Toxoplasma gondii GRA16 Suppresses Aerobic Glycolysis by Downregulating c-Myc and TERT Expressions in Colorectal Cancer Cells.

Abstract

Despite its relatively low adenosine triphosphate (ATP) production efficiency, cancer cells reprogram their metabolism to utilize aerobic glycolysis for rapid proliferation. This "Warburg effect" not only provides biosynthetic precursors but also creates a tumor-favorable microenvironment. Key oncogenic regulators such as protein kinase B (AKT), nuclear factor kappa B (NF-κB), and cellular myelocytomatosis oncogene (c-Myc) enhance glycolytic activity by inducing the expression of enzymes including glucose transporters (GLUTs), hexokinase 2 (HK2), lactate dehydrogenase A (LDHA), and monocarboxylate transporters (MCTs). Moreover, telomerase reverse transcriptase (TERT), beyond its canonical role in telomere maintenance, also promotes glycolysis via the NF-κB and c-Myc pathways. From a therapeutic perspective, aerobic glycolysis contributes to glucose-mediated chemoresistance, limiting the efficacy of irinotecan in colorectal cancer (CRC). In this study, we investigated the role of Toxoplasma gondii-derived dense granule protein 16 (GRA16) in modulating glycolysis and irinotecan sensitivity. In HCT116 CRC cells stably expressing GRA16, AKT and NF-κB signaling were suppressed, leading to the downregulation of c-Myc and TERT. This resulted in decreased expression of GLUTs, HK2, LDHA, and MCTs, ultimately reducing glucose uptake and lactate production. Functional assays revealed that GRA16 induced G2/M cell cycle arrest, increased apoptosis, and suppressed proliferation. Notably, GRA16-expressing cells treated with irinotecan exhibited increased Sub-G1 accumulation and late-apoptotic and necrotic populations. Furthermore, siRNA-mediated silencing of c-Myc confirmed its key role in regulating TERT and glycolytic enzymes. These findings indicate that GRA16 suppresses aerobic glycolysis via the c-Myc/TERT axis and enhances irinotecan sensitivity, offering a promising strategy to overcome chemoresistance in CRC.