Loss of CUL4A expression is underlying cisplatin hypersensitivity in colorectal carcinoma cells with acquired trabectedin resistance

Cullin-RING Ligase 4 in Cancer: Structure, Functions, and Mechanisms

Cullin-RING ligase 4 (CRL4) has attracted enormous attentions because of its extensive regulatory roles in a wide variety of biological and pathological events, especially cancer-associated events. CRL4 exerts pleiotropic effects by targeting various substrates for proteasomal degradation or changes in activity through different internal compositions to regulate diverse events in cancer progression. In this review, we summarize the structure of CRL4 with manifold compositional modes and clarify the emerging functions and molecular mechanisms of CRL4 in a series of cancer-associated events.

CUL4A silencing attenuates cervical carcinogenesis and improves Cisplatin sensitivity

CUL4A is an ubiquitin ligase deregulated in numerous pathologies including cancer and even hijacked by viruses for facilitating their survival and propagation. However, its role in Human papilloma virus (HPV)-mediated cervical carcinogenesis remains elusive. The UALCAN and GEPIA datasets were analyzed to ascertain the transcript levels of CUL4A in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) patients. Subsequently, various biochemical assays were employed to explore the functional contribution of CUL4A in cervical carcinogenesis and to shed some light on its involvement in Cisplatin resistance in cervical cancer. Our UALCAN and GEPIA datasets analyses reveal elevated CUL4A transcript levels in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) patients that correlate with adverse clinicopathological parameters such as tumor stage and lymph node metastasis. Kaplan-Meier plot and GEPIA assessment depict poor prognosis of CESC patients having high CUL4A expression. Varied biochemical assays illustrate that CUL4A inhibition severely curtails hallmark malignant properties such as cellular proliferation, migration, and invasion of cervical cancer cells. We also show that CUL4A knockdown in HeLa cells causes increased susceptibility and better apoptotic induction toward Cisplatin, a mainstay drug used in cervical cancer treatment. More interestingly, we find reversion of Cisplatin-resistant phenotype of HeLa cells and an augmented cytotoxicity towards the platinum compound upon CUL4A downregulation. Taken together, our study underscores CUL4A as a cervical cancer oncogene and illustrates its potential as a prognosis indicator. Our investigation provides a novel avenue in improving current anti-cervical cancer therapy and overcoming the bottle-neck of Cisplatin resistance.

Paraptotic Cell Death as an Unprecedented Mode of Action Observed for New Bipyridine-Silver(I) Compounds Bearing Phosphane Coligands

In this work, we investigated the anticancer activity of several novel silver(I) 2,2'-bipyridine complexes containing either triphenylphosphane (PPh3) or 1,2-bis(diphenylphosphino)ethane (dppe) ligands. All compounds were characterized by diverse analytical methods including ESI-MS spectrometry; NMR, UV-vis, and FTIR spectroscopies; and elemental analysis. Moreover, several compounds were also studied by X-ray single-crystal diffraction. Subsequently, the compounds were investigated for their anticancer activity against drug-resistant and -sensitive cancer cells. Noteworthily, neither carboplatin and oxaliplatin resistance nor p53 deletion impacted on their anticancer efficacy. MES-OV cells displayed exceptional hypersensitivity to the dppe-containing drugs. This effect was not based on thioredoxin reductase inhibition, enhanced drug uptake, or apoptosis induction. In contrast, dppe silver drugs induced paraptosis, a novel recently described form of programmed cell death. Together with the good tumor specificity of this compound's class, this work suggests that dppe-containing silver complexes could be interesting drug candidates for the treatment of resistant ovarian cancer.

The cross talk of ubiquitination and chemotherapy tolerance in colorectal cancer

Ubiquitination, a highly adaptable post-translational modification, plays a pivotal role in maintaining cellular protein homeostasis, encompassing cancer chemoresistance-associated proteins. Recent findings have indicated a potential correlation between perturbations in the ubiquitination process and the emergence of drug resistance in CRC cancer. Consequently, numerous studies have spurred the advancement of compounds specifically designed to target ubiquitinates, offering promising prospects for cancer therapy. In this review, we highlight the role of ubiquitination enzymes associated with chemoresistance to chemotherapy via the Wnt/β-catenin signaling pathway, epithelial-mesenchymal transition (EMT), and cell cycle perturbation. In addition, we summarize the application and role of small compounds that target ubiquitination enzymes for CRC treatment, along with the significance of targeting ubiquitination enzymes as potential cancer therapies.

The cell-line-derived subcutaneous tumor model in preclinical cancer research

Tumor-bearing experimental animals are essential for preclinical cancer drug development. A broad range of tumor models is available, with the simplest and most widely used involving a tumor of mouse or human origin growing beneath the skin of a mouse: the subcutaneous tumor model. Here, we outline the different types of in vivo tumor model, including some of their advantages and disadvantages and how they fit into the drug-development process. We then describe in more detail the subcutaneous tumor model and key steps needed to establish it in the laboratory, namely: choosing the mouse strain and tumor cells; cell culture, preparation and injection of tumor cells; determining tumor volume; mouse welfare; and an appropriate experimental end point. The protocol leads to subcutaneous tumor growth usually within 1-3 weeks of cell injection and is suitable for those with experience in tissue culture and mouse experimentation.

Targeting fibroblast growth factor receptors to combat aggressive ependymoma

Ependymomas (EPN) are central nervous system tumors comprising both aggressive and more benign molecular subtypes. However, therapy of the high-risk subtypes posterior fossa group A (PF-A) and supratentorial RELA-fusion positive (ST-RELA) is limited to gross total resection and radiotherapy, as effective systemic treatment concepts are still lacking. We have recently described fibroblast growth factor receptors 1 and 3 (FGFR1/FGFR3) as oncogenic drivers of EPN. However, the underlying molecular mechanisms and their potential as therapeutic targets have not yet been investigated in detail. Making use of transcriptomic data across 467 EPN tissues, we found that FGFR1 and FGFR3 were both widely expressed across all molecular groups. FGFR3 mRNA levels were enriched in ST-RELA showing the highest expression among EPN as well as other brain tumors. We further identified high expression levels of fibroblast growth factor 1 and 2 (FGF1, FGF2) across all EPN subtypes while FGF9 was elevated in ST-EPN. Interrogation of our EPN single-cell RNA-sequencing data revealed that FGFR3 was further enriched in cycling and progenitor-like cell populations. Corroboratively, we found FGFR3 to be predominantly expressed in radial glia cells in both mouse embryonal and human brain datasets. Moreover, we detected alternative splicing of the FGFR1/3-IIIc variant, which is known to enhance ligand affinity and FGFR signaling. Dominant-negative interruption of FGFR1/3 activation in PF-A and ST-RELA cell models demonstrated inhibition of key oncogenic pathways leading to reduced cell growth and stem cell characteristics. To explore the feasibility of therapeutically targeting FGFR, we tested a panel of FGFR inhibitors in 12 patient-derived EPN cell models revealing sensitivity in the low-micromolar to nano-molar range. Finally, we gain the first clinical evidence for the activity of the FGFR inhibitor nintedanib in the treatment of a patient with recurrent ST-RELA. Together, these preclinical and clinical data suggest FGFR inhibition as a novel and feasible approach to combat aggressive EPN.

E3 Ubiquitin Ligase in Anticancer Drugdsla Resistance: Recent Advances and Future Potential

Drug therapy is the primary treatment for patients with advanced cancer. The use of anticancer drugs will inevitably lead to drug resistance, which manifests as tumor recurrence. Overcoming chemoresistance may enable cancer patients to have better therapeutic effects. However, the mechanisms underlying drug resistance are poorly understood. E3 ubiquitin ligases (E3s) are a large class of proteins, and there are over 800 putative functional E3s. E3s play a crucial role in substrate recognition and catalyze the final step of ubiquitin transfer to specific substrate proteins. The diversity of the set of substrates contributes to the diverse functions of E3s, indicating that E3s could be desirable drug targets. The E3s MDM2, FBWX7, and SKP2 have been well studied and have shown a relationship with drug resistance. Strategies targeting E3s to combat drug resistance include interfering with their activators, degrading the E3s themselves and influencing the interaction between E3s and their substrates. Research on E3s has led to the discovery of possible therapeutic methods to overcome the challenging clinical situation imposed by drug resistance. In this article, we summarize the role of E3s in cancer drug resistance from the perspective of drug class.

FLYWCH1, a Multi-Functional Zinc Finger Protein Contributes to the DNA Repair Pathway

Over recent years, several Cys2-His2 (C2H2) domain-containing proteins have emerged as critical players in repairing DNA-double strand breaks. Human FLYWCH1 is a newly characterised nuclear transcription factor with (C2H2)-type zinc-finger DNA-binding domains. Yet, our knowledge about FLYWCH1 is still in its infancy. This study explores the expression, role and regulation of FLYWCH1 in the context of DNA damage and repair. We provide evidence suggesting a potential contribution of FLYWCH1 in facilitating the recruitment of DNA-damage response proteins (DDRPs). We found that FLYWCH1 colocalises with γH2AX in normal fibroblasts and colorectal cancer (CRC) cell lines. Importantly, our results showed that enforced expression of FLYWCH1 induces the expression of γH2AX, ATM and P53 proteins. Using an ATM-knockout (ATM^KO) model, we indicated that FLYWCH1 mediates the phosphorylation of H2AX (Ser139) independently to ATM expression. On the other hand, the induction of DNA damage using UV-light induces the endogenous expression of FLYWCH1. Conversely, cisplatin treatment reduces the endogenous level of FLYWCH1 in CRC cell lines. Together, our findings uncover a novel FLYWCH1/H2AX phosphorylation axis in steady-state conditions and during the induction of the DNA-damage response (DDR). Although the role of FLYWCH1 within the DDR machinery remains largely uncharacterised and poorly understood, we here report for the first-time findings that implicate FLYWCH1 as a potential participant in the DNA damage response signaling pathways.

p53 Loss Mediates Hypersensitivity to ETS Transcription Factor Inhibition Based on PARylation-Mediated Cell Death Induction

Simple Summary

ETS transcription factors are potent oncogenic drivers in several cancer types and represent promising therapeutic targets. However, molecular factors influencing response to ETS factor inhibition are widely unknown so far. Here, we uncover that sensitivity of cancer cells against ETS factor blockade by the small molecule inhibitor YK-4-279 is strongly promoted by p53 loss in a MAPK-driven background. Induction of a parthanatos-like cell death based on a deregulated MAPK/ETS1/p53/PARP1 signal axis is identified as underlying molecular mechanism. Hence, this study suggests a novel and biomarker-driven therapeutic strategy for p53-deleted tumours, generally known for their profound therapy resistance.

Abstract

The small-molecule E26 transformation-specific (ETS) factor inhibitor YK-4-279 was developed for therapy of ETS/EWS fusion-driven Ewing’s sarcoma. Here we aimed to identify molecular factors underlying YK-4-279 responsiveness in ETS fusion-negative cancers. Cell viability screenings that deletion of P53 induced hypersensitization against YK-4-279 especially in the BRAF^V600E-mutated colon cancer model RKO. This effect was comparably minor in the BRAF wild-type HCT116 colon cancer model. Out of all ETS transcription factor family members, especially ETS1 overexpression at mRNA and protein level was induced by deletion of P53 specifically under BRAF-mutated conditions. Exposure to YK-4-279 reverted ETS1 upregulation induced by P53 knock-out in RKO cells. Despite upregulation of p53 by YK-4-279 itself in RKOp53 wild-type cells, YK-4-279-mediated hyperphosphorylation of histone histone H2A.x was distinctly more pronounced in the P53 knock-out background. YK-4-279-induced cell death in RKOp53-knock-out cells involved hyperPARylation of PARP1, translocation of the apoptosis-inducible factor AIF into nuclei, and induction of mitochondrial membrane depolarization, all hallmarks of parthanatos. Accordingly, pharmacological PARP as well as BRAF^V600E inhibition showed antagonistic activity with YK-4-279 especially in the P53 knock-out background. Taken together, we identified ETS factor inhibition as a promising strategy for the treatment of notoriously therapy-resistant p53-null solid tumours with activating MAPK mutations.

FGF9 promotes cisplatin resistance in colorectal cancer via regulation of Wnt/β-catenin signaling pathway

Development of cisplatin resistance in colorectal cancer is largely caused by dysregulation of signaling pathways, including the Wnt/β-catenin signaling pathway, in cancer cells. Further investigation into the molecular mechanism of chemoresistance could improve outcomes for patients with colorectal cancer. The present study determined that fibroblast growth factor 9 (FGF9) was overexpressed in tumor tissues compared with normal tissues from patients with colorectal cancer. Using the colorectal cancer cell line LoVo, transfection of recombinant FGF9 decreased cisplatin-induced cell apoptosis whilst FGF9 silencing increased cisplatin-induced apoptosis. Western blot analysis and reverse transcription-quantitative polymerase chain reaction demonstrated that FGF9 decreased adenomatous polyposis coli (APC) mRNA and protein expression and contributed to activation of the Wnt/β-catenin signaling pathway. Notably, an increase in FGF9 and β-catenin protein expression and a decrease in APC protein expression was observed in the established LoVo cisplatin resistant cell line (LoVo/cisplatin). Silencing of FGF9 reversed cisplatin resistance of LoVo/cisplatin cells. In conclusion, the present findings suggested that FGF9 activated the Wnt signaling pathway and was a mediator of cisplatin resistance in colorectal cancer.

CUL4A expression is associated with tumor stage and prognosis in nasopharyngeal carcinoma

Cullin 4A (CUL4A) is a protein of E3 ubiquitin ligase with many cellular processes. CUL4A could regulate cell cycle, development, apoptosis, and genome instability. This study aimed to analyze the expression of CUL4A in nasopharyngeal carcinoma (NPC) tissues and the associations of CUL4A expression with prognostic significance. A total of 115 NPC patients were collected to assess the protein expression of CUL4A by immunohistochemistry, so as to analyze the relationships between CUL4A expression and clinicopathological and prognostic parameters. All patients were followed-up until death or 5 years. The results showed that high expression of CUL4A was significantly associated with larger primary tumor size (P = .026), higher nodal status (P = .013), more distant metastasis (P = .020), and higher TNM stage (P = .005). Kaplan-Meier curves showed that patients with higher CUL4A expression had significantly shorter overall survival (OS) and progression-free survival (PFS) (both P < .001). In multivariate Cox analysis, CUL4A is an independent prognostic factor for OS (P = .016; hazard ratio [HR] = 2.770, 95% CI: 1.208-6.351) and PFS (P = .022; HR = 2.311, 95% CI: 1.126-4.743). In conclusion, high expression of CUL4A was associated with advanced disease status of NPC, and might serve as an independent prognostic factor.

Cul4 E3 ubiquitin ligase regulates ovarian cancer drug resistance by targeting the antiapoptotic protein BIRC3

CRL4, a well-defined E3 ligase, has been reported to be upregulated and is proposed to be a potential drug target in ovarian cancers. However, the biological functions of CRL4 and the underlying mechanism regulating cancer chemoresistance are still largely elusive. Here, we show that CRL4 is considerably increased in cisplatin-resistant ovarian cancer cells, and CRL4 knockdown with shRNAs is able to reverse cisplatin-resistance of ovarian cancer cells. Moreover, CRL4 knockdown markedly inhibits the expression of BIRC3, one of the inhibitors of apoptosis proteins (IAPs). Besides, lower expression level of BIRC3 is associated with better prognosis of ovarian cancer patients, and BIRC3 knockdown in ovarian cancer cells can recover their sensitivity to cisplatin. More importantly, we demonstrate that CRL4 regulates BIRC3 expression by mediating the STAT3, but not the PI3K pathway. Therefore, our results identified CRL4 as an important factor in ovarian cancer chemoresistance, suggesting that CRL4 and BIRC3 may serve as novel therapeutic targets for relapsed patients after treatment with cisplatin and its derivative to overcome the bottle neck of ovarian cancer chemoresistance.

The thiosemicarbazone Me2NNMe2 induces paraptosis by disrupting the ER thiol redox homeostasis based on protein disulfide isomerase inhibition

Due to their high biological activity, thiosemicarbazones have been developed for treatment of diverse diseases, including cancer, resulting in multiple clinical trials especially of the lead compound Triapine. During the last years, a novel subclass of anticancer thiosemicarbazones has attracted substantial interest based on their enhanced cytotoxic activity. Increasing evidence suggests that the double-dimethylated Triapine derivative Me2NNMe2 differs from Triapine not only in its efficacy but also in its mode of action. Here we show that Me2NNMe2- (but not Triapine)-treated cancer cells exhibit all hallmarks of paraptotic cell death including, besides the appearance of endoplasmic reticulum (ER)-derived vesicles, also mitochondrial swelling and caspase-independent cell death via the MAPK signaling pathway. Subsequently, we uncover that the copper complex of Me2NNMe2 (a supposed intracellular metabolite) inhibits the ER-resident protein disulfide isomerase, resulting in a specific form of ER stress based on disruption of the Ca2+ and ER thiol redox homeostasis. Our findings indicate that compounds like Me2NNMe2 are of interest especially for the treatment of apoptosis-resistant cancer and provide new insights into mechanisms underlying drug-induced paraptosis.

Altered membrane rigidity via enhanced endogenous cholesterol synthesis drives cancer cell resistance to destruxins

Destruxins, secondary metabolites of entomopathogenic fungi, exert a wide variety of interesting characteristics ranging from antiviral to anticancer effects. Although their mode of action was evaluated previously, the molecular mechanisms of resistance development are unknown. Hence, we have established destruxin-resistant sublines of HCT116 colon carcinoma cells by selection with the most prevalent derivatives, destruxin (dtx)A, dtxB and dtxE. Various cell biological and molecular techniques were applied to elucidate the regulatory mechanisms underlying these acquired and highly stable destruxin resistance phenotypes. Interestingly, well-known chemoresistance-mediating ABC efflux transporters were not the major players. Instead, in dtxA- and dtxB-resistant cells a hyper-activated mevalonate pathway was uncovered resulting in increased de-novo cholesterol synthesis rates and elevated levels of lanosterol, cholesterol as well as several oxysterol metabolites. Accordingly, inhibition of the mevalonate pathway at two different steps, using either statins or zoledronic acid, significantly reduced acquired but also intrinsic destruxin resistance. Vice versa, cholesterol supplementation protected destruxin-sensitive cells against their cytotoxic activity. Additionally, an increased cell membrane adhesiveness of dtxA-resistant as compared to parental cells was detected by atomic force microscopy. This was paralleled by a dramatically reduced ionophoric capacity of dtxA in resistant cells when cultured in absence but not in presence of statins. Summarizing, our results suggest a reduced ionophoric activity of destruxins due to cholesterol-mediated plasma membrane re-organization as molecular mechanism underlying acquired destruxin resistance in human colon cancer cells. Whether this mechanism might be valid also in other cell types and organisms exposed to destruxins e.g. as bio-insecticides needs to be evaluated.