Integrative bioinformatics and experimental validation of the prognostic and functional relevance of XDH and ITPA in non-small cell lung cancer.

Purine metabolism has been implicated in tumor biology and immune regulation, but the clinical and biological relevance of purine metabolism-related genes in non-small cell lung cancer (NSCLC) remains incompletely defined. Transcriptomic data from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) project, together with TCGA clinical data, were analyzed to identify differentially expressed purine metabolism-related genes and assess their prognostic associations. Immune infiltration was evaluated using single-sample gene set enrichment analysis (ssGSEA), and single-cell transcriptomic datasets were analyzed to characterize the cellular context of candidate genes. Stemness features and drug sensitivity were assessed using transcriptome-based computational models. XDH and ITPA protein expression was examined by Western blotting and immunohistochemistry (IHC) in an independent NSCLC cohort and in cell models. Stable knockdown of XDH or ITPA was performed in H1299 cells, with key functional findings further evaluated in A549 cells. Cisplatin sensitivity was assessed using cell-viability dose-response assays in H1299 and A549 cells. Several purine metabolism-related genes were upregulated in NSCLC and associated with overall survival (OS). XDH and ITPA showed higher protein expression in tumor tissues and were associated with adverse clinicopathological features and poorer survival. Higher expression of these genes was also associated with altered immune infiltration patterns. The messenger RNA-based stemness index (mRNAsi) was associated with ITPA and XDH expression in different directions, whereas higher XDH expression was associated with higher predicted half-maximal inhibitory concentration (IC50) values for cisplatin. Knockdown of XDH or ITPA attenuated proliferative, clonogenic, migratory, and invasive phenotypes in H1299 cells, with key findings reproduced in A549 cells. XDH knockdown also reduced the experimentally determined cisplatin IC50 in both H1299 and A549 cells. XDH and ITPA may represent candidate prognostic and functionally relevant purine metabolism-related genes in NSCLC. The integrated clinical, computational, and cellular findings support their association with NSCLC progression-related phenotypes, while the underlying molecular mechanisms and broader clinical applicability require further investigation.