Activation of c-jun and c-fos genes in dNTP imbalance cell death induced with 5-fluoro-2'-deoxyuridine in mouse mammary tumor FM3A cell line

5-Fluoro-2' -deoxyuridine (FdUrd)-induced death of mouse mammary FM3A cells was found to be associated with an increased expression of cellular c-jun and c-fos genes. The increase in these gene expressions was mediated through the protein kinase C-dependent pathway. Blockage of the expressions with the use of antisense oligodeoxynucleotide for c-jun delayed the cell death. These findings suggest that the activation of c-jun and c-fos genes, which encode transcription factors participating in cell proliferation, plays a role in FdUrd-induced cell death.

Different modes of cell death induced by 5-fluoro-2'-deoxyuridine in two clones of the mouse mammary tumor FM3A cell line

The mode of cell death induced by 1 microM 5-fluoro-2'-deoxyuridine (FdUrd) changed in a wild-type F28-7 clone of mouse mammary tumor FM3A cells after a six-month culture. In the original stocked F28-7 clone, FdUrd-induced cell death was accompanied by necrosis-like cell swelling and DNA fragmentation to 100-200 kbp. In subclone F28-7-A isolated from F28-7 cells, which had been cultured for six months, apoptotic bodies and nucleosomal DNA-ladder fragments were observed with the treatment. Furthermore, we investigated the differences in FdUrd-induced intracellular signals between these clones. In F28-7 cells, FdUrd induced increases in caspase-3-like activity, and the mRNA levels of the c-jun, c-fos and c-myc genes, which were greater and earlier than those in F28-7-A cells. Moreover, intracellular acidification occurred in F28-7-A cells treated with FdUrd, though it was not observed in F28-7 cells. These findings suggest that FdUrd-induced cell death occurred through the death program to cell lysis (necrosis) without apoptosis when the induction of these intracellular signals was very high and when intracellular acidification was deficient. Investigation of the differences in the mode of FdUrd-induced cell death between these clones would be important for elucidating the molecular mechanism of pivotal events guiding cells toward either apoptosis or necrosis.

The molecular mechanisms of 5-fluoro-2'-deoxyuridine induced cell death

The molecular mechanism of cell death induced by 5-Fluoro-2'-deoxyuridine (FUdR) was investigated. FUdR caused cell death to induce dNTP pool imbalance and following DNA double strand breaks in mouse mammary tumor FM3A cells. We isolated a new endonuclease from FUdR-treated cells, named endonuclease S, that played an important role in FUdR-induced cell death. Cells treated with FUdR showed intracellular acidification before cell death formation. We observed that the endonuclease S in acidic cells may lead the DNA fragmentation. On the other hand, we observed that protease inhibitors (such as TLCK, TPCK, PMSF, p-APMSF, Pefabloc SC and Z-Asp-CH2-DCB) blocked intracellular acidification, DNA fragmentation and FUdR-induced cell death. But the inhibitors did not affect dNTP pool imbalance in the cells. These results suggest that proteases act at the point of downstream of dNTP pool imbalance and upstream of the intracellular acidification.

Hexacosanoate contents in Japanese common foods

Recently, a diet enriched in oleate and moderately restricted in hexacosanoate (C26:0) was found effective to reduce the plasma very long chain fatty acid (VLCFA) levels in patients with adrenoleukodystrophy (ALD), an X-linked disorder characterized by demyelination of the adrenal cortex and cerebral white matter, and accumulation of saturated VLCFA, particularly C26:0, in tissues of the demyelination. The information about the C26:0 content in Japanese food was, however, almost nil except for one report about foods in the USA, but this did not include some Japanese common foods. With the hope of treating an ALD patient in our hospital, C26:0 contents in Japanese common foods (42 items) were measured. In our case, a one-hour direct transesterification method was used to obtain methylesters of total fatty acids in foods and they were applied directly to a selected ion monitoring gas chromatography-mass spectrometry for the quantitative C26:0 analysis. The C26:0 content in nuts and seeds as well as in fats and oils was found to be significantly higher than in other foods; the content was highest in peanuts. The content in almost all kinds of examined fishes, the common protein foods in Japan, was relatively low. From these data and that in the national nutrition survey in 1986, the daily intake of C26:0 from the average Japanese diet could be estimated to be 12-36 mg. It can be recommended, therefore, that nuts and seeds as well as fats and oils should be restricted as severely as possible from the diet of ALD patients in Japan in order to keep daily C26:0 intake below 10 mg as recommended in the USA.