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Human and rat cDNAs to Clara CeU 10 kDa protein {CClO) have been previously isolated. Comparison of the amino acid sequences showed that CCIO is homologous to rabbit uteroglobin. Here we present further evidence that human CClO is the human COUnterpartor rabbit uteroglobin. We have isolated the gene and have mapped its genomic Jocalization to chromosome llq11-qter. Sequence anaJysis of the 5' -ßanking region reveals tbat the homology between the human and the rabbit gene starts at the first exon/intron boundary and extends up to -1.4 kb. A second region of0.74 kb from -1.77 to -2.51 kb in the human 5'-flanking gene region is homologous to rabbit sequences that include four progesterone receptor binding sites which have been bnplicated in progesteroDe regulation of rabbit uteroglobin gene expression in endometrium. Sequence alignment ortbis region on the nucleotide Ievel shows that only two weak progesterone receptor binding sites are partially conserved. In addition, close inspection or the human and rabbit promoters reveals that the estrogen responsive element and two recently identifled cis elements of the rabbit promoter located between -177 and -258 bp are also absent in the human uteroglobin promoter. Despite these difterences in the 5'-ßanking regions or the genes, we report that the human uteroglobin mRNA is expressed in a human ceU Hne of endometrial origin indicating that human uteroglobin is expressed in the uterus like its rabbit homologue. Thus, lt appears that human uteroglobin is not onJy a marker for lung Clara ceUs bot also an endometrial differentiation marker. Human uteroglobin cDNA or antibodies to the protein may be used to characterize endometrium derived tumors.

MFE-296 endometrial cancer cells express androgen receptors in vitro. These cells, which are tumorigenic in nude mice, are derived from a moderately differentiated human endometrial adenocarcinoma. They express vimentin and the cytokeratins 7, 8, 18, and 19. Karyotyping revealed near-tetraploidy for most of the cells. No marker chromosomes were observed. DNA analyses confirmed the genetic identity of the cell line and the patient from whom the cell line was derived. Proliferation of MFE-296 cells was inhibited by the progestin R5020 and the androgen dihydrotestosterone (DHT). The inhibition of proliferation by DHT was antagonized by the antiandrogen Casodex, demonstrating the involvement of the androgen receptor. Androgen binding was determined at 22,000 binding sites per cell using a whole-cell assay (KD = 0.05 nM) and 30 fmol/mg protein with the dextran charcoal method; 7 fmol/mg protein of progesterone receptors were found, whereas estrogen receptors were below 5 fmol/mg protein. The androgen receptor was functionally intact, as demonstrated by transfection experiments with a reporter-gene construct, containing an androgen-responsive element. In MFE-296 cells the content of the androgen receptor was up-regulated by its own ligand.

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