OBJECTIVETo observe the effect of selenium and zinc alone or in combination on the growth and proliferation of human esophageal cancer Eca109 cell line in vitro.

METHODSDifferent doses of sodium selenite and zinc sulfate were added into the culture medium of Eca109 cells and normal liver epithelial HL7702 cells (control), and the changes in the cell growth were assessed by means of cell growth curve, (3)H-thymidine incorporation assay and flow cytometry.

RESULTSHigh-concentration selenium (0.3 micro g/ml) and zinc (3.5 microg/ml) alone both obviously inhibited Eca109 cell proliferation, and the inhibitory effect was enhanced by a combined treatment. At high concentrations, both selenium and zinc promoted HL7702 cell proliferation, but when combined, they produced inhibitory effect on the cell growth. Selenium and zinc at the physiological concentrations ( 0.1 microg/ml and 1.0 microg/ml, respectively) produced similar effects on Eca109 cells and the control cells. Selenium at 0.3 microg/ml caused Eca109 cell growth arrest in S phase, but this effect was not statistically significant; 3.5 microg/ml zinc significantly increased the number of Eca109 cells in G(1) phase. When combined, 0.3 microg/ml selenium and 3.5 microg/ml zinc caused significant G(1) arrest and promoted apoptosis of the cancer cells, an effect stronger than that of either of the agents used alone.

CONCLUSIONHigh-concentration selenium and zinc show a synergetic effect in inducing growth inhibition of human esophageal cancer Eca109 cell line possibly by causing cell cycle arrest and promoting cell apoptosis, and their combined use can be toxic to normal human liver epithelial cells.