Fig. 2

STK3 promotes GC by activating the Ras-MAPK signaling pathway (*, P < 0.05; **, P < 0.01; ***, P < 0.001). a The heatmap of STK family members in nine GC cell lines. STK3 is abundantly expressed, especially in NCI-N87 and MKN28 cells. b, c The STK3 mRNA and protein expression were significantly decreased after siSTK3 transfection in NCI-N87 and MKN28 cells. d STK3 knockdown suppressed GC cell proliferation. e Depletion of STK3 inhibited monolayer colony formation of the cancer cells. f, g GC cell migration and invasion abilities were impaired with the siSTK3 transfection. h, i, j, k GSEA demonstrated that the STK3 depletion was negatively correlated with cell cycle checkpoint, DNA replication, MAPK pathway, and Ras pathway. l, m In STK3-depleted cells, the DEGs (|Fold Change| > 1.5, P < 0.05) were enriched in the Ras-MAPK signaling pathway, cell cycle, and DNA replication through KEGG and GO enrichment analysis. n STK3 knockdown blocked the Ras activation in MKN28 cells. o The ERK is dephosphorylated and inactivated in the siSTK3 transfectants. p Knocking down STK3 induced G1 phase cell cycle arrest and apoptosis, which were confirmed by the downregulation of CDK4, CDK6, and p-Rb, and activation of cleaved-caspase 7 and cleaved-PARP. q STK3 depletion significantly suppressed the GC-derived organoid growth. Scale bar = 100 μm