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It is well known that artificial increase in expression of growth factors and their receptors can lead to tumorigenic transformation of cells. Additionally, multiple data on the increased expression of growth factors in many human and animal tumorigenic cells have been published. Nevertheless description of the functional role of endogenous growth factors in maintenance of tumorigenic phenotype remains obscure. Previously, we described a new model for studying neoplastic transformation and dormant metastasis. This model consists of cognate tumorigenic and nontumorigenic cell clones, the latter being obtained as a result of spontaneous reversion of tumorigenic ones. All revertant clones demonstrate the three well known features of normal cells: monolayer growth on a plastic, incapability to grow in soft agar with regular culture media with 10% FCS, and incapability to form tumors in syngeneic animals. Using RT-PCR, we measured expression ratios of main growth factors, commonly believed to be associated with malignization, in tumorigenic and revertant clones of our model. For some of these clones, we also measured an activity of growth factors in conditioned media. The data obtained argue that the levels of growth factor expression, measured by both the methods, are distributed between tumorigenic and revertant clones in a sporadic manner and do not correlate with cell tumorigenicity. Thus, our experimental observations enable us to consider the variability of growth factor expression as insignificant events in the reversion of tumorigenic cells to a nontumorigenic phenotype.

In the present paper we have shown that JB6 and PDV murine skin carcinoma cells, as well as previously described sarcoma B6-4 cells, can revert to a nontumor phenotype. Revertant carcinoma clones could not grow in soft agar conditions and like sarcoma revertants acquired dependence on peptide growth factors, and exhibited a reduced expression of c-jun. Spontaneous revertants were shown to be instable. They could revert back to a transformed phenotype in 1-5 months of in vitro passaging. Being inoculated in syngeneic animals, these transformed cells show a recurrence in 2-5 months, similar to that of a dormant metastasis. Thus, dormant revertant cells are believed to be included in many tumors of different origin. So, spontaneous reversions of tumor cells may play an important role in the dormant metastatic process. The cause of these frequent spontaneous transient reversions and revertant instability appears to be of epigenetic nature. Causes and mechanisms of cell transformations and reversions remain to be clarified.

Regulation of c-fos expression in mice sarcoma cell lines CBA and C3H was investigated. Each of the cell lines was represented by a pair of clones: the tumorigenic and the one, which was produced from it by cloning. It was found, that c-fos expression in cells of the pseudonormal phenotype was similar to that in the normal fibroblasts. Experiments with cells reverted to pseudonormal phenotype transfected transiently or permanently with an indicator plasmid fos-cat have shown, that a 600 bp sequence of the c-fos promotor including the TATA site, provides the expression level of the chloramphenicol acetyltransferase, correlating with the level of the c-fos mRNA expression. In the tumorigenic cells, permanent high activity of the cat gene expression was observed which was comparable to that in the normal fibroblasts stimulated by the embrionic serum or TPA. Activity of the transcription factors interacting with regulatory elements SRE, DSE, TRE did not correlate with the c-fos expression level in all the cells.

Karyological analysis of 6 cell lines with distinct tumorigenic properties of mouse strains C3H/He and CBA/Ca has been carried out using differential chromosome staining. All the cell lines are characterized by a decreased number of copies of normal chromosome 7, the increased number of normal copies of chromosome 10 being specific of the cell lines with intermediate tumorigenicity. Cell lines with maximum tumorigenicity differed from all other lines by the increased number of copies of chromosome 5 and by the decreased number of copies of chromosome 6. A wide independent variability was observed in the number of chromosomes and of several types of abnormal chromosomes throughout the neoplastic evolution of cells, to begin from the early immortal passages. But the proportion of normal chromosomes per cell in the studied lines revealed relatively stable values. The potential phenotypical heterogenicity of the lines with maximum tumorigenicity, expressed in their clonal progeny, was associated with the instability in the number of chromosome 15 copies in cells of these lines. It is concluded that multiple genetic events are required in the spontaneous neoplastic evolution of fibroblasts, and only specific traits of the karyotypic instability, associated with the variability of the number of copies of specific chromosomes, may constitute the genetic basis for the above process.

Karyological analysis of 6 lines with distinct tumorigenic properties of mouse strains C3H/He and C57BL/6 has been carried out using a differential staining of chromosomes. The number of normal copies of chromosomes varied in all the investigated cell lines. The more and the less stable chromosomes different from line to line. All the cell lines were characterized by decreased numbers of copies of normal chromosome 7; a decreased number of normal copies of chromosome 2 and 16 was detected in the course of the cell spontaneous neoplastic evolution. The decreased number of normal copies of chromosomes 8, 12 and X, and the increased number of normal copies of chromosome 10 were specific of the cell lines with intermediate tumorigenicity. The maximum tumorigenic cell lines differed from all other lines by increased numbers of copies of chromosomes 4 and 5, and by a decrease in copy number of chromosome 6. The data obtained are discussed in terms of the search of the regularity of karyotypic changes in the course of the cell neoplastic evolution.

A degree of destruction of tumour cells after their inoculation to a syngenic recipient correlates positively with sensitivity to the lytic effect of macrophages. A clear-cut participation of macrophages in elimination of tumours cells can be detected 8 h after their inoculation.

Syngeneic mammary gland tumor (MMT-1) grew slower in non-factor C3H/f (MTV-L) mice than in wirus-positive C3H/He (MTV-S) mice. The immunization of mice with tumor (MMT-1), inoculated and later excised, revealed a higher immune reactivity in the mice of the non-factor substrain. In studying the dynamics of the cytotoxic activity of lymphocytes in regional lymph nodes cytotoxically active lymphocytes were found to appear in C3H/f mice on day 6 after the inoculation of tumor (MMT-1), while the areactive state of lymphocytes was observed in C3H/He mice on days 3 and 24 and in C3H/f mice on day 24 after the inoculation of tumor (MMT-1). Spleen lymphocytes in C3H/f mice had no cytotoxic effect on tumor cells.

Three cell cultures of C3H mouse strain--L, MMT1 and embryonic fibroblasts have different sensitivity to cytolytic action of allogeneic antiserum and to immune lymphocyte action. A sensitivity to cytolytic action of antiserum for these cultures is correlated with the amount of corresponding transplantation antigens. A sensitivity to cytolytic action of immune allogeneic lymphocytes is correlated with the amount of corresponding antigens as well as cell with properties determining the level of lymphocyte sorption on them.

The essential moments of the computer algorithms - a construction of pedigree patterns and determination of inbreeding coefficients - are described. The main attention is given to the field material prossesing for the computer system. The common program is composed to three subprograms: pedigree construction, F estimation and evaluation of information quantity concerning the ancestors. The principal algorithms of the pedigree subprogram is based on computations of a parents computer adress from the proband's code. Such a run is repeated from generation to generation, until the information of ancestors comees to zero. Common ancestors for Wright's inbreeding estimation have been found by sorting out and comparison of husband's and wife's ancestors. The inbreeding coefficient has been formed as the kinship coefficient of parents.

Tumour cells were shown to secrete substances stimulating macrophage migration in vitro and also those depressing the cytopathogenic action of immune lymphocytes in vitro. Embryo fibroblasts (examined in paralled as nontumour cells) secreted as did tumour cells, substances stimulating the macrophage migration, but not substances capable of depressing the cytopathogenic action of immune lymphocytes. L-cells secreted substances inhibiting macrophage migration, but failed to secrete substances depressing the cytopathogenic action of immune lymphocytes.

Some tumors of no mammary tissue origin (sarcoma, hepatoma) grew more effectively in MTV-free mice (C3Hf) as compared with MTV-infected mice (C3H/He), whereas the tumors of mammary gland origin grew more rapidly in the latter ones. It has been shown that C3H/He mice develop a stronger specific immune reaction against hepatoma 22a cells than do C3H/f mice and that the animals of MTV-bearing subline exhibit a higher natural killer activity against these cells.

Immunogenicity of 11 3-methylcholanthrene-induced tumours has been tested in vitro, which was a necessary step in constructing a complex characteristic of cell resistance to the host immune reactions. Such a complex estimate is shown to be useful for predicting the extreme tumourigenicity variants in vivo.

Sarcoma was induced in C57BL/6 mice with 20-methylcholanthrene. The sarcoma cells were found to be heterogeneous in their transplantability. The study of 9 clones distinct in this property has shown that heterogeneous transplantability was due to different susceptibility to lytic action of macrophages.

The expression of three phenotypic markers of transformation in vitro, i.e. serum dependence, contact inhibition and anchorage dependence of growth has been investigated using the lines of mouse cells obtained from spontaneously in vitro transformed embryonal fibroblasts (three stages of a continuous passage in vitro being considered) and from induced tumours. The results obtained indicate that in the cell lines arising spontaneously in the continuous passage in vitro the origin of the transformation features can be observed. Anchorage independence demonstrates not high (r = 0.69) but much better correlation with tumourigenicity than other studied markers.

Changes in growth characteristics (the growth in a mat of normal cells, contact inhibition of division, growth-substrate dependence, dependence on the serum growth factors) and tumourigenicity were compared in 6 cells lines of mice and rats during their in vitro and in vivo long passages. All these factors progressed independently of a tumourigenicity increase, i.e. they obeyed the Fould principle. The trait responsible for the cell capacity to proliferate on a layer of normal cells proved to be the most correct one relative to tumourigenicity prediction.

7 continuous cell lines with different degrees of malignancy were obtained from cultures of embryo fibroblasts of 4 strains of mice. Three of them were selected in vivo for enhanced malignancy. A study of regularities of changes in immunologic and some cytologic characteristics of these cells in the processes of transformation and malignization has been started. The data are presented that in these processes the density of H-2 antigens in embryo fibroblasts many vary significantly in both directions. These alterations are stochastic and do not depend on transformation or malignization of cells. It is also shown that the sensitivity of the cells under study to the complement lytic action may significantly vary, and does not always correlate with the density of antigens which are the targets of the complement lytic action.

Expression of the main structural proteins of mammary gland cancer virus, gp52 and p27, was studied with the immune sera to these proteins in homogenates of tumors from mice of low and high cancer lines. Protein gp52 was found only in tumors of mice-carriers of MTV-S. In a fraction of purified type A particles from the cytoplasm of mammary gland cancer no gp52 was found, but with the antiserum to p27 this fraction reacted by a line identical to that with the antigen from C2HF mouse tumor.

Data are provided on the development of tumorigenicity in cells of 6 independently produced lines of mouse and rat embryonic fibroblasts during their prolonged passage in vitro. The data on the development of lysis of these cells by macrophages and activated lymphocytes during the same passage indicate that enhanced cell lysis of cells by natural effectors and, hence, cell recognition by them may be regarded as an obligatory manifestation of cell malignization.

NK lymphocytes destroyed target cells contaminated with Mycoplasma to a greater extent as compared with normal cells. The mechanism of that phenomenon is based on the production into the environment by effector lymphocytes cocultivated with contaminated cells of high quantity of mycoplasma that has a non-specific cytolytic effect.

Malignant LS cells obtained from benign L cells by selection retained their immunogenicity in syngeneic recipients. Nevertheless, such selection resulted in a partial change in their antigenic structure, which was manifested by the fact that only partial cross reactivity existed between L and LS cells on the level of both humoral and cellular immunity. The preliminary inoculation of L cells induced statistically significant lymphocytic reaction in the animals against LS cells, sufficient to protect 30% of mice inoculated with these cells.

The mouse CBA sarcoma characterized by great cellular heterogeneity was obtained from spontaneously in vitro transformed embryonic fibroblasts. The clones of the given sarcoma distinct in this property were studied. It was shown that the only feature limiting the growth of clones characterized by weak tumorigenicity was contact inhibition of cellular growth. This property is easily estimated by the in vitro methods.

LS cells, the malignant subline of benign L cells, were obtained from L cells by selection carried out by means of their cultivation in the abdominal cavity of allogenic mice. When inoculated subcutaneously in a dose of 1 x 10(6) into the back, LS cells took and progressively grew in 70% of syngeneic animals. The preliminary immunization with L cells protected 30% of mice inoculated subsequently with L cells.

Cytotoxic antibodies against mouse mammary tumour cells, L-cells and hepatoma 22a cells have been found in the serum of C3H/f and C3H/He mice over 8 months of age. Analogues antibodies were found in the serum of young and old BALB/c mice, but not in C57BL/6 mice. The cytotoxic activity of antimammary tumour cell serum has been completely abolished by its depletion by renal tissue of syngeneic and allogeneic animals.

The intensity of the immune response of cells in mice to strong transplantation antigens of the H-2 complex can depend on the histological type of cells taken for immunization. Splenic cells of C3H mice immunized the cells of BALB/c line better that cells of the non-lymphoid origin taken from the same donor. A reverse situation was observed in case of immunization by the same cells of the lines C57Bl/6 and A/He. It was shown by the analysis of the lines of the first generation derived from the crosses between the 3 lines studied and also by the analysis of these characters in mice born from the backcross, that these characters do not exhibit a simple Mendelian segregation.

The previous report contained the information on obtaining in vitro continuous cell lines of embryonic fibroblasts of mice of 4 genotypes, including C3H. In this paper, data on the degree of lysis of some derivatives of FC3H3 cells by natural killers and macrophages are given. It was shown that normal cells were not lysed by these effectors unlike cells which overcame Hayflick's limit and got minimum malignancy in vitro. However, it was established that the in vivo selection of cells for high tumorigenicity resulted in the formation of tumor cells resistant to lymphocytes--natural killers and macrophages.

Computer program "RODAN-1" is used for inbreeding coefficient estimation. The population studied consists of two communities of 5 villages. 385 marriages were computed. The coefficient of inbreeding is 0.00145 for pedigree for rural Russian population (the Arkhangelsk region). The inverse dependence between a village size and corresponding data of inbreeding coefficient is suggested. An attempt was undertaken to estimate the genealogical information value for each pedigree and average information value for a village.

The malignant subline of L cells did not differ from the initial benign subline in such immunological parameters as immunogenicity, ability for modigying immunological reactions by their metabolic products, sensitivity to the lyzing action of the complement, ability for surface adsorption of lymphocytes. The cells of the malignant subline were somewhat less sensitive to the lyzing action of T lymphocytes than the cells of the initial subline.

Complement-dependent cytotoxic antibodies against the cells of mammary tumor MMTI appeared in the blood of C3H/He and C3Hf mice at the terminal stage of tumor growth; at the same time the mice of the above-mentioned substrains showed no difference in the degree of reaction. The level of natural cytotoxic antibodies against MMTI tumor cells detected in old C3H/He and C3Hf mice significantly exceeded their level in young mice affected with tumor; however, MMTI tumor cells grew equally fast in both old and young animals. The sera of mice affected with tumor had a weak cytolytic activity against the cells of hepatoma 22a and did not affect L cells and embryonal fibroblasts. The sera were partially exhasted by spleen and renal tissues, as well as the cells of spontaneous mammary tumor obtained from syngeneic animals and were not exhausted by allogenic cells infected with Rauscher murine leukemia virus.

The paper deals with the effect of assortative matings on some parameters of population structure. To solve this problem, two rural populations near Archangelsk (river Peosa region) were used. Some genetic and demographic characteristics of these populations were described in previous publications. A comparison between random matches through a random number generator and true marriages was made by computer estimation of the spouses kinship coefficients. Significant avoidance of first and second cousins marriages in real populations was discovered. As a consequence of this avoidance of consanguinity, the effective breeding size of villages is increased twofold. Similar results were obtained by estimation os isonymy.

Immune allogeneic cells of lymph nodes, spleen and peritoneal exudate lyse in vitro dividing and irradiated non-dividing target cells with the same intensity. The number of target cells lysed during the immune attack are more precisely registered in irradiated non-dividing cells.