In vitro effect of chlorambucil on human glioma cell lines (SF767 and U87-MG), and human microvascular endothelial cell (HMVEC) and endothelial progenitor cells (ECFCs), in the context of plasma chlorambucil concentrations in tumor-bearing dogs.

ABSTRACT

The objective of this study was to investigate a possible mechanism of action of metronomic chlorambucil on glioma by studying the in vitro cytotoxicity and anti-angiogenic effects on glioma and endothelial cells, respectively. The in vitro LD50 and IC50 of chlorambucil were determined using human SF767 and U87-MG glioma cell lines, human microvascular endothelial cells (HMVECs) and human endothelial colony forming cells (ECFCs). Results were analyzed in the context of chlorambucil concentrations measured in the plasma of tumor-bearing dogs receiving 4 mg m-2 metronomic chlorambucil. The LD50 and IC50 of chlorambucil were 270 µM and 114 µM for SF767, and 390 µM and 96 µM for U87-MG, respectively. The IC50 of chlorambucil was 0.53 µM and 145 µM for the HMVECs and ECFCs, respectively. In pharmacokinetic studies, the mean plasma Cmax of chlorambucil was 0.06 µM. Results suggest that metronomic chlorambucil in dogs does not achieve plasma concentrations high enough to cause direct cytotoxic or growth inhibitory effects on either glioma or endothelial cells.