Entering a New Era of Rational Biomarker Discovery for Early Detection of Melanoma Metastases: Secretome Analysis of Associated Stroma Cells

Abstract

Metastasis in melanoma is associated with poor prognosis. Early detection may thus substantially improve patient survival. Here we present a novel biomarker discovery strategy based on proteome profiling and secretome analysis of primary cells. Tumor associated stroma cells secrete proteins that may act as powerful tumor promoters. This cell cooperativity is reversible and may thus be directly accessible to therapeutic intervention. The onset of these characteristic events seems to precede tumor progression. Thus, proteins specifically secreted by these cells may serve as early disease biomarkers. Due to the leaky nature of newly formed blood vessels and the increased hydrostatic pressure within tumors, secreted proteins are most plausibly shed into the blood. Our analysis strategy is based on three different model systems, including established cultured cell lines, animal model systems, and clinical human samples. The feasibility is demonstrated with secretome and proteome profiles generated from normal human skin fibroblasts in comparison to melanoma-associated fibroblasts isolated from mouse xenografts and fibroblasts from bone marrow of multiple myeloma patients. Further mutual comparisons were enabled including proteome profiles of melanocytes and M24met melanoma cells. All shotgun proteomics data are accessible via the PRIDE database. Among others, the candidate biomarkers GPX5, secreted by melanoma cells, in addition to periostin and stanniocalcin-1, which are expressed by melanoma-associated fibroblasts were identified. In conclusion, this is a novel strategy to identify diagnostic marker proteins aiding early detection of metastatic melanoma and to improve our understanding of pathomechanisms involving the microenvironment to enable the design of novel therapeutic strategies.

SILAC-based quantitative proteomic approach to identify potential biomarkers from the esophageal squamous cell carcinoma secretome

“…10 The cancer secretome has also been studied in different cancers including pancreatic, 11 nasopharyngeal, 12 thyroid, 13 lung adenocarcinoma, 14 oral, 15 ovarian, 16 colorectal, 17 breast 18 and melanoma. 19 A limited number of studies have been carried out in ESCC, wherein researchers have identified a small number of differentially expressed proteins. [20][21][22][23][24] A brief summary of studies carried out thus far is provided in Table 1.…”

Introducing the CPL/MUW proteome database: Interpretation of human liver and liver cancer proteome profiles by referring to isolated primary cells

“…As every pathology-associated cell aberration will be associated with accompanying aberrations in protein expression, the responsible cells may be the perfect targets for discovery of potential biomarkers. We suggest that complex tissue proteome profiles can be better interpreted by referring to previously analyzed profiles of cells [26]. Based on multiple references of the most predominant tissue constituents, the data are pre-sorted according to biological criteria.…”

“…We have established proteome reference profiles of human fibroblasts, keratinocytes, the major blood constituents of dendritic cells (DCs) and endothelial cells at functional distinct states as well as primary and cultured hepatocytes [26][27][28][29][30][31].…”

Biomarkers for Melanoma Diagnosis and the Technologies Used to Identify Them

“…To search for biomarkers useful for the diagnosis of metastases, primary and metastatic cell lines were compared and several candidate biomarkers were successfully discovered (Table 4) (Bernard et al, 2003;Zuidervaart et al, 2006;Al-Ghoul et al, 2008). Proteomics analysis of melanoma-associated fibroblast stromal cells revealed the aberrant expression of several proteins not detected in normal fibroblasts (Paulitschke et al, 2009). These proteins may promote tumor progression.…”

“…Table 5 summarizes a number of different reports in which comprehensive screening of biomarkers from serum and the secretome occurred. By comparing the secretome between melanoma and normal melanocyte, several potential biomarkers were successfully discovered (Pardo et al, 2007;Paulitschke et al, 2009). The traditional serological biomarkers of melanoma such as LDH, S100B and CRP lack sensitivity as early stage melanoma biomarkers.…”