title: Wound healing-like immune program facilitates postpartum mammary gland involution and tumor progression.
abstract: Women diagnosed with breast cancer within 5 years postpartum have poor survival rates. The process of postpartum mammary gland involution, whereby the lactating gland remodels to its prepregnant state, promotes breast cancer progression in xenograft models. Macrophage influx occurs during mammary gland involution, implicating immune modulation in the promotion of postpartum breast cancer. Herein, we characterize the postpartum murine mammary gland and find an orchestrated influx of immune cells similar to that which occurs during wound healing. Further, the normal involuting gland may be in an immunosuppressed state as discerned by the transient presence of Foxp3(+) regulatory T cells and IL-10(+) macrophages with T cell suppressive function. To determine the influence of the postpartum immune microenvironment on mammary tumor promotion, we developed an immune-competent model. In this model, mammary tumors in the involution group are sixfold larger than nulliparous group tumors, have decreased CD4(+) and CD8(+) T cell infiltrates and contain a greater number of macrophages with the ability to inhibit T cell activation. Targeting involution with a neutralizing antibody against the immunosuppressive cytokine IL-10 reduces tumor growth in involution group mice but not in nulliparous mice, implicating the involution microenvironment as the primary target of αIL-10 treatment. Relevance to women is implicated, as we find postlactational human breast tissue has transient high IL-10(+) and Foxp3(+) immune cell infiltrate. These data show an immune modulated microenvironment within the normal involuting mammary gland suggestive of immunosuppression, that when targeted reduces tumor promotion, revealing possible immune-based strategies for postpartum breast cancer.
authors.affiliation: Department of Medicine, Division of Medical Oncology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045; Program in Cancer Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045.
authors.forename: Holly A
authors.initials: HA
authors.lastname: Martinson
authors.forename: Sonali
authors.initials: S
authors.lastname: Jindal
authors.forename: Clarissa
authors.initials: C
authors.lastname: Durand-Rougely
authors.forename: Virginia F
authors.initials: VF
authors.lastname: Borges
authors.forename: Pepper
authors.initials: P
authors.lastname: Schedin
mesh_terms: D000328:Adult; D000818:Animals; D001940:Breast / Q000276:immunology; D001943:Breast Neoplasms / Q000276:immunology / Q000473:pathology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D018450:Disease Progression; D005260:Female; D051858:Forkhead Transcription Factors / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000276:immunology; D008297:Male; D008321:Mammary Glands, Animal / Q000276:immunology* / Q000473:pathology*; D042361:Mammary Glands, Human / Q000276:immunology* / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D049590:Postpartum Period / Q000276:immunology*; D014945:Wound Healing / Q000276:immunology*; D055815:Young Adult
chemical_list: D051858:Forkhead Transcription Factors; D016753:Interleukin-10
keywords: immune modulation; macrophages; myeloid derived suppressor cells; postpartum breast cancer; regulatory T cells