title: Variable transcriptional activity of endogenous retroviruses in human breast cancer.
abstract: Human endogenous retroviruses (HERVs) account for up to 9% of the human genome and include more than 800 elements related to betaretroviruses. While mouse mammary tumor virus (MMTV) is the accepted etiological agent of mammary tumors in mice, the role of retroviral elements in human breast cancer remains elusive. Here, we performed a comprehensive microarray-based analysis of overall retroviral transcriptional activities in 46 mammary gland tissue specimens representing pairs of nonmalignant and tumor samples from 23 patients. An analysis of nonmalignant tissue samples revealed a distinct, mammary gland-specific HERV expression profile that consists of 18 constitutively active HERV taxa. For corresponding tumor samples, a general trend toward lower levels of HERV transcription was observed, suggesting common regulatory mechanisms. In various subsets of patients, however, increased transcript levels of single class I HERV families (HERV-T, HERV-E, and HERV-F) and several class II families, including HML-6, were detected. An analysis of transcribed HML-6 sequences revealed either the activation of some or the increased activity of several proviral loci. No evidence for MMTV or human MMTV-like virus transcripts was found, indicating that transcriptionally active, MMTV analogous, exogenous viruses were not present in the breast cancer samples analyzed.
authors: III Medizinische Universitätsklinik, Medizinische Fakultät Mannheim der Universität Heidelberg, Wiesbadener Strasse 7-11, D-68305 Mannheim, Germany. oliver.frank@med3.ma.uni-heidelberg.de
authors: Oliver
authors: O
authors: Frank
authors: Caroline
authors: C
authors: Verbeke
authors: Norbert
authors: N
authors: Schwarz
authors: Jens
authors: J
authors: Mayer
authors: Alice
authors: A
authors: Fabarius
authors: Rüdiger
authors: R
authors: Hehlmann
authors: Christine
authors: C
authors: Leib-Mösch
authors: Wolfgang
authors: W
authors: Seifarth
mesh_terms: D001483:Base Sequence; D030121:Betaretrovirus / Q000235:genetics; D001943:Breast Neoplasms / Q000821:virology*; D020077:Endogenous Retroviruses / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic