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01.12.2018 | Research article | Ausgabe 1/2018 Open Access

Breast Cancer Research 1/2018

Obesity promotes the expansion of metastasis-initiating cells in breast cancer

Zeitschrift:
Breast Cancer Research > Ausgabe 1/2018
Autoren:
Mélanie Bousquenaud, Flavia Fico, Giovanni Solinas, Curzio Rüegg, Albert Santamaria-Martínez
Wichtige Hinweise

Electronic supplementary material

The online version of this article (https://​doi.​org/​10.​1186/​s13058-018-1029-4) contains supplementary material, which is available to authorized users.
Curzio Rüegg and Albert Santamaria-Martínez contributed equally to this work.

Abstract

Background

Obesity is a strong predictor of poor prognosis in breast cancer, especially in postmenopausal women. In particular, tumors in obese patients tend to seed more distant metastases, although the biology behind this observation remains poorly understood.

Methods

To elucidate the effects of the obese microenvironment on metastatic spread, we ovariectomized C57BL/6 J female mice and fed them either a regular diet (RD) or a high-fat diet (HFD) to generate a postmenopausal diet-induced obesity model. We then studied tumor progression to metastasis of Py230 and EO771 grafts. We analyzed and phenotyped the RD and HFD tumors and the surrounding adipose tissue by flow cytometry, qPCR, immunohistochemistry (IHC) and western blot. The influence of the microenvironment on tumor cells was assessed by performing cross-transplantation of RD and HFD tumor cells into other RD and HFD mice. The results were analyzed using the unpaired Student t test when comparing two variables, otherwise we used one-way or two-way analysis of variance. The relationship between two variables was calculated using correlation coefficients.

Results

Our results show that tumors in obese mice grow faster, are also less vascularized, more hypoxic, of higher grade and enriched in CD11b+Ly6G+ neutrophils. Collectively, this favors induction of the epithelial-to-mesenchymal transition and progression to claudin-low breast cancer, a subtype of triple-negative breast cancer that is enriched in cancer stem cells. Interestingly, transplanting HFD-derived tumor cells in RD mice transfers enhanced tumor growth and lung metastasis formation.

Conclusions

These data indicate that a pro-metastatic effect of obesity is acquired by the tumor cells in the primary tumor independently of the microenvironment of the secondary site.

Graphical abstract

Effects of postmenopausal obesity on primary breast cancer tumoursᅟ
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