CRTC1 Enhances PD-L1-Mediated Tumor Immunosuppression in Non-Small Cell Lung Cancer via the Notch1/Akt Signaling Pathway

Xujun Feng^1,2,3Yuan Shi¹Fang Yuan²Yanxia Hu²Xiangdong Tang¹Wei Zhang³Jiadi Gan^1*Longhua Sun^3*Lingling Cao^2*

• ¹West China School of Medicine, West China Hospital, Sichuan University, Chengdu, China
• ²The First Hospital of Jiujiang, Jiujiang, China
• ³The First Affiliated Hospital, Jiangxi Medical College, Nanchang University, Nanchang, China

Background: While programmed death-ligand 1 (PD-L1)-targeted immunotherapy represents an advancement in non-small cell lung cancer (NSCLC), patient outcomes remain suboptimal. Aberrant activation of the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB)-regulated transcription coactivator (CRTC) is linked to malignant proliferation and functionality in lung cancer cells. This study investigates the involvement of CRTC1 in tumor immunity. Methods: CRTC1 and Notch1 expression were regulated in A549 and NCI-H1299 NSCLC lines through plasmid-mediated overexpression/silencing to assess their effects on cell viability, apoptosis, migration, and invasion. CRTC1/Notch1-dysregulated Lewis lung carcinoma (LLC) cells were co-cultured with T cells to evaluate T cell activation and function. The efficacy of combined CRTC1 knockdown/overexpression and atezolizumab (anti-PD-L1) was tested in an LLC xenograft mouse model. Results: CRTC1 promoted cell viability, migration, and invasion while suppressing apoptosis across NSCLC models. In LLC cells, CRTC1 upregulated tumor cell PD-L1 expression, suppressed T cell-derived IFN-γ and IL-2 production, diminished endogenous CXCL10/11 secretion, and impaired T cell proliferation and cytotoxicity. Mechanistically, CRTC1 interacted with Notch1 to activate the Notch1/Akt pathway, stimulating PD-L1 upregulation, thereby facilitating tumor immunosuppression and growth. Notably, CRTC1 overexpression reversed the protective effects of atezolizumab on tumor growth. Combining CRTC1 knockdown with atezolizumab synergistically enhanced anti-tumor T cell immunity, achieving the most significant tumor regression in xenografts. Conclusion: These findings indicate that CRTC1 in tumor cells suppresses PD-L1-mediated anti-tumor immunity and promotes tumorigenesis via the Notch1/Akt signaling axis. Dual targeting of CRTC1 and PD-L1 demonstrates therapeutic synergy, suggesting CRTC1 pathway inhibition could optimize immunotherapy outcomes in NSCLC patients.