ERBB4 and Friedreich ataxia: To investigate the expression of ErbB molecules (ErbB1–ErbB4) in the membrane of HNSCCs proficient in the FA pathway (FA-proficient), cell lines from patients with sporadic cancer (CAL27 and CAL33), as well as gene-corrected HNSCCs cell lines from patients with FA (see materials and methods section; VU-1131+FANCC and VU-1365+FANCA) were used.