Folliculin impairs breast tumor growth by repressing TFE3-dependent induction of the Warburg effect and angiogenesis
Leeanna El-Houjeiri, … , Peter M. Siegel, Arnim Pause
Leeanna El-Houjeiri, … , Peter M. Siegel, Arnim Pause
Published November 15, 2021
Citation Information: J Clin Invest. 2021;131(22):e144871. https://doi.org/10.1172/JCI144871.
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Research Article Angiogenesis Metabolism

Folliculin impairs breast tumor growth by repressing TFE3-dependent induction of the Warburg effect and angiogenesis

Abstract

Growing tumors exist in metabolically compromised environments that require activation of multiple pathways to scavenge nutrients to support accelerated rates of growth. The folliculin (FLCN) tumor suppressor complex (FLCN, FNIP1, FNIP2) is implicated in the regulation of energy homeostasis via 2 metabolic master kinases: AMPK and mTORC1. Loss-of-function mutations of the FLCN tumor suppressor complex have only been reported in renal tumors in patients with the rare Birt-Hogg-Dube syndrome. Here, we revealed that FLCN, FNIP1, and FNIP2 are downregulated in many human cancers, including poor-prognosis invasive basal-like breast carcinomas where AMPK and TFE3 targets are activated compared with the luminal, less aggressive subtypes. FLCN loss in luminal breast cancer promoted tumor growth through TFE3 activation and subsequent induction of several pathways, including autophagy, lysosomal biogenesis, aerobic glycolysis, and angiogenesis. Strikingly, induction of aerobic glycolysis and angiogenesis in FLCN-deficient cells was dictated by the activation of the PGC-1α/HIF-1α pathway, which we showed to be TFE3 dependent, directly linking TFE3 to Warburg metabolic reprogramming and angiogenesis. Conversely, FLCN overexpression in invasive basal-like breast cancer models attenuated TFE3 nuclear localization, TFE3-dependent transcriptional activity, and tumor growth. These findings support a general role of a deregulated FLCN/TFE3 tumor suppressor pathway in human cancers.

Authors

Leeanna El-Houjeiri, Marco Biondini, Mathieu Paquette, Helen Kuasne, Alain Pacis, Morag Park, Peter M. Siegel, Arnim Pause

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Figure 7

Loss of FLCN in luminal breast cancer cells activates a HIF-1α–dependent angiogenic program in a TFE3-dependent manner.

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Loss of FLCN in luminal breast cancer cells activates a HIF-1α–dependent...
(A–C) Heatmaps representing the differential TFE3 (A), PGC-1α (B), and HIF-1α (C) target gene expression in WT and FLCN-knockout (FLCNKO) MCF7 tumors following RNA-sequencing analysis. Each column represents gene expression from a different mouse from each cohort, where blue indicates WT and red indicates FLCNKO tumors. Fold increase was normalized against EV and color coded (dark red indicates 3-fold or more increase, light green indicates 3-fold or more decrease, black indicates no change). (D) Fold change in HIF-1α transcriptional activity, as determined by HIF-1α luciferase promoter activity normalized to CMV-Renilla, in EV and FLCNKO MCF7 cells transfected with nontargeting (NT) control siRNA or siRNA targeting TFE3. Data represent the average ± SEM of n = 7 independent experiments. Statistical significance was determined using 2-way ANOVA with Bonferroni’s multiple-comparison correction. ***P < 0.001. (E) Relative mean fluorescence intensity of the total cellular reactive oxygen species (ROS) in EV and FLCNKO MCF7 cells transfected with NT control siRNA or siRNA targeting TFE3, as measured by flow cytometry. Data represent the average ± SEM of at least n = 3 independent experiments, each performed in triplicate. Significance was determined using Student’s t test. ***P < 0.001. (F–H) Relative TFE3, PGC-1α, and HIF-1α downstream target gene mRNA levels measured by RT-qPCR in EV and FLCNKO MCF7 cells transfected with NT control siRNA or siRNA targeting TFE3 (F), PGC-1α (G), or HIF-1α (H). Data represent the average ± SEM of at least n = 3 independent experiments, each performed in triplicate. Statistical significance was determined using 2-way ANOVA with Bonferroni’s multiple-comparison correction. ***P < 0.001; ****P < 0.0001. NS, not significant.