Genome-wide CRISPR screens define determinants of epithelial-mesenchymal transition mediated immune evasion by...

Area of Science:

• Cancer Biology
• Immunology
• Genetics

Background:

• Epithelial mesenchymal plasticity (EMP) is crucial for cancer cell immune evasion.
• Mesenchymal-like (Mes) cancer cells exhibit enhanced resistance to cytotoxic T lymphocyte (CTL)-mediated killing compared to epithelial-like (Epi) cells.
• The specific genetic mechanisms underlying this immune evasion remain largely unknown.

Purpose of the Study:

• To elucidate the molecular underpinnings of CTL resistance in Mes pancreatic cancer cells.
• To identify Mes-specific regulators of cytotoxicity and immune escape.

Main Methods:

• Utilized parallel genome-wide CRISPR screens to compare Mes and Epi KPC3 pancreatic cancer cells.
• Validated identified genes (e.g., Egfr, Mfge8) through expression analysis and functional assays.
• Assessed the impact of gene depletion on CTL-mediated killing and T cell function.

Main Results:

• Identified core CTL-evasion genes (e.g., IFN-γ pathway) present in both cell types.
• Discovered Mes-specific regulators, including Egfr and Mfge8, with significantly higher expression in Mes cells.
• Demonstrated that Egfr and Mfge8 depletion sensitized Mes cells to CTL killing.
• Showed that Mes cells secrete Mfge8 to inhibit CD8+ T cell proliferation and cytokine production (IFN-γ, TNFα).

Conclusions:

• Mesenchymal-like cancer cells employ both intrinsic (Egfr) and extrinsic (Mfge8) mechanisms to evade CD8+ T cell-mediated immune surveillance.
• Elevated Egfr and Mfge8 expression correlates with poorer clinical prognosis in pancreatic cancer patients.
• Targeting Egfr and Mfge8 may represent a therapeutic strategy to overcome immune escape in pancreatic cancer.