Circulating antibodies against the breast tumor marker GCDFP-15/gp17 in mammary carcinoma patients and in patients carrying benign breast conditions

Sera samples from 111 women, including 73 breast cancer patients and 38 patients with benign diseases of the breast, were examined. These were compared with samples from healthy women or from patients carrying tumors of origin other than breast as controls. This was done to determine whether antibodies against GCDFP-15/gp17, a protein of gross cystic disease fluid also secreted by mammary apocrine tumor cells, could be found. We observed that 2.6% of mammary disease patients affected by benign conditions and 5.5% of patients carrying malignant mammary gland tumors expressed statistically significant amounts of antibodies against GCDFP-15/gp17 (p <0.01). The highest circulating anti-GCDFP-15/gp17 antibody levels occurred in patients with highly malignant ductal or lobular carcinoma of the breast and in patients with dysplasia. No correlation was found between the presence of circulating antibodies and the size of the tumor or the age of the patients. A bimodal correlation with the percent of invaded lymph nodes was observed instead. IgM and IgG isotypes were detected among the circulating anti-GCDFP- 15/gp17 antibodies, suggesting the involvement of a T-cell-mediated immunoresponse. Our findings raise the possibility that the anti-GCDFP- 15/gp17 immune response may be useful as a tool for investigating some aspects of the mechanisms of breast disease progression and that GCDFP- 15/gp17 may be explored as an antigen for anti-tumor vaccination.