Serological and immunohistochemical detection of a 65-kDa oncofetal protein in breast cancer

Sera from 132 breast cancer patients and 112 healthy female controls were tested with a double-antibody sandwich ELISA using two different monoclonal antibodies against the 65-kDa oncofetal protein, termed p65. Of cancer sera, 90.2% were positive for p65. The average level of p65 was 466.5 ± 243.8 ng/ml (mean ± S.D.) in carcinomas and 37.4 ± 29.5 ng/ml (mean ± S.D.) in controls ( P < 0.0005). A selected group ( n = 15) of these 132 patients were needle-biopsied and assessed immunohistochemically using monoclonal antibodies against p65. Nucleocytoplasmic expression was found in 12 patients (80%) using monoclonal antibodies. Expressions of p65 were concordant in 13 (86%) cases between serum and tumour tissues, but did not correlate with tumour DNA ploidy, histological grade or hormone receptors levels. Sera were also tested for CA 15-3 with the average value in cancer serum being 132.4 ± 14.0 U/ml; there was no significant concordance between the two markers. Thus, p65 may be a potential serum and/or immunohistochemical marker for breast carcinoma.