The effects of very low doses of chemotherapeutic drugs on endothelial cells.

Abstract

e23014 Background: Angiogenesis is one of the key processes leading tumor progression and metastasis. Conventional chemotherapeutic drugs are usually cytotoxic to tumor cells at the therapeutic doses. The lowered doses of those drugs have been shown to induce apoptosis in endothelial cells and implemented as metronomic schedule in the clinic. We aimed to study the effects of very low doses of chemotherapeutic drugs on endothelial cell functions and gene and protein expression of pro-and anti-angiogenic factors. Methods: We first determined the IC50 doses of 5-fluorouracil, irinotecan, and oxaliplatin in a human umbilical endothelial cell line (HUVEC). Then we’ve tested the effects of the IC50, -1log, -2log and -3log of IC50 doses on endothelial cell migration and tube formation. We’ve also studied the effects of the assigned doses on expression levels of the genes VEGF-A, VEGFR2, PDGF-B, angiopoietin-2 (Ang-2), endothelin-1 (End-1), thrombospondin-1 (Tbs-1), iNOS, eNOS by real-time PCR, protein secretion levels of VEGF-A, PDGF-BB, Ang-2, End-1 and Tbs-1 by ELISA and nitrate/nitrite production by a colorimetric assay. Results: The IC50 dose levels of 5-FU, irinotecan, and oxaliplatin were 9,2 μM, 9,8 μM and 11,8 μM, respectively. We found that all the -1log, -2log and -3log of IC50 doses of the drugs tested in the study significantly decreased the migration capacity of the HUVEC cells. However, no significant changes were observed in tube formation of endothelial cells. Likewise, the expression levels of pro-angiogenic genes including Ang-2, iNOS, eNOS, PDGF-B and VEGF-A were significantly decreased at the same doses of the drugs. Accordingly, the levels of Tbs-1 were significantly increased at all 3 dose levels of the drugs. The most efficacious doses of the drugs to decrease NO levels in HUVEC cells were -1logIC50 for 5-FU, -2logIC50 for irinotecan and -3logIC50 for oxaliplatin. Conclusions: In conclusion, our results suggest that 5-FU, irinotecan, and oxaliplatin could decrease the pro-angiogenic and increase anti-angiogenic factor production in endothelial cells at the doses much lower than the usual metronomic schedules and warrant further research in animal models and clinical trials as an anti-angiogenic treatment modality.