Toxoplasma gondii GRA16-induced apoptosis in KRAS-mutant colorectal cancer cells is linked to coordinated p53 and PP2A-B55 signaling

Colorectal cancer (CRC) with KRAS mutations represents a clinically challenging subgroup with variable treatment responses. Among these tumors, codon 12 mutations are associated with poor prognosis and treatment resistance, while KRASG12D-mutant CRCs lack effective mutation-specific therapeutic options. Toxoplasma gondii dense granule protein 16 (GRA16) is a parasite-derived host-modulating effector that modulates phosphatase and tensin homolog (PTEN)/p53, protein phosphatase 2A-B55 (PP2A-B55)-associated signaling, and cancer-associated metabolic pathways. We evaluated the anticancer effects of GRA16 in KRASG12D-mutant LS174T cells using KRASG13D-mutant HCT116 cells as a comparative TP53-wild-type CRC model. Stable GRA16-expressing cells were generated by lentiviral transduction and assessed for proliferation, cell death-associated responses, DNA damage/apoptosis-related protein markers, key signaling proteins, and targeted transcriptional changes. GRA16 inhibited proliferation and increased cell death-associated populations in both cell lines, accompanied by elevated γ-H2A.X, cleaved PARP, and cleaved caspase-3 levels. In HCT116 cells, GRA16 increased PTEN, p53, and PP2A-B55 protein levels and reduced total AKT and Survivin proteins, together with BAX induction and suppression of cell-cycle/checkpoint-, epithelial mesenchymal transition/motility-, and glycolysis-associated transcripts. In LS174T cells, GRA16 increased PP2A-B55 and reduced Survivin protein levels, whereas PTEN protein was unchanged, p53 was reduced, and total AKT was increased. These changes were accompanied by limited p53/BAX-associated transcriptional engagement, glycolytic attenuation, shared cell-cycle/checkpoint-associated gene suppression, and stress-adaptive remodeling. These findings suggest that GRA16 induces cell line-dependent anticancer-associated responses in KRAS-mutant CRC cells, with a prominent PTEN/p53-associated response in HCT116 cells and preserved PP2A-B55 induction and Survivin suppression in LS174T cells.