In vivo CRISPR screens identify a dual function of MEN1 in regulating tumor-microenvironment interactions

Area of Science:

• Oncology
• Genomics
• Immunology

Background:

• Two-dimensional (2D) cell culture models have limitations in identifying therapeutic targets impacting the tumor microenvironment.
• Understanding genes that influence tumor growth in vivo is crucial for developing effective cancer therapies.

Purpose of the Study:

• To identify therapeutic targets influencing the tumor microenvironment by comparing functional genomic screens in 2D cultures versus in vivo xenografts.
• To elucidate the mechanisms by which MEN1 affects tumor growth and immune cell infiltration.

Main Methods:

• Comparative CRISPR-Cas9 screens in 2D cultures and xenografts.
• MEN1 knockout in various solid cancer types.
• In vivo tumor growth assays in immunodeficient and immunocompetent mice.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to assess MLL1 occupancy and H3K4me3.
• Pharmacological inhibition of the menin-MLL interaction.

Main Results:

• MEN1 was identified as a top hit with differential effects in vitro and in vivo.
• MEN1 knockout did not affect in vitro proliferation but modulated tumor growth in mice.
• MEN1 knockout altered MLL1 chromatin occupancy, increased H3K4me3 at repetitive elements, and modulated dsRNA expression.
• MEN1 knockout promoted neutrophil and CD8+ T cell infiltration.
• Menin-MLL inhibition reduced tumor growth in a CD8+ T cell-dependent manner.

Conclusions:

• MEN1 exhibits context-dependent oncogenic and tumor-suppressive functions influenced by the tumor microenvironment.
• Targeting MEN1 offers a potential therapeutic strategy for solid cancers by modulating immune responses.