Alpha-defensins secreted by dysplastic granulocytes inhibit the differentiation of monocytes in chronic myelomonocytic leukemia.

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic disorder that occurs in elderly patients. One of the main diagnostic criteria is the accumulation of heterogeneous monocytes in the peripheral blood. We further explored this cellular heterogeneity and observed that part of the leukemic clone in the peripheral blood was made of immature dysplastic granulocytes with a CD14(-)/CD24(+) phenotype. The proteome profile of these cells is dramatically distinct from that of CD14(+)/CD24(-) monocytes from CMML patients or healthy donors. More specifically, CD14(-)/CD24(+) CMML cells synthesize and secrete large amounts of alpha-defensin 1-3 (HNP1-3). Recombinant HNPs inhibit macrophage colony-stimulating factor (M-CSF)-driven differentiation of human peripheral blood monocytes into macrophages. Using transwell, antibody-mediated depletion, suramin inhibition of purinergic receptors, and competitive experiments with uridine diphosphate (UDP)/uridine triphosphate (UTP), we demonstrate that HNP1-3 secreted by CD14(-)/CD24(+) cells inhibit M-CSF-induced differentiation of CD14(+)/CD24(-) cells at least in part through P2Y6, a receptor involved in macrophage differentiation. Altogether, these observations suggest that a population of immature dysplastic granulocytes contributes to the CMML phenotype through production of alpha-defensins HNP1-3 that suppress the differentiation capabilities of monocytes.

[Towards a standardization of the tools for the studies of clinical proteomics]. / Vers une standardisation des outils pour les études de protéomique clinique.

Proteins identified in biological fluids of cancer patients could be helpful for both diagnosis and prognosis. However, clinical proteomics based on analysis of protein profiles in biological fluids has demonstrated various flaws, most of them related to the difficulties met in reproducibility. These difficulties could be partly overcome by accurate standardisation of pre-analytical and analytical steps of these studies. The size of the patient cohort is one of the parameters that determine the powerfulness of the study. Recruitment of a cohort with a sufficient size often implies multicentric studies in which analysis of the reproducibility between centres and standardisation of pre-analytical and analytical steps are essential. Such a standardisation requires the use of calibrated samples as common references.

Human defensins as cancer biomarkers and antitumour molecules.

Human defensins, which are small cationic peptides produced by neutrophils and epithelial cells, form two genetically distinct alpha and beta subfamilies. They are involved in innate immunity through killing microbial pathogens or neutralizing bacterial toxins and in adaptive immunity by serving as chemoattractants and activators of immune cells. alpha-defensins are mainly packaged in neutrophil granules (HNP1, HNP2, HNP3) or secreted by intestinal Paneth cells (HD5, HD6), while beta-defensins are expressed in mucosa and epithelial cells. Using surface enhanced laser desorption/ionisation time-of-flight (SELDI-TOF) mass spectrometry (MS), alpha-defensins were found to be expressed in a variety of human tumours, either in tumour cells or at their surface. HNP1-3 peptides are also secreted and their accumulation in biological fluids was proposed as a tumour biomarker. Conversely, beta-defensin-1 (HBD-1) is down-regulated in some tumour types in which it could behave as a tumour suppressor protein. Alpha-defensins promote tumour cell growth or, at higher concentration, provoke cell death. These peptides also inhibit angiogenesis, which, in addition to immunomodulation, indicates a complex role in tumour development. This review summarizes current knowledge of defensins to discuss their role in tumour growth, tumour monitoring and cancer treatment.