Abstract P3-12-01: Serum biomarkers identification using quantitative proteomics in patients (pts) with untreated brain metastases from HER2-positive breast cancer receiving capecitabine (C) and lapatinib (L) (UNICANCER LANDsCAPE trial)
Authors: Gonçalves A , Camoin L , Ben Younès I , Romieu G , Campone M , Diéras V , Cropet C , Mahier Aït-Oukhatar C , Dalenc F , Le Rhun E , Labbe-Devilliers C , Borg J-P , Bachelot T 
Published: August 2014

Background: The LANDsCAPE phase II study showed that C+L had a significant antitumor activity in previously untreated brain metastases (BM) from HER2-positive breast cancer (BC), with a central nervous system-objective response rate (CNS-ORR) of 67% and a median time to whole-brain radiotherapy (WBRT) of 8.3 months (43 analysed pts). Thus initial C+L combination might be a viable alternative to immediate WBRT in this setting. In this study, serum samples were collected before and during treatment for proteomic-based approaches to identify predictive biomarkers of treatment response.

Methods: Baseline (BL) and day 21 (D21) serum samples from highly responsive (R, CNS lesions -volumetric response ≥ 75%, n=6) and non-responsive (NR, CNS-stable or progressive disease, n=6) pts were subjected to isobaric Tag for Relative and Absolute Quantification (iTRAQ)-based proteomics. Samples from each condition were pooled to constitute 4 independent mixes ((BL-R, D21-R, BL-NR and D21-NR). Each of them underwent immuno-depletion of highly abundant proteins, concentration, reduction, alkylation and tryptic digestion. Then, each mix was fractionated and subjected to iTRAQ identification and quantitation using nano-liquid chromatography (LC) and electrospray ionisation (ESI)-orbitrap tandem mass spectrometry (MS/MS) (LTQ-orbitrap, Thermofisher). Differentially expressed proteins were analysed using IPA (Ingenuity® Systems) to highlight biological functions and signalling pathways that were most significantly enriched.

Results: iTRAQ-based measurements identified serum proteins with significant (fold-change &gt; 1.5 and p-value &lt; 0.05) differential expression between BL and D21, in R- (n = 38 proteins) and NR- pts (n = 18 proteins). At baseline, 30 proteins were differentially expressed between R-and NR-pts. Among the most differentially expressed proteins, some had been previously described as involved in cancer metastases (between BL and D21: tenascin C, neuropilin-1, Serpin A1, Cathepsin S, prostaglandin D2 synthase, melanoma cell adhesion molecules, procollagen C-endopeptidase enhancer; between R and NR: carnosine dipeptidase 1, endothelial protein C receptor, matrix metallopeptidase 9, cystatin C, lumican, plexin B2, Insulin-like growth factor binding protein acid labile subunit, pro-platelet basic protein, cadherin 5, Protein S). Proteins with differential expression during treatment were involved in various biological processes, including lipid metabolism, small molecule biochemistry, molecular transport, gene expression, cellular growth and proliferation, cellular movement and cancer, as well as various canonical pathways such as acute phase response signalling, LXR/RXR activation and complement system. Interestingly, and as opposed to NR-pts, R-pts specifically showed an overall increase in proteins of acute phase response, with a significant decrease in C-reactive protein (CRP).

Conclusion: iTRAQ-based quantitative proteomics identify serum proteins that could predict the therapeutic response to C+L combination in untreated BM from HER2-positive BC. If validated, such biomarkers may help to select the best therapeutic strategy in this setting.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-12-01.