RESTORATION OF GROWTH-CONTROL IN MALIGNANTLY TRANSFORMED MOUSE FIBROBLASTS GROWN IN A CHEMICALLY DEFINED MEDIUM

  • 1 January 1978
    • journal article
    • research article
    • Vol. 38  (2) , 444-451
Abstract
The expression of growth control and morphological transformation was studied in methylcholanthrene-transformed C3H10T1/2 CL8 cells serially propagated in CDM [chemically defined nutrient medium] by exposing cells to albumin (0.1%) before dispersing them with trypsin (50 .mu.g/ml). In serum-supplemented media, methylcholanthrene-transformed C3H/10T1/2 CL8 cells exhibit various aspects of the transformed phenotype such as irregular morphology, extensive cell overlap, lack of density-dependent inhibition of division, a saturation density of 1.1 .times. 105 cells/cm2 and tumorigenicity in vivo. Cell phenotype in CDM was dramatically altered. Methylcholanthrene-transformed C3H/10T1/2 CL8 cells adapted to CDM exhibited a regular epithelioid morphology with no cell overalp and formed confluent monolayers of nonproliferating cells at a saturation density of 5 .times. 104 cells/cm2. The mean generation time of logarithmic phase cells was 25-27 h. Reversion to the transformed phenotype followed addition of albumin (0.1%) or serum (2%) to logarithmic-phase cultures or exposure (30-60 s) to trypsin (10 .mu.g/ml). Cultures in CDM reexposed to serum remained highly tumorigenic in vivo. Absorbed proteins may block transformation-sensitive cell surface sites responsible for growth control and these sites are inactivated by trypsin.