Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia

Marcus Matthias Schittenhelm, Bianca Walter, Vasileia Tsintari, Birgit Federmann, Mihada Bajrami Saipi, Figen Akmut, Barbara Illing, Ulrike Mau-Holzmann, Falko Fend, Charles Lopez, Kerstin Maria Kampa-Schittenhelm

    Research output: Contribution to journalArticle

    Abstract

    Background: Apoptosis-stimulating Protein of TP53-2 (ASPP2) is a tumor suppressor enhancing TP53-mediated apoptosis via binding to the TP53 core domain. TP53 mutations found in cancers disrupt ASPP2 binding, arguing for an important role of ASPP2 in TP53-mediated tumor suppression. We now identify an oncogenic splicing variant, ASPP2κ, with high prevalence in acute leukemia. Methods: An mRNA screen to detect ASPP2 splicing variants was performed and ASPP2κ was validated using isoform-specific PCR approaches. Translation into a genuine protein isoform was evaluated after establishing epitope-specific antibodies. For functional studies cell models with forced expression of ASPP2κ or isoform-specific ASPP2κ-interference were created to evaluate proliferative, apoptotic and oncogenic characteristics of ASPP2κ. Findings: Exon skipping generates a premature stop codon, leading to a truncated C-terminus, omitting the TP53-binding sites. ASPP2κ translates into a dominant-negative protein variant impairing TP53-dependent induction of apoptosis. ASPP2κ is expressed in CD34+ leukemic progenitor cells and functional studies argue for a role in early oncogenesis, resulting in perturbed proliferation and impaired induction of apoptosis, mitotic failure and chromosomal instability (CIN) – similar to TP53 mutations. Importantly, as expression of ASPP2κ is stress-inducible it defines a novel class of dynamic oncogenes not represented by genomic mutations. Interpretation: Our data demonstrates that ASPP2κ plays a distinctive role as an antiapoptotic regulator of the TP53 checkpoint, rendering cells to a more aggressive phenotype as evidenced by proliferation and apoptosis rates – and ASPP2κ expression results in acquisition of genomic mutations, a first initiating step in leukemogenesis. We provide proof-of-concept to establish ASPP2κ as a clinically relevant biomarker and a target for molecule-defined therapy. Fund: Unrestricted grant support from the Wilhelm Sander Foundation for Cancer Research, the IZKF Program of the Medical Faculty Tübingen, the Brigitte Schlieben-Lange Program and the Margarete von Wrangell Program of the State Ministry Baden-Wuerttemberg for Science, Research and Arts and the Athene Program of the excellence initiative of the Eberhard-Karls University, Tübingen.

    Original languageEnglish (US)
    Pages (from-to)340-351
    Number of pages12
    JournalEBioMedicine
    Volume42
    DOIs
    StatePublished - Apr 1 2019

    Fingerprint

    Tumor Suppressor Protein p53
    Alternative Splicing
    Tumors
    Protein Isoforms
    Leukemia
    Apoptosis
    Neoplasms
    Mutation
    Sanders
    Medical Faculties
    Chromosomal Instability

    Keywords

    • Acute leukemia
    • Alternative splicing
    • ASPP2
    • Oncogenesis

    ASJC Scopus subject areas

    • Biochemistry, Genetics and Molecular Biology(all)

    Cite this

    Schittenhelm, M. M., Walter, B., Tsintari, V., Federmann, B., Bajrami Saipi, M., Akmut, F., ... Kampa-Schittenhelm, K. M. (2019). Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia. EBioMedicine, 42, 340-351. https://doi.org/10.1016/j.ebiom.2019.03.028

    Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia. / Schittenhelm, Marcus Matthias; Walter, Bianca; Tsintari, Vasileia; Federmann, Birgit; Bajrami Saipi, Mihada; Akmut, Figen; Illing, Barbara; Mau-Holzmann, Ulrike; Fend, Falko; Lopez, Charles; Kampa-Schittenhelm, Kerstin Maria.

    In: EBioMedicine, Vol. 42, 01.04.2019, p. 340-351.

    Research output: Contribution to journalArticle

    Schittenhelm, MM, Walter, B, Tsintari, V, Federmann, B, Bajrami Saipi, M, Akmut, F, Illing, B, Mau-Holzmann, U, Fend, F, Lopez, C & Kampa-Schittenhelm, KM 2019, 'Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia', EBioMedicine, vol. 42, pp. 340-351. https://doi.org/10.1016/j.ebiom.2019.03.028
    Schittenhelm, Marcus Matthias ; Walter, Bianca ; Tsintari, Vasileia ; Federmann, Birgit ; Bajrami Saipi, Mihada ; Akmut, Figen ; Illing, Barbara ; Mau-Holzmann, Ulrike ; Fend, Falko ; Lopez, Charles ; Kampa-Schittenhelm, Kerstin Maria. / Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia. In: EBioMedicine. 2019 ; Vol. 42. pp. 340-351.
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    AU - Walter, Bianca

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    AU - Federmann, Birgit

    AU - Bajrami Saipi, Mihada

    AU - Akmut, Figen

    AU - Illing, Barbara

    AU - Mau-Holzmann, Ulrike

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    N2 - Background: Apoptosis-stimulating Protein of TP53-2 (ASPP2) is a tumor suppressor enhancing TP53-mediated apoptosis via binding to the TP53 core domain. TP53 mutations found in cancers disrupt ASPP2 binding, arguing for an important role of ASPP2 in TP53-mediated tumor suppression. We now identify an oncogenic splicing variant, ASPP2κ, with high prevalence in acute leukemia. Methods: An mRNA screen to detect ASPP2 splicing variants was performed and ASPP2κ was validated using isoform-specific PCR approaches. Translation into a genuine protein isoform was evaluated after establishing epitope-specific antibodies. For functional studies cell models with forced expression of ASPP2κ or isoform-specific ASPP2κ-interference were created to evaluate proliferative, apoptotic and oncogenic characteristics of ASPP2κ. Findings: Exon skipping generates a premature stop codon, leading to a truncated C-terminus, omitting the TP53-binding sites. ASPP2κ translates into a dominant-negative protein variant impairing TP53-dependent induction of apoptosis. ASPP2κ is expressed in CD34+ leukemic progenitor cells and functional studies argue for a role in early oncogenesis, resulting in perturbed proliferation and impaired induction of apoptosis, mitotic failure and chromosomal instability (CIN) – similar to TP53 mutations. Importantly, as expression of ASPP2κ is stress-inducible it defines a novel class of dynamic oncogenes not represented by genomic mutations. Interpretation: Our data demonstrates that ASPP2κ plays a distinctive role as an antiapoptotic regulator of the TP53 checkpoint, rendering cells to a more aggressive phenotype as evidenced by proliferation and apoptosis rates – and ASPP2κ expression results in acquisition of genomic mutations, a first initiating step in leukemogenesis. We provide proof-of-concept to establish ASPP2κ as a clinically relevant biomarker and a target for molecule-defined therapy. Fund: Unrestricted grant support from the Wilhelm Sander Foundation for Cancer Research, the IZKF Program of the Medical Faculty Tübingen, the Brigitte Schlieben-Lange Program and the Margarete von Wrangell Program of the State Ministry Baden-Wuerttemberg for Science, Research and Arts and the Athene Program of the excellence initiative of the Eberhard-Karls University, Tübingen.

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