title: TOX3 is expressed in mammary ER(+) epithelial cells and regulates ER target genes in luminal breast cancer.
abstract: BACKGROUND
  A breast cancer susceptibility locus has been mapped to the gene encoding TOX3. Little is known regarding the expression pattern or biological role of TOX3 in breast cancer or in the mammary gland. Here we analyzed TOX3 expression in murine and human mammary glands and in molecular subtypes of breast cancer, and assessed its ability to alter the biology of breast cancer cells.
  
  
  METHODS
  We used a cell sorting strategy, followed by quantitative real-time PCR, to study TOX3 gene expression in the mouse mammary gland. To study the expression of this nuclear protein in human mammary glands and breast tumors, we generated a rabbit monoclonal antibody specific for human TOX3. In vitro studies were performed on MCF7, BT474 and MDA-MB-231 cell lines to study the effects of TOX3 modulation on gene expression in the context of breast cancer cells.
  
  
  RESULTS
  We found TOX3 expression in estrogen receptor-positive mammary epithelial cells, including progenitor cells. A subset of breast tumors also highly expresses TOX3, with poor outcome associated with high expression of TOX3 in luminal B breast cancers. We also demonstrate the ability of TOX3 to alter gene expression in MCF7 luminal breast cancer cells, including cancer relevant genes TFF1 and CXCR4. Knockdown of TOX3 in a luminal B breast cancer cell line that highly expresses TOX3 is associated with slower growth. Surprisingly, TOX3 is also shown to regulate TFF1 in an estrogen-independent and tamoxifen-insensitive manner.
  
  
  CONCLUSIONS
  These results demonstrate that high expression of this protein likely plays a crucial role in breast cancer progression. This is in sharp contrast to previous studies that indicated breast cancer susceptibility is associated with lower expression of TOX3. Together, these results suggest two different roles for TOX3, one in the initiation of breast cancer, potentially related to expression of TOX3 in mammary epithelial cell progenitors, and another role for this nuclear protein in the progression of cancer. In addition, these results can begin to shed light on the reported association of TOX3 expression and breast cancer metastasis to the bone, and point to TOX3 as a novel regulator of estrogen receptor-mediated gene expression.
authors: Research Division of Immunology, Departments of Biomedical Sciences and Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis 5089, Los Angeles, 90048, CA, USA. Akop.Seksenyan@my.rosalindfranklin.edu.
authors: Akop
authors: A
authors: Seksenyan
authors: Research Division of Immunology, Departments of Biomedical Sciences and Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis 5089, Los Angeles, 90048, CA, USA. Kadavallorea@csmc.edu.
authors: Asha
authors: A
authors: Kadavallore
authors: Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA. Ann.Walts@cshs.org.
authors: Ann E
authors: AE
authors: Walts
authors: Research Division of Immunology, Departments of Biomedical Sciences and Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis 5089, Los Angeles, 90048, CA, USA. Delatorreb@csmc.edu.
authors: Brian
authors: B
authors: de la Torre
authors: Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA. berel@usc.edu.|Center for Applied Molecular Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA, USA. berel@usc.edu.
authors: Dror
authors: D
authors: Berel
authors: Genomics Core Facility, Cedars-Sinai Medical Center, Los Angeles, CA, USA. SStrom@mednet.ucla.edu.|Department of Pathology and Laboratory Medicine, University of California Los Angeles David Geffen School of Medicine, Los Angeles, CA, USA. SStrom@mednet.ucla.edu.
authors: Samuel P
authors: SP
authors: Strom
authors: Research Division of Immunology, Departments of Biomedical Sciences and Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis 5089, Los Angeles, 90048, CA, USA. Aliahmadp@csmc.edu.
authors: Parinaz
authors: P
authors: Aliahmad
authors: Genomics Core Facility, Cedars-Sinai Medical Center, Los Angeles, CA, USA. FunariV@cshs.org.
authors: Vincent A
authors: VA
authors: Funari
authors: Research Division of Immunology, Departments of Biomedical Sciences and Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis 5089, Los Angeles, 90048, CA, USA. kayej@csmc.edu.|Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA. kayej@csmc.edu.|Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA. kayej@csmc.edu.
authors: Jonathan
authors: J
authors: Kaye
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006609:High Mobility Group Proteins; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008024:Ligands; D042361:Mammary Glands, Human / Q000378:metabolism / Q000473:pathology; D051379:Mice; D011379:Prognosis; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators
chemical_list: D051017:Apoptosis Regulatory Proteins; D006609:High Mobility Group Proteins; D008024:Ligands; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C521752:TOX3 protein, human; D015534:Trans-Activators; D007334:Insulin-Like Growth Factor I
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