Abstract 3292: Unraveling molecular mechanisms underlying the awakening of dormant melanomas

Abstract Tumor recurrence, which can occur many years after therapeutic intervention, represents the main challenge in clinical oncology. Clinically, this period between the “cure” of the primary tumor and its local or distal metastatic relapse is known as the “dormancy state.” Tumor dormancy has been linked to therapeutic resistance and a high metastatic potential of malignant neoplasms. During tumor immunoediting, the immune response shapes the tumor to adapt and thrive within an immunocompetent host. Epigenetic modulation is an important way by which cells can quickly regulate gene expression and respond to environmental pressures. Another way of rapid modulation can be through regulatory RNAs, such as lncRNAs which can interact at the level of transcription and translation of other molecules, such as protein-coding genes, and regulate gene expression. To better understand the molecular basis of this tumor dormancy and awakening, we established a murine immune-mediated model of awakening of dormant melanoma cells. In this model, a large number of apoptotic cells are used to generate an acute inflammation process in C57BL/6 mice that promotes a permissive environment for a sub-tumorigenic dose of viable metastatic melanoma cells grown into a fully formed tumor, that would not be formed otherwise. Our study shows that the sub-tumorigenic dose of viable cells only generates tumors in immunosuppressed (NSG) mice (100% of animals), indicating that in immunocompetent animals, the primary defense system - T and B lymphocytes, and NK cells - appears to contain it. Considering the role of epigenetic modulation in rapid cell response to the pressure of the environment, we also show that treatment with the global demethylating agent 5-aza-2’-deoxycytidine causes delay and reduction of tumor mainly through immune activation. This suggests the need for future investigations regarding the epigenetic machinery in our model. Thereby, genome-wide DNA methylome analysis was conducted (EPICarray), and differential gene expression (RNA-seq) analysis of tumors from animals treated (or not) with the demethylating agent. Differentially expressed genes are being selected for further in vitro and in vivo studies. To elucidate this model, we are carrying on assays to understand the role of acute inflammation in the awakening of melanoma dormancy by analyzing the inflammatory profile of the defense system using flow cytometry meanwhile we are conducting other in vivo experiments to better characterize our model. Now, we investigated lncRNAs that are differentially expressed in tumors of animals treated with that drug aiming for new potential biomarkers, or regulators of important immune-response protein-coding genes. All in vivo data were statistically validated using the Student's t-test. We aim to discover potential therapeutic targets with a functional role in the immune-mediated progression of melanoma. Supported by CNPq, CAPES, FAPESP Citation Format: Ianca R. Dias, Débora K. Alves-Fernandes, Lih Hongtao, Frank J. Slack, Gangning Liang, Miriam G. Jasiulionis. Unraveling molecular mechanisms underlying the awakening of dormant melanomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3292.