T. Sugihara et al., ENHANCED EXPRESSION OF MULTIPLE FORMS OF VEGF IS ASSOCIATED WITH SPONTANEOUS IMMORTALIZATION OF MURINE FIBROBLASTS, Biochimica et biophysica acta. Molecular cell research, 1224(3), 1994, pp. 365-370
The mechanism(s) involved in immortalization that constitute the first
step during malignant transformation has been the subject of our inte
rest. By the use of spontaneously immortalized mouse embryonic fibrobl
asts we have earlier identified two stages of immortalization which ar
e characterized by growth characterisitics of the cells, their conditi
oned medium and the protein markers such as p53, p81 and mortalin (Kau
l et al. (1994) Biochim. Biophys. Acta, in press). The present study w
as planned to purify the mitogenic factors from the conditioned medium
of stage II cells. Sequential purification by chromatography followed
by peptide sequencing has characterized one of these as vascular endo
thelial growth factor (VEGF). Further analysis by RT-PCR suggests that
the spontaneously immortalized stage II fibroblasts have enhanced syn
thesis and secretion of VEGF as compared to their mortal parent cells.
Expression of a novel 304 bp long form of VEGF is identified in immor
tal fibroblasts in addition to the three known alternatively spliced f
orms. The study points to the involvement of VEGF function during spon
taneonus immortalization of mouse, embryonic fibroblasts.