Abstract
In the present paper, we investigated the relationship between the growth inhibitory effects of recombinant interferon-α2b (rIFN-α2b) and poly (ADPR) polymerase-1 (PARP-1) activity in the human squamous KB cancer cell line. Growth inhibition of the KB cells mediated by 1000 IU/ml of rIFN-α2b was accompanied by a transient rise in PARP-1 specific activity 24 h after rIFN-α2b treatment, confirmed by both the increase of intracellular poly (ADP-ribose) content and the PARP-1 auto-modification level. At longer times of incubation, the onset of apoptosis accompanied KB cell growth inhibition, as demonstrated by both flow cytometry and western-blotting analysis showing an 89 kDa apoptotic fragment of PARP-1. Moreover, pretreatment of the cells with the PARP-1 inhibitor, 3-aminobenzamide (3-ABA), at non-cytotoxic concentrations (1 mM), reduced the cell-growth inhibition, cell-cycle perturbation and apoptosis caused by rIFN-α2b. Taken together, these results strongly suggest that PARP-1 may be directly involved in the effects of rIFN-α2b in the KB cancer cell line.
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