Components of the phosphatidylserine endoplasmic reticulum to plasma membrane transport mechanism as targets for KRAS inhibition in pancreatic cancer.

Abstract

KRAS is mutated in 90% of human pancreatic ductal adenocarcinomas (PDACs). To function, KRAS must localize to the plasma membrane (PM) via a C-terminal membrane anchor that specifically engages phosphatidylserine (PtdSer). This anchor-binding specificity renders KRAS-PM localization and signaling capacity critically dependent on PM PtdSer content. We now show that the PtdSer lipid transport proteins, ORP5 and ORP8, which are essential for maintaining PM PtdSer levels and hence KRAS PM localization, are required for KRAS oncogenesis. Knockdown of either protein, separately or simultaneously, abrogated growth of KRAS-mutant but not KRAS-wild-type pancreatic cancer cell xenografts. ORP5 or ORP8 knockout also abrogated tumor growth in an immune-competent orthotopic pancreatic cancer mouse model. Analysis of human datasets revealed that all components of this PtdSer transport mechanism, including the PM-localized EFR3A-PI4KIIIα complex that generates phosphatidylinositol-4-phosphate (PI4P), and endoplasmic reticulum (ER)-localized SAC1 phosphatase that hydrolyzes counter transported PI4P, are significantly up-regulated in pancreatic tumors compared to normal tissue. Taken together, these results support targeting PI4KIIIα in KRAS-mutant cancers to deplete the PM-to-ER PI4P gradient, reducing PM PtdSer content. We therefore repurposed the US Food and Drug Administration-approved hepatitis C antiviral agent, simeprevir, as a PI4KIIIα inhibitor In a PDAC setting. Simeprevir potently mislocalized KRAS from the PM, reduced the clonogenic potential of pancreatic cancer cell lines in vitro, and abrogated the growth of KRAS-dependent tumors in vivo with enhanced efficacy when combined with MAPK and PI3K inhibitors. We conclude that the cellular ER-to-PM PtdSer transport mechanism is essential for KRAS PM localization and oncogenesis and is accessible to therapeutic intervention.

• Authors: Walaa E Kattan, Junchen Liu, Dina Montufar-Solis, Hong Liang, Bhargavi Brahmendra Barathi, Ransome van der Hoeven, Yong Zhou, John F Hancock
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 118 Issue 51 (12 21 2021) ISSN: 1091-6490 [Electronic] United States
• PMID: 34903667 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• Antineoplastic Agents
• EFR3A protein, human
• KRAS protein, human
• Phosphatidylserines
• Protease Inhibitors
• Receptors, Steroid
• oxysterol binding protein
• Simeprevir
• 1-Phosphatidylinositol 4-Kinase
• PI4KIIIalpha protein, human
• Proto-Oncogene Proteins p21(ras)

Topics

• 1-Phosphatidylinositol 4-Kinase (antagonists & inhibitors, genetics, metabolism)
• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Animals
• Antineoplastic Agents (pharmacology)
• Biological Transport (drug effects)
• Cell Line, Tumor
• Cell Membrane (metabolism)
• Drug Delivery Systems
• Endoplasmic Reticulum (metabolism)
• Gene Knockdown Techniques
• Humans
• Mice
• Mice, Nude
• Phosphatidylserines (metabolism)
• Protease Inhibitors (pharmacology)
• Proto-Oncogene Proteins p21(ras) (antagonists & inhibitors, genetics, metabolism)
• Receptors, Steroid (genetics, metabolism)
• Simeprevir (pharmacology)
• Xenograft Model Antitumor Assays