Integrative Chinese-Western medicine strategy to overcome docetaxel resistance in prostate cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese Medicines (TCMs) have emerged as a promising complementary therapy in the management of prostate cancer (PCa), particularly in addressing resistance to Docetaxel (DTX) chemotherapy.

AIM OF THE REVIEW

This review aims to elucidate the mechanisms underlying the development of resistance to DTX in PCa and explore the innovative approach of integrating TCMs in PCa treatment to overcome this resistance. Key areas of investigation include alterations in microtubule proteins, androgen receptor and androgen receptor splice variant 7, ERG rearrangement, drug efflux mechanisms, cancer stem cells, centrosome clustering, upregulation of the PI3K/AKT signaling pathway, enhanced DNA damage repair capability, and the involvement of neurotrophin receptor 1/protein kinase C.

MATERIALS AND METHODS

With "Prostate cancer", "Docetaxel", "Docetaxel resistance", "Natural compounds", "Traditional Chinese medicine", "Traditional Chinese medicine compound", "Medicinal plants" as the main keywords, PubMed, Web of Science and other online search engines were used for literature retrieval.

RESULTS

Our findings underscore the intricate interplay of molecular alterations that collectively contribute to the resistance of PCa cells to DTX. Moreover, we highlight the potential of TCMs as a promising complementary therapy, showcasing their ability to counteract DTX resistance and enhance therapeutic efficacy.

CONCLUSION

The integration of TCMs in PCa treatment emerges as an innovative approach with significant potential to overcome DTX resistance. This review not only provides insights into the mechanisms of resistance but also presents new prospects for improving the clinical outcomes of patients with PCa undergoing DTX therapy. The comprehensive understanding of these mechanisms lays the foundation for future research and the development of more effective therapeutic interventions.

Semilicoisoflavone B induces oral cancer cell apoptosis by targeting claspin and ATR-Chk1 signaling pathways

The prevalence of oral squamous cell carcinoma (OSCC) is increasing worldwide mainly due to poor oral hygiene and unrestricted lifestyle. Advanced-stage OSCC is associated with poor prognosis and a 5-year survival rate of only 30%-50%. The present study was designed to investigate the anticancer effect and mode of action of Glycyrrhiza-derived semilicoisoflavone B (SFB) in 5-fluorourasil (5FU)-resistant human OSCC cell lines. The study findings revealed that SFB significantly reduces OSCC cell viability and colony formation ability by arresting cell cycle at the G2/M and S phases and reducing the expressions of key cell cycle regulators including cyclin A, cyclin B, CDC2, and CDK2. The compound caused a significant induction in the percentage of nuclear condensation and apoptotic cells in OSCC. Regarding pro-apoptotic mode of action, SFB was found to increase Fas-associated death domain and death receptor 5 expressions and reduce decoy receptor 2 expression, indicating involvement of extrinsic pathway. Moreover, SFB was found to increase pro-apoptotic Bim expression and reduce anti-apoptotic Bcl-2 and Bcl-xL expressions, indicating involvement of intrinsic pathway. Moreover, SFB-mediated induction in cleaved caspases 3, 8, and 9 and cleaved poly(ADP-ribose) polymerase confirmed the induction of caspase-mediated apoptotic pathways. Regarding upstream signaling pathway, SFB was found to reduce extracellular signal regulated kinase 1/2 (ERK) phosphorylation to execute its pro-apoptotic activity. The Human Apoptotic Array findings revealed that SFB suppresses claspin expression, which in turn caused reduced phosphorylation of ATR, checkpoint kinase 1 (Chk1), Wee1, and CDC25C, indicating disruption of ATR-Chk1 signaling pathway by SFB. Taken together, these findings indicate that SFB acts as a potent anticancer compound against 5FU-resistant OSCC by modulating mitogen-activated protein kinase (MAPK) and ATR-Chk1 signaling pathways.

How CLSPN could demystify its prognostic value and potential molecular mechanism for hepatocellular carcinoma: A crosstalk study

BACKGROUND & AIMS

CLSPN, a critical component of the S-phase checkpoint in response to DNA replication stress, has been implicated in the pathogenesis of multiple tumor types. The rising incidence of hepatocellular carcinoma (HCC) poses a significant challenge to global public health. Despite this, the specific functions of CLSPN in the development of HCC remain poorly understood.

METHODS

We systematically evaluated the expression of CLSPN, prognosis and immune infiltration in patients with HCC and identified a competing endogenous RNA (ceRNA) network by using public database. The RT-qPCR, western blot, CCK8, transwell, flow cytometry, animal experiments, proteasome inhibition experiment, Co-IP assay and mass spectrometry were applied to explore its biological functions, post-transcriptional modifications and potential molecular mechanisms of CLSPN in HCC.

RESULTS

We verified the expression of CLSPN, and its high expression is an independent prognostic factor in HCC. The expression of CLSPN is also associated with the immune microenvironment of HCC. CLSPN silencing inhibited the proliferation, migration, invasion and cell cycle progression of HCC cells. We established a PSMA3-AS1/hsa-miR-101-3p/CLSPN regulator axis in HCC. CLSPN was influenced by ubiquitination and was involved in the Wnt/β-catenin pathway to regulate HCC progression.

CONCLUSIONS

It was the first time to comprehensively discover and identify the expression, prognosis, immunotherapy, RNAs regulator, posttranscriptional modification, and molecular mechanisms of CLSPN in HCC. These novel insights have the potential to expedite the development of personalized treatment strategies and translational medicine approaches for HCC patients.

CLSPN actives Wnt/β-catenin signaling to facilitate glycolysis and cell proliferation in oral squamous cell carcinoma

OBJECTIVE

Oral squamous cell carcinoma (OSCC) is a common malignancy with a poor prognosis. This study aimed to determine the influence and underlying mechanisms of CLSPN on OSCC.

METHODS

CLSPN expression was tested using quantitative real-time polymerase chain reaction, immunohistochemistry, and western blotting. Flow cytometry, cell counting kit, and colony formation assays were performed to determine OSCC cell apoptosis, viability, and proliferation, respectively. In OSCC cells, the extracellular acidification rate (ECAR), oxygen consumption rate (OCR), glucose uptake, and lactate production were determined using the corresponding kits. Changes in the protein levels of HK2, PKM2, LDHA, Wnt3a, and β-catenin were assessed using western blotting.

RESULTS

CLSPN expression was increased in OSCC tissues. Overexpression of CLSPN in HSC-2 cells promoted cell proliferation, increased the levels of ECAR, glucose uptake, and lactate production, and increased the protein levels of HK2, PKM2, LDHA, Wnt3a, and β-catenin, but inhibited OCR levels and apoptosis. The knockdown of CLSPN in CAL27 cells resulted in the opposite results. Moreover, the effects of CLSPN overexpression on glycolysis and OSCC cell proliferation were reversed by Wnt3a knockdown. In vivo, knockdown of CLSPN restrained tumor growth, glycolysis, and the activation of Wnt/β-catenin signaling.

CONCLUSION

CLSPN promoted glycolysis and OSCC cell proliferation, and reduced apoptosis, which was achieved by the activation of Wnt/β-catenin signaling pathway.

The Interaction between CLSPN Gene Polymorphisms and Alcohol Consumption Contributes to Oral Cancer Progression

Most disease single nucleotide polymorphisms (SNPs) are regulatory and approximately half of heritability is occupied by the top 1% of genes, with the gene-level structure varying with the number of variants associated with the most common alleles. Cancer occurrence and progression are significantly affected by Claspin (CLSPN) gene polymorphism present in the population, which alters the expression, function, and regulation of the gene. CLSPN genotypes are associated with oral cancer, but the literature on this association is limited. As a result, the goal of this study is to investigate the correlation between CLSPN genotypes and oral cancers' development. This study will explore the presence of four CLSPN SNPs including rs12058760, rs16822339, rs535638 and rs7520495 gene polymorphisms, and analyze the expression of these genes in 304 cancer-free controls and 402 oral squamous cell carcinoma (OSCC) cases. Attempts have been made to obtain insight into the role of CLSPN gene polymorphisms in oral cancer through the analysis of this study. We demonstrated that the OSCC risk of individuals with four CLSPN SNPs relative to the wild type did not differ significantly from that of the wild type when the polymorphisms are analyzed according to individual habits. We further studied the mechanism by which CLSPN polymorphisms affect the progression of clinicopathological features in OSCC patients. The results of the degree of cell differentiation showed that compared with patients of rs7520495 SNP carrying the CC genotype, the incidence of poor cell differentiation in patients carrying the CC + GG genotype was higher (AOR: 1.998-fold; 95% CI, 1.127-3.545; p = 0.018). In particular, patients with the G genotype of rs7520495 had increased poor cell differentiation compared with patients with the C genotype (AOR: 4.736-fold; 95% CI, 1.306-17.178; p = 0.018), especially in the drinking group. On the basis of our analysis of the Cancer Genome Atlas dataset, we found that higher CLSPN levels were associated with poorer cell differentiation in oral cancers. In this study, we provide the first evidence showing that CLSPN SNPs contribute to oral cancer. Whether or not rs7520495 can be used as a confirmatory factor in the future is uncertain, but it seems likely that it can be used as an important factor in predicting recurrence, response to treatment and medication toxicity to patients with oral cancer.

Celastrol suppresses human pancreatic cancer via m6A-YTHDF3-mediated downregulation of Claspin and Bcl-2

BACKGROUND

Celastrol has been revealed to exhibit anticancer pharmacological activity, however, the molecular mechanisms of celastrol involved in pancreatic cancer remain to be further elucidated. The present study was to illustrate whether celastrol suppresses pancreatic cancer through modulating RNA m6A modification.

METHODS

Effect of celastrol treatment on the malignant phenotypes of pancreatic cancer cells was evaluated by CCK-8 assay, EdU assay, colony formation assay, flow cytometry analysis and subcutaneous xenograft experiments. RNA sequencing (RNA-seq) analysis was carried out to analyze the genes differentially expressed in celastrol-treated pancreatic cancer cells. RT-qPCR, Western blotting and immunohistochemistry were employed to evaluate the expression of the indicated genes. RNA dot blot and quantification of total RNA m6A modification assays, MeRIP-qPCR assay, RIP-qPCR assay, RNA stability and protein stability assays were applied to evaluate the regulatory mechanism of celastrol treatment in pancreatic cancer cells.

RESULTS

We demonstrated that celastrol suppressed cell proliferation and induced cell cycle arrest and apoptosis of pancreatic cancer cells in vitro, and decreased tumor growth in vivo. Specifically, Bcl-2, Claspin, METTL3 and YTHDF3 were identified as the potential targets of celastrol treatment in pancreatic cancer cells. Moreover, our results indicated that celastrol treatment downregulated METTL3 and decreased m6A levels of Claspin and Bcl-2 mRNA, leading to the degradation of Claspin and Bcl-2 mRNA in pancreatic cancer cells. Furthermore, we revealed that celastrol treatment downregulated Claspin and Bcl-2, at least in part, in an m6A-YTHDF3-mediated manner in pancreatic cancer cells.

CONCLUSION

Our study highlighted a novel mechanism underlying celastrol-induced cellular proliferation inhibition and apoptosis in pancreatic cancer cells via m6A-YTHDF3-mediated downregulation of Claspin and Bcl-2.

A nine-gene signature as prognostic biomarker in gastric cancer by bioinformatics analysis

PURPOSE

The prognosis of advanced gastric cancer (GC) remains poor. It is urgent and necessary to find suitable prognostic markers. miR-619-5p is highly expressed in GC. However, the value of miR-619-5p and its target genes as prognostic biomarkers of GC is unclear.

METHODS

RT-PCR was performed to verify the expression of miR-619-5p in GC cell lines and their exosomes. Western blotting and transmission electron microscope were used to identify exosomes. The target genes of miR-619-5p were predicted by RNA22 and TargetScan. The differentially expressed genes (DEGs) and prognosis-related genes (PRGs) were obtained using The Cancer Genome Atlas (TCGA) database. The DAVID database was used to analyse pathway enrichment and functional annotation of common target genes. The STRING database and Cytoscape software were used to screen key genes and visualize their functional modules. The survival analysis was conducted using TCGA and Kaplan-Meier Plotter (KMP) databases. Finally, a prognostic model was constructed on the foundation of the key genes to assess the reliability of the screening process.

RESULTS

The expression of miR-619-5p in GC cells and their exosomes was proved to be significantly higher than that in normal cell lines. There are 129 common target genes involved in 3 pathways and 28 functional annotations. Finally, nine key target genes of GC (BRCA1, RAD51, KIF11, ERCC6L, BRIP1, TIMELESS, CDC25A, CLSPN and NCAPG2) were identified, and a prognostic model was successfully constructed with a good predictive ability.

CONCLUSIONS

The model of 9-gene signature could effectively predict the prognosis of GC, and have great potential to be novel prognostic factors and therapeutic targets for patients with GC.

Pyrenebutyrate Pt(IV) Complexes with Nanomolar Anticancer Activity

Research on platinum-based anticancer drugs continuously strives to develop new non-classical platinum complexes. Pt(IV) prodrugs are the most promising, and their activation-by-reduction mechanism of action is being explored as a prospect for higher selectivity and efficiency. Herein, we present the anticancer potency and chemical reactivity of Pt(IV) complexes formed by linking pyrene butyric acid with cisplatin. The results from cytotoxicity screening on 10 types of cancer cell lines and non-malignant cells (HEK-293) indicated IC50 values as low as 50-70 nM for the monosubstituted Pt(IV) complex against leukemia cell lines (HL-60 and SKW3) and a cisplatin-resistant derivative (HL-60/CDDP). Interestingly, the bis-substituted complex is virtually non-toxic to both healthy and cancerous cells of adherent types. Nevertheless, it shows high cytotoxicity against multidrug-resistant derivatives HL-60/CDDP and HL-60/Dox. The reactivity of the complexes with biological reductants was monitored by the NMR method. Furthermore, the platinum uptake by the treated cells was examined on two types of cellular cultures: adherent and suspension growing, and proteome profiling was conducted to track expression changes of key apoptosis-related proteins in HL-60 cells. The general conclusion points to a possible cytoskeletal entrapment of the bulkier bis-pyrene complex that could be limiting its cytotoxicity to adherent cells, both cancerous and healthy ones.

Actionable loss of SLF2 drives B-cell lymphomagenesis and impairs the DNA damage response

The DNA damage response (DDR) acts as a barrier to malignant transformation and is often impaired during tumorigenesis. Exploiting the impaired DDR can be a promising therapeutic strategy; however, the mechanisms of inactivation and corresponding biomarkers are incompletely understood. Starting from an unbiased screening approach, we identified the SMC5-SMC6 Complex Localization Factor 2 (SLF2) as a regulator of the DDR and biomarker for a B-cell lymphoma (BCL) patient subgroup with an adverse prognosis. SLF2-deficiency leads to loss of DDR factors including Claspin (CLSPN) and consequently impairs CHK1 activation. In line with this mechanism, genetic deletion of Slf2 drives lymphomagenesis in vivo. Tumor cells lacking SLF2 are characterized by a high level of DNA damage, which leads to alterations of the post-translational SUMOylation pathway as a safeguard. The resulting co-dependency confers synthetic lethality to a clinically applicable SUMOylation inhibitor (SUMOi), and inhibitors of the DDR pathway act highly synergistic with SUMOi. Together, our results identify SLF2 as a DDR regulator and reveal co-targeting of the DDR and SUMOylation as a promising strategy for treating aggressive lymphoma.

Studying the DNA damage response pathway in hematopoietic canine cancer cell lines, a necessary step for finding targets to generate new therapies to treat cancer in dogs

Background

Dogs present a significant opportunity for studies in comparative oncology. However, the study of cancer biology phenomena in canine cells is currently limited by restricted availability of validated antibody reagents and techniques. Here, we provide an initial characterization of the expression and activity of key components of the DNA Damage Response (DDR) in a panel of hematopoietic canine cancer cell lines, with the use of commercially available antibody reagents.

Materials and methods

The techniques used for this validation analysis were western blot, qPCR, and DNA combing assay.

Results

Substantial variations in both the basal expression (ATR, Claspin, Chk1, and Rad51) and agonist-induced activation (p-Chk1) of DDR components were observed in canine cancer cell lines. The expression was stronger in the CLBL-1 (B-cell lymphoma) and CLB70 (B-cell chronic lymphocytic leukemia) cell lines than in the GL-1 (B-cell leukemia) cell line, but the biological significance of these differences requires further investigation. We also validated methodologies for quantifying DNA replication dynamics in hematopoietic canine cancer cell lines, and found that the GL-1 cell line presented a higher replication fork speed than the CLBL-1 cell line, but that both showed a tendency to replication fork asymmetry.

Conclusion

These findings will inform future studies on cancer biology, which will facilitate progress in developing novel anticancer therapies for canine patients. They can also provide new knowledge in human oncology.

Regulation of Human DNA Primase-Polymerase PrimPol

Transmission of genetic information depends on successful completion of DNA replication. Genomic DNA is subjected to damage on a daily basis. DNA lesions create obstacles for DNA polymerases and can lead to the replication blockage, formation of DNA breaks, cell cycle arrest, and apoptosis. Cells have evolutionary adapted to DNA damage by developing mechanisms allowing elimination of lesions prior to DNA replication (DNA repair) and helping to bypass lesions during DNA synthesis (DNA damage tolerance). The second group of mechanisms includes the restart of DNA synthesis at the sites of DNA damage by DNA primase-polymerase PrimPol. Human PrimPol was described in 2013. The properties and functions of this enzyme have been extensively studied in recent years, but very little is known about the regulation of PrimPol and association between the enzyme dysfunction and diseases. In this review, we described the mechanisms of human PrimPol regulation in the context of DNA replication, discussed in detail interactions of PrimPol with other proteins, and proposed possible pathways for the regulation of human PrimPol activity. The article also addresses the association of PrimPol dysfunction with human diseases.

Therapeutic inhibition of Bmi-1 ablates chemoresistant cancer stem cells in adenoid cystic carcinoma

OBJECTIVES

Adenoid Cystic Carcinomas (ACC) typically show modest responseto cytotoxic therapy. Cancer stem cells (CSC) have been implicated in chemoresistance and tumor relapse. However, their role in ACC remains unknown. The purpose of this work was to evaluate the impact of targeting ACC CSCs with Bmi-1 inhibitors on resistance to cytotoxic therapy and tumor relapse.

MATERIALS AND METHODS

Therapeutic efficacy of a small molecule inhibitor of Bmi-1 (PTC596; Unesbulin) and/or Cisplatin on ACC stemness was evaluated in immunodeficient mice harboring PDX ACC tumors (UM-PDX-HACC-5) and in human ACC cell-lines (UM-HACC-2A,-14) or low passage primary human ACC cells (UM-HACC-6). The effect of therapy on stemness was examined by salisphere assays, flow cytometry for ALDH activity and CD44 expression, and Western blots for Bmi-1 (self-renewal marker) and Oct4 (embryonic stem cell marker) expression.

RESULTS

Platinum-based agents (Cisplatin, Carboplatin) induced Bmi-1 and Oct4 expression, increased salisphere formation and the CSC fraction in vitro and in vivo. In contrast, PTC596 inhibited expression of Bmi-1, Oct4 and pro-survival proteins Mcl-1 and Claspin; decreased the number of salispheres, and the fraction of ACC CSCs in vitro. Silencing Claspin decreased salisphere formation and CSC fraction. Both, single agent PTC596 and PTC596/Cisplatin combination decreased the CSC fraction in PDX ACC tumors. Notably, short-term combination therapy (2 weeks) with PTC596/Cisplatin prevented tumor relapse for 150 days in a preclinical trial in mice.

CONCLUSION

Therapeutic inhibition of Bmi-1 ablates chemoresistant CSCs and prevents ACC tumor relapse. Collectively, these results suggest that ACC patients might benefit from Bmi-1-targeted therapies.

A multi-omics analysis reveals CLSPN is associated with prognosis, immune microenvironment and drug resistance in cancers

BACKGROUND

Immunotherapy is effective only in limited patients. It is urgent to discover a novel biomarker to predict immune cells infiltration status and immunotherapy response of different cancers. CLSPN has been reported to play a pivotal role in various biological processes. However, a comprehensive analysis of CLSPN in cancers has not been conducted.

METHODS

To show the whole picture of CLSPN in cancers, a pan-cancer analysis was conducted in 9125 tumor samples across 33 cancer types by integrating transcriptomic, epigenomic and pharmacogenomics data. Moreover, the role of CLSPN in cancer was validated by CCK-8, EDU, colony formation and flow cytometry in vitro and tumor cell derived xenograft model in vivo.

RESULTS

CLSPN expression was generally upregulated in most cancer types and was significantly associated with prognosis in different tumor samples. Moreover, elevated CLSPN expression was closely correlated with immune cells infiltration, TMB (tumor mutational burden), MSI (microsatellite instability), MMR (mismatch repair), DNA methylation and stemness score across 33 cancer types. Enrichment analysis of functional genes revealed that CLSPN participated in the regulation of numerous signaling pathways involved in cell cycle and inflammatory response. The expression of CLSPN in LUAD patients were further analyzed at the single-cell level. Knockdown CLSPN significantly inhibited cancer cell proliferation and cell cycle related cyclin-dependent kinase (CDK) family and Cyclin family expression in LUAD (lung adenocarcinoma) both in vitro and in vivo experiments. Finally, we conducted structure-based virtual screening by modelling the structure of CHK1 kinase domain and Claspin phosphopeptide complex. The top five hit compounds were screened and validated by molecular docking and Connectivity Map (CMap) analysis.

CONCLUSION

Our multi-omics analysis offers a systematic understanding of the roles of CLSPN in pan-cancer and provides a potential target for future cancer treatment.

Matrix stiffness induces an invasive-dormant subpopulation via cGAS-STING axis in oral cancer

OBJECTIVES

Dormancy is a crucial machinery for cancer cells to survive hostile microenvironment. It is considered as the major cause of post-treatment relapse and metastases. However, its regulatory mechanism in oral squamous cell carcinoma (OSCC) remains unclear. Here we sought to decipher the impacts of matrix stiffness on OSCC-cell dormancy.

MATERIALS AND METHODS

Clinicopathological relevance of matrix stiffness in OSCC was analyzed in a 127 patients' cohort. Impacts of stiffness-related mechanical stress (MS) on OSCC-cell behaviors were investigated in vitro and in vivo. Transcriptomic profiling of MS induced dormant cells were performed, following by mechanistic investigations on MS-induced dormancy. The functional relevance of cGAS in OSCC were analyzed through a bioinformatic approach.

RESULTS

Stiffened matrix correlated with poor survival and post-surgical recurrence in OSCC. Stiffness-related MS induces a dormant subpopulation in OSCC cells, which showed increased drug resistance, enhanced tumor repopulating ability, and an unexpected upregulation of epithelial-mesenchymal transition (EMT) and invasiveness. Mechanistically, MS caused DNA damage, resulted in activation of cGAS-STING signaling. Either blocking of cGAS or STING dramatically impeded the MS-induced production of this invasive-dormant subpopulation. Moreover, cGAS was found being central to the cell-cycle regulation and correlated with poor prognosis in OSCC.

DISCUSSION

We revealed a previously unsuspected role of cGAS-STING axis in mediating the induction of an invasive-dormant subpopulation in response to mechanical cues. Our findings indicated an adaptive machinery whereby tumor cells survive and escape from harsh microenvironment. Targeting this machinery may be a potential strategy for preventing post-therapeutic recurrence and lymphatic metastasis in OSCC.

Association of SNPs in the PAI1 Gene with Disease Recurrence and Clinical Outcome in Bladder Cancer

PURPOSE

Bladder cancer (BCa) is one of the most common cancer types worldwide and is characterized by a high rate of recurrence. In previous studies, we and others have described the functional influence of plasminogen activator inhibitor-1 (PAI1) in bladder cancer development. While polymorphisms in PAI1 have been associated with increased risk and worsened prognosis in some cancers, the mutational status of PAI1 in human bladder tumors has not been well defined.

METHODS

In this study, we evaluated the mutational status of PAI1 in a series of independent cohorts, comprised of a total of 660 subjects.

RESULTS

Sequencing analyses identified two clinically relevant 3' untranslated region (UTR) single nucleotide polymorphisms (SNPs) in PAI1 (rs7242; rs1050813). Somatic SNP rs7242 was present in human BCa cohorts (overall incidence of 72%; 62% in Caucasians and 72% in Asians). In contrast, the overall incidence of germline SNP rs1050813 was 18% (39% in Caucasians and 6% in Asians). Furthermore, Caucasian patients with at least one of the described SNPs had worse recurrence-free survival and overall survival (p = 0.03 and p = 0.03, respectively). In vitro functional studies demonstrated that SNP rs7242 increased the anti-apoptotic effect of PAI1, and SNP rs1050813 was related to a loss of contact inhibition associated with cellular proliferation when compared to wild type.

CONCLUSION

Further investigation of the prevalence and potential downstream influence of these SNPs in bladder cancer is warranted.

Molecular Aspects of Hypoxic Stress Effects in Chronic Ethanol Exposure of Neuronal Cells

Experimental models of a clinical, pathophysiological context are used to understand molecular mechanisms and develop novel therapies. Previous studies revealed better outcomes for spinal cord injury chronic ethanol-consuming patients. This study evaluated cellular and molecular changes in a model mimicking spinal cord injury (hypoxic stress induced by treatment with deferoxamine or cobalt chloride) in chronic ethanol-consuming patients (ethanol-exposed neural cultures (SK-N-SH)) in order to explain the clinical paradigm of better outcomes for spinal cord injury chronic ethanol-consuming patients. The results show that long-term ethanol exposure has a cytotoxic effect, inducing apoptosis. At 24 h after the induction of hypoxic stress (by deferoxamine or cobalt chloride treatments), reduced ROS in long-term ethanol-exposed SK-N-SH cells was observed, which might be due to an adaptation to stressful conditions. In addition, the HIF-1α protein level was increased after hypoxic treatment of long-term ethanol-exposed cells, inducing fluctuations in its target metabolic enzymes proportionally with treatment intensity. The wound healing assay demonstrated that the cells recovered after stress conditions, showing that the ethanol-exposed cells that passed the acute step had the same proliferation profile as the cells unexposed to ethanol. Deferoxamine-treated cells displayed higher proliferative activity than the control cells in the proliferation-migration assay, emphasizing the neuroprotective effect. Cells have overcome the critical point of the alcohol-induced traumatic impact and adapted to ethanol (a chronic phenomenon), sustaining the regeneration process. However, further experiments are needed to ensure recovery efficiency is more effective in chronic ethanol exposure.

Cisplatin resistance driver claspin is a target for immunotherapy in urothelial carcinoma

Bladder cancer is a major and fatal urological disease. Cisplatin is a key drug for the treatment of bladder cancer, especially in muscle-invasive cases. In most cases of bladder cancer, cisplatin is effective; however, resistance to cisplatin has a significant negative impact on prognosis. Thus, a treatment strategy for cisplatin-resistant bladder cancer is essential to improve the prognosis. In this study, we established a cisplatin-resistant (CR) bladder cancer cell line using an urothelial carcinoma cell lines (UM-UC-3 and J82). We screened for potential targets in CR cells and found that claspin (CLSPN) was overexpressed. CLSPN mRNA knockdown revealed that CLSPN had a role in cisplatin resistance in CR cells. In our previous study, we identified human leukocyte antigen (HLA)-A*02:01-restricted CLSPN peptide by HLA ligandome analysis. Thus, we generated a CLSPN peptide-specific cytotoxic T lymphocyte clone that recognized CR cells at a higher level than wild-type UM-UC-3 cells. These findings indicate that CLSPN is a driver of cisplatin resistance and CLSPN peptide-specific immunotherapy may be effective for cisplatin-resistant cases.

Up-regulation of the PI3K/AKT and RHO/RAC/PAK signalling pathways in CHK1 inhibitor resistant Eµ-Myc lymphoma cells

The development of resistance and the activation of bypass pathway signalling represents a major problem for the clinical application of protein kinase inhibitors. While investigating the effect of either a c-Rel deletion or RelAT505A phosphosite knockin on the Eµ-Myc mouse model of B-cell lymphoma, we discovered that both NF-κB subunit mutations resulted in CHK1 inhibitor resistance, arising from either loss or alteration of CHK1 activity, respectively. However, since Eµ-Myc lymphomas depend on CHK1 activity to cope with high levels of DNA replication stress and consequent genomic instability, it was not clear how these mutant NF-κB subunit lymphomas were able to survive. To understand these survival mechanisms and to identify potential compensatory bypass signalling pathways in these lymphomas, we applied a multi-omics strategy. With c-Rel-/- Eµ-Myc lymphomas we observed high levels of Phosphatidyl-inositol 3-kinase (PI3K) and AKT pathway activation. Moreover, treatment with the PI3K inhibitor Pictilisib (GDC-0941) selectively inhibited the growth of reimplanted c-Rel-/- and RelAT505A, but not wild type (WT) Eµ-Myc lymphomas. We also observed up-regulation of a RHO/RAC pathway gene expression signature in both Eµ-Myc NF-κB subunit mutation models. Further investigation demonstrated activation of the RHO/RAC effector p21-activated kinase (PAK) 2. Here, the PAK inhibitor, PF-3758309 successfully overcame resistance of RelAT505A but not WT lymphomas. These findings demonstrate that up-regulation of multiple bypass pathways occurs in CHK1 inhibitor resistant Eµ-Myc lymphomas. Consequently, drugs targeting these pathways could potentially be used as either second line or combinatorial therapies to aid the successful clinical application of CHK1 inhibitors.

Claspin haploinsufficiency leads to defects in fertility, hyperplasia and an increased oncogenic potential

Claspin is an adaptor protein required for ATR-dependent phosphorylation of CHK1 during S-phase following DNA replication stress. Claspin expression is highly variable in cancer, with low levels frequently correlating with poor patient survival. To learn more about the biological consequences of reduced Claspin expression and its effects on tumorigenesis, we investigated mice with a heterozygous knockout of the Clspn gene. Claspin haploinsufficiency resulted in reduced female fertility and a maternally inherited defect in oocyte meiosis I cell cycle progression. Furthermore, aged Clspn+/- mice developed spontaneous lymphoid hyperplasia and increased susceptibility to non-alcoholic fatty liver disease. Importantly, we demonstrate a tumour suppressor role for Claspin. Reduced Claspin levels result in increased liver damage and tumourigenesis in the DEN model of hepatocellular carcinoma. These data reveal that Clspn haploinsufficiency has widespread unanticipated biological effects and establishes the importance of Claspin as a regulatory node controlling tumorigenesis and multiple disease aetiologies.

Regulation of CHK1 inhibitor resistance by a c-Rel and USP1 dependent pathway

Previously, we discovered that deletion of c-Rel in the Eµ-Myc mouse model of lymphoma results in earlier onset of disease, a finding that contrasted with the expected function of this NF-κB subunit in B-cell malignancies. Here we report that Eµ-Myc/cRel-/- cells have an unexpected and major defect in the CHK1 pathway. Total and phospho proteomic analysis revealed that Eµ-Myc/cRel-/- lymphomas highly resemble wild-type (WT) Eµ-Myc lymphomas treated with an acute dose of the CHK1 inhibitor (CHK1i) CCT244747. Further analysis demonstrated that this is a consequence of Eµ-Myc/cRel-/- lymphomas having lost expression of CHK1 protein itself, an effect that also results in resistance to CCT244747 treatment in vivo. Similar down-regulation of CHK1 protein levels was also seen in CHK1i resistant U2OS osteosarcoma and Huh7 hepatocellular carcinoma cells. Further investigation revealed that the deubiquitinase USP1 regulates CHK1 proteolytic degradation and that its down-regulation in our model systems is responsible, at least in part, for these effects. We demonstrate that treating WT Eµ-Myc lymphoma cells with the USP1 inhibitor ML323 was highly effective at reducing tumour burden in vivo. Targeting USP1 activity may thus be an alternative therapeutic strategy in MYC-driven tumours.

Regulation of ATR-CHK1 signaling by ubiquitination of CLASPIN

DNA replication forks are frequently forced into stalling by persistent DNA aberrations generated from endogenous or exogenous insults. Stalled replication forks are catastrophic for genome integrity and cell survival if not immediately stabilized. The ataxia-telangiectasia and RAD3-related kinase (ATR)-CLASPIN-checkpoint kinase 1 (CHK1) signaling cascade is a pivotal mechanism that initiates cell-cycle checkpoints and stabilizes stalled replication forks, assuring the faithful duplication of genomic information before entry into mitosis. The timely recovery of checkpoints after stressors are resolved is also crucial for normal cell proliferation. The precise activation and inactivation of ATR-CHK1 signaling are usually efficiently regulated by turnover and the cellular re-localization of the adaptor protein CLASPIN. The ubiquitination-proteasome-mediated degradation of CLASPIN, driven by APC/CCDH1 and SCFβTrCP, results in a cell-cycle-dependent fluctuation pattern of CLASPIN levels, with peak levels seen in S/G2 phase when it functions in the DNA replisome or as an adaptor protein in ATR-CHK1 signaling under replication stress. Deubiquitination mediated by a series of ubiquitin-specific protease family proteins releases CLASPIN from proteasome-dependent destruction and activates the ATR-CHK1 checkpoint to overcome replication stress. Moreover, the non-proteolytic ubiquitination of CLASPIN also affects CHK1 activation by regulating CLASPIN localization. In this review, we discuss the functions of CLASPIN ubiquitination with specific linkage types in the regulation of the ATR-CHK1 signaling pathway. Research in this area is progressing at pace and provides promising chemotherapeutic targets.

Regulation of Claspin by the p38 stress-activated protein kinase protects cells from DNA damage

Stress-activated protein kinases (SAPKs) enhance survival in response to environmental changes. In yeast, the Hog1 SAPK and Mrc1, a protein required for DNA replication, define a safeguard mechanism that allows eukaryotic cells to prevent genomic instability upon stress during S-phase. Here we show that, in mammals, the p38 SAPK and Claspin-the functional homolog of Mrc1-protect cells from DNA damage upon osmostress during S-phase. We demonstrate that p38 phosphorylates Claspin and either the mutation of the p38-phosphorylation sites in Claspin or p38 inhibition suppresses the protective role of Claspin on DNA damage. In addition, wild-type Claspin but not the p38-unphosphorylatable mutant has a protective effect on cell survival in response to cisplatin treatment. These findings reveal a role of Claspin in response to chemotherapeutic drugs. Thus, this pathway protects S-phase integrity from different insults and it is conserved from yeast to mammals.

The bone marrow niche regulates redox and energy balance in MLL::AF9 leukemia stem cells

Eradicating leukemia requires a deep understanding of the interaction between leukemic cells and their protective microenvironment. The CXCL12/CXCR4 axis has been postulated as a critical pathway dictating leukemia stem cell (LSC) chemoresistance in AML due to its role in controlling cellular egress from the marrow. Nevertheless, the cellular source of CXCL12 in the acute myeloid leukemia (AML) microenvironment and the mechanism by which CXCL12 exerts its protective role in vivo remain unresolved. Here, we show that CXCL12 produced by Prx1+ mesenchymal cells but not by mature osteolineage cells provide the necessary cues for the maintenance of LSCs in the marrow of an MLL::AF9-induced AML model. Prx1+ cells promote survival of LSCs by modulating energy metabolism and the REDOX balance in LSCs. Deletion of Cxcl12 leads to the accumulation of reactive oxygen species and DNA damage in LSCs, impairing their ability to perpetuate leukemia in transplantation experiments, a defect that can be attenuated by antioxidant therapy. Importantly, our data suggest that this phenomenon appears to be conserved in human patients. Hence, we have identified Prx1+ mesenchymal cells as an integral part of the complex niche-AML metabolic intertwining, pointing towards CXCL12/CXCR4 as a target to eradicate parenchymal LSCs in AML.

Targeting Tumour-Associated Fibroblasts in Cancers

Tumours develop within complex tissue environments consisting of aberrant oncogenic cancer cells, diverse innate and adaptive immune cells, along with structural stromal cells, extracellular matrix and vascular networks, and many other cellular and non-cellular soluble constituents. Understanding the heterogeneity and the complex interplay between these cells remains a key barrier in treating tumours and cancers. The immune status of the pre-tumour and tumour milieu can dictate if the tumour microenvironment (TME) supports either a pro-malignancy or an anti-malignancy phenotype. Identification of the factors and cell types that regulate the dysfunction of the TME is crucial in order to understand and modulate the immune status of tumours. Among these cell types, tumour-associated fibroblasts are emerging as a major component of the TME that is often correlated with poor prognosis and therapy resistance, including immunotherapies. Thus, a deeper understanding of the complex roles of tumour-associated fibroblasts in regulating tumour immunity and cancer therapy could provide new insight into targeting the TME in various human cancers. In this review, we summarize recent studies investigating the role of immune and key stromal cells in regulating the immune status of the TME and discuss the therapeutic potential of targeting stromal cells, especially tumour-associated fibroblasts, within the TME as an adjuvant therapy to sensitize immunosuppressive tumours and prevent cancer progression, chemo-resistance and metastasis.

Essential role of CK2α for the interaction and stability of replication fork factors during DNA synthesis and activation of the S-phase checkpoint

The ataxia telangiectasia mutated and Rad3-related (ATR)-CHK1 pathway is the major signalling cascade activated in response to DNA replication stress. This pathway is associated with the core of the DNA replication machinery comprising CDC45, the replicative MCM2-7 hexamer, GINS (altogether forming the CMG complex), primase-polymerase (POLε, -α, and -δ) complex, and additional fork protection factors such as AND-1, CLASPIN (CLSPN), and TIMELESS/TIPIN. In this study, we report that functional protein kinase CK2α is critical for preserving replisome integrity and for mounting S-phase checkpoint signalling. We find that CDC45, CLSPN and MCM7 are novel CK2α interacting partners and these interactions are particularly important for maintenance of stable MCM7-CDC45, ATRIP-ATR-MCM7, and ATR-CLSPN protein complexes. Consistently, cells depleted of CK2α and treated with hydroxyurea display compromised replisome integrity, reduced chromatin binding of checkpoint mediator CLSPN, attenuated ATR-mediated S-phase checkpoint and delayed recovery of stalled forks. In further support of this, differential gene expression analysis by RNA-sequencing revealed that down-regulation of CK2α accompanies global shutdown of genes that are implicated in the S-phase checkpoint. These findings add to our understanding of the molecular mechanisms involved in DNA replication by showing that the protein kinase CK2α is essential for maintaining the stability of the replisome machinery and for optimizing ATR-CHK1 signalling activation upon replication stress.

Molecular determinants of the meiotic arrests in mammalian oocytes at different stages of maturation

Mammalian oocytes undergo two rounds of developmental arrest during maturation: at the diplotene of the first meiotic prophase and metaphase of the second meiosis. These arrests are strictly regulated by follicular cells temporally producing the secondary messengers, cAMP and cGMP, and other factors to regulate maturation promoting factor (composed of cyclin B1 and cyclin-dependent kinase 1) levels in the oocytes. Out of these normally appearing developmental arrests, permanent arrests may occur in the oocytes at germinal vesicle (GV), metaphase I (MI), or metaphase II (MII) stage. This issue may arise from absence or altered expression of the oocyte-related genes playing key roles in nuclear and cytoplasmic maturation. Additionally, the assisted reproductive technology (ART) applications such as ovarian stimulation and in vitro culture conditions both of which harbor various types of chemical agents may contribute to forming the permanent arrests. In this review, the molecular determinants of developmental and permanent arrests occurring in the mammalian oocytes are comprehensively evaluated in the light of current knowledge. As number of permanently arrested oocytes at different stages is increasing in ART centers, potential approaches for inducing permanent arrests to obtain competent oocytes are discussed.

Broad Transcriptomic Impact of Sorafenib and Its Relation to the Antitumoral Properties in Liver Cancer Cells

Simple Summary

Hepatocellular carcinoma (HCC) is the fourth most frequent cause of cancer-related mortality worldwide. While ablation, resection and orthotopic liver transplantation are indicated at an early stage of the disease, Sorafenib (Sfb) is the current most administrated first-line treatment for advanced HCC, even though its therapeutic benefit is limited due to the appearance of resistance. Deep knowledge on the molecular consequences of Sfb-treatment is essentially required for optimizing novel therapeutic strategies to improve the outcomes for patients with advanced HCC. In this study, we analyzed differential gene expression changes in two well characterized liver cancer cell lines upon a Sfb-treatment, demonstrating that both lines responded similarly to the treatment. Our results provide valuable information on the molecular action of Sfb on diverse cellular fundamental processes such as DNA repair, translation and proteostasis and identify rationalization issues that could provide a different therapeutic perspective to Sfb.

Abstract

Hepatocellular carcinoma (HCC) is one of the most frequent and essentially incurable cancers in its advanced stages. The tyrosine kinase inhibitor Sorafenib (Sfb) remains the globally accepted treatment for advanced HCC. However, the extent of its therapeutic benefit is limited. Sfb exerts antitumor activity through its cytotoxic, anti-proliferative and pro-apoptotic roles in HCC cells. To better understand the molecular mechanisms underlying these effects, we used RNA sequencing to generate comprehensive transcriptome profiles of HepG2 and SNU423, hepatoblastoma- (HB) and HCC-derived cell lines, respectively, following a Sfb treatment at a pharmacological dose. This resulted in similar alterations of gene expression in both cell lines. Genes functionally related to membrane trafficking, stress-responsible and unfolded protein responses, circadian clock and activation of apoptosis were predominantly upregulated, while genes involved in cell growth and cycle, DNA replication and repair, ribosome biogenesis, translation initiation and proteostasis were downregulated. Our results suggest that Sfb causes primary effects on cellular stress that lead to upregulation of selective responses to compensate for its negative effect and restore homeostasis. No significant differences were found specifically affecting each cell line, indicating the robustness of the Sfb mechanism of action despite the heterogeneity of liver cancer. We discuss our results on terms of providing rationalization for possible strategies to improve Sfb clinical outcomes.

TRIM21 suppresses CHK1 activation by preferentially targeting CLASPIN for K63-linked ubiquitination

Expression of the E3 ligase TRIM21 is increased in a broad spectrum of cancers; however, the functionally relevant molecular pathway targeted by TRIM21 overexpression remains largely unknown. Here, we show that TRIM21 directly interacts with and ubiquitinates CLASPIN, a mediator for ATR-dependent CHK1 activation. TRIM21-mediated K63-linked ubiquitination of CLASPIN counteracts the K6-linked ubiquitination of CLASPIN which is essential for its interaction with TIPIN and subsequent chromatin loading. We further show that overexpression of TRIM21, but not a TRIM21 catalytically inactive mutant, compromises CHK1 activation, leading to replication fork instability and tumorigenesis. Our findings demonstrate that TRIM21 suppresses CHK1 activation by preferentially targeting CLASPIN for K63-linked ubiquitination, providing a potential target for cancer therapy.

PNU-74654 Suppresses TNFR1/IKB Alpha/p65 Signaling and Induces Cell Death in Testicular Cancer

Testicular cancer (TC) is a rare malignancy worldwide and is the most common malignancy in males aged 15–44 years. The Wnt/β-catenin signaling pathway mediates numerous essential cellular functions and has potentially important effects on tumorigenesis and cancer progression. The search for drugs to inhibit this pathway has identified a small molecule, PNU-74654, as an inhibitor of the β-catenin/TCF4 interaction. We evaluated the therapeutic role of PNU-74654 in two TC cell lines, NCCIT and NTERA2, by measuring cell viability, cell cycle transition and cell death. Potential pathways were evaluated by protein arrays and Western blots. PNU-74654 decreased cell viability and induced apoptosis of TC cells, with significant increases in the sub G1, Hoechst-stained, Annexin V-PI-positive rates. PNU-74654 treatment of both TC cell lines inhibited the TNFR1/IKB alpha/p65 pathway and the execution phase of apoptosis. Our findings demonstrate that PNU-74654 can induce apoptosis in TC cells through mechanisms involving the execution phase of apoptosis and inhibition of TNFR1/IKB alpha/p65 signaling. Therefore, small molecules such as PNU-74654 may identify potential new treatment strategies for TC.

Hypoxic Incubation Conditions for Optimized Manufacture of Tenocyte-Based Active Pharmaceutical Ingredients of Homologous Standardized Transplant Products in Tendon Regenerative Medicine

Human fetal progenitor tenocytes (hFPT) produced in defined cell bank systems have recently been characterized and qualified as potential therapeutic cell sources in tendon regenerative medicine. In view of further developing the manufacture processes of such cell-based active pharmaceutical ingredients (API), the effects of hypoxic in vitro culture expansion on key cellular characteristics or process parameters were evaluated. To this end, multiple aspects were comparatively assessed in normoxic incubation (i.e., 5% CO₂ and 21% O₂, standard conditions) or in hypoxic incubation (i.e., 5% CO₂ and 2% O₂, optimized conditions). Experimentally investigated parameters and endpoints included cellular proliferation, cellular morphology and size distribution, cell surface marker panels, cell susceptibility toward adipogenic and osteogenic induction, while relative protein expression levels were analyzed by quantitative mass spectrometry. The results outlined conserved critical cellular characteristics (i.e., cell surface marker panels, cellular phenotype under chemical induction) and modified key cellular parameters (i.e., cell size distribution, endpoint cell yields, matrix protein contents) potentially procuring tangible benefits for next-generation cell manufacturing workflows. Specific proteomic analyses further shed some light on the cellular effects of hypoxia, potentially orienting further hFPT processing for cell-based, cell-free API manufacture. Overall, this study indicated that hypoxic incubation impacts specific hFPT key properties while preserving critical quality attributes (i.e., as compared to normoxic incubation), enabling efficient manufacture of tenocyte-based APIs for homologous standardized transplant products.

Wogonin Induces Cell Cycle Arrest and Apoptosis of Hepatocellular Carcinoma Cells by Activating Hippo Signalling

OBJECTIVE

The current study aimed to illustrate whether wogonin influences HCC cell cycle progression and apoptosis by regulating Hippo signaling. <P> Methods: The effects of wogonin on HCC cell viability, cell cycle progression and apoptosis were analyzed by utilizing CCK-8 and flow cytometry. RNA-seq was employed to analyze the expression profiles between wogonin-treated and control HCC cells, and the selected RNA-seq transcripts were validated by reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). Immunofluorescence staining was performed to detect the distribution of YAP/TAZ in the nucleus and cytoplasm in HCC cells. Western blotting and human apoptosis array were performed to examine the expression of the indicated genes. <P> Results: We demonstrated that wogonin induced cell cycle arrest and apoptosis of HCC cell lines SMMC7721 and HCCLM3. RNA-seq analysis showed enrichment in genes associated with cell cycle progression and apoptosis following incubation with wogonin in HCC cells, and the pathways analysis further identified that Hippo signaling pathways highly altered in wogonin-treated cells. Specifically, wogonin increased the phosphorylation of MOB1 and LATS1, promoted translocation of endogenous YAP and TAZ from the nucleus to the cytoplasm, and facilitated phosphorylation of YAP and TAZ. Notably, overexpression of YAP or TAZ partially abrogated the wogonin-mediated HCC cell cycle arrest and apoptosis, and reversed wogonin-mediated suppression of Claspin. <P> Conclusion: Wogonin induced HCC cell cycle arrest and apoptosis probably by activating MOB1-LATS1 signaling to inhibit the activation of YAP and TAZ, and then decrease the expression of Claspin, suggesting that the understanding of the molecular mechanisms underlying wogonin-induced cell cycle arrest and apoptosis may be useful in HCC therapeutics.

Targeting protein-protein interactions in the DNA damage response pathways for cancer chemotherapy

Cellular DNA damage response (DDR) is an extensive signaling network that orchestrates DNA damage recognition, repair and avoidance, cell cycle progression and cell death. DDR alteration is a hallmark of cancer, with the deficiency in one DDR capability often compensated by a dependency on alternative pathways endowing cancer cells with survival and growth advantage. Targeting these DDR pathways has provided multiple opportunities for the development of cancer therapies. Traditional drug discovery has mainly focused on catalytic inhibitors that block enzyme active sites, which limits the number of potential drug targets within the DDR pathways. This review article describes the emerging approach to the development of cancer therapeutics targeting essential protein-protein interactions (PPIs) in the DDR network. The overall strategy for the structure-based design of small molecule PPI inhibitors is discussed, followed by an overview of the major DNA damage sensing, DNA repair, and DNA damage tolerance pathways with a specific focus on PPI targets for anti-cancer drug design. The existing small molecule inhibitors of DDR PPIs are summarized that selectively kill cancer cells and/or sensitize cancers to front-line genotoxic therapies, and a range of new PPI targets are proposed that may lead to the development of novel chemotherapeutics.

Claspin Overexpression Promotes Tumor Progression and Predicts Poor Clinical Outcome in Prostate Cancer

Background: Claspin (CLSPN) expression is acknowledged as a poor clinical prognostic factor in various tumors. However, the clinical characteristics and biological functions of CLSPN in prostate cancer (PCa) are still to be clarified. The aim of our study was to evaluate the association of CLSPN expression during PCa progression and its potential role in prognosis. Methods: We analyzed mRNA expression of the CLSPN gene with various clinicopathological features using the Cancer Genome Atlas and GSE21032 dataset. Immunohistochemical assays were used to detect the protein expression levels of CLSPN in human PCa tissue microarrays. Furthermore, we characterized the role of CLSPN in PCa progression through in vitro experiments using a CLSPN knockout. Results: Immunohistochemistry and public datasets revealed that CLSPN expression was increased in PCa with: a high Gleason score; advanced pathological stage; and positive surgical margins. In addition, upregulation of CLSPN was correlated with shorter biochemical recurrence (BCR)-free survival and overall survival. After we knocked-out CLSPN in DU145 and LNCaP cells, the in vitro phenotypic results showed that the ability of the knockouts to proliferate, migrate, and invade was attenuated; but that apoptosis was promoted. Conclusions: Our data support an oncogenic role for CLSPN in PCa progression. Moreover, increased CLSPN expression was identified as an independent factor in predicting bCR-free survival and disease-free survival in PCa patients.

Overexpression of claspin promotes docetaxel resistance and is associated with prostate-specific antigen recurrence in prostate cancer

Although docetaxel (DTX) confers significant survival benefits in patients with castration‐resistant prostate cancer (CRPC), resistance to DTX inevitably occurs. Therefore, clarifying the mechanisms of DTX resistance may improve survival in patients with CRPC. Claspin plays a pivotal role in DNA replication stress and damage responses and is an essential regulator for the S‐phase checkpoint. CLSPN is an oncogenic gene that contributes to tumor proliferation in several human solid tumors. However, the clinical significance of claspin in prostate cancer (PCa) has not been examined. The present study aimed to elucidate the role of claspin and its relationship with DTX resistance in PCa. We immunohistochemically analyzed the expression of claspin in 89 PCa cases, of which 31 (35%) were positive for claspin. Claspin‐positive cases were associated with higher Gleason score, venous invasion, and perineural invasion. Kaplan–Meier analysis showed that high claspin expression was related to poor prostate‐specific antigen (PSA) relapse‐free prognosis. In a public database, high CLSPN expression was associated with poor PSA relapse‐free prognosis, Gleason score, T stage, lymph node metastasis, CRPC, and metastatic PCa. Claspin knockdown by siRNA decreased cell proliferation, upregulated DTX sensitivity, and suppressed the expression of Akt, Erk1/2, and CHK1 phosphorylation in DU145 and PC3 cell lines. Furthermore, claspin expression was much more upregulated in DTX‐resistant DU145 (DU145‐DR) than in parental DU145 cells. Claspin knockdown significantly upregulated the sensitivity to DTX in DU145‐DR cells. These results suggest that claspin plays an important role in PCa tumor progression and DTX resistance.

Daughter-strand gaps in DNA replication - substrates of lesion processing and initiators of distress signalling

Dealing with DNA lesions during genome replication is particularly challenging because damaged replication templates interfere with the progression of the replicative DNA polymerases and thereby endanger the stability of the replisome. A variety of mechanisms for the recovery of replication forks exist, but both bacteria and eukaryotic cells also have the option of continuing replication downstream of the lesion, leaving behind a daughter-strand gap in the newly synthesized DNA. In this review, we address the significance of these single-stranded DNA structures as sites of DNA damage sensing and processing at a distance from ongoing genome replication. We describe the factors controlling the emergence of daughter-strand gaps from stalled replication intermediates, the benefits and risks of their expansion and repair via translesion synthesis or recombination-mediated template switching, and the mechanisms by which they activate local as well as global replication stress signals. Our growing understanding of daughter-strand gaps not only identifies them as targets of fundamental genome maintenance mechanisms, but also suggests that proper control over their activities has important practical implications for treatment strategies and resistance mechanisms in cancer therapy.

Genotoxic stress response: What is the role of cytoplasmic mRNA fate?

Genotoxic stress leads to DNA damage which can be detrimental to the cell. A well-orchestrated cellular response is mounted to manage and repair the genotoxic stress-induced DNA damage. Our understanding of genotoxic stress response is derived mainly from studies focused on transcription, mRNA splicing, and protein turnover. Surprisingly not as much is understood about the role of mRNA translation and decay in genotoxic stress response. This is despite the fact that regulation of gene expression at the level of mRNA translation and decay plays a critical role in a myriad of cellular processes. This review aims to summarize some of the known findings of the role of mRNA translation and decay by focusing on two categories of examples. We discuss examples of mRNA whose fates are regulated in the cytoplasm and RNA-binding proteins that regulate mRNA fates in response to genotoxic stress.

SLFN11 Inactivation Induces Proteotoxic Stress and Sensitizes Cancer Cells to Ubiquitin Activating Enzyme Inhibitor TAK-243

Schlafen11 (SLFN11) inactivation occurs in approximately 50% of cancer cell lines and in a large fraction of patient tumor samples, which leads to chemoresistance. Therefore, new therapeutic approaches are needed to target SLFN11-deficient cancers. To that effect, we conducted a drug screen with the NCATS mechanistic drug library of 1,978 compounds in isogenic SLFN11-knockout (KO) and wild-type (WT) leukemia cell lines. Here we report that TAK-243, a first-in-class ubiquitin activating enzyme UBA1 inhibitor in clinical development, causes preferential cytotoxicity in SLFN11-KO cells; this effect is associated with claspin-mediated DNA replication inhibition by CHK1 independently of ATR. Additional analyses showed that SLFN11-KO cells exhibit consistently enhanced global protein ubiquitylation, endoplasmic reticulum (ER) stress, unfolded protein response (UPR), and protein aggregation. TAK-243 suppressed global protein ubiquitylation and activated the UPR transducers PERK, phosphorylated eIF2α, phosphorylated IRE1, and ATF6 more effectively in SLFN11-KO cells than in WT cells. Proteomic analysis using biotinylated mass spectrometry and RNAi screening also showed physical and functional interactions of SLFN11 with translation initiation complexes and protein folding machinery. These findings uncover a previously unknown function of SLFN11 as a regulator of protein quality control and attenuator of ER stress and UPR. Moreover, they suggest the potential value of TAK-243 in SLFN11-deficient tumors. SIGNIFICANCE: This study uncovers that SLFN11 deficiency induces proteotoxic stress and sensitizes cancer cells to TAK-243, suggesting that profiling SLFN11 status can serve as a therapeutic biomarker for cancer therapy.

Critical role of SMG7 in activation of the ATR-CHK1 axis in response to genotoxic stress

CHK1 is a crucial DNA damage checkpoint kinase and its activation, which requires ATR and RAD17, leads to inhibition of DNA replication and cell cycle progression. Recently, we reported that SMG7 stabilizes and activates p53 to induce G₁ arrest upon DNA damage; here we show that SMG7 plays a critical role in the activation of the ATR-CHK1 axis. Following genotoxic stress, SMG7-null cells exhibit deficient ATR signaling, indicated by the attenuated phosphorylation of CHK1 and RPA32, and importantly, unhindered DNA replication and fork progression. Through its 14-3-3 domain, SMG7 interacts directly with the Ser635-phosphorylated RAD17 and promotes chromatin retention of the 9-1-1 complex by the RAD17-RFC, an essential step to CHK1 activation. Furthermore, through maintenance of CHK1 activity, SMG7 controls G₂-M transition and facilitates orderly cell cycle progression during recovery from replication stress. Taken together, our data reveals SMG7 as an indispensable signaling component in the ATR-CHK1 pathway during genotoxic stress response.

Premalignant Oligodendrocyte Precursor Cells Stall in a Heterogeneous State of Replication Stress Prior to Gliomagenesis

Cancer evolves from premalignant clones that adopt unusual cell states to achieve transformation. We previously pinpointed the oligodendrocyte precursor cell (OPC) as a cell of origin for glioma, but the early changes of mutant OPCs during premalignancy remained unknown. Using mice engineered for inducible Nf1-Trp53 loss in OPCs, we acutely isolated labeled mutant OPCs by laser-capture microdissection, determined global gene-expression changes by bulk RNA sequencing, and compared with cell-state fluctuations at the single-cell level by stochastic profiling, which uses RNA-sequencing measurements from random pools of 10 mutant cells. At 12 days after Nf1-Trp53 deletion, bulk differences were mostly limited to mitotic hallmarks and genes for ribosome biosynthesis, and stochastic profiling revealed a spectrum of stem-progenitor (Axl, Aldh1a1), proneural, and mesenchymal states as potential starting points for gliomagenesis. At 90 days, bulk sequencing detected few differentially expressed transcripts, whereas stochastic profiling revealed cell states for neurons and mural cells that do not give rise to glial tumors, suggesting cellular dead-ends for gliomagenesis. Importantly, mutant OPCs that strongly expressed key effectors of nonsense-mediated decay (Upf3b) and homology-dependent DNA repair (Rad51c, Slx1b, Ercc4) were identified along with DNA-damage markers, suggesting transcription-associated replication stress. Analysis of 10-cell transcriptomes at 90 days identified a locus of elevated gene expression containing an additional repair endonuclease (Mus81) and Rin1, a Ras-Raf antagonist and possible counterbalance to Nf1 loss, which was microdeleted or downregulated in gliomas at 150 days. These hidden cell-state variations uncover replication stress as a potential bottleneck that must be resolved for glioma initiation. SIGNIFICANCE: Profiling premalignant cell states in a mouse model of glioma uncovers regulatory heterogeneity in glioma cells-of-origin and defines a state of replication stress that precedes tumor initiation.See related articles by Singh and colleagues, p. 1840 and Schaff and colleagues, p. 1853.

A Tale of Ice and Fire: The Dual Role for 17β-Estradiol in Balancing DNA Damage and Genome Integrity

Simple Summary

Paradoxically, although the steroid hormone 17β-estradiol (E2) regulates many aspects of male and female physiology, it is described in the chemical indexes as a carcinogen. By the analysis of the literature, we unveil here a novel concept for which E2 possesses a dual nature for which it is both a toxic and a homeostatic regulator controlling DNA stability. Therefore, cancer could arise as a consequence of the deregulation of this delicate equilibrium between cellular pathways.

Abstract

17β-estradiol (E2) regulates human physiology both in females and in males. At the same time, E2 acts as a genotoxic substance as it could induce DNA damages, causing the initiation of cellular transformation. Indeed, increased E2 plasma levels are a risk factor for the development of several types of cancers including breast cancer. This paradoxical identity of E2 undermines the foundations of the physiological definition of “hormone” as E2 works both as a homeostatic regulator of body functions and as a genotoxic compound. Here, (i) the molecular circuitries underlying this double face of E2 are reviewed, and (ii) a possible framework to reconcile the intrinsic discrepancies of the E2 function is reported. Indeed, E2 is a regulator of the DNA damage response, which this hormone exploits to calibrate its genotoxicity with its physiological effects. Accordingly, the genes required to maintain genome integrity belong to the E2-controlled cellular signaling network and are essential for the appearance of the E2-induced cellular effects. This concept requires an “upgrade” to the vision of E2 as a “genotoxic hormone”, which balances physiological and detrimental pathways to guarantee human body homeostasis. Deregulation of this equilibrium between cellular pathways would determine the E2 pathological effects.

Clinical Candidates Targeting the ATR-CHK1-WEE1 Axis in Cancer

Selective killing of cancer cells while sparing healthy ones is the principle of the perfect cancer treatment and the primary aim of many oncologists, molecular biologists, and medicinal chemists. To achieve this goal, it is crucial to understand the molecular mechanisms that distinguish cancer cells from healthy ones. Accordingly, several clinical candidates that use particular mutations in cell-cycle progressions have been developed to kill cancer cells. As the majority of cancer cells have defects in G1 control, targeting the subsequent intra‑S or G2/M checkpoints has also been extensively pursued. This review focuses on clinical candidates that target the kinases involved in intra‑S and G2/M checkpoints, namely, ATR, CHK1, and WEE1 inhibitors. It provides insight into their current status and future perspectives for anticancer treatment. Overall, even though CHK1 inhibitors are still far from clinical establishment, promising accomplishments with ATR and WEE1 inhibitors in phase II trials present a positive outlook for patient survival.

Signaling pathways involved in cell cycle arrest during the DNA breaks

Our genome bears tens of thousands of harms and devastations per day; In this regard, numerous sophisticated and complicated mechanisms are embedded by our cells in furtherance of remitting an unchanged and stable genome to their next generation. These mechanisms, that are collectively called DDR, have the duty of detecting the lesions and repairing them. it's necessary for the viability of any living cell that sustain the integrity and stability of its genetic content and this highlights the role of mediators that transduce the signals of DNA damage to the cell cycle in order to prevent the replication of a defective DNA. In this paper, we review the signaling pathways that lie between these processes and define how different ingredients of DDR are also able to affect the checkpoint signaling.

The Hammer and the Dance of Cell Cycle Control

Cell cycle checkpoints secure ordered progression from one cell cycle phase to the next. They are important to signal cell stress and DNA lesions and to stop cell cycle progression when severe problems occur. Recent work suggests, however, that the cell cycle control machinery responds in more subtle and sophisticated ways when cells are faced with naturally occurring challenges, such as replication impediments associated with endogenous replication stress. Instead of following a stop and go approach, cells use fine-tuned deceleration and brake release mechanisms under the control of ataxia telangiectasia and Rad3-related protein kinase (ATR) and checkpoint kinase 1 (CHK1) to more flexibly adapt their cell cycle program to changing conditions. We highlight emerging examples of such intrinsic cell cycle checkpoint regulation and discuss their physiological and clinical relevance.

HAS3-induced extracellular vesicles from melanoma cells stimulate IHH mediated c-Myc upregulation via the hedgehog signaling pathway in target cells

Intercellular communication is fundamental to the survival and maintenance of all multicellular systems, whereas dysregulation of communication pathways can drive cancer progression. Extracellular vesicles (EVs) are mediators of cell-to-cell communication that regulate a variety of cellular processes involved in tumor progression. Overexpression of a specific plasma membrane enzyme, hyaluronan synthase 3 (HAS3), is one of the factors that can induce EV shedding. HAS3, and particularly its product hyaluronan (HA), are carried by EVs and are known to be associated with the tumorigenic properties of cancer cells. To elucidate the specific effects of cancerous, HAS3-induced EVs on target cells, normal human keratinocytes and melanoma cells were treated with EVs derived from GFP-HAS3 expressing metastatic melanoma cells. We found that the HA receptor CD44 participated in the regulation of EV binding to target cells. Furthermore, GFP-HAS3-positive EVs induced HA secretion, proliferation and invasion of target cells. Our results suggest that HAS3-EVs contains increased quantities of IHH, which activates the target cell hedgehog signaling cascade and leads to the activation of c-Myc and regulation of claspin expression. This signaling of IHH in HAS3-EVs resulted in increased cell proliferation. Claspin immunostaining correlated with HA content in human cutaneous melanocytic lesions, supporting our in vitro findings and suggesting a reciprocal regulation between claspin expression and HA synthesis. This study shows for the first time that EVs originating from HAS3 overexpressing cells carry mitogenic signals that induce proliferation and epithelial-to-mesenchymal transition in target cells. The study also identifies a novel feedback regulation between the hedgehog signaling pathway and HA metabolism in melanoma, mediated by EVs carrying HA and IHH.

A Timeless Tale: G4 structure recognition by the fork protection complex triggers unwinding by DDX11 helicase

How the replisome senses and deals with DNA secondary structures has been a mystery. A new study from the Sale and Pellegrini laboratories finds that the Timeless protein has a G-quadruplex binding domain that works together with the DDX11 helicase to facilitate replication of G4 DNA structures.

Implications of CLSPN Variants in Cellular Function and Susceptibility to Cancer

Claspin is a multifunctional protein that participates in physiological processes essential for cell homeostasis that are often defective in cancer, namely due to genetic changes. It is conceivable that Claspin gene (CLSPN) alterations may contribute to cancer development. Therefore, CLSPN germline alterations were characterized in sporadic and familial breast cancer and glioma samples, as well as in six cancer cell lines. Their association to cancer susceptibility and functional impact were investigated. Eight variants were identified (c.-68C>T, c.17G>A, c.1574A>G, c.2230T>C, c.2028+16G>A, c.3595-3597del, and c.3839C>T). CLSPN c.1574A>G (p.Asn525Ser) was significantly associated with breast cancer and was shown to cause partial exon skipping and decreased Claspin expression and Chk1 activation in a minigene splicing assay and in signalling experiments, respectively. CLSPN c.2028+16G>A was significantly associated with familial breast cancer and glioma, whereas c.2230T>C (p.Ser744Pro), was exclusively detected in breast cancer and glioma patients, but not in healthy controls. The remaining variants lacked a significant association with cancer. Nevertheless, the c.-68C>T promoter variant increased transcriptional activity in a luciferase assay. In conclusion, some of the CLSPN variants identified in the present study appear to modulate Claspin’s function by altering CLSPN transcription and RNA processing, as well as Chk1 activation.

A Systems View of the Genome Guardians: Mapping the Signaling Circuitry Underlying Oligonucleotide/Oligosaccharide-Binding Fold Proteins

The oligonucleotide/oligosaccharide-binding (OB)-fold domain proteins are considered as genome guardians, whose functions are extending beyond genomic stability. The broad functional diversity of the OB-fold proteins is attributed to their protein-DNA, protein-RNA, and protein-protein interactions (PPI). To understand the connectivity of the human OB-fold proteins, we report here a systems-level approach. Specifically, we mapped all human OB-fold PPI networks and evaluated topological features such as network robustness and network hub, among others. We found that the OB-fold network comprised of 227 nodes forming 5523 interactions, and has a scale-free topology having UBA52, ATR, and TP53 as leading hub proteins that control efficient communication within the network. Furthermore, four different clusters and subclusters have been identified, which are implicated in diverse cellular processes, including DNA replication, repair, maintenance of genomic stability, RNA processing, spermatogenesis, complement system, and telomere maintenance. The importance of these clusters is further strengthened by knockout studies, which showed a significant decrease in topological properties. In summary, this study provides new insights on the role of OB-fold protein as genome guardians in regard to the underlying mechanism of signaling pathways, the roles of key regulators, and thus, offers new prospects as potential targets for diagnostics and therapeutics purposes.

OZF is a Claspin-interacting protein essential to maintain the replication fork progression rate under replication stress

DNA replication is essential for cell proliferation and is one of the cell cycle stages where DNA is more vulnerable. Replication stress is a prominent property of tumor cells and an emerging target for cancer therapy. Although it is not directly involved in nucleotide incorporation, Claspin is a protein with relevant functions in DNA replication. It harbors a DNA-binding domain that interacts preferentially with branched or forked DNA molecules. It also acts as a platform for the interaction of proteins related to DNA damage checkpoint activation, DNA repair, DNA replication origin firing, and fork progression. In order to find new proteins potentially involved in the regulation of DNA replication, we performed a two-hybrid screen to discover new Claspin-binding proteins. This system allowed us to identify the zinc-finger protein OZF (ZNF146) as a new Claspin-interacting protein. OZF is also present at replication forks and co-immunoprecipitates not only with Claspin but also with other replisome components. Interestingly, OZF depletion does not affect DNA replication in a normal cell cycle, but its depletion induces a reduction in the fork progression rate under replication stress conditions. Our results suggest that OZF is a Claspin-binding protein with a specific function in fork progression under replication stress.