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Oncogenic Alterations in PI3K Signaling Emulated Optogenetically Recapitulate Some Phenotypic Changes in Mammary
Keith A Gagnon1,2, Veronica W Hui1,3, Terry Ching1,2,4
1Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, United States.
Abstract:
Cancer is known to be a disease of altered cellular signaling; however, the relationship between mutation-specific changes to signal transduction and the phenotypic consequences produced remains poorly understood. Here, we investigate two common breast cancer driver mutations, the PIK3CAH1047R mutation and the ErbB2 amplification, both of which activate the PI3K-Akt pathway but paradoxically drive distinct cellular outcomes. Indeed, in nontransformed mammary epithelial cells, PI3KH1047R expression induced features of epithelial-mesenchymal transition (EMT), while ErbB2amp cells exhibited a hyperproliferative phenotype. Characterization of PI3K axis signaling revealed that ErbB2amp cells display prolonged, stimulus-dependent PI3K activation, whereas PI3KH1047R cells show constitutive, ligand-independent signaling. To test whether these distinct dynamics contribute to the phenotypic responses, we employed an iLID-based optogenetic system that enables precise, tunable control of endogenous PI3K activity. Using this tool to mimic the mutation-specific dynamics in MCF10A mammary epithelial cells, we found that PI3K signaling patterns alone were sufficient to reproduce key features of the PIK3CA H1047R-associated EMT phenotype but not the ErbB2-associated proliferative phenotype. These findings suggest that the temporal encoding of pathway activity, not merely its magnitude, can drive some phenotypic changes in oncogenic progression, explain how distinct mutations within a common signaling pathway can produce divergent cellular phenotypes, and provide a workflow for interrogating the functional consequences of changes in signaling dynamics.
Insights
Distinct breast cancer mutations activate the same pathway but cause different cell behaviors. Signaling patterns, not just strength, can drive these divergent outcomes, impacting cancer progression.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Cancer involves altered cellular signaling, but links between specific mutations, signal transduction, and cell phenotypes are unclear.
- Two common breast cancer mutations, PIK3CA H1047R and ErbB2 amplification, activate the PI3K-Akt pathway but yield different cellular outcomes.
Purpose of the Study:
- Investigate how distinct mutations in the PI3K-Akt pathway lead to different cellular phenotypes in breast cancer.
- Determine if the temporal dynamics of PI3K pathway activation, rather than just magnitude, influence phenotypic consequences.
Main Methods:
- Utilized an optogenetic system (iLID) for precise, tunable control of PI3K pathway activity in mammary epithelial cells.
- Expressed PIK3CA H1047R mutation or ErbB2 amplification in MCF10A cells to compare signaling dynamics and phenotypes.
- Mimicked mutation-specific PI3K signaling dynamics using optogenetics to assess their sufficiency in driving phenotypes.
Main Results:
- PIK3CA H1047R expression induced epithelial-mesenchymal transition (EMT) features, while ErbB2 amplification caused hyperproliferation.
- PIK3CA H1047R cells showed constitutive PI3K activation, whereas ErbB2 amplified cells displayed prolonged, stimulus-dependent activation.
- Optogenetic mimicry of PI3K signaling patterns reproduced EMT features associated with PIK3CA H1047R but not the proliferative phenotype of ErbB2 amplification.
Conclusions:
- Temporal patterns of PI3K pathway activity, not solely its magnitude, can drive distinct phenotypic changes in oncogenic progression.
- Explains how different mutations within a shared signaling pathway can result in divergent cellular phenotypes.
- Provides a novel optogenetic workflow for studying the functional impact of signaling dynamics in cancer.
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