Proteomics-based identification of cancer-associated proteins in chronic lymphocytic leukaemia

ABSTRACT

BACKGROUND: Chronic lymphocytic leukaemia (CLL) is a neoplasm of B-cells characterized by variable prognosis. Exploring the proteome of CLL cells may provide insights into the disease. Therefore, eleven proteomics experiments were conducted on eleven primary CLL samples. RESULTS: We reported a CLL proteome consisting of 919 proteins (false discovery rate (FDR) 1%) whose identification was based on the sequencing of two or more distinct peptides (FDR of peptide sequencing 1%). Mass spectrometry-based protein identification was validated for four different proteins using Western blotting and specific antibodies in different CLL samples. Small sizes of nucleolin (~57 kDa and ~68 kDa) showed a potential association with good prognosis CLL cells (n = 8, p < 0.01). Compared with normal B-cells, CLL cells over-expressed thyroid hormone receptor-associated protein 3 (THRAP3; n = 9; p = 0.00007), which is implicated in cell proliferation; and heterochromatin protein 1-binding protein 3 (HP1BP3; n = 10; p = 0.0002), which promotes cell survival and tumourogenesis. A smaller form of HP1BP3, which may correspond to HP1BP3 isoform-2, was specifically identified in normal B-cells (n = 10; p = 0.0001). HP1BP3 and THRAP3 predicted poor prognosis of CLL (p 0.05). Consistently, THRAP3 and HP1BP3 were found to be associated with cancer-related pathways (p 0.05). CONCLUSIONS: Our findings add to the known proteome of CLL and confirm the prognostic importance of two novel cancer-associated proteins in this disease.