Progressive abrogation of TGF-beta 1 and EGF growth control is associated with tumour progression in ras-transfected human keratinocytes.
This study examined the response of human keratinocytes in different stages of transformation to exogenous TGF-beta 1 and EGF as well as their receptor and growth-factor expression. Cells of the spontaneously immortalized HaCaT cell line and c-Ha-ras transfected clones (I-6, I-7, II-3, II-4) exhibited different tumorigenic potentials when transplanted to athymic mice. HaCaT- and I-6 cells were non-tumorigenic, I-7 cells formed persisting epidermal cysts (benign tumours) and II-3 and II-4 cells developed into invasive squamous-cell carcinomas. TGF-beta 1 inhibited thymidine uptake in a dose-dependent manner, a progressive decrease in response being associated with an increasing malignant potential (HaCaT greater than I-6 greater than I-7 = II-4). HaCaT-cells and ras-clones expressed TGF-beta 1 mRNA at similar levels, but cells of increasing malignant potential secreted markedly less receptor-binding TGF-beta (HaCaT greater than I-6 = I-7 greater than II-3 greater than II-4) into the culture medium. Whilst ras-transfected cells expressed fewer TGF-beta receptors than HaCaT cells, there was little difference between TGF-beta receptor number or affinity between the 4 transfected cell clones. The same was true for the TGF-beta receptor types, but Type-II receptors were expressed at lower levels by the malignant clones II-3 and II-4. When HaCaT and ras-transfected cells were investigated for their response to exogenous EGF, cells were refractory (I-7, II-4), partially stimulated (I-6) or fully stimulated (HaCaT). Cells with increasing malignant potential produced increasing amounts of endogenous TGF-alpha (II-4 = II-3 greater than I-7 = I-6 greater than HaCaT). All tumorigenic ras clones expressed higher mRNA levels than HaCaT-cells. Ras-transfected clones expressed fewer high- and low-affinity EGF receptors than HaCaT cells with a tendency toward increased numbers of high-affinity EGF receptors associated with increasing malignant potential (II-4 = II-3 greater than I-7 greater than I-6) but these changes were associated with a progressive decrease in receptor affinity. The results indicate that tumour progression in human epidermal keratinocytes transfected with c-Ha-ras is associated with a progressive abrogation of TGF-beta 1 and EGF growth control. They suggest that the increased autonomous growth potential associated with advanced stages of epithelial tumour progression can be defined more closely using a cellular profile of TGF-beta and EGF.
Game
S M
SM
Department of Oral Medicine, Surgery and Pathology, University of Bristol, Bristol Dental Hospital and School, UK.
Huelsen
A
A
Patel
V
V
Donnelly
M
M
Yeudall
W A
WA
Stone
A
A
Fusenig
N E
NE
Prime
S S
SS
D002455:Cell Division / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000378:metabolism / Q000473:pathology*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000032:analysis; D011905:Genes, ras; D006801:Humans; D015603:Keratinocytes / Q000473:pathology*; D011956:Receptors, Cell Surface / Q000032:analysis; D018125:Receptors, Transforming Growth Factor beta; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000494:pharmacology*
D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D016211:Transforming Growth Factor alpha; D016212:Transforming Growth Factor beta; D004815:Epidermal Growth Factor; D066246:ErbB Receptors