[The cells of murine sarcoma PC-103 induced by a polymeric plate secret transforming growth factor alpha]. / Kletki sarkomy PS-103 myshei, indutsirovannoi polimernoi plastinkoi, sekretiruiut transformiruiushchii faktor rosta al'fa.

It was shown previously that cells of sarcoma PS-103 induced in mouse by subcutaneous transplantation of plastic film produce growth-stimulating activity. In this communication clone 3 sb, isolated from sarcoma PS-103, was studied. Growth factor produced by the cells of this clone stimulated proliferation of quasi-normal (3T3, NRK) cells and transformed cells both in monolayer and in semi-solid medium. It was shown by gel filtration chromatography that the main growth-stimulating activity migrated with the protein fraction m.m. 10-15 kDa. The addition of this growth factor to the culture medium significantly (90%) inhibited 125I-EGF (epidermal growth factor) binding by A-431 cells. These data suggest that the growth factor produced by the studied tumor cells is transforming growth factor alpha.

[Effect of the tumor-growth promoter 12-O-tetradecanoylphorbol-13-acetate on the proliferation of different clones of mouse tumor cells in a semiliquid medium]. / Vliianie promotora opukholevogo rosta 12-O-tetradekanoilforbol-13-atsetata na proliferatsiiu razlichnykh klonov opukholevykh kletok myshi v poluzhidkoi srede.

The effect of tumour promoter, 12-0-tetradecanoylphorbol-13-acetate (TPA), on the cloning efficiency of different clones of mouse tumour cells was studied in semi-solid medium. The clones varied in their response to TPA. Inhibition and inherited stimulation of colony-formation efficiency in semi-solid medium was revealed. One clone did not respond to TPA. The influence of environmental factors on the clone structure and tumour progression is discussed.

[Independence from the substrate of multiplication in nonclonal and clonal tumor cell populations]. / Nezavisimost' razmnozheniia ot substrata v neklonirovannoi i klonovoi populiatsiiakh opukholevykh kletok.

Experiments were made with sarcoma PS-103 cells cultured in vitro. The sarcoma was induced by implantation of a plastic plate into CBA mice. Clonal analysis of the cell culture demonstrated that 1) all 3 clones isolated from substrate (SB) grew in 1.2% methyl cellulose (MC) at the same efficiency as parental cells; 2) all 5 clones isolated from MC formed in a semi-solid medium 10-100-fold more colonies than PS-103. During the subcloning of one of PS-103 clones in solid substrate and in MC, it turned out that the majority of MC and SB subclones had the plating efficiency in MC similar to that in PS-103. Apparently, the PS-103 population contains clones with different degrees of anchorage independence.

[Relation between the attachment of cells to a substrate and their proliferative characteristics]. / Sviaz' mezhdu prikrepleniem kletok k substratu i ikh proliferativnymi kharakteristikami.

17 cloned cell lines of transformed mouse fibroblasts were used for the evaluation of a correlation between three traits of malignancy: cloning efficiency in semisolid medium (CE); cell dose inducing tumours in 50% of inoculated animals (TD50); degree of cell attachment to a substrate (RT50--rounding time for 50% of the cells under moderate cooling, 18 degrees C). It is shown that an increase in RT50 (better attachment of the cells to the substrate) is accompanied by a decrease in CE and an increase in TD50 (coefficients of rank correlation p = -0.76 and p = 0.58, respectively). A negative correlation between CE and TD50 was also revealed (p = -0.68). A certain increase in the percentage of cells containing actin filament bundles was found in cell clones better attached to the substrate. Mechanisms of disturbances in proliferation and attachment of malignant cells are discussed.

[Effect of ethylmethane sulfonate on the expression of one of the traits of malignancy by cultured mouse cells]. / Vliianie étilmetansul'fonata na ékspressiiu odnogo iz priznakov malignizatsii kul'tiviruemymi kletkami myshi.

The influence of ethyl methane sulfonate (methane sulfonic acid ethyl esther, EMS) on anchorage independence of tumor cells was studied. Mouse near-diploid spontaneously transformed clonal fibroblasts (CAK-25Agr were used. They were characterized by a stable low cloning efficiency in 1,2% methyl cellulose ((3-5) . 10(-5) per cell seeded into a semi-solid medium). EMS enhanced the quantity of CAK-25Agr colonies grown in methyl cellulose. However, this enhancement was only obtained when correction on the cloning efficiency of the cells in a liquid medium was introduced. Subclones of CAK-25Agr isolated from methyl cellulose were studied for their ability to form colonies in the semi-solid medium. The number of subclones with elevated anchorage independence in cultures treated by a mutagen and in untreated cultures did not differ.

[clonal analysis of the independence of tumor cell multiplication from the substrate]. / Klonal'nyi analiz nezavisimosti razmnozheniia opukholevykh kletok ot substrata.

The clone of near-diploid mouse transformed CAK-25AGr cells is characterized by the stable cloning efficiency in a semi-solid medium (about 10(-5) per cell plated in methylcellulose). It was shown that colonies in the semi-solid medium were formed by rare single cells and did not arise as a result of slow multiplication of all cells in the population. These cells are not genetical variants different from other cells in the culture. This is assumed on the basis of following data. First, the majority of the subclones arising in methylcellulose (9 of 12) retained parental cloning efficiency in the semi-solid medium. Second, all 6 subclones picked from the solid substratum had the ability to form colonies in methylcellulose with the frequency not lower than that of the parental clone. Apparently, the proliferation in methylcellulose of the transformed cells studied is a stochastic process. Each cell in the culture has the ability to initiate a colony in the semi-solid medium with the certain probability. This probability is a heritable characteristic of the cloned cell line. It is possible that this characteristic reflects the norm of reaction of the cells to some environmental factors.