The possible antiproliferative potency of human recombinant interferon-beta (hIFN-beta) towards ten human esophageal cancer cell lines was examined in comparison with the activity of the factor towards human malignant melanoma cell lines. The cell growth of esophageal cancer cell lines was inhibited by hIFN-beta in a dose- and time- dependent manner. The 50% inhibitory concentrations (IC50) of hIFN-beta on nine cell lines out of ten ranged between 23 to 332 IU/ml of culture medium. The remaining cell line, T.Tn, was less sensitive to the interferon (IC50, 611 IU/ml). Under the same culture conditions, the melanoma cell lines tested differed markedly in their sensitivity to hIFN-beta. When the esophageal cancer cells were treated with 5-fluorouracil (5-FU) in the presence of a low concentration of hIFN-beta, the effectiveness of 5-FU was markedly enhanced. In particular, the rate of growth inhibition of T.Tn cells was more than the added potencies of 5-FU and hIFN-beta indicating that the interferon is an effective biomodulator of 5-FU. All these data suggest that combination therapy with hIFN-beta and the anticancer drug 5-FU would be beneficial for the treatment of carcinoma of the esophagus.
Changes of electrical cell-surface charge associated with cell cycle were examined electrophoretically in the synchronous culture of HeLa S3 cells. The electrophoretic mobility of the cells increased abruptly in the mitotic phase as high as 45% compared with that of cells in the S phase. This difference of mobility was obtained by comparing pure population of mitotic cells and S-phase cells. Mitotic cells were also found to be more susceptible to neuraminidase than S-phase cells in term of electrophoretic mobility, a greater amount of sialic acid being correspondingly released from the former. The mechanism of the electrokinetic change associated with the processes of cell cycle is discussed, with special reference to the distribution of electric charge in the cell surface membrane.
When human esophageal cancer cells were transfected with the human interferon-beta (hIFN-beta) gene entrapped in cationic multilamellar liposomes, the growth of all cancer cells tested was suppressed in a dose-dependent manner. The 50% inhibitory concentration (IC50) of the hIFN-beta gene entrapped in the liposomes ranged from 16 to 176 ng plasmid DNA/ml culture medium. Among the 10 cell lines examined, NUEC3, NUEC4, TE-3 and WSSC cell lines were highly susceptible to transfection with this gene entrapped in the liposomes. The IC50 values of the hIFN-beta gene entrapped in the liposomes with respect to cell growth were positively-correlated with those of exogenous cytokine hIFN-beta, suggesting that the antiproliferative effect of hIFN-beta gene entrapped in the liposomes can be mainly ascribed to the function of hIFN-beta produced by cells transfected with the gene. Two days after transfection with the liposome-entrapped gene, the concentration of hIFN-beta secreted into the medium was determined. Even though the level of hIFN-beta observed in the medium was lower than that of the IC50 of exogenously added hIFN-beta, the inhibitory potency of the hIFN-beta gene entrapped in the liposomes on the cell growth was remarkable. When the esophageal cancer cells were treated with 5-fluorouracil (5-FU) in the presence of a low concentration of liposome-entrapped-gene, the rate of growth inhibition of these cells increased over that caused by either 5-FU or hIFN-beta gene entrapped in the liposomes alone. All these data suggest that combination therapy with the hIFN-beta gene entrapped in cationic multilamellar liposomes and the anticancer drug 5-FU would be beneficial for preoperative treatment of carcinoma of the esophagus.
