XPD could suppress growth of HepG2.2.15 and down-regulate the expression of hepatitis B virus x protein through P53 pathway

Xeroderma Pigmentosum group D suppresses proliferation and promotes apoptosis of HepG2 cells by downregulating ERG expression via the PPARγ pathway

Xeroderma Pigmentosum group D (XPD) gene has been shown to suppress hepatocellular carcinoma (HCC) progression, but its mechanism remains not fully understood. ETS-related gene (ERG) is generally known as an oncogenic gene. This study aimed to explore whether XPD regulated HCC cell proliferation, apoptosis and cell cycle by inhibiting ERG expression via the PPARγ pathway. The human hepatoma cells (HepG2) were transfected with the XPD overexpression vector (pEGFP-N2/XPD) or empty vector (pEGFP-N2). The PPARγ inhibitor GW9662 was used to determine whether XPD effects were mediated by activation of PPARγ pathway. Cell cycle and apoptosis were ascertained by flow cytometry, and cell viability was measured by MTT assay. Reverse transcription-polymerase chain reaction and Western blot were performed to determine the mRNA and protein levels. Overexpression of XPD significantly enhanced the expression of PPARγ and p-PPARγ, whereas it downregulated that of ERG and cdk7. Furthermore, XPD overexpression notably inhibited proliferation, promoted apoptosis and decreased the percentage of cells in the S + G2 phase of HepG2 cells. However, these effects of XPD overexpression were abrogated by GW9662. Collectively, XPD suppresses proliferation and promotes apoptosis of HepG2 cells by downregulating ERG expression via activation of the PPARγ pathway.

XPD inhibits cell growth and invasion and enhances chemosensitivity in esophageal squamous cell carcinoma by regulating the PI3K/AKT signaling pathway

Esophageal squamous cell carcinoma (ESCC) is a lethal disease due to its high aggressiveness. The aim of the present study was to investigate the role of xeroderma pigmentosum complementation group D (XPD) in the growth and invasion of ESCC and to elucidate the potential underlying molecular mechanisms. Western blot analysis and RT-qPCR were used to detect the expression level of XPD in ESCC tissue samples and adjacent normal esophageal tissue samples. The pEGFP-N2/XPD plasmid was transfected into human ESCC cell lines (EC9706 and EC109). The proliferation, apoptosis, migration and invasion of EC9706 or EC109 cells were assessed following transfection with the XPD overexpression plasmid. The chemosensitivity of EC9706 or EC109 cells to cisplatin or fluorouracil was evaluated by CCK-8 assay. The expression levels of phosphoinositide 3-kinase (PI3K)/AKT, nuclear factor (NF)-κB, Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and mitogen-activated protein kinase (MAPK) signaling pathway-related genes were detected by RT-qPCR and western blot analysis. The results demonstrated that the expression level of XPD was markedly lower in ESCC tissue samples than in adjacent normal esophageal tissue samples. The pEGFP-N2/XPD plasmid was successfully transfected into EC9706 or EC109 cells, inducing XPD overexpression. A High XPD expression markedly suppressed cell proliferation, migration and invasion, and increased the apoptotic rate of EC9706 and EC109 cells. Furthermore, the overexpression of XPD significantly increased the chemosensitivity of EC9706 and EC109 cells to cisplatin or fluorouracil. Following XPD overexpression, the expression levels of PI3K, p-AKT, c-Myc, Cyclin D1, Bcl-2, vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-9 were markedly downregulated, while the expression level of p21 was markedly upregulated. On the whole, the findings of the present study demonstrate that XPD inhibits the growth and invasion of EC9706 and EC109 cells, whilst also enhancing the chemosensitivity of EC9706 and EC109 cells to cisplatin or fluorouracil by regulating the PI3K/AKT signaling pathway. XPD may thus be an underlying target for ESCC treatment and drug resistance.

Associations of mRNA expression of DNA repair genes and genetic polymorphisms with cancer risk: a bioinformatics analysis and meta-analysis

A systematical bioinformatics and meta-analysis were carried out to establish our understanding of possible relationships between DNA repair genes and the development of cancer. The bioinformatics analysis confirmed that lower XPA and XPC levels and higher XPD, XPF, and WRN levels were observed in 19 types of cancer, and subsequently results indicated that elevated XPA and XPC had a better impact on overall survival, however, higher XPD, XPF, and WRN showed worse influence on cancer prognosis. The meta-analysis included 58 eligible studies demonstrated that harboring XPA rs10817938, XPD rs238406 increased overall cancer risk, however, XPA rs2808668 SNP in overall cancer analysis and XPF rs3136038 in the digestive system remarkably reduced the cancer risk. Moreover, no correlation was investigated for XPC rs1870134, WRN rs1346044 and rs1801195. These suggest that the DNA repair gene was associated with carcinogenesis, and contribute to the prognosis, and the critical SNPs further involved in affecting cancer risk.

XPD suppresses cell proliferation and migration via miR-29a-3p-Mdm2/PDGF-B axis in HCC

Objective

The aim of this study was to investigate the role of XPD in migration and invasion of hepatocellular carcinoma (HCC) cells.

Methods

The expression of XPD and miR-29a-3p was examined by western blot and qRT-PCR, cell proliferation was detected by MTT assay, cell migration was detected by transwell assay. TargetScan was used to predict potential targets of miR-29a-3p.

Results

In this study, we found that the expression of XPD and miR-29a-3p was downregulated in HCC samples and HCC cell lines. XPD suppressed proliferation and migration of HCC cell via regulating miR-29a-3p expression. Target prediction analysis and dual-luciferase reporter assay confirmed Mdm2 and PDGF-B were direct targets of miR-29a-3p, and miR-29a-3p suppressed proliferation and migration of HCC cells via regulating the expression of Mdm2 or PDGF-B.

Conclusions

Our data indicated that XPD suppressed cell proliferation and migration via miR-29a-3p-Mdm2/PDGF-B axis in HCC.

Silencing of Xeroderma Pigmentosum Group D Gene Promotes Hepatoma Cell Growth by Reducing P53 Expression

BACKGROUND This study investigated the effect of xeroderma pigmentosum group D (XPD) silencing on the growth of hepatoma cells and assessed the mechanisms. MATERIAL AND METHODS XPD gene was silenced by siRNA in hepatoma cells. The experiments were randomly divided into a control group, a liposome control group, a negative control (NC) group, an XPD siRNA group, and an XPD siRNA + P53 inhibitor group. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) was used to detect cell viability 24 h after gene silencing and treatments. Terminal deoxynucleotidyl transferases (TdT)-mediated dUTP nick-end labeling (TUNEL) and flow cytometry were used to detect apoptosis. Invasive ability was detected by Transwell assay. Additionally, the expression of mouse double-minute 2 homolog (Mdm2), mouse double-minute 4 homolog (Mdm4), CyclinD1, P21, Bax, P53, C-sis, and Bcl-2 was detected by real-time polymerase chain reaction and Western blotting. RESULTS Compared with the NC group, XPD siRNA significantly reduced XPD expression at both mRNA and protein levels. XPD siRNA significantly promoted cell proliferation, reduced apoptosis, and promoted cell invasive ability. Expression of CyclinD1, Bcl-2, and C-sis increased significantly after XPD silencing, while the expression of P21, Mdm2, Mdm4, Bax, and P53 significantly decreased (vs. NC, P<0.05). Importantly, P53 inhibitor (1 μM bpV) further enhanced the effect of XPD silencing (vs. XPD silencing, P<0.05). CONCLUSIONS Our data revealed that XPD silencing promoted growth of hepatoma cells by reducing P53 expression.

ERCC2/XPD Lys751Gln alter DNA repair efficiency of platinum-induced DNA damage through P53 pathway

Platinum-based treatment causes Pt-DNA adducts which lead to cell death. The platinum-induced DNA damage is recognized and repaired by the nucleotide excision repair (NER) system of which ERCC2/XPD is a critical enzyme. Single nucleotide polymorphisms in ERCC2/XPD have been found to be associated with platinum resistance. The aim of the present study was to investigate whether ERCC2/XPD Lys751Gln (rs13181) polymorphism is causally related to DNA repair capacity of platinum-induced DNA damage. First, cDNA clones expressing different genotypes of the polymorphism was transfected to an ERCC2/XPD defective CHO cell line (UV5). Second, all cells were treated with cisplatin. Cellular survival rate were investigated by MTT growth inhibition assay, DNA damage levels were investigated by comet assay and RAD51 staining. The distribution of cell cycle and the change of apoptosis rates were detected by a flow cytometric method (FCM). Finally, P53mRNA and phospho-P53 protein levels were further investigated in order to explore a possible explanation. As expected, there was a significantly increased in viability of UV5^{ERCC2 (AA)} as compared to UV5^{ERCC2 (CC)} after cisplatin treatment. The DNA damage level of UV5^{ERCC2 (AA)} was significant decreased compared to UV5^{ERCC2 (CC)} at 24 h of treatment. Mutation of ERCC2rs13181 AA to CC causes a prolonged S phase in cell cycle. UV5^{ERCC2 (AA)} alleviated the apoptosis compared to UV5^{ERCC2 (CC)}, meanwhile P53mRNA levels in UV^{ERCC2 (AA)} was also lower when compared UV5^{ERCC2 (CC)}. It co-incides with a prolonged high expression of phospho-P53, which is relevant for cell cycle regulation, apoptosis, and the DNA damage response (DDR). We concluded that ERCC2/XPD rs13181 polymorphism is possibly related to the DNA repair capacity of platinum-induced DNA damage. This functional study provides some clues to clarify the relationship between cisplatin resistance and ERCC2/XPDrs13181 polymorphism.

XPD Functions as a Tumor Suppressor and Dysregulates Autophagy in Cultured HepG2 Cells

Background

Recent clinical studies have linked polymorphisms in the xeroderma pigmentosum group D (XPD) gene, a key repair gene involved in nucleotide excision repair, to increased risk of hepatocellular carcinoma (HCC). However, the cellular effects of XPD expression in cultured HCC cells remain largely uncharacterized. Therefore, the aim of this study was to characterize the in vitro cellular effects of XPD expression on the HCC cell line HepG2.

Material/Methods

HepG2 cells were transfected as follows to create four experimental groups: pEGFP-N2/XPD plasmid (XPD) group, EGFP-N2 plasmid (N2) control group, lipofectamine™ 2000 (lipid) control group, and non-transfected (CON) control group. An MTT cell proliferation assay, Annexin V-APC apoptosis assay, colony formation assay, scratch wound migration assay, Transwell migration assay, and Western blotting of the autophagic proteins LC3 and p62 were conducted.

Results

XPD expression significantly inhibited HepG2 cell proliferation (p<0.05), significantly promoted HepG2 cell apoptosis (p<0.05), significantly inhibited HepG2 colony formation (p<0.05), significantly decreased HepG2 cells’ migratory ability (p<0.05), and significantly lowered HepG2 cells’ invasive capacity (p<0.05). Western blotting showed that XPD expression significantly increased LC3 expression (p<0.05) and significantly reduced p62 expression (p<0.05).

Conclusions

XPD expression serves as a tumor suppressor and dysregulates autophagic protein degradation in HepG2 cells in vitro. Further in vivo pre-clinical studies and clinical trials are needed to validate XPD’s potential as a tumor-suppressive gene therapy.