Extracellular matrix protein 1 (ECM1) is a secreted glycoprotein and playing a pivotal role in endochondral bone formation, angiogenesis, and tumour biology. Three splice variants have been identified: ECM1a (540 aa) is most widely expressed, with highest expression in the placenta and heart; ECM1b (415 aa) is differentiation-dependent expressed and found only in tonsil and associated with suprabasal keratinocytes; ECM1c (559 aa) accounts for approximately 15% of skin ECM1. Although ECM1 is not tumor specific, is significantly elevated in many malignant epithelial tumors and is suggested as a possible trigger for angiogenesis, tumor progression and malignancies. It also has been shown to regulate endochondral bone formation, skeletal development and tissue remodeling.

> 88 % as determined by SDS-PAGE