title: Differential in vivo tumorigenicity of distinct subpopulations from a luminal-like breast cancer xenograft.
abstract: Intratumor heterogeneity caused by genetic, phenotypic or functional differences between cancer cell subpopulations is a considerable clinical challenge. Understanding subpopulation dynamics is therefore central for both optimization of existing therapy and for development of new treatment. The aim of this study was to isolate subpopulations from a primary tumor and by comparing molecular characteristics of these subpopulations, find explanations to their differing tumorigenicity. Cell subpopulations from two patient derived in vivo models of primary breast cancer, ER+ and ER-, were identified. EpCAM+ cells from the ER+ model gave rise to tumors independently of stroma cell support. The tumorigenic fraction was further divided based on SSEA-4 and CD24 expression. Both markers were expressed in ER+ breast cancer biopsies. FAC-sorted cells based on EpCAM, SSEA-4 and CD24 expression were subsequently tested for differences in functionality by in vivo tumorigenicity assay. Three out of four subpopulations of cells were tumorigenic and showed variable ability to recapitulate the marker expression of the original tumor. Whole genome expression analysis of the sorted populations disclosed high similarity in the transcriptional profiles between the tumorigenic populations. Comparing the non-tumorigenic vs the tumorigenic populations, 44 transcripts were, however, significantly differentially expressed. A subset of these, 26 identified and named genes, highly expressed in the non-tumorigenic population, predicted longer overall survival (N = 737, p<0.0001) and distant metastasis free survival (DMFS) (N = 1379, p<0.0001) when performing Kaplan-Meier survival analysis using the GOBO online database. The 26 gene set correlated with longer DMFS in multiple breast cancer subgroups. Copy number profiling revealed no aberrations that could explain the observed differences in tumorigenicity. This study emphasizes the functional variability among cell populations that are otherwise genomically similar, and that the risk of breast cancer recurrence can only be eliminated if the tumorigenic abilities in multiple cancer cell subpopulations are inhibited.
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Genetics, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: Nirma
authors.initials: N
authors.lastname: Skrbo
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Oncology, Oslo University Hospital, Oslo, Norway.
authors.forename: Geir-Olav
authors.initials: GO
authors.lastname: Hjortland
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; K.G. Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Alexandr
authors.initials: A
authors.lastname: Kristian
authors.affiliation: Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Ruth
authors.initials: R
authors.lastname: Holm
authors.affiliation: Department of Genetics, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; K.G. Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Silje
authors.initials: S
authors.lastname: Nord
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Lina
authors.initials: L
authors.lastname: Prasmickaite
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Oncology, Oslo University Hospital, Oslo, Norway; Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; K.G. Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Olav
authors.initials: O
authors.lastname: Engebraaten
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Centre, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway; Department of Pharmacy, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway; K.G. Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Gunhild M
authors.initials: GM
authors.lastname: Mælandsmo
authors.affiliation: Department of Genetics, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Centre, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway; K.G. Jebsen Centre for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Therese
authors.initials: T
authors.lastname: Sørlie
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Centre, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Kristin
authors.initials: K
authors.lastname: Andersen
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051927:CD24 Antigen / Q000378:metabolism; D063646:Carcinogenesis; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D016000:Cluster Analysis; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D011960:Receptors, Estrogen / Q000378:metabolism; D055746:Stage-Specific Embryonic Antigens / Q000378:metabolism; D014183:Transplantation, Heterologous
chemical_list: D000951:Antigens, Neoplasm; D051927:CD24 Antigen; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D011960:Receptors, Estrogen; D055746:Stage-Specific Embryonic Antigens; C066584:stage-specific embryonic antigen-4