Lectin-resistant variants of mouse Lewis lung carcinoma cells. I. Selection and in vivo properties

Impaired tumor growth in colony-stimulating factor 1 (CSF-1)-deficient, macrophage-deficient op/op mouse: evidence for a role of CSF-1-dependent macrophages in formation of tumor stroma

Macrophages have been suggested to play a major role in the immune response to cancer. They have also been suggested to stimulate the formation of tumor stroma and to promote tumor vascularization. The availability of the op/op mouse, which has no endogenous colony-stimulating factor 1 (CSF-1) and which possesses a profound macrophage deficiency, provides a new model to verify these notions. Subcutaneous growth of transplantable Lewis lung cancer (LLC) is markedly impaired in the op/op mice compared with normal littermates. Treatment of tumor-bearing op/op mice with human recombinant CSF-1 corrects this impairment. Histological analysis of tumors grown in op/op and normal mice revealed marked differences. Tumors grown in op/op mice display a decreased mitotic index and pronounced necrosis, particularly hemorrhagic. Moreover, particularly in the op/op tumors, peculiar sinusoid-like abortive vessels (not filled with blood) have been observed. These tumors, in contrast to tumors grown in normal mice, are almost deprived of regular arteries and veins. In contrast to tumors grown in normal mice, they exhibit almost no Sirius red-stained collagenous fibers and Gomori silver-stained reticular fibers. Our data suggest that the CSF-1-dependent macrophage subpopulation missing in op/op mice plays a primary role in supporting tumor stroma formation and tumor vascularization in murine LLC tumors.

Expression of PNA-binding sites on specific glycoproteins by human melanoma cells is associated with a high metastatic potential

Lectin-binding patterns of seven human melanoma clones and variants selected from the same parental cell line and differing in their spontaneous metastatic potential in an animal model were compared by flow cytometry and Scatchard analysis. Human melanoma clones and variants with high and low metastatic potential could be distinguished by their peanut agglutinin (PNA)-binding patterns, but not by their wheat germ agglutinin (WGA)-, Ulex europaeus agglutinin I (UEA I)-, and soybean agglutinin (SBA)-binding patterns. Low metastatic clones and variants proved to be made up of single poorly peanut agglutinin-binding cell population (2.20-3.52 x 10(6) sites/cell, Ka = 2.48-2.75 x 10(6) M-1). By contrast, highly metastatic variants were found to be constituted by two cellular subpopulations, exhibiting respectively a moderate 2.62-3.72 x 10(6) sites/cell) and a high peanut agglutinin staining (17.68-18.76 x 10(6) sites/cell). One highly metastatic clone was found to be homogeneously constituted by a single population of cells strongly binding this lectin (18.86 x 10(6) sites/cell) with an association constant of 4.06 +/- 10(6) M-1. Using an EPICS V cytometer, these two subpopulations were sorted from a highly metastatic variant and tested for their metastatic abilities: cells with high PNA binding generated a higher frequency of metastases than did moderately PNA-binding cells. Following treatment with Vibrio cholerae neuraminidase, all cells from all variants and clones were brightly labeled by PNA, collecting in a single peak with similar fluorescence intensities. Electrophoresis of total cellular proteins and subsequent detection with labeled PNA om Western blots show two major PNA-reactive glycoproteins with apparent molecular weights of 140 and 110 kDa (MAGP1 and MAGP2), expressed only in highly metastatic cells, but which can be strongly labeled by PNA in slightly metastatic cells following a treatment with neuraminidase. These results provide evidence that the expression of terminal galactose (beta 1-3)N-acetyl galactosamine structure, positioned on MAGP1 and MAGP2 glycoproteins, is associated with the metastatic potential of human melanoma cells.

Human tumor spontaneous metastasis in immunosuppressed newborn rats. II. Multiple selections of human melanoma metastatic clones and variants

Using a recently developed model of human tumor spontaneous metastasis in immunosuppressed newborn rats, we selected variants with different metastatic abilities from the human melanoma cell line M4Be. We used 4 in vivo selection approaches, by direct serial tumor transplantations or by techniques involving in vitro reculture of the cells recovered from s.c. tumors or lung and lymph-node metastases. In addition, 3 series of clones were derived in vitro from the M4Be cell line, either by limiting-dilution or by cloning in semi-solid agar and harvesting small and large colonies. A considerable amount of heterogeneity in tumorigenicity and metastatic ability was demonstrated among variants and clones following in vivo selections and in vitro cloning. Four main malignant phenotypes were identified among those expressed by the selected cells: poorly tumorigenic and poorly metastatic; poorly tumorigenic and highly metastatic; highly tumorigenic and poorly metastatic; and highly tumorigenic and highly metastatic. However, while malignant phenotype (i.e., tumorigenicity and metastatic ability) did not appear to be grossly influenced by in vitro cloning procedure, it appeared greatly influenced both by the in vivo selection procedure (direct transplantations or use of in vitro culture between the in vivo passages) and by the origin of the cells under selection (s.c. tumor or metastases). Our study provided us with a large panel of variants and clones with varying metastatic abilities, which represent a model of human melanoma spontaneous metastasis allowing the study of critical determinants in human tumor metastasis.

Structures of the alpha(1-3)-galactose-containing asparagine-linked glycans of a Lewis lung carcinoma cell subline resistant to Aleuria aurantia agglutinin: elucidation by 1H-NMR spectroscopy

Four bi-antennary glycan fractions of the N-acetyllactosamine-type, derived from a Lewis lung carcinoma (LL2) cell subline resistant to the Aleuria aurantia agglutinin were studied by 400 MHz 1H-NMR spectroscopy. By this method, their antennae were found to be terminated either by alpha(2-3 or 6)-linked N-acetylneuraminic acid or alpha(1-3)-linked galactose residues. The primary structure of glycans of these four glycopeptide or derived oligosaccharide-alditols has been determined in full detail.

Lectin-resistant variants of mouse Lewis lung carcinoma cells. II. Altered glycosylation of membrane glycoproteins

Lectin-resistant variants of mouse Lewis lung carcinoma LL2 cell line, selected with wheat germ agglutinin (WGAR), Ricinus communis agglutinin II (RCA IIR) and Aleuria aurantia agglutinin (AAAR) were studied. Total cellular glycopeptides of the parent LL2 line and of the five lectin-resistant variants were analyzed by gel filtration and affinity chromatography on immobilized concanavalin A and Lens culinaris agglutinin. The results revealed that low-metastatic WGAR and RCA IIR variants possessed less highly branched tri- and tetra-antennary N-acetyllactosaminic type glycans with a simultaneous increase in biantennary N-acetyllactosaminic type, oligomannosidic type or hybrid type glycans, as compared to the parent metastasizing LL2 cell line. These findings imply that cell surface carbohydrate changes may possibly be relevant for metastasis. However, the AAAR variant, which possessed reduced spontaneous metastatic ability after s.c. administration, but increased experimental metastatic ability after i.v. inoculation, exhibited apparently the same glycan pattern than the parent LL2 line. This particular variant is under investigation in order to find specific modification(s) of glycan(s) which could play a specific role in the metastatic process.