Figure 2.

Dose-dependent effects of bombesin, BK, CCK and neuromedin B on colony formation in GLC16 and GLC19 SCLC cells. GLC16 (hatched bars) and GLC19 (filled bars) cells, 3–5 days postpassage, were washed and 10⁴ viable cells per ml were plated in SITA medium containing 0.3% agarose on top of a base of 0.5% agarose in culture medium as described in Materials and Methods. Both layers contained additions at the nanomolar concentrations indicated. Cultures were incubated at 37°C in a humidified atmosphere at 5% CO₂ : 95% air for 21 days and then stained with nitro-tetrazolium blue. Spontaneous colony formation, that is, in the absence of any exogenously added peptide was 140±15 (n=75) and 160±20 (n=85), in the cell lines GLC16 and 19, respectively, and normalised to 100%. Each point represents the mean±s.e.m. of two to four experiments each of five replicates. ^*Statistically different from neuropeptide concentration matched GLC16 cells (ANOVA, P<0.05).