Abstract
MicroRNA has been suspected to be generally involved in carcinogenesis since their first description. A first study supported this assumption for canine mammary tumors when miRNA expression was compared to normal gland. The present study extends these results by comparing the expression of 16 microRNA (miRNA) and 4 small nucleolar RNA (snoRNA) in tumors of different malignancy, for example, adenomas, nonmetastasizing and metastasizing carcinomas as well as lymph node metastases, with each other and with normal mammary gland. All neoplastic tissues differed in their miR-210 expression levels from normal gland. While metastatic cells differed in their expression of mir-29b, miR-101, mir-125a, miR-143, and miR-145 from primary tumors, the comparison of miRNA expression in primary tumors of different malignancy failed to reveal significant differences except for a significant downregulation of mir-125a in metastasizing carcinomas when compared to adenomas.
Highlights
MicroRNA is an evolutionarily conserved, noncoding, but regulatory RNA species of approximately 22 nucleotides in length
The present study extends these results by comparing the expression of 16 microRNA and 4 small nucleolar RNA in tumors of different malignancy, for example, adenomas, nonmetastasizing and metastasizing carcinomas as well as lymph node metastases, with each other and with normal mammary gland
While metastatic cells differed in their expression of mir-29b, miR-101, mir-125a, miR-143, and miR-145 from primary tumors, the comparison of miRNA expression in primary tumors of different malignancy failed to reveal significant differences except for a significant downregulation of mir-125a in metastasizing carcinomas when compared to adenomas
Summary
MicroRNA (miRNA) is an evolutionarily conserved, noncoding, but regulatory RNA species of approximately 22 nucleotides in length. It plays a crucial role in various physiological and pathological processes by regulating gene expression posttranscriptionally. A deregulation of miRNA is associated with a wide variety of pathologic states including carcinogenesis [4]. MiR-10b has been identified as a tumor suppressor which prevents human breast cancer development and as an oncogene which initiates breast cancer invasion and metastasis [5]. Several miRNA species have been identified to be involved in human breast cancer development including miR-21, miR-145, and miR-210 [6,7,8]. Only a single study is available on miRNA expression in canine mammary tumors
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