Background: Long non-coding RNAs (lncRNAs) have been shown to have functional roles in cancer biology and are dys-regulated in many tumors. Colon Cancer Associated Transcript-1 (CCAT1) is a lncRNA, previously shown to be significantly up-regulated in colon cancer. The aim of this study is to determine expression levels of CCAT1 in gastric carcinoma (GC).

Methods: Tissue samples were obtained from patients undergoing resection for gastric carcinoma (n= 19). For each patient, tumor tissue and normal appearing gastric mucosa were taken. Normal gastric tissues obtained from morbidly obese patients, undergoing laparoscopic sleeve gastrectomy served as normal controls (n= 19). A human gastric carcinoma cell line (AGS) served as positive control. RNA was extracted from all tissue samples and CCAT1 expression was analyzed using quantitative real time-PCR (qRT-PCR).

Results: Low expression of CCAT1 was identified in normal gastric mucosa samples obtained from morbidly obese patients [mean Relative Quantity (RQ)= 1.95±0.4]. AGS human gastric carcinoma cell line showed an elevated level of CCAT1 expression (RQ= 8.02). Expression levels of CCAT1 were approximately 10.8 fold higher in GC samples than in samples taken from the negative control group (RQ= 21.1±5 vs. RQ= 1.95±0.4, respectively, p< 0.001). Interestingly, CCAT1 expression was significantly overexpressed in adjacent normal tissues when compared to the negative control group (RQ= 15.25±2 vs. RQ= 1.95±0.4, respectively, p< 0.001). Tissues obtained from recurrent GC cases showed the highest expression levels (RQ= 88.8±31; p< 0.001). Expression levels increased with tumor stage (T4-36.4±15, T3-16.1±6, T2-4.7±1), however this did not reach statistical significance (p= 0.2). There was no difference in CCAT1 expression between intestinal and diffuse type GC (RQ= 22.4±7 vs. 22.4±16, respectively, p= 0.9). Within the normal gastric tissue samples, no significant difference in CCAT1 expression was observed in helicobacter pylori negative and positive patients (RQ= 2.4±0.9 vs. 0.93±0.2, respectively, p= 0.13).

Conclusion: CCAT1 is up-regulated in gastric cancer, and may serve as a potential bio-marker for early detection and surveillance.