Dataset Information

Methylated arsenic metabolites bind to PML protein but do not induce cellular differentiation and PML-RAR? protein degradation.

ABSTRACT: Arsenic trioxide (As2O3) is one of the most effective therapeutic agents used for patients with acute promyelocytic leukemia (APL). The probable explanation for As2O3-induced cell differentiation is the direct targeting of PML-RAR? oncoprotein by As2O3, which results in initiation of PML-RAR? degradation. However, after injection, As2O3 is rapidly methylated in body to different intermediate metabolites such as trivalent monomethylarsonous acid (MMA(III)) and dimethylarsinous acid (DMA(III)), therefore, it remains unknown that which arsenic specie is actually responsible for the therapeutic effects against APL. Here we have shown the role of As2O3 (as iAs(III)) and its intermediate metabolites (i.e., MMA(III)/DMA(III)) in NB4 cells. Inorganic iAs(III) predominantly showed induction of cell differentiation, while MMA(III) and DMA(III) specifically showed to induce mitochondria and endoplasmic reticulum-mediated apoptosis, respectively. On the other hand, in contrast to iAs(III), MMA(III) showed stronger binding affinity for ring domain of PML recombinant protein, however, could not induce PML protein SUMOylation and ubiquitin/proteasome degradation. In summary, our results suggest that the binding of arsenicals to the ring domain of PML proteins is not associated with the degradation of PML-RAR? fusion protein. Moreover, methylated arsenicals can efficiently lead to cellular apoptosis, however, they are incapable of inducing NB4 cell differentiation.

SUBMITTER: Wang QQ

PROVIDER: S-EPMC4694856 | biostudies-other | 2015 Sep

REPOSITORIES: biostudies-other

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Methylated arsenic metabolites bind to PML protein but do not induce cellular differentiation and PML-RARα protein degradation.

Wang Qian Qian QQ Zhou Xin Yi XY Zhang Yan Fang YF Bu Na N Zhou Jin J Cao Feng Lin FL Naranmandura Hua H

Oncotarget 20150901 28

Arsenic trioxide (As2O3) is one of the most effective therapeutic agents used for patients with acute promyelocytic leukemia (APL). The probable explanation for As2O3-induced cell differentiation is the direct targeting of PML-RARα oncoprotein by As2O3, which results in initiation of PML-RARα degradation. However, after injection, As2O3 is rapidly methylated in body to different intermediate metabolites such as trivalent monomethylarsonous acid (MMA(III)) and dimethylarsinous acid (DMA(III)), th ...[more]

PMID: 26213848

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Project description:Chronic exposure to inorganic arsenic (InAs) through drinking water is a major problem worldwide. InAs undergoes hepatic methylation to form mono- and dimethyl arsenical species (MMA and DMA, respectively), facilitating arsenic elimination. Both reactions are catalyzed by arsenic (+3 oxidation state) methyltransferase (AS3MT) using S-adenosylmethionine (SAM) as the methyl donor, yielding the methylated product and S-adenosylhomocysteine (SAH), a potent product-inhibitor of AS3MT. SAM biosynthesis depends on folate- and cobalamin-dependent one-carbon metabolism. With the use of samples from 353 participants in the Folate and Oxidative Stress Study, our objective was to test the hypotheses that blood SAM and SAH concentrations are associated with arsenic methylation and that these associations differ by folate and cobalamin nutritional status. Blood SAM and SAH were measured by HPLC. Arsenic metabolites in blood and urine were measured by HPLC coupled to dynamic reaction cell inductively coupled plasma MS. In linear regression analyses, SAH was not associated with any of the arsenic metabolites. However, log(SAM) was negatively associated with log(% urinary InAs) (?: -0.11; 95% CI: -0.19, -0.02; P = 0.01), and folate and cobalamin nutritional status significantly modified associations between SAM and percentage of blood MMA (%bMMA) and percentage of blood DMA (%bDMA) (P = 0.02 and P = 0.01, respectively). In folate- and cobalamin-deficient individuals, log(SAM) was positively associated with %bMMA (?: 6.96; 95% CI: 1.86, 12.05; P < 0.01) and negatively associated with %bDMA (?: -6.19; 95% CI: -12.71, 0.32; P = 0.06). These findings suggest that when exposure to InAs is high, and methyl groups are limiting, SAM is used primarily for MMA synthesis rather than for DMA synthesis, contributing additional evidence that nutritional status may explain some of the interindividual differences in arsenic metabolism and, consequently, susceptibility to arsenic toxicity.

Project description:Chronic ingestion of water containing inorganic arsenic (iAs) has been linked to a variety of adverse health effects, including cancer, hypertension and diabetes. Current evidence suggests that the toxic methylated trivalent metabolites of iAs, methylarsonous acid (MAs(III)) and dimethylarsinous acid (DMAs(III)) play a key role in the etiology of these diseases. Both MAs(III) and DMAs(III) have been detected in urine of subjects exposed to iAs. However, the rapid oxidation of DMAs(III) and, to a lesser extent, MAs(III) in oxygen-rich environments leads to difficulties in the analysis of these metabolites in samples of urine collected in population studies. Results of our previous work indicate that MAs(III) and DMAs(III) are relatively stable in a reducing cellular environment and can be quantified in cells and tissues. In the present study, we used the oxidation state-specific hydride generation-cryotrapping-atomic absorption spectroscopy (HG-CT-AAS) to examine the presence and stability of these trivalent metabolites in the liver of mice and in UROtsa/F35 cells exposed to iAs. Tri- and pentavalent metabolites of iAs were analyzed directly (without chemical extraction or digestion). Liver homogenates prepared in cold deionized water and cell culture medium and lysates were stored at either 0 °C or -80 °C for up to 22 days. Both MAs(III) and DMAs(III) were stable in homogenates stored at -80 °C. In contrast, DMAs(III) in homogenates stored at 0 °C began to oxidize to its pentavalent counterpart after 1 day; MAs(III) remained stable for at least 3 weeks under these conditions. MAs(III) and DMAs(III) generated in UROtsa/F35 cultures were stable for 3 weeks when culture media and cell lysates were stored at -80 °C. These results suggest that samples of cells and tissues represent suitable material for the quantitative, oxidation state-specific analysis of As in laboratory and population studies examining the metabolism or toxic effects of this metalloid.

Project description:The oncogenic fusion protein PML/RAR is expressed in most cases of acute promyelocytic leukemia (APL). In transgenic models, PML/RAR is able to induce a preleukemic state. However, it is not sufficient to induce leukemia, which develops with low frequency (~50%) and long latency (about 1 year). These data indicate that secondary genetic cooperating alterations are required in order to induce leukemia. In an effort to identify the genes that cooperate in the leukemogenesis PML/RAR-dependent, we performed an insertional mutagenesis screening infecting the PML/RAR KI mice with Moloney Murine Leukemia Virus (MLV). The infection of the PML/RAR KI mice significantly accelerated the onset (~6 months) and increased the penetrance (~75% of infected animals) of the leukemia. To identify genes mutated by the proviral integrations, flanking sequences of the retrovirus insertions were cloned by IPCR and analysed by parallel sequencing. We sequenced DNAs from the spleen of 48 independent leukemic mice. After filtering, ~133,000 reads were univocally mapped onto the mouse genome. Of them, ~131,000 were present more than once in the DNA from the same mouse and produced a total of 1,707 independent genomic insertions (retroviral insertion sites - RISs). To identify chromosomal regions that are frequently mutated by retrovirus insertions (common insertion sites; CISs), we evaluated the density of RISs distribution over the mouse genome, using statistical approaches that calculate the significance of RISs occurrence (p<0.05) within specific genomic regions (Monte Carlo simulation or Kernel Convolution). The two different approaches identified the same set of 221 CISs. Finally, we identified 271 genes putatively targeted by retroviral insertions in the 221 CISs. These putative targets appeared to be enriched in genes identified as relevant cancer-genes in different tumor types. Moreover, from a biological point of view, our screening was performed in saturating conditions. Therefore, to our knowledge, our is the first report of an exhaustive list of virtually all the mouse genes that functionally cooperate with PML/RAR in the induction of APL.

Dataset Information

Methylated arsenic metabolites bind to PML protein but do not induce cellular differentiation and PML-RAR? protein degradation.

Publications

Methylated arsenic metabolites bind to PML protein but do not induce cellular differentiation and PML-RARα protein degradation.

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