COMBINED TREATMENTS OF HEAT, RADIATION, OR CYTOKINES WITH FLAVONE ACETIC-ACID ON THE GROWTH OF CULTURED ENDOTHELIAL-CELLS

The antitumour effects of flavone acetic acid (FAA) against a broad sp ectrum of established experimental tumours has been demonstrated. Dama ge to the vasculature. which rapidly disrupts blood flow and induces h aemorrhagic necrosis, is believed to be a major mechanism contributing to the observed antitumour effects. Despite these established observa tions, FAA has shown little effect against human tumours. However, oth er applications of FAA, for examples, for an extended period of treatm ents or in combination with other antitumour modalities, have not been sufficiently explored. In order to test the direct effects of FAA on vasculature, endothelial cells isolated from human umbilical vein (HUV EC) and bovine pulmonary artery (CPAEC) were used in this study. FAA a t the concentrations of 50 to 200 mug/ml causes reduction in cell numb er (from 20 to > 30% of the cells) of HUVEC as measured by MTT assay a fter 1, 3, and 5 h of treatment at 37-degrees-C. FAA did not produce s ignificant effects on similarly treated human squamous cell carinoma, cell line UM-SCC-2. After 1 h treatment of FAA at 300 mug/ml, a large number of HUVECs failed to react with an actin stain, NBD-phallacidin. The growth of HUVECs and CPAEC in the presence of FAA for 1-3 days wa s progressively reduced. The number of HUVEC treated for 3 days at the concentrations of 100, 200, and 300 mug/ml were reduced by 75-86% in comparison with the control culture. The experiments with CPAEC showed similar results. The inhibition of the growth of endothelial cells by FAA was enhanced when it combines with tumour necrosis factor-alpha b ut not with interleukin-1, interferon-gamma, heat, or radiation. We ob served that FAA can initiate both immediate effects and growth inhibit ion on cultured endothelial cells. These results support the notion th at FAA rapidly induces vasculature damage. Furthermore, cytokines such as tumour necrosis factor-alpha can enhance the toxicity of FAA on en dothelial cells.