Hypothesis\nTumors that exceed a quantifiable splicing entropy threshold—defined as the Shannon entropy of aberrant splice junction usage normalized to total junction reads—become hypersensitive to SF3B1‑mutant‑selective synthetic introns and simultaneously generate a neoantigen landscape with sufficient immunogenicity to respond to splice‑neo‑guided vaccines.\n\n## Mechanistic Basis\nRecent work shows that SF3B1 K700E, SRSF2 P95, and U2AF1 S34F/Y mutations rewire splice site recognition without destroying the spliceosome, creating chronic splicing stress, R‑loop accumulation, and dependence on ATR/Chk1 and PRMT5【https://pmc.ncbi.nlm.nih.gov/articles/PMC12982372/】. We propose that as splicing entropy rises, two convergent processes amplify vulnerability: (1) increased production of cryptic introns and exon‑skipping events fuels synthetic intron‑mediated lethal missplicing because the mutant spliceosome already operates near its fidelity limit; (2) the same aberrant transcripts generate frameshift‑derived neoantigens that bind HLA‑A02:01 with high affinity, as demonstrated for influenza‑like epitopes【https://pubmed.ncbi.nlm.nih.gov/38754917/】. Crucially, elevated R‑loops at promoters of antigen‑processing genes (e.g., TAP1, ERAP1) remodel chromatin, enhancing neoantigen presentation and creating a feed‑forward loop where splicing entropy both drives immune visibility and sensitizes cells to splice‑targeted toxins.\n\n## Testable Predictions\n1. In SF3B1‑mutant cell lines, measuring splicing entropy from RNA‑seq will stratify clones into low, intermediate, and high entropy groups; only the high‑entropy cohort will show >5‑fold loss of viability after treatment with a synthetic intron designed to exploit SF3B1 hypersensitivity【https://aacrjournals.org/cancerdiscovery/article/12/5/1180/694527/Synthetic-Introns-Support-Targeting-of-Tumor-Cells】.\n2. High‑entropy tumors will harbor a neoantigen burden whose z‑score exceeds the 90th percentile of the cohort and will display stronger HLA‑A02:01 binding (IC50 < 50 nM) than low‑entropy counterparts, correlating with increased CD8⁺ T‑cell infiltration in co‑culture assays.\n3. Combining synthetic intron therapy with a splice‑neo‑personalized vaccine will produce synergistic tumor regression in high‑entropy xenografts, whereas low‑entropy tumors will respond to neither modality alone.\n\n## Experimental Design\n- Generate isogenic SF3B1 K700E, SRSF2 P95H, and U2AF1 S34F lines in a hematopoietic background; use CRISPR‑base editing to titrate mutant allele frequency.\n- Perform deep RNA‑seq, compute splice junction Shannon entropy (H = - Σ p_i log p_i) where p_i is proportion of each observed junction; validate with long‑read Iso‑Seq to capture cryptic events.\n- Treat cells with a panel of synthetic introns (e.g., targeting BCL2L1 or MCL1) and measure viability (CellTiter‑Glo) and R‑loop levels (S9.6 immunofluorescence).\n- Predict neoantigens using SPLICE‑neo pipeline, synthesize peptides, assess HLA‑A*02:01 binding via competitive ELISA, and stimulate autologous PBMCs to measure IFN‑γ ELISpot.\n- In vivo, implant high‑ vs low‑entropy xenografts into NSG mice, randomize to synthetic intron, vaccine, combination, or control; monitor tumor growth and immune infiltrate (flow cytometry, immunohistochemistry).\n\n## Potential Implications\nIf validated, splicing entropy would become a quantitative biomarker for patient selection in splice‑targeted clinical trials and for designing neoantigen vaccines that exploit the very instability that drives oncogenesis. It also offers a mechanistic bridge between the noise‑to‑entropy transition in aging and the therapeutic window created by spliceosome addiction in cancer.