Bioactivity of well-defined green tea extracts in multicellular tumor spheroids.
The effect of green tea extracts (GTE) of a reproducible, well-defined composition on cellular viability, proliferation, and antioxidant defense was investigated in multicellular spheroids derived from WiDr human colon adenocarcinoma cells. The maximum GTE concentration investigated, i.e. 100 micro g GTE/ml, was equivalent to the plasma concentration commonly measured in humans drinking 6-10 cups of green tea per day. This GTE concentration lead to a substantial retardation of spheroid volume growth with diameters reaching only half the size of untreated aggregates. Flow cytometric analysis and immunocytochemistry showed an enhanced accumulation of cells in G2/M and in the non-proliferating compartment, respectively. The emergence of central necrosis occurred at larger spheroid diameters compared to control conditions leading to a significant increase (p<0.05) in the thickness of the viable cell rim (mean +/- SD) from 240+/-49.9 micro m to 294+/-69.5 micro m. This was associated with an elevation of the intracellular GSH concentration and, thus, of cellular antioxidant defense, as shown by HPLC analysis. A considerable toxicity, however, was found at these GTE levels in single cells. Cells did not adhere to culture dishes nor did they aggregate to form spheroids when plated as a suspension with GTE already in the culture medium. The findings show that green tea constituents interfere with early phases of tumorigenesis at a cellular level, e.g., by reducing cell-substratum and cell-cell interaction, enhancing G2/M arrest, and retarding spheroid volume growth. The differences in GTE effects between single cells and cell spheroids underline the importance of inclusion of spheroids in pharmaco-/toxicological testing.
Mueller-Klieser
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Institute of Physiology and Pathophysiology, Johannes Gutenberg-University Mainz, 55099 Mainz, Germany. wolfgang.mueller-klieser@uni-mainz.de
Schreiber-Klais
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S
Walenta
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Kreuter
M H
MH
D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D005260:Female; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D018874:Spheroids, Cellular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013662:Tea; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D015820:Cadherins; D018797:Cell Cycle Proteins; D019394:Ki-67 Antigen; D010936:Plant Extracts; D013662:Tea; D005978:Glutathione