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Neuroblastoma is a highly malignant neoplasm found in young children. Although children with high-risk neuroblastoma respond to chemotherapy, relapses are common. On account of poor treatment outcome, new treatment strategies are constantly sought for neuroblastoma. Polyamine analogues are potentially novel substances for treatment of neuroblastoma. In this study, we have treated two neuroblastoma cell lines, SH-SY5Y and LA-N-1, with the spermine analogue N1, N11-Diethylnorspermine (DENSPM). SH-SY5Y was the most sensitive cell line, in which DENSPM treatment resulted in an inhibition of cell proliferation and an induction of cell death. The cell death induced by DENSPM treatment was apoptotic, as evidenced by cleavage of procaspase 3 and induction of caspase-3 activity. In contrast, DENSPM treatment only resulted in a slight inhibition of cell proliferation in LA-N-1 cells. There were several possible causes for the lower sensitivity to DENSPM treatment in the latter cell line when compared with SH-SY5Y cells. DENSPM-induced polyamine depletion was more extensive in SH-SY5Y cells than in LA-N-1 cells. This was partly because of a higher induction of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase in the cell line SH-SY5Y. The DENSPM-induced polyamine depletion was also caused by the inhibition of ornithine decarboxylase. LA-N-1 cells contained a higher level of the prosurvival protein survivin, which was further increased after DENSPM treatment. In contrast, DENSPM treatment resulted in a decreased survivin level in SH-SY5Y cells.

Polyamine analogue treatment results in growth inhibition and sometimes in cell death. Therefore, polyamine analogues are considered in the treatment of cancer; however, the cellular properties that govern sensitivity are not known. The objective of this study was to elucidate molecular mechanisms behind apoptosis induced by the polyamine analogue N, N-diethylnorspermine (DENSPM). Four different breast cancer cell lines were treated with DENSPM. Cell death was evaluated with flow cytometry and a caspase 3 assay. The levels of a number of proapoptotic and antiapoptotic proteins in subcellular compartments were evaluated with western blot. In the most sensitive cell line, DENSPM treatment induced the release of cytochrome c from mitochondria, resulting in activation of caspase 3 but without decreasing the mitochondrial transmembrane potential. However, in the three other cell lines DENSPM treatment did not induce extensive cell death. This is partly explained by the high levels of antiapoptotic proteins Bcl-2 and Bad and low levels of proapoptotic proteins Bax and procaspase 3 in these three cell lines. The results are also partly explained by the degree of activation of the catabolic enzyme spermidine/spermine-N-acetyltransferase and polyamine pool reduction achieved by DENSPM treatment. Our results show that the protein profile of proapoptotic and antiapoptotic proteins may contribute to the outcome to treatment with the polyamine analogue DENSPM. The results also indicate that it should be possible to find molecular markers for sensitivity to DENSPM that could be used in the clinic to predict sensitivity to a polyamine analogue.