Synthesis and in vitro activities of new anticancer duplex drugs linking 2′-deoxy-5-fluorouridine (5-FdU) with 3′-C-ethynylcytidine (ECyd) via a phosphodiester bonding

Nucleoside dimers analogues with a 1,2,3-triazole linkage: conjugation of floxuridine and thymidine provides novel tools for cancer treatment. Part II

The fluorinated nucleoside dimers with a 1,2,3-triazole linkage are novel compounds within the field of bioorganic chemistry. We report on the synthesis and properties of two groups of nucleoside dimers analogs possessing a different arrangement of the 1,4-disubstituted 1,2,3-triazole linkage. Based on analysis of the ³J_HH, ³J_H1'C2, and ³J_H1'C6 we estimated conformational preferences of sugar part and orientation around glycosidic bond. These compounds show moderate anticancer activity, with cytostatic studies in three different cancer cell lines.

Chemosensitivity of various peritoneal cancer cell lines to HIPEC and PIPAC: comparison of an experimental duplex drug to standard drug regimens in vitro

We performed an in-vitro study testing the chemosensitivity of peritoneal cancer cell lines (SW620, HCT116, MKN45, 23,132/87, OAW42) to various cytostatic drug regimens. A duplex drug, characterized by reversible linking of the antimetabolites 2'-deoxy-5-fluorouridine (5-FdU) and 3'-C-ethynylcytidine (ECyd), was compared to oxaliplatin or to cisplatin plus doxorubicin. The experiments were designed to reflect the conditions of intraperitoneal chemotherapy. CASY® (Cell Analysis System) technology was used to compare the impact of incubation temperature/duration and drug concentration on the viability of the cancer cell lines versus normal human dermal fibroblasts. Two incubation scenarios were explored: (i) hyperthermic intraperitoneal chemotherapy (HIPEC) with 1 h of incubation at 42 °C, and (ii) pressurized intraperitoneal aerosol chemotherapy (PIPAC) with several successive incubations at 37 °C. Under HIPEC conditions, oxaliplatin induced a potent temperature-dependent growth inhibition of colon cancer cells not seen with the duplex drug. Under PIPAC conditions, the duplex drug achieved the same growth inhibition at a fraction of the dose level required with oxaliplatin. Gastric and ovarian cancer cells were more sensitive to cisplatin plus doxorubicin than to the duplex drug under PIPAC conditions. The duplex drug suggests itself, notably in cases of platinum resistance, as an alternative or addition to intraperitoneal chemotherapies when platinum-based PIPAC technology is used. Using it with HIPEC technology is not recommended. Higher doses of the duplex drug will enhance growth inhibition, albeit at the cost of a severely reduced difference in chemosensitivity between tumor and normal cells. Our findings provide orientation for PIPAC-based personalized intraperitoneal chemotherapy.

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.

Improving nucleoside analogs via lipid conjugation: Is fatter any better?

In the past few decades, nucleoside analog drugs have been used to treat a large variety of cancers. These anti-metabolite drugs mimic nucleosides and interfere with chain lengthening upon incorporation into the DNA or RNA of actively replicating cells. However, efficient delivery of these drugs is limited due to their pharmacokinetic properties, and tumors often develop drug resistance. In addition, nucleoside analogs are generally hydrophilic, resulting in poor bioavailability and impaired blood-brain barrier penetration. Conjugating these drugs to lipids modifies their pharmacokinetic properties and may improve in vivo efficacy. This review will cover recent advances in the field of conjugation of phospholipids to nucleoside analogs. This includes conjugation of myristic acid, 12-thioethyldodecanoic acid, 5-elaidic acid esters, phosphoramidate, and self-emulsifying formulations. Relevant in vitro and in vivo data will be discussed for each drug, as well as any available data from clinical trials.

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.

Sensitivity of gastric adenocarcinoma and normal cell lines against combined or conjugated antimetabolites

The in-vitro growth inhibition of cancer and normal cell lines caused by mixed or covalently linked antimetabolites should clarify whether the conjugation of antimetabolites influences cell sensitivity and growth inhibition in a manner that differs from an equimolar mixture of the same antimetabolites or not. Growth inhibition of the human gastric adenocarcinoma cell lines 23132/87 and MKN-45 in comparison with normal gastric intestinal CCL-241 and the dermal fibroblast cell line NHDF was evaluated using CASY technology. The cell lines were incubated with an equimolar mixture of 5-fluoro-2'-deoxyuridine (5FdU)+3'-C-ethynylcytidine (ECyd) or the covalently linked duplex drug 5FdU(5'→5')ECyd. The drug and metabolites of the assays and medium were determined semiquantitatively using high-performance liquid chromatography. The sensitivity of cancer and nonmalignant cell lines was clearly different against the duplex drug. A measure of 0.65 µmol/l 5FdU(5'→5')ECyd, for example, reduced the growth of MKN-45 or 23132/87 gastric cancer cells from 100% on day 0 to about 50 or 20% on day 10, respectively. However, under the same conditions, the growth of the nonmalignant NHDF and CCL-241 cell lines was not markedly inhibited. The cytostatic activity of the duplex drug is based on the active metabolites in and outside the cell formed by the degradation of 5FdU(5'→5')ECyd. The sensitivity of cell lines against the duplex drug depended on its ability to metabolize the duplex drug. 5FdU(5'→5')ECyd should be more advantageous for specific and efficient polychemotherapy of gastric cancer than the corresponding equimolar mixture of 5FdU+ECyd or a standard combination regime of single drugs.

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

PURPOSE

Duplex drugs are promising anticancer agents. After in vivo cleavage into active nucleoside analogues, they exert their anti-tumour activity with reduced toxicity and side effects. Here we evaluated the impact of two duplex drugs on the viability of hepatoblastoma (HB) cells lines and their toxicity against human fibroblasts.

METHODS

The duplex drugs 2'-deoxy-5-fluorouridylyl-(3'-5')- 3'-C-ethynylcytidine (5-FdU(3'-5')ECyd) and 3'-C-ethynylcytidinylyl-(5'→1-O)-2-O-octadecyl-sn-glycerylyl-(3'-Ο→5')-2'-deoxy-5-fluorouridine (ECyd-lipid-5-FdU) were analysed in two HB cell lines (HUH6, HepT1) and fibroblasts by MTT assay. The treatment potential was compared to the single substances 2'-deoxy-5-fluorourindine (5-FdU), 3'-C-ethynylycytidine (ECyd) and an equimolar mixture of both. Cell cycle analyses were performed using flow cytometry after 7-AAD staining.

RESULTS

Both duplex drugs achieve a potent cytotoxic effect at low μM concentrations, which was more pronounced than the mixture of ECyd + 5-FdU. Further, both substances exert toxicity on fibroblasts of tumour samples, with less toxicity in foreskin fibroblasts cultures. Cell cycle analyses revealed a shift towards apoptotic cells for both drugs in HB cells.

CONCLUSION

5-FdU(3'-5')ECyd and ECyd-lipid-5-FdU exert a highly potent anti-tumoural effect on HB cells and might therefore be a treatment option in HB. Pharmacological formulations of both duplex drugs have to be evaluated in vivo to reduce possible side effects.

Cytotoxicity of new duplex drugs linking 3'-C-ethynylcytidine and 5-fluor-2'-deoxyuridine against human melanoma cells

Melanoma is an increasingly common and potentially fatal malignancy of the skin and some mucous membranes. As no cure exists for metastatic disease, there is an urgent need for novel drugs. 2'-Deoxy-5-fluorouridylyl-(3'-5')-3'-C-ethynylcytidine [5-FdU(3'-5')ECyd] and 3'-C-ethynylcytidinylyl-(5' → 1-O)-2-O-octadecyl-sn-glycerylyl-(3-O → 5')-2'-deoxy-5-fluorouridine [ECyd-lipid-5-FdU] represent cytostatic active duplex drugs, which can be metabolized into various active antimetabolites. We evaluated the cytotoxicity of these heterodinucleoside phosphate analogs, their corresponding monomers ECyd and 5-FdU and combinations thereof on six metastatic melanoma cell lines and six ex vivo patient-derived melanoma cells in comparison to current standard cytostatic agents and the BRAF V600E inhibitor Vemurafenib. In vitro (real-time)-proliferation assays demonstrated that 5-FdU(3'-5')ECyd and ECyd-lipid-5-FdU had a high cytotoxic efficacy causing 75% melanoma cell death at concentrations in the nanomolar and micromolar range. Cytotoxicity was conducted by induction of DNA cleavage indicating apoptotic cells. Chicken embryotoxicity demonstrated that the duplex drugs were less toxic than 5-FdU at 0.01 μM. In vivo the duplex drug 5-FdU(3'-5')ECyd was efficacious in the murine LOX IMVI melanoma xenograph model on administration of 11.2 mg/kg/injection every fourth day. Both duplex drugs are promising novel cytostatic agents for the treatment of malignant melanoma meriting clinical evaluation.

Acceptance of oral chemotherapy in breast cancer patients - a survey study

Background

Oral (p.o.) chemotherapy treatments gained increasing importance in the palliative treatment of metastatic breast cancer (MBC). Aim of this survey was to evaluate the acceptance of p.o. treatment and patients' individual attitudes towards it.

Methods

A specific 14 item-questionnaire was designed. Patients suffering from breast cancer receiving a newly launched p.o. or i.v. chemotherapy treatment were prospectively evaluated during 4 months of time. 224 questionnaires using descriptive statistics, chi-square test, Spearman correlation were evaluated.

Results

Patients' median age was 54 years, 164 received i.v., 60 p.o therapy. 89% with p.o. and 67% with i.v. regimens would choose p.o. over i.v. therapy, if equal efficacy is guaranteed. Significant differences were especially found in terms of personal benefit (55% i.v., 92% p.o.), reduced feeling of being ill due to p.o. treatment (26% i.v., 65% p.o.), better coping with disease due to p.o. therapy (36% i.v., 68% p.o.). Side effects were significantly less often reported under p.o. treatment (19% p.o. vs. 53% i.v.)

Conclusion

P.o. chemotherapy shows a high acceptance in MBC patients under palliative therapy. Compliance can be achieved in particular through a differentiated indication, patient education and competent support along a p.o. treatment.

Cellular pharmacology of multi- and duplex drugs consisting of ethynylcytidine and 5-fluoro-2'-deoxyuridine

Prodrugs can have the advantage over parent drugs in increased activation and cellular uptake. The multidrug ETC-L-FdUrd and the duplex drug ETC-FdUrd are composed of two different monophosphate-nucleosides, 5-fluoro-2′deoxyuridine (FdUrd) and ethynylcytidine (ETC), coupled via a glycerolipid or phosphodiester, respectively. The aim of the study was to determine cytotoxicity levels and mode of drug cleavage. Moreover, we determined whether a liposomal formulation of ETC-L-FdUrd would improve cytotoxic activity and/or cleavage. Drug effects/cleavage were studied with standard radioactivity assays, HPLC and LC-MS/MS in FM3A/0 mammary cancer cells and their FdUrd resistant variants FM3A/TK⁻. ETC-FdUrd was active (IC₅₀ of 2.2 and 79 nM) in FM3A/0 and TK⁻ cells, respectively. ETC-L-FdUrd was less active (IC₅₀: 7 nM in FM3A/0 vs 4500 nM in FM3A/TK⁻). Although the liposomal formulation was less active than ETC-L-FdUrd in FM3A/0 cells (IC₅₀:19.3 nM), resistance due to thymidine kinase (TK) deficiency was greatly reduced. The prodrugs inhibited thymidylate synthase (TS) in FM3A/0 cells (80–90%), but to a lower extent in FM3A/TK⁻ (10–50%). FdUMP was hardly detected in FM3A/TK⁻ cells. Inhibition of the transporters and nucleotidases/phosphatases resulted in a reduction of cytotoxicity of ETC-FdUrd, indicating that this drug was cleaved outside the cells to the monophosphates, which was verified by the presence of FdUrd and ETC in the medium. ETC-L-FdUrd and the liposomal formulation were neither affected by transporter nor nucleotidase/phosphatase inhibition, indicating circumvention of active transporters. In vivo, ETC-FdUrd and ETC-L-FdURd were orally active. ETC nucleotides accumulated in both tumor and liver tissues. These formulations seem to be effective when a lipophilic linker is used combined with a liposomal formulation.