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Cell strains isolated from an established line of SV40-transformed mouse 3T3 cells (SV3T3) showed large variations in the various parameters of transformation, viz. saturation density, serum requirement, contact inhibition of movement and of growth and Concanavalin-A-mediated agglutinability. These cell strains were studied for changes in elution profiles of fucose-labelled surface glycoproteins, using actively growing, untransformed 3T3 cells as controls. A cell strain established from a tumour arising after injection of wild-type SV3T3 cells and SV3T3 cells grown in vivo in diffusion chambers, was similarly studied. Changes in surface glycoproteins were observed only in the tumour-derived cell strain. The results suggest that alterations in surface glycoproteins are associated with the tumorigenic potential of the cells rather than with the transformed phenotype per se.

NIH 3T3 cells were transfected with DNA derived from human bladder carcinoma, colon carcinoma and HL60 promyelocytic leukemia cells. The transfectants were examined for the presence of human oncogenes in relation to tumorigenic potential and composition of surface-located fucosyl glycopeptides by gel filtration, Concanavalin-A-binding and high-performance liquid chromatography. All transfectants, harboring 3 different human cellular ras genes, appeared to be tumorigenic in nude mice and displayed characteristically altered glycopeptides. The surface glycopeptides were consistently changed to higher apparent molecular weight due to enrichment in higher-branched sialic-acid-containing glycopeptides. Similar alterations have been found previously in virally- and chemically-transformed cells in vitro and tumors raised in vivo, and were designated as cancer-related or tumor-associated glycopeptides. Revertants derived from HL60-DNA-induced transfectants, which had lost the transfected human N-ras oncogene, simultaneously lost their tumorigenic potential and expression of cancer-related membrane glycopeptides. In addition, spontaneous transformants, exhibiting morphology and growth patterns indistinguishable from those of tumor-DNA-induced transfectants, neither contained transferred human DNA sequences nor expressed cancer-related glycopeptides. Nevertheless these cells were capable, after prolonged latency periods, of inducing tumors in nude mice. Cells derived from such tumors constantly displayed cancer-related glycopeptides on their surface, suggesting selection of tumorigenic cells from spontaneous transformants during passage in nude mice. In one of these tumors at least, an endogenous mouse ras-gene appeared to be activated. The results indicate a close correlation between the presence of activated ras-oncogenes in the genome of the transfected cells, the tumorigenic potential of these cells and the expression of surface-located cancer-related glycopeptides. The data suggest that functions provided by human ras-oncogenes contribute to the alteration of membrane glycopeptides on tumor cells.

It has previously been shown that differential fucose labelling of many normal and homologous tumor cells, followed by proteolytic release and degradation, yields glycopeptides which upon gel filtration shown an increase in fast-eluting glycopeptides for the tumor cells. This technique has now been applied to cell-surface glycoproteins of different human hematopoietic cell lines. These lines included Epstein-Barr virus (EBV)-carrying lymphoblastoid cell lines of presumed non-neoplastic origin, and malignant EBV-genome-positive Burkitt lymphoma and EBV-negative non-Burkitt lymphoma, leukemia and myeloma lines. As compared with normal peripheral lymphocytes, both the lymphoblastoid type of cell lines and the different types of lines of proven malignant ancestry contained the fast-eluting glycopeptides on their cell surface with very few exceptions. It is therefore concluded that (I) malignant conversion of human lymphoid cell in vivo is commonly, but not obligatorily, associated with a specific change in the composition of the fucosyl glycopeptides, and (2) EBV infection of B lymphocytes does not lead only to the well-documented immortalization in vitro but also, as a rule, to the same type of alteration in fucosyl glycopeptides as was demonstrated for the neoplastic cell lines. It proved possible to distinguish several categories of hematopoietic cell lines due to the effect that pretreatment of the glycopeptides with neuraminidase or mild acid exerted on their subsequent chromatographic behavior.