Cyclical changes in susceptibility of a myeloma tumor (LPC-1) to immune destruction. III. Periodic production of a cell surface glycoprotein and changes in reactivity with cytotoxic T cells and anti-H-2(d) sera

Previous studies showed that when LPC-1 myeloma cells were grown as ascites tumor cells in syngeneic (BALB/c) mice, the cells harvested after 2 to 4 days of growth ('early' cells) were susceptible to lysis by cytotoxic T lymphocytes (CTL) and highly reactive with anti H-2(d) antisera. Cells harvested after 12 to 14 days of growth ('late' cells) were resistant to lysis by CTL and poorly reactive with anti-H-2(d) antisera. The present study shows that exposure to trypsin or chymotrypsin or subtilisin (but not to thrombin or Staphylococcus A protease) promptly converts LPC-1 cells with the late phenotype into cells with the early phenotype. Comparison of radiolabeled cell surface proteins by gel electrophoresis showed that the late cells possess a prominent trypsin sensitive, high m.w. (160,000 daltons) surface glycoprotein that is present in smaller amounts on the early LPC-1 cells. This glycoprotein (gp160) was not detectable in four other BALB/c tumors that do not undergo the early late transition of LPC-1. That gp160 was produced by LPC-1 cells, rather than adsorbed by these cells as they grow in vivo, was evident from the presence of an indistinguishable metabolically labeled glycoprotein on cultured LPC-1 cells.