Human hepatocellular carcinoma expresses specific PCNA isoforms: an in vivo and in vitro evaluation

Natural bioactive compounds and STAT3 against hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is a challenging and very fatal liver cancer. The signal transducer and activator of transcription 3 (STAT3) pathway is a crucial regulator of tumor development and are ubiquitously active in HCC. Therefore, targeting STAT3 has emerged as a promising approach for preventing and treating HCC. Various natural bioactive compounds (NBCs) have been proven to target STAT3 and have the potential to prevent and treat HCC as STAT3 inhibitors. Numerous kinds of STAT3 inhibitors have been identified, including small molecule inhibitors, peptide inhibitors, and oligonucleotide inhibitors. Due to the undesirable side effects of the conventional therapeutic drugs against HCC, the focus is shifted to NBCs derived from plants and other natural sources. NBCs can be broadly classified into the categories of terpenes, alkaloids, carotenoids, and phenols. Most of the compounds belong to the family of terpenes, which prevent tumorigenesis by inhibiting STAT3 nuclear translocation. Further, through STAT3 inhibition, terpenes downregulate matrix metalloprotease 2 (MMP2), matrix metalloprotease 9 (MMP9) and vascular endothelial growth factor (VEGF), modulating metastasis. Terpenes also suppress the anti-apoptotic proteins and cell cycle markers. This review provides comprehensive information related to STAT3 abrogation by NBCs in HCC with in vitro and in vivo evidences.

Expression of nonmuscle myosin IIC is regulated by non-canonical binding activity of miRNAs

The expression of mechanoresponsive nonmuscle myosin II (NMII)C is found to be inducible during tumor progression, but its mechanism is yet to be explored. Here, we report a group of microRNAs (mmu-miR-200a-5p, mmu-miR-532-3p, mmu-miR-680, and mmu-miR-1901) can significantly repress the expression of nonmuscle myosin IIC (NMIIC). Interestingly, these microRNAs have both canonical and non-canonical binding sites at 3/UTR and coding sequence (CDS) of NMIIC's heavy chain (HC) mRNA. Each of the miRNA downregulates NMHC-IIC to a different degree as assessed by dual-luciferase and immunoblot analyses. When we abolish the complementary base pairing at canonical binding site, mmu-miR-532-3p can still bind at non-canonical binding site and form Argonaute2 (AGO2)-miRNA complex to downregulate the expression of NMIIC. Modulating the expression of NMIIC by miR-532-3p in mouse mammary tumor cells, 4T1, increases its tumorigenic potential both in vitro and in vivo. Together, these studies provide the functional role of miRNA's non-canonical binding mediated NMIIC regulation in tumor cells.

The potential of PCNA inhibition as a therapeutic strategy in cervical cancer

Cervical cancers are the fourth most common and most deadly cancer in women worldwide. Despite being a tremendous public health burden, few novel approaches to improve care for these malignancies have been introduced. We discuss the potential for proliferating cell nuclear antigen (PCNA) inhibition to address this need as well as the advantages and disadvantages for compounds that can therapeutically inhibit PCNA with a specific focus on cervical cancer.

Novel Peptide Therapeutic Approaches for Cancer Treatment

Peptides are increasingly being developed for use as therapeutics to treat many ailments, including cancer. Therapeutic peptides have the advantages of target specificity and low toxicity. The anticancer effects of a peptide can be the direct result of the peptide binding its intended target, or the peptide may be conjugated to a chemotherapy drug or radionuclide and used to target the agent to cancer cells. Peptides can be targeted to proteins on the cell surface, where the peptide–protein interaction can initiate internalization of the complex, or the peptide can be designed to directly cross the cell membrane. Peptides can induce cell death by numerous mechanisms including membrane disruption and subsequent necrosis, apoptosis, tumor angiogenesis inhibition, immune regulation, disruption of cell signaling pathways, cell cycle regulation, DNA repair pathways, or cell death pathways. Although using peptides as therapeutics has many advantages, peptides have the disadvantage of being easily degraded by proteases once administered and, depending on the mode of administration, often have difficulty being adsorbed into the blood stream. In this review, we discuss strategies recently developed to overcome these obstacles of peptide delivery and bioavailability. In addition, we present many examples of peptides developed to fight cancer.

Hepatocarcinogenesis Prevention by Pirfenidone Is PPARγ Mediated and Involves Modification of Nuclear NF-kB p65/p50 Ratio

Targeted therapies for regulating processes such as inflammation, apoptosis, and fibrogenesis might modulate human HCC development. Pirfenidone (PFD) has shown anti-fibrotic and anti-inflammatory functions in both clinical and experimental studies. The aim of this study was to evaluate PPARγ expression and localization in samples of primary human tumors and assess PFD-effect in early phases of hepatocarcinogenic process. Human HCC tissue samples were obtained by surgical resection. Experimental hepatocarcinogenesis was induced in male Fischer-344 rats. TGF-β1 and α-SMA expression was evaluated as fibrosis markers. NF-kB cascade, TNFα, IL-6, and COX-2 expression and localization were evaluated as inflammation indicators. Caspase-3, p53, and PARP-1 were used as apoptosis markers, PCNA for proliferation. Finally, PPARα and PPARγ expression were evaluated to understand the effect of PFD on the activation of such pathways. PPARγ expression was predominantly localized in cytoplasm in human HCC tissue. PFD was effective to prevent histopathological damage and TGF-β1 and α-SMA overexpression in the experimental model. Anti-inflammatory effects of PFD correlate with diminished IKK and decrease in both IkB-phosphorylation/NF-kB p65 expression and p65-translocation into the nucleus. Pro-apoptotic PFD-induced effects are related with p53 expression, Caspase-3 p17 activation, and PARP-1-cleavage. In conclusion, PFD acts as a tumor suppressor by preventing fibrosis, reducing inflammation, and promoting apoptosis in MRHM.

Anticancer Effects of Tacrolimus on Induced Hepatocellular Carcinoma in Mice

BACKGROUND

Tacrolimus is a calcineurin inhibitor widely used for immunological disorders. However, there is a significant controversy regarding its effect on the liver. The present study was conducted to evaluate the anticancer effects of tacrolimus on an induced murine hepatocellular carcinoma (HCC) model and its possible hepatotoxicity at standard therapeutic doses.

METHODS

Fifty-four male mice were divided into five groups: a control healthy group, control HCC group, tacrolimus-treated group, doxorubicin (DOXO)-treated group, and combined tacrolimus- and DOXO-treated group. The activity of liver enzymes, including alkaline phosphatase, gamma-glutamyl transferase, lactate dehydrogenase, alanine transaminase, and aspartate transaminase, was determined. Serum vascular endothelial growth factor (VEGF) was measured using an enzyme-linked immunosorbent assay. A quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to measure the expression of proliferating cell nuclear antigen (PCNA), Bax, and p53 mRNA. Immunohistochemical staining for cyclin D1 and VEGF was performed.

RESULTS

Mice that received combined treatment with tacrolimus and DOXO exhibited the best improvement in all parameters when compared with the groups that received DOXO or tacrolimus alone (p < 0.001).

CONCLUSION

The combination of DOXO and tacrolimus was more effective in the management of HCC compared with either agent alone. This improvement was detected by the reduction of liver enzymes and the improvement of the histopathological picture. The involved mechanisms included significant apoptosis induction demonstrated by upregulation of bax along with a reduction in angiogenesis demonstrated by downregulation of VEGF. This was accompanied by inhibition of cell cycle progression mediated by upregulated p53 and downregulated PCNA and cyclin D1.

Evaluation of cytotoxic activity and anticancer potential of indigenous Rosemary (Rosmarinus officinalis L.) and Oregano (Origanum vulgare L.) dry extracts on MG-63 bone osteosarcoma human cell line

We aimed to investigate the cytotoxic activity of indigenous Rosemary and Oregano freeze-dried extracts upon MG-63 osteosarcoma human cell line. We have determined the influence of analyzed dry extracts on cell morphology, cell survival and cell proliferation. The evaluation of dry extracts effect upon cell proliferation and viability was assessed by means of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) method. For cytotoxicity evaluation, Live & Dead and lactate dehydrogenase assays have been used. To further investigate the potential anticancer effect, we have studied the influence of dry extracts upon cells, by means of caspase-3/7 assay and proliferation cell nuclear antigen (PCNA) expression. Cells were incubated with extracts in the following concentration range (100–700 μg/mL) for 24 hours. According to our results, both dry extracts have shown cytotoxic effects by means of all used methods. Bone osteosarcoma cells viability significantly decreased with increasing concentration of analyzed extracts (beyond 300 μg/mL for Rosemary dry extract and only at 700 μg/mL for Oregano dry extract). According to our results, apoptosis is one of the main mechanisms involved in the cytotoxic properties of analyzed extracts. Moreover, Rosemary extract has also shown decreased expression of PCNA, when compared to control (untreated cells). Both extracts were standardized in phenolic compounds (being a rich source of flavones and phenolcarboxylic acids), so we assume that these are the main constituents involved in the cytotoxic effect. Still, further preclinical studies are needed to confirm the antitumor properties and to go deeply in the molecular mechanisms involved.

Targeting Non-Oncogene Addiction for Cancer Therapy

While Next-Generation Sequencing (NGS) and technological advances have been useful in identifying genetic profiles of tumorigenesis, novel target proteins and various clinical biomarkers, cancer continues to be a major global health threat. DNA replication, DNA damage response (DDR) and repair, and cell cycle regulation continue to be essential systems in targeted cancer therapies. Although many genes involved in DDR are known to be tumor suppressor genes, cancer cells are often dependent and addicted to these genes, making them excellent therapeutic targets. In this review, genes implicated in DNA replication, DDR, DNA repair, cell cycle regulation are discussed with reference to peptide or small molecule inhibitors which may prove therapeutic in cancer patients. Additionally, the potential of utilizing novel synthetic lethal genes in these pathways is examined, providing possible new targets for future therapeutics. Specifically, we evaluate the potential of TONSL as a novel gene for targeted therapy. Although it is a scaffold protein with no known enzymatic activity, the strategy used for developing PCNA inhibitors can also be utilized to target TONSL. This review summarizes current knowledge on non-oncogene addiction, and the utilization of synthetic lethality for developing novel inhibitors targeting non-oncogenic addiction for cancer therapy.

Inhibitory and ameliorative effect of heliomycin derived from actinomycete on induced hepatocellular carcinoma in rats

The hepatoprotective activity of heliomycin obtained from the culture broth of actinomycete AB5 against diethylnitrosamine (DEN)-induced hepatic cancer in Wistar rats was estimated. Heliomycin exhibited a significant decrease in the levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) compared to the positive control. For instance, the heliomycin group after 20 weeks showed a significant decline in ALT, AST, and ALP values (70.75 ± 5.12, 140.25 ± 11.75, and 163.25 ± 18.66, respectively) compared to the positive control group (170.00 ± 9.55, 252.75 ± 12.33, and 278.00 ± 21.32, respectively). Additionally, the isolated compound showed a highly significant decrease in serum alpha-fetoprotein (AFP) levels. After 8, 16, and 20 weeks, the mean values of AFP in the heliomycin group revealed a highly significant decrease (33.62 ± 2.46, 30.00 ± 4.05, and 28.50 ± 2.64, respectively) compared to the positive control group (49.45 ± 3.03, 81.90 ± 6.70, and 90.75 ± 5.12, respectively). The histopathological investigation of liver sections supported the results of biochemical analysis. It was demonstrated that heliomycin showed histological improvement of hepatocytes and marked increase of nuclear pyknotic with clear cytoplasm, which is a sign of improving the apoptotic pathway of malignant cells. It also displayed marked fibrosis at most of the malignant cells and the development of some regenerative nodules. Heliomycin showed moderate immunoreactivity with alpha-fetoprotein (AFP), and proliferation cell nuclear antigen (PCNA) compared to the positive control group. To the best of our knowledge, this is the first study to report the anticancer activity of heliomycin against hepatocellular carcinoma in vivo.

Targeting Proliferating Cell Nuclear Antigen (PCNA) as an Effective Strategy to Inhibit Tumor Cell Proliferation

Targeting highly proliferating cells is an important issue for many types of aggressive tumors. Proliferating Cell Nuclear Antigen (PCNA) is an essential protein that participates in a variety of processes of DNA metabolism, including DNA replication and repair, chromatin organization and transcription and sister chromatid cohesion. In addition, PCNA is involved in cell survival, and possibly in pathways of energy metabolism, such as glycolysis. Thus, the possibility of targeting this protein for chemotherapy against highly proliferating malignancies is under active investigation. Currently, approaches to treat cells with agents targeting PCNA rely on the use of small molecules or on peptides that either bind to PCNA, or act as a competitor of interacting partners. Here, we describe the status of the art in the development of agents targeting PCNA and discuss their application in different types of tumor cell lines and in animal model systems.

GTSE1, CDC20, PCNA, and MCM6 Synergistically Affect Regulations in Cell Cycle and Indicate Poor Prognosis in Liver Cancer

GTSE1 is well correlated with tumor progression; however, little is known regarding its role in liver cancer prognosis. By analyzing the hepatocellular carcinoma (HCC) datasets in GEO and TCGA databases, we showed that high expression of GTSE1 was correlated with advanced pathologic stage and poor prognosis of HCC patients. To investigate underlying molecular mechanism, we generated GTSE1 knockdown HCC cell line and explored the effects of GTSE1 deficiency in cell growth. Between GTSE1 knockdown and wild-type HCC cells, we identified 979 differentially expressed genes (520 downregulated and 459 upregulated genes) in the analysis of microarray-based gene expression profiling. Functional enrichment analysis of DEGs suggested that S phase was dysregulated without GTSE1 expression, which was further verified from flow cytometry analysis. Moreover, three other DEGs: CDC20, PCNA, and MCM6, were also found contributing to GTSE1-related cell cycle arrest and to be associated with poor overall survival of HCC patients. In conclusion, GTSE1, together with CDC20, PCNA, and MCM6, may synergistically promote adverse prognosis in HCC by activating cell cycle. Genes like GTSE1, CDC20, PCNA, and MCM6 may be promising prognostic molecular biomarkers in liver cancer.

Potential Antitumor Activity and Apoptosis Induction of Glossostemon bruguieri Root Extract against Hepatocellular Carcinoma Cells

Glossostemon bruguieri (moghat) is used as a nutritive and demulcent drink. This study was performed to investigate the antiproliferative effects of moghat root extract (MRE) and its apoptotic mechanism in hepatocellular carcinoma (HCC) cells, HepG2 and Hep3B. MTT assay, morphological changes, apoptosis enzyme linked immunosorbent assay, caspase and apoptotic activation, flow cytometry, and immunoblot analysis were employed. The IC₅₀ of MRE for HepG2 (910 ± 6 μg/ml) and for Hep3B (1510 ± 5 μg/ml) induced significant growth-inhibitory effects against HCC cells, with no cytotoxic effect on normal hepatocytes. MRE treatment induced apoptotic effects to HepG2 cells in a caspase-dependent manner and via upregulating p53/p21 and PCNA. The upregulation of p21 was controlled by p53 expression in HepG2 but not in Hep3B despite upregulation of Bax protein in both cell lines. Interestingly, p21 may be a remarkable switch to G1 arrest in HepG2 cells, but not in Hep3B cells. In addition, Fas- and mitochondria-mediated pathways were found to be involved in MRE-induced apoptosis in Hep3B cells. The GC-MS analysis of MRE revealed two major constituents of pharmaceutical importance: the flavonoid apigenin (17.04%) and the terpenoid squalene (11.32%). The data presented in this paper introduces G. bruguieri as a promising nontoxic herb with therapeutic potential for HCC. To the authors' knowledge, the present study provides the first report on the anticancer activity of MRE on HCC cells.

Validating the disruption of proliferating cell nuclear antigen interactions in the development of targeted cancer therapeutics

Human DNA replication and repair is a highly coordinated process involving the specifically timed actions of numerous proteins and enzymes. Many of these proteins require interaction with proliferating cell nuclear antigen (PCNA) for activation within the process. The interdomain connector loop (IDCL) of PCNA provides a docking site for many of those proteins, suggesting that this region is critically important in the regulation of cellular function. Previous work in this laboratory has demonstrated that a peptide mimicking a specific region of the IDCL (caPeptide) has the ability to disrupt key protein-protein interactions between PCNA and its binding partners, thereby inhibiting DNA replication within the cells. In this study, we confirm the ability of the caPeptide to disrupt DNA replication function using both intact cell and in vitro DNA replication assays. Further, we were able to demonstrate that treatment with caPeptide results in a decrease of polymerase δ activity that correlates with the observed decrease in DNA replication. We have also successfully developed a surface plasmon resonance (SPR) assay to validate the disruption of the PCNA-pol δ interaction with caPeptide.

A Peptide mimicking a region in proliferating cell nuclear antigen specific to key protein interactions is cytotoxic to breast cancer

Proliferating cell nuclear antigen (PCNA) is a highly conserved protein necessary for proper component loading during the DNA replication and repair process. Proteins make a connection within the interdomain connector loop of PCNA, and much of the regulation is a result of the inherent competition for this docking site. If this target region of PCNA is modified, the DNA replication and repair process in cancer cells is potentially altered. Exploitation of this cancer-associated region has implications for targeted breast cancer therapy. In the present communication, we characterize a novel peptide (caPeptide) that has been synthesized to mimic the sequence identified as critical to the cancer-associated isoform of PCNA. This peptide is delivered into cells using a nine-arginine linking mechanism, and the resulting peptide (R9-cc-caPeptide) exhibits cytotoxicity in a triple-negative breast cancer cell line, MDA-MB-436, while having less of an effect on the normal counterparts (MCF10A and primary breast epithelial cells). The novel peptide was then evaluated for cytotoxicity using various in vivo techniques, including ATP activity assays, flow cytometry, and clonogenetic assays. This cytotoxicity has been observed in other breast cancer cell lines (MCF7 and HCC1937) and other forms of cancer (pancreatic and lymphoma). R9-cc-caPeptide has also been shown to block the association of PCNA with chromatin. Alanine scanning of the peptide sequence, combined with preliminary in silico modeling, gives insight to the disruptive ability and the molecular mechanism of action of the therapeutic peptide in vivo.

PCNA: a silent housekeeper or a potential therapeutic target?

Proliferating cell nuclear antigen (PCNA) is known as a molecular marker for proliferation given its role in replication. Three identical molecules of PCNA form a molecular sliding clamp around the DNA double helix. This provides an essential platform on which multiple proteins are dynamically recruited and coordinately regulated. Over the past decade, new research has provided a deeper comprehension of PCNA as a coordinator of essential cellular functions for cell growth, death, and maintenance. Although the biology of PCNA in proliferation has been comprehensively reviewed, research progress in unveiling the potential of targeting PCNA for disease treatment has not been systematically discussed. Here we briefly summarize the basic structural and functional characteristics of PCNA, and then discuss new developments in its protein interactions, trimer formation, and signaling regulation that open the door to possible therapeutic targeting of PCNA.

Reconstructing dynamic gene regulatory networks from sample-based transcriptional data

The current method for reconstructing gene regulatory networks faces a dilemma concerning the study of bio-medical problems. On the one hand, static approaches assume that genes are expressed in a steady state and thus cannot exploit and describe the dynamic patterns of an evolving process. On the other hand, approaches that can describe the dynamical behaviours require time-course data, which are normally not available in many bio-medical studies. To overcome the limitations of both the static and dynamic approaches, we propose a dynamic cascaded method (DCM) to reconstruct dynamic gene networks from sample-based transcriptional data. Our method is based on the intra-stage steady-rate assumption and the continuity assumption, which can properly characterize the dynamic and continuous nature of gene transcription in a biological process. Our simulation study showed that compared with static approaches, the DCM not only can reconstruct dynamical network but also can significantly improve network inference performance. We further applied our method to reconstruct the dynamic gene networks of hepatocellular carcinoma (HCC) progression. The derived HCC networks were verified by functional analysis and network enrichment analysis. Furthermore, it was shown that the modularity and network rewiring in the HCC networks can clearly characterize the dynamic patterns of HCC progression.

Elevated expression of cancer-associated proliferating cell nuclear antigen in high-grade prostatic intraepithelial neoplasia and prostate cancer

BACKGROUND

Proliferating cell nuclear antigen (PCNA) plays an important role in DNA replication and repair. The expression and potential utility of this marker in prostatic neoplasia is uncertain. With the development of this new caPCNA selective antibody, we explored the potential utility of this marker in prostate cancer.

METHODS

Using a traditional primary Fab2' rabbit anti-caPCNA antibody-HRP conjugated secondary anti-Fab2' antibody format, the expression of the caPCNA was analyzed in prostate tissue from 89 radical prostatectomy specimens. The caPCNA expression was correlated with clinicopathologic characteristics.

RESULTS

The fraction of cells staining positively with caPCNA antibody in prostatic adenocarcinoma (mean, 23%) was significantly higher than that in benign prostatic epithelium (mean, 2%; P < 0.001) or high-grade prostatic intraepithelial neoplasia (PIN) (mean, 6%; P < 0.05). Moreover, the intensity of caPCNA expression in prostatic adenocarcinoma (mean, 2.9) was significantly higher than that in benign prostatic tissue (mean, 0.7; P < 0.001) or high-grade PIN (mean, 2.0; P < 0.001). Benign prostatic epithelium showed only minimal or negative reactivity. There was significant correlation between the percentage of caPCNA expression and primary Gleason grade (P = 0.01), and with Gleason score (P = 0.02). Adenocarcinomas with positive vascular invasion had a significantly higher percentage of cells staining with caPCNA antibody (P < 0.0001) and a higher intensity of caPCNA expression (P = 0.04).

CONCLUSIONS

Our data indicate that increased expression of the cancer-associated isoform of PCNA is common in prostatic adenocarcinoma and its precursor and may be a useful biomarker.

Proteomic mining in the dysplastic liver of WHV/c-myc mice--insights and indicators for early hepatocarcinogenesis

Because of the asymptomatic process of carcinogenesis, the early detection of cancers such as hepatocellular carcinoma (HCC) is very challenging. Tumor-prone transgenic mouse models of oncogenesis can provide a stable and powerful tool for the analysis of cancer initiation, and are therefore promising for the discovery of early putative biomarkers of HCC. Using a label-free proteomic quantification strategy, we comprehensively investigated the protein expression profile in the livers of three 2-month-old WHV/c-myc mice at the dysplastic stage, with age-matched wt-C57 mice as controls. We identified 2781 proteins, 540 of which were differentially expressed. These proteins successfully characterized certain precancerous biological processes and alterations in transcriptional regulators before tumor onset. Two candidates, FK506-binding protein 4 (FKBP52) and ferritin heavy chain, were taken as examples for a search from the mouse model to clinical human tissues. Their levels in serum samples were determined by western blotting, and showed a noteworthy ability to distinguish between HCC and control cases. Immunohistochemical analysis with tissue microarrays confirmed the differential expression of FKBP52 between HCC and the paired controls (P < 0.001). The regulation of FKBP52 was also discovered to be relevant to HCC staging, with a dramatic decline at stage III (P < 0.05). The potentials of the candidate pool in this study were discussed in terms of delineating c-myc-induced hepatocarcinogenesis and facilitating biomarker discovery for early HCC diagnosis.