title: Transformation of enriched mammary cell populations with polyomavirus middle T antigen influences tumor subtype and metastatic potential.
abstract: BACKGROUND
  Breast cancer exhibits significant molecular, histological, and pathological diversity. Factors that impact this heterogeneity are poorly understood; however, transformation of distinct normal cell populations of the breast may generate different tumor phenotypes. Our previous study demonstrated that the polyomavirus middle T antigen (PyMT) oncogene can establish diverse tumor subtypes when broadly expressed within mouse mammary epithelial cells. In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.
  
  
  METHODS
  Isolated mouse mammary epithelial cells were transduced with a lentivirus encoding PyMT during an overnight infection and then sorted into hormone receptor-positive luminal (CD133+), hormone receptor-negative luminal (CD133-), basal, and stem cell populations using the cell surface markers CD24, CD49f, and CD133. Each population was subsequently transplanted into syngeneic cleared mouse mammary fat pads to generate tumors. Tumors were classified by histology, estrogen receptor status, molecular subtype, and metastatic potential to investigate whether transformation of different enriched populations affects tumor phenotype.
  
  
  RESULTS
  Although enriched mammary epithelial cell populations showed no difference in either the ability to form tumors or tumor latency, differences in prevalence of solid adenocarcinomas and squamous, papillary, and sebaceous-like tumors were observed. In particular, squamous metaplasia was observed more frequently in tumors derived from basal and stem cells than in luminal cells. Interestingly, both molecularly basal and luminal tumors developed from luminal CD133+, basal, and stem cell populations; however, luminal CD133- cells gave rise exclusively to molecularly basal tumors. Tumors arising from the luminal CD133-, basal, and stem cell populations were highly metastatic; however, luminal CD133+ cells generated tumors that were significantly less metastatic, possibly due to an inability of these tumor cells to escape the primary tumor site.
  
  
  CONCLUSIONS
  Expression of PyMT within different mammary cell populations influences tumor histology, molecular subtype, and metastatic potential. The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.
authors.affiliation: Department of Oncological Sciences, University of Utah, 315 South 1400 East, Salt Lake City, UT, 84112, USA. daria.drobysheva@hci.utah.edu.
authors.forename: Daria
authors.initials: D
authors.lastname: Drobysheva
authors.affiliation: Department of Oncological Sciences, University of Utah, 315 South 1400 East, Salt Lake City, UT, 84112, USA. brittni.smith@hci.utah.edu.
authors.forename: Brittni Alise
authors.initials: BA
authors.lastname: Smith
authors.affiliation: Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, OK, 73104, USA. maria-mcdowell@omrf.org.
authors.forename: Maria
authors.initials: M
authors.lastname: McDowell
authors.affiliation: Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, OK, 73104, USA. katrin-guillen@omrf.org.
authors.forename: Katrin P
authors.initials: KP
authors.lastname: Guillen
authors.affiliation: Department of Oncological Sciences, University of Utah, 315 South 1400 East, Salt Lake City, UT, 84112, USA. atakan.ekiz@hci.utah.edu.
authors.forename: Huseyin Atakan
authors.initials: HA
authors.lastname: Ekiz
authors.affiliation: Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, OK, 73104, USA. bryan.welm@hci.utah.edu.|Current address: Department of Surgery, Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope Drive, Salt Lake City, UT, 84112, USA. bryan.welm@hci.utah.edu.
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Welm
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000821:virology; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D008175:Lung Neoplasms / Q000556:secondary / Q000821:virology*; D008321:Mammary Glands, Animal / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000473:pathology / Q000821:virology*; D051379:Mice; D009368:Neoplasm Transplantation; D018295:Neoplasms, Basal Cell / Q000556:secondary / Q000821:virology*; D010455:Peptides / Q000378:metabolism; D011120:Polyomavirus / Q000235:genetics
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000952:Antigens, Polyomavirus Transforming; D006023:Glycoproteins; D010455:Peptides; C000606024:Prom1 protein, mouse