Regulation of a broad array of cellular functions in both normal cells and cancer is controlled through the phosphorylation of unique proteins within multistep signaling pathways. Phosphorylation is directed through hundreds of specific kinases which can be activated through a variety of mechanisms. Not surprisingly, these tightly regulated networks are critical to nearly all cellular functions and can be abnormally activated or suppressed in cancer through both genetic and epigenetic mechanisms (Gross et al., J Clin Invest 125:1780–1789, 2015). Often, these alterations in kinase activity result in tumorigenic changes leading to increased survival and resistance, as well as tumor growth and spread (Fig. 15.1). It has also become evident that aberrant kinase activity plays a central role in a tumor’s ability to evade immune surveillance. As a result, kinase inhibition has emerged as a field of intense study across multiple cancer subtypes, and currently over 25 oncology drugs that target kinases are approved in the United States (Gross et al., J Clin Invest 125:1780–1789, 2015).