Abstract 6702: Characterization of the microRNA landscape during airway epithelial differentiation and the key role of the miR-34c-5p-FOSL1 regulatory axis in the transformation to squamous metaplasia

MicroRNAs (miRNA) regulate many cellular functions, including proliferation, differentiation, immune regulation, and apoptosis. Dysregulation of miRNAs plays a key causal role in carcinogenesis across a wide variety of cancers. The miRNA family miR-34/449 has been shown to be important for airway epithelial multiciliogenesis and is down-regulated in asthma. Yet, much remains to be learned about the role of miRNAs in airway epithelial development and differentiation. Moreover, specific causal roles of these miRNAs in the development and progression of airway disease states, such as COPD and squamous cell cancer, is largely unknown. In this study, we characterized the expression of miRNAs and their target mRNA during airway epithelial differentiation. We utilized primary human bronchial epithelial cells grown on an air-liquid interface coupled with mRNA and miRNA sequencing at multiple timepoints to robustly characterize the miRNA-mRNA expression landscape of the airway epithelium throughout differentiation. We identified dynamic changes in expression of many miRNAs and their mRNA targets, including several members of the miR-34/449 family. Within this family, we observed highly induced expression of the family member miR-34c-5p throughout differentiation, while its target FOSL1 - a transcription factor - demonstrated decreased expression throughout differentiation. Furthermore, we demonstrated that inhibition of miR-34c-5p resulted in not only increased expression of FOSL1, but also induced the transition to a squamous metaplasia phenotype. Finally, we showed that in human COPD airway tissue samples, miR-34c-5p is significantly downregulated and FOSL1 is significantly upregulated compared to healthy airway, demonstrating the key role the miR-34c-5p-FOSL1 regulatory axis plays in the transition to squamous metaplasia. This study builds a strong foundation and offers promising future directions for the role of miRNAs in both normal airway epithelial differentiation as well as their role in disease. The discovery of the miR-34c-5p-FOSL1 regulatory axis in the transformation to squamous metaplasia uncovers a key molecular regulator of this preneoplastic state. Further, given the increasing understanding of the role of FOSL1 in carcinogenesis as well as its well-established high expression across many different types of cancers, the tight regulation of FOSL1 by miR-34c-5p uncovers a promising avenue for both further understanding the molecular drivers of carcinogenesis as well as potential therapeutic targets. Citation Format: Dalton Hill, Phillip Clapp, Ying Du, Scott Randell, Neil Hayes. Characterization of the microRNA landscape during airway epithelial differentiation and the key role of the miR-34c-5p-FOSL1 regulatory axis in the transformation to squamous metaplasia [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 6702.