Arsenic trioxide (ATO) is an effective chemotherapeutic agent for the treatment of acute promyelocytic leukemia and is being tested in phase II studies in various types of hematological malignancies and solid tumors. We have previously shown that ATO is a potent inducer of apoptosis in multiple myeloma cells, engaging primarily the intrinsic apoptotic pathway in cells expressing w.t. p53. In contrast, in cells expressing mutant p53, both the intrinsic and extrinsic apoptotic pathways are engaged. These findings were further supported by a recent study using a p53 temperature sensitive (p53Ts) mutant cell line, BRK, expressing w.t. p53 at 32°C and mutant p53 phenotype at 37°C (

Akay et al. Akay et al.,
AACR
; Abstract #
5344
,
2005
). Furthermore, myeloma cells expressing w.t. p53 transfected with SiRNA for p53 or p21 behaved like cells with mutant p53 (Kircelli et al. ASH presentation,2005). In order to identify new genes affected by ATO we used the Affymetrix Microarray technology to compare global gene expression in IM9 myeloma cells (w.t. p53) and U266 myeloma cells (mutant p53) following 0, 1,5 and 10 hours of treatment with ATO. We found ≥2 fold increase in gene expression by Affymetrix Microarray Suite Software (MAS) in 94 genes at 5 h and 455 genes at 10 h with an increase in 134, at both 5 and 10 h of treatment. By similar analysis, 263 genes were decreased at 5 h and 679 genes were decreased at 10 h with 204 genes decreased at both time points. Similar analysis with GeneSpring (GS) software revealed an increase in 202 genes and a decrease in 233 genes at both 5 and 10 h. Combination of the 2 analysis methods yielded 90 consistent increasers and 64 consistent decreasers. A great number of these genes in whom we detected changes in this study are genes that were previously identified by us and by others using Western immunoblotting. In addition, we observed differential effect of ATO in IM9 and U266 myeloma cells in apoptosis-related genes (HRK, BID, MCL1); cell cycle-related genes (GADD45, Cyclin D1, cyclin D2 and cyclin D3); signal transduction proteins (ERK, NFkB, ATM, ATR, CHK2, TRAILR2, TNF-R5/6 and VEGF); in chaperon proteins; cyclophyllin B; SAT, ToPoIIA and others. Systematic validation of these changes on the protein levels is ongoing.

Topics:
apoptosis, arsenic trioxide, gene expression, myeloma cells, cyclins, acute promyelocytic leukemia, antineoplastic agents, apoptosis promoter, cyclin d1, hematologic neoplasms

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2005, The American Society of Hematology
2005
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