Yumiko Emoto PhD
Department of Biology, Graduate School of Sciences
E-mail: yemotscb@mbox.nc.kyushu-u.ac.jp
Cell proliferation in eukaryotes is controlled by the interplay between growth inhibitors and growth stimulators. Growth inhibitors are biologically as fundamental as the stimulators, but their structure and function are far less well characterized.
1.　We discovered cell-growth inhibitory activity in a salt extract of pig spinal cord. We purified the growth inhibitor by gel filtration, ion exchange chromatography and HPLC with a multimode column.

2.　Incubation of MDCK cells with the inhibitor suppressed their proliferation and caused them to become round. The effects were dose dependent, and the round cells that were still attached to the culture plate were alive. Upon removal of the inhibitor these cells flattened out and resumed proliferation. However, the inhibitor showed little effect on CHO-K1 cells. These results demonstrate that the effect of the inhibitor is reversible and is specific to certain types of cells.

3.　The growth inhibitor also suppressed detachment-induced apoptosis of MDCK cells.
Our results indicate that the inhibitory activity is not due to a nonspecific cytotoxic mechanism. The cell-growth inhibitor is therefore a substance with biological significance.