Effect of duplex drugs linking 2'-deoxy-5-fluorouridine (5-FdU) with 3'-C-ethynylcytidine (ECyd) on hepatoblastoma cell lines

Late-stage guanine C8-H alkylation of nucleosides, nucleotides, and oligonucleotides via photo-mediated Minisci reaction

Chemically modified nucleosi(ti)des and functional oligonucleotides (ONs, including therapeutic oligonucleotides, aptamer, nuclease, etc.) have been identified playing an essential role in the areas of medicinal chemistry, chemical biology, biotechnology, and nanotechnology. Introduction of functional groups into the nucleobases of ONs mostly relies on the laborious de novo chemical synthesis. Due to the importance of nucleosides modification and aforementioned limitations of functionalizing ONs, herein, we describe a highly efficient site-selective alkylation at the C8-position of guanines in guanosine (together with its analogues), GMP, GDP, and GTP, as well as late-stage functionalization of dinucleotides and single-strand ONs (including ssDNA and RNA) through photo-mediated Minisci reaction. Addition of catechol to assist the formation of alkyl radicals via in situ generated boronic acid catechol ester derivatives (BACED) markedly enhances the yields especially for the reaction of less stable primary alkyl radicals, and is the key to success for the post-synthetic alkylation of ONs. This method features excellent chemoselectivity, no necessity for pre-protection, wide range of substrate scope, various free radical precursors, and little strand lesion. Downstream applications in disease treatment and diagnosis, or as biochemical probes to study biological processes after linking with suitable fluorescent compounds are expected.

Advance of structural modification of nucleosides scaffold

With Remdesivir being approved by FDA as a drug for the treatment of Corona Virus Disease 2019 (COVID-19), nucleoside drugs have once again received widespread attention in the medical community. Herein, we summarized modification of traditional nucleoside framework (sugar + base), traizole nucleosides, nucleoside analogues assembled by other drugs, macromolecule-modified nucleosides, and their bioactivity rules. 2′-“Ara”-substituted by –F or –CN group, and 3′-“ara” substituted by acetylenyl group can greatly influence their anti-tumor activities. Dideoxy dehydrogenation of 2′,3′-sites can enhance antiviral efficiencies. Acyclic nucleosides and L-type nucleosides mainly represented antiviral capabilities. 5-F Substituted uracil analogues exihibit anti-tumor effects, and the substrates substituted by –I, –CF₃, bromovinyl group usually show antiviral activities. The sugar coupled with 1-N of triazolid usually displays anti-tumor efficiencies, while the sugar coupled with 2-N of triazolid mainly represents antiviral activities. The nucleoside analogues assembled by cholesterol, polyethylene glycol, fatty acid and phospholipid would improve their bioavailabilities and bioactivities, or reduce their toxicities.

Human foreskin fibroblasts: from waste bag to important biomedical applications

Circumcision is one of the most performed surgical procedures worldwide, and it is estimated that one in three men worldwide is circumcised, which makes the preputial skin removed after surgery an abundant material for possible applications. In particular, it is possible efficiently to isolate the cells of the foreskin, with fibroblasts being the most abundant cells of the dermis and the most used in biomedical research. This work aimed to review the knowledge and obtain a broad view of the main applications of human foreskin fibroblast cell culture. A literature search was conducted, including clinical trials, preclinical basic research studies, reviews and experimental studies. Several medical and laboratory applications of human foreskin fibroblast cell culture have been described, especially when it comes to the use of human foreskin fibroblasts as feeder cells for the cultivation of human embryonic stem cells, in addition to co-culture with other cell types. The culture of foreskin fibroblasts has also been used to: obtain induced pluripotent stem cells; the diagnosis of Clostridium difficile; to test the toxicity and effect of substances on normal cells, especially the toxicity of possible antineoplastic drugs; in viral culture, mainly of the human cytomegalovirus, study of the pathogenesis of other microorganisms; varied studies of cellular physiology and cellular interactions. Fibroblasts are important for cell models for varied application cultures, demonstrating how the preputial material can be reused, making possible new applications.

Level of evidence: Not applicable for this multicentre audit.

The conjugated antimetabolite 5-FdU-ECyd and its cellular and molecular effects on platinum-sensitive vs. -resistant ovarian cancer cells in vitro

Background

Resistance to platinum-based chemotherapy is a clinical challenge in the treatment of ovarian cancer (OC) and limits survival. Therefore, innovative drugs against platinum-resistance are urgently needed. Our therapeutic concept is based on the conjugation of two chemotherapeutic compounds to a monotherapeutic pro-drug, which is taken up by cancer cells and cleaved into active cytostatic metabolites. We explore the activity of the duplex-prodrug 5-FdU-ECyd, covalently linking 2'-deoxy-5-fluorouridine (5-FdU) and 3'-C-ethynylcytidine (ECyd), on platinum-resistant OC cells.

Methods

In vitro assays and RNA-Sequencing were applied for characterization of 5-FdU-ECyd treated platinum-sensitive A2780 and isogenic platinum-resistant A2780cis and independent platinum-resistant Skov-3-IP OC cells.

Results

Nano molar 5-FdU-ECyd concentrations induced a rapid dose-dependent decline of cell viability in platinum-sensitive and -resistant OC cells. The effect of 5-FdU-ECyd was accompanied by the formation of DNA double strand breaks and apoptosis induction, indicated by a strong increase of pro-apoptotic molecular markers. Moreover, 5-FdU-ECyd efficiently decreased migration of platinum-resistant OC cells and inhibited clonogenic or spheroidal growth. Transcriptome analysis showed early up-regulation of CDKN1A and c-Fos in both, platinum-resistant and -sensitive cells after 5-FdU-ECyd treatment and de-regulation of distinct cellular pathways involved in cell cycle regulation, apoptosis, DNA-damage response and RNA-metabolism. Combined treatment of 5-FdU-ECyd and cisplatin did not show a synergistic cellular response, suggesting the potential use of 5-FdU-ECyd as a monotherapeutic agent.

Conclusion

Our data provide novel mechanistic insight into the anti-tumor effect of 5-FdU-ECyd and we hypothesize that this duplex-prodrug could be a promising therapeutic option for OC patients with resistance to platinum-based chemotherapy.

Metabolism, Biochemical Actions, and Chemical Synthesis of Anticancer Nucleosides, Nucleotides, and Base Analogs

Nucleoside, nucleotide, and base analogs have been in the clinic for decades to treat both viral pathogens and neoplasms. More than 20% of patients on anticancer chemotherapy have been treated with one or more of these analogs. This review focuses on the chemical synthesis and biology of anticancer nucleoside, nucleotide, and base analogs that are FDA-approved and in clinical development since 2000. We highlight the cellular biology and clinical biology of analogs, drug resistance mechanisms, and compound specificity towards different cancer types. Furthermore, we explore analog syntheses as well as improved and scale-up syntheses. We conclude with a discussion on what might lie ahead for medicinal chemists, biologists, and physicians as they try to improve analog efficacy through prodrug strategies and drug combinations.

A single-center retrospective study of pediatric hepatoblastoma

Hepatoblastoma is a malignant liver tumor generally diagnosed in infants and children <3 years old. The current retrospective study aimed to investigate the associations of tumor stage, pathological type, metastasis and chemotherapy with clinical outcomes. In the current study, a total of 102 patients with hepatoblastoma were enrolled between September 2006 and June 2014. Clinical records and follow-up information for each of patient were obtained to conduct a Kaplan-Meier survival analysis and log-rank test. The median age of the subjects was 1.5 years, and 98 patients had stage III or IV hepatoblastoma. Complete or partial remittance occurred in 72 subjects, and 91 underwent surgical operation. The survival rate differed significantly among patients with different tumor stages (P=0.015, χ²=8.359). The mortality rate of stage IV subjects with intrahepatic metastasis was significantly higher than that of those without (P=0.004). Among the 45 subjects with relapsed hepatoblastoma, the mortality rate was higher in the subjects that abandoned chemotherapy than in patients who continued regular chemotherapy. In total, 27 of 45 subjects with relapsed hepatoblastoma succumbed to the disease; 20 of them abandoned chemotherapy treatment; and the remaining 7 patients underwent regular chemotherapy and succumbed to the disease by the end of follow-up. The present study indicates that the increased mortality rate was associated with postoperative residual-induced intrahepatic metastasis and relapsed hepatoblastoma; and that regular chemotherapy is necessary for patient to achieve complete or partial remission following surgical operation.

Induction of apoptosis in cervical cancer cells by the duplex drug 5-FdU-ECyd, coupling 2'-deoxy-5-fluorouridine and 3'-C-ethinylcytidine

OBJECTIVE

Therapeutic options are limited for patients with advanced cervical cancer, and more effective drugs with favorable side-effect profiles are needed. We developed a nucleoside analogue duplex drug (5-FdU-ECyd), in which the DNA synthesis inhibitor 5-fluorodeoxyuridine is coupled to the RNA synthesis inhibitor 3'-C-ethinylcytidine. We therefore aimed to test its efficacy in cervical carcinoma cells in vitro and to establish its mechanism of action.

METHODS

The cytotoxic effects of 5-FdU-ECyd on cervical cancer cells were assessed using the MTT assay, clonality assays, FACScan analysis, and its effect on cancer cell spheroids. Mechanisms of cell death were analyzed by Western blotting for apoptosis and autophagy pathways and mitochondrial membrane potential.

RESULTS

HeLa, CaSki, SiHa, and Me180 cervical cancer cells were highly sensitive to 5-FdU-ECyd in both 2- and 3-dimensional cancer models. The cell death induced by 5-FdU-ECyd was associated with characteristic morphological and biochemical signs of apoptosis, including nuclear chromatin condensation and fragmentation, PARP cleavage, and a breakdown in mitochondrial membrane potential. 5-FdU-ECyd treatment led to an early S-phase arrest and drastically reduced expression of the anti-apoptosis protein Mcl-1 and increased signaling via the JNK and p38 MAPK pathways.

CONCLUSIONS

5-FdU-ECyd is highly cytotoxic in cervical cancer cells and exploits apoptosis pathways that might be specific to cancer, but not normal cells. 5-FdU-ECyd might represent a new chemotherapeutic option for patients with advanced or treatment refractory cervical cancer.