Introducing a clinical-practical, alternative splicing activity-based proteogenomic method that identifies, in their oncogenically active states, biomarker genes bearing patient-specific GE or copy-number alterations of prognostic significance. This integrated multi-omics method uses intronic splicing enhancers (ISEs) probes to sort in situ ISE-interacting trans-acting protein factors (trans-interactome) directly from a heterogeneous tumor for subsequent mass spectrometry (MS) characterization.