INHIBITION OF PROLIFERATION AND INDUCTION OF APOPTOSIS BY ABROGATION OF HEAT-SHOCK PROTEIN (HSP)-70 EXPRESSION IN TUMOR-CELLS

Tumor cells often express elevated levels of heat-shock protein (HSP) 70. The present study was designed to invesitgate the role of HSP70 in the proliferation and survival of tumor cells in the human system. Wh en Molt-4 and other tumor cells were treated in vitro with HSP70 antis ense oligomer, they displayed propidium-iodide-stained condensed nucle i (intact or fragmented). A ladder-like pattern of DNA fragments was o bserved with HSP70 antisense-oligomer-treated tumor cells in agrose ge l electrophoresis, which was consistent with internucleosomal DNA frag mentation. Flow cytometry analysis revealed the hypodiploid DNA peak o f propidium-iodide-stained nuclei in the antisense-oligomer-treated ce lls. The apoptosis induced by HSP antisense oligomer was dose- and tim e-dependent. The antisense oligomer induced apoptosis mainly in tumor cells at G1 and S phase, resulting in an inhibition of cell proliferat ion. HSP70 antisense oligomer caused DNA-sequence-specific inhibition of HSP70 expression, which preceded apparent apoptosis. These results indicate that HSP70 antisense treatment inhibits the expression of HSP 70, which in turn inhibits cell proliferation and induces apoptosis in tumor cells and suggest that HSP70 is required for tumor cells to pro liferate and survive under normal condition.