EXPRESSION OF THE RECEPTOR PROTEIN-TYROSINE KINASE MYK-1 HTK IN NORMAL AND MALIGNANT MAMMARY EPITHELIUM/

We have recently reported the molecular characterization of a novel mu rine receptor PTK (myk-1), belonging to the eph-related family, whose expression was differentially regulated during mammary gland developme nt and elevated in invasive mouse mammary tumours. In this communicati on we have investigated the cellular origin of myk-1 expression by in situ hybridisation and RNase protection. Murine antisense myk-1 probe specifically recognised ductal and alveolar epithelium in the resting mouse mammary gland. In normal human breast, the expression of htk, th e human homologue, was also confined to the secretory luminal epitheli al cells. RNase protection analysis of enriched luminal and myoepithel ial cells prepared from human reduction mammoplasty tissue confirmed t he luminal specificity. Elevated expression of htk was found in severa l human breast carcinoma cell lines as well as in primary, high grade, infiltrating, ductal carcinomas of the breast. The specific epithelia l expression of the myk-1/htk receptor PTK suggests a specialised role of this eph-related PTK in the differentiation and/or maintenance of secretory epithelium in the adult. (C) 1996 Academic Press, Inc.