The Proteome Landscape of Chronic Lymphocytic Leukemia

Many functional consequences of mutations on tumor phenotypes in chronic lymphocytic leukemia (CLL) are only partially known. This is in part due to missing information on the proteome of CLL. We profiled the proteome of 49 diverse CLL samples with data-independent acquisition mass spectrometry (DIA-MS) and related the results to genomic, functional and clinical differences. We found trisomy 12 and IGHV to be major determinants of proteome variation in CLL (1073 and 512 differential proteins). In contrast to reports in other biological systems, the disease driver trisomy 12 was associated with limited protein buffering, a finding that suggests the biological relevance of proteins encoded by chromosome 12 for CLL biology. Protein complex analyses detected functional units involved in BCR/PI3K/AKT signaling in CLL with trisomy 12. We identified the transcription factor complex of STAT1/STAT2 to be up-regulated in IGHV unmutated CLL. We tested the functional relevance of protein expression for associations with response to anticancer drugs, and STAT2 protein expression emerged as a biomarker for the prediction of response to kinase inhibitors including BTK and MEK inhibitors. This study highlights the emerging importance of protein abundance profiling in cancer research and identifies STAT2 protein levels as new key factor in CLL biology.