Ets2-Dependent Stromal Regulation of Mouse Mammary Tumors

Abstract

The Ets2 transcription factor is regulated by mitogen-activated protein (MAP) kinase phosphorylation of a single threonine residue. We generated by gene targeting a single codon mutation in Ets2 substituting Ala for the critical Thr-72 phosphorylation site (Ets2 A72 Most cancers are epithelial in origin. However, a significant and sometimes predominate portion of breast, colon, stomach, and pancreas tumors are host fibroblasts, endothelial cells, inflammatory cells, smooth muscle cells, adipocytes, and extracellular matrix known collectively as stroma (6). Much less is known about the molecular genetics of tumor-stroma interaction than is known about epithelial transformation. Tissue stroma can both suppress and promote tumor progression (16,57). Among the examples of stroma-neoplasia communication is the role of matrix metalloproteinases produced by fibroblasts and invasive inflammatory cells in the angiogenic switch associated with pancreatic and skin neoplastic progression (5, 10).)Ets2 is one of over 25 transcription factors in the human genome that utilize the Ets winged helix-loop-helix DNA-binding domain (30, 54). Extracellular signal-regulated kinase 2 (Erk2) binds to Ets2 through a docking site in the evolutionarily conserved, N-terminal pointed domain of a subset of Ets transcription factors (44). The signal transduction pathway from growth factor receptors, such as fibroblast growth factor (FGF) receptor and epidermal growth factor receptor (EGFR; Erbb1), through the Ras-mitogen-activated protein kinase pathway to the pointed domain of Ets transcription factors is used for regulating developmental transitions in Drosophila melanogaster and Caenorhabditis elegans and growth factor signaling in humans and mice. In Drosophila the closest relative of Ets2, the Pointed-P2 product of the pointed gene, is key in Ras-pathway-dependent photoreceptor development (40) and in tracheal ductal morphogenesis (42). In mammals, Ets2 has been implicated in growth factor stimulation of macrophages (7,31,45,49); FGF stimulation (59); and oncogenic stimulation by Neu (23), Ras (60), and Raf (36). The expression of either wild-type Ets2 or a dominant-negative form of Ets2 can reverse the transformed characteristics of human or mouse cancer cell lines (17, 18). Inactivation of Ets2 by a gene-targeted deletion of the DNA-binding domain and nuclear localization signal (Ets2 db1 ) results in embryonic lethality associated with deficient expression of matrix metalloproteinase 9 (MMP-9) and CD31 in trophoblastic derivatives (59). Haploinsufficiency of Ets2 is sufficient to restrict mammary tumors arising from polyomavirus middle T (PyMT) oncogene expression driven by the mouse mammary tumor virus (MMTV) long terminal repeat promoter (38).Here, we show that mutation of Thr-72 creates a hypomorphic allele of Ets2 (Ets2 A72 ), which acts, at least in part, in host stroma to restrict mammary tumors. This tumor restriction is genetically downstream of vascular endothelial growth factor (VEGF) production and is correlated with decrea...

Role of infiltrated leucocytes in tumour growth and spread

“…Similarly, inhibition of MMP9 production in tumour-associated macrophages by a hypomorphic Ets-2 mutation also inhibited tumour development in the PyMT mouse model of breast cancer (Man et al, 2003). These data confirms the involvement of macrophages in tumour development in mouse models.…”

Ets2-dependent microenvironmental support of mouse mammary tumors

“…Targeted deletion of the Ets2 DNA-binding domain (Ets2 db1 ) or mutation of the unique, activating MAPK phosphorylation site (Ets2 A72 ) revealed that Ets2 supports both autochthonous and transplanted mammary tumors (Man et al, 2003). The Ets2-dependent host effect on transplanted tumors showed that at least part of the function of Ets2 was mediated through the stroma (Man et al, 2003).…”

“…Targeted deletion of the Ets2 DNA-binding domain (Ets2 db1 ) or mutation of the unique, activating MAPK phosphorylation site (Ets2 A72 ) revealed that Ets2 supports both autochthonous and transplanted mammary tumors (Man et al, 2003). The Ets2-dependent host effect on transplanted tumors showed that at least part of the function of Ets2 was mediated through the stroma (Man et al, 2003). However, a possible epithelial role for Ets2 is suggested by reversal of the transformed phenotype of BT20 breast tumor cells by a dominantnegative Ets2 construct (Sapi et al, 1998), but such constructs also broadly inhibit Ets family transcription factor function (Hever et al, 2003).…”

Infiltrating neutrophils mediate the initial angiogenic switch in a mouse model of multistage carcinogenesis

“…Tumor-associated macrophages have been reported to express MMP-9 in a number of mouse models of cancer, including squamous carcinomas of the skin (18) and cervix (19) and carcinomas of the breast (20,21). When stained with anti-CD68 (Fig.…”