DAPK loss in colon cancer tumor buds: implications for migration capacity of disseminating tumor cells.

Jelena Ivanovska,Viktor Hendrik Koelzer,Inti Zlobec,Heather Dawson,William Laqua,Tilman T Rau,Regine Schneider-Stock,Stefan Forster,Abbas Agaimy,Arndt Hartmann,Stephan Söder,Fabian Garreis,Alessandro Lugli,Eva Karamitopoulou

doi:10.18632/oncotarget.4908

Jelena Ivanovska, Viktor Hendrik Koelzer + Show 12 more

Open Access

https://doi.org/10.18632/oncotarget.4908

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Abstract

Defining new therapeutic strategies to overcome therapy resistance due to tumor heterogeneity in colon cancer is challenging. One option is to explore the molecular profile of aggressive disseminating tumor cells. The cytoskeleton-associated Death-associated protein kinase (DAPK) is involved in the cross talk between tumor and immune cells at the invasion front of colorectal cancer. Here dedifferentiated tumor cells histologically defined as tumor budding are associated with a high risk of metastasis and poor prognosis. Analyzing samples from 144 colorectal cancer patients we investigated immunhistochemical DAPK expression in different tumor regions such as center, invasion front, and buds. Functional consequences for tumor aggressiveness were studied in a panel of colon tumor cell lines using different migration, wound healing, and invasion assays. DAPK levels were experimentally modified by siRNA transfection and overexpression as well as inhibitor treatments. We found that DAPK expression was reduced towards the invasion front and was nearly absent in tumor buds. Applying the ECIS system with HCT116 and HCT116 stable lentiviral DAPK knock down cells (HCTshDAPK) we identified an important role for DAPK in decreasing the migratory capacity whereas proliferation was not affected. Furthermore, the migration pattern differed with HCTshDAPK cells showing a cluster-like migration of tumor cell groups. DAPK inhibitor treatment revealed that the migration rate was independent of DAPK's catalytic activity. Modulation of DAPK expression level in SW480 and DLD1 colorectal cancer cells significantly influenced wound closure rate. DAPK seems to be a major player that influences the migratory capability of disseminating tumor cells and possibly affects the dynamic interface between pro- and anti-survival factors at the invasion front of colorectal cancer. This interesting and new finding requires further evaluation.

Highlights

Death-associated protein kinase (DAPK) is a calmodulin regulated and cytoskeleton associated serine/threonine kinase [1]
We found that Deathassociated protein kinase (DAPK) expression was reduced towards the invasion front and was nearly absent in tumor buds
Applying the electric cell substrate impedance sensing (ECIS) system with HCT116 and HCT116 stable lentiviral DAPK knock down cells (HCTshDAPK) we identified an important role for DAPK in decreasing the migratory capacity whereas proliferation was not affected

Summary

Introduction

Death-associated protein kinase (DAPK) is a calmodulin regulated and cytoskeleton associated serine/threonine kinase [1]. It is a large 160 kDa protein composed of several functional domains, including a kinase domain, a CaM regulatory domain, eight consecutive ankyrin repeats, two putative nucleotide binding domains (P-loops), cytoskeletal/ras of complex proteins (ROC) domain and a death domain [2, 3]. Some studies report the importance of the scaffold function of DAPK to trigger and stabilise multi-protein complexes [4, 5]. Besides a major role in cell death mechanisms, DAPK regulates cytoskeleton-associated proteins to suppress directed migration via blocking of cell polarisation [4, 6]. The phosphorylation of myosin light chain at Ser by DAPK in vivo correlates with the weakening of the structural integrity of the cortical actin network necessary for morphological apoptosis-associated changes such as cell rounding, shrinking, and detachment [10,11,12,13]

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