Abstract 1728: DCLK1 promotes tumor growth and invasion through Slug-mediated epithelial-mesenchymal transition in pancreatic neuroendocrine tumors

Abstract

Abstract Introduction: Accumulating evidence suggests that Doublecortin-like kinase 1 (DCLK1) is a putative marker for intestinal and pancreatic cancer stem cells. (Nakanishi et al., Nat Genet 2013, Bailey et al., Gastroenterology 2013). Recently, we have reported that DCLK1 was highly and diffusely expressed in human rectal neuroendocrine tumors (NETs) (Ikezono et al., Oncol Lett, 2015). However, the function of DCLK1 has not yet been investigated in detail. Aims: The aims of the present study were to assess expression levels of DCLK1 in pancreatic NET (PNET) tissues and to identify critical functions of this molecule in PNET cells. Methods: Fifteen patients (8 male, 7 female; mean age, 56) with PNETs were enrolled in this study. The tumors were surgically resected between 1997 and 2012 in Kurume University Hospital. Immunohistochemistry (IHC) was employed to assess expression levels of DCLK1. QGP1, a human PNET cell line, was used in this study, and the cells were transfected with dclk1 cDNA to establish the DCLK1-overexpressing (QGP1-DOE) cells. The QGP1-DOE cells were subjected to dclk1 silencing to confirm acquired cellular characteristics by DCLK1 overexpression. Protein and mRNA expression levels were analyzed by Western blot and real-time PCR (ABI PRISM 7700), respectively. Results: In IHC, all of the 15 PNETs clearly and diffusely expressed DCLK1 in the tumor areas. QGP1-DOE cells robustly expressed full length of DCLK1, showing epithelial-mesenchymal transition (EMT)-like appearance. Of note, extremely high expression of the EMT regulator Slug was found in QGP1-DOE cells compared with control cells at both protein and mRNA levels. Expressions of N-cadherin and Vimentin were also upregulated, in concert with those of phospholylated (p-) FAK, Paxillin, and cyclin D1, in the QGP1-DOE cells. These cells increased cellular motility and proliferation. DCLK1 knockdown restored the above-mentioned expression profile of the EMT-associated molecules. Conclusion: We demonstrated robust expression of DCLK1 in human PNET tissues and PNET cells for the first time. Enforced expression of DCLK1 induced EMT via upregulating Slug expression and promoted proliferation and invasion probably through increasing expression levels of cyclin D1, pFAK, and Paxillin. Therefore, it is speculated that inhibition of DCLK1 expression is a novel therapeutic strategy for PNETs. Citation Format: Yu Ikezono, Hironori Koga, Jun Akiba, Mitsuhiko Abe, Fumitaka Wada, Toru Nakamura, Hideki Iwamoto, Atsutaka Masuda, Takahiko Sakaue, Hirohisa Yano, Osamu Tsuruta, takuji Torimura. DCLK1 promotes tumor growth and invasion through Slug-mediated epithelial-mesenchymal transition in pancreatic neuroendocrine tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1728.