Unusual Suspects: Bone and Cartilage ECM Proteins as Carcinoma Facilitators

SIMPLE SUMMARY: To provide insights into the role of the extracellular matrix (ECM) in health and pathological conditions, it is important to identify tissue-specific proteins, their interacting networks and functions. Latest discoveries suggest that multiple tumors express, and use to their advantage, atypical ECM components that are not found in the cancer tissue of origin. The aim of this review was to summarize and critically assess available information on the expression and function of atypical carcinoma-, bone- and cartilage-specific components of the extracellular matrix. To the best of our knowledge, this topic has not previously been covered by any published review, and thus provides a novel perspective for devising strategies to target tumor stroma as anti-cancer therapeutic options. ABSTRACT: The extracellular matrix (ECM) is the complex three-dimensional network of fibrous proteins and proteoglycans that constitutes an essential part of every tissue to provide support for normal tissue homeostasis. Tissue specificity of the ECM in its topology and structure supports unique biochemical and mechanical properties of each organ. Cancers, like normal tissues, require the ECM to maintain multiple processes governing tumor development, progression and spread. A large body of experimental and clinical evidence has now accumulated to demonstrate essential roles of numerous ECM components in all cancer types. Latest findings also suggest that multiple tumor types express, and use to their advantage, atypical ECM components that are not found in the cancer tissue of origin. However, the understanding of cancer-specific expression patterns of these ECM proteins and their exact roles in selected tumor types is still sketchy. In this review, we summarize the latest data on the aberrant expression of bone and cartilage ECM proteins in epithelial cancers and their specific functions in the pathogenesis of carcinomas and discuss future directions in exploring the utility of this selective group of ECM components as future drug targets.