Integrating single-cell and bulk RNA sequencing data reveals RGS4 as a functional driver in a proliferative subgroup of SF-1 lineage PitNETs.

The molecular determinants underlying the heterogeneity and proliferative behavior of Steroidogenic Factor-1 (SF-1) lineage Pituitary Neuroendocrine Tumors (PitNETs) remain insufficiently defined. We performed an integrated analysis of single-cell RNA sequencing (scRNA-seq) and bulk transcriptomic datasets from SF-1 lineage PitNETs to identify molecular subgroups and their defining biomarkers. The functional significance of the top candidate gene, Regulator of G-protein Signaling 4 (RGS4), was examined using gain- and loss-of-function approaches and pharmacological inhibition in pituitary adenoma cell lines. Mechanistic studies were conducted using protein interaction and stability assays. We identified a previously unrecognized SF-1 lineage subgroup characterized by markedly elevated RGS4 expression, which correlated with larger tumor size and higher MIB-1 proliferation index. Functional experiments demonstrated that Rgs4 enhances tumor cell proliferation and inhibits apoptosis. Mechanistically, RGS4 promotes p53 ubiquitination, resulting in its destabilization and proteasomal degradation. This study defines a new SF-1 lineage PitNETs subgroup characterized by high-RGS4 expression. RGS4 promotes tumor proliferation by destabilizing p53, highlighting the RGS4-p53 axis as a promising therapeutic target.