Molecular Imaging-Guided Sonodynamic Therapy

Magnetically actuated sonodynamic nanorobot collectives for potentiated ovarian cancer therapy

Ovarian cancer presents a substantial challenge due to its high mortality and recurrence rates among gynecological tumors. Existing clinical chemotherapy treatments are notably limited by drug resistance and systemic toxic side effects caused by off target drugs. Sonodynamic therapy (SDT) has emerged as a promising approach in cancer treatment, motivating researchers to explore synergistic combinations with other therapies for enhanced efficacy. In this study, we developed magnetic sonodynamic nanorobot (Fe3O4@SiO2-Ce6, FSC) by applying a SiO2 coating onto Fe3O4 nanoparticle, followed by coupling with the sonosensitizer Ce6. The magnetic FSC nanorobot collectives could gather at fixed point and actively move to target site regulated by magnetic field. In vitro experiments revealed that the magnetic FSC nanorobot collectives enabled directional navigation to the tumor cell area under guidance. Furthermore, under low-intensity ultrasonic stimulation, FSC nanorobot collectives mediated sonodynamic therapy exhibited remarkable anti-tumor performance. These findings suggest that magnetically actuated sonodynamic nanorobot collectives hold promising potential for application in target cancer therapy.

Cuproptosis: A novel therapeutic target for overcoming cancer drug resistance

Cuproptosis is a newly identified form of cell death driven by copper. Recently, the role of copper and copper triggered cell death in the pathogenesis of cancers have attracted attentions. Cuproptosis has garnered enormous interest in cancer research communities because of its great potential for cancer therapy. Copper-based treatment exerts an inhibiting role in tumor growth and may open the door for the treatment of chemotherapy-insensitive tumors. In this review, we provide a critical analysis on copper homeostasis and the role of copper dysregulation in the development and progression of cancers. Then the core molecular mechanisms of cuproptosis and its role in cancer is discussed, followed by summarizing the current understanding of copper-based agents (copper chelators, copper ionophores, and copper complexes-based dynamic therapy) for cancer treatment. Additionally, we summarize the emerging data on copper complexes-based agents and copper ionophores to subdue tumor chemotherapy resistance in different types of cancers. We also review the small-molecule compounds and nanoparticles (NPs) that may kill cancer cells by inducing cuproptosis, which will shed new light on the development of anticancer drugs through inducing cuproptosis in the future. Finally, the important concepts and pressing questions of cuproptosis in future research that should be focused on were discussed. This review article suggests that targeting cuproptosis could be a novel antitumor therapy and treatment strategy to overcome cancer drug resistance.

Mn(II)-hemoporfin-based metal-organic frameworks as a theranostic nanoplatform for MRI-guided sonodynamic therapy

Imaging-guided therapy holds great potential for enhancing therapeutic performance in a personalized way. However, it is still challenging to develop appropriate multifunctional materials to overcome the limitations of current all-in-one theranostic agents. In this study, we developed a one-for-all theranostic nanoplatform called Mn(II)-hemoporfin MOFs, designed specifically for MRI-guided sonodynamic tumor therapy. The formation of MOF structures not only improves imaging but also enhances therapeutic effects through collective actions. Furthermore, by modifying polyethylene glycol (PEG), Mn(II)-hemoporfin-PEG was able to enhance permeability and retention effects, ensuring long circulation in the blood and accumulation in the tumor. MRI enhancement provided by Mn(II)-hemoporfin-PEG remained localized at the tumor site, with Mn(II)-hemoporfin-PEG demonstrating 88.6% efficacy in sonodynamic therapy testing in vivo. Mn(II)-hemoporfin-PEG exhibits excellent longitudinal relaxation, MRI effects, and sonodynamic performance, making it a promising alternative for clinical cancer treatment.

Molecular imaging of tumour-associated pathological biomarkers with smart nanoprobe: From "Seeing" to "Measuring"

Although the extraordinary progress has been made in molecular biology, the prevention of cancer remains arduous. Most solid tumours exhibit both spatial and temporal heterogeneity, which is difficult to be mimicked in vitro. Additionally, the complex biochemical and immune features of tumour microenvironment significantly affect the tumour development. Molecular imaging aims at the exploitation of tumour-associated molecules as specific targets of customized molecular probe, thereby generating image contrast of tumour markers, and offering opportunities to non-invasively evaluate the pathological characteristics of tumours in vivo. Particularly, there are no "standard markers" as control in clinical imaging diagnosis of individuals, so the tumour pathological characteristics-responsive nanoprobe-based quantitative molecular imaging, which is able to visualize and determine the accurate content values of heterogeneous distribution of pathological molecules in solid tumours, can provide criteria for cancer diagnosis. In this context, a variety of "smart" quantitative molecular imaging nanoprobes have been designed, in order to provide feasible approaches to quantitatively visualize the tumour-associated pathological molecules in vivo. This review summarizes the recent achievements in the designs of these nanoprobes, and highlights the state-of-the-art technologies in quantitative imaging of tumour-associated pathological molecules.

Lipid bilayer-based biological nanoplatforms for sonodynamic cancer therapy

Sonodynamic therapy (SDT) has been developed as a promising alternative therapeutic modality for cancer treatment, involving the synergetic application of sonosensitizers and low-intensity ultrasound. However, the antitumor efficacy of SDT is significantly limited due to the poor performance of conventional sonosensitizers in vivo and the constrained tumor microenvironment (TME). Recent breakthroughs in lipid bilayer-based nanovesicles (LBBNs), including multifunctional liposomes, exosomes, and isolated cellular membranes, have brought new insights into the advancement of SDT. Despite their distinct sources and preparation methods, the lipid bilayer structure in common allows them to be functionalized in many comparable ways to serve as ideal nanocarriers against challenges arising from the tumor-specific sonosensitizer delivery and the complicated TME. In this review, we provide a comprehensive summary of the recent advances in LBBN-based SDT, with particular attention on how LBBNs can be engineered to improve the delivery efficiency of sonosensitizers and overcome physical, biological, and immune barriers within the TME for enhanced sonodynamic cancer therapy. We anticipate that this review will offer valuable guidance in the construction of LBBN-based nanosonosensitizers and contribute to the development of advanced strategies for next-generation sonodynamic cancer therapy.

Ferroptosis as a promising therapeutic strategy for melanoma

Malignant melanoma (MM) is the most common and deadliest type of skin cancer and is associated with high mortality rates across all races and ethnicities. Although present treatment options combined with surgery provide short-term clinical benefit in patients and early diagnosis of non-metastatic MM significantly increases the probability of survival, no efficacious treatments are available for MM. The etiology and pathogenesis of MM are complex. Acquired drug resistance is associated with a pool prognosis in patients with advanced-stage MM. Thus, these patients require new therapeutic strategies to improve their treatment response and prognosis. Multiple studies have revealed that ferroptosis, a non-apoptotic form of regulated cell death (RCD) characterized by iron dependant lipid peroxidation, can prevent the development of MM. Recent studies have indicated that targeting ferroptosis is a promising treatment strategy for MM. This review article summarizes the core mechanisms underlying the development of ferroptosis in MM cells and its potential role as a therapeutic target in MM. We emphasize the emerging types of small molecules inducing ferroptosis pathways by boosting the antitumor activity of BRAFi and immunotherapy and uncover their beneficial effects to treat MM. We also summarize the application of nanosensitizer-mediated unique dynamic therapeutic strategies and ferroptosis-based nanodrug targeting strategies as therapeutic options for MM. This review suggests that pharmacological induction of ferroptosis may be a potential therapeutic target for MM.

Recent Developments in PET and SPECT Radiotracers as Radiopharmaceuticals for Hypoxia Tumors

Hypoxia, a deficiency in the levels of oxygen, is a common feature of most solid tumors and induces many characteristics of cancer. Hypoxia is associated with metastases and strong resistance to radio- and chemotherapy, and can decrease the accuracy of cancer prognosis. Non-invasive imaging methods such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) using hypoxia-targeting radiopharmaceuticals have been used for the detection and therapy of tumor hypoxia. Nitroimidazoles are bioreducible moieties that can be selectively reduced under hypoxic conditions covalently bind to intracellular macromolecules, and are trapped within hypoxic cells and tissues. Recently, there has been a strong motivation to develop PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazole moieties for the visualization and treatment of hypoxic tumors. In this review, we summarize the development of some novel PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazoles, as well as their physicochemical properties, in vitro cellular uptake values, in vivo biodistribution, and PET/SPECT imaging results.

Recent Advances of 68Ga-Labeled PET Radiotracers with Nitroimidazole in the Diagnosis of Hypoxia Tumors

Positron emission tomography (PET) is a noninvasive molecular imaging method extensively applied in the detection and treatment of various diseases. Hypoxia is a common phenomenon found in most solid tumors. Nitroimidazole is a group of bioreducible pharmacophores that selectively accumulate in hypoxic regions of the body. Over the past few decades, many scientists have reported the use of radiopharmaceuticals containing nitroimidazole for the detection of hypoxic tumors. Gallium-68, a positron-emitting radioisotope, has a favorable half-life time of 68 min and can be conveniently produced by ⁶⁸Ge/⁶⁸Ga generators. Recently, there has been significant progress in the preparation of novel ⁶⁸Ga-labeled complexes bearing nitroimidazole moieties for the diagnosis of hypoxia. This review provides a comprehensive overview of the current status of developing ⁶⁸Ga-labeled radiopharmaceuticals with nitroimidazole moieties, their pharmacokinetics, and in vitro and in vivo studies, as well as PET imaging studies for hypoxic tumors.

The design of small-molecule prodrugs and activatable phototherapeutics for cancer therapy

Cancer remains as one of the most significant health problems, with approximately 19 million people diagnosed worldwide each year. Chemotherapy is a routinely used method to treat cancer patients. However, current treatment options lack the appropriate selectivity for cancer cells, are prone to resistance mechanisms, and are plagued with dose-limiting toxicities. As such, researchers have devoted their attention to developing prodrug-based strategies that have the potential to overcome these limitations. This tutorial review highlights recently developed prodrug strategies for cancer therapy. Prodrug examples that provide an integrated diagnostic (fluorescent, photoacoustic, and magnetic resonance imaging) response, which are referred to as theranostics, are also discussed. Owing to the non-invasive nature of light (and X-rays), we have discussed external excitation prodrug strategies as well as examples of activatable photosensitizers that enhance the precision of photodynamic therapy/photothermal therapy. Activatable photosensitizers/photothermal agents can be seen as analogous to prodrugs, with their phototherapeutic properties at a specific wavelength activated in the presence of disease-related biomarkers. We discuss each design strategy and illustrate the importance of targeting biomarkers specific to the tumour microenvironment and biomarkers that are known to be overexpressed within cancer cells. Moreover, we discuss the advantages of each approach and highlight their inherent limitations. We hope in doing so, the reader will appreciate the current challenges and available opportunities in the field and inspire subsequent generations to pursue this crucial area of cancer research.

Nanosensitizer-mediated unique dynamic therapy tactics for effective inhibition of deep tumors

X-ray and ultrasound waves are widely employed for diagnostic and therapeutic purposes in clinic. Recently, they have been demonstrated to be ideal excitation sources that activate sensitizers for the dynamic therapy of deep-seated tumors due to their excellent tissue penetration. Here, we focused on the recent progress in five years in the unique dynamic therapy strategies for the effective inhibition of deep tumors that activated by X-ray and ultrasound waves. The concepts, mechanisms, and typical nanosensitizers used as energy transducers are described as well as their applications in oncology. The future developments and potential challenges are also discussed. These unique therapeutic methods are expected to be developed as depth-independent, minimally invasive, and multifunctional strategies for the clinic treatment of various deep malignancies.

Newly developed gas-assisted sonodynamic therapy in cancer treatment

Sonodynamic therapy (SDT) is an emerging noninvasive treatment modality that utilizes low-frequency and low-intensity ultrasound (US) to trigger sensitizers to kill tumor cells with reactive oxygen species (ROS). Although SDT has attracted much attention for its properties including high tumor specificity and deep tissue penetration, its anticancer efficacy is still far from satisfactory. As a result, new strategies such as gas-assisted therapy have been proposed to further promote the effectiveness of SDT. In this review, the mechanisms of SDT and gas-assisted SDT are first summarized. Then, the applications of gas-assisted SDT for cancer therapy are introduced and categorized by gas types. Next, therapeutic systems for SDT that can realize real-time imaging are further presented. Finally, the challenges and perspectives of gas-assisted SDT for future clinical applications are discussed.

Ultrasound Molecular Imaging and Its Applications in Cancer Diagnosis and Therapy

Ultrasound imaging is regarded as a highly sensitive imaging modality used in routine clinical examinations. Over the last several decades, ultrasound contrast agents have been widely applied in ultrasound molecular cancer imaging to improve the detection, characterization, and quantification of tumors. To date, a few new potential preclinical and clinical applications regarding ultrasound molecular cancer imaging are being investigated. This review presents an overview of the various kinds of ultrasound contrast agents employed in ultrasound molecular imaging and advanced imaging techniques using these contrast agents. Additionally, we discuss the recent enormous development of ultrasound contrast agents in the relevant preclinical and clinical applications, highlight the recent challenges which need to be overcome to accelerate the clinical translation, and discuss the future perspective of ultrasound molecular cancer imaging using various contrast agents. As a highly promising and valuable tumor-specific imaging technique, it is believed that ultrasound molecular imaging will pave an accurate and efficient way for cancer diagnosis.

Ultrasound-dependent RNAi using TatU1A-rose bengal conjugate

Tat-U1A-rose bengal conjugate (TatU1A-RB) was prepared as an ultrasound-sensitive RNA carrier molecule. This molecule consists of Tat cell-penetrating peptide, U1A RNA-binding protein, and rose bengal as a sonosensitizer. We demonstrated that TatU1A-RB delivered RNA via the endocytosis pathway, which was followed by ultrasound-dependent endosomal escape and cytosolic dispersion of the RNA. A short hairpin RNA (shRNA) delivered by TatU1A-RB mediated RNA interference (RNAi) ultrasound-dependently. Even by ultrasound irradiation through blood cells, RNAi could be induced with TatU1A-RB and the shRNA. This ultrasound-dependent cytosolic RNA delivery method will serve as the basis for a new approach to nucleic acid therapeutics.