MDM4/HIPK2/p53 cytoplasmic assembly uncovers coordinated repression of molecules with anti-apoptotic activity during early DNA damage response

Twenty years of Gendicine® rAd-p53 cancer gene therapy: The first-in-class human cancer gene therapy in the era of personalized oncology

Genetic mutations in TP53 contribute to human malignancies through various means. To date, there have been a variety of therapeutic strategies targeting p53, including gene therapy to restore normal p53 function, mutant p53 rescue, inhibiting the MDM2-p53 interaction, p53-based vaccines, and a number of other approaches. This review focuses on the functions of TP53 and discusses the aberrant roles of mutant p53 in various types of cancer. Recombinant human p53 adenovirus, trademarked as Gendicine, which is the first anti-tumor gene therapy drug, has made tremendous progress in cancer gene therapy. We herein discuss the biological mechanisms by which Gendicine exerts its effects and describe the clinical responses reported in clinical trials. Notably, the clinical studies suggest that the combination of Gendicine with chemotherapy and/or radiotherapy may produce more pronounced efficacy in slowing tumor growth and progression than gene therapy/chemotherapy alone. Finally, we summarize the methods of administration of recombinant human p53 adenovirus for different cancer types to provide a reference for future clinical trials.

MDMX in Cancer: A Partner of p53 and a p53-Independent Effector

The p53 tumor suppressor protein plays an important role in physiological and pathological processes. MDM2 and its homolog MDMX are the most important negative regulators of p53. Many studies have shown that MDMX promotes the growth of cancer cells by influencing the regulation of the downstream target gene of tumor suppressor p53. Studies have found that inhibiting the MDMX-p53 interaction can effectively restore the tumor suppressor activity of p53. MDMX has growth-promoting activities without p53 or in the presence of mutant p53. Therefore, it is extremely important to study the function of MDMX in tumorigenesis, progression and prognosis. This article mainly reviews the current research progress and mechanism on MDMX function, summarizes known MDMX inhibitors and provides new ideas for the development of more specific and effective MDMX inhibitors for cancer treatment.

Comparative miRNA expression profile analysis of porcine ovarian follicles: new insights into the initiation mechanism of follicular atresia

Follicular atresia occurs in every stage of ovarian development, which is relevant to female fertility. In the past decade, increasing studies have confirmed that miRNAs, a class of short non-coding RNAs, play an important role in follicular atresia by post-transcription regulation of their target genes. However, the function of miRNAs on follicular atresia initiation is unknown. In the present study, high-throughput small RNA sequencing was performed to analyze differential miRNA expression profiles between healthy (HF) follicles and early atretic (EAF) follicles. A total of 237 conserved miRNA were detected, and the miR-143 is the highest expressed in follicles. Meanwhile, we also found wide sequence variations (isomiRs) in porcine ovarian miRNA, including in 5'un-translation region, core seed sequences and 3'untranslation region. Furthermore, we identified 22 differentially expressed miRNAs in EAF groups compared to HF group, of which 3 miRNAs were upregulated, as well as 19 miRNAs were downregulated, and then the RT-PCR was performed to validate these profiles. The target genes of these differentially expressed miRNAs were predicted by using miRwalk, miRDB, and Targetscan database, respectively. Moreover, the gene ontology and KEGG pathway enrichment established that the regulating functions and signaling pathways of these miRNAs contribute to follicular atresia initiation and cell fate. In conclusion, this study provides new insights into the changes of miRNAs in early atretic follicles to demonstrate their molecular regulation in ovarian follicular atretic initiation.

Gene expression profiling of RIP2-knockdown in HD11 macrophages - elucidation of potential pathways (gene network) when challenged with avian pathogenic E.coli (APEC)

BACKGROUND

Receptor interacting serine/threonine kinase 2 (RIP2), ubiquitous in many tissue/cell types, is the key regulator of immune and inflammatory responses for many diseases, including avian pathogenic E. coli (APEC), which causes a wide variety of localized or systemic infections. However, the molecular mechanisms by which RIP2 drives its transcriptional program to affect immune and inflammatory response upon APEC infection remains poorly understood.

RESULTS

In this study, RNA-seq and bioinformatics analyses were used to detect gene expression and new direct/indirect RIP2 targets in the treatments of wild type HD11 cells (WT), RIP2 knockdown cells (shRIP2), APEC stimulation cells (APEC), and RIP2 knockdown cells combined with APEC infection (shRIP2 + APEC). The results revealed that a total of 4691 and 2605 differentially expressed genes (DEGs) were screened in shRIP2 + APEC vs. APEC and shRIP2 vs. WT, respectively. Functional annotation analysis showed that apoptosis, MAPK, p53, Toll-like receptor, and Nod-like receptor signaling pathways were involved in APEC-induced RIP2 knockdown HD11 cells. By analyzing the enriched pathway and gene networks, we identified that several DEGs, including HSP90AB1, BID, and CASP9 were targeted by RIP2 upon APEC infection.

CONCLUSION

As a whole, this study can not only provide data support for constructing gene networks of RIP2 knockdown with APEC challenge but also provide new ideas for improving the immune and inflammatory response.

Homeodomain Interacting Protein Kinase 2-Modified Rat Spinal Astrocytes Affect Neurofunctional Recovery After Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) is regarded as an acute neurological disorder, and astrocytes play a role in the progression of SCI.

OBJECTIVE

Herein, we investigated the roles of homeodomain-interacting protein kinase 2 (HIPK2)- modified rat spinal astrocytes in neurofunctional recovery after SCI.

METHODS

Rat spinal astrocytes were cultured, isolated, and then identified through microscopic observation and immunofluorescence staining. Astrocytes were infected with the adenovirus vector overexpressing HIPK2 for modification, and proliferation and apoptosis of astrocytes were examined using Cell Counting Kit-8 method and flow cytometry. SCI rat models were established and treated with astrocytes or HIPK2-modified astrocytes. Subsequently, rat motor ability was analyzed via the Basso-Beattie-Bresnahan (BBB) scoring and inclined-plane test, and the damage to spinal cord tissues and neuronal survival were observed via Hematoxylin-eosin staining and Nissl staining. The levels of HIPK2, brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and nuclear factor erythroid 2- related transcription factor 2 (Nrf2)/antioxidant response element (ARE) pathway-related proteins were detected.

RESULTS

Rat spinal astrocytes were harvested successfully. HIPK2 overexpression accelerated the proliferation and repressed the apoptosis of rat spinal astrocytes. Rat spinal astrocytes treatment increased BBB points and the maximum angle at which SCI rats remained stable, ameliorated damage to spinal cord tissues, increased the number of neurons, and attenuated neural damage and inflammation, while the treatment of HIPK2-modified rat spinal astrocytes imparted more pronounced effects to the neurofunctional recovery of SCI rats. Meanwhile, HIPK2-modified rat spinal astrocytes further activated the Nrf2/ARE pathway.

CONCLUSION

HIPK2-modified rat spinal astrocytes facilitated neurofunctional recovery and activated the Nrf2/ARE pathway after SCI.

HIPK2 cooperates with KRAS signaling and associates with colorectal cancer progression

HIPK2 is an evolutionary conserved kinase that has gained attention as a fine tuner of multiple signaling pathways, among which those commonly altered in colorectal cancer (CRC). The aim of this study was to evaluate the relationship of HIPK2 expression with progression markers and mutational pattern and gain insights into the contribution of HIPK2 activity in CRC. We evaluated a retrospective cohort of CRC samples by immunohistochemistry for HIPK2 expression and by NGS for the detection of mutations of cancer associated genes. We show that the percentage of HIPK2 positive cells increases with tumor progression, significantly correlates with TNM staging and associates with a worse outcome. In addition, we observed that high HIPK2 expression significantly associates with KRAS mutations but not with other cancer related genes. Functional characterization of the link between HIPK2 and KRAS show that activation of the RAS pathway either due to KRAS mutation or via upstream receptor stimulation, increases HIPK2 expression at the protein level. Of note, HIPK2 physically participates in the active RAS complex while HIPK2 depletion impairs ERK phosphorylation and the growth of tumors derived from KRAS mutated CRC cells. Overall, this study identifies HIPK2 as a prognostic biomarker candidate in CRC patients and underscores a previously unknown functional link between HIPK2 and the KRAS signaling pathway. Implications: Our data indicate HIPK2 as a new player in the complex picture of the KRAS signaling network, providing rationales for future clinical studies and new treatment strategies for KRAS mutated CRC.

Targeting Post-Translational Regulation of p53 in Colorectal Cancer by Exploiting Vulnerabilities in the p53-MDM2 Axis

The role played by the key tumor suppressor gene p53 and the implications of p53 mutations for the development and progression of neoplasia continue to expand. This review focuses on colorectal cancer and the regulators of p53 expression and activity identified over the past decade. These newly recognized regulatory mechanisms include (1) direct regulation of mouse double minute 2 homolog (MDM2), an E3 ubiquitin-protein ligase; (2) modulation of the MDM2-p53 interaction; (3) MDM2-independent p53 degradation; and (4) inhibition of p53 nuclear translocation. We positioned these regulatory mechanisms in the context of p53 missense mutations, which not only evade canonical p53 degradation machinery but also exhibit gain-of-function phenotypes that enhance tumor survival and metastasis. Lastly, we discuss current and potential therapeutic strategies directed against p53 mutant-bearing tumors.

Exercise downregulates HIPK2 and HIPK2 inhibition protects against myocardial infarction

Background

Exercise can protect myocardial infarction (MI) and downregulate cardiac Homeodomain-Interacting Protein Kinase 2 (HIPK2). However, the role of HIPK2 in MI is unclear.

Methods

HIPK2^–/– mice and miR-222^–/– rats, HIPK2 inhibitor (PKI1H) and adeno-associated virus serotype 9 (AAV9) carrying miR-222 were applied in the study. Animals were subjected to running, swimming, acute MI or post-MI remodeling. HIPK2 inhibition and P53 activator were used in neonatal rat cardiomyocytes (NRCMs) and human embryonic stem cell-derived cardiomyocytes (hESC-CMs) subjected to oxygen glucose deprivation/reperfusion (OGD/R). Serum miR-222 levels were analyzed in healthy people and MI patients that were survival or readmitted to the hospital and/or died.

Findings

Cardiac HIPK2 protein levels were reduced by exercise while increased in MI. In vitro, HIPK2 suppression by lentiviral vectors or inhibitor prevented apoptosis induced by OGD/R in NRCMs and hESC-CMs. HIPK2 inhibitor-treated mice and HIPK2^–/– mice reduced infarct size after acute MI, and preserved cardiac function in MI remodeling. Mechanistically, protective effect against apoptosis by HIPK2 suppression was reversed by P53 activators. Furthermore, increasing levels of miR-222, targeting HIPK2, protected post-MI cardiac dysfunction, whereas cardiac dysfunction post-MI was aggravated in miR-222^–/– rats. Moreover, serum miR-222 levels were significantly reduced in MI patients, as well as in MI patients that were readmitted to the hospital and/or died compared to those not.

Interpretation

Exercise-induced HIPK2 suppression attenuates cardiomyocytes apoptosis and protects MI by decreasing P-P53. Inhibition of HIPK2 represents a potential novel therapeutic intervention for MI.

Funding

This work was supported by the grants from National Key Research and Development Project (2018YFE0113500 to JJ Xiao), National Natural Science Foundation of China (82020108002, 81722008, and 81911540486 to JJ Xiao, 81400647 to MJ Xu, 81800265 to YJ Liang), Innovation Program of Shanghai Municipal Education Commission (2017-01-07-00-09-E00042 to JJ Xiao), the grant from Science and Technology Commission of Shanghai Municipality (18410722200 and 17010500100 to JJ Xiao), the “Dawn” Program of Shanghai Education Commission (19SG34 to JJ Xiao), Shanghai Sailing Program (21YF1413200 to QL Zhou). JS is supported by Horizon2020 ERC-2016-COG EVICARE (725229).

PRCC reduces the sensitivity of cancer cells to DNA damage by inhibiting JNK and ATM/ATR pathways and results in a poor prognosis in hepatocellular carcinoma

Background and aim

The proline rich mitotic checkpoint control factor (PRCC) is involved in the splicing process of pre-mRNA. This study aims to elucidate PRCC molecular function, regulatory mechanism and diagnostic value in hepatocellular carcinoma (HCC).

Methods

The tissue microarray and serum samples from HCC patients were used to investigate the clinical value of PRCC. The biological function and molecular mechanism of PRCC were demonstrated by cell biology, biochemical and animal experiments. The relationship between PRCC and intratumoral heterogeneity (ITH) was analyzed by bioinformatics.

Results

PRCC was highly expressed in HCC tissues and related to the poor prognosis of HCC patients, its contents were elevated in the preoperative sera of HCC patients. PRCC exhibited high application potential as a substitute or adjuvant of alpha-fetoprotein (AFP) for clinical diagnosis of HCC. It had no significant effect on the proliferation of cancer cells, but could inhibit spheroid formation and metastasis of HCC cells in vitro and in vivo. The high ectopic expression of PRCC made cancer cells insensitive to DNA damage, and enhanced the heterogeneity of HCC cells by inhibiting the JNK/ATM/ATR/ATF2 axis. The HCC patients with high PRCC expression had high ITH, which corresponded to a short overall survival in patients.

Conclusions

PRCC has high application potential as a substitute or adjuvant of AFP for clinical diagnosis of HCC. The high ectopic expression of PRCC not only caused HCC cells to resist to cell death induced by DNA damage, but also endowed cancer cells with numerous DNA mutations to become increasingly heterogeneous, finally leading to a poor prognosis in HCC patients. These data suggested PRCC could be a promising therapeutic target in HCC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00699-x.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

Functional characterization of HIC, a P2Y1 agonist, as a p53 stabilizer for prostate cancer cell death induction

Background: (1-(2-hydroxy-5-nitrophenyl)(4-hydroxyphenyl)methyl)indoline-4-carbonitrile (HIC), an agonist of the P2Y1 receptor (P2Y1R), induces cell death in prostate cancer cells. However, the molecular mechanism behind the inhibition of HIC in prostate cancer remains elusive. Methods & results: Here, to outline the inhibitory role of HIC on prostate cancer cells, PC-3 and DU145 cell lines were treated with the respective IC₅₀ concentrations, which reduced cell proliferation, adherence properties and spheroid formation. HIC was able to arrest the cell cycle at G1/S phase and also induced apoptosis and DNA damage, validated by gene expression profiling. HIC inhibited the prostate cancer cells' migration and invasion, revealing its antimetastatic ability. P2Y1R-targeted HIC affects p53, MAPK and NF-κB protein expression, thereby improving the p53 stabilization essential for G1/S arrest and cell death. Conclusion: These findings provide an insight on the potential use of HIC, which remains the mainstay treatment for prostate cancer.

Role of Sex in the Therapeutic Targeting of p53 Circuitry

Sex profoundly affects cancer incidence and susceptibility to therapy, with sex hormones highly contributing to this disparity. Various studies and omics data suggest a relationship between sex and the oncosuppressor p53 circuitry, including its regulators MDM2 and MDM4. Association of this network with genetic variation underlies sex-related altered cancer risk, age of onset, and cancer sensitivity to therapy. Moreover, sex-related factors, mainly estrogenic hormones, can affect the levels and/or function of the p53 network both in hormone-dependent and independent cancer. Despite this evidence, preclinical and clinical studies aimed to evaluate p53 targeted therapy rarely consider sex and related factors. This review summarizes the studies reporting the relationship between sex and the p53 circuitry, including its associated regulators, MDM2 and MDM4, with particular emphasis on estrogenic hormones. Moreover, we reviewed the evaluation of sex/hormone in preclinical studies and clinical trials employing p53-target therapies, and discuss how patients’ sex and hormonal status could impact these therapeutic approaches.

A Novel Ruthenium(II) Complex With Lapachol Induces G2/M Phase Arrest Through Aurora-B Kinase Down-Regulation and ROS-Mediated Apoptosis in Human Prostate Adenocarcinoma Cells

Lapachol is a well-studied natural product that has been receiving great interest due to its anticancer properties that target oxidative stress. In the present work, two novel lapachol-containing ruthenium(II) complexes [Ru(Lap)(dppm)(bipy)]PF6 (1) and [Ru(Lap)(dppm)(phen)]PF6 (2) [Lap = lapachol, dppm = 1,1'-bis(diphosphino)methane, bipy = 2,2'-bipyridine, phen = 1,10-phenantroline] were synthesized, fully characterized, and investigated for their cellular and molecular responses on cancer cell lines. We found that both complexes exhibited a potent cytotoxic effect in a panel of cancer cell lines in monolayer cultures, as well as in a 3D model of multicellular spheroids formed from DU-145 human prostate adenocarcinoma cells. Furthermore, the complex (2) suppressed the colony formation, induced G2/M-phase arrest, and downregulated Aurora-B. The mechanism studies suggest that complex (2) stimulate the overproduction of reactive oxygen species (ROS) and triggers caspase-dependent apoptosis as a result of changes in expression of several genes related to cell proliferation and caspase-3 and -9 activation. Interestingly, we found that N-acetyl-L-cysteine, a ROS scavenger, suppressed the generation of intracellular ROS induced by complex (2), and decreased its cytotoxicity, indicating that ROS-mediated DNA damage leads the DU-145 cells into apoptosis. Overall, we highlighted that coordination of lapachol to phosphinic ruthenium(II) compounds considerably improves the antiproliferative activities of resulting complexes granting attractive selectivity to human prostate adenocarcinoma cells. The DNA damage response to ROS seems to be involved in the induction of caspase-mediated cell death that plays an important role in the complexes' cytotoxicity. Upon further investigations, this novel class of lapachol-containing ruthenium(II) complexes might indicate promising chemotherapeutic agents for prostate cancer therapy.

Tenacissoside G synergistically potentiates inhibitory effects of 5-fluorouracil to human colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most malignant tumors worldwide with poor prognosis and low survival rate. Since the clinical efficacy of the commonly used 5-fluorouracil (5-FU) based chemotherapy in CRC patients is limited because of its intolerable adverse effects, there is an urgent need to explore agents that can enhance the anti-cancer activity of 5-FU, reduce adverse effects and prevent resistance.

PURPOSE

This study aims to investigate Tenacissoside G (TG)'s synergistic potentiation with 5-FU in inhibitory activity to colorectal cancer cells.

METHODS

The anti-proliferation effect of TG on 5 colorectal cancer cell lines was assessed by CCK-8 assay. The isobologram analysis and combination index methods were used to detect the synergistic effect of TG and 5-FU by the CompuSyn software using the T.C. Chou Method. The effects of TG/5-FU combination on cell cycle distribution and apoptosis induction were detected by flow cytometry. DNA damage degrees of cells treated with TG, 5-FU and their combination were evaluated by the alkaline comet assay. Protein expression regulated by the TG/5-FU combination was investigated by western blotting. Furthermore, a xenograft mouse model was established to investigate the synergistic anti-tumor effect in vivo.

RESULTS

In this work, we observed a dose-dependent growth inhibitory activity and cell cycle arrest induction of TG, a monomeric substance originated from Marsdenia tenacissima (Roxb.) Wight et Arn, in colorectal cancer cells. It was found that TG potentiated the anticancer effects of 5-FU with a synergism for the first time. And the co-treatment effects were also validated by in vivo experiments. The underlying mechanisms involved in the synergistic effects were probably included: (1) increased activation of caspase cascade; (2) enhancement of DNA damage degree and (3) induction of p53 phosphorylation at Serine 46.

CONCLUSION

TG potentiated 5-FU's inhibitory activity to human colorectal cancer through arresting cell cycle progression and inducing p53-mediated apoptosis, which may present a novel strategy in CRC therapies and contribute to the optimizing clinical application of 5-FU.

Inhibition of the mTOR pathway and reprogramming of protein synthesis by MDM4 reduce ovarian cancer metastatic properties

Epithelial ovarian cancer (EOC) is a highly heterogeneous disease with a high death rate mainly due to the metastatic spread. The expression of MDM4, a well-known p53-inhibitor, is positively associated with chemotherapy response and overall survival (OS) in EOC. However, the basis of this association remains elusive. We show that in vivo MDM4 reduces intraperitoneal dissemination of EOC cells, independently of p53 and an immune-competent background. By 2D and 3D assays, MDM4 impairs the early steps of the metastatic process. A 3D-bioprinting system, ad hoc developed by co-culturing EOC spheroids and endothelial cells, showed reduced dissemination and intravasation into vessel-like structures of MDM4-expressing cells. Consistent with these data, high MDM4 levels protect mice from ovarian cancer-related death and, importantly, correlate with increased 15 y OS probability in large data set analysis of 1656 patients. Proteomic analysis of EOC 3D-spheroids revealed decreased protein synthesis and mTOR signaling, upon MDM4 expression. Accordingly, MDM4 does not further inhibit cell migration when its activity towards mTOR is blocked by genetic or pharmacological approaches. Importantly, high levels of MDM4 reduced the efficacy of mTOR inhibitors in constraining cell migration. Overall, these data demonstrate that MDM4 impairs EOC metastatic process by inhibiting mTOR activity and suggest the usefulness of MDM4 assessment for the tailored application of mTOR-targeted therapy.

CircRNA-016901 silencing attenuates irradiation-induced injury in bone mesenchymal stem cells via regulating the miR-1249-5p/HIPK2 axis

Currently, bone marrow transplantation remains the basic treatment for various hematological tumors and irradiation is one of the most important pretreatment methods. However, irradiation pretreatment may result in damage to bone mesenchymal stem cells (BMSCs). The present study aimed to investigate the effect of circular RNA-016901 (circ-016901) on the injury of irradiation-induced BMSCs and the underlying mechanism. The expression levels of circ-016901, microRNA-1249-5p (miR-1249-5p) and homeodomain interacting protein kinase 2 (HIPK2) in irradiation-induced mouse BMSCs at various irradiation doses were detected via reverse transcription-quantitative PCR (RT-qPCR). The effect of circ-016901 on cell proliferation was examined using Cell Counting Kit-8 assays following silencing or overexpression of circ-016901. Cell apoptosis was detected by flow cytometry and caspase-3/7 activity. The expression of autophagy-related markers, including Beclin-1 and LC3-II/I, was detected at the mRNA and protein levels by RT-qPCR and western blotting, respectively. Irradiation treatment upregulated the expression of circ-016901 and HIPK2 and downregulated miR-1249-5p expression. The expression levels of LC3-II/I and Beclin-1 in BMSCs were downregulated in a dose-dependent manner. Silencing of circ-016901 promoted proliferation of irradiation-induced BMSCs and attenuated irradiation-induced apoptosis. Moreover, silencing of circ-016901 elevated the expressions of LC3-II/I and Beclin-1 in irradiation-induced BMSCs. Similar results were obtained with miR-1249-5p overexpression and HIPK2 silencing. These results demonstrated that circ-016901 silencing attenuated injury in irradiation-induced mouse BMSCs by regulating the miR-1249-5p/HIPK2 axis, providing a novel target for future research on the mechanism of radiation resistance in BMSCs.

Nanoparticle-complexed antimiRs for inhibiting tumor growth and metastasis in prostate carcinoma and melanoma

Background

MiRNAs act as negative regulators of gene expression through target mRNA degradation or inhibition of its translation. In cancer, several miRNAs are upregulated and play crucial roles in tumorigenesis, making the inhibition of these oncomiRs an interesting therapeutic approach. This can be achieved by directly complementary single-stranded anti-miRNA oligonucleotides (antimiRs). A major bottleneck in antimiR therapy, however, is their efficient delivery. The nanoparticle formation with polyethylenimine (PEI) may be particularly promising, based on the PEI’s ability to electrostatically interact with oligonucleotides. This leads to their protection and supports delivery. In the present study, we explore for the first time PEI for antimiR formulation and delivery. We use the branched low molecular weight PEI F25-LMW for the complexation of different antimiRs, and analyse tumor- and metastasis-inhibitory effects of PEI/antimiR complexes in different tumor models.

Results

In prostate carcinoma, transfection of antimiRs against miR-375 and miR-141 leads to tumor cell inhibition in 2D- and 3D-models. More importantly, an in vivo tumor therapy study in prostate carcinoma xenografts reveals anti-tumor effects of the PEI/antimiR complexes. In advanced melanoma and metastasis, we identify by a microRNA screen miR-150 as a particularly relevant oncomiR candidate, and validate this result in vitro and in vivo. Again, the systemic application of PEI/antimiR complexes inhibiting this miRNA, or the previously described antimiR-638, leads to profound tumor growth inhibition. These effects are associated with the upregulation of direct miRNA target genes. In a melanoma metastasis mouse model, anti-metastatic effects of PEI/antimiR treatment are observed as well.

Conclusions

We thus describe PEI-based complexes as efficient platform for antimiR therapy, as determined in two different tumor entities using in vivo models of tumor growth or metastasis. Our study also highlights the therapeutic relevance of miR-375, miR-141, miR-150 and miR-638 as target miRNAs for antimiR-mediated inhibition.

Targeting MDMX for Cancer Therapy: Rationale, Strategies, and Challenges

The oncogene MDMX, also known as MDM4 is a critical negative regulator of the tumor suppressor p53 and has been implicated in the initiation and progression of human cancers. Increasing evidence indicates that MDMX is often amplified and highly expressed in human cancers, promotes cancer cell growth, and inhibits apoptosis by dampening p53-mediated transcription of its target genes. Inhibiting MDMX-p53 interaction has been found to be effective for restoring the tumor suppressor activity of p53. Therefore, MDMX is becoming one of the most promising molecular targets for developing anticancer therapeutics. In the present review, we mainly focus on the current MDMX-targeting strategies and known MDMX inhibitors, as well as their mechanisms of action and in vitro and in vivo anticancer activities. We also propose other potential targeting strategies for developing more specific and effective MDMX inhibitors for cancer therapy.

An Alternative Splice Variant of HIPK2 with Intron Retention Contributes to Cytokinesis

HIPK2 is a DYRK-like kinase involved in cellular stress response pathways, development, and cell division. Two alternative splice variants of HIPK2, HIPK2-FL and HIPK2-Δe8, have been previously identified as having different protein stability but similar functional activity in the stress response. Here, we describe one additional HIPK2 splice variant with a distinct subcellular distribution and functional activity in cytokinesis. This novel splice variant lacks the last two exons and retains intron13 with a stop codon after 89 bp of the intron, generating a short isoform, HIPK2-S, that is detectable by 2D Western blots. RT-PCR analyses of tissue arrays and tumor samples show that HIPK2-FL and HIPK2-S are expressed in normal human tissues in a tissue-dependent manner and differentially expressed in human colorectal and pancreatic cancers. Gain- and loss-of-function experiments showed that in contrast to HIPK2-FL, HIPK2-S has a diffuse, non-speckled distribution and is not involved in the DNA damage response. Rather, we found that HIPK2-S, but not HIPK2-FL, localizes at the intercellular bridge, where it phosphorylates histone H2B and spastin, both required for faithful cell division. Altogether, these data show that distinct human HIPK2 splice variants are involved in distinct HIPK2-regulated functions like stress response and cytokinesis.

Effect of p53 activation through targeting MDM2/MDM4 heterodimer on T regulatory and effector cells in the peripheral blood of Type 1 diabetes patients

Various immunotherapies for the treatment of type 1 diabetes are currently under investigation. Some of these aim to rescue the remaining beta cells from autoimmune attack caused by the disease. Among the strategies employed, p53 has been envisaged as a possible target for immunomodulation. We studied the possible effect of p53 activation on Treg subsets and Treg/Teff balance in type 1 diabetes patients' PBMC. Upon p53 activation, we observed an increase in CD8+ Treg and activated CD8+ Teff whilst CD8+ Teff cells significantly decreased in healthy PBMC when stimulated with anti-CD3/CD28. No effect was detected on percentages of CD4+ Treg, while a reduction was seen in CD4+ Teff cells and an increase in activated CD4+ Teff cells. In patients' PBMC, upon p53 activation followed by 6 days of anti-CD3/CD28 stimulation, CD8+ Treg and activated CD8+ Teff were increased while CD8+ Teff were decreased. No differences were detected in the CD4+ counterparts. CD8+ Teff PD1+, CD8+ Teff PD1low were increased upon p53 activation in type 1 diabetics compared to controls while CD8+ Teff PD1high were increased in both groups. The same increased percentages were detected for CD4+ counterparts. CD4+ Treg PD1high cells were decreased in diabetics upon p53 activation at day 6 of anti-CD3/CD28 stimulation. In conclusion, a Teff dysregulation is observed upon p53 activation suggesting that molecules promoting p53 cannot be used for therapy in type 1 diabetics.

Estrogens Counteract Platinum-Chemosensitivity by Modifying the Subcellular Localization of MDM4

Estrogen activity towards cancer-related pathways can impact therapeutic intervention. Recent omics data suggest possible crosstalk between estrogens/gender and MDM4, a key regulator of p53. Since MDM4 can either promote cell transformation or enhance DNA damage-sensitivity, we analysed in vivo impact of estrogens on both MDM4 activities. In Mdm4 transgenic mouse, Mdm4 accelerates the formation of fibrosarcoma and increases tumor sensitivity to cisplatin as well, thus confirming in vivo Mdm4 dual mode of action. Noteworthy, Mdm4 enhances chemo- and radio-sensitivity in male but not in female animals, whereas its tumor-promoting activity is not affected by mouse gender. Combination therapy of transgenic females with cisplatin and fulvestrant, a selective estrogen receptor degrader, was able to recover tumor cisplatin-sensitivity, demonstrating the relevance of estrogens in the observed sexual dimorphism. Molecularly, estrogen receptor-α alters intracellular localization of MDM4 by increasing its nuclear fraction correlated to decreased cell death, in a p53-independent manner. Importantly, MDM4 nuclear localization and intra-tumor estrogen availability correlate with decreased platinum-sensitivity and apoptosis and predicts poor disease-free survival in high-grade serous ovarian carcinoma. These data demonstrate estrogen ability to modulate chemo-sensitivity of MDM4-expressing tumors and to impinge on intracellular trafficking. They support potential usefulness of combination therapy involving anti-estrogenic drugs.

The long and the short of it: the MDM4 tail so far

The mouse double minute 4 (MDM4) is emerging from the shadow of its more famous relative MDM2 and is starting to steal the limelight, largely due to its therapeutic possibilities. MDM4 is a vital regulator of the tumor suppressor p53. It restricts p53 transcriptional activity and also, at least in development, facilitates MDM2's E3 ligase activity toward p53. These functions of MDM4 are critical for normal cell function and a proper response to stress. Their importance for proper cell maintenance and proliferation identifies them as a risk for deregulation associated with the uncontrolled growth of cancer. MDM4 tails are vital for its function, where its N-terminus transactivation domain engages p53 and its C-terminus RING domain binds to MDM2. In this review, we highlight recently identified cellular functions of MDM4 and survey emerging therapies directed to correcting its dysregulation in disease.

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.

Role of Xeroderma Pigmentosum Group D in Cell Cycle and Apoptosis in Cutaneous Squamous Cell Carcinoma A431 Cells

BACKGROUND Cutaneous squamous cell carcinoma (cSCC) is the second most widespread cancer in humans and its incidence is rising. Novel therapy with better efficacy is needed for clinical treatment of cSCC. Many studies have shown the importance of DNA repair pathways during the development of cancer. A key nucleotide excision repair (NER) protein, xeroderma pigmentosum group D (XPD), is responsible for the excision of a large variety of bulky DNA lesions. MATERIAL AND METHODS To explore the role of XPD in A431 cells, we overexpressed XPD in A431 cells and performed MTT assay, flow cytometry, and Western blot analysis to examine cell proliferation, cell apoptosis, and genes expression. RESULTS We found that the overexpression of XPD suppressed cell viability, induced cell cycle arrest at G1 phase, and promoted cell apoptosis. Additionally, XPD blocked the expression of c-myc, cdc25A, and cdk2, and improved the levels of HIPK2 and p53. CONCLUSIONS These results provide new evidence to reveal the role of XPD in cSCC A431 cells and suggest that XPD may serve as an anti-oncogene during cSCC development.

Apoptosis as anticancer mechanism: function and dysfunction of its modulators and targeted therapeutic strategies

Apoptosis is a form of programmed cell death that results in the orderly and efficient removal of damaged cells, such as those resulting from DNA damage or during development. Apoptosis can be triggered by signals from within the cell, such as genotoxic stress, or by extrinsic signals, such as the binding of ligands to cell surface death receptors. Deregulation in apoptotic cell death machinery is an hallmark of cancer. Apoptosis alteration is responsible not only for tumor development and progression but also for tumor resistance to therapies. Most anticancer drugs currently used in clinical oncology exploit the intact apoptotic signaling pathways to trigger cancer cell death. Thus, defects in the death pathways may result in drug resistance so limiting the efficacy of therapies. Therefore, a better understanding of the apoptotic cell death signaling pathways may improve the efficacy of cancer therapy and bypass resistance. This review will highlight the role of the fundamental regulators of apoptosis and how their deregulation, including activation of anti-apoptotic factors (i.e., Bcl-2, Bcl-xL, etc) or inactivation of pro-apoptotic factors (i.e., p53 pathway) ends up in cancer cell resistance to therapies. In addition, therapeutic strategies aimed at modulating apoptotic activity are briefly discussed.

Otub1 stabilizes MDMX and promotes its proapoptotic function at the mitochondria

Otub1 regulates p53 stability and activity via non-canonical inhibition of UbcH5, the MDM2 cognate ubiquitin-conjugating enzyme (E2). However, whether Otub1 regulates MDMX stability and activity is not clear. Here we report that Otub1 also suppresses MDM2-mediated MDMX ubiquitination in cells and in vitro, independently of its deubiquitinating enzyme activity. Consequently, overexpression of Otub1 markedly stabilized MDMX and increased its levels, whereas knockdown of Otub1 reduced the levels of MDMX. Interestingly, MDMX induced by Otub1 can localize to mitochondria in addition to the cytosol, enhance p53 phosphorylation at S46 (p53S46P) and promote mitochondria-mediated apoptotic pathway. Knockdown of MDMX reduced Otub1-induced p53S46P, which was shown to be critical for p53's mitochondrial function and apoptotic activity. Furthermore, Otub1 promotes UV-irradiation-induced p53S46P and apoptosis, which can be significantly inhibited by MDMX depletion. Together, these results suggest that Otub1 stabilizes MDMX and promotes p53S46P and mitochondria-mediated apoptosis, providing an alternative mechanism of Otub1's role in apoptosis.

MDM4 actively restrains cytoplasmic mTORC1 by sensing nutrient availability

BACKGROUND

Many tumor-related factors have shown the ability to affect metabolic pathways by paving the way for cancer-specific metabolic features. Here, we investigate the regulation of mTORC1 by MDM4, a p53-inhibitor with oncogenic or anti-survival activities depending on cell growth conditions.

METHOD

MDM4-mTOR relationship was analysed through experiments of overexpression or silencing of endogenous proteins in cell culture and using purified proteins in vitro. Data were further confirmed in vivo using a transgenic mouse model overexpressing MDM4. Additionally, the Cancer Genome Atlas (TCGA) database (N = 356) was adopted to analyze the correlation between MDM4 and mTOR levels and 3D cultures were used to analyse the p53-independent activity of MDM4.

RESULTS

Following nutrient deprivation, MDM4 impairs mTORC1 activity by binding and inhibiting the kinase mTOR, and contributing to maintain the cytosolic inactive pool of mTORC1. This function is independent of p53. Inhibition of mTORC1 by MDM4 results in reduced phosphorylation of the mTOR downstream target p70S6K1 both in vitro and in vivo in a MDM4-transgenic mouse. Consistently, MDM4 reduces cell size and proliferation, two features controlled by p70S6K1, and, importantly, inhibits mTORC1-mediated mammosphere formation. Noteworthy, MDM4 transcript levels are significantly reduced in breast tumors characterized by high mTOR levels.

CONCLUSION

Overall, these data identify MDM4 as a nutrient-sensor able to inhibit mTORC1 and highlight its metabolism-related tumor-suppressing function.

The Double Role of p53 in Cancer and Autoimmunity and Its Potential as Therapeutic Target

p53 is a sequence-specific short-lived transcription factor expressed at low concentrations in various tissues while it is upregulated in damaged, tumoral or inflamed tissue. In normally proliferating cells, p53 protein levels and function are tightly controlled by main regulators, i.e., MDM2 (mouse double minute 2) and MDM4 proteins. p53 plays an important role due to its ability to mediate tumor suppression. In addition to its importance as a tumor suppressor, p53 coordinates diverse cellular responses to stress and damage and plays an emerging role in various physiological processes, including fertility, cell metabolism, mitochondrial respiration, autophagy, cell adhesion, stem cell maintenance and development. Interestingly, it has been recently implicated in the suppression of autoimmune and inflammatory diseases in both mice and humans. In this review based on current knowledge on the functional properties of p53 and its regulatory pathways, we discuss the potential utility of p53 reactivation from a therapeutic perspective in oncology and chronic inflammatory disorders leading to autoimmunity.

MDM2-MDM4 molecular interaction investigated by atomic force spectroscopy and surface plasmon resonance

Murine double minute 2 (MDM2) and 4 (MDM4) are known as the main negative regulators of p53, a tumor suppressor. They are able to form heterodimers that are much more effective in the downregulation of p53. Therefore, the MDM2-MDM4 complex could be a target for promising therapeutic restoration of p53 function. To this aim, a deeper understanding of the molecular mechanisms underlining the heterodimerization is needed. The kinetic and thermodynamic characterization of the MDM2-MDM4 complex was performed with two complementary approaches: atomic force spectroscopy and surface plasmon resonance. Both techniques revealed an equilibrium dissociation constant (KD ) in the micromolar range for the MDM2-MDM4 heterodimer, similar to related complexes involved in the p53 network. Furthermore, the MDM2-MDM4 complex is characterized by a relatively high free energy, through a single energy barrier, and by a lifetime in the order of tens of seconds. New insights into the MDM2-MDM4 interaction could be highly important for developing innovative anticancer drugs focused on p53 reactivation.

MDMX (MDM4), a Promising Target for p53 Reactivation Therapy and Beyond

The MDMX protein was identified as a p53-interacting protein with a strong similarity to MDM2. Like Mdm2, Mdmx expression is essential for curbing p53 activity during embryonic development, indicating nonredundant functions of Mdmx and Mdm2. There is now a large body of evidence indicating that cancers frequently up-regulate MDMX expression as a means to dampen p53 tumor-suppressor function. Importantly, MDMX also shows p53-independent oncogenic functions. These data make MDMX an attractive therapeutic target for cancer therapy. Here, we summarize the mechanisms used by cancer cells to increase MDMX expression and promising pharmacological strategies to target MDMX in cancer-in particular, the recent findings that antisense oligonucleotides (ASOs) can be used to efficiently modulate MDMX messenger RNA (mRNA) splicing.

Investigation of the Effects of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) on Apoptosis and Cell Cycle in a Zebrafish (Danio rerio) Liver Cell Line

This study aimed to explore the effects of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) on apoptosis and cell cycle in a zebrafish (Danio rerio) liver cell line (ZFL). Treatment groups included a control group, PFOA-IC₅₀, PFOA-IC₈₀, PFOS-IC₅₀ and PFOS-IC₈₀ groups. IC₅₀ and IC₈₀ concentrations were identified by cellular modeling and MTT assays. mRNA levels of p53, Bcl-2, Bax, Caspase-3 and NF-κB p65 were detected by qPCR. Cell apoptosis and cell cycle were detected by flow cytometry and the protein levels of p53, Bcl-2, Bax, Caspase-3 and NF-κB p65 were determined by western blotting. Both PFOA and PFOS inhibited the growth of zebrafish liver cells, and the inhibition rate of PFOS was higher than that of PFOA. Bcl-2 expression levels in the four groups were significantly higher than the control group and Bcl-2 increased significantly in the PFOA-IC₈₀ group. However, the expression levels of Bax in the four treatment groups were higher than the control group. The percentage of cell apoptosis increased significantly with the treatment of PFOA and PFOS (p < 0.05). Cell cycle and cell proliferation were blocked in both the PFOA-IC₈₀ and PFOS-IC₈₀ groups, indicating that PFOA-IC₈₀ and PFOS-IC₅₀ enhanced apoptosis in ZFL cells.

Novel insights about the MDM2/MDM4 heterodimer

MDM2 (mouse double minute 2 homolog) and MDM4 (double minute 4 human homolog, also known as MDMX) inhibit the activity of tumor protein p53 (TP53, best known as p53) through their heterodimerization. New evidence indicates that under stress conditions the heterodimer is modified, leading to different activities of the single molecules. In particular, following lethal DNA damage, MDM2 and MDM4 dissociate and MDM4 promotes the stabilization of homeodomain-interacting protein kinase 2 (HIPK2) and the phosphorylation of p53, resulting in transcriptional repression of antiapoptotic targets of p53/HIPK2.