Hormonal regulation of the transformation phenotype in simian virus 40-transformed rat embryonic preadipose cell lines.

Abstract

The regulation of transformed phenotypes was studied in newly isolated preadipose cell lines which were established after infection with simian virus 40 tsA58 dl2009. The clonal cell lines isolated exhibited most of the characteristics typical of transformed cells. The transformants, however, were able to differentiate into adipocytes in the presence of low calf serum (0.5%) and a combination of several hormones, including hydrocortisone and insulin. Treatment with insulin alone stimulated the growth of these cells but did not induce lipid accumulation without added hydrocortisone. The effect of hydrocortisone was accompanied by a restoration of growth control in the transformants after they reached high cell density. The blot hybridization analysis of cellular DNAs digested by restriction enzymes revealed that simian virus 40 genomes were integrated at multiple separate sites at which a head-to-tail oligomeric insertion took place. Large T antigen was synthesized in growing cells but was regulated at high cell density when cells were committed to differentiate by glucocorticoids. These results suggest that the glucocorticoid hydrocortisone is capable of restoring growth regulation at high cell densities to simian virus 40-transformed preadipose cell lines.

Hydrocortisone Promotes the Neodifferentiation of Kirsten Murine Sarcoma Virus Transformed Human Skin Fibroblasts to Adipose Cells: Relevance to Oncogenic Mechanisms

“…Moreover, although both growth hormone and HC are anabolic agents, other low-molecular weight com pounds for which no such function could be assigned, including heme, have been impli cated in preadicpocyte conversion of murine cells [2,5,6,18,22,24,28,35]. In addition, SV40-transformed rat embryo preadipocytes have been shown to convert into adipose cells in the presence of HC [36]. In this con text, mouse preadipocytes have also been shown to convert to fat cells when transfected with the middle T of polyoma virus [8], However, such conversion has been demon strated with preadipocytes only and is, there fore, more likely to represent yet another mechanism fuctionally analogous to HC and growth hormone.…”

Differential early viral gene expression in two stages of human papillomavirus type 16 DNA-induced malignant transformation.

“…NIH 3T3 cells transfected with pMHPV16d acquired the ability to grow in reduced serum concentrations shortly after transfection. This ability was also observed after transformation by viruses such as simian virus 40 or Rous sarcoma virus (7,16,30,37,40); viral functions perturbed growth control but did not induce malignant transformation (30,45 (19,25), suggesting that a particular viral genome-host cell interaction is required for neoplastic conversion (19 (32). Although these putative transforming genes are biologically active in the BPV-1-C127 model, the most abundant transcripts are sequences from the downstream end of the early region (E2, E4, and E5) (1,10,15 E6, E7, E4, and E5 transcripts also occurred in transformed PM3T3Fo lines, although the total quantity of these messages was very low.…”