GTF3C2 Promotes the Proliferation of Hepatocellular Carcinoma Cells through the USP21/MEK2/ERK1/2 Pathway.

BACKGROUND AND AIMS: General transcription factor IIIC subunit 2 (GTF3C2) is one of the polymerase III transcription-related factors. Previous studies have revealed that GTF3C2 is involved in regulating cell proliferation. However, the role of GTF3C2 in hepatocellular carcinoma (HCC) remains unclear. This study aimed to determine its expression, biological function, and mechanism in HCC. METHODS: The expression of GTF3C2 in HCC and non-tumor tissues, along with its clinical significance, was investigated using public databases and clinical samples. Reverse transcription-quantitative polymerase chain reaction and Western blot assays were performed to detect the expression of GTF3C2, ubiquitin specific peptidase 21 (USP21), mitogen-activated protein kinase 2 (MEK2), extracellular signal-regulated kinase 1/2 (ERK1/2), and p-ERK1/2 in cells. A luciferase reporter assay was conducted to explore the regulatory effect of GTF3C2 on USP21 transcription. Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, and colony formation assays were performed to assess HCC cell proliferation. Subcutaneous injection of HCC cells into nude mice was used to evaluate tumor growth in vivo. RESULTS: GTF3C2 expression was upregulated in HCC tissues and was positively correlated with advanced tumor stages and high tumor grades. HCC patients with high GTF3C2 expression had significantly worse survival outcomes. Knockdown of GTF3C2 suppressed the proliferation of Hep3B and HCCLM3 cells, while overexpression of GTF3C2 facilitated the proliferation of SNU449 and Huh7 cells. GTF3C2 promoted USP21 expression by activating its transcription, which subsequently increased the levels of MEK2 and p-ERK1/2 in HCC cells. Overexpression of both USP21 and MEK2 counteracted the GTF3C2 knockdown-induced inactivation of the ERK1/2 pathway. Moreover, GTF3C2 promoted HCC cell proliferation in vitro and tumor growth in vivo by regulating the USP21/MEK2/ERK1/2 pathway. CONCLUSIONS: Upregulation of GTF3C2 is frequently observed in HCC tissues and predicts poor prognosis. GTF3C2 promotes HCC cell proliferation via the USP21/MEK2/ERK1/2 pathway.