A recent in vitro study has suggested that overexpression of ERBB2 may
mediate breast tumour progression and metastasis by inhibiting the tr
anscription of the E-cadherin (E-CD) gene. To test this hypothesis in
human breast cancer in vivo, we studied the relationship between the e
xpression of both molecules in 247 breast carcinomas immunohistochemic
ally. Five ductal carcinomas in situ overexpressed ERBB2 and showed pr
eserved E-CD expression. Forty-four of 226 infiltrating ductal carcino
mas (19.47%) showed ERBB2 overexpression, and a statistically signific
ant relationship was found between ERBB2 overexpression and high histo
logical grade. E-CD expression was preserved in 111 cases (49.1%) and
correlated with the histological grade. How ever, no significant relat
ionship was found between ERBB2 and E-CD expression. None of the 16 in
filtrating lobular carcinomas expressed ERBB2 or E-CD. These observati
ons in different histological types of breast carcinoma strongly argue
against a role for ERBB2 as a transcriptional regulator of E-CD expre
ssion in most human breast carcinomas in vivo.