TERC suppresses PD-L1 expression by downregulating RNA binding protein HuR

Area of Science:

• Molecular Biology
• Cancer Research
• Immunology

Background:

• TERC is the RNA component of telomerase, essential for telomere synthesis.
• Emerging evidence suggests TERC has roles beyond telomerase function.
• PD-L1 is a key immune checkpoint protein often upregulated in cancer.

Purpose of the Study:

• To investigate the non-telomeric role of TERC in regulating PD-L1 expression.
• To elucidate the mechanism by which TERC influences PD-L1 levels.
• To explore therapeutic strategies involving TERC modulation for cancer treatment.

Main Methods:

• Correlation analysis of TERC expression with PD-L1 levels.
• Ectopic expression of TERC and TERT in ALT cells.
• Investigation of TERC's effect on PD-L1 mRNA stability and HuR expression.
• Treatment with the FoxO1 inhibitor AS1842856 and assessment of TERC and PD-L1 expression.

Main Results:

• TERC expression is negatively correlated with PD-L1 levels.
• Ectopic TERC, but not TERT, suppresses PD-L1 in ALT cells, indicating a telomerase-independent mechanism.
• TERC promotes PD-L1 mRNA degradation by inhibiting HuR, a protein stabilizing PD-L1 mRNA.
• The FoxO1 inhibitor AS1842856 increases TERC expression and counteracts chemotherapy-induced PD-L1 upregulation.

Conclusions:

• TERC suppresses PD-L1 expression through a novel, telomerase-independent pathway involving HuR and mRNA degradation.
• Modulating TERC expression via FoxO1 inhibition presents a promising therapeutic strategy to enhance cancer chemotherapy and prevent immune escape.