Open AccessEffect of melphalan and hyperthermia on cell cycle progression and cyclin B 1 expression in human melanoma cells
Author(s) -
Orlandi L.,
Zaffaroni N.,
Bearzatto A.,
Costa A.,
Supino R.,
Vaglini M.,
Silvestrini R.
Publication year - 1995
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1995.tb00049.x
Subject(s) - melphalan , cancer research , melanoma , cell cycle progression , cell cycle , cyclin d , hyperthermia , cyclin , biology , medicine , cell , chemotherapy , genetics
We have investigated the effect of mild hyperthermia (42°C) on the cytotoxic activity of a 1 h melphalan exposure in human melanoma cell lines. Hyperthermia did not affect cell growth of any culture, but it increased, to a different extent, melphalan cytotoxicity in all cell lines, with a reduction in the IC 50 of 1.7 to 2.6‐fold. Flow cytometric analysis showed that in normal temperature conditions melphalan caused S phase cell accumulation, which was evident only at 24 h in JR8, M14 and 2/21 cell lines and was still persistent at 72 h in 2/60 cells. Moreover, in all cell lines, the delay in S phase was paralleled, or followed, by an accumulation of cells in G 2 + M, which was transient in JR8 and M14 cells and persisted until 72 h in 2/21 and 2/60 melanoma clones. Hyperthermia caused a stabilization and prolongation of melphalan induced G 2 + M accumulation in JR8 and M14 cells. Conversely, in 2/21 and 2/60 clones, cell cycle perturbations induced by the drug were similar under normothermic or hyperthermic conditions. Specifically, in JR8, for which the maximum enhancement by hyperthermia on melphalan cytotoxicity was observed, cell accumulation in G 2 + M was still present 120 h after treatment. The accumulation was accompanied by an inhibition in the G 2 ‐ M transition, as demonstrated by the significant reduction in the mitotic index of cells exposed to combined treatment compared to controls. Moreover, a bivariate distribution of cells stained for DNA and cyclin B 1 showed that, following melphalan and hyperthermia treatment, the fraction of cyclin B 1 ‐expressing cells paralleled the fraction of G 2 + M phase cells, thus indicating that the inability of cells to enter mitosis was not ascribable to a reduction of cyclin B 1 expression. On the whole, our results indicate that hyperthermia can stabilize the G 2 accumulation induced by melphalan in human melanoma cells. Such a stabilization could contribute to the enhancement of melphalan cytotoxicity by heat, even though a strict correlation was not observed between the magnitude and persistence of the cell cycle perturbations and the extent of melphalan activity.