Expression of Transcribed Ultraconserved Regions (T-UCRs) is often deregulated in cancer. The present study assesses the expression and methylation of three T-UCRs (Uc160, Uc283 and Uc346) in colorectal cancer (CRC) and explores the potential of T-UCR methylation in circulating DNA for the detection of adenomas and adenocarcinomas.Expression levels of Uc160, Uc283 and Uc346 were lower in neoplastic tissues from 64 CRC patients (statistically significant for Uc160, p<0.001), compared to non-malignant tissues, while methylation levels displayed the inverse pattern (p<0.001, p=0.001 and p=0.004 respectively). In colon cancer cell lines, overexpression of Uc160 and Uc346 led to increased proliferation and migration rates. Methylation levels of Uc160 in plasma of 50 CRC, 59 adenoma patients, 40 healthy subjects and 12 patients with colon inflammation or diverticulosis predicted the presence of CRC with 35% sensitivity and 89% specificity (p=0.016), while methylation levels of the combination of all three T-UCRs resulted in 45% sensitivity and 74.3% specificity (p=0.013). In conclusion, studied T-UCRs’ expression and methylation status are deregulated in CRC while Uc160 and Uc346 appear to have a complicated role in CRC progression. Moreover their methylation status appears a promising non-invasive screening test for CRC, provided that the sensitivity of the assay is improved.

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e15130 Background: Expression of Transcribed Ultra Conserved Regions (T-UCRs) is often deregulated in cancer. We investigated the role of three T-UCRs (Uc160, Uc283 and Uc346) in colorectal adenocarcinomas and their prognostic and diagnostic value. Methods: Expression and methylation levels of the T-UCRs were assessed in neoplastic and paired non-malignant fresh frozen (FF) tissue specimens from 64 colorectal cancer (CRC) patients, as well as in 6 FF adenoma tissue specimens. In addition, T-UCR methylation levels were assessed in FFPE tumor tissues from 80 CRC patients and in plasma from 161 patients (50 CRC, 59 adenoma patients, 40 healthy subjects and 12 patients with colon inflammation or diverticulosis). Results: Expression levels of all three T-UCRs were lower in neoplastic, compared to non-malignant tissues, although at a statistically significant level only for Uc160 ( p< 0.001). Also, methylation levels of Uc160, Uc283 and Uc346 were higher in tumors compared to non-malignant tissues ( p< 0.001, p= 0.001 and p= 0.004 respectively). Tissue methylation levels of Uc160 were associated with TTP ( p= 0.017). The combination of Uc283 and Uc346 methylation levels was related to OS, however without reaching statistical significance ( p= 0.066). Methylation status of Uc160 and Uc346 in plasma differed significantly among the four patient groups with CRC patients exhibiting the higher levels. Moreover, a strong correlation was found between Uc160 plasma methylation levels and adenoma or adenocarcinoma size and lymph node infiltration ( p< 0.001 and p= 0.024 respectively). When methylation status was used to predict if a subject has CRC, sensitivity and specificity were 35% and 89% respectively, while the values changed to 45% and 74.3% respectively when we combined the sum of the three T-UCR plasma methylation levels. For adenomas, the combination of Uc160 and Uc346 plasma methylation displayed 30.2% (sensitivity) and 80.7% (specificity). Conclusions: T-UCR expression and methylation is deregulated in CRC while their methylation has prognostic value and appears a promising non-invasive screening test for CRC and adenomas, provided that the sensitivity of the assay is improved.