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Effect of Okadaic Acid on gene expression in human pancreatic cells

ABSTRACT: Pancreatic ductal adenocarcinoma (PDAC) has a bad prognosis, a fast progression and is difficult to treat, highlighting the need for new therapeutic targets. Aggressive tumors mostly show Epithelial-to-Mesenchymal Transition (EMT). Protein phosphatase type 2A (PP2A) plays a central role in processes of cell survival and proliferation, but the link with EMT and tumor progression is largely unknown. Therefore, we examined expression of a PP2A gene set in five datasets of human PDAC and their association with an aggressive phenotype. Two datasets included PDAC tumor samples and normal pancreatic tissue. In two other datasets, the samples could be classified into clinical/molecular subtypes of EMT-high/aggressive and EMT-low/moderate PDAC. Spearman correlation, hierarchical clustering and ROC-analysis were performed. EMT was also quantified using weighted expression of 8 marker genes. In each study we observed that, compared to normal tissue, (advanced) tumor stage positively and significantly correlated with EMT. EMT-high PDAC showed suppression of PPP2R1B and PPP2R2D expression and upregulation of PPP2R3C, PPP2R5E, STRN, STRN3 and PPP2R2A. A strong link was further found for upregulation of endogenous inhibitors of PP2A (KIAA1524/CIP2A, ARPP19, TIPRL and PPME1) with advanced PDAC. ROC-curve indicates that high expression of PP2A-inhibitors are predictors of aggressive PDAC. This was further investigated in a cell line model of Panc-1 cells made resistant to the PP2A-inhibitor Okadaic acid. Gene expression was determined in cells exposed for 24 hours and resistant cells. In summary, we demonstrate an important association of PP2A inhibition with EMT in advanced human pancreatic cancer. We then performed gene expression profiling analysis using data obtained from RNA-seq of 3 different cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE216036 | GEO | 2023/05/16

REPOSITORIES: GEO

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Project description:Background Pancreatic ductal adenocarcinoma (PDAC) tends to undergo distant metastasis, especially liver metastasis, leading to a poor prognosis. Metabolic remodelling and epigenetic reprogramming are two important hallmarks of malignant tumours and participate in regulating PDAC tumorigenesis and metastasis. However, the interaction between these two processes during PDAC metastasis has not been fully elucidated. Methods We performed metabolomics analysis to identify the critical metabolites associated with PDAC liver metastasis and focused on guanidinoacetic acid (GAA). Intracellular GAA content was significantly increased in liver metastatic PDAC cells compared to primary cancer cells in mouse xenograft tumour models. The effects of GAA supplementation and glycine amidinotransferase (GATM) knockdown on PDAC metastasis were assessed by analysing cell migration, filopodia formation, epithelial-mesenchymal transition (EMT), and in vivo metastasis in different cell and animal models. Next, ChIP‒qPCR, 3C‒qPCR, and CRISPRi/dCas9-KRAB experiments were used to validate the “epigenome-metabolome" mechanism. Finally, the results of in vitro approaches, including RNA-seq, CUT&RUN, RT‒qPCR, and western blot analyses, as well as luciferase reporter gene assay and transwell assay, revealed the GAA-c-Myc-HMGA axis and transcription-activating histone modifications reprogramming. Results A high level of intracellular GAA was associated with PDAC liver metastasis. GAA could promote the migration, EMT, and liver metastasis of pancreatic cancer cells in vitro and in vivo. Next, we explored the role of GATM-mediated de novo GAA synthesis in pancreatic cancer metastasis. High expression of GATM was positively correlated with advanced N stage in PDAC. Knockdown of GATM significantly reduced the intracellular level of GAA, suppressed EMT, and inhibited PDAC liver metastasis, and these effects were attenuated by GAA supplementation. Mechanistically, we identified the active enhancers looped to the GATM gene locus that promoted GATM expression and PDAC liver metastasis. Furthermore, we found that GAA promoted cell migration and EMT by regulating c-Myc-mediated high mobility group AT-hook protein expression. Moreover, GAA increased the H3K4me3 modification level by upregulating histone methyltransferases, which induced the transcription of metastasis-related genes, including MYC. Conclusions These findings revealed the critical role of the epigenome-metabolome interaction in regulating PDAC liver metastasis and suggested potential therapeutic strategies targeting GAA metabolism and epigenetic regulatory mechanisms.

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Effect of Okadaic Acid on gene expression in human pancreatic cells

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