Coordinated activation of c-Src and FOXM1 drives tumor cell proliferation and breast cancer progression
Ipshita Nandi, … , Benita S. Katzenellenbogen, William J. Muller
Ipshita Nandi, … , Benita S. Katzenellenbogen, William J. Muller
Published February 16, 2023
Citation Information: J Clin Invest. 2023;133(7):e162324. https://doi.org/10.1172/JCI162324.
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Research Article Oncology

Coordinated activation of c-Src and FOXM1 drives tumor cell proliferation and breast cancer progression

Abstract

Activation of the tyrosine kinase c-Src promotes breast cancer progression and poor outcomes, yet the underlying mechanisms are incompletely understood. Here, we have shown that deletion of c-Src in a genetically engineered model mimicking the luminal B molecular subtype of breast cancer abrogated the activity of forkhead box M1 (FOXM1), a master transcriptional regulator of the cell cycle. We determined that c-Src phosphorylated FOXM1 on 2 tyrosine residues to stimulate its nuclear localization and target gene expression. These included key regulators of G2/M cell-cycle progression as well as c-Src itself, forming a positive feedback loop that drove proliferation in genetically engineered and patient-derived models of luminal B–like breast cancer. Using genetic approaches and small molecules that destabilize the FOXM1 protein, we found that targeting this mechanism induced G2/M cell-cycle arrest and apoptosis, blocked tumor progression, and impaired metastasis. We identified a positive correlation between FOXM1 and c-Src expression in human breast cancer and show that the expression of FOXM1 target genes predicts poor outcomes and associates with the luminal B subtype, which responds poorly to currently approved therapies. These findings revealed a regulatory network centered on c-Src and FOXM1 that is a targetable vulnerability in aggressive luminal breast cancers.

Authors

Ipshita Nandi, Harvey W. Smith, Virginie Sanguin-Gendreau, Linjia Ji, Alain Pacis, Vasilios Papavasiliou, Dongmei Zuo, Stella Nam, Sherif S. Attalla, Sung Hoon Kim, Sierra Lusson, Hellen Kuasne, Anne-Marie Fortier, Paul Savage, Constanza Martinez Ramirez, Morag Park, John A. Katzenellenbogen, Benita S. Katzenellenbogen, William J. Muller

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Figure 2

c-Src ablation impairs proliferation and increases apoptosis in an organoid model of early mammary tumor progression.

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c-Src ablation impairs proliferation and increases apoptosis in an organ...
(A) Mammary glands from c-Src+/+ and c-SrcL/L MIC mice were immunostained with the indicated antibodies and DAPI. Representative images and quantification of Ki67+ and BrdU+ nuclei, normalized to Cre. n = 10 mice per group (minimum of 10,000 total nuclei per sample). Scale bar: 100 μm. **P < 0.01, by unpaired, 2-tailed Student’s t test. (B) Organotypic cultures were immunostained with the indicated antibodies and DAPI, and the organoid diameter was measured. Scale bar: 10 μm. ***P < 0.001 and ****P < 0.0001, by 1-way ANOVA with Tukey’s post hoc test. (C) Organoids were immunostained with the indicated antibodies (left panel), and staining was quantified and normalized to total nuclei (DAPI) (right panel). Scale bar: 10 μm. n = 3 independent mice per genotype (minimum of 20 total nuclei analyzed per mouse). *P < 0.05 and **P < 0.01, by 1-way ANOVA with Tukey’s post hoc test. (D) Organoids were immunostained to detect cleaved caspase 3 (left panel). Staining was quantified and normalized to the total number of cells, as determined by DAPI staining (right panel). n = 3 independent mice per genotype (minimum of 20 total nuclei analyzed per mouse). Scale bar: 10 μm. ***P < 0.001, by 1-way ANOVA with Tukey’s post hoc test. Dox, doxycycline.