# TG221: An Experimental Model for Liver Cancer Prevention and Treatment Approaches

## TL;DR

The TG221 mouse model helps study liver cancer by mimicking human HCC and testing new treatments like metformin and miRNA-based therapies.

## Contribution

TG221 is a novel transgenic mouse model for studying miRNA-driven liver cancer and testing RNA-based therapies.

## Key findings

- Metformin prevents tumor formation and suppresses key signaling pathways in early fibrosis.
- miR-199a-3p replacement reduces tumor burden and improves liver integrity.
- A miR-199a-3p-responsive oncolytic virus replicates selectively in tumors with low toxicity.

## Abstract

Hepatocellular carcinoma (HCC) is a leading cause of cancer mortality. It usually arises in cirrhotic liver, where chronic inflammation and fibrosis create a tumor-permissive microenvironment. Dysregulation of microRNAs (miRNAs), particularly upregulation of the oncomiR miR-221 and loss of the tumor suppressor miR-199a-3p represent key drivers of liver carcinogenesis. The TG221 transgenic mouse, designed to overexpress miR-221 in hepatocytes, provides a relevant in vivo platform for mechanistic studies and for testing preventive and therapeutic approaches. The TG221 model recapitulates miR-221-driven tumorigenesis, including suppression of p27, p57 and Bmf. It is characterized by steatohepatitic injury and accelerated tumor formation after genotoxic challenge. In the cirrhotic CCl4-induced background, TG221 mice develop fibrosis and cirrhosis followed by dysplastic and malignant lesions, mirroring the natural history of human HCC. Metformin administered during early fibrosis prevented macroscopic tumor formation and suppressed PI3K/AKT/mTOR signaling. Anti-miR-221 and miR-199a-3p mimics reduced tumor burden, restored tumor-suppressive pathways and improved liver integrity, thus indicating feasible chemopreventive strategies. From a therapeutic point of view, miR-199a-3p replacement synergized with palbociclib and overcame sorafenib resistance. A miR-199a-3p-responsive oncolytic adenovirus achieved tumor-selective replication with minimal toxicity. This review highlights the importance of the TG221 transgenic mouse as a powerful model for studying miRNA-driven hepatocarcinogenesis and enables preclinical evaluation of RNA-based chemopreventive and therapeutic approaches. Metformin, miRNA inhibition, miRNA replacement and miRNA-guided viral therapies emerge as promising approaches for advancing precision prevention and treatment strategies in HCC.