Study of the role of microRNAs in treatment response and identification of combined therapeutic strategies based on in vivo preclinical models of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Although immune checkpoint inhibitors (ICIs) have revolutionized HCC treatment, molecularly targeted agents, like sorafenib and lenvatinib, remain first-line options for advanced HCC. Their limiting factors are the early development of drug resistance and the lack of biomarkers of treatment response. Several studies emphasize the central role of microRNAs in modulating HCC progression, metabolic reprogramming, and drug response. Sorafenib and lenvatinib resistance mechanisms are not clearly understood but miR-22, a tumor suppressor miRNA and potential target in several cancers, seems to show an emerging role in sorafenib resistance. My thesis project aims to elucidate the mechanisms of sorafenib and lenvatinib resistance in mouse xenograft and DEN-HCC rat in vivo preclinical models respectively. Lenvatinib resistant (LR) Huh-7 cell lines were used to investigate the mechanisms involved in lenvatinib resistance. Firstly, I reported miR-22 role in modulating tumor progression, hypoxia pathway and sorafenib resistance, through GLUT1 targeting, in both in vivo models. I also demonstrated that miR-22 regulates angiogenesis in both in vitro (HUVEC cells) and in vivo (xenograft mice) models. Furthermore, I characterized miR-22 as a potential circulating biomarker of sorafenib response in the DEN-HCC rat model and in a cohort of HCC patients. Omics characterization of lenvatinib treated DEN-HCC rats, showed a deregulation of angiogenesis, EMT, hypoxia and apoptosis pathways in non-responder animals, and metabolic pathways upregulation, such as oxidative metabolism and cholesterol/bile acids biosynthesis. These data were further validated in the in vitro model of LR Huh-7 cells. In summary, the data obtained in this thesis highlights the potential use of miR-22 as a therapeutic target and circulating biomarker of sorafenib response, as well as the suitability of our preclinical tools for the identification lenvatinib resistance mechanisms.