HYBRIDOMA CELLS PRODUCING ANTIBODIES TO CATHEPSIN-L HAVE GREATLY REDUCED POTENTIAL FOR TUMOR-GROWTH

Several tumour-forming cell lines are known to secrete the precursor o f a lysosomal cysteine proteinase, procathepsin L. The function in tum our growth and proliferation of this neutral-pH-labile proteinase or i ts precursor outside lysosomes is as yet unknown. Murine myeloma cells (P3X63Ag8.653) secrete procathepsin L and exhibit a high potential fo r malignant tumour growth and metastasis. Such cells were fused with s pleen cells of mice immunized with cathepsin L. Clones of the resultin g hybridoma cells continued to secrete procathepsin L, but also secret ed the antibody to cathepsin L. Here we show that the hybridoma cells producing an antibody to cathepsin L have, to a great extent, lost the potential that they otherwise exhibit for inducing solid tumours afte r implantation into mice.