P21-driven multifusion gene system for evaluating the efficacy of histone deacetylase inhibitors by in vivo molecular imaging and for transcription targeting therapy of cancer mediated by histone deacetylase inhibitor

Rosline promotes p21 expression to inhibit ovarian cancer cell proliferation via p53-independent pathway

AIM

To investigate the effect of benzothiazole derivatives (Rosline) on ovarian cancer and the potential mechanism.

METHODS

Ovarian cancer tissues were collected clinically and immunohistochemistry was used to detect the expression of p53 and p21. Ovarian cancer cells were exposed to 0, 2.5, 5, 10 μmol/L Rosline for 24 h. 100 nmol/L Pifithrin-α pre-incubation was used to inhibit the transcriptional activity of p53. CCK-8 and BrdU assays were used to detect the effects of different concentrations of rosline on the proliferation and cell cycle of OVCAR420 and SKOV3 cells. Flow cytometry assay was used to detect cell cycle. The transcriptional and translational expression of p21 and p53 were detected by RT-qPCR and Western blot.

RESULTS

p21 was expressed in ovarian cancer tissues without p53 expression. Rosline inhibits the proliferation of ovarian cancer cells and blocks the cell cycle progression. Meanwhile, Rosline promotes p21 expression in ovarian cancer cells at both mRNA and protein levels, but with no significant effect on p53 expression. Besides, Rosline promotes p21 expression, inhibits cell proliferation, and blocks the cell cycle via the p53-independent pathway.

CONCLUSION

Rosline promoted p21 expression thereby inhibiting cell proliferation and blocks the cell cycle via p53-independent pathway.

Sirtuin 4 Inhibits Prostate Cancer Progression and Metastasis by Modulating p21 Nuclear Translocation and Glutamate Dehydrogenase 1 ADP-Ribosylation

Protein posttranslational modification regulates several biological mechanisms, including tumor progression. In this study, we show that the mitochondrial Sirtuin 4 (SIRT4), which has ADP-ribosylation activity, plays a role in prostate cancer (PCa) progression. Firstly, SIRT4 expression was verified in PCa tissues and cell lines by quantitative real-time PCR (qRT-PCR) and western blotting. Subsequently, we established stable PC-3 and 22rv1 cells that overexpressed SIRT4 and knocked down SIRT4, respectively. The functions of SIRT4 in PCa were explored through various phenotype experiments. The mechanism underlying the functions of SIRT4 was investigated through western blotting, immunoprecipitation, immunofluorescence, and nuclear and cytoplasmic extraction assays. We revealed that SIRT4 inhibited cell progression both in vivo and in vitro. Mechanistically, on the one hand, SIRT4 promoted the ADP-ribosylation of glutamate dehydrogenase 1 to inhibit the glutamine metabolism pathways. On the other hand, SIRT4 inhibited the phosphorylation of AKT, thereby affecting p21 phosphorylation and its cellular localization for cell cycle arrest. In conclusion, our study indicates that SIRT4 is directly associated with PCa progression and could be a novel target for PCa therapy.

δ-Catenin Participates in EGF/AKT/p21Waf Signaling and Induces Prostate Cancer Cell Proliferation and Invasion

Prostate cancer (PCa) is the second most leading cause of death in males. Our previous studies have demonstrated that δ-catenin plays an important role in prostate cancer progression. However, the molecular mechanism underlying the regulation of δ-catenin has not been fully explored yet. In the present study, we found that δ-catenin could induce phosphorylation of p21^Waf and stabilize p21 in the cytoplasm, thus blocking its nuclear accumulation for the first time. We also found that δ-catenin could regulate the interaction between AKT and p21, leading to phosphorylation of p21 at Thr-145 residue. Finally, EGF was found to be a key factor upstream of AKT/δ-catenin/p21 for promoting proliferation and metastasis in prostate cancer. Our findings provide new insights into molecular controls of EGF and the development of potential therapeutics targeting δ-catenin to control prostate cancer progression.

Histone Deacetylase Inhibitors Romidepsin and Vorinostat Promote Hepatitis B Virus Replication by Inducing Cell Cycle Arrest

BACKGROUND AND AIMS

Chronic hepatitis B virus (HBV) infection is a global public health challenge. HBV reactivation usually occurs in cancer patients after receiving cytotoxic chemotherapy or immunosuppressive therapies. Romidepsin (FK228) and vorinostat (SAHA) are histone deacetylase inhibitors (HDACi) approved by the Food and Drug Administration as novel antitumor agents. The aim of this study was to explore the effects and mechanisms of HDACi treatment on HBV replication.

METHODS

To assess these effects, human hepatoma cell lines were cultured and cell viability after FK228 or SAHA treatment was measured by the CCK-8 cell counting kit-8 assay. Then, HBV DNA and RNA were quantified by real-time PCR and Southern blotting. Furthermore, analysis by western blotting, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and flow cytometry was performed.

RESULTS

FK228/SAHA treatment significantly promoted HBV replication and biosynthesis in both HBV-replicating cells and HBV-transgenic mouse model. Flow cytometry assay indicated that FK228/SAHA enhanced HBV replication by inducing cell cycle arrest through modulating the expression of cell cycle regulatory proteins. In addition, simultaneous inhibition of HDAC1/2 by FK228 promoted HBV replication more effectively than the broad spectrum HDAC inhibitor SAHA.

CONCLUSIONS

Overall, our results demonstrate that cell cycle blockage plays an important role in FK228/SAHA-enhanced HBV replication, thus providing a potential avenue for rational use of HDACi in patients with chronic hepatitis B.

STAT3/NF-κB-Regulated Lentiviral TK/GCV Suicide Gene Therapy for Cisplatin-Resistant Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) represents approximately 20% of all breast cancers and appears resistance to conventional cytotoxic chemotherapy, demonstrating a particularly poor prognosis and a significantly worse clinical outcome than other types of cancer. Suicide gene therapy has been used for the in vivo treatment of various solid tumors in recent clinical trials. In tumor microenvironment, STAT3/NF-κB pathways are constitutively activated in stromal cells as well as in cancer stem cells (CSCs). In this study, we have cloned a novel STAT3/NF-κB-based reporter system to drive the expression of herpes simplex virus thymidine kinase (HSV-TK) against breast cancer. Lentiviral vector expressing HSV-TK under the regulation of STAT3/NF-κB fused response element was developed. In this setting, we exploited the constitutive STAT3/NF-κB activation in tumors to achieve higher transgene expression than that driven by a constitutively active CMV promotor in vivo. An orthotropic MDA-MB-231 triple negative breast cancer mouse model was used for evaluating the feasibility of STAT3-NF-κB-TK/GCV suicide gene therapy system.

The basal promoter activity of Lenti-CMV-TK and Lenti-STAT3-NF-κB-TK in MDA-MB-231 cells was compared by ³H-FEAU uptake assay. The Lenti-CMV-TK showed ~5 fold higher ³H-FEAU uptake then Lenti -STAT3-NF-κB-TK. In clonogenic assay, cells expressing Lenti-CMV-TK were 2-fold more sensitive to GCV than Lenti-STAT3-NF-κB-TK transduced cells. In vitro effect of STAT3-NF-κB-induced transgene expression was determined by 10ng/mL TNF-α induction and confirmed by western blot analysis and DsRedm fluorescent microscopy. In vivo evaluation of therapeutic effect by bioluminescence and [¹⁸F]FHBG microPET imaging indicated that Lenti-STAT3-NF-κB-TK showed more tumor growth retardation than Lenti-CMV-TK when GCV (20 mg/kg) was administered. The invasiveness and expression of cancer stem cell markers were both decreased after STAT3/NF-κB-regulated HSV-TK/GCV therapy. Moreover, STAT3/NF-κB signaling targeting could further sensitize tumor cells to cisplatin. This study successfully established a theranositic approach to treat triple-negative breast cancer via STAT3-NF-κB responsive element-driven suicide gene therapy. This platform may also be an alternative strategy to handle with drug-resistant cancer cells.

Multiple functions of p21 in cell cycle, apoptosis and transcriptional regulation after DNA damage

An appropriate control over cell cycle progression depends on many factors. Cyclin-dependent kinase (CDK) inhibitor p21 (also known as p21(WAF1/Cip1)) is one of these factors that promote cell cycle arrest in response to a variety of stimuli. The inhibitory effect of P21 on cell cycle progression correlates with its nuclear localization. P21 can be induced by both p53-dependent and p53-independent mechanisms. Some other important functions attributed to p21 include transcriptional regulation, modulation or inhibition of apoptosis. These functions are largely dependent on direct p21/protein interactions and also on p21 subcellular localizations. In addition, p21 can play a role in DNA repair by interacting with proliferating cell nuclear antigen (PCNA). In this review, we will focus on the multiple functions of p21 in cell cycle regulation, apoptosis and gene transcription after DNA damage and briefly discuss the pathways and factors that have critical roles in p21 expression and activity.

Functional-genetic dissection of HDAC dependencies in mouse lymphoid and myeloid malignancies

Histone deacetylase (HDAC) inhibitors (HDACis) have demonstrated activity in hematological and solid malignancies. Vorinostat, romidepsin, belinostat, and panobinostat are Food and Drug Administration-approved for hematological malignancies and inhibit class II and/or class I HDACs, including HDAC1, 2, 3, and 6. We combined genetic and pharmacological approaches to investigate whether suppression of individual or multiple Hdacs phenocopied broad-acting HDACis in 3 genetically distinct leukemias and lymphomas. Individual Hdacs were depleted in murine acute myeloid leukemias (MLL-AF9;Nras(G12D); PML-RARα acute promyelocytic leukemia [APL] cells) and Eµ-Myc lymphoma in vitro and in vivo. Strikingly, Hdac3-depleted cells were selected against in competitive assays for all 3 tumor types. Decreased proliferation following Hdac3 knockdown was not prevented by BCL-2 overexpression, caspase inhibition, or knockout of Cdkn1a in Eµ-Myc lymphoma, and depletion of Hdac3 in vivo significantly reduced tumor burden. Interestingly, APL cells depleted of Hdac3 demonstrated a more differentiated phenotype. Consistent with these genetic studies, the HDAC3 inhibitor RGFP966 reduced proliferation of Eµ-Myc lymphoma and induced differentiation in APL. Genetic codepletion of Hdac1 with Hdac2 was pro-apoptotic in Eµ-Myc lymphoma in vitro and in vivo and was phenocopied by the HDAC1/2-specific agent RGFP233. This study demonstrates the importance of HDAC3 for the proliferation of leukemia and lymphoma cells, suggesting that HDAC3-selective inhibitors could prove useful for the treatment of hematological malignancies. Moreover, our results demonstrate that codepletion of Hdac1 with Hdac2 mediates a robust pro-apoptotic response. Our integrated genetic and pharmacological approach provides important insights into the individual or combinations of HDACs that could be prioritized for targeting in a range of hematological malignancies.

Molecular Mechanism of the Cell Death Induced by the Histone Deacetylase Pan Inhibitor LBH589 (Panobinostat) in Wilms Tumor Cells

Background

Wilms tumor (WT) is an embryonic kidney cancer, for which histone acetylation might be a therapeutic target. LBH589, a novel targeted agent, suppresses histone deacetylases in many tumors. This study investigated the antitumor activity of LBH589 in SK-NEP-1 and G401 cells.

Methods

SK-NEP-1 and G401 cell growth was assessed by CCK-8 and in nude mice experiments. Annexin V/propidium iodide staining followed by flow cytometry detected apoptosis in cell culture. Gene expressions of LBH589-treated tumor cells were analyzed using an Arraystar Human LncRNA Array. The Multi Experiment View cluster software analyzed the expression data. Differentially expressed genes from the cluster analyses were imported into the Ingenuity Pathway Analysis tool.

Results

LBH589 inhibited cell proliferation of SK-NEP-1 and G401 cells in a dose-dependent manner. Annexin V, TUNEL and Hochest 33342 staining analysis showed that LBH589-treated cells showed more apoptotic features compared with the control. LBH589 treatment inhibited the growth of SK-NEP-1 xenograft tumors in nude mice. Arraystar Human LncRNA Array analysis of genes and lncRNAs regulated by LBH589 identified 6653 mRNAs and 8135 lncRNAs in LBH589-treated SK-NEP-1 cells. The most enriched gene ontology terms were those involved in nucleosome assembly. KEGG pathway analysis identified cell cycle proteins, including CCNA2, CCNB2, CCND1, CCND2, CDK4, CDKN1B and HDAC2, etc. Ingenuity Pathway Analysis identified important upstream molecules: HIST2H3C, HIST1H4A, HIST1A, HIST1C, HIST1D, histone H1, histone H3, RPRM, HSP70 and MYC.

Conclusions

LBH589 treatment caused apoptosis and inhibition of cell proliferation of SK-NEP-1and G401 cells. LBH589 had a significant effect and few side effects on SK-NEP-1 xenograft tumors. Expression profiling, and GO, KEGG and IPA analyses identified new targets and a new “network” of genes responding to LBH589 treatment in SK-NEP-1 cells. RPRM, HSP70 and MYC may be important regulators during LBH589 treatment. Our results provide new clues to the proapoptotic mechanism of LBH589.