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Recognition of asparagine-linked oligosaccharides on murine tumor cells by natural killer cells
Abstract:
MDW4, a wheat germ agglutinin resistant mutant of the murine tumor line MDAY-D2, expresses abnormal asparagine-linked oligosaccharides, is less metastatic when injected intravenously, and is hypersensitive to natural killer (NK) lysis in vitro. To determine whether these phenotypes may be related, variants of the YAC-1 lymphoma and a YAC-1 X MDAY-D2 hybrid line were compared for sensitivity to four different lectins and to NK cell lysis in vitro. A relationship between sensitivity to concanavalin A (Con A) and NK cell lysis in vitro was observed. Although no single plasma membrane glycoprotein separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with 125I-labeled Con A correlated with NK and Con A sensitivities of the cell lines, a relationship between these phenotypes and the collective 125I-Con A staining intensity on the gels was apparent. In a more direct test of carbohydrate recognition by NK cells, specific glycopeptide structures isolated from tumor cells and added to the NK cell assay in microM quantities were found to inhibit tumor cell lysis. Thus, a subset of asparagine-linked oligosaccharides, including high mannose and some incomplete complex structures on a number of cell surface glycoproteins, appears to be recognized as part of the target structures for NK cell lysis. The administration of polyinosinic:polycytidylic acid stimulated splenic NK activity in vivo but had no effect on the growth of the NK-resistant MDAY-D2 cells. However, the low tumorigenicity of MDW4 cells injected intravenously was reduced further by pretreating the mice with polyinosinic:polycytidylic acid, which indicated a role for NK cells in the elimination of circulating tumor cells expressing high mannose and/or incomplete complex asparagine-linked oligosaccharides.
Insights
Tumor cell surface oligosaccharides, particularly high mannose types, are recognized by natural killer (NK) cells. This recognition influences tumor cell lysis and metastasis, suggesting a target for cancer immunotherapy.
Area of Science:
- Immunology
- Glycobiology
- Cancer Research
Background:
- Murine tumor line MDW4, a mutant of MDAY-D2, exhibits altered asparagine-linked oligosaccharides, reduced metastasis, and increased sensitivity to natural killer (NK) cell lysis.
- The relationship between these altered cell surface carbohydrates and NK cell recognition requires further investigation.
Purpose of the Study:
- To investigate the link between specific oligosaccharide structures on tumor cell surfaces and their susceptibility to NK cell-mediated lysis.
- To explore the potential of targeting these carbohydrate structures for cancer therapy.
Main Methods:
- Comparison of YAC-1 lymphoma and YAC-1 x MDAY-D2 hybrid cells for sensitivity to lectins and NK cell lysis.
- Analysis of plasma membrane glycoproteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 125I-labeled concanavalin A (Con A).
- Inhibition assays using isolated glycopeptides to assess NK cell recognition of specific carbohydrate structures.
Main Results:
- A correlation was observed between sensitivity to Con A and NK cell lysis.
- While no single glycoprotein was solely responsible, overall 125I-Con A staining intensity related to NK and Con A sensitivities.
- Specific glycopeptides, including high mannose and incomplete complex oligosaccharides, inhibited tumor cell lysis, indicating their recognition by NK cells.
- Polyinosinic:polycytidylic acid enhanced NK activity but did not affect resistant tumor growth; however, it reduced the intravenous growth of MDW4 cells.
Conclusions:
- A subset of asparagine-linked oligosaccharides on tumor cell surface glycoproteins are recognized by NK cells as targets.
- These findings suggest that NK cell recognition of specific cell surface carbohydrates plays a role in eliminating circulating tumor cells and may represent a therapeutic target.