Targeting serotonin-driven histone serotonylation suppresses lineage plasticity and progression of NEPC

Neuroendocrine prostate cancer (NEPC) is an aggressive, therapy-resistant subtype of prostate cancer characterized by lineage plasticity. While metabolic and signaling molecules are increasingly recognized as modulators of tumor progression, their role in cell fate transition remains unclear. NEPC tumors produce and accumulate serotonin (5-HT), a neurotransmitter that regulates diverse physiological processes. Here, we identify a tumor-intrinsic 5-HT axis as a key driver of NEPC lineage commitment and progression. NEPC endogenously synthesize serotonin via aromatic L-amino acid decarboxylase (DDC) and reuptake through the transporter SLC6A4, independent of serotonin receptor activity. Mechanistically, high level of intracellular 5-HT promotes neuroendocrine differentiation and suppresses androgen receptor (AR) signaling through histone serotonylation at H3K4me3Q5. This epigenetic modification reconfigures the H3K4me3 chromatin landscape and sustains NEPC-specific transcriptional programs. Pharmacological inhibition of 5-HT synthesis using the FDA-approved DDC inhibitor carbidopa significantly impairs tumor growth and prolongs survival in both genetically engineered and patient-derived xenograft models, highlighting histone serotonylation as a druggable vulnerability in NEPC. Overall design: RNA-seq profiling was performed on PC3 cells overexpressing DDC, SLC6A4, or an empty vector. ChIP-seq was performed for H3K4me3, H3K4me3Q5ser, and input controls in PC3 cells overexpressing DDC, SLC6A4, or an empty vector. CUT&Tag was performed in human prostate cancer cells using the Hyperactive Universal CUT&Tag Assay Kit for Illumina (Vazyme, TD903), followed by paired-end sequencing on Novaseq X. Raw sequencing reads were processed using FastQC for quality control and aligned to the human reference genome (GRCh38.release108) using Bowtie2(50). PCR duplicates have been removed. Peak calling was performed using MACS2(51), and annotation of binding sites was conducted using HOMER and in-house scripts.