Radiation- and photo-induced activation of 5-fluorouracil prodrugs as a strategy for the selective treatment of solid tumors

Review of Prodrug and Nanodelivery Strategies to Improve the Treatment of Colorectal Cancer with Fluoropyrimidine Drugs

Fluoropyrimidine (FP) drugs are central components of combination chemotherapy regimens for the treatment of colorectal cancer (CRC). FP-based chemotherapy has improved survival outcomes over the last several decades with much of the therapeutic benefit derived from the optimization of dose and delivery. To provide further advances in therapeutic efficacy, next-generation prodrugs and nanodelivery systems for FPs are being developed. This review focuses on recent innovative nanodelivery approaches for FP drugs that display therapeutic promise. We summarize established, clinically useful FP prodrug strategies, including capecitabine, which exploit tumor-specific enzyme expression for optimal anticancer activity. We then describe the use of FP DNA-based polymers (e.g., CF10) for the delivery of activated FP nucleotides as a nanodelivery approach with proven activity in pre-clinical models and with clinical potential. Multiple nanodelivery systems for FP delivery show promise in CRC pre-clinical models and we review advances in albumin-mediated FP delivery, the development of mesoporous silica nanoparticles, emulsion-based nanoparticles, metal nanoparticles, hydrogel-based delivery, and liposomes and lipid nanoparticles that display particular promise for therapeutic development. Nanodelivery of FPs is anticipated to impact CRC treatment in the coming years and to improve survival for cancer patients.

Major advances in targeted protein degradation: PROTACs, LYTACs, and MADTACs

Of late, targeted protein degradation (TPD) has surfaced as a novel and innovative chemical tool and therapeutic modality. By co-opting protein degradation pathways, TPD facilitates complete removal of the protein molecules from within or outside the cell. While the pioneering Proteolysis-Targeting Chimera (PROTAC) technology and molecular glues hijack the ubiquitin-proteasome system, newer modalities co-opt autophagy or the endo-lysosomal pathway. Using this mechanism, TPD is posited to largely expand the druggable space far beyond small-molecule inhibitors. In this review, we discuss the major advances in TPD, highlight our current understanding, and explore outstanding questions in the field.

Development of a hypoxic nanocomposite containing high-Z element as 5-fluorouracil carrier activated self-amplified chemoradiotherapy co-enhancement

The synergetic effect of chemoradiotherapy achievement is encouraging but significantly hampered by the prevalence of hypoxia, leading to drug/radiation resistance in solid tumours. To address the problem and improve the efficiency of cancer therapy, a lamellar-structure multifunctional graphene oxide (GO) drug-delivery system with an average size of 243 nm, co-delivering of metronidazole (MI), 5-fluorouracil (5-FU) and FePt magnetic nanoparticles (MNPs), was successfully designed and synthesized in the study. The integration of hypoxic drug carrier loading radiosensitizers and chemotherapeutic drugs simultaneously, combines the properties of hypoxia-sensitivity and chemoradiotherapy co-enhancement within a single nanoplatform, which is expected to provide new ideas for cancer treatment. Through in vitro tests, the hypoxia-sensitivity and cytotoxicity of intracellular reactive oxygen species (ROS) of the nanocomposites (NCs) were proved. Moreover, the additive effect between MI, 5-FU and FePt MNPs in cytotoxicity and radiation sensitization aspects is disclosed. It performs an enhanced cell proliferation inhibition and makes up a self-amplified radiotherapy enhancement system that improves radiation efficiency and cell radiosensitivity simultaneously. In conclusion, the study recommended a novel and promising multifunctional nanoplatform which performed a self-amplified effect that activated chemoradiotherapy co-enhancement.

Using high harmonic radiation to reveal the ultrafast dynamics of radiosensitiser molecules

5-Fluorouracil (5FU) is a radiosensitiser molecule routinely used in combined chemo- and radio-therapies to enhance and localize cancer treatments. We have employed ultra-short XUV pulses produced by high harmonic generation (HHG) as a pump pulse to study the dynamics underlying the photo-stability and the radiation damage of this molecule. This work shows that it is possible to resolve individual dynamics even when using unselected HH. By comparing the results with those obtained in the multiphoton absorption at 400 nm, we were able to identify the frequencies of the HH comb relevant to the recorded dynamics: HH5 and HH3. The latter excites a high-lying Rydberg state interacting with a valence state and its dynamics is revealed by a 30 fs decay signal in the parent ion transient. Our results suggest that the same photoprotection mechanisms as those conferring photostability to the neutral nucleobases and to the DNA appear to be activated: HH5 excites the molecule to a state around 10.5 eV that undergoes an ultrafast relaxation on a timescale of 30 fs due to nonadiabatic interactions. This is followed sequentially by a 2.3 ps internal conversion as revealed by the dynamics observed for another fragment ion. These dynamics are extracted from the fragment ion signals. Proton or hydrogen transfer processes are required for the formation of three fragments and we speculate that the time scale of one of the processes is revealed by a H⁺ transient signal.

Short oligonucleotide prodrug having 5-fluoro and 5-iodouracil inhibits the proliferation of cancer cells in a photo-responsive manner

Photo-induced C1' hydrogen abstraction of 5-fluoro-2'-deoxyuridine was adopted as the key reaction for releasing 5-fluorouracil (5-FU) anticancer drug from oligonucleotide strands. After photoirradiation following 5-FU release, anticancer activity was expected. We demonstrated that oligonucleotide tetramer, d(A(F)U(I)UA), can release 5-FU under physiological conditions in a photo-responsive manner thorough photo-induced C1' hydrogen abstraction, and that the 5-FU released from d(A(F)U(I)UA) having a phosphorothioate backbone clearly suppresses the proliferation of HeLa cells in a photo-responsive manner.

Multifunctional magnetic fluorescent hybrid nanoparticles as carriers for the hydrophobic anticancer drug 5-fluorouracil

In this paper fluorescent magnetic Fe(3)O(4)@m-SiO(2)@YPO(4):Tb(3+) particles with a size of 52 nm have been prepared and characterized. The surface of the nanoparticles was modified with β-cyclodextrin and folic acid using glutathione as a linker. The hydrophobic anticancer drug 5-fluorouracil (5-FU) was successfully loaded on the fluorescent magnetic nanoparticles via formation of the 5-FU-CD inclusion complex. The overall size of the drug conjugate is 71 nm and the particles are highly stable in an aqueous medium without any deterioration of HD size. The drug conjugate favors more release at lower pH owing to instability of the 5-FU-CD inclusion complex. These results demonstrate that the developed multifunctional nanocomposite can be potentially used in magnetically guided delivery of 5-FU.

Aggregate formation and radiolytic degradation of amphiphilic DNA block copolymer possessing disulfide bond

We have designed a novel aggregate of DNA block copolymer (DBC) that is sensitive to hypoxic X-irradiation. The DBC consists of tetrahydropyrane-protected 2-hydroxyethyl methacrylate as a hydrophobic unit and oligodeoxynucleotides as a hydrophilic unit, which are linked to a radiation-sensitive disulfide bond. The DBC self-assembled efficiently to form aggregates that encapsulated small molecules such as nile red and pyrene. Hypoxic X-irradiation could then induce reductive degradation of the DBC aggregates via an exchange reaction of the disulfide bond to release guest molecules.

Radiolytic Reduction Characteristics of Artificial Oligodeoxynucleotides Possessing 2-Oxoalkyl Group or Disulfide Bonds

A number of advances have been made in the development of modified oligodeoxynucleotides (ODNs), and chemical or physical properties of which are controlled by external stimuli. These intelligent ODNs are promising for the next generation of gene diagnostics and therapy. This paper focuses on the molecular design of artificial ODNs that are activated by X-irradiation and their applications to regulation of hybridization properties, conformation change, radiation-activated DNAzyme, and decoy molecules.