Attenuated TGFB signalling in macrophages decreases susceptibility to DMBA-induced mammary cancer in mice

Abstract

Background Transforming growth factor beta1 (TGFB1) is a multi-functional cytokine that regulates mammary gland development and cancer progression through endocrine, paracrine and autocrine mechanisms. TGFB1 also plays roles in tumour development and progression, and its increased expression is associated with an increased breast cancer risk. Macrophages are key target cells for TGFB1 action, also playing crucial roles in tumourigenesis. However, the precise role of TGFB-regulated macrophages in the mammary gland is unclear. This study investigated the effect of attenuated TGFB signalling in macrophages on mammary gland development and mammary cancer susceptibility in mice. Methods A transgenic mouse model was generated, wherein a dominant negative TGFB receptor is activated in macrophages, in turn attenuating the TGFB signalling pathway specifically in the macrophage population. The mammary glands were assessed for morphological changes through wholemount and H&E analysis, and the abundance and phenotype of macrophages were analysed through immunohistochemistry. Another cohort of mice received carcinogen 7,12-dimethylbenz(a)anthracene (DMBA), and tumour development was monitored weekly. Human non-neoplastic breast tissue was also immunohistochemically assessed for latent TGFB1 and macrophage marker CD68. Results Attenuation of TGFB signalling resulted in an increase in the percentage of alveolar epithelium in the mammary gland at dioestrus and an increase in macrophage abundance. The phenotype of macrophages was also altered, with inflammatory macrophage markers iNOS and CCR7 increased by 110% and 40%, respectively. A significant decrease in DMBA-induced mammary tumour incidence and prolonged tumour-free survival in mice with attenuated TGFB signalling were observed. In human non-neoplastic breast tissue, there was a significant inverse relationship between latent TGFB1 protein and CD68-positive macrophages. Conclusions TGFB acts on macrophage populations in the mammary gland to reduce their abundance and dampen the inflammatory phenotype. TGFB signalling in macrophages increases mammary cancer susceptibility potentially through suppression of immune surveillance activities of macrophages.

N‐(benzylidene)‐2‐((2‐hydroxynaphthalen‐1‐yl)diazenyl)benzohydrazides (1‐2) (NCHDH and NTHDH) attenuate DMBA‐induced breast cancer via Nrf2/NF‐κB/apoptosis signaling

“…The animals of all groups during the whole study and death in any group were recorded. The survival analysis was performed in all the treated groups before the DMBA administration to the 20th week following DMBA administration [28,29].…”

Estrogen-induced immune changes within the normal mammary gland

“…Whilst www.nature.com/scientificreports/ an oversimplification, these states can be broadly divided on a spectrum ranging from M1 tumour-inhibiting macrophages to M2 tumour-promoting macrophages 33 . In the mouse mammary gland, M1 macrophages are associated with reduced cancer susceptibility, and reduction in this macrophage subtype due to endogenous TGFβ signaling increases cancer risk 34 . As M2 macrophages and neutrophils can both stimulate angiogenesis, cancer stem cell niche remodelling and cytotoxic T cell inhibition, it is plausible that these changes induced by oophorectomy and endocrine therapy provide the tissue with an improved ability to respond to early tumour growth and transformation.…”

The Combination of Immune Checkpoint Blockade with Tumor Vessel Normalization as a Promising Therapeutic Strategy for Breast Cancer: An Overview of Preclinical and Clinical Studies

“…In BC, TAM polarization is regulated by several TME-derived factors [ 102 ]. For example, upon VEGF binding to VEGFR2 expressed on their membrane, TAMs polarize to an M2-like phenotype [ 103 , 104 ] and secrete angiogenic and immunosuppressive cytokines (e.g., IL-10, TGFβ, and VEGF) that favor tumor progression [ 105 , 106 , 107 ]. Interestingly, macrophages of BC-bearing mice have been found to express both VEGFR1 and VEGFR2, while those from tumor-free mice express only VEGFR1 [ 90 ].…”