LGALS3 Drives Dopamine Agonist Resistance in Prolactinoma by Activating the MAPK/ERK Pathway: A Multi‐Omics Study

BACKGROUND: Dopamine agonist resistance is observed in 10%-30% of patients with prolactinomas, resulting in therapeutic failure and tumour progression. The molecular mechanisms underlying this resistance are not yet fully understood, highlighting the need for the identification of novel biomarkers and therapeutic targets. METHODS: We performed a comprehensive integrative analysis of bulk RNA sequencing and single-cell RNA sequencing datasets obtained from dopamine agonist-resistant and dopamine agonist-sensitive prolactinomas. To substantiate the primary findings, we utilised a multifaceted methodological framework that integrated Weighted Gene Co-expression Network Analysis with machine learning techniques, including Random Forest, Support Vector Machine, and Least Absolute Shrinkage and Selection Operator. This was complemented by functional assays, which encompassed in vitro experiments involving gene overexpression and knockdown in GH3 cell models, alongside in vivo investigations using nude mouse xenograft models. RESULTS: LGALS3 has been identified as a pivotal factor in mediating resistance. Through single-cell RNA sequencing analysis, a resistance-specific subpopulation, termed Cluster 15, was discovered. This cluster is characterised by heightened genomic instability and stemness, as evidenced by increased expression of SOX2 and SOX9, with predominant expression of LGALS3. Mechanistically, LGALS3 activates the MAPK/ERK signalling pathway, which in turn enhances cell viability, prolactin secretion, and migration, while simultaneously inhibiting apoptosis by modulating the Bax/Bcl-2/Caspase cascade. Functional validation studies demonstrated that silencing LGALS3 significantly reduced tumour growth both in vitro, as shown by decreased Ki67 proliferation and impaired migration, and in vivo, as indicated by reduced tumour weight and volume. CONCLUSION: LGALS3 functions as a candidate diagnostic biomarker and represents a promising therapeutic target. Targeting the LGALS3-MAPK axis presents a viable strategy to restore therapeutic sensitivity in patients with refractory prolactinoma.