Analysis of tissue- and hormone-specific regulation of the human prolactin-inducible protein/gross cystic disease fluid protein-15 gene in transgenic mice Y Myal 1 , B Iwasiow, H Cosby, A Yarmill, A Blanchard, D Tsuyuki, A Fresnoza, M L Duckworth and R P C Shiu Departments of Pathology 1 and Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada (Requests for offprints should be addressed to Y Myal, Department of Pathology, Faculty of Medicine, University of Manitoba, 770 Bannatyne Ave., Winnipeg, Manitoba, Canada R3E 0W3) ABSTRACT The human prolactin-inducible protein/gross cystic disease fluid protein-15 (PIP/GCDFP-15) gene is expressed in more than 90% of human breast cancer biopsies but not in the normal mammary gland. However, it is expressed in several normal human apocrine glands such as the lacrimal and salivary glands. In human breast cancer cell lines, the gene is regulated by a number of hormones including androgen and prolactin. It is not known whether gene expression in normal tissues is under similar hormonal control. To understand the mechanisms by which hormone- and tissue-specific expression of the human PIP/GCDFP-15 gene are regulated in vivo, we generated transgenic mice using a 13·7 kb genomic DNA fragment containing the entire 7 kb human gene, together with 2·9 kilobases of 5* and 3·8 kilobases of 3* flanking sequences. The human PIP/GCDFP-15 transgene was found to be expressed in both the lacrimal and salivary glands but was not expressed in the mammary glands of transgenic mice. This tissue-specific pattern of the transgene expression in the mouse was very similar to that of the endogenous human PIP/GCDFP- 15 gene, and to the endogenous mouse gene. In the mouse salivary glands, the transgene expression was highest in the parotid, considerably less in the submaxillary (submandibular) and absent in the sublingual glands. In the mouse lacrimal gland, as in the human breast cancer cell lines, the human PIP/GCDFP-15 transgene was also up-regulated by androgen. These studies demonstrate that the human gene with its 6·3 kb flanking sequences is able to confer gene expression in vivo in a tissue-specific and hormone-responsive manner. Journal of Molecular Endocrinology (1998) 21, 217–223 INTRODUCTION The human prolactin-inducible protein/gross cystic disease fluid protein-15 (PIP/GCDFP-15) is a 14 kDa protein first identified in human breast cancer cell lines (Shiu & Iwasiow 1985) and in the fluid from benign gross cystic disease of the human breast (Haagensen & Mazoujian 1986). The PIP/ GCDFP-15 gene expression has been detected in most (293%) human breast tumor biopsies (Clark et al. 1996). PIP/GCDFP-15 has been used as a diagnostic marker for human breast cancer and for breast cancer progression (Mazoujian et al. 1983, 1989). In human breast cancer cell lines, the gene is regulated by a number of hormones including prolactin, estrogen, dexamethasone and cytokines, but is maximally up-regulated by androgen (Murphy et al. 1987, Simard et al. 1989, Blais et al. 1996). PIP/GCDFP-15 has also been detected in normal human tissues, particularly those apocrine in origin such as the Moll’s gland of eyelids and the minor bronchial glands and in the secretions of the lacrimal and salivary glands; however, it is not expressed in the normal mammary gland (Mazoujian et al. 1983, Haagensen & Mazoujian 1986, Murphy et al. 1987, Mazoujian & Margolis 1988). It is not known whether the expression of the human PIP/GCDFP-15 gene in any of these normal tissues is under similar hormonal control as that observed in the human breast cancer cell lines. The single copy human gene has previously been isolated and characterized (Myal et al. 1991). The 217 Journal of Molecular Endocrinology (1998) 21, 217–223 ? 1998 Society for Endocrinology Printed in Great Britain 0952–5041/98/021–217 $08.00/0