Kinetic Analysis of Hydrocortisone Effect on the Neodifferentiation of Kirsten Murine Sarcoma Virus-Transformed Human Skin Fibroblasts to Adipose Cells

Abstract

Here we have demonstrated that transformation of human skin fibroblasts (SF) by the Kirsten murine sarcoma virus (KiMSV) is associated with their neodifferentiation into preadipose cells. Hydrocortisone (HC) and dexamethasone (DX) promoted the transformation/neodifferentiation of preadipocytes into mature fat cells. The effects of HC on the expression of adipocyte-containing foci (ACF) and on the total number of transformed foci (TTF) present in KiMSV-treated SF cultures were optimal at a concentration of about 500 ng/ml, or 1.25 X 10(-6) M. At this concentration of HC, the occurrence of ACF varied between 25 and up to 100% of the TTF formed in virus-treated cell cultures. In contrast, equimolar concentrations of estrogenic, androgenic, or progestational steroids inhibited ACF formation. The continued presence of HC post virus inoculation was necessary to effect optimal adipocytic conversion in KiMSV-treated cultures. Moreover, cell cultures that were "primed" with HC for up to 25 days or more prior to virus inoculation showed a further increase of TTF and of ACF at 14-21 days postinoculation. It is likely that the ras oncogene and HC can effect transformation/neodifferentiation of cells in a variety of normal or diseased human tissues de novo.

Transformation/Neodifferentiation of Human Skin Fibroblasts by Acute Oncornaviruses and Dexamethasone

“…1). The ex tent of adipocytic conversion (adipocytecontaining foci [7,20] of HSF by HaMSV and DX, like that by KiMSV, was in the range of 23-100% of the total number of transformed foci present (table II). Adipo cytic conversion by KiMSV and HaMSV was associated with increased GPDH activ ity (table III).…”

“…Scoring of transformed foci was done through (a) direct visuali zation of live cultures under the light microscope (40 X) and (b) by specific staining. Adipocyte-con taining foci in virus-infected cell cultures were iden tified with 0.2% oil red O essentially as described [7], The positively stained foci were marked, and the cultures were destained, fixed and restained with Giemsa for a total focus count [7,20,21]. Glycerol-3-phosphate dehydrogenase (GPDH) activity was as sayed according to Kopelovich et al [8] as modified elsewhere [22].…”

“…Virus stocks were propagated essentially as de scribed previously [7,14,20,21). Seven replication/transformation-competent oncornaviruses were studied (table I).…”

“…Hydrocortisone (HC) or dexamethasone (DX) promoted transformation/neodifferentiation of preadipocytes to fully differentiated adipose cells [7,20,21], Other presumptive adipogenic agents [22,23], notable among which is 5-azacytidine [24], were found to be ineffective in the human cell system [21].…”

“…Feline or mon key-derived oncornaviruses did not cause this conversion. It is conceivable that cellu lar oncogenes and glucocorticosteroids, or other naturally occurring hormones, can ef fect morphogenetic changes in cells from a variety of normal or diseased human tissues de novo [7,10,11,[19][20][21]26], …”