CSN3 promotes gastric cancer progression and is associated with immune infiltration and inflammatory signaling

Casein kappa (CSN3) is a milk protein-encoding gene, and its expression pattern and biological significance in gastric cancer (GC) remain unclear, this study aims to explore expression and function of CSN3 in GC.

CSN3 expression was assessed in GC tissues and cell lines. Its biological effects were examined in vitro and in vivo. STRING and AlphaFold 3 were used to explore CSN3-associated proteins. RNA sequencing was performed to investigate mechanisms associated with CSN3. Key molecules and inflammatory cytokines related to NOD/TLR signaling were validated by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Immune infiltration was analyzed using Tumor Immune Estimation Resource (TIMER) and preliminarily validated by immunohistochemistry.

CSN3 expression was elevated in GC and was positively associated with deeper tumor invasion, lymph node metastasis, advanced Tumor-Node-Metastasis (TNM) stage, and poorer prognosis. Knockdown of CSN3 inhibited GC cell proliferation and migration while promoting apoptosis. CSN3 overexpression promoted tumor growth in vivo. Protein-protein interaction analysis identified CALM3 as a potential CSN3-interacting protein. RNA sequencing revealed that CSN3 overexpression was associated with the NOD-like receptor and Toll-like receptor signaling pathways. Western blotting showed increased NOD1, RIP2, and p-p65 levels in CSN3-overexpressing cells. RT-qPCR demonstrated upregulation of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α). Moreover, CSN3 expression was positively correlated with immune infiltration, particularly CD8⁺ T cells.

CSN3 is upregulated in GC and is associated with malignant progression and poor prognosis. CSN3 may promote GC progression partly through modulation of NOD1/RIP2/NF-κB-related inflammatory signaling and remodeling of the tumor immune microenvironment. These findings suggest that CSN3 may serve as a potential biomarker in GC.