DNA fragments amplified in a stomach cancer-derived cell line, KATO-III, were previously identified by the in-gel DNA renaturation method, and a 0.2-kilobase-pair fragment of the amplified sequence was subsequently cloned. By genomic walking, a portion of the exon of the gene flanking this 0.2-kilobase-pair fragment was cloned, and the gene was designated as K-sam (KATO-III cell-derived stomach cancer amplified gene). The K-sam cDNAs, corresponding to the 3.5-kilobase K-sam mRNA, were cloned from the KATO-III cells. Sequence analysis revealed that this gene coded for 682 amino acid residues that satisfied the characteristics of the receptor tyrosine kinase. The K-sam gene had significant homologies with bek, FLG, and chicken basic fibroblast growth factor receptor gene. The K-sam gene was amplified in KATO-III cells with the major transcript of 3.5-kilobases in size. This gene was also expressed in some other stomach cancer cells, a small cell lung cancer, and germ cell tumors.

Claudins (CLDNs) constitute the major transmembrane proteins of tight junctions. It may be hypothesized that changes in or loss of expression of tight junctional proteins such as CLDNs can lead to cellular disorientation and detachment, which is commonly seen in neoplasia. Recent studies have suggested that claudin-1 (CLDN1) plays an important role in invasion and metastasis and claudin-4 (CLDN4) has a particular role in mammary glandular cell differentiation and carcinogenesis. In this study, we examined 83 breast cancer cases and demonstrated immunohistochemical expression patterns of CLDN1/CLDN4 in recurrent and nonrecurrent groups. We found significant results between the recurrent and non-recurrent group for expression of CLDN1/ CLDN4. The recurrent group (26 cases) showed decreased expression patterns of CLDN1 (p<0.001), compared to the non-recurrent group (57 cases). Decreased expression of CLDN1 (p<0.0001) correlated with short disease-free interval. The lymph node metastasis-positive group showed decreased expression patterns of CLDN1 (p=0.001). However, there was no significance between the recurrent group and non-recurrent group in CLDN4 expression. There was no significance between histological factors and CLDN4 expression. The results indicated that CLDN1 expression correlated with the recurrence status and malignant potential of breast cancer.

Homeobox genes, which are found in all eukaryotic organisms, encode transcriptional regulators involved in cell-type differentiation and development. Several homeobox genes encoding homeodomain proteins that bind and activate the insulin gene promoter have been described. In an attempt to identify additional beta-cell homeodomain proteins, we designed primers based on the sequences of beta-cell homeobox genes cdx3 and lmxl and the Drosophia homeodomain protein Antennapedia and used these primers to amplffy inserts by PCR from an insulinoma cDNA library. The resulting amplification products include sequences encoding 10 distinct homeodomain proteins; 3 of these proteins have not been described previously. In addition, an insert was obtained encoding a splice variant of engrafled-2, a homeodomain protein previously identified in the central nervous system. Northern analysis revealed a distinct pattern of expression for each homeobox gene. Interestingly, the PCR-derived clones do not represent a complete sampling of the beta-cell library because no inserts encoding cdx3 or lmxl protein were obtained. Beta cells probably express additional homeobox genes. The abundance and diversity of homeodomain proteins found in beta cells illustrate the remarkable complexity and redundancy of the machinery controlling beta-cell development and differentiation.RIPE3B element (16) and the P1 element (8) [also called CT1 (9)] lie on either side of the IEB1 element. The A/T elements and the E boxes function synergistically: none of the elements can function in isolation, but combination of an E box and an A/T element results in dramatic activation of transcription (11,16,19). A number of complexes from beta-cell nuclei bind to the A/T elements (6, 8-11, 16, 19 Based on evidence that the A/T-binding proteins cloned so far do not account for all the beta-cell nuclear complexes that bind the A/T elements (H.O. and M.S.G., unpublished data), we assumed that beta cells contained additional homeodomain proteins. We attempted to identify additional beta-cell homeodomain proteins by PCR. We report here the PCR amplification and cDNA cloning of several additional betacell homeodomain proteins. ¶ The beta cells in the pancreatic islets of Langerhans are distinguished by their ability to produce insulin. The cellspecific expression of insulin derives, at least in part, from regulation of the insulin gene promoter by a unique set of nuclear proteins that bind to the promoter and activate it in beta cells. Mapping of transcriptionally active sequences within the insulin promoter has identified several important sequence elements within the rat insulin I (1, 2), rat insulin II (3, 4), and human insulin promoters (5) and has led to the recognition of beta-cell nuclear protein complexes that bind these elements (4-11) (for reviews, see refs. 12 and 13).Many of the critical sequence elements of the insulin promoter fall into two groups: the E box elements and the (A+T)-rich elements. The proximal human and rat insulin I promoters contain two...

hst is a transforming gene first identified from transformed NIH 3T3 cells that were transfected with DNA of a human stomach cancer. A genomic fragment of hst obtained directly from a human genomic library also has transforming activity. This fragment has a coding sequence identical to that of the hst cDNA prepared from an NIH 3T3 transformant induced by DNA from a stomach cancer. The deduced amino acid sequence of the hst protein is 43%, 38%, and 40% homologous, respectively, to human basic fibroblast growth factor, human acidic fibroblast growth factor, and mouse int-2 protein in selected regions. This suggests that hst encodes a protein related to fibroblast growth factors, which are wide-spectrum mitogens, and to the int-2 protein, a potential oncogene product implicated in murine mammary carcinogenesis.

Pancreatic islet beta cells regulate the rate of insulin gene transcription in response to a number of nutrients, the most potent of which is glucose. To test for its regulation by glucose, the promoter sequence was isolated from the human insulin gene. When linked to chloramphenicol acetyltransferase and transfected into primary islet cultures, the human insulin promoter is activated by glucose. In parallel islet transfections, glucose also activates the L-pyruvate kinase and islet amyloid chain ketoacid dehydrogenase E1a promoter, but it does not affect the beta cell glucose kinase promoter. Using deletion and substitution mutations of the proximal human insulin promoter, we mapped a metabolic response element to the E box, E1, at -100 base pairs relative to the transcription start site. Although the isolated E1 element responds to glucose, inclusion of either of two AT-rich sequences, A1 or A2/C1 on either side of E1, results in dramatic synergistic activation. Inclusion of A2/C1 also increases the response to glucose. The A2-E1-A1 region alone, however, does not explain all of the activity of the human insulin promoter in cultured islets, and other transcriptionally important elements likely to contribute to the glucose response as well.