In Vitro and in Vivo Selection of two Lewis Lung Carcinoma Cell Lines

Morphological Characterization of Lewis Lung Carcinoma (3LL). A Light and Electron Microscopic Study

Primary tumor and its metastases of subcutaneously injected Lewis lung carcinoma (3LL) of the mouse were examined by light and electron microscopy. Although the optical appearance, in both cases, was of a indiffentiated carcinoma, the ultrastructural observation showed characteristic intracyto-plasmic myelinoid bodies similar to those seen in type II pneumocytes in normal lung. These findings suggest that Lewis lung carcinoma is a carcinoma derived from granular pneumocytes equivalent to human alveolar cell carcinoma. The histological and embryological aspects ot type II pneumocytes that could explain the histogenesis of this tumor are discussed.

Cell Proliferation Kinetics of the Intramuscularly Implanted Lewis Lung Carcinoma

The growth kinetics of the Lewis lung carcinoma tumor was studied. The main proliferative parameters of an early stage of the growth (8th day after tumor implantation) were derived from the analysis of the growth curve and the fraction of labeled mitoses (FLM curve). The occurrence of proliferative changes due to the transplantation was confirmed. The main variations observed concern a shortening of the cell cycle time, a prolongation of the S phase duration and an increase in cell loss. A critical analysis of the results of this preliminary study is reported.

Effects of prolonged treatment with decarbazine on tumor metastatic potential in mice bearing Lewis lung carcinoma

The effects of decarbazine on tumour growth and metastatic dissemination upon treatment protracted for 10 tumour transplant generations were examined in mice bearing Lewis lung carcinoma. Primary tumour growth is unaffected by the drug, independently from the duration of the treatment. In contrast, dacarbazine significantly inhibits the formation of lung metastasis. The proportion of mice with metastasis decreases for an increasing number of transplant generations of treatment, and after 10 transplant generations of treatment metastatic capacity is completely lost in immunocompetent mice. The reduction in metastatic potential is relatively stable, being retained for three successive transplant generations without treatment. The metastatic potential of treated tumours in immunosuppressed mice is substantially similar to that in immunocompetent hosts, indicating that chemical xenogenization of tumour cells does not occur as reported for transplantable mouse leukaemias. The results obtained using clonally selected tumour lines with different metastatic potential rule out the selection by dacarbazine of tumour cell sublines with reduced metastatic potential as the mechanism of the drug's action. Upon prolonged treatment, dacarbazine appears to cause a rather stable and dramatic loss in metastatic potential, not accompanied by resistance, which might be attributed to genotypic alteration(s) of tumour cells, and which might participate into the clinical effects of the drug.

Antineoplastic action of p-(3-methyl-1-triazeno)benzoic acid potassium salt, a monomethyl derivative of the antimetastatic compound DM-COOK

The antitumor and antimetastatic effects of p-(3-methyl-1-triazeno)benzoic acid potassium salt (MM-COOK) as compared with those of the parent 3,3-dimethyl derivative (DM-COOK) were examined using Lewis lung carcinoma, MCa mammary carcinoma of the CBA mouse and TLX5 lymphoma. Similarly to DM-COOK, MM-COOK reduces metastasis formation and significantly prolongs the survival of mice bearing the Lewis lung carcinoma when given at a daily dose corresponding to one-half that of DM-COOK. Unlike DM-COOK, MM-COOK exhibits significant cytotoxicity to metastatic foci and pronounced inhibition of primary tumor development. MM-COOK also causes cytotoxic effects on TLX5 lymphoma cell growing in the peritoneal cavity, even when used at low doses. The antimetastatic effects observed in mice bearing MCa mammary carcinoma are unrelated to the inhibition of primary tumor growth and are more likely due to the selection of clones endowed with lower metastatic ability. It appears that MM-COOK exhibits the same antineoplastic activity as DM-COOK, but the former does so at a lower daily dose and produces interesting cytotoxic effects other than those reflecting its antimetastatic properties. It thus seems to be a valid alternative to DM-COOK, in view of the possible introduction of newer aryltriazenes into clinical use.

Stimulation of tumor cell growth in vitro by a monoclonal antibody to a tumor specific protein (TSP-180) present on the cell surface of 3LL cells

Proliferation capacity and MHC class I antigen expression of two Lewis lung carcinoma (3LL) metastatic variants (C87, BC215) grown under defined experimental conditions (serum-free defined medium or 10 per cent serum) have been studied following exposure to MoAb 135-13C which recognizes on these cells a tumor surface protein of 180,000 daltons (TSP-180). The results of this study indicate that the high metastatic clone (C87) binds higher amounts of MoAb to TSP-180 and Db antigens than does the low metastatic one (BC215), while both clones express very low amounts of Kb antigens. 3LL clones grown in 10 per cent serum or adapted in serum-free, defined medium show the same metastatic phenotype and MHC class I antigen expression, but when grown in defined medium exhibit increased capacity to bind MoAb 135-13C. However, the relative binding rate of 3LL clones grown in 10 per cent serum or in defined medium is unchanged: the high metastatic clone always showing higher capacity to bind MoAb to TSP-180. Furthermore, comparison of EGF binding sites on the cell surface of 3LL clones, grown in different culture conditions, demonstrates that the C87 clone binds higher amounts of labelled EGF and that this amount increases in serum-free defined medium, exactly as reported for TSP-180. In addition, competition experiments demonstrated that MoAb 135-13C does not compete for EGF binding sites on 3LL cell surface. Studies on cell proliferation following exposure to MoAb 135-13C, revealed that the low metastatic clone (BC215) is more actively stimulated than the high metastatic one. Moreover, similar data were obtained after exposure of 3LL clones to physiological amounts of different growth factors (i.e. EGF, MSA, insulin). Analysis of MHC class I antigen expression following exposure to MoAb 135-13C indicated that MoAb 135-13C induces on the cell surface of the C87 clone a transient low modulation of Db antigens. These results suggest that 3LL cells endowed with lower metastatic potential are more dependent on the microenvironmental conditions than the high metastasizing ones, and that MoAb 135-13C binding to 3LL cell surface stimulates proliferation as reported for several known growth factors.

Antimetastatic action of orally administered lysozyme in mice bearing Lewis lung carcinoma

The pharmacological activity of orally administered lysozyme, for the control of the growth of solid tumor metastases, was examined in mice bearing Lewis lung carcinoma. Groups of at least 10 tumor-bearing mice, fed daily for three consecutive weeks from subcutaneous tumor implantation with lysozyme, prepared from hen egg-white, had a pronounced reduction of the weight of their metastatic tumor to 25-50 per cent of controls within a wide range of doses (25-200 mg/kg/day). The antimetastatic effect was not related to the length of the treatment schedule employed; a short course of 7 days, given on days 1-7 after tumor implantation, proved equally active. The inhibition of the formation of lung metastases, in mice treated with lysozyme prior to tumor inoculation, lasts for at least 2 weeks after discontinuation of treatment, indicating that the antimetastatic activity observed is not associated with cytotoxic activity of the lysozyme, and is probably mediated by the elicitation of host responses. The examination of the therapeutic potential of the antimetastatic action of lysozyme supplied through the usual diet indicates that this treatment synergizes with the antitumor effects of cisplatin, given to mice after surgical removal of the primary tumor, causing a statistically significant prolongation of the survival time of the animals as compared with chemotherapy alone.

MHC antigens expressed on 3LL metastatic variants: correlation with the expression of a TSP-180 protein

In attempts to correlate metastatic potential with specific properties of tumor cells, homogeneous subpopulations, which are endowed with low or high metastatic potential, have been selected from Lewis lung carcinoma (3LL). In particular, since cell surface constituents are possibly involved in the metastatic process, changes in antigen expression have been correlated with the metastatic potential of 3LL variants. In this view, we quantitated the expression of MHC (Db,Kb) antigens and of a tumor specific protein (TSP) identified by the monoclonal antibody (MoAb) 135-13C on some "in vitro" and "in vivo" variants of 3LL. The MoAb 135-13C was found to recognize a TSP-180 protein that appears on the cell surface of several murine carcinomas, but is not detected on normal cells in culture. Studies of the MHC expression on these variants, by the use of the indirect immunofluorescent staining or the direct binding of the MoAb to H-2Db (28-14-8) and the MoAb to H-2Kb (28-13-3), demonstrate that "in vivo" and "in vitro" 3LL variants which, are endowed with a higher metastatic potential, express on the cell surface a higher amount of the Db antigen. By contrast, all the 3LL lines have few cells recognized by the MoAb to H-2Kb and express low amounts of this antigen on the cell surface. The direct binding to different tumor lines and the analysis of the immunoprecipitates from the cell lysates by the use of the MoAb 135-13C demonstrate that the TSP-180 protein is highly expressed on 3LL cells which possess high capacity to metastasize to the lung. The variations induced in 3LL metastatic phenotype by the injection of the variant lines in allogeneic mice (Balb/c, C3HeB:H-2d,H-2k, respectively) or after treatment with the specific MoAb 135-13C have, also, been studied. An attempt was made to correlate the changes in 3LL metastatic phenotype with the expression of the TSP-180 protein and of the MHC antigens. We conclude that a high expression on the cell surface of the Db antigen and of the TSP-180 protein, is associated with a high malignant phenotype of 3LL tumor cells.

Morphological analysis of metastatic potential and antimetastatic drug effects in mice bearing two lines of Lewis lung carcinoma

Two lines of Lewis lung carcinoma with a different potential to metastasize spontaneously to the lungs have been examined for their cytological and histological characteristics. Metastatic potential appears to be related with parenchymal organization of the primary tumours, since large haemorrhagic areas containing detached tumour cells and the absence of endothelialized capillaries are observed only in the line with high metastatic potential. At the same time, the cytological characteristics of the cells of the two tumour lines are similar, and do not seem to be related with metastatic potential. After treatment with the selective antimetastatic drugs ICRF-159 and DM-COOK, and with DTIC, the histological appearance of the line with high metastatic potential becomes similar to that of the line with low metastatic potential. These data seem to indicate that the early phases of tumour spread occurring in the primary tumour are of relevance for metastatic potential and control by antimetastatic drugs, and suggest that for DTIC such antimetastatic action may participate to its clinical antitumour effects.

Changes of phenotypic characteristics of variants derived from Lewis lung carcinoma during long-term in vitro growth

Two cultured cell clones derived from Lewis lung carcinoma (3LL), which have been shown to differ in their metastatic potential, were studied for their phenotypic stability in vitro. Several growth properties (lag-phase duration, doubling time, saturation density, cell shedding, plating efficiency) have been monitored for more than three years. The ability to induce primary tumors and metastasis, together with the response of cultured cells to adriamycin and bleomycin, have also been evaluated over the same period. The results show that the pattern of metastatic heterogeneity of the two clones is maintained during the serial passages in vitro, although the most actively metastatic clone (C108) displayed a reduced lung colony-forming ability at late passages. Furthermore, both clones exhibited an increasing sensitivity to adriamycin, while no changes were observed in the response to bleomycin. The present data suggest a phenotypic instability of tumor clones adapted to tissue culture conditions and, in particular, that the inherent chemosensitivity of tumor cells may change during long-term culture.

Effects of DTIC, DM-COOK and ICRF-159 on the number of circulating Lewis lung carcinoma cells detected by flow cytometry

Circulating tumor cells can be detected by means of flow cytometry in the blood of mice bearing i.m. Lewis lung carcinoma. This technique can be applied in the case of aneuploid tumors and does not require either concentration of nucleated cells or other processing of the blood samples. It offers the advantages of simplicity and speed and allows quantitative measurement of the number of circulating tumor cells. It can be applied to the study of the effects of drug treatment on the number of circulating tumor cells, for those drugs which do not cause alterations in the nuclear DNA content of normal diploid blood cells. The number of circulating tumor cells determined by flow cytometry is markedly reduced by treatment with ICRF-159, by dimethyltriazene DM-COOK, and also by its clinically used analog, DTIC.

DNA content distribution of in vivo and in vitro lines of Lewis lung carcinoma

The kinetic features of Lewis lung carcinoma (3LL) and of two in vitro and two in vivo derivative lines were studied by flow cytometry. The in vitro lines C108 and BC215 show the same tetraploid DNA content and a very similar cell cycle structure, characterized by a prevalent S fraction. Also, the in vivo lines, the original 3LL and M1087, show a tetraploid DNA content, while the BM21548 is characterized by a hyperdiploid DNA mode and a broader distribution of DNA values. No difference in the modal DNA value is found between each primary tumor and the corresponding lung metastases for all the in vivo lines. In addition, an increase in the G1 component corresponding to a decrease in the S fraction is observed during the tumor growth. These kinetic features were related to some malignant properties of 3LL lines, such as growth pattern and metastatic potential. Our findings indicate that a direct correlation is not always possible to establish.