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Autocrine CSF1R signaling mediates switching between invasion and proliferation downstream of TGF? in claudin-low breast tumor cells.

ABSTRACT: Patient data suggest that colony-stimulating factor-1 (CSF1) and its receptor (CSF1R) have critical roles during breast cancer progression. We have previously shown that in human breast tumors expressing both CSF1 and CSF1R, invasion in vivo is dependent both on a paracrine interaction with tumor-associated macrophages and an autocrine regulation of CSF1R in the tumor cells themselves. Although the role of the paracrine interaction between tumor cells and macrophages has been extensively studied, very little is known about the mechanism by which the autocrine CSF1R signaling contributes to tumor progression. We show here that breast cancer patients of the claudin-low subtype have significantly increased expression of CSF1R. Using a panel of breast cancer cell lines, we confirm that CSF1R expression is elevated and regulated by TGF? specifically in claudin-low cell lines. Abrogation of autocrine CSF1R signaling in MDA-MB-231 xenografts (a claudin-low cell line) leads to increased tumor size by enhanced proliferation, but significantly reduced invasion, dissemination and metastasis. Indeed, we show that proliferation and invasion are oppositely regulated by CSF1R downstream of TGF? only in claudin-low cell lines. Intravital multiphoton imaging revealed that inhibition of CSF1R in the tumor cells leads to decreased in vivo motility and a more cohesive morphology. We show that, both in vitro and in vivo, CSF1R inhibition results in a reversal of claudin-low marker expression by significant upregulation of luminal keratins and tight-junction proteins such as claudins. Finally, we show that artificial overexpression of claudins in MDA-MB-231 cells is sufficient to tip the cells from an invasive state to a proliferative state. Our results suggest that autocrine CSF1R signaling is essential in maintaining low claudin expression and that it mediates a switch between the proliferative and the invasive state in claudin-low tumor cells downstream of TGF?.

SUBMITTER: Patsialou A

PROVIDER: S-EPMC4317382 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Autocrine CSF1R signaling mediates switching between invasion and proliferation downstream of TGFβ in claudin-low breast tumor cells.

Patsialou A A Wang Y Y Pignatelli J J Chen X X Entenberg D D Oktay M M Condeelis J S JS

Oncogene 20140804 21

Patient data suggest that colony-stimulating factor-1 (CSF1) and its receptor (CSF1R) have critical roles during breast cancer progression. We have previously shown that in human breast tumors expressing both CSF1 and CSF1R, invasion in vivo is dependent both on a paracrine interaction with tumor-associated macrophages and an autocrine regulation of CSF1R in the tumor cells themselves. Although the role of the paracrine interaction between tumor cells and macrophages has been extensively studied ...[more]

PMID: 25088194

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Project description:BackgroundOsteopontin is a secreted phosphoglycoprotein that is expressed by a number of normal cells as well as a variety of tumor cells. With respect to breast cancer, osteopontin has been implicated in regulating tumor cell proliferation and migration/metastasis and may serve as a prognostic indicator. However it remains unclear whether osteopontin has the same impact in all breast cancer subtypes and in particular, osteopontin's effects in claudin-low breast cancer are poorly understood.MethodscDNA microarrays and qRT-PCR were used to evaluate osteopontin expression in mammary tumors from MTB-IGFIR transgenic mice and cell lines derived from these tumors. siRNA was then used to determine the impact of osteopontin knockdown on proliferation, apoptosis and migration in vitro in two murine claudin-low cell lines as well as identify the receptor mediating osteopontin's physiologic effects.ResultsOsteopontin was expressed at high levels in mammary tumors derived from MTB-IGFIR transgenic mice compared to normal mammary tissue. Evaluation of cell lines derived from different mammary tumors revealed that mammary tumor cells with claudin-low characteristic expressed high levels of osteopontin whereas mammary tumor cells with mixed luminal and basal-like features expressed lower levels of osteopontin. Reduction of osteopontin levels using siRNA significantly reduced proliferation and migration while increasing apoptosis in the claudin-low cell lines. Osteopontin's effect appear to be mediated through a receptor containing ITGAV and not through CD44.ConclusionsOur data suggests that mammary tumors with a mixed luminal/basal-like phenotype express high levels of osteopontin however this osteopontin appears to be largely produced by non-tumor cells in the tumor microenvironment. In contrast tumor cells with claudin-low characteristics express high levels of osteopontin and a reduction of osteopontin in these cells impaired proliferation, survival and migration.

Project description:BackgroundMicroRNAs are a class of non-coding RNAs that regulate gene expression through binding to mRNAs and preventing their translation. One family of microRNAs known as the miR-200 family is an important regulator of epithelial identity. The miR-200 family consists of five members expressed in two distinct clusters; the miR-200c/141 cluster and the miR-200b/200a/429 cluster. We have found that murine and human mammary tumor cells with claudin-low characteristics are associated with very low levels of all five miR-200s.MethodsTo determine the impact of miR-200s on claudin-low mammary tumor cells, the miR-200c/141 cluster and the miR-200b/200a/429 cluster were stably re-expressed in murine (RJ423) and human (MDA-MB-231) claudin-low mammary tumor cells. Cell proliferation and migration were assessed using BrdU incorporation and transwell migration across Matrigel coated inserts, respectively. miRNA sequencing and RNA sequencing were performed to explore miRNAs and mRNAs regulated by miR-200 re-expression while Enrichr-based pathway analysis was utilized to identify cellular functions modified by miR-200s.ResultsRe-expression of the miR-200s in murine and human claudin-low mammary tumor cells partially restored an epithelial cell morphology and significantly inhibited proliferation and cell invasion in vitro. miRNA sequencing and mRNA sequencing revealed that re-expression of miR-200s altered the expression of other microRNAs and genes regulated by SUZ12 providing insight into the complexity of miR-200 function. SUZ12 is a member of the polycomb repressor complex 2 that suppresses gene expression through methylating histone H3 at lysine 27. Flow cytometry confirmed that re-expression of miR-200s increased histone H3 methylation at lysine 27.ConclusionsRe-expression of miR-200s in claudin-low mammary tumor cells alters cell morphology and reduces proliferation and invasion, an effect potentially mediated by SUZ12-regulated genes and other microRNAs.

Dataset Information

Autocrine CSF1R signaling mediates switching between invasion and proliferation downstream of TGF? in claudin-low breast tumor cells.

Publications

Autocrine CSF1R signaling mediates switching between invasion and proliferation downstream of TGFβ in claudin-low breast tumor cells.

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