EXPRESSION OF C-ERBB3 PROTEIN IN PRIMARY BREAST CARCINOMAS

Expression of c-erbB3 protein was investigated in 104 primary breast c arcinomas comprising nine comedo ductal carcinoma in situ (DCIS), 91 i nvasive ductal carcinomas and four invasive lobular carcinomas using t wo monoclonal antibodies, RTJ1 and RTJ2. Of the 91 invasive ductal car cinomas, seven contained the comedo DCIS component adjacent to the inv asive component. An immunohistochemical technique was used to evaluate the association between expression of c-erbB3 and clinical parameters and tumour markers such as epidermal growth factor receptor (EGFR), c -erbB2, cathepsin-D and p53 in archival formalin-fixed paraffin-embedd ed tumour tissues. Our results indicated that RTJ1 and RTJ2 gave ident ical staining patterns and concordant results. it was found that the o verexpression of c-erbB3 protein was observed in 67% (6/9) of comedo D CIS, 52% (44/84) of invasive ductal carcinomas, 71% (5/7) of carcinoma s containing both the in situ and invasive lesions and 25% (1/4) of in vasive lobular carcinomas. A significant relationship (P < 0.05) was o bserved between strong immunoreactivity of c-erbB3 protein and histolo gical grade, EGFR and cathepsin-D, but not with expression of c-erbB2, p53, oestrogen receptor status, lymph node metastases or age of patie nt. However, we noted that a high percentage of oestrogen receptor-neg ative tumours (59%), lymph node-positive tumours (63%) and c-erbB2 (63 %) were strongly positive for c-erbB3 protein. We have also documented that a high percentage of EGFR (67%), c-erbB2 (67%), p53 (75%) and ca thepsin-D-positive DCIS (60%) were strongly positive for c-erbB3. Thes e observations suggest that overexpression of c-erbB3 protein could pl ay an important role in tumour progression from non-invasive to invasi ve and, also, that it may have the potential to be used as a marker fo r poor prognosis of breast cancer.