| Abstract |
From an already transformed but still low-malignant C57BL mouse cell
population (P4bis line), we selected a highly tumorigenic derivative
(P4bisT line), thus illustrating in vitro a stepwise "malignant
progression" at the cell level. The accentuation of tumor producing
capacities of the P4bisT cells was not due to changes in antigenic
properties, since the shift of tumorigenicity could be demonstrated to a
similar degree in syngeneic as well as in heterologous, immunologically
depressed hosts. The different degrees of malignancy appeared, therefore,
in this model, as an intrinsic property of each type of cells. However,
some cell properties, such as cross antigenicity and a chromosome marker,
were still shared by both P4bis and its P4bisT derivative. Important
differences in morphology and "social behavior" were observed when these
two cell lines were compared in vitro. A particularly marked difference
was observed in the adhesivness of each kind of cells to the substrate and
to sister cells, which was much more pronounced for P4bis cells. This
difference could be evaluated and expressed quantitatively by a checking
system of measuring the extent of common inter-cellular borderlines and
counting of the cytoplasmic borderline crossings. Thus, each cell line
could be precisely characterized by these two indexes of social behavior.
Finally, the important mobility of individual P4bisT cells, easily
detachable and moving freely through the cultures, was observed with the
aid of time-lapse microcinematography. A parallel was drawn between the
important motility of P4bisT cells in vitro and their high invasivness
observed in vivo.
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