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Summary In order to quantitate the effects of tumour subpopulation interactions, we have devised a method to determine the subpopulation composition of tumours by using paired tumour cell lines able to grow in different selective media. Line 4T07 forms colonies in thioguanine but not in HAT and line 168 forms colonies in HAT but not in thioguanine. An

Our studies caution against the use of IL-2 gene-transduced syngeneic stromal cells as an alternative strategy of gene therapy for cancer. However, they may allow study of the mechanisms of tumor antigen recognition and the possible involvement of co-stimulatory signals for effective tumor vaccination by gene-modified cells.

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Summary In order to examine in detail the sensitivity to chemotherapy of tumour cells at various organ sites and at various stages of metastasis, we have used a series of cell lines, all selected from sister subpopulations derived from a single mouse mammary tumour, which can be distinguished and quantitated from normal cells and from each other through growth in selective medium. For the studies described here, we used two lines, 4T07 and 66FAR, which will form colonies in vitro in medium containing 60 iM 6-thioguanine Material and methods MiceMale BALB/c mice 8 to 12 weeks old were produced in our animal colony, which was established by caesarean derivation of a litter of mice from BALB/cfC3H parents obtained from the Cancer Research Laboratory, Berkeley, CA. Tumour cell lines used in the experiments described here grow and respond to chemotherapy equally well in male and female mice.Tumour cell lines Tumour subpopulation lines 66 and 410.4 were isolated from a single spontaneously arising mammary tumour from a BALB/cfC3H mouse (Miller et al., 1983;Dexter et al., 1978). Line 66FAR is a diaminopurine (and fluoradenine) -resistant variant of line 66 obtained by stepwise selection in increasing concentrations of diaminopurine, followed by 5-fluoroadenine. Line 4T07 is a thioguanine-, ouabain-resistant variant of line 410.4 (Miller et al., 1987). Doubling times for these cultures in vitro were approximately 15 h, 18 h, and 13 h for lines 4T07, 66FAR, and 66, respectively (n = 3). Plating efficiencies averaged 64% (n = 8 cultures per cell line) and were not significantly different for the three lines.Cell culture Cells were grown in monolayer in DME-10, DME supplemented with 2.5% foetal bovine serum, 7.5% calf serum, 1 mM mixed non-essential amino acids, and 2 mM L-glutamine. Cultures were split and recultured twice a week, using 0.25% trypsin plus 0.05% EDTA in Hanks buffered salt solution to remove cells from the tissue culture flasks. Experimental metastasisCells from culture were suspended with trypsin/EDTA, rinsed once, and suspended in DME-10. Cell suspensions (usually 2.5 x 106 ml-') were injected intravenously via the lateral tail vein at 0.2 ml/mouse.