TrkA expression directs the anti-neoplastic activity of MLK3 inhibitors in triple-negative breast cancer
Rakesh Sathish Nair1, Sandeep Kumar1, Subhasis Das1,2
1Department of Surgery, Division of Surgical Oncology, The University of Illinois at Chicago, Chicago, IL, 60612, USA.
Abstract:
Mixed Lineage Kinase 3 (MLK3) is a viable target for neoplastic diseases; however, it is unclear whether its activators or inhibitors can act as anti-neoplastic agents. We reported that the MLK3 kinase activity was higher in triple-negative (TNBC) than in hormone receptor-positive human breast tumors, where estrogen inhibited MLK3 kinase activity and provided a survival advantage to ER+ breast cancer cells. Herein, we show that in TNBC, the higher MLK3 kinase activity paradoxically promotes cancer cell survival. Knockdown of MLK3 or MLK3 inhibitors, CEP-1347 and URMC-099, attenuated tumorigenesis of TNBC cell line and Patient-Derived (PDX) xenografts. The MLK3 kinase inhibitors decreased both the expression and activation of MLK3, PAK1, and NF-kB protein and caused cell death in TNBC breast xenografts. RNA-seq analysis identified several genes downregulated by MLK3 inhibition, and the NGF/TrkA MAPK pathway was significantly enriched in tumors sensitive to growth inhibition by MLK3 inhibitors. The TNBC cell line unresponsive to kinase inhibitor had substantially lower TrkA, and overexpression of TrkA restored the sensitivity to MLK3 inhibition. These results suggest that the functions of MLK3 in breast cancer cells depend on downstream targets in TNBC tumors expressing TrkA, and MLK3 kinase inhibition may provide a novel targeted therapy.
Insights
Mixed Lineage Kinase 3 (MLK3) higher activity promotes triple-negative breast cancer (TNBC) survival. MLK3 inhibition, via compounds like CEP-1347, reduced TNBC tumor growth and induced cell death, suggesting a new targeted therapy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Mixed Lineage Kinase 3 (MLK3) kinase activity is elevated in triple-negative breast cancer (TNBC) compared to hormone receptor-positive breast tumors.
- Estrogen inhibits MLK3 activity, conferring a survival advantage to estrogen receptor-positive (ER+) breast cancer cells.
- In TNBC, paradoxically, higher MLK3 kinase activity promotes cancer cell survival.
Purpose of the Study:
- To investigate the role of MLK3 kinase activity in TNBC pathogenesis.
- To evaluate the anti-neoplastic potential of MLK3 inhibitors in TNBC models.
- To identify downstream targets and pathways affected by MLK3 inhibition in TNBC.
Main Methods:
- MLK3 knockdown and treatment with MLK3 inhibitors (CEP-1347, URMC-099) in TNBC cell lines and patient-derived xenografts (PDX).
- Assessment of protein expression and activation (MLK3, PAK1, NF-kB) and cell death.
- RNA-sequencing (RNA-seq) analysis to identify gene expression changes.
- Investigation of the NGF/TrkA MAPK pathway and TrkA expression in relation to inhibitor sensitivity.
Main Results:
- MLK3 knockdown and inhibitors attenuated TNBC cell line and PDX xenograft tumorigenesis.
- MLK3 inhibitors decreased MLK3, PAK1, and NF-kB expression/activation, inducing cell death.
- RNA-seq revealed genes downregulated by MLK3 inhibition, with significant enrichment of the NGF/TrkA MAPK pathway in sensitive tumors.
- Low TrkA expression correlated with unresponsiveness to MLK3 inhibitors; TrkA overexpression restored sensitivity.
Conclusions:
- MLK3 functions in TNBC are dependent on downstream targets, particularly TrkA.
- MLK3 kinase inhibition demonstrates potential as a novel targeted therapy for TNBC, especially in tumors expressing TrkA.
