Oxidative damage-induced hyperactive ribosome biogenesis participates in tumorigenesis of offspring by cross-interacting with the Wnt and TGF-β1 pathways in IVF embryos.

In vitro fertilization (IVF) increases the risk of tumorigenesis in offspring. The increased oxidative damage during IVF may be involved in tumor formation. However, the molecular mechanisms underlying this phenomenon remain largely unclear. Using a well-established model of oxidatively damaged IVF mouse embryos, we applied the iTRAQ method to identify proteins differentially expressed between control and oxidatively damaged zygotes and explored the possible tumorigenic mechanisms, especially with regard to the effects of oxidative damage on ribosome biogenesis closely related to tumorigenesis. The iTRAQ results revealed that ribosomal proteins were upregulated by oxidative stress through the Nucleolin/β-Catenin/n-Myc pathway, which stimulated ribosomes to synthesize an abundance of repair proteins to correct the damaged DNA/chromosomes in IVF-derived embryos. However, the increased percentages of γH2AX-positive cells and apoptotic cells in the blastocyst suggested that DNA repair was insufficient, resulting in aberrant ribosome biogenesis. Overexpression of ribosomal proteins, particularly Rpl15, which gradually increased from the 1-cell to 8-cell stages, indicated persistent hyperactivation of ribosome biogenesis, which promoted tumorigenesis in offspring derived from oxidatively damaged IVF embryos by selectively enhancing the translation of β-Catenin and TGF-β1. The antioxidant epigallocatechin-3-gallate (EGCG) was added to the in vitro culture medium to protect embryos from oxidative damage, and the expression of ribosome-/tumor-related proteins returned to normal after EGCG treatment. This study suggests that regulation of ribosome biogenesis by EGCG may be a means of preventing tumor formation in human IVF-derived offspring, providing a scientific basis for optimizing in vitro culture conditions and improving human-assisted reproductive technology. Increased production of ribosomes, the multi-molecular structures inside cells where protein synthesis occurs, is implicated in the enhanced risk of cancer in offspring conceived by in vitro fertilization (IVF), suggesting an approach to reduce this risk. In studies on IVF mouse embryos, Zhiling Li and colleagues at First Affiliated Hospital of Shantou University Medical College in China found that harmful effects of natural oxidizing agents induced overproduction of specific protein components of ribosomes. This increased the embryos’ susceptibility to tumorigenesis through a particular molecular signaling pathway. Exposure to the natural antioxidant chemical epigallocatechin-3-gallate (EGCG) corrected the overproduction and protected the embryos. EGCG, found in green tea, is being widely investigated for its anticancer effects. Exposing embryos to EGCG during IVF might protect the resulting children from increased risk of tumor formation in later life.