Multi-platform Affinity Proteomics Identify Proteins Linked to Metastasis and Immune Suppression in Ovarian Cancer Plasma

A central reason behind the poor clinical outcome of patients with high-grade serous carcinoma (HGSC) of the ovary is the difficulty in reliably detecting early occurrence or recurrence of this malignancy. Biomarkers that provide reliable diagnosis of this disease are therefore urgently needed. Systematic proteomic methods that identify HGSC-associated molecules may provide such biomarkers. We applied the antibody-based proximity extension assay (PEA) platform (Olink) for the identification of proteins that are upregulated in the plasma of OC patients. Using binders targeting 368 different plasma proteins, we compared 20 plasma samples from HGSC patients (OC-plasma) with 20 plasma samples from individuals with non-malignant gynecologic disorders (N-plasma). We identified 176 proteins with significantly higher levels in OC-plasma compared to N-plasma by PEA (p < 0.05 by U-test; Benjamini-Hochberg corrected), which are mainly implicated in immune regulation and metastasis-associated processes, such as matrix remodeling, adhesion, migration and proliferation. A number of these proteins have not been reported in previous studies, such as BCAM, CDH6, DDR1, N2DL-2 (ULBP2), SPINT2, and WISP-1 (CCN4). Of these SPINT2, a protease inhibitor mainly derived from tumor cells within the HGSC microenvironment, showed the highest significance (p < 2 × 10⁻⁷) similar to the previously described IL-6 and PVRL4 (NECTIN4) proteins. Results were validated by means of the aptamer-based 1.3 k SOMAscan proteomic platform, which revealed a high inter-platform correlation with a median Spearman ρ of 0.62. Likewise, ELISA confirmed the PEA data for 10 out of 12 proteins analyzed, including SPINT2. These findings suggest that in contrast to other entities SPINT2 does not act as a tumor suppressor in HGSC. This is supported by data from the PRECOG and KM-Plotter meta-analysis databases, which point to a tumor-type-specific inverse association of SPINT2 gene expression with survival. Our data also demonstrate that both the PEA and SOMAscan affinity proteomics platforms bear considerable potential for the unbiased discovery of novel disease-associated biomarkers.

A set of conformationally well-defined L/D-peptide epitopes provides a serological bar code for autoantibody subtypes

Which conformational parameters lead to an antibody-affine peptide antigen? And in how many different conformations can we actually present the respective conformational epitope? To provide answers from a chemical point of view, we direct the bending and tethering of peptide backbones by the utilisation of a hydrophobic cluster, disulfides, and d-amino acids. Each mutation is employed pairwise on directly opposite sides of a β-hairpin. In combination, these synthetic modules guide the formation of complementary β-sheet-like structures, whereby the oppositely configured (l/d-)bi-disulfide pairs form with high regioselectivity. The conformational properties of the peptides are assessed by NMR spectroscopy and correlated with their antibody affinity in ELISA. From a pool of thus designed peptide antigens with distinctive complementary affinities against known rheumatoid arthritis (RA) autoantibodies, we select a set of epitopes for an immunoassay with sera of RA patients. We want to put emphasis on the idea, that the different conformational properties of the chosen antigens, containing the same epitope sequence, are mirrored in the distribution of autoantibody subtypes (or of the antibody polyclonality, respectively). Such directly comparable information can only be delivered by a set of peptides, rather than a single one. The hairpin-restriction technology of l/d-configured bi-disulfide amino acid pairs is not limited to RA but applicable to other shape-persistent hairpin motifs which are supposed to identify subgroups of protein receptors.

Synthesis of a biological active β-hairpin peptide by addition of two structural motifs

The idea of privileged scaffolds - that there seem to be more bioactive compounds found around some structures than others - is well established for small drug molecules, but has little significance for standalone peptide secondary structures whose adaptable shapes escape the definition of a 3D motif in the absence of a protein scaffold. Here, we joined two independent biological functions in a single highly restricted peptide to support the hypothesis that the β-hairpin shape is the common basis of two otherwise unrelated biological recognition processes. To achieve this, the hydrophobic cluster HWX₄LV from the decapeptide cyclic hairpin model peptide C¹-C¹⁰cyclo-CHWEGNKLVC was included in the bicyclic peptide 2. The designed β-hairpin peptide C⁴-C¹⁷, C⁸-C¹³bicyclo-KHQCHWECTZGRCRLVCGRSGS (2, Z=citrulline), serves, on the one hand, as a specific epitope for rheumatoid autoantibodies and, on the other hand, shows a not negligible antibiotic effect against the bacterial strain E. coli AS19.

Paraneoplastic brainstem encephalitis in a patient with exceptionally long course of a metastasized neuroendocrine rectum neoplasm

Background

Paraneoplastic neurological syndromes (PNS) have frequently been described in patients with lung or breast cancer. However, some reports also described a correlation to carcinoid tumors, probably triggered via the excessive release of hormones.

Case presentation

We report the case of a 40-year-old woman that was diagnosed with a neuroendocrine neoplasm (NEN) of the rectum and multiple synchronous liver metastases ten years ago. She initially responded well to transarterial chemoembolization (TACE), resulting in prolonged disease stabilization. However, ten years after initial diagnosis the patient developed unspecific neurological symptoms that could not be classified by standard neurological diagnostic work-up. Special laboratory analysis revealed a high titer of anti-Ri (ANNA-2), a well-characterized antibody that is associated with paraneoplastic neurologic syndromes. The patient’s symptoms improved markedly after a 5-day-course of high-dose glucocorticoid therapy. To our knowledge, this is the first report of a Ri-positive PNS in a patient with hormone-negative rectal NEN.

Conclusion

PNS can complicate the patient’s clinical course, response to treatment, impact prognosis and even be interpreted as metastatic spread. However, owing to their rarity, the knowledge of these syndromes is very helpful in order to be able to provide evidence-based diagnostic and therapeutic approaches.

Surfactant protein B intron 4 variation in German patients with COPD and acute respiratory failure

Chronic obstructive pulmonary disease (COPD) is a major health problem. Genetic factors that contribute to the disease have been postulated. The pulmonary surfactant protein B (SP-B), which is essential for normal lung function, is considered as a candidate gene for COPD in this case-control study. We studied the SP-B intron 4 size variants in 346 individuals. This group consisted of 118 patients with chronic bronchitis or COPD, including 24 patients with acute respiratory failure (ARF) in COPD, 118 matched controls without pulmonary disease and 110 healthy individuals (population control). The frequency of intron 4 variants was similar in either control group (10.9%, 14.4%, respectively), with a small increase in the COPD group (18.6%). This increase was due to a high increase of intron 4 variants in the ARF subgroup (37.5%, p = 0.003, OR 4.9, 95% CI: 1.76-13.6). The data indicate that SP-B intron 4 variants may associate with increased risk of ARF in COPD and may be used as a marker of susceptibility in this disease subgroup.