LAUSR

It is estimated that more than 90% of the human genome is transcribed into non-coding RNAs (ncRNA). It has been demonstrated that ncRNAs have an important role in biological processes such as proliferation, differentiation, and cell migration. Changes in their expression have been associated with several diseases, including cancer. Melanoma is one of the most aggressive types of cancer, with high probability of metastasis and an unfavorable response to therapies. Our lab has developed an in vitro melanoma progression model, which was established by exposing nontumorigenic melanocytes (melan-a) to sustained stress conditions (cycles of adhesion blockage), sequentially generating different cell lines (i.e., 4C, premalignant melanocytes; 4C11-, non-metastatic melanoma cells; and 4C11+, metastatic melanoma cells), in which each cell line represents a distinct stage of tumor progression. Previous RNA sequencing data comparing these 4 cell lines identified a total of 3404 long non-coding transcripts which displayed differential expression (DE) levels when comparing two or more cell lines. We have clustered 531 of them into three distinct signatures: malignancy, epithelial-to-mesenchymal transition (EMT), or metastasis, according to their expression profiles. We also analyzed the neighboring genes of those lncRNAs, as it is known that lncRNAs might regulate gene expression in cis. We identified the lncRNA Dlx4os, highly expressed in undifferentiated and mesenchymal-like 4C and 4C11- cells, and 6 neighboring genes whose expression correlate to the EMT signature and overall survival in human melanoma patients. Among these genes we found Dlx4, which shares the same promoter site with Dlx4os and whose expression correlates to a poor prognosis. We silenced Dlx4os in the 4C11- cells through interference RNA technology. The downregulation of Dlx4os led to expression changes in EMT-related genes, such as Snail1, Sox10 and Mitf, indicating that it might play a role in EMT. Dlx4os downregulation also inhibited cell migration in vitro and tumorigenesis in vivo. These results overall indicate a role of Dlx4os in melanocyte malignant transformation. Citation Format: Ana Luísa P. Ayub, Hatylas Azevedo, Diogo Pessoa, Leinal Sejour, Ioannis Vlachos, Eduardo M. Reis, Frank J. Slack, Miriam G. Jasiulionis. Dlx4os: a lncRNA associated with malignant melanocyte transformation. [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 3755.