Transcription factor AP-2α activates RNA polymerase III-directed transcription and tumor cell proliferation by controlling expression of c-MYC and p53

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.

miR-1293 suppresses osteosarcoma progression by modulating drug sensitivity in response to cisplatin treatment

Chemotherapy is considered the primary treatment for osteosarcoma. however, its effectiveness is limited due to drug resistance and toxicity. Thus, identifying novel therapeutic targets to enhance the efficacy of chemotherapy is urgently needed. Here, we identified a novel cisplatin-sensitivity enhancing mechanism via up-regulation of the tumour suppressor gene, miR-1293. Meanwhile, higher levels of miR-1293 observed in prechemotherapy patients were associated with a more favorable prognosis. The mechanism underlying cisplatin upregulated miR-1293 expression involves hypomethylation of the miR-1293 promoter, which blocks the binding of the transcription repressor TFAP2A to the promoter. Furthermore, miR-1293 inhibits osteosarcoma progression by targeting TIMP1 to inactivate the Notch1/Hes1 and TGFBR1/Smad2/3 pathways, thereby promoting tumour cell death. The findings presented herein unveil a novel mechanism for enhancing cisplatin sensitivity and proposed a potential therapeutic strategy for osteosarcoma through pre-chemotherapy supplementation of miR-1293.

Crucial role of the transcription factors family activator protein 2 in cancer: current clue and views

The transcription factor family activator protein 2 (TFAP2) is vital for regulating both embryonic and oncogenic development. The TFAP2 family consists of five DNA-binding proteins, including TFAP2A, TFAP2B, TFAP2C, TFAP2D and TFAP2E. The importance of TFAP2 in tumor biology is becoming more widely recognized. While TFAP2D is not well studied, here, we mainly focus on the other four TFAP2 members. As a transcription factor, TFAP2 regulates the downstream targets directly by binding to their regulatory region. In addition, the regulation of downstream targets by epigenetic modification, posttranslational regulation, and interaction with noncoding RNA have also been identified. According to the pathways in which the downstream targets are involved in, the regulatory effects of TFAP2 on tumorigenesis are generally summarized as follows: stemness and EMT, interaction between TFAP2 and tumor microenvironment, cell cycle and DNA damage repair, ER- and ERBB2-related signaling pathway, ferroptosis and therapeutic response. Moreover, the factors that affect TFAP2 expression in oncogenesis are also summarized. Here, we review and discuss the most recent studies on TFAP2 and its effects on carcinogenesis and regulatory mechanisms.