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01.12.2017 | Research article | Ausgabe 1/2017 Open Access

BMC Cancer 1/2017

Inhibition of Six1 affects tumour invasion and the expression of cancer stem cell markers in pancreatic cancer

BMC Cancer > Ausgabe 1/2017
Tristan Lerbs, Savita Bisht, Sebastian Schölch, Mathieu Pecqueux, Glen Kristiansen, Martin Schneider, Bianca T. Hofmann, Thilo Welsch, Christoph Reissfelder, Nuh N. Rahbari, Johannes Fritzmann, Peter Brossart, Jürgen Weitz, Georg Feldmann, Christoph Kahlert
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Electronic supplementary material

The online version of this article (doi:10.​1186/​s12885-017-3225-5) contains supplementary material, which is available to authorized users.



Epithelial-to-mesenchymal transition (EMT) and cancer stem cells (CSC) contribute to tumour progression and metastasis. Assessment of transcription factors involved in these two mechanisms can help to identify new targets for an oncological therapy. In this study, we focused on the evaluation of the transcription factor Six1 (Sine oculis 1). This protein is involved in embryologic development and its contribution to carcinogenesis has been described in several studies.


Immunohistochemistry against Six1 was performed on a tissue microarray containing specimens of primary pancreatic ductal adenocarcinomas (PDAC) of 139 patients. Nuclear and cytoplasmic expression was evaluated and correlated to histopathological parameters. Expression of Six1 was inhibited transiently by siRNA in Panc1 and BxPc3 cells and stably by shRNA in Panc1 cells. Expression analysis of CDH1 and Vimentin mRNA was performed and cell motility was tested in a migration assay. Panc1 cells transfected with Six1 shRNA or scrambled shRNA were injected subcutaneously into nude mice. Tumour growth was observed for four weeks. Afterwards, tumours were stained against Six1, CD24 and CD44.


Six1 was overexpressed in the cytoplasm and cellular nuclei in malignant tissues (p < 0.0001). No correlation to histopathological parameters could be detected. Six1 down-regulation decreased pancreatic cancer cell motility in vitro. CDH1 and vimentin expression was decreased after inhibition of the expression of Six1. Pancreatic tumours with impaired expression of Six1 showed significantly delayed growth and displayed loss of the CD24+/CD44+ phenotype.


We show that Six1 is overexpressed in human PDAC and that its inhibition results in a decreased tumour progression in vitro and in vivo. Therefore, targeting Six1 might be a novel therapeutic approach in patients with pancreatic cancer.
Additional file 1: Table 1. Six1 expression in the cell nucleus of malignant and benign tissue and its correlation to clinical and histopathological parameters. *Only 135 malignant and 103 benign specimens could be included. **Only 136 malignant specimens could be evaluated. (DOCX 14 kb)
Additional file 2: Fig. S1. Sequence of siRNA against Six1R1. (PPTX 3958 kb)
Additional file 3: Table 2. Six1, CD44, CD24 and tumor volumes in each mice. (DOCX 11 kb)
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