Density-dependent inhibition of growth, plating efficiency on confluent monolayers of 3T3 cells, and growth in agar have been measured in epithelial tumor cell lines to determine whether they have properties in common with transformed mesenchymal cells. Five lines (RT4, RT112, J82, T24, and EJ) were derived from different human bladder tumors and HT29 was from a human colon tumor. All the lines resembled transformed "fibroblasts" in the absence of density-dependent inhibition of growth and the cell-surface large external transformation-sensitive protein, and they could form colonies on 3T3 monolayers. Only RT112, EJ, and HT29 were tumorigenic in nude mice, and the tumors had many of the structural and ultrastructural features of both the original tumor and the tissue of origin, even though the cells had been through many in vitro passages. Four of the lines (J82, T24, EJ, HT29) grew in agar, so that in some cell lines no correlation of growth in agar with tumorigenicity in nude mice was found: J82 and T24 were nontumorigenic and grew in agar, whereas tumorigenic line RT112 did not grow in agar. The ability to grow in agar did not appear associated with the production of high levels of plasminogen activators.

No abstract

Viability, DNA synthesis and mitosis have been followed in the temperature sensitive Chinese hamster cell mutant K12 under permissive and non-permissive conditions. On incubation a t 40°C cells retained their ability to form colonies at 3 3°C for 15 to 20 hours, but viability was lost gradually during the following 20 hours. When random cultures of K12 were shifted to 40°C the rate of DNA synthesis was normal for three to four hours but then decreased markedly, reaching 95% inhibition after 24 hours. Under the same conditions mitosis was inhibited after 15 hours. If cultures which had been incubated at 40°C for 16 hours were placed at 33°C the rate of DNA synthesis increased five hours after the shift down and mitosis 18 hours after. These results can be interpreted on the assumption that K12 at 40°C is unable to complete a step in the cell cycle which is essential for DNA synthesis and which occurs three to four hours before the start of S at 33°C.The preceding paper described the isolation of a temperature sensitive mutant K12 derived from the Chinese hamster cell line Wg-1A (Roscoe, Read and Robinson, '73). K12 was selected from a large population because it detached relatively easily from a glass substrate at the nonpermissive temperature. It was found to have a very low spontaneous reversion rate (less than 1 in 6 X lo7) and over a period of 48 hours at 40°C K12 cells stopped growing and became fully rounded in contrast to a normal spread configuration and good growth at 33°C. In this paper experiments with K12 and Wg-1A are reported which describe the effect of temperature shifts between 33 O C and 40 O C on viability, DNA synthesis and mitosis. MATERIALS AND METHODS CellsWg-lA, the isolation of K12 and the growth medium used have been described previously (Roscoe, Read and Robinson, '73). Stocks of cells were maintained at 31 "C with transfers at weekly intervals. Experiments were carried out at 33°C or 40°C in plastic bottles (Falcon Plastics) or Petri dishes (NUNCLON).For continuous observation of cells at 33°C or 40°C micrographs of cultures were taken at intervals of 90 or 120 seconds using 16 mm cine film. When cells were shifted from low to high temperature or vice-versa the constant temperature cabinet and microscope equilibrated within one hour. The resulting films were analysed using a cine projector fitted with a frame counter. Measurement of D N A synthesis: (i) By thymidine incorporationThe method used was based on that described by Bachetti and Whitmore ('69). All the Petri dishes (50 mm diameter) for a given experiment were inoculated from one cell suspension with about 5 X 104 cells; they were then incubated for 24 hours at 3 3°C before a n y required temperature shifts. In these experiments operations at 40°C were performed in a constant temperature room. For each point at which the rate of DNA synthesis was to be measured the medium was carefully removed and replaced with fresh growth medium containing 0.5 pC/ml "H-thymidine (TdR; 5.25 C per mmole). In some experiments "H-TdR was a...

No abstract