ERBB4 and breast cancer: The relationship between the variable expression of DNA damage response proteins (p53, BRCA1, γH2AX, pChk2), DNA damage-sensitive tumor suppressors (WWOX, FHIT), WWOX-interacting proteins (Ap2- α and γ, ERBB4), cancer subtype, and clinical factors was tested in a tissue microarray analysis of 479 cases of breast cancer samples.