Decoding the response to a PP2A inhibitor in pancreatic cancer
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE300008 | GEO | 2026/06/18
REPOSITORIES: GEO
Dataset's files
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| GSE300008_RAW.tar | Raw | |||
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Project description:Pancreatic ductal adenocarcinoma (PDAC) remains a therapeutic challenge, with the aggressive basal-like/mesenchymal subtype demonstrating pronounced resistance to current standard-of-care chemotherapy. Novel, targeted therapeutic strategies are urgently needed to improve outcomes for these patients. Leveraging CRISPR-Cas9 screens, we identified PP2A’s catalytic subunit, PPP2CA, as a relevant PDAC target. Pharmacological PP2A inhibition (PP2Ai) selectively impaired mesenchymal PDAC growth. To delineate the molecular mechanisms underlying PP2Ai sensitivity, we employed a dual-pronged strategy. Functional characterization of mesenchymal PDAC cells revealed metabolic reprogramming, marked by suppressed oxidative phosphorylation and heightened autophagy, coupled with endoplasmic reticulum stress and subsequent apoptosis induction upon blockade of PP2A. Genome-wide CRISPR screens identified key genetic modifiers of PP2Ai sensitivity, revealing critical roles for transcriptional regulators, mRNA processing, translation, and metabolic pathways. Guided by human expression data implicating PP2A in splicing and transcriptional regulation, we prioritized these interconnected processes for orthogonal validation. Mesenchymal PDAC cells exhibited significantly enhanced splicing following PP2Ai treatment, with skipped exons (SE) representing the most prominently altered splicing event. Notably, we identified enhanced transcriptional elongation upon PP2A inhibition, particularly of short genes, driven by CDK9. Our findings establish a reciprocal regulatory relationship between PP2A and CDK9 that controls the activation of ER stress response factors, particularly the key transcriptional regulator ATF4. Our findings establish PP2A as a promising therapeutic target in mesenchymal PDAC and reveal its critical role in regulating transcriptional elongation. These insights enable both the precise application of PP2A inhibitors and the development of rational combination therapies.
2026-06-18 | GSE317590 | GEO
Project description:Oncogenic mutations in KRAS are present in approximately 95% of patients diagnosed with pancreatic ductal adenocarcinoma (PDAC) and are considered the initiating event during the development of pancreatic intraepithelial neoplasia (PanIN) precursor lesions. While it is well established that KRAS mutations can drive the initiation of pancreatic oncogenesis, the effects of oncogenic KRAS signaling on regulation of phosphatases during this process is not fully appreciated. Protein Phosphatase 2A (PP2A) has been implicated in suppressing KRAS-driven cellular transformation. However, low PP2A activity is observed in PDAC cells compared to non-transformed cells, suggesting that suppression of PP2A activity is an important step in the overall development of PDAC. In the current study, we demonstrate that KRASG12D induces the expression of both Cancerous Inhibitor of PP2A (CIP2A), an endogenous inhibitor of PP2A activity, and the PP2A target, c-MYC. Consistent with these findings, KRASG12D sequestered the specific PP2A subunit responsible for c-MYC degradation, B56a, away from the active PP2A holoenzyme in a CIP2A-dependent manner. During PDAC initiation in vivo, knockout of B56a promoted KRASG12D tumorigenesis by accelerating acinar-to-ductal metaplasia (ADM) and the formation of PanIN lesions. The process of ADM was attenuated ex vivo in response to pharmacological re-activation of PP2A utilizing direct small molecule activators of PP2A (SMAPs). Together, our results suggest that suppression of PP2A-B56a through KRAS signaling can promote Myc-driven initiation of pancreatic tumorigenesis.
2025-07-28 | GSE250099 | GEO
Project description:Oncogenic mutations in KRAS are present in approximately 95% of patients diagnosed with pancreatic ductal adenocarcinoma (PDAC) and are considered the initiating event during the development of pancreatic intraepithelial neoplasia (PanIN) precursor lesions. While it is well established that KRAS mutations can drive the initiation of pancreatic oncogenesis, the effects of oncogenic KRAS signaling on regulation of phosphatases during this process is not fully appreciated. Protein Phosphatase 2A (PP2A) has been implicated in suppressing KRAS-driven cellular transformation. However, low PP2A activity is observed in PDAC cells compared to non-transformed cells, suggesting that suppression of PP2A activity is an important step in the overall development of PDAC. In the current study, we demonstrate that KRASG12D induces the expression of both Cancerous Inhibitor of PP2A (CIP2A), an endogenous inhibitor of PP2A activity, and the PP2A target, c-MYC. Consistent with these findings, KRASG12D sequestered the specific PP2A subunit responsible for c-MYC degradation, B56a, away from the active PP2A holoenzyme in a CIP2A-dependent manner. During PDAC initiation in vivo, knockout of B56a promoted KRASG12D tumorigenesis by accelerating acinar-to-ductal metaplasia (ADM) and the formation of PanIN lesions. The process of ADM was attenuated ex vivo in response to pharmacological re-activation of PP2A utilizing direct small molecule activators of PP2A (SMAPs). Together, our results suggest that suppression of PP2A-B56a through KRAS signaling can promote Myc-driven initiation of pancreatic tumorigenesis.
2025-07-28 | GSE249867 | GEO
Project description:In this study, we discovered that CDK9-mediated, RNAPII-driven transcription is functionally opposed by a protein phosphatase 2A (PP2A) complex that is recruited to transcription sites by the Integrator complex subunit INTS6. PP2A dynamically antagonises phosphorylation of key CDK9 substrates including DSIF and RNAPII-CTD. Loss of INTS6 results in resistance to tumor cell death mediated by CDK9 inhibition, decreased turnover of CDK9 phospho-substrates and amplification of acute cell growth and pro-inflammatory transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill both leukemic and solid tumor cells, providing therapeutic benefit in vivo. These data demonstrate that finely-tuned gene expression relies on the balance of kinase and phosphatase activity throughout the transcription cycle.
2022-08-12 | PXD025060 | Pride
Project description:Gene expression by RNA Polymerase II (RNAPII) is tightly controlled by Cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The RNAPII pausing checkpoint, engaged after transcription initiation, is controlled by CDK9 to regulate transcription in metazoans. We discovered that CDK9-mediated RNAPII pause-release is functionally opposed by a protein phosphatase 2A (PP2A) complex. PP2A dynamically competes for key CDK9 substrates, DSIF and RNAPII-CTD, and is recruited to transcription pausing sites by the Integrator complex subunit INTS6. INTS6 depletion confers resistance to CDK9 inhibition in a variety of normal and tumor cell lines. Loss of INTS6 abolishes the Integrator-PP2A association leading to unrestrained CDK9 activity, which amplifies transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill MLL-rearranged leukemias and solid tumors and provide therapeutic benefit in vivo. These data demonstrate that f inely-tuned gene expression relies on the balance of kinase and phosphatase activity at the pausing checkpoint.
2021-05-23 | GSE163804 | GEO
Project description:Gene expression by RNA Polymerase II (RNAPII) is tightly controlled by Cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The RNAPII pausing checkpoint, engaged after transcription initiation, is controlled by CDK9 to regulate transcription in metazoans. We discovered that CDK9-mediated RNAPII pause-release is functionally opposed by a protein phosphatase 2A (PP2A) complex. PP2A dynamically competes for key CDK9 substrates, DSIF and RNAPII-CTD, and is recruited to transcription pausing sites by the Integrator complex subunit INTS6. INTS6 depletion confers resistance to CDK9 inhibition in a variety of normal and tumor cell lines. Loss of INTS6 abolishes the Integrator-PP2A association leading to unrestrained CDK9 activity, which amplifies transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill MLL-rearranged leukemias and solid tumors and provide therapeutic benefit in vivo. These data demonstrate that f inely-tuned gene expression relies on the balance of kinase and phosphatase activity at the pausing checkpoint.
2021-05-23 | GSE163803 | GEO
Project description:Gene expression by RNA Polymerase II (RNAPII) is tightly controlled by Cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The RNAPII pausing checkpoint, engaged after transcription initiation, is controlled by CDK9 to regulate transcription in metazoans. We discovered that CDK9-mediated RNAPII pause-release is functionally opposed by a protein phosphatase 2A (PP2A) complex. PP2A dynamically competes for key CDK9 substrates, DSIF and RNAPII-CTD, and is recruited to transcription pausing sites by the Integrator complex subunit INTS6. INTS6 depletion confers resistance to CDK9 inhibition in a variety of normal and tumor cell lines. Loss of INTS6 abolishes the Integrator-PP2A association leading to unrestrained CDK9 activity, which amplifies transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill MLL-rearranged leukemias and solid tumors and provide therapeutic benefit in vivo. These data demonstrate that f inely-tuned gene expression relies on the balance of kinase and phosphatase activity at the pausing checkpoint.
2021-05-23 | GSE163802 | GEO
Project description:Gene expression by RNA Polymerase II (RNAPII) is tightly controlled by Cyclindependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The RNAPII pausing checkpoint, engaged after transcription initiation, is controlled by CDK9 to regulate transcription in metazoans. We discovered that CDK9-mediated RNAPII pause-release is functionally opposed by a protein phosphatase 2A (PP2A) complex. PP2A dynamically competes for key CDK9 substrates, DSIF and RNAPIICTD, and is recruited to transcription pausing sites by the Integrator complex subunit INTS6. INTS6 depletion confers resistance to CDK9 inhibition in a variety of normal and tumor cell lines. Loss of INTS6 abolishes the Integrator-PP2A association leading to unrestrained CDK9 activity, which amplifies transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill MLLrearranged leukemias and solid tumors and provide therapeutic benefit in vivo. These data demonstrate that finely-tuned gene expression relies on the balance of kinase and phosphatase activity at the pausing checkpoint.
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Project description:CDK9 is a kinase critical for the productive transcription of protein-coding genes by RNA polymerase II (pol II). As part of P-TEFb, CDK9 phosphorylates the carboxyl-terminal domain (CTD) of pol II and elongation factors, which allows pol II to elongate past the early elongation checkpoint (EEC) encountered soon after initiation. We show that, in addition to halting pol II at the EEC, loss of CDK9 activity causes premature termination of transcription across the last exon, loss of polyadenylation factors from chromatin, and loss of polyadenylation of nascent transcripts. Inhibition of the phosphatase PP2A abrogates the premature termination and loss of polyadenylation caused by CDK9 inhibition, indicating that this kinase/phosphatase pair regulates transcription elongation and RNA processing at the end of protein-coding genes. We also confirm the splicing factor SF3B1 as a target of CDK9 and show that SF3B1 in complex with polyadenylation factors is lost from chromatin after CDK9 inhibition. These results emphasize the important roles that CDK9 plays in coupling transcription elongation and termination to RNA maturation downstream of the EEC.
2022-08-22 | GSE176541 | GEO