# Tumor-Derived Lactate Drives Malignant Progression of Refractory Papillary Thyroid Carcinoma via the H3K18la-STAT1-LDHA Axis

## TL;DR

Tumor lactate promotes aggressive thyroid cancer by modifying histones and activating genes that sustain cancer growth.

## Contribution

This study identifies a new regulatory axis linking tumor metabolism and epigenetics in papillary thyroid carcinoma.

## Key findings

- Elevated H3K18la levels correlate with aggressive features in papillary thyroid carcinoma.
- H3K18la activates STAT1, which upregulates LDHA to increase lactate production.
- The H3K18la-STAT1-LDHA axis sustains malignant progression in thyroid cancer.

## Abstract

Papillary thyroid carcinoma (PTC) remains among the most prevalent endocrine malignancies globally, with its incidence steadily rising. Although clinical outcomes are generally favorable, a clinically significant subset of patients exhibits highly aggressive tumor phenotypes, characterized by larger tumor size and increased lymph node metastasis. Accumulating evidence implicates metabolic reprogramming and epigenetic dysregulation as pivotal drivers of tumor progression. Lactate, one of the byproducts of tumor metabolism, has recently garnered attention for its regulatory functions beyond metabolism. Histone lactylation, a recently identified epigenetic modification dynamically regulated by intracellular lactate accumulation, has emerged as an important regulator of tumor proliferation, metastasis, immune evasion, and therapeutic resistance. However, the functional implications and mechanistic underpinnings of histone lactylation in PTC remain largely unexplored.

Here, we report significantly elevated pan-lysine lactylation and histone H3 lysine 18 lactylation (H3K18la) levels in clinical PTC specimens, with tumor tissues exhibiting markedly higher levels compared to adjacent normal thyroid tissues., correlating positively with aggressive clinicopathological features. Relevant cellular phenotypic assays further support this conclusion. Mechanistically, we demonstrate that H3K18la modification directly facilitates the transcriptional activation of Signal Transducer and Activator of Transcription 1 (STAT1). Activated STAT1 subsequently promotes transcriptional upregulation of Lactate Dehydrogenase A (LDHA), thereby enhancing lactate biosynthesis and establishing a self-perpetuating positive feedback loop. Consequently, tumor-derived lactate orchestrates and sustains malignant progression in PTC through this “H3K18la-STAT1-LDHA” regulatory axis.

Collectively, our findings uncover a novel mechanistic linkage between tumor metabolism and epigenetic regulation in PTC, providing critical insights into thyroid cancer pathogenesis. Furthermore, therapeutic targeting of the H3K18la-STAT1-LDHA axis may represent an innovative and promising strategy to improve outcomes for patients with aggressive and refractory PTC.