Acute myeloid leukaemia (AML) is an aggressive blood cancer characterized by a distinct block in differentiation of myeloid progenitors, recurrent chromosomal translocations and gene mutations of which >50% involve signal transduction through dysregulated kinases and phosphatases. In search for novel protein biomarkers for disease stratification we investigated the phosphoproteome in leukaemic cells from 62 AML patients at time of diagnosis using immobilized metal-affinity chromatography, protein separation by two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry before validation by selected reaction monitoring (SRM). Unsupervised clustering found 27 phosphoproteins significantly discriminating patients according to leukaemic cell differentiation (French-American-British (FAB) classification), cytogenetic and mutational (FLT3, NPM1) status or response to chemotherapy. Monocytic differentiation (FAB M4-M5) correlated with enrichment of proteins involved in apoptosis (MOES, ANXA5 and EFHD2). TALDO, a protein associated with thrombocytopenia if down-regulated, was elevated in patients with wild type NPM1 compared to patients with NPM1 mutation. This study demonstrates the potential of quantitative proteomics in AML classification and risk stratification.
Biological significance: Patients diagnosed with AML are currently categorized according to cellular morphology, cytogenetic alterations and mutations, although the majority of these cellular and genetic alterations have no or unsolved impact on therapy selection or prognosis. We therefore explored the phosphoproteome for abundance changes associated with traditional classifiers to unravel patterns that could stratify patients at the protein level. MOES, ANXA5 and EFHD2 were confirmed by SRM to be correlated to monocytic differentiation, whilst TALDO was elevated in NPM1 wild type patients.
Keywords: 2D-DIGE; Acute myeloid leukaemia; Biomarker; Phosphoproteomics; SRM.
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