Naturally occurring neomorphic PIK3R1 mutations activate the MAPK pathway, dictating therapeutic response to MAPK pathway inhibitors

Cancer Cell. 2014 Oct 13;26(4):479-94. doi: 10.1016/j.ccell.2014.08.017. Epub 2014 Oct 2.


PIK3R1 (p85α regulatory subunit of PI3K) is frequently mutated across cancer lineages. Herein, we demonstrate that the most common recurrent PIK3R1 mutation PIK3R1(R348∗) and a nearby mutation PIK3R1(L370fs), in contrast to wild-type and mutations in other regions of PIK3R1, confers an unexpected sensitivity to MEK and JNK inhibitors in vitro and in vivo. Consistent with the response to inhibitors, PIK3R1(R348∗) and PIK3R1(L370fs) unexpectedly increase JNK and ERK phosphorylation. Surprisingly, p85α R348(∗) and L370fs localize to the nucleus where the mutants provide a scaffold for multiple JNK pathway components facilitating nuclear JNK pathway activation. Our findings uncover an unexpected neomorphic role for PIK3R1(R348∗) and neighboring truncation mutations in cellular signaling, providing a rationale for therapeutic targeting of these mutant tumors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use
  • Cell Nucleus / metabolism
  • Enzyme Activation
  • Humans
  • MAP Kinase Signaling System / drug effects*
  • Mutation*
  • Phosphatidylinositol 3-Kinases / genetics*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Protein Transport


  • Antineoplastic Agents
  • PIK3R1 protein, human
  • Phosphatidylinositol 3-Kinases