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Targeting PP2A for cancer therapeutic modulation.

ABSTRACT: Protein phosphatases play essential roles as negative regulators of kinases and signaling cascades involved in cytoskeletal organization. Protein phosphatase 2A (PP2A) is highly conserved and is the predominant serine/threonine phosphatase in the nervous system, constituting more than 70% of all neuronal phosphatases. PP2A is involved in diverse regulatory functions, including cell cycle progression, apoptosis, and DNA repair. Although PP2A has historically been identified as a tumor suppressor, inhibition of PP2A has paradoxically demonstrated potential as a therapeutic target for various cancers. LB100, a water-soluble, small-molecule competitive inhibitor of PP2A, has shown particular promise as a chemo- and radio-sensitizing agent. Preclinical success has led to a profusion of clinical trials on LB100 adjuvant therapies, including a phase I trial in extensive-stage small-cell lung cancer, a phase I/II trial in myelodysplastic syndrome, a phase II trial in recurrent glioblastoma, and a completed phase I trial assessing the safety of LB100 and docetaxel in various relapsed solid tumors. Herein, we review the development of LB100, the role of PP2A in cancer biology, and recent advances in targeting PP2A inhibition in immunotherapy.

SUBMITTER: Ronk H

PROVIDER: S-EPMC9630519 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Targeting PP2A for cancer therapeutic modulation.

Ronk Halle H Rosenblum Jared S JS Kung Timothy T Zhuang Zhengping Z

Cancer biology & medicine 20221101 10

Protein phosphatases play essential roles as negative regulators of kinases and signaling cascades involved in cytoskeletal organization. Protein phosphatase 2A (PP2A) is highly conserved and is the predominant serine/threonine phosphatase in the nervous system, constituting more than 70% of all neuronal phosphatases. PP2A is involved in diverse regulatory functions, including cell cycle progression, apoptosis, and DNA repair. Although PP2A has historically been identified as a tumor suppressor, ...[more]

PMID: 36342229

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Project description:Mutations in spliceosomal genes are commonly found in patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). These mutations occur at highly restricted amino acid residues and perturb normal splice site and exon recognition. Spliceosomal mutations are always heterozygous and rarely co-occur with one another, suggesting that cells may only tolerate a partial deviation from normal splicing activity. To test this hypothesis, we generated mice with inducible hemizygous expression of the commonly occurring SRSF2P95H mutation in the hematopoietic system. These mice rapidly developed lethal bone marrow failure upon activation of the Srsf2P95H mutation with concomitant deletion of the wildtype Srsf2 allele, demonstrating that Srsf2-mutant cells depend on the wildtype Srsf2 allele for survival. We next tested whether spliceosomal-mutant leukemias display greater sensitivity to pharmacologic splicing inhibition induced by the small molecule E7107. Treatment of isogenic murine leukemias as well as patient-derived xenograft (PDX) AMLs showed significant reductions in leukemic burden specifically in samples carrying spliceosomal mutations. Collectively, these data provide genetic and pharmacologic evidence that leukemias with spliceosomal mutations are preferentially susceptible to additional splicing perturbations in vivo compared with wildtype counterparts. Modulation of spliceosome function may provide a novel therapeutic avenue in genetically defined subsets of MDS/AML patients. We created an isogenic murine leukemia model by retroviral overexpression of the MLL-AF9 fusion oncogene in Vav-Cre Srsf2+/+ or Vav-Cre Srsf2P95H/+ BM cells followed by transplantation into lethally irradiated recipient mice. In order to determine the mechanistic origins of the Srsf2 mutant-selective effects of E7107, we analyzed transcriptional changes after five consecutive days of E7107 or vehicle treatment in vivo. GFP+ Cd11b+ cells were purified from the BM of recipient mice exactly three hours after the last dose of E7107 and were subjected to paired-end 2x50bp RNA-seq. For the knock-in/knock-out experiments, we generated inducible, hemizygous Srsf2P95H mice to study the effects of wildtype Srsf2 deletion with concomitant activation of the Srsf2P95H allele. Mx1-cre Srsf2fl/+ mice were crossed to Srsf2P95H/+ mice to generate Srsf2 wildtype (Mx1-cre Srsf2+/+), Srsf2 heterozygous knockout (Mx1-Cre Srsf2+/-), Srsf2 heterozygous P95H mutant (Mx1-Cre Srsf2P95H/+), and Srsf2 hemizygous P95H mutant (Mx1-Cre Srsf2P95H/-) mice, which were subjected to single-end 101bp RNA-seq.

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Targeting PP2A for cancer therapeutic modulation.

Publications

Targeting PP2A for cancer therapeutic modulation.

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