Protein phosphatase 1 regulatory subunit 1A in ewing sarcoma tumorigenesis and metastasis

• Published in: Oncogene Vol. 37; no. 6; pp. 798 - 809
• Main Authors: Luo, W, Xu, C, Ayello, J, Dela Cruz, F, Rosenblum, J M, Lessnick, S L, Cairo, M S
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08-02-2018; Nature Publishing Group
• Subjects: 38; 38/39; 38/77; 45; 45/91; 631/67/1798; 631/67/322; 64; 64/60; 82; 96; Animals; Apoptosis; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Bone Neoplasms - genetics; Bone Neoplasms - metabolism; Bone Neoplasms - secondary; Cancer metastasis; Care and treatment; Cell Adhesion; Cell Biology; Cell migration; Cell Movement; Cell Proliferation; Cell Transformation, Neoplastic - genetics; Cell Transformation, Neoplastic - metabolism; Cell Transformation, Neoplastic - pathology; Development and progression; Dopamine and cAMP-Regulated Phosphoprotein 32 - genetics; Dopamine and cAMP-Regulated Phosphoprotein 32 - metabolism; Ewing's sarcoma; Ewings sarcoma; Female; Gene Expression Regulation, Neoplastic; Genetic aspects; Genetic transformation; Health aspects; Human Genetics; Humans; Internal Medicine; Kinases; Medicine; Medicine & Public Health; Metastases; Metastasis; Mice; Mice, Inbred NOD; Mice, SCID; Molecular modelling; Neurogenesis; Oncology; original-article; Pathogenesis; Phosphatase; Phosphatases; Phosphoprotein phosphatase; Phosphorylation; Protein kinase A; Protein phosphatase; Protein phosphatase inhibitors; Proteins; Ribonucleic acid; Risk factors; RNA; Sarcoma, Ewing - genetics; Sarcoma, Ewing - metabolism; Sarcoma, Ewing - pathology; Tumor Cells, Cultured; Tumorigenesis; Xenograft Model Antitumor Assays; Xenografts; Zinc Finger E-box Binding Homeobox 2 - genetics; Zinc Finger E-box Binding Homeobox 2 - metabolism
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2017.378

Protein phosphatase inhibitors are often considered as tumor promoters. Protein phosphatase 1 regulatory subunit 1A (PPP1R1A) is a potent protein phosphatase 1 (PP1) inhibitor; however, its role in tumor development is largely undefined. Here we characterize, for the first time, the functions of PPP1R1A in Ewing sarcoma (ES) pathogenesis. We found that
PPP1R1A
is one of the top ranked target genes of EWS/FLI, the master regulator of ES, and is upregulated by EWS/FLI via a GGAA microsatellite enhancer element. Depletion of PPP1R1A resulted in a significant decrease in oncogenic transformation and cell migration
in vitro
as well as xenograft tumor growth and metastasis in an orthotopic mouse model. RNA-sequencing and functional annotation analyses revealed that PPP1R1A regulates genes associated with various cellular functions including cell junction, adhesion and neurogenesis. Interestingly, we found a significant overlap of PPP1R1A-regulated gene set with that of ZEB2 and EWS, which regulates metastasis and neuronal differentiation in ES, respectively. Further studies for characterization of the molecular mechanisms revealed that activation of PPP1R1A by PKA phosphorylation at Thr35, and subsequent PP1 binding and inhibition, was required for PPP1R1A-mediated tumorigenesis and metastasis, likely by increasing the phosphorylation levels of various PP1 substrates. Furthermore, we found that a PKA inhibitor impaired ES cell proliferation, tumor growth and metastasis, which was rescued by the constitutively active PPP1R1A. Together, these results offered new insights into the role and mechanism of PPP1R1A in tumor development and identified an important kinase and phosphatase pathway, PKA/PPP1R1A/PP1, in ES pathogenesis. Our findings strongly suggest a potential therapeutic value of inhibition of the PKA/PPP1R1A/PP1 pathway in the treatment of primary and metastatic ES.