Sc. Kaul et al., IDENTIFICATION OF GENETIC EVENTS INVOLVED IN EARLY STEPS OF IMMORTALIZATION OF MOUSE FIBROBLASTS, Biochimica et biophysica acta (G). General subjects, 1201(3), 1994, pp. 389-396
The spontaneously immortalized early passaged fibroblasts from three d
ifferent strains of mouse are observed to represent two distinct stage
s of immortalization. The cells at stage I are characterized by slow g
rowth rate, contact inhibition and requisition of serum factors for th
eir growth and proliferation. Stage II cells are marked by fast, multi
layer growth that is independent of serum supplementation in growth me
dium and by the elevated levels of the two marker proteins, i.e., p53
and p81. The change from cytosolic distribution of mortalin, a senesce
nce inducing protein (J. Biol. Chem. (1993) 268, 6615-6621; 22239-2224
2) to the perinuclear locale is detected as an early event during cell
ular immortalization. Furthermore, the distinct stages could be charac
terized by thermal analysis of intact cells, that to the best of our k
nowledge is employed for the first time for the analysis of cellular m
ortal and immortal phenotypes. The study characterizes at least two di
stinct end points in rodent transformation suggesting that there are m
ultiple routes to immortalization.