Despite immense inte
rest in the p
roteome as a sou
rce of bioma
rke
rs in cance
r, mass spect
romet
ry has yet to yield a clinically useful p
rotein bioma
rke
r fo
r tumo
r classification. To explo
re the potential of a pa
rticula
r class of mass spect
romet
ry-based quantitation app
roaches, label-f
ree alignment of liquid ch
romatog
raphy coupled to tandem mass spect
romet
ry (LC鈥揗S/MS) data sets, fo
r the identification of bioma
rke
rs fo
r acute leukemias, we asked whethe
r a label-f
ree alignment algo
rithm could distinguish known classes of leukemias on the basis of thei
r p
roteomes. This app
roach to quantitation involves (1) computational alignment of MS1 peptide peaks ac
ross la
rge numbe
rs of samples; (2) measu
rement of the
relative abundance of peptides ac
ross samples by integ
rating the a
rea unde
r the cu
rve of the MS1 peaks; and (3) assignment of peptide IDs to those quantified peptide peaks on the basis of the co
rresponding MS2 spect
ra. We ext
racted p
roteins f
rom blasts de
rived f
rom fou
r patients with acute myeloid leukemia (AML, acute leukemia of myeloid lineage) and five patients with acute lymphoid leukemia (ALL, acute leukemia of lymphoid lineage). Mobilized CD34+ cells pu
rified f
rom pe
riphe
ral blood of six healthy dono
rs and mononuclea
r cells (MNC) f
rom the pe
riphe
ral blood of two healthy dono
rs we
re used as healthy cont
rols. P
roteins we
re analyzed by LC鈥揗S/MS and quantified with a label-f
ree alignment-based algo
rithm developed in ou
r labo
rato
ry. Unsupe
rvised hie
ra
rchical cluste
ring of blinded samples sepa
rated the samples acco
rding to thei
r known biological cha
racte
ristics, with each sample g
roup fo
rming a disc
rete cluste
r. The fou
r p
roteins best able to distinguish CD34+, AML, and ALL we
re all eithe
r known bioma
rke
rs o
r p
roteins whose biological functions a
re consistent with thei
r ability to distinguish these classes. We conclude that alignment-based label-f
ree quantitation of LC鈥揗S/MS data sets can, at least in some cases,
robustly distinguish known classes of leukemias, thus opening the possibility that la
rge scale studies using such algo
rithms can lead to the identification of clinically useful bioma
rke
rs.
r>Keywords:
rs" href="http://pubs.acs.org/action/doSearch?action=search&searchText=leukemia&qsSearchArea=searchText">leukemia; rs" href="http://pubs.acs.org/action/doSearch?action=search&searchText=mass%5C-spectrometry&qsSearchArea=searchText">mass-spectrometry; rs" href="http://pubs.acs.org/action/doSearch?action=search&searchText=biomarkers&qsSearchArea=searchText">biomarkers; rs" href="http://pubs.acs.org/action/doSearch?action=search&searchText=alignment%5C-based+quantification&qsSearchArea=searchText">alignment-based quantification