HAEM4:Acute Myeloid Leukemia (AML) with Biallelic Mutations of CEBPA

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Primary Author(s)*

Paul Defazio, MSc, Monash Health

Cancer Category/Type

Acute Myeloid Leukemia (AML)

Cancer Sub-Classification / Subtype

Acute myeloid leukaemia (AML) with biallelic CEBPA mutations

Definition / Description of Disease

AML with biallelic CEBPA (CCAT/Enhancer Binding Protein Alpha) mutations is a distinct disease entity in the 2016 World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia[1].

Mutations in CEBPA have been divided into two types[2]. Firstly, frameshift mutations in the N-terminal region trans-activating domain (TAD) between the alternative translation initiation sites can abolish expression of the larger isoform by introducing premature stop codons; this results in overexpression of the shorter isoform, which appears to have a dominant negative effect on the larger CEPBA protein. Secondly, in-frame C-terminal mutations in the bZIP domain reduce the DNA-binding potential of CEBPA and its ability to dimerise with other CEBP family members. Most CEBPA-mutated AMLs exhibit more than one mutation[2]. Compound heterozygous mutations affecting both the N-terminal and C-terminal regions of the CEBPA protein are associated with favorable clinical outcome in the context of AML, in the absence of complex karyotype or FLT3 internal tandem duplications. Only biallelic CEBPA mutations are prognostically significant; monoallelic mutations do not have prognostic implications[3].

Synonyms / Terminology

None

Epidemiology / Prevalence

Approximately 6-15% of de novo AML and 15-18% of AML with normal karyotypes have monoallelic or biallelic CEBPA mutations[1][4]. There does not appear to be age or gender differences between CEBPA mutated and non-mutated AML. Inherited heterozygous CEBPA mutations have also been linked to familial AML[5]. Inherited CEBPA are associated with earlier-onset AML. Taskesen et al. reported that five of 71 (7%) CEBPA-mutant AML patients carried germline mutations[4].

Clinical Features

AML with mutated CEBPA tends to have higher haemoglobin levels, lower platelet counts, lower lactate dehydrogenase levels and higher PB blast cell counts compared to CEBPA non-mutated AML[1]. There is also a lower frequency of lymphadenopathy and myeloid sarcoma in CEBPA mutated AML than in non-mutated AML[1].

Sites of Involvement

Blood, bone marrow

Morphologic Features

There are no distinctive morphological features of AML with CEBPA mutations. The vast majority of cases have features of AML with maturation or AML without maturation. Cases with monocytic or myelomonocytic features are less common.

Immunophenotype

Like in CEBPA wild-type AML, leukemic blasts usually express one or more of the myeloid-associated antigens CD13, CD33, CD65, CD11b, and CD15. HLA-DR and CD34 are also usually expressed on the majority of blasts. CD7, CD15, CD34, and HLA-DR expression are found in significantly more patients with biallelic CEBPA mutations than in unmutated patients[6]. Monocytic markers such as CD14 and CD64 are usually not expressed in AML with biallelic CEBPA mutations. Expression of CD56 and other lymphoid antigens is also uncommon.

Finding Marker
Positive (universal) EXAMPLE CD1
Positive (subset) EXAMPLE CD2
Negative (universal) EXAMPLE CD3
Negative (subset) EXAMPLE CD4

Chromosomal Rearrangements (Gene Fusions)

None

Chromosomal Rearrangement Genes in Fusion (5’ or 3’ Segments) Pathogenic Derivative Prevalence
EXAMPLE t(9;22)(q34;q11.2) EXAMPLE 3'ABL1 / 5'BCR EXAMPLE der(22) EXAMPLE 5%
EXAMPLE t(8;21)(q22;q22) EXAMPLE 5'RUNX1 / 3'RUNXT1 EXAMPLE der(8) EXAMPLE 5%

Characteristic Chromosomal Aberrations / Patterns

None

Genomic Gain/Loss/LOH

None

Chromosome Number Gain/Loss/Amp/LOH Region
EXAMPLE 8 EXAMPLE Gain EXAMPLE chr8:0-1000000
EXAMPLE 7 EXAMPLE Loss EXAMPLE chr7:0-1000000

Gene Mutations (SNV/INDEL)

Pathogenic mutations in CEBPA are predominantly insertion/deletion frameshift mutations in the N-terminal TAD region and in-frame C-terminal bZIP mutations. No particular mutational hotspots exist but the following table records the most reported mutations in the COSMIC database (frequency based on a count out of 1523 mutations):

Gene Mutation Oncogene/Tumor Suppressor/Other Presumed Mechanism (LOF/GOF/Other; Driver/Passenger) Prevalence (COSMIC/TCGA/Other)
CEBPA c.939_940insAAG, p.K313_V314insK Oncogene LOF 52
CEBPA c.68_69insC, p.H24fs*84 Oncogene LOF 43
CEBPA c.247delC, p.Q83fs*77 Oncogene LOF 32
CEBPA c.936_937insCAG, p.Q312_K313insQ Oncogene LOF 28
CEBPA c.912_913insTTG, p.K304_Q305insL Oncogene LOF 24

Other Mutations

Concurrent mutations in NPM1 and FLT3 are seen less frequently in individuals with biallelic CEBPA mutations than in those with no or monoallelic mutations[4]. Conversely, mutations in GATA2 appear to occur more often in CEBPA single- and double-mutants[7]. The prognostic significance of these concomitant mutations is, however, unclear. Biallelic CEBPA mutations appear to confer a positive prognostic effect regardless of concomitant mutations.

Type Gene/Region/Other
Concomitant Mutations NPM1, FLT3, GATA2
Secondary Mutations None
Mutually Exclusive None

Epigenomics (Methylation)

None

Genes and Main Pathways Involved

CEBPA, located on chromosome 19 band q13.1, encodes a transcription factor of the basic region leucine zipper (bZIP) family. It is involved in the coordination of myeloid differentiation and cellular growth arrest. Alternative translation initiation sites result in protein isoforms of different lengths.

CEPBA works in a tissue-specific manner to direct cellular differentiation by activating lineage-specific gene promoters. Interactions with the basal transcriptional apparatus (TBP/TFIIB), histone acetylators (CBP/p300), and chromatin-remodelling complexes (SWI/SNF) have all been implicated in lineage-specific gene activation by CEBPA. In the haematopoietic system there appears to be interplay between CEBPA and GATA factors[8]. CEBPA knockout mice show a complete lack of granulocytes while blasts accumulate in the bone marrow, suggesting an early block of myeloid maturation[9]. In the context of haematopoietic differentiation, evidence suggests CEBPA plays a role in regulating the expression of genes encoding growth factor receptors (e.g. granulocyte colony-stimulating factor) and secondary granule proteins (e.g. lactoferrin)[10][11]. It has also been implicated, along with NFI-A, in mediating miR-223 expression[12]. Studies indicate that CEBPA is not required for differentiation of granulocytes beyond the granulocyte-monocyte progenitor (GMP) stage, and that CEBPA controls stem-cell renewal with expression of Bmi-1 elevated in 'CEBPA knockouts[13]. Proliferation arrest also appears to be an important aspect of CEBPA function via interaction with CDK2/CDK4, upregulation of the p21 (WAF-1/CIP-1/SDI-1) protein and the SWI/SNF complex, and inhibition of the E2F complex[14][15][16][17][18]. This E2F inhibition leads to c-myc downregulation, which is required for granulocytic regulation[19]. Mutations in the C-terminal region of CEBPA abrogate CEBPA-E2F complex function[20]. The precise mechanism by which CEBPA mutants inhibit granulocytic differentiation in the context of AML is still unclear.

Diagnostic Testing Methods

Sanger sequencing, Next Generation Sequencing

Clinical Significance (Diagnosis, Prognosis and Therapeutic Implications)

Patients with biallelic CEBPA mutations and a normal karyotype have a more favorable prognosis than those with monoallelic or no CEBPA mutations, with higher complete remission rates and longer disease-free survival, relapse-free survival, event-free survival, and overall survival[1]. Patients with abnormal karyotypes (but not complex karyotypes) and biallelic CEBPA mutations also have longer disease-free survival, event-free survival, and overall survival when compared to patients with monoallelic or no CEBPA mutations[1].

Familial Forms

Familial mutations of CEBPA have been described in several families[5][21][22]. Typically, these are N-terminal mutations that are later joined by a somatic C-terminal mutation on the opposite allele leading to AML.

Other Information

Put your text here

Links

CEBPA

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Arber DA, et al., (2017). Acute myeloid leukaemia with recurrent genetic abnormalities, in World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, Revised 4th edition. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Arber DA, Hasserjian RP, Le Beau MM, Orazi A, and Siebert R, Editors. Revised 4th Edition. IARC Press: Lyon, France, p142-144.
  2. ↑ 2.0 2.1 Pabst, T.; et al. (2007). "Transcriptional dysregulation during myeloid transformation in AML". Oncogene. 26 (47): 6829–6837. doi:10.1038/sj.onc.1210765. ISSN 0950-9232. PMID 17934489.
  3. ↑ Wouters, Bas J.; et al. (2009). "Double CEBPA mutations, but not single CEBPA mutations, define a subgroup of acute myeloid leukemia with a distinctive gene expression profile that is uniquely associated with a favorable outcome". Blood. 113 (13): 3088–3091. doi:10.1182/blood-2008-09-179895. ISSN 1528-0020. PMC 2662648. PMID 19171880.
  4. ↑ 4.0 4.1 4.2 Taskesen, Erdogan; et al. (2011). "Prognostic impact, concurrent genetic mutations, and gene expression features of AML with CEBPA mutations in a cohort of 1182 cytogenetically normal AML patients: further evidence for CEBPA double mutant AML as a distinctive disease entity". Blood. 117 (8): 2469–2475. doi:10.1182/blood-2010-09-307280. ISSN 1528-0020. PMID 21177436.
  5. ↑ 5.0 5.1 Smith, Matthew L.; et al. (2004). "Mutation of CEBPA in familial acute myeloid leukemia". The New England Journal of Medicine. 351 (23): 2403–2407. doi:10.1056/NEJMoa041331. ISSN 1533-4406. PMID 15575056.
  6. ↑ Lin, Liang-In; et al. (2005). "Characterization of CEBPA mutations in acute myeloid leukemia: most patients with CEBPA mutations have biallelic mutations and show a distinct immunophenotype of the leukemic cells". Clinical Cancer Research: An Official Journal of the American Association for Cancer Research. 11 (4): 1372–1379. doi:10.1158/1078-0432.CCR-04-1816. ISSN 1078-0432. PMID 15746035.
  7. ↑ Green, Claire L.; et al. (2013). "GATA2 mutations in sporadic and familial acute myeloid leukaemia patients with CEBPA mutations". British Journal of Haematology. 161 (5): 701–705. doi:10.1111/bjh.12317. ISSN 1365-2141. PMID 23560626.
  8. ↑ McNagny, K. M.; et al. (1998). "Regulation of eosinophil-specific gene expression by a C/EBP-Ets complex and GATA-1". The EMBO journal. 17 (13): 3669–3680. doi:10.1093/emboj/17.13.3669. ISSN 0261-4189. PMC 1170703. PMID 9649437.
  9. ↑ Zhang, D. E.; et al. (1997). "Absence of granulocyte colony-stimulating factor signaling and neutrophil development in CCAAT enhancer binding protein alpha-deficient mice". Proceedings of the National Academy of Sciences of the United States of America. 94 (2): 569–574. doi:10.1073/pnas.94.2.569. ISSN 0027-8424. PMC 19554. PMID 9012825.CS1 maint: PMC format (link)
  10. ↑ Radomska, H. S.; et al. (1998). "CCAAT/enhancer binding protein alpha is a regulatory switch sufficient for induction of granulocytic development from bipotential myeloid progenitors". Molecular and Cellular Biology. 18 (7): 4301–4314. doi:10.1128/mcb.18.7.4301. ISSN 0270-7306. PMC 109014. PMID 9632814.CS1 maint: PMC format (link)
  11. ↑ Zhang, P.; et al. (1998). "Upregulation of interleukin 6 and granulocyte colony-stimulating factor receptors by transcription factor CCAAT enhancer binding protein alpha (C/EBP alpha) is critical for granulopoiesis". The Journal of Experimental Medicine. 188 (6): 1173–1184. doi:10.1084/jem.188.6.1173. ISSN 0022-1007. PMC 2212540. PMID 9743535.
  12. ↑ Fazi, Francesco; et al. (2005). "A minicircuitry comprised of microRNA-223 and transcription factors NFI-A and C/EBPalpha regulates human granulopoiesis". Cell. 123 (5): 819–831. doi:10.1016/j.cell.2005.09.023. ISSN 0092-8674. PMID 16325577.
  13. ↑ Zhang, Pu; et al. (2004). "Enhancement of hematopoietic stem cell repopulating capacity and self-renewal in the absence of the transcription factor C/EBP alpha". Immunity. 21 (6): 853–863. doi:10.1016/j.immuni.2004.11.006. ISSN 1074-7613. PMID 15589173.
  14. ↑ Pedersen, T. A.; et al. (2001). "Cooperation between C/EBPalpha TBP/TFIIB and SWI/SNF recruiting domains is required for adipocyte differentiation". Genes & Development. 15 (23): 3208–3216. doi:10.1101/gad.209901. ISSN 0890-9369. PMC 312836. PMID 11731483.CS1 maint: PMC format (link)
  15. ↑ Slomiany, B. A.; et al. (2000). "C/EBPalpha inhibits cell growth via direct repression of E2F-DP-mediated transcription". Molecular and Cellular Biology. 20 (16): 5986–5997. doi:10.1128/mcb.20.16.5986-5997.2000. ISSN 0270-7306. PMC 86075. PMID 10913181.CS1 maint: PMC format (link)
  16. ↑ Timchenko, N. A.; et al. (1996). "CCAAT/enhancer-binding protein alpha (C/EBP alpha) inhibits cell proliferation through the p21 (WAF-1/CIP-1/SDI-1) protein". Genes & Development. 10 (7): 804–815. doi:10.1101/gad.10.7.804. ISSN 0890-9369. PMID 8846917.
  17. ↑ Wang, H.; et al. (2001). "C/EBPalpha arrests cell proliferation through direct inhibition of Cdk2 and Cdk4". Molecular Cell. 8 (4): 817–828. doi:10.1016/s1097-2765(01)00366-5. ISSN 1097-2765. PMID 11684017.
  18. ↑ Wang, Qian-Fei; et al. (2003). "Cell cycle inhibition mediated by the outer surface of the C/EBPalpha basic region is required but not sufficient for granulopoiesis". Oncogene. 22 (17): 2548–2557. doi:10.1038/sj.onc.1206360. ISSN 0950-9232. PMID 12730669.
  19. ↑ Johansen, L. M.; et al. (2001). "c-Myc is a critical target for c/EBPalpha in granulopoiesis". Molecular and Cellular Biology. 21 (11): 3789–3806. doi:10.1128/MCB.21.11.3789-3806.2001. ISSN 0270-7306. PMC 87031. PMID 11340171.CS1 maint: PMC format (link)
  20. ↑ Porse, B. T.; et al. (2001). "E2F repression by C/EBPalpha is required for adipogenesis and granulopoiesis in vivo". Cell. 107 (2): 247–258. doi:10.1016/s0092-8674(01)00516-5. ISSN 0092-8674. PMID 11672531.
  21. ↑ Nanri, Tomoko; et al. (2010). "A family harboring a germ-line N-terminal C/EBPalpha mutation and development of acute myeloid leukemia with an additional somatic C-terminal C/EBPalpha mutation". Genes, Chromosomes & Cancer. 49 (3): 237–241. doi:10.1002/gcc.20734. ISSN 1098-2264. PMID 19953636.
  22. ↑ Sellick, G. S.; et al. (2005). "Further evidence that germline CEBPA mutations cause dominant inheritance of acute myeloid leukaemia". Leukemia. 19 (7): 1276–1278. doi:10.1038/sj.leu.2403788. ISSN 0887-6924. PMID 15902292.

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