GROWTH-CHARACTERISTICS AND HA-RAS MUTATIONS OF CELL-CULTURES ISOLATEDFROM CHEMICALLY-INDUCED MOUSE-LIVER TUMORS

Cells have been isolated from liver tumours that have arisen in contro l C3H/He mice, in mice given 10 mu g diethylnitrosamine (DEN) during t he neonatal period or in mice given a diet containing phenobarbitone ( PB) to allow a daily intake of 85 mg/kg/day. The cells were grown to t he 8 degrees subculture when their growth characteristics were investi gated in monolayer culture and following suspension in soft agar and o n transplantation into nude mice. In addition, DNA was isolated from t he cultures and from tumours that grew in nude mice and analysed for m utations at codon 61 of the Ha-ras oncogene. All cells derived from DE N-induced hepatocellular carcinomas (HCC) demonstrated a lack of densi ty inhibition of growth in monolayer culture, grew in soft agar and fo rmed tumours in nude mice with an average mean latency of 29 days. Thr ee of the seven lines showed mutations in Ha-ras: two were CAA --> AAA transversions and one showed a CAA --> CTA transversion. In contrast, cells isolated from eosinophilic nodules in mice given PB showed inhi bition of growth at confluence, did not grow in soft agar and only fou r of eight formed tumours in nude mice with a mean average latent peri od of 181 days. Cells grown from HCC in mice given PB showed a lack of density inhibition of growth, however they did not grow in soft agar nor did they form tumours in nude mice. A single spontaneous HCC from a control mouse showed a similar growth pattern to HCC cells isolated from mice given PB. Cells from a basophilic nodule, taken from a contr ol untreated mouse grew vigorously in culture and in soft agar and for med tumours in nude mice with a latency of 6 days. None of the cells i solated from control mice or from mice given PB showed evidence of mut ations at codon 61 of Ha-ras. These data confirm that there are fundam ental differences in the biology of cells grown from tumours that deve lop in mice under different treatment regimes. These studies also demo nstrate the utility of cell culture and molecular biology in addressin g the fundamental mechanism of mouse hepatic neoplasia.