Summary Sodium butyrate has been shown to affect cell proliferation, and, at concentrations above approximately 0.5 mM, to cause cell death in some tumour cell lines. When combined with cytotoxic drugs increase in chemosensitivity has been observed. We are presently carrying out a study of the combined effects of sodium butyrate and cytotoxic drugs on cultured cervix tumour cells. To provide a baseline for this study we Prasad, 1980;Kruh, 1982;Nordenberg et al., 1987). Possibly combined with the effect of n-butyrate on cell proliferation is its action in reversibly inducing what has been termed a 'better differentiated phenotype', of increased radiosensitivity and chemosensitivity (Spremuli & Dexter, 1984). Due to these properties n-butyrate has been the subject of clinical investigations in leukaemic patients (Novogrodsky et al., 1983;Miller et al., 1987). Its effects when combined with cytotoxic drugs (Wasserman et al., 1989) or irradiation (Arundel & Leith, 1987; Leith et al., 1986) have also been investigated.We are presently carrying out an investigation of the effect of n-butyrate, when combined with a range of cytotoxic drugs, on cervix tumour cell lines when cultured as multicell spheroids. As a necessary preliminary to this study we have carried out a systematic investigation of the effect of nbutyrate alone on the growth characteristics of cervix tumour cells cultured as multicell spheroids. The effect of n-butyrate concentrations in the range 0.005 to 3 mM has been investigated, and the culture of the cells as multicell spheroids has allowed measurements over periods of up to 24 days. The results of this study are presented in this report.
Materials and methods
Cell cultureThe cervix tumour cell lines employed in this study were established in primary culture from cervix biopsy tissue taken routinely during radiotherapy at Cookridge Hospital (Dyson et al., 1984a). Six cell lines were used: 754, 612, 995, 090, 329, 708. These were maintained as monolayer cultures from which multicellular aggregates were obtained as required by using the method of Sutherland and Durand (1976). Spheroid cultures were initiated with the same number of spheroids per flask to allow intercomparison of cell counts during the period of the experiments. Multicell spheroids were maintained in culture as previously described (Boothby et al., 1989). Excess spheroids were discarded at the time of media change to maintain cell numbers approximately constant.The necessary volumes of 50 mM or 500 mM sodium nbutyrate solution were added to the spheroid suspensions at the start of the experiment to adjust to the concentrations shown in the figures, with further additions at media changes to maintain these concentrations. The butyrate solution was prepared from n-butyric acid (BDH Limited, Poole, UK) in Hanks basic salt solution, adjusted to pH 7.2 with NaOH solution, then sterilised by filtration through an 0.2 gtm Acrodisc (Gelman Sciences Limited, Northampton, UK).Spheroid diameter This was measured by means of a laser diffracti...