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 & 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.).