Differential effects of cytochalasin B and caffeine on control of DNA synthesis in normal and transformed cells

Abstract

Evidence is presented which suggests the existence of a t least two growth control points in cultured mammalian cells. These controls are in "parallel" rather than in "series." It is suggested that in normal and some transformed cells the controls are coupled while in SV40 transformed cells and tumor cells they are uncoupled. One control is revealed by cytochalasin B (CB) treatment since in normal and some kinds of transformed cells, CB treatment results in the accumulation or the arrest of cells in G1. In this case, the control is normal or coupled. In DNA tumor virus transformed cells and many cultured tumor cells (excluding human glioblastomas) CB does not arrest cells although it prevents cytoplasmic division. Such cells continue DNA synthesis and nuclear division and become highly multinucleated. The effects of CB are not concentration dependent. Here the control is defective or uncoupled. Another control is revealed by caffeine treatment. Again, normal and some types of transformed cells are accumulated in G1 following caffeine treatment, while SV40 transformed cells and tumor cells continue DNA synthesis unabated. The effects of caffeine in arresting cells are concentration dependent. Similarly the control point revealed by caffeine is coupled in normal cells and altered or uncoupled in some SV40 transformed and tumor cells. Although CB and caffeine do not inhibit DNA synthesis in tumor and SV40 transformed cells when administered separately, they cause G1 accumulation when administered in combination. This observation can be explained by the possibility that some transformed cells can utilize alternate or parallel mechanisms to progress through G1 when one mechanism is blocked (CB or caffeine). When both are blocked the cells become arrested in G1. The human glioblastomas are unique among the cultured human tumors thus far examined since they are partially arrested by CB. However they are like other human tumors in that caffeine does not significantly affect DNA synthesis.Previous observations have shown a differential response to cytochalasin B (CB) or caffeine among normal and transformed cells. In CB treated normal cells nuclear division and DNA synthesis are inhibited in the absence of cytoplasmic cleavage (Wright and Hayflick, '72; Kelly and Sambrook, '73; ONeill, '74; ONeill et al., '75; Hirano and Kurimura, '74). In contrast CB treated DNA virus transformed cells and many kinds of tumor cells show continued DNA synthesis and nuclear division in the absence of cytoplasmic division (Wright and Hayflick, '72;

Caffeine and human DNA metabolism: the magic and the mystery

“…Caffeine has long been known to induce a G1 delay in mammalian cells [65][66][67], and we showed that caffeineinduced ~75% inhibition of G1/S progression in diploid human fibroblast strains. ATM and p53 were not required as AT cells and cells expressing HPV16E6 to inactivate p53 also arrested in G1 when incubated in caffeine.…”

Disruption of actin microfilaments by cytochalasin D leads to activation of p53

“…This means essentially normal segregation of chromosomes and filial nucleus formation. Therefore, treatment of the cells with CD results in formation of multinuclear cells in culture [26, 29, 30]. In our recent study we have shown that spontaneously derived or colcemid‐induced micronuclei cause activation of p53 with strong dependence on their number [31].…”

Spectroscopic and molecular modeling studies of caffeine complexes with DNA intercalators

“…This relatively high daily consumption, as well as the abundance of methylxanthines (primarily caffeine) in dietary substances, has stimulated extensive research into the question of methylxanthine toxicity particularly with respect to coronary heart disease and cancer (Bertrand et al, 1970;Jick et al, 1973;Mann and Thorogood, 1975;Rall, 1980;Curatolo and Robertson, 1983;Dews et al, 1984;Pozniak, 1985). Caffeine has been shown to inhibit enzymes required for DNA synthesis, cause an increase in chromatin condensation, increase the length of the GI phase, and exhibit antimutagenic activity against N-methyl-N'-nitro-N-nitrosoguanidine (Borodina et al, 1979;O'Neal, 1979;Levin, 1982;Roberts, 1984;Kunicka et al, 1990;Selby and Sancar, 1990). In the presence of DNA-modifying agents, high concentrations of caffeine (>10 mM) appear to enhance cell mortality (Roberts, 1984).…”