Characterization of ductal and lobular breast carcinomas using novel prolactin receptor isoform specific antibodies

Rabbits were immunized with synthetic peptides of isoform unique regions and immune sera affinity purified prior to validation by Western blot and immunohistochemical analyses. Sections of ductal and lobular carcinomas were stained with each affinity purified isoform specific antibody to determine expression patterns in breast cancer subclasses.We show that the rabbit antibodies have high titer and could specifically recognize each isoform of PRLR. Differences in PRLR isoform expression levels were observed and quantified using histosections from xenografts of established human breast cancer cells lines, and ductal and lobular carcinoma human biopsy specimens. In addition, these results were verified by real-time PCR with isoform specific primers. While nearly all tumors contained LF and SF1b, the majority (76%) of ductal carcinoma biopsies expressed SF1a while the majority of lobular carcinomas lacked SF1a staining (72%) and 27% had only low levels of expression.Differences in the receptor isoform expression profiles may be critical to understanding the role of PRL in mammary tumorigenesis. Since these antibodies are specifically directed against each PRLR isoform, they are valuable tools for the evaluation of breast cancer PRLR content and have potential clinical importance in treatment of this disease by providing new reagents to study the protein expression of the human PRLR.The role of prolactin (PRL) in human breast cancer is now becoming more clearly defined. Recent epidemiologic evidence clearly shows that in both pre- and post-menopausal women with serum prolactin levels in the highest quartile have a significant increased risk of developing breast cancer [1,2]. PRL, acting through is receptors, has definitively been shown to increase cell proliferation and decrease apoptosis in breast cancer cells in culture [3,4]. Additionally, PRL is a pro-angiogenesis factor both in normal and cancerous mammary tissue [5,6]. We [7] and others [8] have shown the existenc