Abstract 3799: Regulation of p16-E2F1-CDK4/6 signaling by TRUC-16 ultraconserved long non-coding RNA

Abstract High phylogenetic conservation of genomic loci is a potential marker of essential biological functionality. Ultraconserved elements (UCEs) are DNA sequences entirely conserved through millions of years of evolution, but their functions are not well understood. Several long non-coding RNAs (lncRNAs) are transcribed from UCEs and play active roles in cancer development. Using a combination of in vitro and in vivo experiments with two animal models and 4 patient cohorts, we discovered several remarkable aspects of ultraconservation. Using a multi-step genetically defined carcinogenesis model, we identified one UCE, uc.206, and its associated overexpressed lncRNA TRUC-16 as a regulator of cell proliferation in chronic lymphocytic leukemia (CLL). High levels of TRUC-16 inhibit p16INK4A translation, causing increased proliferation through an E2F1-mediated mechanism in CLL patients, as well as in zebrafish and murine models. uc.206/TRUC-16 function is extremely conserved throughout evolution. We found cell cycle-related effects of TRUC-16 in both mice and zebrafish, in which we observed increased proliferation of blood cells after overexpression of the human TRUC-16. High levels of CDK4/6 consequent to TRUC-16 overexpression and p16 decrease can be specifically targeted in both CLL and Richter’s Transformation (RT), a rare but deadly consequence of CLL. Inhibition of CDK6 is a therapeutic option never tested in CLL, but in use for another type of B cell malignancy, such as the mantle cell lymphoma. Our results highlight the multifaceted contribution of a UCE to human tumorigenesis and open new possibilities for the use of long-noncoding RNAs in cancer therapies. Citation Format: Linda Fabris, Erik Knutsen, Maria Teresa S. Bertilaccio, Steliana Calin, Recep Bayraktar, George T. Eisenhoffer, Leonard Girnita, George A. Calin. Regulation of p16-E2F1-CDK4/6 signaling by TRUC-16 ultraconserved long non-coding RNA. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3799.