Mutant TP53 Hotspot Variants Differentially Rewire the Caspase Regulatory Network Across Cancer Lineages: A Pan-Cancer Computational Pharmacology Analysis

Background TP53 is mutated in approximately 50% of all human cancers, and mutant p53 (mutp53) proteins acquire gain-of-function (GOF) activities that actively suppress apoptosis. However, the mechanism by which mutp53 specifically rewires the complete caspase regulatory network spanning initiator caspases, executioner caspases, the PIDDosome complex, the pseudo-caspase FLIP (CFLAR), inhibitor of apoptosis proteins (IAPs), death receptors, and BH3-only proteins across distinct cancer lineages has never been systematically mapped at pan-cancer scale. Furthermore, whether individual hotspot variants (R175H, R248W, R273H) produce distinct caspase regulatory signatures remains unknown. Methods RNA-sequencing data (STAR counts) and somatic mutation data from 3,739 tumors across eight TCGA cohorts (LUAD, COAD, STAD, PAAD, LUSC, HNSC, BLCA, LIHC) were integrated to perform DESeq2 differential expression analysis comparing mutp53 (missense; n=1,202) versus wild-type p53 tumors, stratified by adenocarcinoma versus squamous/other lineage. Hotspot-resolved analyses were performed for R175H (n=59), R248W (n=33), and R273H (n=35). Spearman correlation, Kaplan-Meier survival analysis, Cox proportional hazards regression, ssGSEA apoptosis pathway scoring, and CCLE cell line validation (675 mutp53 vs 1,009 wtp53 lines across 24 lineages) were performed. A drug-target pharmacology network overlay mapped computationally identified vulnerabilities to clinical-stage apoptosis-restoring agents. Results Mutp53 consistently upregulated BIRC5 (survivin) and E2F1 across all eight cohorts, while FAS (TNFRSF6), BCL2, and HRK showed lineage-specific downregulation predominantly in adenocarcinomas. Hotspot analysis revealed that R175H and R248W produced bidirectional rewiring in adenocarcinomas, while R273H caused predominantly caspase network silencing in squamous/other lineages. ssGSEA demonstrated opposite apoptosis pathway enrichment directions between lineages: HALLMARK_APOPTOSIS was paradoxically enriched in adenocarcinoma mutp53 tumors but depleted in squamous/other mutp53 tumors. Clinically significant survival associations were identified for APAF1 in TCGA-BLCA (p=0.00018), XIAP in TCGA-BLCA (p=0.0036), BAX in TCGA-PAAD (p=0.0041), BCL2 in TCGA-PAAD (p=0.010), PIDD1 in TCGA-LUSC (p=0.0026), and CFLAR in TCGA-HNSC (p=0.028). CCLE validation confirmed the TCGA findings across independent cell lines. Conclusion Mutp53 rewires the caspase regulatory network in a lineage-specific and hotspot-resolved manner. This pan-cancer computational pharmacology analysis provides a vulnerability atlas directly informing rational drug combinations: venetoclax for BCL2-dependent adenocarcinomas, smac mimetics for XIAP/BIRC2-dependent bladder cancer, and TRAIL agonists combined with APR-246 for FAS-silenced squamous cancers, representing the first systematic integration of mutp53 caspase network biology with precision pharmacotherapy.