Genes affected by Ret activation during estrogen stimulation or inhibition in MCF7/Aro cells

Endocrine therapy is the main therapeutic option for patients with estrogen receptor alpha positive (ER+) breast cancer. Nevertheless, most of them become estrogen-independent and relapse after the treatment. Ret is a tyrosine kinase receptor that shows elevated expression levels in ER+ human breast tumors. In this study, we demonstrate that activation of the Ret receptor promotes proliferation as well as cell migration irrespective of endocrine therapy. Microarray data show that Ret activation involves changes in the expression of inflammatory- and motility-related genes. In vivo treatment with a Ret pathway inhibitor in a ER+/Ret+ mouse mammary cancer model, reduces tumor growth and lung metastasis even after endocrine therapy. Additionally, we show a connection between Ret and inflammatory pathways. The pro-inflamatory cytokine IL6 lies at the core of this regulation, which involves a positive feedback loop with IL6 and the Ret pathway reciprocally stimulating each other to further leading metastasis risk. Our findings provide insight into endocrine resistance mechanism and point at the Ret pathway as a potential target for future therapies.

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Gattelli A, Nalvarte I, Boulay A, Roloff TC, Schreiber M, Carragher N, Macleod KK, Schlederer M, Lienhard S, Kenner L, Torres-Arzayus MI, Hynes NE