THE ROLE OF Hsp70 CHAPERONE IN THE REACTION OF HUMAN LEUKEMIC CELLS ON ANTICANCER
DRUGS
E. Yu. Komarova, B. A. Margulis, I. V. Guzhova
Institute of Cytology RAS, St. Petersburg, Russia;
1 e-mail: guzhova@link.cytspb.rssi.ru
Most of anti-tumor factors are designed to kill selectively cancer cells; in most cases this action is related to the ability
of the above substances to induce apoptosis. One of potent anti-apoptotic mechanisms is based on Hsp70 protein. Since the level of
this protein is often higher in malignant tumors than in normal tissues, the aim of this study was to establish whether the elevated Hsp70
content may influence the process of apoptosis induced by anti-tumor drugs in cancer cells population. The increase of intracellular
content of Hsp70 in human leukemia U-937 cells was attained by a mild heat stress or by transfection of cells with the human
hsp 70 gene. The elevation of Hsp70 quantity, irrespective of the way it was performed, leads to the inhibition of apoptosis in
cells treated with two substances, etoposide or adriamycin. The inhibition of apoptosis was accompanied with the reducing of the
share of cells with fragmented nuclei and with the delay in caspase activation. It is suggested that in addition to the previously discovered
targets, whose activity is suppressed by the Hsp70 chaperone, this protein can inhibit the activity of caspase-3 and -7; this delays the
onset of apoptosis in part of a cancer cell population.
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