1245 - AARS1/2-Mediated Histone Lactylation Drives an Immunosuppressive Tumor Microenvironment and Represents a Novel Target to Enhance Anti-PD-1 Therapy

09:40am - 09:45am ET

Room 157

Presenter(s)

Rong Xiao, PhD - Shandong Cancer Hospital and Institute, Jinan, shandong

M. Liu¹, Z. Wang², J. Yuan³, B. Tian³, F. Wang³, Y. Xu³, H. Yuan¹, Y. Dong¹, J. Yu³, D. Chen³, and R. Xiao⁴; ¹Cancer Center, Shandong University, Jinan, Shandong, China, ²Shandong Second Medical University, Jinan, Shandong, China, ³Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, ⁴Shandong Cancer Hospital and Institute, Jinan, shandong, China

Purpose/Objective(s):

Lactate accumulation in the tumor microenvironment (TME) is a hallmark of cancer, driving immunosuppression and resistance to immunotherapy.Targeting lactate production via LDHA sensitizes tumors to immunotherapy, but clinical translation is hindered by toxicity. AARS1/2 were recently identified as direct lactate sensors. Here, we elucidate the mechanistic role of AARS1/2 in driving immunosuppression via epigenetic reprogramming and evaluate the translational potential of targeting this axis to enhance anti-PD-1 efficacy.

Materials/Methods:

We generated AARS1/2 double-knockout (DKO) tumor cells and established orthotopic/s.c. models in C57BL/6 mice treated with anti-PD-1. Tumors were analyzed by RNA-seq, flow cytometry, and histology. AARS1/2 lactyltransferase activity, H4K16la levels, and target gene regulation were assessed via western blot, ChIP-qPCR, and rescue assays. A peptide inhibitor of H4K16la was developed and tested alone/with PD-1 blockade in vivo. Clinical relevance was validated using multiplex IHC on specimens from immunotherapy responders vs. non-responders.

Results:

Analysis of our institutional cohort and TCGA data confirmed that high LDHA expression correlates with poor prognosis in patients receiving immunotherapy. This link was functionally mediated by lactate, as AARS1/2 DKO tumors—which exhibit disrupted lactate signaling—showed significantly enhanced sensitivity to PD-1 blockade in vivo compared to controls. Mechanistically, we identified AARS1/2 as critical lactonyl transferases. Their deletion globally reduced histone lactylation, with a pronounced effect on H4K16la. ChIP-qPCR and rescue experiments revealed that H4K16la directly regulates the transcription of Ccn1, a key immunomodulatory gene. Loss of AARS1/2 led to reduced H4K16la at the Ccn1 promoter, downregulating CCN1 expression. This downregulation promoted M1-like macrophage polarization via the NF-?B pathway, remodeling the TME from immunosuppressive to immunostimulatory. An H4K16la-targeting peptide mimicked this effect and, when combined with anti-PD-1, produced potent synergistic antitumor efficacy. Clinically, tumor H4K16la levels inversely correlated with M1 macrophage infiltration in immunotherapy responders.

Conclusion:

This study unveils a novel and targetable epigenetic-metabolic axis in cancer immunity. We establish AARS1/2 as key lactonyl transferases that drive an immunosuppressive TME by catalyzing H4K16la, which in turn promotes CCN1 expression and suppresses M1 macrophage polarization. Pharmacological targeting of this pathway with a novel H4K16la-inhibitory peptide robustly sensitizes tumors to PD-1 blockade, offering a promising new strategy to overcome immunotherapy resistance with high translational potential.