Inhibition of growth of transformed cells and tumors by an endogenous acceptor of galactosyltransferase

A galactosyltransferase glycopeptide acceptor purified from human malignant effusions was tested for its effects on cell growth in vitro and in vivo. Addition of the glycopeptide to the media of cells growing in tissue culture caused a significant inhibition of attachment and growth of transformed cells but had minimal effect on nontransformed cells. Transformed hamster cells (BHKpy, BHKpygiv, NILpy) and human malignant cells (BT-20 human breast and pancreatic carcinoma cells) were killed by the addition of as little as 0.5 μg of acceptor (per ml of medium), while nontransformed counterparts did not show a significant change in growth or morphology. In vivo studies showed that the acceptor inhibited development and progression of tumors in hamsters inoculated with tumorigenic BHKpy cells. Growth of tumors was inhibited 69-94% in animals given 20 μg of acceptor subcutaneously and 39-67% when acceptor was given intraperitoneally at the time of tumor cell inoculation. Administration of the acceptor after the development of a palpable tumor (~0.5 cm) caused a 60-85% reduction in growth rate and, in some cases, actual reduction in size and disappearance of palpable tumor. These studies demonstrate that a galactosyltransferase glycopeptide acceptor purified from human malignant effusions produces selective inhibition of transformed cell growth in animal and tissue culture systems.