Design of recombinant antibody microarrays for urinary proteomics.

PURPOSE: Urinary proteomics has become a key discipline within clinical proteomics for noninvasive diagnosis and monitoring of disease, and biomarker discovery. In order to decipher complex proteomes, high demands will, however, be placed upon the methodology applied. The purpose of this study was to develop a recombinant antibody microarray platform for urinary proteomics. EXPERIMENTAL DESIGN: We adopted our previously in-house developed recombinant antibody microarray set-up and redesigned the platform for urinary proteomics. In this process, the key antibody array assay parameters, such as sample handling, sample labeling protocol, and assay conditions, etc, reflecting the unique properties of urine as sample format, were addressed and reoptimized in a step-by-step procedure. RESULTS: In this proof-of-concept study, we have designed the first generation of a recombinant antibody microarray technology platform for urinary proteomics. The results showed that multiplexed, sensitive (pg/mL range), and reproducible urine protein expression profiling could be performed targeting directly labeled, nonfractionated urine. CONCLUSION AND CLINICAL RELEVANCE: We have demonstrated that crude, directly labeled urine samples could be profiled in a rapid, reproducible, sensitive, and multiplexed manner after minimal sample prehandling. These findings could potentially pave the way for enhanced urinary proteomics and understanding of renal physiology with implications in both health and disease.

Molecular serum portraits in patients with primary breast cancer predict the development of distant metastases.

The risk of distant recurrence in breast cancer patients is difficult to assess with current clinical and histopathological parameters, and no validated serum biomarkers currently exist. Using a recently developed recombinant antibody microarray platform containing 135 antibodies against 65 mainly immunoregulatory proteins, we screened 240 sera from 64 patients with primary breast cancer. This unique longitudinal sample material was collected from each patient between 0 and 36 mo after the primary operation. The velocity for each serum protein was determined by comparing the samples collected at the primary operation and then 3-6 mo later. A 21-protein signature was identified, using leave-one-out cross-validation together with a backward elimination strategy in a training cohort. This signature was tested and evaluated subsequently in an independent test cohort (prevalidation). The risk of developing distant recurrence after primary operation could be assessed for each patient, using her molecular portraits. The results from this prevalidation study showed that patients could be classified into high- versus low-risk groups for developing metastatic breast cancer with a receiver operating characteristic area under the curve of 0.85. This risk assessment was not dependent on the type of adjuvant therapy received by the patients. Even more importantly, we demonstrated that this protein signature provided an added value compared with conventional clinical parameters. Consequently, we present here a candidate serum biomarker signature able to classify patients with primary breast cancer according to their risk of developing distant recurrence, with an accuracy outperforming current procedures.

Surrogate antigens as targets for proteome-wide binder selection.

In the past decade, many initiatives were taken for the development of antibodies for proteome-wide studies, as well as characterisation and validation of clinically relevant disease biomarkers. Phage display offers many advantages compared to antibody generation by immunisation because it is an unlimited resource of affinity reagents without batch-to-batch variation and is also amendable for high throughput in contrast to conventional hybridoma technology. One of the major bottlenecks to proteome-wide binder selection is the limited supply of suitable target antigens representative of the human proteome. Here, we provide proof of principle of using easily accessible, cancer-associated protein epitope signature tags (PrESTs), routinely generated within the Human Protein Atlas project, as surrogate antigens for full-length proteins in phage selections for the retrieval of target-specific binders. These binders were subsequently tested in western blot, immunohistochemistry and protein microarray application to demonstrate their functionality.