GSTK1 regulates glycolysis‑related proteins and lactylation‑associated molecular events via the IL‑6/JAK2/STAT3 axis in gastric cancer: insights from integrated transcriptomic and in vitro functional assays

Gastric cancer (GC) exhibits prominent intratumoral heterogeneity and metabolic reprogramming, which contributes to metastasis and therapeutic resistance. Both glycolytic reprogramming and lysine lactylation facilitate tumor progression, yet their synergistic regulatory networks in GC remain poorly defined. Glutathione S‑transferase kappa 1 ( GSTK1 ) participates in redox and energy homeostasis and modulates metabolic activity, inflammatory responses, and lactylation across multiple diseases. Nevertheless, systematic transcriptomic characterization and functional validation of GSTK1 in GC remain lacking. We integrated bulk, single‑cell, and spatial transcriptomic datasets from TCGA and GEO to characterize GC tumor microenvironment heterogeneity. InferCNV, CytoTRACE, CellChat, RCTD, and MISTy algorithms were applied to evaluate genomic instability, stemness, intercellular communication, and spatial signaling. Multi‑cohort survival analysis was performed to screen metabolism‑related prognostic hub genes. Spatial transcriptomics was utilized to examine the spatial distribution of candidate hub genes, along with energy metabolism and lactylation signatures. GC cell lines were used to validate the regulatory functions of hub genes in malignant behaviors, inflammatory signaling, glycolysis‑related protein expression, and global lactylation levels. Multi‑layer transcriptomic profiling identified a putative malignant Epi_2 epithelial subset characterised by high genomic instability, stemness and inferred NK‑cell communication. This subset displays activated energy‑metabolism and lactylation‑associated transcriptional signatures. Multi‑cohort survival analysis confirmed that elevated GSTK1 expression correlates with favorable GC prognosis. Spatial transcriptomics revealed spot-level positive correlations between GSTK1 and energy metabolism and lactylation signatures. In vitro assays linked GSTK1 alterations to GC malignant behaviors including proliferation, migration, invasion and EMT, as well as IL‑6/JAK2/STAT3 signaling, glycolytic protein abundance, and global lactylation levels. GSTK1 represents a candidate prognostic biomarker requiring further validation. The identified GSTK1 -associated regulatory axis links inflammatory signaling, glycolysis-related proteins and global lysine lactylation, providing mechanistic insights into GC progression and suggesting a potential therapeutic target.