Protein drug target activation homogeneity in the face of intra- tumor heterogeneity: implications for precision medicine

Introduction: Recent studies indicated tumors may be comprised of heterogeneous molecular subtypes and incongruent molecular portraits may emerge if di erent areas of the tumor are sampled. This study explored the impact of intra- tumoral heterogeneity in terms of activation/phosphorylation of FDA approved drug targets and downstream kinase substrates. Material and methods: Two independent sets of liver metastases from colorectal cancer were used to evaluate protein kinase-driven signaling networks within di erent areas using laser capture microdissection and reverse phase protein array. Results: Unsupervised hierarchical clustering analysis indicated that the signaling architecture and activation of the MAPK and AKT-mTOR pathways were consistently maintained within di erent regions of the same biopsy. Intra-patient variability of the MAPK and AKT-mTOR pathway were