Biological characteristics of CCN proteins in tumor development.

The extracellular membrane (ECM) is no longer regarded as inert, rather it has multiple versatile physiologic functions. Its diverse composition is implicated in each step of cancer progression including inflammation, angiogenesis, tumor invasion and metastasis. In addition to structural proteins, the ECM also contains a family of non-structural proteins called matricellular proteins. The six secreted CCN proteins, which belong to the matricellular protein family, include the following: Cyr61 (CCN1), CTGF (CCN2), Nov (CCN3), WISP- 1 (CCN4), WISP-2 (CCN5) and WISP-3(CCN6). These proteins are capable of modulating a variety of biological processes in health as well as in disease conditions. In tumor development and in tumor microenvironment, CCN proteins can influence multiple facets of pathophysiological processes including cellular proliferation, invasion and metastasis. This review has attempted a cohesive look at the CCN family protein functions in a tumor-specific manner.