Induction of polyploidization in the human erythroleukemia cell line (HEL) by
protein kinase inhibitor (K252a) and the phorbol-ester TPA.
Yokoe H, Masumi-Fukazawa A, Sunohara M, Tanzawa H, Sato K, Sato T, Fuse A.
Department of Safety Research on Biologics, National Institute of Health, Tokyo,
Japan.
Endomitosis (polyploidization) is a distinctive feature of megakaryocyte
differentiation. We examined this mechanism in an erythromegakaryocytic cell
line, HEL, using a protein kinase inhibitor K252a or a phorbol-ester TPA. HEL
cells treated with K252a showed a marked increase in the proportion of CD41
positive cells and polyploid cells as well as in cellular size and nuclear size.
TPA showed similar results but induced multi-nucleation instead of enlargement
of nuclear size. K252a added at the G1/S boundary phase did not inhibit the
first and second round DNA synthesis, but inhibited cell division. K252a did not
inhibit the expression of genes involved in mitosis such as cyclin B, cdc25B and
cdc2, in the first round S phase. However, the cyclin B associated Cdc2 kinase
activity needed for mitosis during the G2/M phase was reduced by K252a. TPA
delayed DNA synthesis and expression of these genes, and suppressed Cdc2 kinase
activity in the second round G2/M phase. These results suggest that the
polyploidization induced by K252a results from inhibiting mitosis possibly
caused by suppression of Cdc2 kinase activity. TPA may induce the
multi-nucleation through a different mechanism.
Publication Types:
Research Support, Non-U.S. Gov't
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