Mj. Donnelly et al., AUTOCRINE PRODUCTION OF TGF-ALPHA AND TGF-BETA DURING TUMOR PROGRESSION OF RAT ORAL KERATINOCYTES, Carcinogenesis, 14(5), 1993, pp. 981-985
This study describes a new technique to separate transforming growth f
actor-alpha (TGF-alpha) and transforming growth factor-beta (TGF-beta)
from culture supernatants using ion exchange chromatography; assays o
f competitive inhibition of ligand binding were used to quantify the a
mount of growth factor. The method was simple, inexpensive and did not
require large volumes of culture medium. The autocrine production of
TGF-alpha and TGF-beta was examined in oral keratinocyte cell lines de
rived from the palatal and lingual mucosa of rats painted with the car
cinogen 4-nitroquinoline N-oxide (4NQO). Escape from cellular senescen
ce (immortality) was associated with a marked increase in TGF-alpha pr
oduction (cell line R2P) but tumour progression, as reflected by the d
evelopment of anchorage independence in agarose gels and tumorigenicit
y in athymic mice, did not result in a consistent increase or decrease
of TGF-alpha production compared to normals. Four cell lines (R8AP, R
1T, R3T, R1P), with different functional cellular phenotypes, produced
two to three times more TGF-alpha than normals. TGF-alpha production
was inversely correlated to epidermal growth factor cell surface recep
tor expression. The autocrine production of TGF-beta was variable with
the majority of cell lines producing markedly little TGF-beta; three
cell lines (R4T, R8BP, R9T) produced more TGF-beta than normals. The p
roduction of TGF-beta was unrelated to tumour progression, the express
ion of TGF-beta cell surface receptors or TGF-alpha production. The re
sults indicate that the autocrine production of TGF-alpha and TGF-beta
are not accurate markers of tumour progression in the rat 4NQO model
of oral carcinogenesis.