Human EGFR adenoviral particles

The liver has a unique regenerative capacity, but the mechanisms regulating it are not fully understood. The zinc finger protein ZBTB20 is a key transcriptional repressor of the alpha-fetoprotein (AFP) gene in the liver. As a hallmark of liver differentiation, AFP expression is closely associated with hepatocyte proliferation. Here, researchers show that ZBTB20 is a positive regulator of liver replication and is required for efficient liver regeneration. Mice lacking ZBTB20 specifically in hepatocytes exhibited a marked defect in liver regeneration after partial hepatectomy. Furthermore, in the absence of ZBTB20, epithelial growth factor receptor (EGFR) expression in the liver was significantly reduced, greatly attenuating activation of the EGFR signaling pathway in the regenerating liver. In ZBTB20-deficient hepatocytes, adenovirus-mediated overexpression of EGFR could largely restore AKT activation in vitro in response to EGFR ligands, as well as hepatocyte replication in liver regeneration. Furthermore, in ZBTB20-deficient livers, ZBTB20 overexpression could significantly restore hepatic EGFR expression and cell proliferation after hepatectomy. Together, these data suggest that ZBTB20 is a key regulator of EGFR expression and hepatocyte proliferation in mouse liver regeneration and may serve as a potential therapeutic target in the clinical setting of liver regeneration.

Given the important role of EGFR in liver regeneration, researchers reasoned that impaired EGFR activation might at least partially account for the defective hepatocyte proliferation in the absence of ZBTB20. To test this hypothesis, they first infected ZBTB20-deficient primary hepatocytes in vitro with recombinant adenovirus expressing EGFR (Ad-EGFR) or green fluorescent protein (GFP) (Ad-GFP) as a control. EGFR overexpression effectively restored AKT activation by EGF compared with the GFP control. Researchers then further investigated the rescue effect of Ad-EGFR on liver regeneration. Intravenous injection of Ad-EGFR resulted in EGFR overexpression in LZB20KO livers compared with the GFP control (Figure 1a). Two days after adenovirus administration, mice were subjected to PH, and liver regeneration was assessed by hepatocyte proliferation 48 h after PH. EGFR overexpression largely corrected the hepatocyte replication defect in LZB20KO mice, as reflected by the restoration of BrdU incorporation and Ki67 expression in hepatocytes (Figure 1b, c). These data suggest that impaired EGFR expression and activation at least partially explain the defect in liver regeneration in the absence of ZBTB20.

Figure 1. EGFR overexpression restores the impaired hepatocyte proliferation in regenerating liver from Zbtb20-deficient mice. (Zhang H, et al., 2018)