C71-27 Overexpression of the Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A) Enhances Extracellular Matrix Remodeling and Inflammatory Responses in Lung Fibroblasts

Abstract Background, Introduction, or Rationale The activity of protein phosphatase 2A (PP2A), a serine-threonine phosphatase, is reduced in the lung fibroblasts of patients with idiopathic pulmonary fibrosis (IPF). Chemical reactivation of PP2A can reduce bleomycin-induced fibrosis in mouse models. However, the mechanism underlying reduced PP2A activity in IPF remains unknown. Objective or Hypothesis The objective of this study was to determine whether the endogenous PP2A inhibitor, cancerous inhibitor of PP2A (CIP2A), suppresses PP2A activity and enhances fibrotic signaling in lung fibroblasts. Materials and/or Methods CIP2A was overexpressed in primary lung fibroblasts using lentiviral technology. RNA sequencing was performed to evaluate changes in gene expression following CIP2A overexpression. Several targets identified by RNA sequencing were validated by PCR and Western blotting. Fibroblasts were treated with inhibitors targeting Akt, ERK, and SMAD3. Results and/or Discussion Immuno-precipitation of PP2A from fibroblasts isolated from healthy and IPF subjects suggested increased binding of PP2A to CIP2A in IPF samples. Silencing CIP2A expression enhanced PP2A responses in fibroblasts from IPF subjects.Transcriptome analysis of fibroblasts overexpressing CIP2A identified approximately 600 differentially expressed genes. Gene Ontology (GO) analysis identified multiple functional pathways significantly altered by CIP2A overexpression, including inflammatory responses, cell adhesion, regulation of cell migration, and extracellular matrix remodeling. Confirmational analysis demonstrated that CIP2A overexpression significantly upregulated the fibrotic markers COL1A1 and CTHRC1 and inflammation mediators IL1B, IL8, and CCL27. CIP2A overexpression also inhibited PP2A activity and enhanced phosphorylation of ERK, Akt, and SMAD3. Chemical inhibition of SMAD3, Akt, and ERK markedly reduced CIP2A-driven COL1A1 and CTHRC1 expression. Conclusions This study indicates that CIP2A negatively regulates PP2A activity in lung fibroblasts while modulating multiple processes, including inflammatory responses, cell adhesion, cell migration, and extracellular matrix remodeling. This abstract is funded by: A grant made available to M.O. and P.G. (the Department of Defense (W81XWH-20-1-0494)).