Cell cycle kinetics responses of human stomach cancer cells to reduction in polyamine levels by treatment with alpha difluoromethylornithine in vitro

Two polyamine analogs (BE-4-4-4 and BE-4-4-4-4) directly affect growth, survival, and cell cycle progression in two human brain tumor cell lines

1,14-Bis-(ethyl)-amino-5,10-diazatetradecane N1,N11-bis(ethyl)norspermine (BE-4-4-4) and 1,19-bis-(ethylamino)-5,10,15 triazanonadecane (BE-4-4-4-4) are two relatively new polyamine analogs synthesized for use as antineoplastic agents. In human brain tumor cell lines U-251 MG and SF-767, both agents inhibited cell growth, were cytotoxic, induced a variable G1/S block, and depleted intracellular polyamines. Since intracellular polyamine depletion did not always correlate with growth inhibition, cell survival, or cell cycle progression, it cannot completely explain the effects of these agents on growth, survival, and cell cycle progression in U-251 MG and SF-767 cells.

Mucosal polyamine metabolism in the columnar lined oesophagus

Mucosal ornithine decarboxylase activity and polyamine content has been proposed as a possible marker for malignant potential in gastrointestinal mucosa. Polyamine content and histological findings were examined in 107 pairs of endoscopic biopsy specimens taken from gastric fundus, fundic and specialised Barrett's oesophagus and Barrett's adenocarcinoma. The content of putrescine (median nmol/mg protein, range) the primary product of ornithine decarboxylase showed a progressive increase from gastric fundus (0.41, 0.15-1.5); fundic (0.45, 0.01-4.08); specialised Barrett's oesophagus (0.54, 0.01-2.0); dysplastic columnar lined oesophagus (0.56, 0.31-3.1) to adenocarcinoma (1.23, 0.29-8.98). Adenocarcinoma putrescine content was significantly greater than gastric fundus (p < 0.018) and fundic (p < 0.03). Mucosal spermine, spermidine, and total polyamine values were greater in gastric fundus than fundic, specialised Barrett's oesophagus, and dysplastic columnar lined oesophagus (all p < 0.001) suggesting failure to further metabolise putrescine to its higher polyamines in the metaplastic epithelium. Although metaplastic columnar lined oesophagus shows significant differences in polyamine metabolic activity from the stomach the important distinction between specialised and dysplastic columnar lined oesophagus cannot be made by measuring the polyamine content.

Synergistic antiproliferative activity of human fibroblast interferon in combination with alpha-difluoromethylornithine against human gastric cancer cells in vitro

The author has studied the effects of alpha-difluoromethylornithine (alpha DFMO), an enzyme-activated irreversible inhibitor of ornithine decarboxylase; human fibroblast interferon (IFN beta); and their combination on human gastric cancer cell growth in vitro. alpha DFMO (from 0.1 to 4 mmol/l) inhibited cell growth in a dose-dependent manner. Both alpha DFMO (0.1 mmol/l) and higher doses of IFN beta (100 and 1000 IU/ml) caused only limited inhibition of cell growth. When alpha DFMO (0.1 mmol/l) was administered in combination with IFN beta (100 and 1000 IU/ml), synergistic antiproliferative activity was observed 7 days after continuous exposure. Although the mechanisms by which this effect occurs are unclear, it appears to be associated with direct inhibition of tumor cell proliferation, possibly by modulation of polyamine metabolism.

Schedule dependent potentiation of antitumor drug effects by alpha-difluoromethylornithine in human gastric carcinoma cells in vitro

A clone of human gastric cancer cells (AGS-6) and the parental line (AGS-P) from which it was isolated were used in cell survival studies to determine whether pretreatment for 24, 48 or 72h with alpha-difluoromethylornithine (DFMO, 5mM) would increase the cell's sensitivity to 5-Fluorouracil (5FU), Adriamycin (Adria), 1-(2-chloroethyl)-3-(4-methyl cyclohexyl)-1-nitrosourea (MeCCNU), or Bleomycin (Bleo). Generally, the AGS parental cells were most sensitive to the anticancer agents after exposures to DFMO. However, there was no way to predict in advance from DFMO-induced changes in ornithine decarboxylase (ODC), polyamine or cell kinetics values, how long an exposure to DFMO was required before sensitization to an anticancer agent occurred. The degree of potentiation for a single drug was variable from time to time during exposure to DFMO, and broad differences in the sensitizations were demonstrated among the four anticancer drugs. The AGS-6 clone exhibited little or no increased sensitivity as a result of pretreatment with DFMO, even though the DFMO-induced reductions in ODC and polyamine values in these cells were similar to those produced in the more sensitive parental line.

Heterogeneous survival and cell kinetics responses of human astrocytoma clones to alpha-difluoromethylornithine in vitro

The effects of alpha-difluoromethylornithine (DFMO) on survival, cell kinetics and polyamine levels were studied on two clones of human astrocytoma in vitro. The survival responses were dose and time dependent; and treatments with DFMO which lasted for 72 h resulted in heterogeneous responses with one clone being up to 6 times more sensitive than the other. Shorter treatments produced more uniform killing in the clones. A continuous exposure of the cells to 5 mM DFMO resulted in a rapid decrease in putrescine values in both clones, followed by decreases in the spermidine levels. These effects were closely followed by 148% to 170% increases in cell population doubling times, and a lowering of saturation densities. No clear correlations could be established among baseline polyamine levels and cell kinetics or survival responses to DFMO treatments.