Estradiol induces BDNF/TrkB signaling in triple-negative breast cancer to promote brain metastases

Abstract

Breast cancer brain metastases (BM) affect younger women disproportionally, including those lacking estrogen receptor (ER), progesterone receptor, and HER2 (known as triple-negative breast cancer; TNBC). Previous studies in preclinical models showed that pre-menopausal levels of estradiol (E2) promote TNBC-BM through incompletely understood mechanisms involving reactive astrocytes. Herein, a novel mechanism involving E2-dependent upregulation of brain-derived neurotrophic factor (BDNF) in astrocytes, and subsequent activation of tumor cell tropomyosin kinase receptor B (TrkB), is identified. E2 increased experimental BM of TNBC 4T1BR5 and E0771 cells by 21 and 3.6 fold, respectively, compared to E2-depleted mice. ERα + reactive astrocytes were found at early and late stages of BM, and E2 upregulated BDNF in ER + reactive astrocytes in vitro and in vivo. TrkB was expressed in TNBC brain-trophic cell lines, BM-patient-derived xenografts, and breast cancer BM. Conditioned media from E2-treated astrocytes (CM-E2) activated TrkB and downstream AKT, ERK, and PLC-γ signaling in TNBC cells, increasing their invasiveness and tumor-initiating capability in vitro. The promotion of BM by E2-activated astrocytes was found to be more complex, involving feedback loops and other receptor tyrosine kinases. In 4T1BR5 cells, there was a positive feedback loop whereby astrocytic BDNF induced cancer cell BDNF translation. Upregulation of cancer cell BDNF was required to promote full invasiveness of 4T1BR5 in response to CM-E2, and was observed in brain metastatic cells in E2-treated mice in vivo. Moreover, the non-competitive BDNF/TrkB inhibitor ANA-12 reduced E2-induced 4T1BR5 BM to levels similar to OVX mice. BDNF also activated EGFR in TrkB + EGFR + TNBC cells, suggesting that E2 action through astrocytes activates redundant pathways promoting BM. These findings have important therapeutic implications, as they provide a rationale to use E2-depletion therapies or TrkB inhibitors to prevent or delay development of BM in younger women.

Activation of brain‐derived neurotrophic factor signaling in the basal forebrain reverses acute sleep deprivation‐induced fear memory impairments

“…We further used ANA‐12, a highly potent and selective TrkB inhibitor to testify this. We found that injection of ANA‐12 abolished the increase in p‐TrkB and p‐PLCγ1 levels induced by sleep deprivation which were consistent with results from recent study (Contreras‐Zárate et al, 2019). Furthermore, ANA‐12 aggravated sleep deprivation‐induced memory impairments (Figure 5).…”

Ameloblastomas Exhibit Stem Cell Potential, Possess Neurotrophic Properties, and Establish Connections with Trigeminal Neurons

“…Both NGF and BDNF have already been shown to promote tumor innervation in other tissues [29,72,74,79]. In addition to promoting cancer innervation, neurotrophin-mediated signaling has been shown to directly drive tumor onset and progression [72,74,[80][81][82]. The neurotrophin receptors TRKA, TRKB, and P75/NGFR are expressed by malignant cells in many tumor types, where they inhibit key tumor suppressor mechanisms [82] or directly promote cancer cell proliferation and invasiveness [71,74,80,81,83].…”

EO771, is it a well‐characterized cell line for mouse mammary cancer model? Limit and uncertainty

“…However, among the 30 publications considering EO771 cells as triple negative or ERα+, only 3 articles analyzed the expression of ERα 6,40,41 . Contreras‐Zárate et al have considered EO771 cells as triple negative and have showed that the proliferation of EO771 cells is independent of the estradiol presence 23 . But in the same time, they showed that estradiol drives the signaling for brain metastasis of EO771 cells 23 .…”

“…Contreras‐Zárate et al have considered EO771 cells as triple negative and have showed that the proliferation of EO771 cells is independent of the estradiol presence 23 . But in the same time, they showed that estradiol drives the signaling for brain metastasis of EO771 cells 23 . Therefore, Hiraga et al have observed that the gene encoding ERα is transcribed in EO771 cells 41 and Gu et al have observed the protein expression of ERα by western blot 40 .…”

“…Indeed, the advantage of having a tumor line from the most used mouse strain, C57BL/6, makes it possible to have a lot of genetically modified models of this strain. Thus, EO771 cell tumor growth can be evaluated i) in KO mice for E2 (estradiol), 23 apolipoprotein E and aromatase, 42 IFN‐γ receptor, 48 natural killer lytic‐associated molecule (NKLAM), 33 MMP13, 49 calcium‐independent phospholipase A2 β, 50 IGFBP‐3, 21,51,52 DUSP1, 53 GDF2, 54 BMP10, 54 and mKIAA1462 55 but also ii) in transgenic models such as mice overexpressing IL‐15, 56 obese, 13,35 NKC KD (exhibiting silenced Ly49 expression in NK cells), 46 GFP‐LC3 (LC3 linked to GFP expressing mice), 57 mice transgenically modified to express the HER2 proto‐oncogene (ERBB2) 58 or FAT‐1 (gene leading to the endogenous formation of ω3‐Polyunsaturated fatty acid from ω6‐Polyunsaturated fatty acid) 44,59 …”