Prevalence and role of HER2 mutations in cancer.

HER2 activating mutations act as oncogenic drivers in various cancer types. In the clinic, they can be identified by next generation sequencing (NGS) in either tumor biopsies or circulating cell-free DNA (cfDNA). Preclinical data indicate that HER2 "hot spot" mutations are constitutively active, have transforming capacity in vitro and in vivo and show variable sensitivity to anti-HER2 based therapies. Recent clinical trials also revealed activity of HER2-targeted drugs against a variety of tumors harboring HER2 mutations. Here, we review the prevalence and type of HER2 mutations identified in different human cancers, their biochemical and biological characterization, and their sensitivity to anti HER2-based therapies in both preclinical and clinical settings.