Investigating the impact of vitamin B6 deficiency on tumor development and metabolic homeostasis in Drosophila melanogaster

Vitamin B6, in its active form pyridoxal 5’-phosphate (PLP), is an essential cofactor required for over one hundred enzymatic reactions involved in amino acid, carbohydrate, and lipid metabolism, as well as in one-carbon and antioxidant pathways. Despite its fundamental role in cellular homeostasis, the biological consequences of vitamin B6 deficiency remain incompletely understood, particularly in the context of genome instability and cancer susceptibility. The aim of this work was to investigate how PLP deficiency influences both metabolic and genomic integrity in Drosophila melanogaster, and to explore whether these perturbations interact to promote tumorigenic processes. In the first part of the study, the Drosophila Rasv12 tumor model was used to test the hypothesis that vitamin B6 deficiency promotes tumor malignancy. Pharmacological inhibition of PLP synthesis using 4-deoxypyridoxine (4DP) or gingkotoxin (GT) cooperated with oncogenic Ras to convert benign overgrowths into invasive malignant tumors. PLP deficiency increased tumor size and promoted metastatic behavior, as indicated by basement membrane rupture and upregulation of Mmp1. Molecular analyses revealed elevated reactive oxygen species (ROS), reduced activity of the PLP-dependent enzyme serine hydroxymethyltransferase (SHMT), and the formation of chromosome aberrations (CABs), indicating that oxidative stress and impaired dTMP biosynthesis contribute to genomic instability. Supplementation with antioxidants or dTMP partially rescued both chromosomal and tumor phenotypes, suggesting a mechanistic link between redox imbalance, nucleotide metabolism and cancer progression. In the second part, NMR-based metabolomic profiling was applied to characterize the systemic metabolic alterations induced by vitamin B6 deficiency in wild-type larvae. The analysis revealed substantial increases in branched-chain and aromatic amino acids, glycine and glucose-1-phosphate, accompanied by a global reduction in lipids, including phospholipids and triglycerides. These shifts are consistent with decreased activity of PLP-dependent aminotransferases, decarboxylases and enzymes of lipid synthesis, indicating broad metabolic reprogramming under conditions of PLP shortage. The observed alterations parallel metabolic signatures described in diabetes, insulin resistance and cancer, reinforcing the physiological relevance of this model. Taken together, the results of this thesis suggest that vitamin B6 deficiency may generate a cellular environment in which metabolic imbalance and genomic instability intersect to promote oncogenic transformation. Although further studies are required to establish causality and tissue-specific mechanisms, this work highlights Drosophila melanogaster as a powerful model for dissecting how micronutrient deficiency can couple metabolism, redox regulation and genome integrity to influence disease susceptibility and cancer development.