A novel breast cancer screening platform: An epitope-based biomarker coupled to electrochemical sensor

9

Background: The subtractive proteomic selection technology called Phage Display (PD) has been extensively used by our group in the discovery of high affinity ligands to target tissues and molecules. We have selected specific ligands against IgG purified from BC tissues, which was successfully coupled to an electrochemical sensor to detect the tumor-specific immune response. Methods: After PD selections, all immunoreactive peptide ligands were further characterized by DNA sequencing, in vitro translated and submitted to bioinformatic analyses. Further validations were performed by ELISA. We then used one synthetic peptide (SF4) for the construction of an immunosensor, which was applied to patients and control samples for final validation. Electrochemical impedance spectroscopy (EIS) was performed. Results: We have selected the F4 peptide for final validation and sensor construction due to its capability of detecting IgG in the peripheral blood and the excellent ELISA ratio BC:BBD, discriminating more than 70% of BC patients. The synthetic peptide reached a good precision in BC diagnosis (68%), but surprisingly, the selected F4 clone presented the highest sensitivity and specificity, (77.8% and 85.7%, respectively), suggesting that it can be used as a diagnostic reagent for early BC screening prior to imaging and pathological analyses. The electrochemical sensor that was built with the epitope-based peptide discriminated all IgG from BC and healthy individuals. Results with the EIS sensor demonstrated that the presence of (SF4) peptide IgG generated higher resistivity (-Z ') compared to the system containing only the peptide or the control sera. This is justified by the fact that with the immobilized biological peptide layer was correctly conjugated with the IgG forming an antigen: antibody complex that led to an increased resistance to the charge transfer system, producing a decrease in electron transfer between the iron-coupled / ferricyanide redox and the electrode surface. Conclusions: An electrochemical sensor using an epitope-based biomarker was developed, which allows for the first time BC screening using a very simple platform that could be an important auxiliary tool to mammography imaging.

Dynamic dialog between cytokeratin 18 and annexin A1 in breast cancer: a transcriptional disequilibrium

Cytokeratins (CKs) constitute the cytoskeletal network and are regulated by post-translational modifications, acting not only as a mechanical support, but also in cell signaling and regulatory processes. Signaling is mediated by CK-associated proteins, such as Annexin A1 (ANXA1), a ligand of the CK18/CK8 complex. ANXA1 has a pivotal role in cellular and immunological responses, and together with CK18 have been implicated in several processes related to malignant transformation in breast cancer (BC). Our aim was to demonstrate how their interaction might be linked to BC development. We investigated transcript levels, protein expression and distribution for both targets in breast tissues of 92 patients (42 BCs and 50 benign diseases) using qPCR and immunohistochemistry, respectively. ANXA1 and CK18 mRNAs were inversely correlated, and their ratio in each TNM stage significantly differentiated BC from benign diseases (OR=5.62). These differences did not mirror tissue protein levels, but a significant dichotomous protein distribution in tumor tissues was observed, differing from the expected co-localization observed during cell homeostasis. The disequilibrium of transcriptional levels between ANXA1/CK18 and alterations in their tissue distribution are present either in initial events or tumor progression, which suggest a critical event in BC. The broken dialog between ANXA1 and CK18 in normal breast tissues may play a critical role in BC development, and together may be used as combined targets for BC diagnostics.

A novel highly reactive Fab antibody for breast cancer tissue diagnostics and staging also discriminates a subset of good prognostic triple-negative breast cancers

The discovery of novel markers for breast cancer (BC) has been recently relied on antibody combinatorial libraries and selection through phage display. We constructed a recombinant Fab library, and after selections against BC tissues, the FabC4 clone was thoroughly investigated by immunohistochemistry in 232 patients with long-term follow-up. The FabC4 ligand was determined by mass spectrometry. The FabC4 expression was associated with younger age, lack of progesterone receptor, higher histological grades and non-luminal subtypes, and it also identified a subset of good prognostic triple-negative BCs, possibly targeting a conformational epitope of Cytokeratin-10 (CK10). This new CK10-epitope specific antibody may open new possibilities in diagnostic and therapeutic strategies.