Proteomics and metabolomics identify molecular mechanisms of aging potentially predisposing for chronic lymphocytic leukemia

Abstract

B cell chronic lymphocytic leukemia (B-CLL), the most common type of leukemia in adults, is still essentially incurable despite the development of novel therapeutic strategies. This reflects the incomplete understanding of the pathophysiology of this disease. A comprehensive proteome analysis of primary human B-CLL cells and B cells from younger as well as elderly healthy donors was performed. For comparison, the chronic B cell leukemia cell line JVM-13 was also included. A principal component analysis comprising 6,945 proteins separated these four groups, placing B cells of aged-matched controls between those of young donors and B-CLL patients, while identifying JVM-13 as poorly related cells. Mass spectrometric proteomics data have been made fully accessible via ProteomeXchange with identifier PXD006570-PXD006572, PXD006576, PXD006578, and PXD006589-PXD006591. Remarkably, B cells from aged controls displayed significant regulation of proteins related to stress management in mitochondria and ROS stress such as DLAT, FIS1, and NDUFAB1, and DNA repair, including RAD9A, MGMT, and XPA. ROS levels were indeed found significantly increased in B cells but not in T cells or monocytes from aged individuals. These alterations may be relevant for tumorigenesis and were observed similarly in B-CLL cells. In B-CLL cells, some remarkable unique features like the loss of tumor suppressor molecules PNN and JARID2, the stress-related serotonin transporter SLC6A4, and high expression of ZNF207, CCDC88A, PIGR and ID3, otherwise associated with stem cell phenotype, were determined. Alterations of metabolic enzymes were another outstanding feature in comparison to normal B cells, indicating increased beta-oxidation of fatty acids and increased consumption of glutamine. Targeted metabolomics assays corroborated these results. The present findings identify a potential proteome signature for immune senescence in addition to previously unrecognized features of B-CLL cells and suggest that aging may be accompanied by cellular reprogramming functionally relevant for predisposing B cells to transform to B-CLL cells.

Altered expression of metabolic pathways in CLL detected by unlabelled quantitative mass spectrometry analysis

“…MIF secretion is robustly induced by oxidative stress (Gupta et al , ), which is supported by our data showing that CLL cells have higher expression of several antioxidant species (e.g. TXNRD2, GSTP1, SOD1, TXN) and evidence from the literature showing that CLL cells have high levels of intracellular ROS species (Mayer et al , ). Low levels of PNP have also been previously reported in CLL (Huang et al , ).…”

“…The availability of mass spectrometry (MS) late last century led to studies investigating the CLL proteome. These analyses identified a limited number of differentially expressed proteins not only between M-and UM-CLL (Cochran et al, 2003;Barnidge et al, 2005;Scielzo et al, 2005;Rees-Unwin et al, 2010;Alsagaby et al, 2014;Eagle et al, 2015), but also between healthy B cells and B-CLL cells (Johnston et al, 2018;Mayer et al, et al 2018). This is most likely not an accurate representation of the true proteomic differences between these cell types, given their vastly divergent lifespans and functions in the body.…”

Quantitative proteomics of synaptosome S‐nitrosylation in Alzheimer’s disease

“…This study identified both proteins as NOS2‐dependent synapto‐SNO proteins that increased during aging in APP/PS1 mice. NDUFAB1 regulation was previously related to aging and has been shown to be responsible for oxidative phosphorylation and down‐regulated in AD patients (Kim et al ; Mayer et al ; Akila Parvathy Dharshini et al ). NDUFAB1 reduction may lead to energy metabolism impairment and result in neuronal cell death by apoptosis (Kim et al ).…”

Metabolic underpinnings of leukemia pathology and treatment

“…19 Further evidence supporting dysregulated glutaminolysis was found in accompanying proteomic experiments which revealed increased levels of glutaminase and glutamine synthetase in CLL cells. 19 In comparison to normal lymphocytes, CLL cells have a dysregulated cell growth cycle and are primed for hypoxic response by constitutive low level expression of HIF-1α 20 even in normoxic environments such as circulating blood. Transcriptlevel expression of HIF-1α is variable among CLL patients 21 and has been correlated to unfavorable prognoses in a study of 88 CLL patients.…”

“…A mass spectrometry‐based metabolomic study of B lymphocytes from CLL patients (n = 4) in comparison to healthy controls (n = 5) revealed alterations in glutaminolysis in B‐CLL cells, specifically decreased levels of glutamine and glutamate and increased alanine, a product of glutaminolysis (Figure A) . Further evidence supporting dysregulated glutaminolysis was found in accompanying proteomic experiments which revealed increased levels of glutaminase and glutamine synthetase in CLL cells . In comparison to normal lymphocytes, CLL cells have a dysregulated cell growth cycle and are primed for hypoxic response by constitutive low level expression of HIF‐1α even in normoxic environments such as circulating blood.…”