ERBB2 and cancer: However, in many types of cancer the pathway is activated by genomic aberrations, such as gene amplification (e.g., HER2), gene deletion or loss-of-function mutations in genes encoding inhibitory proteins (e.g., PTEN), or specific activating mutations in one of the key pathway-activating components (e.g., EGFR, HER2, PIK3CA) [52].