Proteomics of uveal melanoma: a minireview

Thrombin Cleavage of Osteopontin and the Host Anti-Tumor Immune Response

Osteopontin (OPN) is a multi-functional protein that is involved in various cellular processes such as cell adhesion, migration, and signaling. There is a single conserved thrombin cleavage site in OPN that, when cleaved, yields two fragments with different properties from full-length OPN. In cancer, OPN has tumor-promoting activity and plays a role in tumor growth and metastasis. High levels of OPN expression in cancer cells and tumor tissue are found in various types of cancer, including breast, lung, prostate, ovarian, colorectal, and pancreatic cancer, and are associated with poor prognosis and decreased survival rates. OPN promotes tumor progression and invasion by stimulating cell proliferation and angiogenesis and also facilitates the metastasis of cancer cells to other parts of the body by promoting cell adhesion and migration. Furthermore, OPN contributes to immune evasion by inhibiting the activity of immune cells. Thrombin cleavage of OPN initiates OPN's tumor-promoting activity, and thrombin cleavage fragments of OPN down-regulate the host immune anti-tumor response.

Characterization of Extracellular vesicles isolated from different Liquid biopsies of uveal melanoma patients

Purpose:

Uveal melanoma (UM) is the most common intraocular malignant tumor in adults. Extracellular vesicles (EVs) have been extensively studied as a biomarker to monitor disease in patients. The study of new biomarkers in melanoma patients could prevent metastasis by earlier diagnosis. In this study, we determined the proteomic profile of EVs isolated from aqueous humor (AH), vitreous humor (VH), and plasma from UM patients in comparison with cancer-free control patients.

Methods:

AH, VH and plasma were collected from seven patients with UM after enucleation; AH and plasma were collected from seven cancer-free patients with cataract (CAT; control group). EVs were isolated using the membrane-based affinity binding column method. Nanoparticle tracking analysis (NTA) was performed to determine the size and concentration of EVs. EV markers, CD63 and TSG101, were assessed by immunoblotting, and the EV proteome was characterized by mass spectrometry.

Results:

Mean EV concentration was higher in all analytes of UM patients compared to those in the CAT group. In the UM cohort, the mean concentration of EVs was significantly lower in AH and plasma than in VH. In contrast, the mean size and size distribution of EVs was invariably identical in all analyzed analytes and in both studied groups (UM vs. CAT). Mass spectrometry analyses from the different analytes from UM patients showed the presence of EV markers.

Conclusion:

EVs isolated from AH, VH, and plasma from patients with UM showed consistent profiles and support the use of blood to monitor UM patients as a noninvasive liquid biopsy.

Evaluation of a Three-Marker Panel for the Detection of Uveal Melanoma Metastases: A Single-Center Retrospective Analysis

Simple Summary

Blood-based B-cell activating factor (BAFF), growth differentiation factor-15 (GDF-15) and osteopontin (OPN) have been reported to be biomarkers for the uveal melanoma (UM) metastases. This work intended to assess their kinetics and to evaluate their significance as a three-marker panel for clinical practice. Our results not only provided their cutoff values for differentiating the metastatic patients from non-metastatic patients, but also confirmed that the three-marker panel outperformed any single biomarker in distinguishing metastatic patients. Besides, the increasing trends of the levels of three biomarkers were detected in the two-year period before the imaging diagnosis of metastases. The multiplex panel of BAFF, GDF-15 and OPN might be a utilizable implementation for the detection of UM metastases. Since it is a retrospective pilot work, more well-designed prospective studies employing larger cohorts are still needed to validate the findings.

Abstract

Blood-based B-cell activating factor (BAFF), growth differentiation factor-15 (GDF-15) and osteopontin (OPN) have been identified to be promising biomarkers for the metastases of uveal melanoma (UM). This study intended to assess their kinetics and to evaluate their significance as a three-marker panel. A group of 36 UM patients with and 137 patients without metastases were included in the study. Their plasma OPN levels were measured by ELISA; serum BAFF and GDF-15 levels were determined with a Luminex MAGPIX system. Receiver operating characteristic (ROC) analysis was performed to calculate the cutoff values of the three markers for identifying the patients with metastases. The ability to identify patients with metastases was compared between the single markers and the combination as a three-marker panel. By using the Student’s t-test, we also investigated the kinetic changes of the levels of BAFF, GDF-15 and OPN across six periods (i.e., 0–6 months, 6–12 months, 12–18 months, 18–24 months, >24 months and post-metastasis) before the imaging diagnosis of metastases. By maximizing the Youden’s index, the serum GDF-15 level of 1209 pg/mL and the plasma OPN level of 92 ng/mL were identified to have the best performance for distinguishing the metastatic patients from non-metastatic patients. The three-marker panel offered a better performance in distinguishing patients with metastases, with an area under the curve of 0.802, than any single biomarker. Increasing trends of the levels of three biomarkers were observed in the two-year period before the imaging diagnosis of metastases. The combined panel of BAFF, GDF-15 and OPN might be a utilizable implementation for the detection of UM metastases. In the bioinformatics study with two external datasets, the high expression of gene BAFF and GDF-15 in primary UM tissues was identified to be associated with poor overall survival rates. As the current work is a single-center retrospective study, more well-designed prospective investigations employing larger cohorts are urgently needed to validate our findings.

An Insight into the Proteome of Uveal Melanoma-Derived Ectosomes Reveals the Presence of Potentially Useful Biomarkers

Cancer cells are known to release extracellular vesicles that often promote disease development and progression. The present study investigated the protein content and glycosylation pattern of ectosomes released in vitro by a human primary uveal melanoma Mel202 cell line. Ectosomes released by Mel202 cells were isolated from conditioned media using sequential centrifugation, and a nano-LC-MS/MS approach was used to determine their protein content. Subsequently, proteins from ectosomes, the whole cell extracts, and the membrane fractions were probed with a panel of lectins using Western blotting and flow cytometry to reveal characteristic glycan structures. As many as 2527 unique proteins were identified, and many of them are known to be involved in cancer cell proliferation and altered metabolism, tumor invasion, metastasis, or drug resistance. Lectin-based studies revealed a distinct glycosylation pattern between Mel202-derived ectosomes and the parental cell membranes. Selective enrichment of ectosomal proteins with bisected complex type N-glycans and α2,6-linked sialic acids may be significant for ectosome formation and sequestration. Differences in the surface glycosylation of Mel202 cells and ectosomes supports recent findings that the budding of ectosomes occurs within strictly determined fragments of the plasma membrane, and thus ectosomes contain a unique protein and glycan composition.

PARP Inhibition Increases the Response to Chemotherapy in Uveal Melanoma

Uveal melanoma (UM) remains without effective therapy at the metastatic stage, which is associated with BAP-1 (BRCA1 associated protein) mutations. However, no data on DNA repair capacities in UM are available. Here, we use UM patient-derived xenografts (PDXs) to study the therapeutic activity of the PARP inhibitor olaparib, alone or in combination. First, we show that the expression and the activity of PARP proteins is similar between the PDXs and the corresponding patient’s tumors. In vivo experiments in the PDX models showed that olaparib was not efficient alone, but significantly increased the efficacy of dacarbazine. Finally, using reverse phase protein arrays and immunohistochemistry, we identified proteins involved in DNA repair and apoptosis as potential biomarkers predicting response to the combination of olaparib and dacarbazine. We also observed a high increase of phosphorylated YAP and TAZ proteins after dacarbazine + olaparib treatment. Our results suggest that PARP inhibition in combination with the alkylating agent dacarbazine could be of clinical interest for UM treatment. We also observe an interesting effect of dacarbazine on the Hippo pathway, confirming the importance of this pathway in UM.

A multiplex immunoassay of serum biomarkers for the detection of uveal melanoma

Background

Approximately 50% of uveal melanoma (UM) patients develop metastases preferentially in the liver leading to death within 15 months. Currently, there is no effective treatment for metastatic UM, in part because the tumor burden is typically high when liver metastases are detected through abnormal liver function tests (LFTs) or imaging studies. The use of LFTs results followed by diagnostic tests has high specificity and predictive values but low sensitivity, and better tests are needed for early diagnosis of the primary tumor as well as its metastatic spread. To evaluate serum biomarkers for the early detection of UM, multiplex immunoassays were developed.

Methods

Magnetic bead-based multiplex immunoassays were developed for the selected serum biomarkers using a Bio-Plex 200 system. The dynamic ranges, lower limits of detection and quantification, cross-reactivity, and intra- and inter-assay precision were assessed. All proteins were analyzed in sera of 48 patients diagnosed with UM (14 metastatic, 9 disease–free (DF) ≥ 5 years, 25 unknown) and 36 healthy controls. The performance of the biomarkers was evaluated individually and in combination for their ability to detect UM.

Results

A 7-plex immunoassay of OPN, MIA, CEACAM-1, MIC-1, SPON1, POSTN and HSP27 was developed with negligible cross-reactivity, recovery of 84–105%, and intra-assay and inter-assay precision of 2.3–7.5% or 2.8–20.8%, respectively. Logistic regression identified a two-marker panel of HSP27 and OPN that significantly improved the individual biomarker performance in discriminating UM from healthy controls. The improved discrimination of a two-marker panel of MIA and MIC-1 was also observed between metastatic UM and DF, however not statistically significant due to the small sample size.

Conclusions

The multiplex immunoassay provides sufficient analytical performance to evaluate serum biomarkers that complement each other in detection of UM, and warrants further validation with a larger number of patient samples.

Electronic supplementary material

The online version of this article (10.1186/s12014-019-9230-8) contains supplementary material, which is available to authorized users.

Somatostatin Receptors as Molecular Targets in Human Uveal Melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, with an incidence of 4–5 cases per million. The prognosis of UM is very poor. In the present study, our aim was to investigate the expression of mRNA and protein for somatostatin receptor types-1, -2, -3, -4, -5 (SSTR-1–5) in human UM tissue samples and in OCM-1 and OCM-3 human UM cell lines by qRT-PCR, western blot and ligand competition assay. The mRNA for SSTR-2 showed markedly higher expression in UM tissues than SSTR-5. The presence of SSTRs was demonstrated in 70% of UM specimens using ligand competition assay and both human UM models displayed specific high affinity SSTRs. Among the five SSTRs, the mRNA investigated for SSTR-2 and SSTR-5 receptors was strongly expressed in both human UM cell lines, SSTR-5 showing the highest expression. The presence of the SSTR-2 and SSTR-5 receptor proteins was confirmed in both cell lines by western blot. In summary, the expression of somatostatin receptors in human UM specimens and in OCM-1 and OCM-3 human UM cell lines suggests that they could serve as a potential molecular target for therapy of UM using modern powerful cytotoxic SST analogs targeting SSTR-2 and SSTR-5 receptors.

Characterization of luteinizing hormone-releasing hormone receptor type I (LH-RH-I) as a potential molecular target in OCM-1 and OCM-3 human uveal melanoma cell lines

Introduction

Uveal melanoma (UM) is the most common primary intraocular malignancy with very poor prognosis. Conventional chemotherapy only rarely prolongs the survival, therefore patients require novel treatment modalities. The discovery of specific receptors for hypothalamic hormones on cancer cells has led to the development of radiolabeled and cytotoxic hormone analogs.

Materials and methods

In the present study, our aim was to investigate the expression of mRNA for receptors of luteinizing hormone-releasing hormone type I (LH-RH-I) and LH-RH ligand in OCM-1 and OCM-3 human uveal melanoma cell lines. The presence and binding characteristics of LH-RH-I receptor protein was further studied by Western blot, immunocytochemistry and ligand competition assay. The expression of mRNA and protein for LH-RH-I receptors has been also studied using tumor samples originating from nude mice xenografted with OCM-1 or OCM-3 cells.

Results

The mRNA for LH-RH-I receptor has been detected in OCM-1 and OCM-3 cell lines and was found markedly higher in OCM-3 cells. The mRNA for LH-RH-I receptors was also observed in both UM xenograft models in vivo with higher levels in OCM-3. The presence of LH-RH-I receptor protein was found in both cell lines in vitro by immunocytochemistry and Western blot, and also in tumor tissue samples grown in nude mice by Western blot. Both human uveal melanoma models investigated showed specific high affinity receptors for LH-RH-I using ligand competition assay. The mRNA for LH-RH ligand has also been detected in OCM-1 and OCM-3 cell lines and cancer tissues.

Conclusion

The demonstration of the expression of LH-RH-I receptors in OCM-1 and OCM-3 human UM cell lines suggests that they could serve as potential molecular target for therapy. Our findings support the development of new therapeutic approaches based on cytotoxic LH-RH analogs or modern powerful antagonistic analogs of LH-RH targeting LH-RH-I receptors in UM.

Peptidome profiling of human serum of uveal melanoma patients based on magnetic bead fractionation and mass spectrometry

AIM

To find new biomarkers for uveal melanoma (UM) by analyzing the serum peptidome profile.

METHODS

Proteomic spectra in patients with UM before and after operation were analyzed and compared with those of healthy controls. Magnetic affinity beads were used to capture serum peptides and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer were used to compile serum peptide profiles.

RESULTS

A panel of 49 peptides were differentially expressed between UM patients and controls, of which 33 peptides were of higher intensities in patient group and 16 peptides were of higher intensities in control group. Based on combined use of these potential markers, peptides with mean molecular masses of 1467 and 9289.0 Da provide high sensitivity (83.3%), specificity (100%) and accuracy rate (93.0%) together to differentiate melanoma patients from healthy controls. At the time point of 6mo postoperatively, the levels of many peptides differentially expressed before surgery showed no more statistical difference between the patients and the control group. Fibrinogen α-chain precursors were identified as potential UM markers.

CONCLUSION

We have shown that a convenient and fast proteomic technique, affinity bead separation and MALDI-TOF analysis combined with bioinformatic software, facilitates the identification of novel biomarkers for UM.

Concurrence of chromosome 3 and 4 aberrations in human uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy with a very poor prognosis. The most frequent chromosome aberration in UM is the monosomy of chromosome 3. Previously, we demonstrated that ~50% of UMs express type-I receptor for luteinizing hormone‑releasing hormone (LH-RH-R). The gene encoding LH-RH-R is located in chromosome 4 (location: 4q21.2); however, the occurrence of numerical aberrations of chromosome 4 have never been studied in UM. In the present study, we investigated the abnormalities of chromosome 3 and 4, and the possible correlation between them, as well as with LH-RH-R expression. Forty-six specimens of UM were obtained after enucleation. Numerical aberrations of chromosome 3 and 4 were studied by fluorescence in situ hybridization (FISH). Chromosome 4 was detected in normal biparental disomy only in 14 (30%) samples; however, 32 cases (70%) showed more than 2 signals/nucleus. Monosomy of chromosome 3 could be found in 16 (35%) samples. In 6 specimens (13%), more than 2 copies of chromosome 3 were found, while normal biparental disomy was detected in 24 (52%) samples. Statistical analysis indicated a statistically significant (p<0.05) correlation between the copy number of chromosome 3 and 4. Moreover, moderate difference was revealed in the survival rate of the UM patients with various pathological profiles. No correlation was found between chromosome aberrations and LH-RH-R expression. Our results clearly demonstrate abnormalities in chromosome 3 and 4 and the incidence of the monosomy of chromosome 3 in human UM. In summary, our results provide new incite concerning the genetic background of this tumor. Our findings could contribute to a more precise determination of the prognosis of human UM and to the development of new therapeutic approaches to this malignancy.

Uveal Melanoma: Current Trends in Diagnosis and Management

Uveal melanoma, which is the most common primary intraocular malignancy in adults, arises from melanocytes within the iris, ciliary body and choroid. The diagnosis is based principally on clinical examination of the tumor with biomicroscopy and indirect ophthalmoscopy and confirmed by diagnostic techniques such as ultrasonography, fundus fluorescein angiography and optical coherence tomography. The clinical diagnosis of posterior uveal melanomas can be made when the classical appearance of a pigmented dome-shaped mass is detected on dilated fundus exam. Uveal melanomas classically show low to medium reflectivity on A-scan ultrasonography and on B-scan ultrasonography the tumor appears as a hyperechoic, acoustically hollow intraocular mass. Management of a suspicious pigmented lesion is determined by its risk factors of transforming into a choroidal melanoma, such as documentation of growth, thickness greater than 2 mm, presence of subretinal fluid, symptoms and orange pigment, margin within 3 mm of the optic disc, and absence of halo and drusen. Advances in the diagnosis and local and systemic treatment of uveal melanoma have caused a shift from enucleation to eye-conserving treatment modalities including transpupillary thermotherapy and radiotherapy over the past few decades. Prognosis can be most accurately predicted by genetic profiling of fine needle aspiration biopsy of the tumor before the treatment, and high-risk patients can now be identified for clinical trials that may lead to target-based therapies for metastatic disease and adjuvant therapy which aims to prevent metastatic disease.

iTRAQ Quantitative Proteomic Comparison of Metastatic and Non-Metastatic Uveal Melanoma Tumors

BACKGROUND

Uveal melanoma is the most common malignancy of the adult eye. The overall mortality rate is high because this aggressive cancer often metastasizes before ophthalmic diagnosis. Quantitative proteomic analysis of primary metastasizing and non-metastasizing tumors was pursued for insights into mechanisms and biomarkers of uveal melanoma metastasis.

METHODS

Eight metastatic and 7 non-metastatic human primary uveal melanoma tumors were analyzed by LC MS/MS iTRAQ technology with Bruch's membrane/choroid complex from normal postmortem eyes as control tissue. Tryptic peptides from tumor and control proteins were labeled with iTRAQ tags, fractionated by cation exchange chromatography, and analyzed by LC MS/MS. Protein identification utilized the Mascot search engine and the human Uni-Prot/Swiss-Protein database with false discovery ≤ 1%; protein quantitation utilized the Mascot weighted average method. Proteins designated differentially expressed exhibited quantitative differences (p ≤ 0.05, t-test) in a training set of five metastatic and five non-metastatic tumors. Logistic regression models developed from the training set were used to classify the metastatic status of five independent tumors.

RESULTS

Of 1644 proteins identified and quantified in 5 metastatic and 5 non-metastatic tumors, 12 proteins were found uniquely in ≥ 3 metastatic tumors, 28 were found significantly elevated and 30 significantly decreased only in metastatic tumors, and 31 were designated differentially expressed between metastatic and non-metastatic tumors. Logistic regression modeling of differentially expressed collagen alpha-3(VI) and heat shock protein beta-1 allowed correct prediction of metastasis status for each of five independent tumor specimens.

CONCLUSIONS

The present data provide new clues to molecular differences in metastatic and non-metastatic uveal melanoma tumors. While sample size is limited and validation required, the results support collagen alpha-3(VI) and heat shock protein beta-1 as candidate biomarkers of uveal melanoma metastasis and establish a quantitative proteomic database for uveal melanoma primary tumors.