Programmable therapeutic nanoscale covalent organic framework for photodynamic therapy and hypoxia-activated cascade chemotherapy

Clinical photodynamic therapy (PDT) only has a limited cancer therapeutic effect and typically leads to a more hypoxic milieu owing to the hypoxic conditions of the solid tumor microenvironment that limit the singlet oxygen (¹O₂), generation. To address this issue, the PDT, in combination with hypoxia-activated prodrugs, has recently been investigated as a possible clinical treatment modality for cancer therapy. By cross-linking the photosensitizer tetra(4-hydroxyphenyl)porphine (THPP) and a ¹O₂-cleavable thioketal (TK) linker, a multifunctional nanoscale covalent organic framework (COF) platform with a high porphyrin loading capacity was synthesized, which significantly improve the reactive oxygen species (ROS) generation efficiency and contributes to PDT. As-synthesized THPP_TK-PEG nanoparticles (NPs) possess a high THPP photosensitizer content and mesoporous structure for further loading of the hypoxia-responsive prodrug banoxantrone (AQ4N) into the COF with a high-loading content. The nano-carriers surfaces are coated with a thick PEG coating to promote their dispersibility in physiological surroundings and therapeutic performance. When exposed to 660 nm radiation, such a nanoplatform can efficiently create cytotoxic ¹O₂ for PDT. Similarly, oxygen intake may exacerbate the hypoxic environment of the tumor, inducing the activation of AQ4N to achieve hypoxia-activated cascade chemotherapy and increased treatment efficacy. This study provides a new nanoplatform for photodynamic-chemical synergistic therapy and offers critical new insights for designing and developing a multifunctional supramolecular drug delivery system. STATEMENT OF SIGNIFICANCE: Here, we designed a laser-activated hypoxia-responsive nanoscale COF nanoplatform for hypoxia-activated cascade chemotherapy and PDT. When exposed to laser light, thus this nanoplatform can efficiently create cytotoxic ¹O₂ for PDT while consuming oxygen at the tumor location. However, increased oxygen consumption can exacerbate the tumor's hypoxic environment, causing AQ4N to become active, allowing for programmed hypoxia-triggered cascade chemotherapy and improved therapeutic efficacy. In addition, this innovative nanoscale COF nanoplatform allows for laser-controlled drug delivery in specific areas, which dramatically improves tumor inhibition. This research suggests a method for attaining ultrasensitive drug release and effective cascade therapy for cancer treatments.

Targeting Hypoxia: Hypoxia-Activated Prodrugs in Cancer Therapy

Hypoxia is an important characteristic of most solid malignancies, and is closely related to tumor prognosis and therapeutic resistance. Hypoxia is one of the most important factors associated with resistance to conventional radiotherapy and chemotherapy. Therapies targeting tumor hypoxia have attracted considerable attention. Hypoxia-activated prodrugs (HAPs) are bioreductive drugs that are selectively activated under hypoxic conditions and that can accurately target the hypoxic regions of solid tumors. Both single-agent and combined use with other drugs have shown promising antitumor effects. In this review, we discuss the mechanism of action and the current preclinical and clinical progress of several of the most widely used HAPs, summarize their existing problems and shortcomings, and discuss future research prospects.

Intratumoural Cytochrome P450 Expression in Breast Cancer: Impact on Standard of Care Treatment and New Efforts to Develop Tumour-Selective Therapies

Despite significant advances in treatment strategies over the past decade, selective treatment of breast cancer with limited side-effects still remains a great challenge. The cytochrome P450 (CYP) family of enzymes contribute to cancer cell proliferation, cell signaling and drug metabolism with implications for treatment outcomes. A clearer understanding of CYP expression is important in the pathogenesis of breast cancer as several isoforms play critical roles in metabolising steroid hormones and xenobiotics that contribute to the genesis of breast cancer. The purpose of this review is to provide an update on how the presence of CYPs impacts on standard of care (SoC) drugs used to treat breast cancer as well as discuss opportunities to exploit CYP expression for therapeutic intervention. Finally, we provide our thoughts on future work in CYP research with the aim of supporting ongoing efforts to develop drugs with improved therapeutic index for patient benefit.

A Cleverly Designed Novel Lipid Nanosystem: Targeted Retention, Controlled Visual Drug Release, and Cascade Amplification Therapy for Mammary Carcinoma in vitro

Objective

To construct an ideal theranostic nanoplatform (LIP3); to clarify its physicochemical properties; to confirm its characteristics of dual-modality imaging, active-targeting, and cascade amplification therapy for mammary carcinoma; and to perform a preliminary exploration of the cytotoxicity mechanism.

Design

A self-prepared liposome nanosystem, LIP3, can actively target 4T1 cells because the surface is linked with C-RGD. Haematoporphyrin monomethyl ether (HMME), an excellent sonosensitizer entrapped in the lipid bilayer, can function in photoacoustic imaging. Low-intensity focused ultrasound (LIFU) of ultrasound-targeted microbubble destruction (UTMD) promotes localized drug delivery into tumours because PFH, a phase-change substance, is loaded in the LIP3 core, achieving visualization of targeted drug release, and sonodynamic therapy (SDT) can kill tumour cells. SDT provides a favourable environment for AQ4N, resulting in amplification of LIP3 treatment. Therefore, LIP3 shows targeted aggregation and targeted release, integrating dual-mode imaging and precise treatment.

Results

The self-prepared lipid nanosystem, LIP3, meets the above expectations and has ideal physicochemical properties, with a regular sphere with uniform distribution. Contrast-enhanced ultrasound (CEUS), photoacoustic imaging, and bimodal imaging were effective in vitro. In 4T1 cell experiments, the cell capacity was as high as 42.9%, and the cytotoxicity to 4T1 was more than 5 times that of LIP1 (containing AQ4N only) and more than 2 times that of LIP2 (containing only HMME), achieving comparable results as cascade therapy for mammary cancer.

Conclusion

LIP3, a theranostic nanoplatform, was successfully constructed and conformed to the physicochemical characterization of ideal nanoparticles, with active-targeting, dual-modality imaging, visualized drug release, and precise treatment under the action of LIFU. SDT provides a favourable environment for AQ4N, resulting in amplification of LIP3 treatment. Therefore, LIP3 shows targeted aggregation and targeted release, integrating dual-mode imaging, and precise cascade treatment. This unique theranostic NPS with multiple capabilities is expected to be a favourable anti-cancer method in the future.

Programmable Therapeutic Nanodevices with Circular Amplification of H2 O2 in the Tumor Microenvironment for Synergistic Cancer Therapy

Tumor microenvironment activated nanodevices have remarkable superiority to enhance therapeutic efficacy and minimize side effects, but their practical applications are dramatically reduced by the low abundance and heterogeneous distribution of specific stimuli at the tumor site. Herein, programmable vesicular nanodevices based on the triblock copolymer containing poly(ethylene glycol) (PEG) and poly(caprolactone) (PCL) with peroxalate esters (PO) as hydrogen peroxide-responsive linkage (PEG-PO-PCL-PO-PEG), are developed for co-delivery of hypoxia-activated prodrug (AQ4N) and glucose oxidase (GOD). The obtained nanodevices (PAG) can be activated by the high level of H₂ O₂ in tumor microenvironment to improve the permeability of membranes for glucose entrance. Afterward, the oxidation of glucose catalyzed by GOD produces amplified H₂ O₂ amounts which in turn induce complete destruction of PAG for fast release of AQ4N and GOD. Ultimately, the PAG can exert programmable therapeutic effects from the following aspects: 1) starvation therapy by cutting off the energy supply from glucose through GOD catalysis; 2) oxidative cytotoxicity after H₂ O₂ amplification; 3) chemotherapy of AQ4N activated by the intensified tumor hypoxia microenvironment after oxygen consumption. The stimuli amplification, controlled drug release, synergistic therapy, and corresponding mechanisms of PAG are demonstrated. Therefore, the presented work could provide significant new insights for cancer treatment.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.