Tangeretin Suppresses LUAD via SSTR4 Downregulation: Integrated Bioinformatics and Functional Validation

Lung adenocarcinoma (LUAD) remains the leading cause of cancer-related mortality worldwide, highlighting the urgent need for novel therapeutic targets. While the role of the somatostatin receptor (SSTR) family is well established in neuroendocrine tumors, their expression patterns, clinical significance, and therapeutic potential in LUAD are not fully understood. In this study, comprehensive analyses of publicly available databases, including TCGA, GSCA, and TIMER, revealed that SSTR4 transcriptional expression is significantly downregulated in LUAD tissues compared to adjacent normal lung tissues. Moreover, low SSTR4 expression correlates with advanced tumor stage, remodeling of the immune microenvironment, and decreased overall survival in patients with LUAD. Using the PRESTO-Tango system, we identified tangeretin (TAN) as a potential ligand for SSTR4. Functional assays demonstrated that SSTR4 knockdown markedly enhanced TAN-mediated proliferative, migratory, and survival inhibitory effects in LUAD cells. Subsequent RNA sequencing and pathway enrichment analyses revealed that the loss of SSTR4 altered the effects of TAN from extracellular matrix remodeling to disruption of calcium homeostasis and energy metabolism disorders, elucidating the mechanism underlying the enhanced antitumor activity. Collectively, these findings establish SSTR4 as a critical tumor suppressor and prognostic biomarker in LUAD and highlight the therapeutic potential of targeting the TAN-SSTR4 signaling axis. These results provide novel insights into the biological functions of SSTR family members in LUAD.