MAP3K1/MAP2K4 mutations drive breast cancer progression by compensating for TP53 loss through inactivation of the
Sike Hu1, Ailing Ji2, Manxue Wang2
1Tianjin Institute of Medical and Pharmaceutical Sciences, DuoLun Road, Tianjin, 300000, China. husike@126.com.
Background:
Cancer progression is driven by somatic mutations, with alterations in driver genes such as tumor suppressors and oncogenes playing critical roles. In breast cancer (BRCA), mutations in MAP3K1 and MAP2K4 are recurrent, especially in estrogen receptor-positive (ER+) subtypes, yet their functional significance and mechanistic contributions remain incompletely understood. This study aims to elucidate the role of MAP3K1/MAP2K4 mutations in BRCA pathogenesis.
Methods:
We performed integrated genomic analyses using data from The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohorts. Functional validation was conducted in breast cancer cell lines (e.g., MCF-7, ZR-75-1) using shRNA-mediated knockdown, overexpression of dominant-negative MKK4 (MKK4DN), and western blotting. In vivo tumor growth and metastasis were assessed using a xenograft mouse model. Proteomic and phosphoproteomic data from Clinical Proteomic Tumor Analysis Consortium (CPTAC) were analyzed to evaluate JNK pathway activity and FOSL1 expression across multiple cancer types.
Results:
MAP3K1 and MAP2K4 were identified as frequently mutated in BRCA, with mutation spectra dominated by loss-of-function alterations. These mutations exhibited mutual exclusivity with TP53 alterations and were enriched in ER + tumors. Mechanistically, MAP3K1/MAP2K4 loss led to reduced JNK2 phosphorylation, impaired p53 activation at Ser15, and subsequent upregulation of FOSL1 (encoding FRA1), promoting tumor proliferation and metastasis. In vivo, MKK4DN (dominant-negative MAP2K4) expression enhanced tumor growth and lung metastasis, accompanied by decreased phospho-JNK/p53 and increased FRA1. Pan-cancer analysis revealed that MAP3K1/MAP2K4 mutations compensate for TP53 loss in regulating FOSL1 expression, particularly in tumors with moderate TP53 mutation rates.
Conclusions:
Our findings establish MAP3K1 and MAP2K4 as key tumor suppressors in BRCA that operate via the JNK2-p53-FOSL1 axis. Their inactivation provides an alternative mechanism for p53 pathway disruption, adhering to the "minimal necessary alteration" principle in cancer signaling. This study highlights the dual regulatory mechanisms controlling FRA1 expression and offers insights into breast cancer heterogeneity, with potential implications for targeted therapy and patient stratification.
Insights
Mutations in MAP3K1 and MAP2K4 act as tumor suppressors in breast cancer (BRCA) by disrupting the JNK2-p53-FOSL1 pathway, promoting tumor growth and metastasis. These findings offer insights into BRCA heterogeneity and potential therapeutic targets.
Area of Science:
- Genomics and Cancer Biology
- Molecular Oncology
- Signal Transduction Pathways
Background:
- Somatic mutations in driver genes like tumor suppressors and oncogenes drive cancer progression.
- Mutations in MAP3K1 and MAP2K4 are recurrent in breast cancer (BRCA), particularly in estrogen receptor-positive (ER+) subtypes.
- The functional significance and mechanistic roles of MAP3K1/MAP2K4 mutations in BRCA pathogenesis are not fully understood.
Purpose of the Study:
- To elucidate the functional significance and mechanistic contributions of MAP3K1 and MAP2K4 mutations in breast cancer (BRCA) pathogenesis.
- To investigate the role of these mutations in the JNK2-p53-FOSL1 signaling axis.
- To explore the implications for breast cancer heterogeneity and potential therapeutic strategies.
Main Methods:
- Integrated genomic analyses of TCGA and METABRIC breast cancer cohorts.
- Functional validation using cell line experiments (shRNA knockdown, dominant-negative MKK4 overexpression, western blotting).
- In vivo assessment of tumor growth and metastasis in xenograft mouse models; analysis of CPTAC proteomic and phosphoproteomic data.
Main Results:
- MAP3K1 and MAP2K4 are frequently mutated in BRCA, with loss-of-function alterations enriched in ER+ tumors and mutually exclusive with TP53 mutations.
- Loss of MAP3K1/MAP2K4 function reduces JNK2 phosphorylation, impairs p53 activation, and upregulates FOSL1 (FRA1), promoting proliferation and metastasis.
- Pan-cancer analysis shows MAP3K1/MAP2K4 mutations can compensate for TP53 loss in regulating FOSL1 expression.
Conclusions:
- MAP3K1 and MAP2K4 function as key tumor suppressors in BRCA through the JNK2-p53-FOSL1 axis.
- Inactivation of MAP3K1/MAP2K4 provides an alternative mechanism for p53 pathway disruption, aligning with the 'minimal necessary alteration' principle.
- These findings illuminate dual regulatory mechanisms of FRA1 expression, contributing to understanding breast cancer heterogeneity and informing targeted therapy development.
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