Transfection by human oncogenes: Concomitant induction of tumorigenicity and tumor‐associated membrane alterations

Abstract

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.

Metastatic potential of transformed rat 3Y1 cell lines is inversely correlated with lysosomal‐type sialidase activity

“…Consequently, their metabolic shift to an increased sialic acid density, at least of some sialoglycoproteins responsible, may bring about the enhanced metastasis, especially invasiveness. This is also consistent with other work demonstrating good correlations between sialic acid contents and invasiveness [4,6,8,9]. We have further found that BL6 cells, a high invasive variant of B16 melanoma cells, have higher levels of sialyltransferase activity than cells of low invasiveness, although in that case sialidase activity was hardly affected (unpublished data).…”

“…The changes generally involve glycoproteins expressed on tumor cell surface with increased branching of complex-type N-glycans, increased polylactosaminoglycan chains and increased sialylation [l-5], which are correlated not only with tumorigenicity but also with elevated metastatic potential [6,7]. In particular, the alterations in sialylation have been proposed to be intimately associated with invasiveness and metastatic ability [4,6,8,9]. To elucidate how such aberrant sialylation occurs in cancer cells, we have been studying sialidase and sialyltransferase in rat hepatoma [lo-121 and other tumor models [13].…”

Sensitisation of HL60 human leukaemic cells to cytotoxic drug-induced apoptosis by inhibition of PI3-kinase survival signals

“…36 To investigate these survival pathways and their importance in impeding apoptosis, we used the acute pro-myeloid leukaemic cell line, HL60, which has an activating N-Ras mutation. 37,38 Furthermore, HL60 cells, although highly expressing Bcl-2 are unselected for enhanced resistance to cytotoxic drugs. 39 This is relatively uncommon in drug resistance studies which often employ cell lines which have been artificially selected for high levels of resistance to concentrations of drugs which may never be clinically relevant.…”

Rodent fibroblast tumours expressing human myc and ras genes: growth, metastasis and endogenous oncogene expression

“…Ras-expressing cells develop a constellation of new features. Some of these could be expected to favour autonomous growth, such as the production of tumour growth factors (Ozanne et al, 1982;Anzano et al, 1985;Pragnell et al, 1985;Spandidos, 1985;Marshall et al, 1985) and release from pre-existing control by exogenous trophic stimuli (Kasid et al, 1985;Racker et al, 1985;Zahn & Goldfarb, 1986), whilst some correlate strongly with invasive and metastatic ability, such as increased sialylation of surface glycoproteins (Collard et al, 1985). Ras gene expression, however, is also associated with enhanced cellular capacity to act as a target for NK cytocidal activity (Johnson et al, 1985;Trimble et al, 1986) a feature likely to militate against successful metastasis (Nicolson & Poste, 1983;Hanna & Schneider, 1983).…”