Main author: Ramile Dilshat
Institution or Company: Department of Biochemistry and Molecular biology, Faculty of Medicine, University of Iceland
Co-Authors, Institution or Company:
Ramile Dilshat, University of Iceland. Joline Dammeier, Department of Biochemistry and Molecular biology, Faculty of Medicine, University of Iceland. Eirikur Steingrimsson, Department of Biochemistry and Molecular biology, Faculty of Medicine, University of Iceland.
Introduction: Melanoma represents the deadliest form of skin cancer and originates from melanocytes. The aggressiveness of melanoma cells has been partly linked to the transcriptional state of cells with low MITF activity (MITFlow state). Such cells are characterized by the abundant expression of extracellular matrix (ECM) and focal adhesion genes. Recently, we have shown that MITF is a direct repressor of many ECM and focal adhesion genes but may also do this indirectly through other factors.
Methods: CRISPR-Cas9, RNA-seq.
Results: We have shown that SETDB2, a histone methyltransferase which places a repressive histone mark is a direct target of MITF. SETDB2 is highly expressed in melanoma tumours and its expression showed a strong correlation with MITF in the Cancer Genome Atlas. To map the transcriptional signature upon SETDB2 loss, we generated SETDB2-KO cells using CRISPR-Cas9, then performed RNA-sequencing and compared the effect to those observed with MITF-KO cells. Analysis of RNA-seq data revealed that like MITF, SETDB2 represses the expression of ECM and focal adhesion genes. Immunostaining for the focal adhesion marker PXN revealed that SETDB2-KO cells have increased numbers of focal points compared to the control cells. They also have increased expression of N-Cadherin, suggesting a switch into a resistant cell state.
Conclusions: Since increased numbers of focal adhesions and expression of N-Cadherin are observed in MITF KO lines, this suggests that these effects of MITF are partly mediated through SETDB2. Together, our study might unravel an epigenetic mechanism that can be therapeutically exploited to overcome melanoma drug resistance.
