Abstract 280: Switching of CD44 and hMena mRNA splice variants between the intramucosal lesion and invasive front of early stage human colorectal carcinoma (pT1), and their relationship to the expression of cancer stem cell markers and clinicopathological features.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background:Epithelial-Mesenchymal Transition (EMT) is a key process involved in both tumor metastasis and cancer stem cell development. Recent studies have indicated that regulation at the level of alternative splicing constitutes a critical mechanism that controls EMT and cancer progression (Warzecha CC et al. Mol Cell 33:591,2009). The aim of this study was to clarify the mRNA expression statuses of CD44 and hMena splice variants and colon cancer stemness markers in pT1 stage colorectal carcinoma (CRC). Materials and methods:The mRNA expression of CD44 and hMena splice variants as well as colorectal cancer stemness markers, such as ALDH1, CD133 and CD26, were analyzed in 58 tumors of early CRC featuring submucosal invasion (pT1). The samples were obtained from endoscopically resected specimens between 2006 and 2010 at the Asahi General Hospital. The mRNAs were extracted from the mucosal lesion and invasive front of each CRC specimen using laser-captured microdissection then analyzed by semi-quantitative real-time PCR. The correlations between expression of these mRNAs and clinicopathological factors were also investigated. This study was approved by institutional review boards. Results:Significantly higher CD44s mRNA levels were predominantly expressed in the samples from invasive fronts when compared with those measured from intramucosal lesion, while CD44v mRNA levels were significantly higher in the samples from intramucosal lesions than of those from invasive fronts (P=0.0004 and 0.001, respectively). The hMena+11a mRNA levels in the mucosal lesions were higher than those measured from the invasive front (p=0.006). The mRNA levels of hMenaINV, in contrast, showed the reversed expression pattern. Thus, cell-type specific expression of epithelial and mesenchmal isoforms of hMena is achieved through tight regulation of mutually exclusive exons hMena+11a and MenaINV, respectively. The mRNA levels of ALDH1, CD133 and CD26 were low and did not differ between samples from the intramucosal area and invasive front. However, ALDH1 transcript levels increased at the area of subserosal invasion of advanced CRCs. Notably, higher expression levels of hMenaINV mRNAs in samples extracted from invasive fronts were associated with tumor budding grade (P=0.008). Discussion:Our study indicates that the expression of CD44s and MenaINV may reflect the EMT better than the cancer stem cell markers during the initial submucosal invasion of CRC. In summary, the expression of CD44 and hMena splice variants could be potentially useful biomarkers for evaluating the malignant potential of CRC. Citation Format: Hiroshi Yoshida, Akihiro Toyoda, Noriyuki Tanaka, Wataru Masuda, Motoo Kitagawa, Yoshio Suzuki, Kenichi Harigaya. Switching of CD44 and hMena mRNA splice variants between the intramucosal lesion and invasive front of early stage human colorectal carcinoma (pT1), and their relationship to the expression of cancer stem cell markers and clinicopathological features. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 280. doi:10.1158/1538-7445.AM2013-280