Growth factors mediate their diverse biologic responses (regulation of cellular proliferation. differentiation. migration and survival) by binding to and activating cell-surface receptors with intrinsic protein kinase activity named Receptor Tyrosine Kinases (RTKs). About 60 RTKs have been identified and can be classified into more than 16 different receptor families. https://www.nacrack.com/hot-choice-Open-Box-Verona-Wig-by-BelleTress-Heat-Friendly-Synthetic-Hair-Average-Cap-Buttered-Toast-R-great-buy/