The cytotoxic effects of three anticancer drugs, methotrexate (MTX), 5-fluorouracil (5-Fu) and oridonin (Rub A), were investigated using a human gastric adenocarcinoma cell line (MGc80-3) and a human esophageal cancer cell line (CaEs-17) by means of colony-forming assay, dye exclusion test, measurement of incorporation of 3H-thymidine into DNA and examination of mitotic index. MGc80-3 cells, exposed for 24 hr to increasing concentrations of MTX (0-1.6 micrograms/ml), 5-Fu (0-12 micrograms/ml) or Rub A (0-25 micrograms/ml), showed different types of dose-survival curves determined by colony-forming assay. It suggests that these drugs have different models of action. The killing effect of MTX and 5-Fu was obviously underestimated by dye exclusion; the cell numbers were reduced to about 30% and 60% of control, while the colony formation showed approximately 2.5 and 3.5-log kill. When CaEs-17 cells exposed for 6 hr to varying concentrations of Rub A (0-15 micrograms/ml), the reduction in cell number (15 micrograms/ml, T/C = 18.0%) was always less than that (15 micrograms/ml, T/C = 3.8%) in colony formation. Under the same condition, the mitotic index, however, increased with increasing dosage first, and then the T/C values, at higher concentrations (5-15 micrograms/ml), reached approximately 200%. Although the drug significantly inhibited the incorporation of 3H-thymidine, the pattern of the dose-response curve differed from the dose-survival curve. These findings in cytobiochemistry and morphology may contribute to explain the cytotoxicity of an anticancer drug, but failed in correlation with the data obtained by colony-forming assay which seems to be the most reliable method for determining drug-induced cell lethality.

The effect of retinamide on the subcellular structure of esophageal cancer epithelial cells(ECa109-C3) was observed by transmission electron microscope. Cells, treated with 10 micrograms/ml retinamide for 1, 2, 3, 4 and 5 days, gave the following changes: 1. The number of the microvilli decreased. 2. The number of the tonofilaments and desmosomes increased. 3. polyribosome decreased in amount or disappeared. 4. The ratio of the nucleus/cytoplasm reduced. These changes varied with the time of retinamide treatment. In the early stage, the structural changes, resembling that in ECa109-C3 cells treated with DMSO, showed some characteristics of the normal esophageal epithelial cells. These results show that the retinamide can induce the differentiation of the esophageal epithelial cancer cells. In the late stage, the retinamide caused the swelling of mitochondria, blurring of cristae, dispersion of Golgi complexes, appearance of more lysosomes and degeneration of cancer cells.