Investigation of PP2A and Its Endogenous Inhibitors in Neuroblastoma Cell Survival and Tumor Growth

Abstract

High-risk neuroblastoma continues to carry a poor prognosis. Nearly 50% of these tumors relapse following extensive treatment regimens. Protein phosphatase 2A (PP2A), a tumor suppressor, has been shown to be downregulated in many human cancers via multiple mechanisms including upregulation of its endogenous inhibitors, I2PP2A or CIP2A. We hypothesized that inhibition of the endogenous PP2A inhibitors or activation of PP2A would decrease tumorigenicity in human neuroblastoma cells. Four human neuroblastoma cell lines were utilized. Expression of PP2A and its endogenous inhibitors I2PP2A and CIP2A was confirmed by immunoblotting. PP2A activation was measured via phosphatase activation assay. Multiple parallel methods including siRNA inhibition of the endogenous PP2A inhibitors and pharmacologic activation of PP2A were utilized. Cell viability, proliferation, migration, and invasion assays were performed. In vivo studies were utilized to determine the effects of PP2A activation on neuroblastoma tumor growth. Inhibition of the endogenous inhibitors of PP2A or pharmacologic activation of PP2A with the PP2A activator FTY720 led to decreased neuroblastoma cell viability, proliferation, migration, and invasion. Treatment of mice bearing SK-N-AS or SK-N-BE(2) neuroblastoma tumors with FTY720 resulted in a significant decrease in tumor growth compared to vehicle-treated animals. In conclusion, activation of PP2A may provide a novel therapeutic target for neuroblastoma.

A diazeniumdiolate-based NO donor induces apoptosis by modulating the CIP2A/PP2A/ERK signaling axis

“…The present results indicated JS-K stimulated a signi cant enhancement of PP2A activity. Several studies indicate that PP2A can dephosphorylate and inactivate both MEK and ERK proteins while PP2A inhibitors OA can induce MEK and ERK1/2 phosphorylation [4,5,22]. The present results demonstrated that PP2A suppression could antagonize the inhibition effect of JS-K on the ERK signaling pathway including dephosphorylation of MEK, ERK, Elk-1, c-Myc, and c-Fos.…”

A diazeniumdiolate-based NO donor induces apoptosis by modulating the CIP2A/PP2A/ERK signaling axis

“…The present results indicated JS-K stimulated a signi cant enhancement of PP2A activity. Several studies indicate that PP2A can dephosphorylate and inactivate both MEK and ERK proteins while PP2A inhibitors OA can induce MEK and ERK1/2 phosphorylation [23][24][25]. The present results demonstrated that PP2A suppression could antagonize the inhibition effect of JS-K on the ERK signaling pathway including dephosphorylation of MEK, ERK, Elk-1, c-Myc, and c-Fos.…”

Metabolomics-transcriptomics joint analysis: unveiling the dysregulated cell death network and developing a diagnostic model for high-grade neuroblastoma

“…A cluster analysis heatmap ( Figure 3C ) was employed to visually depict the top 100 differentially expressed genes, facilitating a more comprehensive understanding of the distinctions between HG-NB and LG-NB groups, thereby highlighting their significant differences. Based on the transcriptome results and relevant literature on NB ( 22 – 27 ), we selected 6 reported differentially expressed genes, namely MGST1 , SERPINE1 , IGF2 , CIP2A , CHL1 , and ERBB3 for RT-PCR validation. Our RT-PCR results demonstrated that the relative expressions of MGST1 , SERPINE1 , IGF2 , and CIP2A were significantly increased in HG-NB compared to LG-NB, while the relative expressions of CHL1 and ERBB3 were significantly decreased in HG-NB compared to LG-NB.…”