PARP-1 serves as a novel molecular marker for hepatocellular carcinoma in a Southern Chinese Zhuang population

Disrupting Poly(ADP-ribosyl)ating Pathway Creates Premalignant Conditions in Mammalian Liver

Hepatocellular carcinoma (HCC) is a major global health concern, representing one of the leading causes of cancer-related deaths. Despite various treatment options, the prognosis for HCC patients remains poor, emphasizing the need for a deeper understanding of the factors contributing to HCC development. This study investigates the role of poly(ADP-ribosyl)ation in hepatocyte maturation and its impact on hepatobiliary carcinogenesis. A conditional Parg knockout mouse model was employed, utilizing Cre recombinase under the albumin promoter to target Parg depletion specifically in hepatocytes. The disruption of the poly(ADP-ribosyl)ating pathway in hepatocytes affects the early postnatal liver development. The inability of hepatocytes to finish the late maturation step that occurs early after birth causes intensive apoptosis and acute inflammation, resulting in hypertrophic liver tissue with enlarged hepatocytes. Regeneration nodes with proliferative hepatocytes eventually replace the liver tissue and successfully fulfill the liver function. However, early developmental changes predispose these types of liver to develop pathologies, including with a malignant nature, later in life. In a chemically induced liver cancer model, Parg-depleted livers displayed a higher tendency for hepatocellular carcinoma development. This study underscores the critical role of the poly(ADP-ribosyl)ating pathway in hepatocyte maturation and highlights its involvement in liver pathologies and hepatobiliary carcinogenesis. Understanding these processes may provide valuable insights into liver biology and liver-related diseases, including cancer.

Combining Crocin and Sorafenib Improves Their Tumor-Inhibiting Effects in a Rat Model of Diethylnitrosamine-Induced Cirrhotic-Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most aggressive malignancies, with continuously increasing cases and fatalities. Diagnosis often occurs in the advanced stages, confining patients to systemic therapies such as sorafenib. Sorafenib (SB), a multi-kinase inhibitor, has not yet demonstrated sufficient efficacy against advanced HCC. There is a strong argument in favor of studying its use in combination with other medications to optimize the therapeutic results. According to our earlier work, crocin (CR), a key bioactive component of saffron, hinders HCC development and liver cancer stemness. In this study, we investigated the therapeutic use of CR or its combination with SB in a cirrhotic rat model of HCC and evaluated how effectively SB and CR inhibited tumor growth in this model. Diethylnitrosamine (DEN) was administered intraperitoneally to rats once a week for 15 weeks, leading to cirrhosis, and then 19 weeks later, leading to multifocal HCC. After 16 weeks of cancer induction, CR (200 mg/kg daily) and SB (10 mg/kg daily) were given orally to rats for three weeks, either separately or in combination. Consistently, the combination treatment considerably decreased the incidence of dyschromatic nodules, nodule multiplicity, and dysplastic nodules when compared to the HCC group of single therapies. Combined therapy also caused the highest degree of apoptosis, along with decreased proliferating and β-catenin levels in the tumor tissues. Additionally, when rats received combined therapy with CR, it showed anti-inflammatory characteristics where nuclear factor kappa B (NF-κB) and cyclooxygenase-2 (Cox-2) were considerably and additively lowered. As a result, CR potentiates the suppressive effects of SB on tumor growth and provides the opportunity to strengthen the therapeutic effects of SB in the treatment of HCC.

The potential of PARP inhibitors in targeted cancer therapy and immunotherapy

DNA damage response (DDR) deficiencies result in genome instability, which is one of the hallmarks of cancer. Poly (ADP-ribose) polymerase (PARP) enzymes take part in various DDR pathways, determining cell fate in the wake of DNA damage. PARPs are readily druggable and PARP inhibitors (PARPi) against the main DDR-associated PARPs, PARP1 and PARP2, are currently approved for the treatment of a range of tumor types. Inhibition of efficient PARP1/2-dependent DDR is fatal for tumor cells with homologous recombination deficiencies (HRD), especially defects in breast cancer type 1 susceptibility protein 1 or 2 (BRCA1/2)-dependent pathway, while allowing healthy cells to survive. Moreover, PARPi indirectly influence the tumor microenvironment by increasing genomic instability, immune pathway activation and PD-L1 expression on cancer cells. For this reason, PARPi might enhance sensitivity to immune checkpoint inhibitors (ICIs), such as anti-PD-(L)1 or anti-CTLA4, providing a rationale for PARPi-ICI combination therapies. In this review, we discuss the complex background of the different roles of PARP1/2 in the cell and summarize the basics of how PARPi work from bench to bedside. Furthermore, we detail the early data of ongoing clinical trials indicating the synergistic effect of PARPi and ICIs. We also introduce the diagnostic tools for therapy development and discuss the future perspectives and limitations of this approach.

PARP1 as a prognostic biomarker for human cancers: a meta-analysis

Aim: A comprehensive meta-analysis was carried out to evaluate the association between high PARP1 expression and clinical outcomes in diverse types of cancers. Materials & methods: The electronic databases for all articles about PARP1 expression and cancers were searched. Additionally, bioinformatics analysis was utilized to validate the results of the meta-analysis. Results: Fifty-two studies with a total of 7140 patients were included in the current meta-analysis. High PARP1 expression was found to be significantly associated with poor overall survival and recurrence in various cancers, which were further strengthened and complemented by the results of bioinformatic analysis. Furthermore, increased PAPR1 expression was also related to clinicopathological features. Conclusion: Our findings confirmed that PARP1 might be a promising biomarker for prognosis in human cancers.

PARP inhibitors and radiation potentiate liver cell death in vitro. Do hepatocellular carcinomas have an achilles' heel?

BACKGROUND

A promising avenue for cancer treatment is exacerbating the deregulation of the DNA repair machinery that would normally protect the genome. To address the applicability of poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) combined with radiotherapy for the treatment of hepatocellular carcinoma (HCC) two approaches were used: firstly, the in vitro sensitivity to the PARPi Veliparib and Talazoparib +/- radiation exposure was determined in liver cell lines and the impact of the HBV X protein (HBx) that deregulates cellular DNA damage repair via SMC5/6 degradation was investigated. Secondly, PARP expression profiles and DNA damage levels using the surrogate marker gammaH2AX were assessed in a panel of control liver vs HCC tissues.

METHODS

Cell cytotoxicity was measured by clonogenic survival or relative cell growth and the DNA damage response using immunological-based techniques in Hep3B, PLC/PRF/5, HepG2- and HepaRG-derived models. Transcriptome changes due to HBx expression vs SMC6 loss were assessed by RNA sequencing in HepaRG-derived models. PARP and PARG transcripts (qPCR) and PARP1, H2AX and gammaH2AX protein levels (RPPA) were compared in control liver vs HBV-, HCV-, alcohol- and non-alcoholic steatohepatitis-associated HCC (tumor/peritumor) tissues.

RESULTS

PARPi cytotoxicity was significantly enhanced when combined with X-rays (2Gy) with Talazoparib having a greater impact than Veliparib in most in vitro models. HBx expression significantly lowered survival, probably driven by SMC5/6 loss based on the transcriptome analysis and higher DNA damage levels. PARP1 and PARP2 transcript levels were significantly higher in tumor than peritumor and control tissues. The HBV/HCV/alcohol-associated tumor tissues studied had reduced H2AX but higher gammaH2AX protein levels compared to peritumor and control tissues providing evidence of increased DNA damage during liver disease progression.

CONCLUSIONS

These proof-of-concept experiments support PARPi alone or combined with radiotherapy for HCC treatment, particularly for HBV-associated tumors, that warrant further investigation.

Deciphering the effects of PYCR1 on cell function and its associated mechanism in hepatocellular carcinoma

Overexpression of pyrroline-5-carboxylate reductase 1 (PYCR1) has been associated with the development of certain cancers; however, no studies have specifically examined the role of PYCR1 in hepatocellular carcinoma (HCC). Based on The Cancer Genome Atlas expression array and meta-analysis conducted using the Gene Expression Omnibus database, we determined that PYCR1 was upregulated in HCC compared to adjacent nontumor tissues (P < 0.05). These data were verified using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry analysis. Additionally, patients with low PYCR1 expression showed a higher overall survival rate than patients with high PYCR1 expression. Furthermore, PYCR1 overexpression was associated with the female sex, higher levels of alpha-fetoprotein, advanced clinical stages (III and IV), and a younger age (< 45 years old). Silencing of PYCR1 inhibited cell proliferation, invasive migration, epithelial-mesenchymal transition, and metastatic properties in HCC in vitro and in vivo. Using RNA sequencing and bioinformatics tools for data-dependent network analysis, we found binary relationships among PYCR1 and its interacting proteins in defined pathway modules. These findings indicated that PYCR1 played a multifunctional role in coordinating a variety of biological pathways involved in cell communication, cell proliferation and growth, cell migration, a mitogen-activated protein kinase cascade, ion binding, etc. The structural characteristics of key pathway components and PYCR1-interacting proteins were evaluated by molecular docking, and hotspot analysis showed that better affinities between PYCR1 and its interacting molecules were associated with the presence of arginine in the binding site. Finally, a candidate regulatory microRNA, miR-2355-5p, for PYCR1 mRNA was discovered in HCC. Overall, our study suggests that PYCR1 plays a vital role in HCC pathogenesis and may potentially serve as a molecular target for HCC treatment.

Activated platelets contribute to the progression of hepatocellular carcinoma by altering the tumor environment

AIM

Hepatocellular carcinoma (HCC) is a primary liver cancer that usually develops in a background of chronic liver disease and prolonged inflammation. A major contributor in the complex molecular pathogenesis of HCC is the highly intertwined cross-talk between the tumor and the surrounding stromal cells, such as hepatic stellate cells, endothelial cells, macrophages and other immune cells. These tumor-stroma interactions actively fuel tumor growth and modulate the hepatic microenvironment to benefit tumor invasion and disease progression. Platelets have been reported to interact with different cell types in the tumor microenvironment, including tumor cells, stellate cells and macrophages.

MATERIALS AND METHODS

Mice were treated with hepatocarcinogenic compound diethylnitrosamine for 25 weeks to induce HCC in the background of fibrosis and inflammation. From week 10, anti-platelet drug Clopidogrel was added to the drinking water and mice were given ad libitum access.

KEY FINDINGS

In this study, we show that activated platelets promote tumor cell proliferation and contribute to the adverse tumor-stroma cross-talk that fuels tumor progression. We also show that inhibiting platelet activation with the P2Y12-inhibitor Clopidogrel decreases the number of tumors in a chemically induced mouse model for HCC.

SIGNIFICANCE

These results suggest an important role for platelets in the pathogenesis of HCC and that the use of anti-platelet drugs may be therapeutically relevant for patients with liver cancer.

Evaluating the role of RAD52 and its interactors as novel potential molecular targets for hepatocellular carcinoma

Background

Radiation sensitive 52 (RAD52) is an important protein that mediates DNA repair in tumors. However, little is known about the impact of RAD52 on hepatocellular carcinoma (HCC). We investigated the expression of RAD52 and its values in HCC. Some proteins that might be coordinated with RAD52 in HCC were also analyzed.

Methods

Global RAD52 mRNA levels in HCC were assessed using The Cancer Genome Atlas (TCGA) database. RAD52 expression was analyzed in 70 HCC tissues and adjacent tissues by quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemistry. The effect of over-expressed RAD52 in Huh7 HCC cells was investigated. The String database was then used to perform enrichment and functional analysis of RAD52 and its interactome. Cytoscape software was used to create a protein–protein interaction network. Molecular interaction studies with RAD52 and its interactome were performed using the molecular docking tools in Hex8.0.0. Finally, these DNA repair proteins, which interact with RAD52, were also analyzed using the TCGA dataset and were detected by qRT-PCR. Based on the TCGA database, algorithms combining ROC between RAD52 and RAD52 interactors were used to diagnose HCC by binary logistic regression.

Results

In TCGA, upregulated RAD52 related to gender was obtained in HCC. The area under the receiver operating characteristic curve (AUC) of RAD52 was 0.704. The results of overall survival (OS) and recurrence-free survival (RFS) indicated no difference in the prognosis between patients with high and low RAD52 gene expression. We validated that RAD52 expression was increased at the mRNA and protein levels in Chinese HCC tissues compared with adjacent tissues. Higher RAD52 was associated with older age, without correlation with other clinicopathological factors. In vitro, over-expressed RAD52 significantly promoted the proliferation and migration of Huh7 cells. Furthermore, RAD52 interactors (radiation sensitive 51, RAD51; X-ray repair cross complementing 6, XRCC6; Cofilin, CFL1) were also increased in HCC and participated in some biological processes with RAD52. Protein structure analysis showed that RAD52–RAD51 had the firmest binding structure with the lowest E-total energy (− 1120.5 kcal/mol) among the RAD52–RAD51, RAD52–CFL1, and RAD52–XRCC6 complexes. An algorithm combining ROC between RAD52 and its interactome indicated a greater specificity and sensitivity for HCC screening.

Conclusions

Overall, our study suggested that RAD52 plays a vital role in HCC pathogenesis and serves as a potential molecular target for HCC diagnosis and treatment. This study’s findings regarding the multigene prediction and diagnosis of HCC are valuable.

PARP Inhibitor PJ34 Protects Mitochondria and Induces DNA-Damage Mediated Apoptosis in Combination With Cisplatin or Temozolomide in B16F10 Melanoma Cells

PARP-1 inhibition has recently been employed in both mono- and combination therapies in various malignancies including melanoma with both promising and contradicting results reported. Although deeper understanding of the underlying molecular mechanisms may help improving clinical modalities, the complex cellular effects of PARP inhibitors make disentangling of the mechanisms involved in combination therapies difficult. Here, we used two cytostatic agents used in melanoma therapies in combination with PARP inhibition to have an insight into cellular events using the B16F10 melanoma model. We found that, when used in combination with cisplatin or temozolomide, pharmacologic blockade of PARP-1 by PJ34 augmented the DNA-damaging and cytotoxic effects of both alkylating compounds. Interestingly, however, this synergism unfolds relatively slowly and is preceded by molecular events that are traditionally believed to support cell survival including the stabilization of mitochondrial membrane potential and morphology. Our data indicate that the PARP inhibitor PJ34 has, apparently, opposing effects on the mitochondrial structure and cell survival. While, initially, it stimulates mitochondrial fusion and hyperpolarization, hallmarks of mitochondrial protection, it enhances the cytotoxic effects of alkylating agents at later stages. These findings may contribute to the optimization of PARP inhibitor-based antineoplastic modalities.