Purification and biological properties of an epithelial intestinal cell growth inhibitor from a human small intestine.

ABSTRACT

Endogenous mitotic inhibitors act as control-mechanisms in intestinal epithelium proliferation. The presence of an inhibitor of cultured intestinal epithelial cell from a villous extract of rat jejunum has been reported in one of our papers. The object of the study now reported was to find the presence of a growth inhibitor in the villous extract from man's small intestine and to purify and characterize this factor when found. Our results reveal that (1) Such an inhibitor was found in a supernatant preparation obtained from human intestinal epithelial cells. The inhibition of the proliferation of epithelial cells (IRD-98) it induced was seem to be dose-dependent and non-cytotoxic. (2) After chromatography on hydroxylapatite, on DEAE and then on ACA 54 (gel permeation), a low-molecular-weight protein (15 kDa) called purified intestinal inhibitor (PII) was isolated (purification factor of approx. 50,000 with respect to the supernatant fraction). This fraction proved to inhibit the IRD-98 cells in a reversible manner. When cells are incubated with this protein, cells prove to be arrested in phase G1 of the cell cycle as is revealed by the flow cytometry studies. The results obtained support the hypothesis that regulation of cell proliferation is mediated by endogenous inhibitors at the epithelial level.