Effects of altering surface glycoprotein composition on metastatic colonisation potential of murine mammary tumour cells.

This study has examined cells from naturally-occurring murine mammary tumours to ascertain whether cell surface glycoproteins play a significant role in colonisation of the lungs after intravenous inoculation. It was found that gel electrophoretic analysis of membrane extracts and lectin adsorption studies did not reveal any consistent differences in glycoprotein composition of cells from tumours which can heavily colonise the lungs relative to ones from tumours which cannot do so or to cells from pulmonary metastases. Also, alteration of structural and functional properties of surface glycoproteins by treatment with succinylated lectins or with drugs such as tunicamycin and swainsonine, which inhibit glycosylation of membrane proteins, had no specific effects on metastatic colonisation of the lungs. Tunicamycin apparently decreased capability to form experimental metastases but also diminished tumourigenicity on subcutaneous inoculation, although it did not affect tumour cell viability in vitro. This information supports earlier studies from this laboratory involving enzymic digestion of the surface of living tumour cells before inoculation and demonstrates that the pulmonary colonisation capability of these mammary tumour cells can withstand global disorganisation of membrane glycoprotein structure and composition. This implies that either the surface glycoproteins are not important in the colonisation process, or that these tumour cells have great capability for rapid repair of their surfaces. It is concluded that a clear answer to whether surface glycoprotein composition has a decisive role in pulmonary colonisation by these mammary tumour cells requires introduction of stable heritable traits into tumour cell populations by genetic manipulation.