BMPR2 loss in fibroblasts promotes mammary carcinoma metastasis via increased inflammation

Abstract

Bone Morphogenetic Protein (BMP) receptors mediate a diverse range of signals to regulate both development and disease. BMP activity has been linked to both tumor promoting and suppressive functions in both tumor cells and their surrounding microenvironment. We sought to investigate the requirement for BMPR2 in stromal fibroblasts during mammary tumor formation and metastasis. We utilized FSP1 (Fibroblast Specific Protein-1) promoter driven Cre to genetically delete BMPR2 in mice expressing the MMTV.PyVmT mammary carcinoma oncogene. We found that abrogation of stromal BMPR2 expression via FSP1 driven Cre resulted in increased tumor metastasis. Additionally, similar to epithelial BMPR2 abrogation, stromal loss of BMPR2 results in increased inflammatory cell infiltration. We proceeded to isolate and establish fibroblast cell lines without BMPR2 and found a cell autonomous increase in inflammatory cytokine secretion. Fibroblasts were co-implanted with syngeneic tumor cells and resulted in accelerated tumor growth and increased metastasis when fibroblasts lacked BMPR2. We observed that the loss of BMPR2 results in increased chemokine expression, which facilitates inflammation by a sustained increase in myeloid cells. The chemokines increased in BMPR2 deleted cells correlated with poor outcome in human breast cancer patients. We conclude that BMPR2 has tumor suppressive functions in the stroma by regulating inflammation.

PI3K Inhibition Reduces Mammary Tumor Growth and Facilitates Antitumor Immunity and Anti-PD1 Responses

“…MMTV-PyMT mammary tumor cells (C57/Bl/6 genetic background and FVBn background) were established from spontaneous tumors arising in mice [32]. 4T1 cells (BALB/c genetic background) were obtained from the ATCC.…”

SHARPIN regulates collagen architecture and ductal outgrowth in the developing mouse mammary gland

“…To evaluate further the role of stromal SHARPIN in the regulation of mammary ductal outgrowth, a conditional Sharpin knockout in stromal cells was generated using the S100 Calcium Binding Protein A4 (S100a4), commonly known as the fibroblast-specific protein-1 (FSp1), promoter for Cre expression. The S100a4 promoter has also previously been used for conditional knockout and selective gene expression in the mammary gland stroma (Cheng et al, 2005;Trimboli et al, 2009;O'Connell et al, 2011;Pickup et al, 2015;Koledova et al, 2016). S100a4 expression was detected in lysates of isolated wt and Sharpin cpdm mammary gland fibroblasts by Western blotting ( Fig EV4A) and by IHC labelling of the mammary gland stroma ( Fig EV4C).…”

“…The S100a4 promoter has also previously been used for conditional knockout and selective gene expression in the mammary gland stroma (Cheng et al, 2005;Trimboli et al, 2009;O'Connell et al, 2011;Pickup et al, 2015;Koledova et al, 2016). The S100a4 promoter has also previously been used for conditional knockout and selective gene expression in the mammary gland stroma (Cheng et al, 2005;Trimboli et al, 2009;O'Connell et al, 2011;Pickup et al, 2015;Koledova et al, 2016).…”

Bone Morphogenetic Proteins

“…As discussed, BMP-9/ALK-1 signals promote tumor angiogenesis to alter the tumor microenvironment favorable for cancer growth. Pickup and colleagues investigated the requirement for BMPRII in stromal fibroblasts during the formation and metastasis of mammary carcinoma (Pickup et al 2015). Genetic ablation of stromal BMPR2 expression using fibroblast-specific protein 1 (FSP1) promoter-driven Cre resulted in increased tumor metastasis in a transgenic mouse model of mammary carcinoma.…”