Abstract B29: The elucidation for functional roles of Metadherin in metastatic cascade of pancreatic cancer

Abstract

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers. At present, surgical resection is the only curative treatment for PDAC, but the majority of PDAC patients show early recurrence even after curative resection. There is a possibility of having been distant micrometastasis at early stage of carcinogenesis in PDAC. The control of PDAC metastatic progression leads to improve the prognosis of PDAC patients. Recently, it is reported that a verified mediator of distant metastasis, Metadherin (MTDH), promotes metastasis in experimental models of breast cancer, and its high expression is associated with poor prognosis in a large spectrum of cancer types. Recent evidences imply that the epithelial-mesenchymal transition (EMT) and putative cancer stem cell (CSC) functions orchestrates to play crucial roles in cancer progression. In this study, we aim to investigate the function of MTDH in PDAC progression concomitant with undergoing EMT/MET plasticity or involving putative CSC functions. Experimental methods: We investigated MTDH expression in 7 human and 6 mouse PDAC cell lines and elucidated the roles of MTDH in PDAC progression by in vitro experiments for the loss of function using siMTDH and shMTDH. In immunohistochemical (IHC) staining of MTDH in resected PDAC tissues, we analyzed the correlation between MTDH expression and the clinico-pathological parameters as well as clinical outcome of the 82 PDAC patients. Results: Western blot analyses showed higher MTDH protein expression in metastatic PDAC compared to primary PDAC cell lines. In metastatic cell lines, MTDH expression has a positive correlation with E-cadherin expression. These data suggest that MTDH might be related to mesenchymal-epithelial transition (MET) and play a crucial role in metastatic cascade of PDAC. Conversely, MTDH has a negative correlation with E-cadherin in primary PDAC cell lines. It is implicated that MTDH might play inverse functions in primary site and metastatic site. Next, to examine what is the role of MTDH in the EMT/MET process, we evaluated the expression pattern of EMT markers and MTDH in response to transient TGF-β1 treatment. We found that E-cadherin expression decreases at 8 to 24 hours after treatment (EMT initiation), and then comes back to increase of the expression at 4 days after treatment (MET induction). While MTDH and E-cadherin expression shows an inverse relation during EMT initiation, these two expressions have a positive correlation during MET period (from 7 days after treatment). Additionally, we found EMT induction by TGF-β1 is attenuated by knockdown of MTDH, These results suggest MTDH might contribute to the phenotypic switch of PDAC cells via the EMT/MET process. MTDH knockdown significantly impaired the ability of pancreatosphere formation in PDAC cells and sensitized PDAC cells to gemcitabine. In FACS analyses, we also found that the percentage of CD133-positive cancer stem cell subpopulation was significantly reduced in MTDH knockdown metastatic PDAC cells. In anoikis assay, (this assay evaluate the resistance for apoptosis after losing contact from extracelluar matrix), MTDH knockdown reduced anoikis resistance in PDAC cells. These data indicate that MTDH might foster putative CSC functions in PDAC cells. In IHC staining, high MTDH expression indicated significantly higher incidence of hematogenous metastasis (p=0.02). Furthermore, High expression group showed poorer prognosis of PDAC patients compared to Low expression group in Kaplan Meier analysis (p=0.029). Conclusions: MTDH might promote PDAC metastasis to undergo EMT in primary PDAC and MET in metastatic PDAC along with.putative CSC functions. The regulation of MTDH might develop the new strategy for PDAC treatment, and lead to improve the outcome of patients. Citation Format: Kensuke Suzuki, Shigetsugu Takano, Hideyuki Yoshitomi, Shingo Kagawa, Hiroaki Shimizu, Masayuki Otsuka, Katunori Furukawa, Tukasa Takayashiki, Satoshi Kuboki, Daisuke Suzuki, Nozomu Sakai, Hiroyuki Nojima, Masaru Miyazaki.{Authors}. The elucidation for functional roles of Metadherin in metastatic cascade of pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B29.