endothelial cells significantly decreased their capacity to form vascular structures and increased their sensitivity to the anti-angiogenic and vascular-disrupting effects of chemotherapy, whereas silencing βII-tubulin expression had no effect. Collectively our results show that LDM chemotherapy impairs the angiogenic potential of endothelial cells while increasing their chemosensitivity—an effect at least in part mediated by the down-regulation of βIII-tubulin expression. Furthermore, our study suggests that βIII-tubulin represents an attractive therapeutic target to increase the anti-angiogenic effects of chemotherapy and overall anti-tumour efficacy.Electronic supplementary materialThe online version of this article (doi:10.1007/s10456-012-9321-x) contains supplementary material, which is available to authorized users.

Highlights

The discovery of the central role played by tumour angiogenesis in cancer progression and metastasis has led to the development of novel anti-cancer drugs targeting this key biological process and instigated the re-examination of conventional chemotherapy agents
Conventional and metronomic chemotherapy differentially impact on the angiogenic potential of vascular endothelial cells
BII- and bIII-tubulin gene expression were silenced in endothelial cells using small interfering RNA (siRNA) sequences whose potency and specificity have been validated previously [28, 29] and obtained from Dharmacon (Thermo Fisher Scientific, Scoresby, Australia) and Qiagen (Qiagen), respectively

Summary

Introduction

The discovery of the central role played by tumour angiogenesis in cancer progression and metastasis has led to the development of novel anti-cancer drugs targeting this key biological process and instigated the re-examination of conventional chemotherapy agents. A number of studies revealed that many of the chemotherapeutic drugs commonly used in the clinic are effective at treating cancer because they can affect both the cancer cells and the tumour vasculature [1,2,3]. This led to the development of novel treatment modalities aimed at promoting the anti-angiogenic activity of chemotherapy. The efficacy of metronomic chemotherapy is currently investigated in several phase II and III clinical trials worldwide in a variety of human malignancies (http//:clinicaltrials.gov)

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