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Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH
Published on: August 19, 2014
Low p53 expression of acute myelocytic leukemia cells with t(8;21) chromosome abnormality: association with low
Masato Shikami1, Hiroshi Miwa, Kazuhiro Nishii
1Department of Internal Medicine, Division of Hematology, Aichi Medical University, 21 Karimata, Nagakute, Aichi 480-1195, Japan.
Abstract:
In this study, the mRNA expression of p14(ARF) in t(8;21)AML cells was found to be significantly lower than acute myelocytic leukemia (AML) cells without t(8;21) chromosome abnormality, which was concordant with previous observation by Linggi et al. that AML1-MTG8 represses the transcription of p14(ARF). Although p53 mRNA expression level of t(8;21)AML cells was not low, p53 protein expression was reduced in t(8;21)AML cells. Genotoxic damage by ionizing radiation did not induce p53 upregulation in t(8;21)AML cells. Since p14(ARF) has been demonstrated to inhibit p53 degradation by binding to MDM2, repression of p14(ARF) expression in t(8;21)AML may facilitate the degradation of p53 by MDM2. Low p14(ARF) in t(8;21)AML may also account for the absence of upregulation of p53 by ionizing radiation. Then, we have shown that p53 expression level was inversely correlated with S/G2/M population of cell cycle in AML cells. Most of the t(8;21)AML are considered to be in p53(low) S/G2/M(high). It is now widely known that formation of AML1-MTG8 by t(8;21) translocation is a very early event in leukemogenesis, and AML1-MTG8 alone might have limited proliferative potential. Then, secondary oncogenic events such as activated receptor tyrosine kinase (like c-kit mutation), is necessary to become full-blown leukemia. Low p53 protein expression and insufficient induction of p53 by genotoxic damage might increase the opportunity to obtain additional oncogenic events, since genome guard function of p53 does not work in t(8;21)AML cells.
Insights
In t(8;21) acute myeloid leukemia (AML), low p14-ARF expression leads to reduced p53 protein, hindering DNA repair and promoting leukemogenesis. This impacts cell cycle progression and oncogenic event acquisition.
Area of Science:
- Hematology
- Molecular Biology
- Cancer Research
Background:
- The t(8;21) chromosomal translocation is an early event in acute myeloid leukemia (AML) pathogenesis.
- AML1-MTG8 fusion protein, resulting from t(8;21), is known to repress p14-ARF transcription.
- p53 protein's role in tumor suppression and DNA damage response is critical.
Purpose of the Study:
- To investigate the expression levels of p14-ARF and p53 in t(8;21) AML cells.
- To elucidate the functional consequences of altered p14-ARF and p53 in t(8;21) AML.
- To understand the implications for leukemogenesis and potential therapeutic strategies.
Main Methods:
- Quantitative analysis of mRNA and protein expression of p14-ARF and p53.
- Assessment of p53 response to genotoxic damage (ionizing radiation).
- Cell cycle analysis (S/G2/M populations) and correlation with p53 levels.
Main Results:
- t(8;21) AML cells exhibit significantly lower p14-ARF mRNA than non-t(8;21) AML cells.
- p53 protein expression is reduced in t(8;21) AML cells, despite normal mRNA levels.
- Genotoxic damage fails to upregulate p53 in t(8;21) AML cells, suggesting impaired p53 pathway activation.
- A significant inverse correlation exists between p53 expression and the S/G2/M cell cycle population in AML cells.
- Most t(8;21) AML cases display a p53(low) and S/G2/M(high) phenotype.
Conclusions:
- Repression of p14-ARF by AML1-MTG8 likely contributes to p53 degradation via MDM2 in t(8;21) AML.
- The impaired p53 response to DNA damage in t(8;21) AML cells may facilitate the acquisition of secondary oncogenic events.
- Reduced p53 function compromises the 'genome guard' role, potentially promoting full leukemogenesis.
