Partial Reversion of the Metastatic Phenotype in a Wheat Germ Agglutinin-Resistant Mutant of the Murine Tumor Cell Line MDAY-D2 Selected With <italic>Bandeiraea simplicifolia</italic> Seed Lectin<xref ref-type="fn" rid="FN2">2</xref>

Abstract

MDW4, a wheat germ agglutinin (WGA)-resistant (WGAr) mutant of the metastatic murine tumor cell line MDAY-D2, was previously shown to be nonmetastatic in the syngeneic DBA/2 host. A substantial portion of the asparagine (Asn)-linked carbohydrate in MDW4 terminated in N-acetylglucosamine (GlcNAc) and appeared to be a premature truncation product of the sialylated poly-N-acetyllactosamine-containing complex found in MDAY-D2 cells. This lesion in carbohydrate structure has been shown to contribute to the more adhesive behavior of MDW4 cells on laminin, fibronectin, and type IV collagen and to the increased sensitivity of MDW4 to natural killer (NK) cell lysis in vitro. For further characterization of the relationship between Asn-linked carbohydrate structures, cell adhesion, NK cell sensitivity, and metastasis, mutants of MDW4 were selected for resistance to the GlcNAc-binding lectin from Bandeiraea simplicifolia seeds (BSII). Three independently selected BSII-resistant (BSIIr) mutants of MDW4 chosen for further study had a lectin resistance phenotype intermediate between that of MDAY-D2 and that of MDW4. Plasma membrane glycoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with iodinated WGA, BSII, and leukoagglutinin also indicated an intermediate phenotype, with the presence of both GlcNAc-terminating structures and sialylated complex. Compared to MDW4, the BSIIr mutants of MDW4 showed a return to the more malignant phenotype of MDAY-D2 when injected iv. The double mutants were less sensitive to NK cell lysis in vitro and to the in vivo effects of the NK cell boosting agent polyinosinic-polycytidylic acid. The double mutants retained the ability to attach to fibronectin, laminin, and collagen type IV in vitro, a property that may have contributed to their low malignancy when the cells were injected sc. MDW4 cells have been shown to fuse at low frequency with host-derived bone marrow cells at the sc site of injection, thereby acquiring the wild-type lectin resistance and metastatic phenotypes. The same process appears to occur in mice given an injection of the double mutants. The results suggest that the WGA-binding oligosaccharides found in MDAY-D2 and the BSIIr mutants of MDW4 enhance the malignant phenotype of the cells in the experimental metastasis assay.