In gel digestion workflow

The molecular identities of the Buckets from the T point of the study. The knowledge of the protein id essential for a further antibody based validation.

the predictive biomarker to the clinical situ development of an antibody based ELISA assay.

Since nearly all of the Buckets from table 10 displ 4000 Da, a direct identification of the biomarker similar to a Bottom Up workflow, was technically no identification of those biomarkers, a pre

initial study containing the Bucket of interests,

Therefore, LC-fractions of interests from a cell line with a high biomarker were separated in a

molecular size of the biomarker candidate to be ide Subsequently, in gel digestion of proteins within g

peptides were eluted and subjected to cap

were spotted on PAC targets and peptides were ident

MS-MS spectra were analyzed by a database search on the MASC 9 gives a schematic overview on the in gel digestio

Figure 10: Schematic overview on the in gel digesti digestion was performed and subsequently LC

workflow for the identification of biomarker

tities of the Buckets from the T-test analysis were unknown at this point of the study. The knowledge of the protein identity of a biomarker candidate is essential for a further antibody based validation. Furthermore, the final translation of the predictive biomarker to the clinical situation is mostly accompanied by the development of an antibody based ELISA assay.

Since nearly all of the Buckets from table 10 displayed a molecular weight above identification of the biomarker candidates via MS/MS analysis, similar to a Bottom Up workflow, was technically not possible. As a first step for the identification of those biomarkers, a pre-fractionation of the HPLC-fractions from the initial study containing the Bucket of interests, was performed by SDS page.

fractions of interests from a cell line with a high expression of the biomarker were separated in a 4-12% SDS Bis Tris gel and gel bands at the molecular size of the biomarker candidate to be identified were excised Subsequently, in gel digestion of proteins within gel bands was performed, the tryptic peptides were eluted and subjected to cap-RP-HPLC. The resulting LC

were spotted on PAC targets and peptides were identified by MS/MS analysis.

ctra were analyzed by a database search on the MASCOT server.

9 gives a schematic overview on the in gel digestion workflow.

Figure 10: Schematic overview on the in gel digestion workflow. Gel bands were excised, in gel subsequently LC-MALDI-MS/MS analysis revealed the protein identity.

for the identification of biomarker candidates test analysis were unknown at this

entity of a biomarker candidate is Furthermore, the final translation of ation is mostly accompanied by the

ayed a molecular weight above candidates via MS/MS analysis, t possible. As a first step for the fractions from the was performed by SDS page.

fractions of interests from a cell line with a high expression of the 12% SDS Bis Tris gel and gel bands at the molecular size of the biomarker candidate to be identified were excised.

el bands was performed, the tryptic HPLC. The resulting LC-fractions ified by MS/MS analysis. The ctra were analyzed by a database search on the MASCOT server. Figure

Gel bands were excised, in gel MS/MS analysis revealed the protein identity.

3. Results

An example for a MS/MS spectrum, which resulted in the identification of the Superoxide dismutase [Cu/Zn] is shown in figure 11. The spectrum was generated from one (3720.81m/z, corresponding to the bucket 5 of the initial study) of the three peptides that were detected during the identification of the protein. The MASCOT database search for this peptide resulted in a MASCOT score of 151, and thus identified the SOD 1 with great confidence. In the In gel digestion experiments, several peptides corresponding to the SOD 1 were detected with high intensities, which indicates a high abundance of the protein in the LC-Fraction.

Figure 11: MALDI-MS/MS spectra of one (3720.81m/z) of the three peptides used for the identification of the Superoxide dismutase [Cu/Zn]. The relative intensity is plotted on the y-axis, the molecular mass is plotted on the x-axis. Peptides that could be linked to fragments are indicated by the lines below.

This was initially stated by the MALDI-MS spectrum of the corresponding cell line from the basic data set of the study. Other significantly (p 0.05) regulated biomarker candidates which were identified by using this approach are shown in table 11. The identification approach using in gel digestion resulted in the identification of twenty one biomarker candidates from various cellular compartments, with several biological functions. Among those were for example nuclear proteins, such as the DNA-directed

3. Results

RNA polymerase, the small nuclear ribonucleoprotein Sm D3 and the Histone H2B type 1. Furthermore, enzymes located in the cytoplasm like the Superoxide dismutase [Cu/Zn], the Ubiquitin-60S ribosomal protein L40 and the mitochondrial ATPase inhibitor, were identified.

Although all of these twenty one biomarker candidates may have a potential in predicting the response to FOLFOX treatment or give insight in mechanisms of chemoresistance, it was not possible to validate them all during this thesis. For this reason, a literature search on all identified biomarker candidates was conducted in order to select the most promising biomarker candidates. As a result of this literature search, three biomarker candidates were selected for further validation. This set of biomarkers included the Superoxide dismutase [Cu/Zn] (SOD1), the Ubiquitin-60S ribosomal protein L40 (UBA52) and the mitochondrial ATPase inhibitor (ATPIF1).

The SOD1 has already been described in the context of chemoresistance to cisplatin and has been found to be regulated similar to the findings in this study. This biomarker, which in general supports/confirms the results from this study, has been used as an internal control. The biomarker candidates UBA52 and ATPIF1 are undescribed in the context of chemoresistance and thus potentially represent valuable, newly discovered predictors of response to FOLFOX chemotherapy.

3. Results

Table 11: List of biomarker candidates from the Top Down study, identified by the in gel digestion approach. Expression differences of the biomarker candidates are displayed as Fold change in relation to the S = chemosensitive vs. R = chemoresistant group.

T-test Bucket Identity of Biomarker Candidates UniProt identifier p-value Fold change S/R

2470.4s:15858.49m/z Superoxide dismutase [Cu-Zn]- Homo sapiens (Human) SODC_HUMAN 0.0001 -1.86

1491.5s:12332.08m/z ATPase inhibitor, mitochondrial- Homo sapiens (Human) ATIF1_HUMAN 0.0027 4.94

1475.4s:6170.38m/z Ubiquitin-60S ribosomal protein L40- Homo sapiens (Human) RL40_HUMAN 0.0001 3.61

2337.5s:11204.95m/z Dermcidin (Preproteolysin)- Homo sapiens (Human) DCD_HUMAN 0.0063 3.31

3000.2s:13926.29m/z Thioredoxin domain-containing protein 17- Homo sapiens (Human) TXD17_HUMAN 0.0054 2.68

2406.9s : 6921.07m/z DNA-directed RNA polymerases I, II, and III subunit RPABC4 OS=Homo sapiens RPAB4_HUMAN 0.0015 -1.79

2660.9s : 13727.06m/z Histone H2B type 1 (H2B.1 A)- Homo sapiens (Human) H2B1C_HUMAN 0.0002 -3.39

1665.6s : 8373.76m/z Cysteine-rich protein 1 (Cysteine-rich intestinal protein) (CRIP) - Homo sapiens (Human) CRIP1_HUMAN 0.0011 1.81 2817.1s : 8867.83m/z Cytochrome c oxidase polypeptide VIc precursor (EC 1.9.3.1) - Homo sapiens (Human) COX6C_HUMAN 0.0017 -2.08

2673.0s : 8144.58m/z Uncharacterized protein C20orf52 - Homo sapiens (Human) ROMO1 CT052_HUMAN 0.0030 -2.14

2738.9s : 18435.83m/z Thioredoxin, mitochondrial precursor (Mt-Trx) (MTRX) (Thioredoxin-2) - Homo sapiens (Human) THIOM_HUMAN 0.0049 -2.1 2626.6s : 11040.89m/z Loss of heterozygosity 3 chromosomal region 2 gene A protein - Homo sapiens (Human) L3R2A_HUMAN 0.0121 -2.11 2571.6s : 13985.36m/z Small nuclear ribonucleoprotein Sm D3 (snRNP core protein D3) (Sm-D3) - Homo sapiens (Human) SMD3_HUMAN 0.0130 -1.73 2632.0s : 15209.69m/z Fatty acid-binding protein, epidermal (E-FABP) - Homo sapiens (Human) FABPE_HUMAN 0.0130 -2.18 2591.4s : 10292.36m/z Dynein light chain 1, cytoplasmic (Dynein light chain LC8-type 1) - Homo sapiens (Human) DYL1_HUMAN 0.0134 -1.64 2369.0s : 21805.30m/z NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 9 OS- Homo sapiens NDUB9_HUMAN 0.0139 -2.27

2646.1s : 7939.90m/z 40S ribosomal protein S28 - Homo sapiens (Human) RS28_HUMAN 0.0147 -1.66

2636.3s : 6929.97m/z NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 1 (EC 1.6.5.3) - Homo sapiens (Human)NDUB1_HUMAN 0.0200 -1.52 2789.8s : 12777.80m/z SH3 domain-binding glutamic acid-rich-like protein - Homo sapiens (Human) SH3L1_HUMAN 0.0272 -2.17 2843.5s : 17899.84m/z Ubiquitin-conjugating enzyme E2 L3 (EC 6.3.2.19) - Homo sapiens (Human) UB2L3_HUMAN 0.0302 -1.96 2376.1s : 21973.62m/z Peptidyl-prolyl cis-trans isomerase F, mitochondrial OS=Homo sapiens (Human) PPIF_HUMAN 0.0361 -3.26

3. Results

In order to visualize and statistically analyze the value of those three biomarker candidates, visualization by box and whisker plots and T-tests with adjusted raw data were generated. The analysis of LC-MALDI data using Profile Analysis is hindered by the fact that replicates of samples are recognized as independent samples.

Therefore, statistical significances of selected biomarker candidates were independently verified in the GraphPad Prism® Version 5.0 software using the means of replicates, as shown in figure 12.

ATPase inhibitor, mitochondrial

chemosensitive chemoresistant

0 500 1000 1500 2000

Arb. Units

Ubiquitin-60S ribosomal protein L40

chemosensitive chemoresistant

0 500 1000 1500 2000

Arb. Units

Cu/Zn Superoxid Dismutase, mitochondrial

chemosensitive chemoresistant

0 500 1000 1500

Arb. Units

Figure 12: Box and whisker plots for the three biomarker candidates from the Top Down study, chosen for further validation. The means of replicates were plotted with the 5-95 percentile.

The ATPase inhibitor was up regulated 4.94 fold (p-value = 0.0265) in the chemosensitive group, the Ubiquitin- 60S ribosomal protein L40 was up regulated 3.61 fold in the chemosensitive group and the Superoxide dismutase [Cu/Zn] was 1.86 fold up regulated (p-value = 0.0045) in the chemoresistant group. These biomarker candidates were subjected to a technical validation of the workflow by western blotting and NanoPro1000 assays were developed for antibodies directed against the corresponding biomarkers.

3. Results

3.6 Bottom Up proteomic study of intrinsic chemoresistance to FOLFOX