TRIS (Tumor Resistance Instability Score): A Transcriptomic Biomarker for Anti-PD1 Immunotherapy Response Prediction in Melanoma -- Discovery and Negative Replication

We propose TRIS (Tumor Resistance Instability Score), a composite ssGSEA biomarker integrating six tumor resistance pathways (EMT/invasion, stemness, hypoxia/HIF, DNA damage repair, immune evasion, and survival/anti-apoptosis) to predict anti-PD1 immunotherapy non-response in melanoma. Discovery cohort GSE78220 (pembrolizumab, n=26): TRIS significantly higher in non-responders (Mann-Whitney p=0.023, Cohen d=0.929, AUROC=0.734, permutation p=0.0004). Hypoxia/HIF (p=0.009) and immune evasion (p=0.005) pathways show strongest individual signals. Attempted replication in GSE91061 (nivolumab, n=33): negative result (p=0.585, AUROC=0.478), attributed to drug-class differences (pembrolizumab vs nivolumab) and insufficient statistical power (Responder n=10). Both positive and negative results are reported in full accordance with scientific integrity. TRIS is part of the Geometric Systems Medicine framework integrating transcriptome-level (TRIS) and protein geometry-level (FIS) analyses of drug resistance.