Oligonucleotides offer the potential to manipulate gene expression in targeted cells which might be exploitable for therapeutic benefit. The effects of combining a phosphorothioate
oligonucleotide OL(1) p53, which transiently down-regulates p53 levels, with an
anthracycline,
Idarubicin, on the growth of wild-type p53 WMN gene-expressing
lymphoma cells was evaluated. Fluorescent
OL(1) p53, was used to demonstrate
oligonucleotide uptake and retention by the WMN cells. Uptake was maximal at 24 hours and compared to baseline (0 hours) increasing apoptotic cells were evident in WMN cells treated with OL(1) (1 microM) alone and in combination with
Idarubicin (0.2 nM) for 24 to 48 hours. In cells treated with
OL(1) p53 and
Idarubicin, truncated p53 message of a predicted 201 base pair length based on
RNAase H cleavage of the OL(1) p53-p53
mRNA heteroduplex was detected after 7 hours of incubation. The message for p53 was transiently downregulated as detected by RT-PCR analysis at 24 hours, and
protein levels transiently reduced at 36 hours, as shown by a quantitative Western blot. Corresponding to these events, the growth of WMN cells ceased after 48 hours in the concurrent presence of
OL(1) p53 and
Idarubicin and, the
lymphoma cells were dead after 72 hours. No reduction in hematopoietic colony forming cell capacity of similarly treated hematopoietic progenitor cells harvested from
cytokine-mobilized blood by
apheresis was observed. Therefore, synergistic cytotoxicity of
Idarubicin for
lymphoma cells treated with an
oligonucleotide targeting p53 message was demonstrated at
oligonucleotide and
Idarubicin concentrations which were minimally toxic to hematopoietic progenitor cells. This approach offers new opportunities for purging of
lymphoma cells from hematopoietic harvests and systemic
lymphoma therapy.