Abstract 567: Tumor suppressor merlin and WWOX involve in regulating tumor cell growth via epithelial mesenchymal transition (EMT)

Abstract

Abstract Cancer radiotherapy may complicated by chemo/radiation-induced resistance. Gene expression profiling studies have revealed that the tumor carries mesenchymal signature is a poor prognostic predictor. Our laboratory had generated post-irradiated 1306-MG glioblastoma (GBM) cell line which expresses epithelial mesenchymal transition (EMT) markers such as vimentin, fibronectin, desmin, and carbonic anhydrase III. Nuclear translocation of vimentin also occurs in these cells. These findings all indicate EMT. EMT requires cells transition and detachment which is mainly driven by a hyperactive Raf/MAPK pathway via transforming growth factor β (TGF-β) signaling. TGF-β signaling interacts with cell surface Hyal-2 and recruits WWOX. We treated 1306-MG with hyaluronan (HA) and co-transfected with wild type, active form, and inactive form merlin plus WWOX. By fluorescence resonance energy transfer (FRET) and co-immuoprecipitation (CO-IP) assays, our data showed that WWOX interacted with merlin in GBM cell line after treated with hyaluronan (HA). This finding suggest that WWOX participates in the regulation of CD44/merlin signaling. The growth of 1306-MG in merln or WWOX transfected cells showed more cells in S/G2M phases than co-tranfected cells. The co-tranfected WWOX with wild type or active form merlin induced growth arrest in cell cycle were greater than single-tranfected merlin or WWOX. However, inactive form merlin and WWOX co-tranfection caused a growth permissive state was identified by flow cytometry analysis. Using soft agarose colony survival assay, we determined that colony number in co-transfected cells with WWOX plus wild type and active form merlin were more doubled than cells transfected with inactive form merlin plus WWOX. On the contrary, co-transfected cells with wild type and active form merlin plus WWOX, colony size was smaller than co-transfected with inactive form merlin plus WWOX. Given the presence of EMT marker proteins in post-irradiated GBM cell lines, we hypothesize that merlin interacts with WWOX may interfere TGF-β signal pathway and EMT. Analysis data from 1306-MG cells after 12 Gy irradiation and transfected WWOX plus individual types of merlin, we found EMT makers such as vimentin and fibronectin were also significantly increased, especially in cells co-transfected with WWOX and inactive form merlin. Data obtained from cells treated with TβRI/II inhibitor suggested that these changes were TGF-β-dependant. According to these results, we conclude that TGF-β signaling recruits merlin/WWOX and via its interaction to promote cell growth and EMT in post-irradiated GBM cell line in vitro. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 567. doi:10.1158/1538-7445.AM2011-567