Dataset Information

A TDO2-AhR signaling axis facilitates anoikis resistance and metastasis in triple-negative breast cancer.

ABSTRACT: The ability of a cancer cell to develop resistance to anoikis, a programmed cell death process triggered by substratum detachment, is a critical step in the metastatic cascade. Triple-negative breast cancers (TNBC) exhibit higher rates of metastasis after diagnosis, relative to estrogen-positive breast cancers, but while TNBC cells are relatively more resistant to anoikis, the mechanisms involved are unclear. Through gene expression and metabolomic profiling of TNBC cells in forced suspension culture, we identified a molecular pathway critical for anchorage-independent cell survival. TNBC cells in suspension upregulated multiple genes in the kynurenine pathway of tryptophan catabolism, including the enzyme tryptophan 2,3-dioxygenase (TDO2), in an NF-?B-dependent manner. Kynurenine production mediated by TDO2 in TNBC cells was sufficient to activate aryl hydrocarbon receptor (AhR), an endogenous kynurenine receptor. Notably, pharmacologic inhibition or genetic attenuation of TDO2 or AhR increased cellular sensitivity to anoikis, and also reduced proliferation, migration, and invasion of TNBC cells. In vivo, TDO2 inhibitor-treated TNBC cells inhibited colonization of the lung, suggesting that TDO2 enhanced metastatic capacity. In clinical specimens of TNBC, elevated expression of TDO2 was associated with increased disease grade, estrogen receptor-negative status, and shorter overall survival. Our results define an NF-?B-regulated signaling axis that promotes anoikis resistance, suggest functional connections with inflammatory modulation by the kynurenine pathway, and highlight TDO2 as an attractive target for treatment of this aggressive breast cancer subtype.

SUBMITTER: D'Amato NC

PROVIDER: S-EPMC4631670 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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A TDO2-AhR signaling axis facilitates anoikis resistance and metastasis in triple-negative breast cancer.

D'Amato Nicholas C NC Rogers Thomas J TJ Gordon Michael A MA Greene Lisa I LI Cochrane Dawn R DR Spoelstra Nicole S NS Nemkov Travis G TG D'Alessandro Angelo A Hansen Kirk C KC Richer Jennifer K JK

Cancer research 20150911 21

The ability of a cancer cell to develop resistance to anoikis, a programmed cell death process triggered by substratum detachment, is a critical step in the metastatic cascade. Triple-negative breast cancers (TNBC) exhibit higher rates of metastasis after diagnosis, relative to estrogen-positive breast cancers, but while TNBC cells are relatively more resistant to anoikis, the mechanisms involved are unclear. Through gene expression and metabolomic profiling of TNBC cells in forced suspension cu ...[more]

PMID: 26363006

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Project description:Tumor-initiating cells with reprogramming plasticity and/or de-differentiation attributes have been thought to initiate primary tumor development as well as to regenerate secondary tumors in metastatic organs; however, the molecular mechanisms are not fully understood. We previously found that breast tumor-initiating cell marker, CD44, directs multicellular aggregation and cluster formation of circulating tumor cells (CTCs), which further enhance stemness and survival of such cells, enabling metastatic colonization to the lungs. To further elucidate the molecular network underlying CTC cluster formation, we performed global proteomic profiling and discovered that the tetraspanin protein CD81, which is normally enriched in exosomes (small extracellular vesicles), is a new driver of cancer initiation and metastasis as a facilitator and target of CD44. Loss of CD81 compromises tumorigenicity and mammosphere formation of triple negative breast cancer (TNBC) cells. Assisted by machine learning-based algorithms and mutagenesis approach, we found that CD81 interacts with CD44 on the cellular membrane through their extracellular regions. Notably, genetic knockout of CD44 or CD81 results in loss of both CD81 and CD44 in secreted exosomes, a state which abolishes exosome-induced self-renewal of recipient cells, such as mammosphere formation. In addition, RNA sequencing analysis showed that CD81 knockdown up-regulates expression of a cell differentiation marker, SEMA7a, whose down-regulation partially rescues mammosphere formation inhibition by CD81 depletion. Clinically, CD81 expression was observed in >80% of CTCs and specifically enriched and co-expressed along with CD44 in clustered CTCs of breast cancer patients. Mimicing the phenotypes of CD44 deficiency, loss of CD81 also inhibited tumor cell aggregation and lung metastasis of TNBC in both human and mouse tumor models, supporting the clinical significance of CD81 in association with patient outcomes. Our study highlights a new driving role of CD81 in cancer exosome-induced stemness, clustered CTCs, and metastasis initiation of TNBC, reported for the first time to our knowledge.

Project description:Triple-negative breast cancer (TNBC) is an aggressive subtype with few treatment options for chemo-resistant disease. In both preclinical models and patient circulating tumor cells, androgen receptor (AR) expression is increased in anchorage independent TNBC. The AR inhibitor enzalutamide (Enza) leads to reduced TNBC growth in soft agar, invasion, mammosphere formation in vitro, and reduced tumorigenicity and recurrence when combined with chemotherapy in vivo pre-clinical models. Transforming growth factor β (TGFβ) pathway gene signatures are also increased during TNBC anchorage independent survival both in vitro and in vivo in pre-clinical models and CTC from patients during relapse while on chemotherapy. We hypothesized that a positive loop between AR and TGFβ signaling facilitates TNBC anchorage independent survival (anoikis resistance). We previously published that AR protein levels and transcriptional activity increased during anchorage independent conditions and we now find that that multiple components of the TGFβ pathway, including TGFβ1 and 3, as well as pathway activity, as measured by nuclear localization and transcriptional activity of pSmad3, are enhanced in anchorage independent conditions. Indeed, exogenous TGFβ increased AR protein and TGFβ inhibition decreased AR and TNBC viability, particularly under anchorage independent culture conditions. ChIP-Seq experiments revealed AR binding to genomic regions near the TGFB1 and SMAD3. TGFB3 and AR expression were positively correlated in clinical datasets and high levels of co-expression correspond to significantly worse recurrence-free and overall survival in both ER- and basal-like breast cancer. Finally, combining Enza with a TGFβ inhibitor decreased cell survival more than either drug alone, particularly under anchorage independent conditions, where the effect was more than additive. These findings warrant further investigations into whether combined inhibition of AR and TGFβ pathways might decrease metastatic recurrence rates and mortality from TNBC.

Dataset Information

A TDO2-AhR signaling axis facilitates anoikis resistance and metastasis in triple-negative breast cancer.

Publications

A TDO2-AhR signaling axis facilitates anoikis resistance and metastasis in triple-negative breast cancer.

Similar Datasets

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