TMEM176A drives anti-apoptotic signaling through TGM2-mediated ERK activation in gastric cancer

Background: Gastric Cancer (GC) remains one of the leading causes of cancer-related mortality worldwide, yet the molecular mechanisms underlying its progression are not fully understood. TMEM176A, a transmembrane protein implicated in immune regulation and tumor biology, has an undefined role in GC. This study aims to elucidate the functional significance and mechanistic involvement of TMEM176A in GC.

Methods: TMEM176A expression and its prognostic significance in GC were first evaluated using TCGA-STAD data through Kaplan-Meier survival analysis, ROC curve analysis, and a nomogram-based prognostic model. Validation was performed by immunohistochemistry on tissue microarrays and Western blotting(WB) of clinical GC specimens. Functional roles of TMEM176A were investigated using knockout and overexpression GC cell models, followed by CCK-8 proliferation assays, wound-healing migration assays, cell-cycle distribution analysis, Apoptosis detection with Annexin V/PI flow cytometry, mitochondrial membrane potential (ΔΨm) measurement, and Western blotting of Bcl-2 Family proteins. RNA Sequencing (RNA-seq) with subsequent enrichment analyses was applied to identify downstream signaling pathways associated with TMEM176A. Potential protein interactions were further examined by co-immunoprecipitation and immunofluorescence. Finally, rescue experiments with a specific pathway inhibitor were conducted to confirm the mechanistic involvement of TMEM176A in gastric Cancer progression.

Results: TMEM176A expression was markedly elevated in tumor tissues and significantly associated with poor prognosis in GC. A prognostic nomogram combining TMEM176A expression with conventional clinicopathological factors demonstrated strong predictive performance (AUC = 0.768, 95 % CI: 0.694-0.843), with calibration plots confirming good agreement between predicted and observed survival. Functionally, TMEM176A promoted GC cell proliferation and migration, whereas its knockout induced G2/M cell cycle arrest, and caspase-dependent Apoptosis characterized by a decreased Bcl-2/Bax ratio and mitochondrial dysfunction. In vivo, TMEM176A overexpression accelerated tumor growth and suppressed Apoptosis. Transcriptomic profiling and pathway analyses identified MAPK/ERK signaling as a key downstream target. TMEM176A loss reduced ERK1/2 phosphorylation, and pharmacological rescue experiments through WB confirms these. Mechanistically, Transglutaminase 2 (TGM2) was identified as a novel downstream mediator of TMEM176A, and required for sustaining ERK activation. Rescue experiments showed that TGM2 overexpression rescued ERK phosphorylation and partially suppressed Apoptosis in TMEM176A-deficient cells, whereas pharmacologic inhibition of TGM2 abrogated the anti-apoptotic effects of TMEM176A overexpression.

Conclusion: We demonstrated that TMEM176A functions as a pivotal oncogenic driver in GC by promoting Apoptosis resistance and sustaining MAPK/ERK pathway activation. Mechanistically, TMEM176A transcriptionally upregulates TGM2, which in turn enhances ERK phosphorylation, thereby establishing a TMEM176A-TGM2-ERK signaling axis. This cascade represents a novel mechanism underlying GC progression and provides a promising target for therapeutic intervention.

Apoptosis; Gastric cancer; MAPK/ERK signaling; TGM2; TMEM176A.