Heregulin-beta 1 also known as neuregulin-1 (NRG-1) is a member of the epidermal growth factor (EGF) family of growth factors and acts as a ligand for ErbB family receptor tyrosine kinases (Britsch et al.). Heregulin/neuregulin is a family of structurally related polypeptide growth factors derived from alternatively spliced genes (NRG1, NRG2, NRG3, and NRG4). Heregulin-beta 1 plays an important role during the development of the nervous system, heart, and mammary glands (Britsch). Heregulin-beta 1 is expressed in neuronal cells, and modulates cell growth and differentiation of the cells during development and wound healing (Mei and Xiong). It has been implicated through in vivo and in vitro studies that heregulin-beta 1/ErbB signaling is crucial for multiple aspects of cardiovascular development and protects the heart from ischemic injury (Odiete et al.). Heregulin-beta 1 also promotes invasiveness and metastasis of breast cancer cells (Hutcheson et al.). It has also been shown that heregulin-beta 1 has a role in the growth and maintenance of human embryonic stem cells (Wang et al.).