NUCLEOLAR AND NUCLEAR ABERRATIONS IN HUMAN LOX TUMOR-CELLS FOLLOWING TREATMENT WITH P120 ANTISENSE OLIGONUCLEOTIDE ISIS-3466

Previous reports from this laboratory have shown marked cytocidal effe cts of the ISIS-3466 antisense phosphorothioate oligodeoxynucleotide t o the human nucleolar protein p120 on human cancer cell lines in vitro and inhibition of tumor growth in vivo in an i.p./i.p. LOX cell model (L. Perlaky et al. Anti-Cancer Drug Design 8:3-14, 1993). In this stu dy, light and fluorescence microscopy showed that the number of LOX ce lls in mitosis decreased by 50% after incubation for 4 h in 0.2-0.4 mu M antisense oligonucleotide; a 70% reduction in cell number was found from 8-72 h post-treatment. In addition, marked unravelling of nucleo lar structures and chromatin fragmentation was found after a 4-h incub ation. The nucleolar unravelling occurred in varying degrees ranging f rom partial unfolding to almost complete separation of the strands of nucleolar residues. Twenty four hours post-treatment, immunofluorescen ce staining with the anti-p120 monoclonal antibody showed reduced nucl eolar protein p120 and translocation of the p120 protein from the nucl eoli to the nucleoplasm. Analysis of the mechanisms of the nucleolar u nravelling and inhibition of mitosis will provide further understandin g of the cytocidal effects of the ISIS-3466 antisense oligonucleotide.