Camptothecin and its analogues are used as S-phase specific
antitumor drugs because of
topoisomerase I inhibition providing cells to death by apoptosis. Our previous works documented that amelanotic hamster's
melanoma is very sensitive to
camptothecin. Because of the challenges in treating
melanoma and S-phase specificity of
camptothecin, we performed a study to search what
melanoma cell cycle phases are susceptible to this substance. Melanotic (Ma) and amelanotic (Ab) lines of Bomirski hamster's
melanoma were used.
Camptothecin cytotoxicity was determined by TUNEL method and cell cycle analysis was done by
DNA staining with
propidium iodide.
Camptothecin after short time killed
amelanotic melanoma cells from S/G2/M phases but with extended time dying cells came from G0/G1. Melanotic
melanoma had fewer cells in S/G2/M phases and 3-fold more of these cells spontaneously died in comparison to more aggressive amelanotic line. High susceptibility of
amelanotic melanoma cells to
camptothecin show that not only cells with proliferative activity were sensitive to this
alkaloid but with extended time it killed cells from all cycle phases. High number of cells in S/G2/M phases and low rate of spontaneous death among
amelanotic melanoma cells suggest that the expansive growth of this
melanoma line depends mainly on the decreased ability to undergo spontaneous apoptosis. If the sensitivity of
amelanotic melanoma is not only hamster's but also human
melanoma feature, we can suspect that by choosing
melanoma form for treatment with
camptothecin we could improve effectiveness of this
drug against
melanoma.