ERBB3 and squamous cell carcinoma: Shames and colleagues analyzed HRG and ErbB3 mRNA levels in more than 750 tumors of diverse origin, including over 150 primary and recurrent tissue samples from patients with squamous cell carcinoma of the head and neck.53 They found that high HRG expression is associated with activation of ErbB3 (as assessed by ErbB3 phosphorylation) and that HRG expression was significantly higher in recurrent specimens compared with patient-matched and unmatched therapy-naïve specimens.