map that is made publicly available atwww.proteinatlas.org.^38 Despite the use in
RPPA, these antibodies are interesting candidates for the application in imaging
mass spectrometry (see the next paragraph).
Imaging mass spectrometry (IMS) is the next method for personalized patient
profiling. This technique has experienced a real boom in last years, and its potential
is a real challenge for the researchers in biomedicine, especially in personalized
medicine.^39 IMS enables direct determination of the spatial distribution of cell and
tissue components, and exactly this fact makes this technique extremely interesting
for the application in personalized medicine. With an appropriate sample prepara-
tion, images of distribution of small molecules such as drugs and metabolites and
also the label-free images of macromolecular structures and components such as
proteins, carbohydrates, and lipids can be obtained.^40 Most IMS data are based on
matrix-assisted laser desorption/ionization (MALDI) or secondary ion mass spectro-
metry (SIMS); see Josic and Kovac ( 2009 ). MALDI can record the spatial distri-
bution of high-mass molecules, e.g., proteins and polysaccharides and their
metabolites. Consequently, IMS is well suited for absorption of drugs, their distri-
bution, metabolism, and excretion follow-up studies. The multicomponent detec-
tion capabilities of this technique are of prime interest for biomarker discovery. It is
both an advantage and a big disadvantage of this technique since single proteins are
still difficult to identify and validate as specific markers.^41 An important step
forward was the development of methods for identification of biomarkers that are
specific for a particular disease. In a relatively complicated study, Kang et al.^42 use
two-dimensional gel electrophoresis and fluorescence microscopy to verify proteins
that are specific for interface zones (a region between tumors and normal tissues) of
ovarian tumors. Le Founder et al.^43 provided IMS fingerprints for distinguishing
hepatocellular carcinoma (HCC) from cirrhosis in liver biopsies. The most discrimi-
nating peak that was more intense in HCC was characterized as monomeric protein
ubiquitin. This result was validated by an immunohistochemical study in a large
series of HCC/cirrhosis samples that were analyzed by tissue microarray. All
identified proteins (plastin 2 and peroxiredoxin 1 for interface region and ubiquitin
in HCC) are relatively abundant, and consequently both results are not spectacular,
but they can be considered as groundbreaking for further investigations. Recently,
Sugara et al.^44 introduced IMS as an alternative for RPPA to provide new infor-
mation on efficiency of kinase inhibitors used in the treatment of malignant mela-
noma. Determination of drug uptake at the target sides of directed therapy that was
gained by use of this method provides important data about its mode of action.
(^38) Ponten et al. ( 2011 ), pp. 428–446; Lundberg and Uhlen ( 2010 ), pp. 3984–3996.
(^39) MacAleese et al. ( 2009 ), pp. 819–834; Taverna et al. ( 2014 ).
(^40) Josic and Kovac ( 2009 ), pp. 207–213.
(^41) Kang et al. ( 2010 ), pp. 1157–1164.
(^42) Maier et al. ( 2013 ), pp. 2901–2910.
(^43) Le Founder et al. ( 2011 ), pp. 3755–3765.
(^44) Kang et al. ( 2010 ), pp. 1157–1164.
188 D. Josic ́and U. Andjelkovic ́