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Karlis Briviba, Kerstin Schnäbele, Elke Schwertle, Mark Blockhaus, Gerhard Rechkemmer
?-Carotene Inhibits Growth of Human Colon Carcinoma Cells in Vitro by Induction of Apoptosis
Epidemiological studies suggest that ?carotene is able to modulate the risk of cancer. A number of in vitro studies reported that ?carotene inhibits the growth of cancer cells; however, so far little is known about the molecular mechanisms of the antiproliferative effect of ?carotene. Here we have investigated the effects of two ?carotene preparations, (i) ?carotene dissolved in tetrahydrofuran (final concentration in cell culture medium: 0.5%) and (ii) ?carotene incorporated in a water dispersible bead form, on cultured human colon carcinoma cells HT29. The treatment of cells with ?carotene up to 30 M for 72 h led to a significant increase in the cellular ?carotene concentration and formation of retinol. ?Carotene showed only low cytotoxicity for confluent cells tested up to 30 M, but at dietary relevant concentrations for the intestinal tract (10, 30 M) ?carotene was strongly cytotoxic for growing cells and induced apoptosis in HT29 cells as assessed by the AnnexinV assay (the maximal effect was observed 15 h after treatment with ?carotene). Exposure of cells to retinol at concentrations yielding cellular retinol levels similar to those observed by ?carotene treatment had no antiproliferative or cytotoxic effect. Furthermore, ?carotene did not affect the activation of the extracellular signalregulated kinases (ERK1 and ERK2) that are essential for cellular growth. In summary, ?carotene can inhibit growth of human colon carcinoma cells in vitro by induction of apoptosis in proliferating cells.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 382, 12/2001
Pages: 1663 - 1668