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Mutant KRAS promotes CIP2A-mediated suppression of PP2A-B56a to initiate development of pancreatic ductal adenocarcinoma

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posted on 2023-08-02, 19:08 authored by Samantha Lauren TinsleySamantha Lauren Tinsley

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, the results of this study suggest that suppression of PP2A-B56a through KRAS signaling can promote Myc-driven initiation of pancreatic tumorigenesis.

Funding

MYC is a critical downstream effector in KRAS-driven pancreatic cancer

National Cancer Institute

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The role of PP2A B56a in pancreatic tumorigenesis

National Cancer Institute

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SIRG Graduate Research Assistantship, Purdue University Institute of Cancer Research

Ross-Lynn Research Scholars Grant, Purdue University Department of Biological Sciences

Frederick N. Andrews Recruitment Fellowship, Purdue University Graduate School

History

Degree Type

  • Doctor of Philosophy

Department

  • Biological Sciences

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Brittany L. Allen-Petersen

Additional Committee Member 2

Emily C. Dykhuizen

Additional Committee Member 3

Zhong-Yin Zhang

Additional Committee Member 4

R. Claudio Aguilar

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