Toxoplasma GRA16 Inhibits NF-κB Activation through PP2A-B55 Upregulation in Non-Small-Cell Lung Carcinoma Cells

Abstract

Nuclear factor kappa B (NF-κB) activation is a well-known mechanism by which chemoresistance to anticancer agents is reported. It is well-known that irinotecan as a chemotherapeutic drug against non-small-cell lung carcinoma (NSCLC) has limited anticancer effect due to NF-κB activation. In this study, we propose the novel role of GRA16, a dense granule protein of Toxoplasma gondii, as an anticancer agent to increase the effectiveness of chemotherapy via the inhibition of NF-κB activation. To demonstrate this, H1299 cells were stably transfected with GRA16. The anticancer effects of GRA16 were demonstrated as a reduction in tumor size in a mouse xenograft model. GRA16 directly elevated B55 regulatory subunit of protein phosphatase 2A (PP2A-B55) expression in tumor cells, thereby decreasing GWL protein levels and ENSA phosphorylation. This cascade, in turn, induced PP2A-B55 activation and suppressed AKT/ERK phosphorylation and cyclin B1 levels, suggesting reduced cell survival and arrested cell cycle. Moreover, PP2A-B55 activation and AKT phosphorylation inhibition led to NF-κB inactivation via the reduction in inhibitory kappa B kinase beta (IKKβ) levels, de-phosphorylation of inhibitor of kappa B alpha (IκBα), and reduction in the nuclear transit of NF-κB p65. Furthermore, this molecular mechanism was examined under irinotecan treatment. The PP2A-B55/AKT/NF-κB p65 pathway-mediated anticancer effects were only induced in the presence of GRA16, but not in the presence of irinotecan. Moreover, GRA16 synergistically promoted the anticancer effects of irinotecan via the induction of the sub-G1 phase and reduction of cell proliferation. Collectively, irinotecan and GRA16 co-treatment promotes the anticancer effects of irinotecan via NF-κB inhibition and cell cycle arrest induced by GRA16, subsequently increasing the chemotherapeutic effect of irinotecan to NSCLC cells via NF-κB inhibition.

Toxoplasma gondii infection possibly reverses host immunosuppression to restrain tumor growth

“…GRA16 interacts with host ubiquitin-specific protease 7 and protein phosphatase 2A to manipulate cell-cycle progression and restore p53 pathway through five putative nuclear sequences ( Bougdour et al., 2013 ). GRA16 also improves the treatment efficacy of irinotecan, a chemotherapeutic drug, by inhibiting the activation of nuclear factor kappa B (NF-κB) in non-small-cell lung carcinoma H1299 cells ( Seo et al., 2020 ). Furthermore, as the main regulator of immune and inflammatory processes, NF-κB is also regarded as a tumor-immunosurveillance factor that mediates the crosstalk of many transcription factors [such as the tumor necrosis factor receptor-associated factors (TRAFs)] and regulates the secretion of cytokines (such as TNFα, IL-1, and IL-6), cell proliferation, and apoptosis ( Hoesel and Schmid, 2013 ).…”

Irinotecan (CPT-11) Canonical Anti-Cancer Drug Can also Modulate Antiviral and Pro-Inflammatory Responses of Primary Human Synovial Fibroblasts

“…Regarding inflammation, data about CPT and its derivatives are still unclear. Indeed, it has been demonstrated that CPT and CPT-11 induce activation of the NF-κB pathway in a variety of human carcinoma cell lines, a mechanism thought to contribute to resistance to chemotherapy [41][42][43]. In addition, SN38, the active metabolite of CPT-11, has been shown to increase CXCL8 secretion by enhancing the phosphorylation of MAP kinases in HCT8 cells [44].…”

Anti-Tumor Effect of Parasitic Protozoans

“…Coincidentally, the secreted GRA15 was confirmed to localize to the endoplasmic reticulum and to activate innate immune and stimulator of interferon genes (STING) responses by promoting polyubiquitination at Lys-337 and oligomerization in a tumor necrosis factor (TNF) receptor-associated factor (TRAF) protein-dependent manner [ 24 ]. In addition, the GRA16 displayed the ability to break the chemoresistance of irinotecan by inhibiting nuclear factor kappa B (NF-κB) via a PP2A-B55/AKT/NF-κB p65 pathway against non-small-cell lung carcinoma (NSCLC) [ 25 ]. Recently, the fact that the small intestine (SI) exhibited low tumorigenesis or metastatic growth from distant tumors attracted attention.…”