A cDNA coding for an enzyme belonging to the family of copper amine oxidases was cloned from a bovine lung cDNA library using a PCR approach. The nucleotide sequence of this cDNA was found to be different from that of the previously published liver cDNA encoding bovine serum amine oxidase, another copper amine oxidase. Analyses using reverse transcription followed by PCR of RNA extracted from different bovine tissues confirmed that the copper amine oxidase gene expressed in bovine liver is closely related to, but different from, the copper amine oxidase gene expressed in bovine lung, kidney, spleen and heart. Northern blotting data showed that the level of copper amine oxidase expression in liver is considerably higher than in the other tissues tested. Southern blotting analyses of bovine chromosomal DNA suggested the existence of at least three copper amine oxidase genes. Two of these genes are apparently expressed in a tissue‐specific manner as outlined above. A fragment of a third copper amine oxidase gene is identified. The exon‐intron organization of the bovine copper amine oxidase genes analyzed is similar to that of the related human diamine oxidase gene, except that no intron in the position equivalent to that of the third intron in the human gene is found. In the third gene, a complete replacement of the third intron of the bovine copper amine oxidase gene (equivalent to the fourth intron of the human gene) has occurred.
Overexpression of thymosin beta-4 has been linked to malignant progression but the localization of this polypeptide within tumors is incompletely known. We therefore examined breast cancers for thymosin beta-4 using immunofluorescence. Reactive cells were identified with monoclonal cell marker antibodies. A very heterogeneous staining pattern for thymosin beta-4 was observed. Thus, while leukocytes and macrophages showed intense reactivity for this polypeptide, cancer cells, and endothelial cells showed a much more variable reactivity. A similar heterogeneous staining was observed also in colorectal carcinomas. The degree of staining of breast cancer cells for thymosin beta-4 correlated neither to histological grade nor to endothelial cell staining. However, there was a tendency toward correlation (P = 0.07) between staining of endothelial cells and histological grade. Treatment of cultured breast cancer cells (SK-BR-3) with 1-4 microg thymosin beta-4/mL significantly increased cell numbers, as determined by MTT-assays. These data reveal an unexpected cellular heterogeneity of thymosin beta-4 expression in breast and colonic carcinomas and suggest that local release of this polypeptide in the tumor microenvironment may modulate tumor behavior.
