Upregulation of MLK4 promotes migratory and invasive potential of breast cancer cells

Anna A Marusiak,Dawid Mehlich,John Brognard,Dominika Nowis,Monika K Prelowska,Michal Lazniewski,Aleksandra Korwat,Hanna Kedzierska,Klaudia Kaminska,Jakub Golab,Olga Sokolowska,Adam Gorczynski,Wojciech Biernat,Dariusz Plewczynski

doi:10.1038/s41388-018-0618-0

Abstract

Metastasis to distant organs is a major cause for solid cancer mortality, and the acquisition of migratory and invasive phenotype is a key factor in initiation of malignancy. In this study we investigated the contribution of Mixed-Lineage Kinase 4 (MLK4) to aggressive phenotype of breast cancer cells. Our TCGA cancer genomic data analysis revealed that amplification or mRNA upregulation of MLK4 occurred in 23% of invasive breast carcinoma cases. To find the association between MLK4 expression and the specific subtype of breast cancer, we performed a transcriptomic analysis of multiple datasets, which showed that MLK4 is highly expressed in triple-negative breast cancer compared to other molecular subtypes. Depletion of MLK4 in cell lines with high MLK4 expression impaired proliferation and anchorage-dependent colony formation. Moreover, silencing of MLK4 expression significantly reduced the migratory potential and invasiveness of breast cancer cells as well as the number of spheroids formed in 3D cultures. These in vitro findings translate into slower rate of tumor growth in mice upon MLK4 knock-down. Furthermore, we established that MLK4 activates NF-κB signaling and promotes a mesenchymal phenotype in breast cancer cells. Immunohistochemical staining of samples obtained from breast cancer patients revealed a strong positive correlation between high expression of MLK4 and metastatic potential of tumors, which was predominantly observed in TNBC subgroup. Taken together, our results show that high expression of MLK4 promotes migratory and invasive phenotype of breast cancer and may represent a novel target for anticancer treatment.

Highlights

IntroductionBreast cancer is a highly heterogeneous disease classified into several subgroups varying on molecular characterization, treatment responses and clinical outcomes [1]
Supplementary information The online version of this article contains supplementary material, which is available to authorized users.Breast cancer is a highly heterogeneous disease classified into several subgroups varying on molecular characterization, treatment responses and clinical outcomes [1]
We found that Mixed-Lineage Kinase 4 (MLK4) was highly upregulated in the samples of triplenegative breast cancer (TNBC) patients compared to other subtypes (Fig. 1b), and that MLK4 gene amplification and/or mRNA upregulation was present in more than 50% of TNBC samples in analyzed TCGA datasets (Fig. 1c)

Summary

Introduction

Breast cancer is a highly heterogeneous disease classified into several subgroups varying on molecular characterization, treatment responses and clinical outcomes [1]. Histopathological assessments of samples have their limitations and an additional approach, based on the patterns of gene expression, further aids in treatment stratification [2]. Gene expression studies have identified several molecular subtypes of breast cancer including luminal A, luminal B, HER2-enriched, basal-like and normal breast-like [1, 3]. The subgroup which is characterized by the absence of ER/ PR and the lack of HER2 overexpression is called triplenegative breast cancer (TNBC). TNBC represents about 1020% of all breast cancers, and approximately 80% of TNBCs are simultaneously classified as basal-like [4, 5]. TNBC is a heterogeneous subgroup linked with an aggressive phenotype, frequent metastasis and poor prognosis, where no targeted therapies have been developed so far [6,7,8]

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Conclusion