title: Regulation of COX2 expression in mouse mammary tumor cells controls bone metastasis and PGE2-induction of regulatory T cell migration.
abstract: BACKGROUND
  The targeting of the immune system through immunotherapies to prevent tumor tolerance and immune suppression are at the front lines of breast cancer treatment and research. Human and laboratory studies have attributed breast cancer progression and metastasis to secondary organs such as the bone, to a number of factors, including elevated levels of prostaglandin E2 (PGE2) and the enzyme responsible for its production, cyclooxygenase 2 (COX2). Due to the strong connection of COX2 with immune function, we focused on understanding how variance in COX2 expression manipulates the immune profile in a syngeneic, and immune-competent, mouse model of breast cancer. Though there have been correlative findings linking elevated levels of COX2 and Tregs in other cancer models, we sought to elucidate the mechanisms by which these immuno-suppressive cells are recruited to breast tumor and the means by which they promote tumor tolerance.
  
  
  RESULTS
  To elucidate the mechanisms by which exacerbated COX2 expression potentiates metastasis we genetically manipulated non-metastatic mammary tumor cells (TM40D) to over-express COX2 (TM40D-COX2). Over-expression of COX2 in this mouse breast cancer model resulted in an increase in bone metastasis (an observation that was ablated following suppression of COX2 expression) in addition to an exacerbated Treg recruitment in the primary tumor. Interestingly, other immune-suppressive leukocytes, such as myeloid derived suppressor cells, were not altered in the primary tumor or the circulation. Elevated levels of PGE2 by tumor cells can directly recruit CD4+CD25+ cells through interactions with their EP2 and/or EP4 receptors, an effect that was blocked using anti-PGE2 antibody. Furthermore, increased Treg recruitment to the primary tumor contributed to the greater levels of apoptotic CD8+ T cells in the TM40D-COX2 tumors.
  
  
  CONCLUSIONS
  Due to the systemic effects of COX2 inhibitors, we propose targeting specific EP receptors as therapeutic interventions to breast cancer progression.
authors.affiliation: Department of Molecular Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Karavitis
authors.forename: Laura M
authors.initials: LM
authors.lastname: Hix
authors.forename: Yihui H
authors.initials: YH
authors.lastname: Shi
authors.forename: Rachael F
authors.initials: RF
authors.lastname: Schultz
authors.forename: Khashayarsha
authors.initials: K
authors.lastname: Khazaie
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D001859:Bone Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000556:secondary; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000378:metabolism; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism* / Q000473:pathology
chemical_list: D000906:Antibodies; D052246:Cyclooxygenase 2 Inhibitors; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D015232:Dinoprostone