The tumour suppressor ING1 shares many biological functions with p53, such as cell cycle arrest, DNA repair, apoptosis, and chemosensitivity. Previous findings indicate that the isoform p24ING1 is capable of enhancing chemosensitivity in human fibroblasts. To investigate if the p33ING1 isoform is also involved in chemosensitivity, we overexpressed p33ING1 in melanoma cells and assessed for cell death after treatment with camptothecin. Results from the sulforhodamine B cell survival assay and flow cytometry analysis show no significant difference among cells transfected with vector, p33ING1, and antisense p33ING1. Furthermore, co-transfection of the p33ING1 and p53 constructs had no effect on the frequency of cell death, indicating that there is no synergistic effect between the two tumour suppressors in camptothecin-induced cell death in melanoma cells. This is in contrast to previously observed collaboration between p33ING1 and p53 in DNA repair and apoptosis. Taken together, we demonstrate that p33ING1 does not enhance camptothecin-induced cell death in melanoma cells.

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