Abstract Long noncoding RNAs (lncRNAs) are transcribed RNA molecules that can interact with DNA or RNA, transcription factors, histones and other chromatin modifying proteins, affecting the expression level of a broad spectrum of genes. Because of their tissue-specific expression characteristics, lncRNAs hold strong promise as novel biomarkers and therapeutic targets for diseases. High-density whole-genome microarray analysis in ameloblastomas, an aggressive odontogenic tumor, and in adenomatoid odontogenic tumor (AOT), an indolent one, showed a high frequency of copy number alteration at chromosome band 14q32.33, which encompasses the lncRNA gene KIAA0125. To understand molecular mechanisms associated with their biological behavior and considering the copy-number gains observed at 14q32.33, we aimed to investigate the expression levels of the lncRNA KIAA0125 in ameloblastomas and in AOTs. The University Ethics Committee approved this study and patients signed informed consent. Thirteen frozen samples were included: five solid/multicystic ameloblastomas, four AOT, and four dental follicles. qPCR reactions were performed in triplicates and the relative changes in gene expression were obtained using the 2^-ΔΔCt formula. The reference gene HPRT1 was used for normalization and the human keratinocyte HaCat cell line was used as calibrator. Differences in the relative changes in gene expression between two groups of samples were assessed and the significance level was set at 0.05. All samples expressed more KIAA0125 than the calibrator. The ameloblastoma group showed higher expression levels of KIAA0125 when compared to dental follicles (p=0.042), while there was no difference between the expression in ameloblastomas and AOT (p>0.05). The expression levels of KIAA0125 in AOT were not different from that of the dental follicle. Our findings suggest that lncRNA KIAA0125 is likely involved in ameloblastoma pathobiology. LncRNAs hold strong promise as therapeutic targets, and experimental validation of this lncRNA functions may lead to tailored therapies targeting KIAA0125 in extensive and recurrent ameloblastomas. Citation Format: Silvia F. Sousa, Marina G. Diniz, Josiane A. França, Fabricio A. Vilas-Boas, Fabricio T. Souza, George A. Calin, Ricardo S. Gomez, Carolina C. Gomes. The long noncoding RNA KIAA0125 is aberrantly expressed in ameloblastomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1811.