MORHOLOGICAL AND FUNCTIONAL HETEROGENEITY OF RAT ASCITIC HEPATOMA ZAJDELA CELLS
I. I. Tiuriaeva,1 N. A. Filatova, Yu. M. Rozanov, S. Yu. Demin, G. I. Blinova, V. A. Ivanov
Institute of Cytology RAS, St. Petersburg;
1 e-mail: tii@mail.cytspb.rssi.ru
This work is devoted to the study of molecular and cellular mechanisms of disdifferentiation during neoplastic
transformation of cells by investigating the malignant tumor cell heterogeneity. We have revealed two cell fractions
of hepatoma Zajdela which differ in patterns of growth in primary culture. The cells of one fraction were attached to
the culture plastic and grew in a monolayer (S-fraction), whereas cells of another fraction floated in the culture medium
(F-fraction). Using method of lifetime supervision of primary culture cells (1—2 passages) at the limit of the resolving
power of DIC-microscopy it has been revealed, that both fractions contain cells of several types. Some of
them were specific for one of the fractions, and others were found in both fractions, but their frequencies differed. It
has been shown by the same method, that long separate cultivation of these fractions in vitro (more than 50 passage)
change both cellular structure and the initial ratio of different types of cells in both fractions. According to DNA flow
cytometry, the cells of both fractions were hypotetraploid and had insignificant differences in DNA contents. After
adaptation to in vitro conditions, S-fraction cells raised their proliferative activity in comparison with the F-fraction
cells, and after long cultivation showed 2.3 times higher DNA content. Greater amount of cell surface laminin, a hepatocellular
carcinoma marker, was observed on F-fraction cells than on S-fraction cells. Interfractional distinctions
were confirmed also by immunologic assessment of hepatoma cells resistance to natural killer lyses: the sensitivity of
S-fraction cells in primary culture was 2.4 times higher than F-fraction cells sensitivity, and, after long cultivation,
F-fraction cells became practically resistant to cytotoxic action of natural killers. Based on the data obtained, the
most probable paths of cell disdifferentiation during hepatoma Zajdela formation and during long cultivation of
this tumor cells in vitro are discussed.
Key words: tumor cell fractions, DNA flow cytometry, tumor heterogeneity, natural killer, hepatoma Zajdela
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