title: Molecular profiling and characterization of luminal-like and basal-like in vivo breast cancer xenograft models.
abstract: The number of relevant and well-characterized cell lines and xenograft models for studying human breast cancer are few, and may represent a limitation for this field of research. With the aim of developing new breast cancer model systems for in vivo studies of hormone dependent and independent tumor growth, progression and invasion, and for in vivo experimental therapy studies, we collected primary mammary tumor specimens from patients, and implanted them in immunodeficient mice. Primary tumor tissue from 29 patients with breast cancer was implanted subcutaneously with matrigel in SCID mice, in the presence of continuous release of estradiol. The tumors were transferred into new animals when reaching a diameter of 15mm and engrafted tumors were harvested for morphological and molecular characterization from passage six. Further, gene expression profiling was performed using Agilent Human Whole Genome Oligo Microarrays, as well as DNA copy number analysis using Agilent Human Genome CGH 244K Microarrays. Of the 30 primary tumors implanted into mice (including two implants from the same patient), two gave rise to viable tumors beyond passage ten. One showed high expression levels of estrogen receptor-alpha protein (ER) while the other was negative. Histopathological evaluation of xenograft tumors was carried out at passage 10-12; both xenografts maintained the morphological characteristics of the original tumors (classified as invasive grade III ductal carcinomas). The genomic profile of the ER-positive xenograft tumor resembled the profile of the primary tumor, while the profile obtained from the ER-negative parental tumor was different from the xenograft. However, the ER-negative parental tumor and xenograft clustered on the same branch using unsupervised hierarchical clustering analysis on RNA microarray expression data of "intrinsic genes". A significant variation was observed in the expression of extracellular matrix (ECM)-related genes, which were found downregulated in the engrafted tumors compared to the primary tumor. By IHC and qRT-PCR we found that the downregulation of stroma-related genes was compensated by the overexpression of such molecules by the mouse host tissue. The two established breast cancer xenograft models showed different histopathological characteristics and profound diversity in gene expression patterns that in part can be associated to their ER status and here described as basal-like and luminal-like phenotype, respectively. These two new breast cancer xenografts represent useful preclinical tools for developing and testing of new therapies and improving our knowledge on breast cancer biology.
authors.affiliation: Department of Genetics, Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0310 Oslo, Norway.
authors.forename: Anna
authors.initials: A
authors.lastname: Bergamaschi
authors.forename: Geir Olav
authors.initials: GO
authors.lastname: Hjortland
authors.forename: Tiziana
authors.initials: T
authors.lastname: Triulzi
authors.forename: Therese
authors.initials: T
authors.lastname: Sørlie
authors.forename: Hilde
authors.initials: H
authors.lastname: Johnsen
authors.forename: Anne Hansen
authors.initials: AH
authors.lastname: Ree
authors.forename: Hege Giercksky
authors.initials: HG
authors.lastname: Russnes
authors.forename: Sigurd
authors.initials: S
authors.lastname: Tronnes
authors.forename: Gunhild M
authors.initials: GM
authors.lastname: Maelandsmo
authors.forename: Oystein
authors.initials: O
authors.lastname: Fodstad
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Borresen-Dale
authors.forename: Olav
authors.initials: O
authors.lastname: Engebraaten
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology*; D004195:Disease Models, Animal; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology; D005260:Female; D020869:Gene Expression Profiling; D015894:Genome, Human; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D020411:Oligonucleotide Array Sequence Analysis; D015203:Reproducibility of Results; D014183:Transplantation, Heterologous; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D016159:Tumor Suppressor Protein p53