Nanobubbles Containing sPD-1 and Ce6 Mediate Combination Immunotherapy and Suppress Hepatocellular Carcinoma in Mice

Strategies to enhance the therapeutic efficacy of anti-PD-1 antibody, anti-PD-L1 antibody and anti-CTLA-4 antibody in cancer therapy

Although immune checkpoint inhibitors (anti-PD-1 antibody, anti-PD-L1 antibody, and anti-CTLA-4 antibody) have displayed considerable success in the treatment of malignant tumors, the therapeutic effect is still unsatisfactory for a portion of patients. Therefore, it is imperative to develop strategies to enhance the effect of these ICIs. Increasing evidence strongly suggests that the key to this issue is to transform the tumor immune microenvironment from a state of no or low immune infiltration to a state of high immune infiltration and enhance the tumor cell-killing effect of T cells. Therefore, some combination strategies have been proposed and this review appraise a summary of 39 strategies aiming at enhancing the effectiveness of ICIs, which comprise combining 10 clinical approaches and 29 foundational research strategies. Moreover, this review improves the comprehensive understanding of combination therapy with ICIs and inspires novel ideas for tumor immunotherapy.

Nanomaterials-based precision sonodynamic therapy enhancing immune checkpoint blockade: A promising strategy targeting solid tumor

Burgeoning is an evolution from conventional photodynamic therapy (PDT). Thus, sonodynamic therapy (SDT) regulated by nanoparticles (NPs) possesses multiple advantages, including stronger penetration ability, better biological safety, and not reactive oxygen species (ROS)-dependent tumor-killing effect. However, the limitation to tumor inhibition instead of shrinkage and the incapability of eliminating metastatic tumors hinder the clinical potential for SDT. Fortunately, immune checkpoint blockade (ICB) can revive immunological function and induce a long-term immune memory against tumor rechallenges. Hence, synergizing NPs-based SDT with ICB can provide a promising therapeutic outcome for solid tumors. Herein, we briefly reviewed the progress in NPs-based SDT and ICB therapy. We highlighted the synergistic anti-tumor mechanisms and summarized the representative preclinical trials on SDT-assisted immunotherapy. Compared to other reviews, we provided comprehensive and unique perspectives on the innovative sonosensitizers in each trial. Moreover, we also discussed the current challenges and future corresponding solutions.

Delivery of sPD1 gene by anti-CD133 antibody conjugated microbubbles combined with ultrasound for the treatment of cervical cancer in mice

To explore new therapeutic options for cervical cancer, the inhibitory effect on cervical cancer of targeted CD133-loaded sPD1 gene microbubbles (MBs) combined with low-frequency ultrasound was studied and its mechanism was explored. We prepared microbubbles conjugated with anti-CD133 antibody to deliver the sPD1 gene and determined concentration, particle size, and potentials of MBs. In addition, we verified that CD133 targeted-MBs could specifically bind to U14 cervical cancer cells in vitro. A mouse model of subcutaneous xenograft cervical cancer was established and mice were divided into a control group, an non-targeted microbubble group, a CD133-MBs group, an sPD1-MBs group and a CD133/sPD1-MBs group. Compared with the control group, tumor growth was inhibited in each group, with the CD133/sPD1 group showing the strongest inhibitory effect after treatment. The tumor volume and weight inhibition rates in the CD133/sPD1-MBs group were 78.01% and 72.25% respectively, which were statistically different from the other groups (P < 0.05), and HE staining and TUNEL immunofluorescence showed necrosis and apoptosis in tumor tissue. Flow cytometry, lactate dehydrogenase, and indirect immunofluorescence experiments showed that T lymphocytes were activated and a large number of CD8-positive T cells infiltrated the tumor tissue after treatment, with the CD133/sPD1-MBs group showing the most prominent effects (P < 0.05). The combination of ultrasound with anti- CD133 antibody-conjugated microbubbles loaded with the sPD1 gene can inhibit the growth of cervical cancer, suggesting that the immunosuppressive microenvironment of the tumor is improved after treatment.

Enhancement of sonodynamic treatment of ovarian cancer based on Pt-B-P ternary nanoparticles

Sonodynamic therapy (SDT) can noninvasively focus sound energy to deep tumor tissues and activate sonosensitizer (such as chlorin e6(Ce6)) to produce antitumor effects. However, due to the hypoxic microenvironment of the tumor, the effect of sonodynamic therapy is limited. In this work, we successfully synthesized Platinum-Boron-Phosphorus ternary nanoparticles (Pt-B-P NPs) for the first time to efficiently catalyze the decomposition of hydrogen peroxide (H₂O₂) in tumor tissues to produce sufficient oxygen (O₂) and improve the effect of sonodynamic treatment of ovarian cancer. In vitro studies, we found that compared with Platinum nanoparticles (Pt NPs), Pt-B-P NPs have the significantly increased ability to catalyze the decomposition of H₂O₂ to produce oxygen and thus the hypoxic environment of tumor cells could be improved efficiently. Meanwhile, the bio-distribution, therapeutic effect and bio-safety of Pt-B-P NPs in vivo were evaluated using BALB/c-nu mouse model of ovarian cancer and the desired result had been achieved.

Recent advances in sonodynamic immunotherapy

Tumor immunotherapy has become an important means of tumor therapy by enhancing the immune response and triggering the activation of immune cells. However, currently, only a small number of patients respond to immunotherapy alone, and patients may experience immune-related adverse events (irAEs) during the course of treatment. Sonodynamic therapy (SDT) can produce cytotoxic substances to tumor tissue, induce apoptosis and enhance immunity. SDT combined with immunotherapy is considered a promising strategy for cancer treatment. In this mini review, we summarize the role of SDT in immunotherapy in recent years, including the application of SDT-triggered immunotherapy and the combination of SDT and immunotherapy.

Microbubbles for human diagnosis and therapy

Microbubbles (MBs) were observed for the first time in vivo as a curious consequence of quick saline injection during ultrasound (US) imaging of the aortic root, more than 50 years ago. From this serendipitous event, MBs are now widely used as contrast enhancers for US imaging. Their intrinsic properties described in this review, allow a multitude of designs, from shell to gas composition but also from grafting targeting agents to drug payload encapsulation. Indeed, the versatile MBs are deeply studied for their dual potential in imaging and therapy. As presented in this paper, new generations of MBs now opens perspectives for targeted molecular imaging along with the development of new US imaging systems. This review also presents an overview of the different therapeutic strategies with US and MBs for cancer, cardiovascular diseases, and inflammation. The overall aim is to overlap those fields in order to find similarities in the MBs application for treatment enhancement associated with US. To conclude, this review explores the new scales of MBs technologies with nanobubbles development, and along concurrent advances in the US imaging field. This review ends by discussing perspectives for the booming future uses of MBs.

[Comparison of three commercial photosensitizers for efficiency of inducing immunogenic cell death in anti-tumor immunotherapy]

OBJECTIVE

To compare 3 commercial immunogenic cell death (ICD) inducers, namely Chlorin e6 (Ce6), Neutral Red (NR), and Rose Bengal Sodium salt (RB), for their photosensitive properties, efficacy for photodynamic therapy (PDT) and ICD induction efficiency in antitumor immunotherapy.

METHODS

Reactive oxygen species (ROS) probes were used to evaluate the photosensitivity of the 3 ICD inducers, and their capacity for inducing intracellular ROS production was evaluated using a DCFH-DA probe. The cytotoxicity and biocompatibility of the 3 photosensitizers were compared using a CCK-8 kit, and their ICD-inducing efficiency was assessed by detecting the levels of surface-exposed calreticulin (ecto-CRT), high mobility group protein 1 (HMGB1) and adenosine triphosphate (ATP). In the animal experiment, BALB/c mouse models bearing 4T1 cellderived subcutaneous tumor were given intratumoral injection of Ce6 or NR solution (30 μL, 5 mg/mL), followed 2 h later by white light irradiation for 10 min (400 mW/cm²). Body weight and tumor size changes of the mice were monitored, and the percentage of CD8⁺ T cells in the tumor and IFN-γ⁺ CD8⁺ T cells in the spleen were analyzed by flow cytometry 14 days after the treatment. HE and TUNEL staining was used to analyze tumor cell apoptosis in the mice.

RESULTS

Among the 3 photosensitizers, Ce6 exhibited the strongest ROS-inducing capability and killing effect on the tumor cells. The results of ectoCRT, HMGB1 and ATP level detection all demonstrated a stronger ICD induction ability of Ce6. In the tumor-bearing mice, the tumor growth in Ce6 and NR groups was significantly inhibited after the treatment. The percentages of CD8⁺ T cells and IFN-γ⁺ CD8⁺ T cells were 12.7% and 7.1% in Ce6 group, respectively, significantly higher than those in NR group (6.1% and 2.8%, respectively; P < 0.05). HE and TUNEL staining revealed obvious tumor cell apoptosis in the tumor tissues in both Ce6 and NR groups, but the therapeutic effect was more prominent in Ce6 group.

CONCLUSION

Among the 3 photosensitizers, Ce6 has the highest efficiency for inducing ROS production with the strongest PDT efficacy and ICD induction capability. Ce6 can also increase the number and function of CD8⁺ T cells in anti-tumor immunotherapy to initiate robust adaptive immune response.

Nanobubble-mediated co-delivery of Ce6 and miR-195 for synergized sonodynamic and checkpoint blockade combination therapy with elicitation of robust immune response in hepatocellular carcinoma

MicroRNAs (miRNAs) is the tiny and highly conserved noncoding RNAs, regulate gene expression at the post-transcriptional level by binding to the 3'-UTR of target mRNAs. Several studies found that miR-195 plays an unavoidable role in the regulation of cell proliferation, cycle and apoptosis in hepatocellular carcinoma (HCC). Here, we constructed miR-195 and Chlorine e6 (Ce6) co-loading NBs (nanobubbles), making use of NBs as carriers to deliver miR-195 and Ce6 to mouse tumor models. Our results showed that the binding between PD-1 and PD-L1 was blocked by upregulating miR-195 expression. The analysis of CTL (Cytotoxic T Cell) immune activity in the treatment group was higher than the control group. Simultaneously, Ce6 was used as sonosensitizer to induce SDT (sonodynamic therapy) and trigger ICD (immunogenic cell death) of tumor cell via generation of ROS. Recent studies have found that ICD may further enhance anti-tumor immunity against PD-L1. Results indicated that combination treatment effectively stimulated infiltration of T cell and the activation of natural killer (NK) cells as well as the maturation of dendritic cells (DCs), and the combination treatment group exibited the highest CTL killing activity. These results indicate that a stronger antitumor immunity was triggered via combination of SDT-induced tumor cell ICD and immune checkpoint blockade of PD-1/PD-L1 mediated by upregulation of miR-195. In conclusion, we have successfully constructed an efficient delivery system with great potential to provide a new strategy for synergistic immunotherapy.

Nanobubble-based anti-hepatocellular carcinoma therapy combining immune check inhibitors and sonodynamic therapy

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, posing a global threat to human healthcare, and current approved treatment strategies do not produce satisfactory outcomes. Here, nanobubbles (NBs) were prepared that carried Immune Check Inhibitors (ICIs), PD-L1 antibody (PD-L1 Ab) and sonodynamic agent CHLORIN E6 (Ce₆); the anti-cancer properties of these NBs were analyzed from the point of view of immune and sonodynamic therapies. The PD-L1 Ab/Ce₆-NBs could inhibit tumor growth through regulating reactive oxygen species (ROS) production, apoptosis, and most importantly, the function of associated immunocytes, including natural killer cells and lymphocytes. The tumor tissues highly expressed markers of immunogenic tumor cell death (ICD) in which the expression of calreticulin (CRT) and ICD-related immune cytokines (CD80, CD86, INF-γ, and IL-2) were increased in PD-L1 Ab/Ce₆-NB treated mice. PD-L1 Ab/Ce₆-NBs also promoted murine spleen lymphocyte proliferation and cytotoxic activity, as well as CD8+ T cell infiltration in the tumor tissues, and downregulation of the PD-L1 protein and mRNA expression. Furthermore, Bax expression was increased and Bcl-2 was inhibited at the mRNA and protein levels in a murine subcutaneous transplanted tumor model. These results indicate that PD-L1 Ab/Ce₆-NBs can induce ROS-dependent ICD to further boost anti-cancer immune responses under the action of targeting the PD-1/PD-L1 immune check point in the tumor microenvironment as a promising therapeutic agent for HCC.

Rational Nanomedicine Design Enhances Clinically Physical Treatment-Inspired or Combined Immunotherapy

Independent of tumor type and non-invasive or minimally-invasive feature, current physical treatments including ultrasound therapy, microwave ablation (MWA), and radiofrequency ablation (RFA) are widely used as the local treatment methods in clinics for directly killing tumors and activating systematic immune responses. However, the activated immune responses are inadequate and incompetent for tumor recession, and the incomplete thermal ablation even aggravates the immunosuppressive tumor microenvironment (ITM), resulting in the intractable tumor recurrence and metastasis. Intriguingly, nanomedicine provides a powerful platform as they can elevate energy utilization efficiency and augment oncolytic effects for mitigating ITM and potentiating the systematic immune responses. Especially after combining with clinical immunotherapy, the anti-tumor killing effect by activating or enhancing the human anti-tumor immune system is reached, enabling the effective prevention against tumor recurrence and metastasis. This review systematically introduces the cutting-edge progress and direction of nanobiotechnologies and their corresponding nanomaterials. Moreover, the enhanced physical treatment efficiency against tumor progression, relapse, and metastasis via activating or potentiating the autologous immunity or combining with exogenous immunotherapeutic agents is exemplified, and their rationales are analyzed. This review offers general guidance or directions to enhance clinical physical treatment from the perspectives of immunity activation or magnification.

Application of nanosonosensitizer materials in cancer sono-dynamic therapy

Sonodynamic therapy (SDT) is a novel non-invasive treatment for cancer combining low-intensity ultrasound and sonosensitizers. SDT activates sonosensitizers through ultrasound, releasing energy and generating reactive oxygen species to kill tumor cells. Compared with traditional photodynamic therapy (PDT), SDT is a promising anti-cancer therapy with the advantages of better targeting, deeper tissue penetration, and higher focusing ability. With the development and broad application of nanomaterials, novel sonosensitizers with tumor-targeting specificity can deliver to deep tumors and enhance the tumor microenvironment. In this review, we first review the mechanisms of sonodynamic therapy. In addition, we also focus on the current types of sonosensitizers and the latest design strategies of nanomaterials in sonosensitizers. Finally, we summarize the combined strategy of sonodynamic therapy.

Exploring chitosan-shelled nanobubbles to improve HER2 + immunotherapy via dendritic cell targeting

Immunotherapy is a valuable approach to cancer treatment as it is able to activate the immune system. However, the curative methods currently in clinical practice, including immune checkpoint inhibitors, present some limitations. Dendritic cell vaccination has been investigated as an immunotherapeutic strategy, and nanotechnology-based delivery systems have emerged as powerful tools for improving immunotherapy and vaccine development. A number of nanodelivery systems have therefore been proposed to promote cancer immunotherapy. This work aims to design a novel immunotherapy nanoplatform for the treatment of HER2 + breast cancer, and specially tailored chitosan-shelled nanobubbles (NBs) have been developed for the delivery of a DNA vaccine. The NBs have been functionalized with anti-CD1a antibodies to target dendritic cells (DCs). The NB formulations possess dimensions of approximately 300 nm and positive surface charge, and also show good physical stability up to 6 months under storage at 4 °C. In vitro characterization has confirmed that these NBs are capable of loading DNA with good encapsulation efficiency (82%). The antiCD1a-functionalized NBs are designed to target DCs, and demonstrated the ability to induce DC activation in both human and mouse cell models, and also elicited a specific immune response that was capable of slowing tumor growth in mice in vivo. These findings are the proof of concept that loading a tumor vaccine into DC-targeted chitosan nanobubbles may become an attractive nanotechnology approach for the future immunotherapeutic treatment of cancer.

Advances and prospects of ultrasound targeted drug delivery systems using biomaterial-modified micro/nanobubbles for tumor therapy

The incidence of malignant tumors is rising rapidly and tends to be in the younger, which has been one of the most important factors endangering the safety of human life. Ultrasound micro/nanobubbles, as a noninvasive and highly specific antitumor strategy, can reach and destroy tumor tissue through their effects of cavitation and acoustic perforation under the guidance of ultrasound. Meanwhile, micro/nanobubbles are now used as a novel drug carrier, releasing drugs at a target region, especially on the prospects of biomaterial-modified micro/nanobubbles as a dual modality for drug delivery and therapeutic monitoring. and successful evaluation of the sonoporation mechanism(s), ultrasound parameters, drug type and dose will need to be addressed before translating this technology for clinical use. Therefore, this paper collects the literature on the experimental and clinical studies of ultrasound biomaterial-modified micro/nanobubbles therapy in vitro and in vivo in recent years.

Biological Characteristics and Clinical Significance of Soluble PD-1/PD-L1 and Exosomal PD-L1 in Cancer

The immune checkpoint pathway consisting of the cell membrane-bound molecule programmed death protein 1 (PD-1) and its ligand PD-L1 has been found to mediate negative regulatory signals that effectively inhibit T-cell proliferation and function and impair antitumor immune responses. Considerable evidence suggests that the PD-1/PD-L1 pathway is responsible for tumor immune tolerance and immune escape. Blockage of this pathway has been found to reverse T lymphocyte depletion and restore antitumor immunity. Antagonists targeting this pathway have shown significant clinical activity in specific cancer types. Although originally identified as membrane-type molecules, several other forms of PD-1/PD-L1 have been detected in the blood of cancer patients, including soluble PD-1/PD-L1 (sPD-1/sPD-L1) and exosomal PD-L1 (exoPD-L1), increasing the composition and functional complications of the PD-1/PD-L1 signaling pathway. For example, sPD-1 has been shown to block the PD-1/PD-L immunosuppressive pathway by binding to PD-L1 and PD-L2, whereas the role of sPD-L1 and its mechanism of action in cancer remain unclear. In addition, many studies have investigated the roles of exoPD-L1 in immunosuppression, as a biomarker for tumor progression and as a predictive biomarker for response to immunotherapy. This review describes the molecular mechanisms underlying the generation of sPD-1/sPD-L1 and exoPD-L1, along with their biological activities and methods of detection. In addition, this review discusses the clinical importance of sPD-1/sPD-L1 and exoPD-L1 in cancer, including their predictive and prognostic roles and the effects of treatments that target these molecules.

Combination of Ablation and Immunotherapy for Hepatocellular Carcinoma: Where We Are and Where to Go

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide and is increasing in incidence. Local ablative therapy plays a leading role in HCC treatment. Radiofrequency (RFA) is one of the first-line therapies for early local ablation. Other local ablation techniques (e.g., microwave ablation, cryoablation, irreversible electroporation, phototherapy.) have been extensively explored in clinical trials or cell/animal studies but have not yet been established as a standard treatment or applied clinically. On the one hand, single treatment may not meet the needs. On the other hand, ablative therapy can stimulate local and systemic immune effects. The combination strategy of immunotherapy and ablation is reasonable. In this review, we briefly summarized the current status and progress of ablation and immunotherapy for HCC. The immune effects of local ablation and the strategies of combination therapy, especially synergistic strategies based on biomedical materials, were discussed. This review is hoped to provide references for future researches on ablative immunotherapy to arrive to a promising new era of HCC treatment.

Multifunctional Composite Nanosystems for Precise/Enhanced Sonodynamic Oxidative Tumor Treatment

Ultrasound-activated therapies have been regarded as the efficient strategy for tumor treatment, among which sonosensitizer-enabled sonodynamic oxidative tumor therapy features intrinsic advantages as compared to other exogenous trigger-activated dynamic therapies. Nanomedicine-based nanosonosensitizer design has been extensively explored for improving the therapeutic efficacy of sonodynamic therapy (SDT) of tumor. This review focuses on solving two specific issues, i.e., precise and enhanced sonodynamic oxidative tumor treatment, by rationally designing and engineering multifunctional composite nanosonosensitizers. This multifunctional design can augment the therapeutic efficacy of SDT against tumor by either improving the production of reactive oxygen species or inducing the synergistic effect of SDT-based combinatorial therapies. Especially, this multifunctional design is also capable of endowing the nanosonosensitizer with bioimaging functionality, which can effectively guide and monitor the therapeutic procedure of the introduced sonodynamic oxidative tumor treatment. The design principles, underlying material chemistry for constructing multifunctional composite nanosonosensitizers, intrinsic synergistic mechanism, and bioimaging guided/monitored precise SDT are summarized and discussed in detail with the most representative paradigms. Finally, the existing critical issues, available challenges, and potential future developments of this research area are also discussed for promoting the further clinical translations of these multifunctional composite nanosonosensitizers in SDT-based tumor treatment.