Rhein suppresses lactate metabolism and melanoma progression via downregulating LDHA/H3K18 lactylation/PLK1 axis

INTRODUCTION: An increasing body of evidence suggests that lactate and its associated post-translational modification, lactylation, are critically involved in the aggressive progression of melanoma and represent promising therapeutic targets. Rhein, a bioactive compound derived from rhubarb-a traditional Chinese medicinal herb-has shown anti-cancer properties in multiple tumor types. Nevertheless, its role in melanoma remains poorly understood. OBJECTIVES: This study investigated the role of Rhein in melanoma and uncovered the underlying mechanism. METHODS: Cell growth and cell death were investigated by colony formation and Propidium Iodide (PI) Staining. The RNA sequencing analysis was used to identify the altered genes and miRNAs. Targeted Metabolomics Analysis was used to investigate the altered metabolites. RESULTS: In this study, we demonstrate that Rhein effectively suppresses melanoma cell proliferation and migration while inducing apoptosis in vitro, and also inhibits tumor growth in vivo. Moreover, Rhein strengthens the host's anti-tumor immune response and counteracts tumor immune evasion. Mechanistically, Rhein significantly reduces LDHA expression, leading to decrease intracellular and extracellular lactic acid levels. Restoring LDHA expression or supplementing lactate diminishes Rhein's anti-melanoma activity and facilitates immune escape. We further show that Rhein downregulates PLK1 by reducing histone H3K18 lactylation at the PLK1 promoter. Notably, our results reveal that Rhein treatment markedly increases miR-27a-5p expression. Upregulated miR-27a-5p suppresses LDHA, subsequently lowering both lactic acid accumulation and PLK1 levels. CONCLUSIONS: Taken together, these data highlight the critical involvement of the miR-27a-5p/LDHA/lactate/PLK1 signaling axis in mediating Rhein's anti-melanoma effects, suggesting its potential as a therapeutic strategy for melanoma.