The Research Progress of PD-1/PD-L1 Inhibitors Enhancing Radiotherapy Efficacy

Role of PD-1/PD-L1 signaling axis in oncogenesis and its targeting by bioactive natural compounds for cancer immunotherapy

Cancer is a global health problem and one of the leading causes of mortality. Immune checkpoint inhibitors have revolutionized the field of oncology, emerging as a powerful treatment strategy. A key pathway that has garnered considerable attention is programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1). The interaction between PD-L1 expressed on tumor cells and PD-1 reduces the innate immune response and thus compromises the capability of the body's immune system. Furthermore, it controls the phenotype and functionality of innate and adaptive immune components. A range of monoclonal antibodies, including avelumab, atezolizumab, camrelizumab, dostarlimab, durvalumab, sinitilimab, toripalimab, and zimberelimab, have been developed for targeting the interaction between PD-1 and PD-L1. These agents can induce a broad spectrum of autoimmune-like complications that may affect any organ system. Recent studies have focused on the effect of various natural compounds that inhibit immune checkpoints. This could contribute to the existing arsenal of anticancer drugs. Several bioactive natural agents have been shown to affect the PD-1/PD-L1 signaling axis, promoting tumor cell apoptosis, influencing cell proliferation, and eventually leading to tumor cell death and inhibiting cancer progression. However, there is a substantial knowledge gap regarding the role of different natural compounds targeting PD-1 in the context of cancer. Hence, this review aims to provide a common connection between PD-1/PD-L1 blockade and the anticancer effects of distinct natural molecules. Moreover, the primary focus will be on the underlying mechanism of action as well as the clinical efficacy of bioactive molecules. Current challenges along with the scope of future research directions targeting PD-1/PD-L1 interactions through natural substances are also discussed.

Efficacy and Mechanism of Combining Radiotherapy and Immunotherapy in Stage IV Non-Small Cell Lung Cancer

OPINION STATEMENT

Lung cancer is the leading cause of cancer-related deaths worldwide, with about 85% of patients being diagnosed as non-small cell lung cancer (NSCLC); and most presenting with stage IV disease initially. With the continuous advancement of treatment strategies of oncology, immunotherapy with/without chemo-immunotherapy has become the first-line treatment for patients with stage IV NSCLC. However, a proportion of patients still develop resistance to the treatment regimen and experience local progression, and primary lung lesion progression is the main progression pattern of stage IV NSCLC. Preclinical and clinical studies have demonstrated the potential of radiotherapy in anti-tumor treatment and suggest that administering local radiotherapy prior to cancer progression can prolong survival. Therefore, we consider whether adding local radiotherapy before the progression of a pulmonary lesion in stage IV NSCLC patients receiving chemo-immunotherapy would be beneficial. The present review aims to explore the efficacy and safety of combining radiotherapy with immunotherapy in the treatment of stage IV NSCLC, delving into the intricacies of their underlying mechanism.

Calcium nanoparticles target and activate T cells to enhance anti-tumor function

Calcium signaling plays a crucial role in the activation of T lymphocytes. However, modulating calcium levels to control T cell activation in vivo remains a challenge. In this study, we investigate T cell activation using 12-myristate 13-acetate (PMA)-encapsulated CaCO3 nanoparticles. We find that anti-PD-1 antibody-conjugated CaCO3 nanoparticles can be internalized by T cells via receptor-mediated endocytosis and then gradually release calcium. This results in an increase in cytosolic calcium, which triggers the activation of NFAT and NF-κB pathways, especially when the surface of the CaCO3 nanoparticles is loaded with PMA. Animal studies demonstrate that the PMA-loaded calcium nanoparticles enhance the activation and proliferation of cytotoxic T cells, leading to improved tumor suppression without additional toxicity. When tested in metastatic tumor models, T cells loaded with the calcium nanoparticles prior to adoptive cell transfer control tumor growth better, resulting in prolonged animal survival. Our approach offers an alternative T cell activation strategy to potentiate immunotherapy by targeting a fundamental signaling pathway.

AGuIX nanoparticle-nanobody bioconjugates to target immune checkpoint receptors

This article presents bioconjugates combining nanoparticles (AGuIX) with nanobodies (VHH) targeting Programmed Death-Ligand 1 (PD-L1, A12 VHH) and Cluster of Differentiation 47 (CD47, A4 VHH) for active tumor targeting. AGuIX nanoparticles offer theranostic capabilities and an efficient biodistribution/pharmacokinetic profile (BD/PK), while VHH's reduced size (15 kDa) allows efficient tumor penetration. Site-selective sortagging and click chemistry were compared for bioconjugation. While both methods yielded bioconjugates with similar functionality, click chemistry demonstrated higher yield and could be used for the conjugation of various VHH. The specific targeting of AGuIX@VHH has been demonstrated in both in vitro and ex vivo settings, paving the way for combined targeted immunotherapies, radiotherapy, and cancer imaging.

Impact of Waiting Response Evaluation to First-Line Systemic Therapy before Considering Local Ablative Therapy in Metastatic Non-Small-Cell Lung Cancer

Stereotactic radiotherapy (SRT) is gaining increasing importance in metastatic non-small-cell lung cancer (mNSCLC) management. The optimal sequence of tumor irradiation relative to systemic treatment remains unclear. If waiting response evaluation to first-line systemic therapy (FLST) before considering local treatment may allow for the exclusion of poorer prognosis progressive tumors that may not benefit from SRT, performing irradiation near immune check point inhibitor (ICI) first administration seems to improve their synergic effect. Herein, we aimed to determine whether delaying SRT after response evaluation to FLST would result in better prognosis. We compared overall survival (OS), progression-free survival (PFS), and time to first subsequent therapy (TFST) for 50 patients locally treated before or within 90 days of initiating FLST (early SRT), with 49 patients treated at least 90 days after initiating FLST (late SRT). Patients treated with conventional chemotherapy alone exhibited significantly poorer median OS, PFS, and TFST in the early SRT arm: (in months) 16.5 [8.33-NR] vs. 58.3 [35.05-NR] (p = 0.0015); 4.69 [3.57-8.98] vs. 8.20 [6.66-12.00] (p = 0.017); and 6.26 [4.82-11.8] vs. 10.0 [7.44-21.8] (p = 0.0074), respectively. Patient receiving ICI showed no difference in OS (NR [25.2-NR] vs. 36.6 [35.1-NR], p = 0.79), PFS (7.54 [6.23-NR] vs. 4.07 [2.52-NR], p = 0.19), and TFST (13.7 [9.48-NR] vs. 10.3 [3.54-NR], p = 0.49). These results suggest that delaying SRT treatment in order to filter a rapidly growing tumor may be less necessary when ICI is administered in mNSCLC.

Radionecrosis mimicking pseudo‑progression in a patient with lung cancer and brain metastasis following the combination of anti‑PD‑1 therapy and stereotactic radiosurgery: A case report

Brain metastases (BMs) usually develop in patients with non-small cell lung cancer. In addition to systemic therapy, radiation therapy and surgery, anti-programmed cell death-ligand 1 (PD-L1) therapy is another promising clinical anticancer treatment modality. However, the optimal timing and drug-drug interactions of anti-PD-L1 therapy with other combined treatments remain to be elucidated. Treatment with anti-PD-L1 therapy is associated with an increased risk of radionecrosis (RN) regardless of tumor histology. The present study described a case of RN in a patient with lung adenocarcinoma and with BM who received anti-PD-L1 therapy. Before anti-PD-L1 treatment, the patient received whole brain radiotherapy. During durvalumab treatment, the intracranial metastases regressed. The progression of intracranial lesions 9 months later prompted a second-line of therapy with PD-L1 inhibitor durvalumab and stereotactic radiotherapy (SRT). Despite stereotactic irradiation, the lesions progressed further, leading to surgical resection. On examination, RN was detected, but there was no evidence of metastatic lung cancer. The aim of the present study was to present the longitudinal change in magnetic resonance imaging in RN following STR and anti-PD-L1 combined therapy. The atypical image of RN is conditionally important for making an accurate preoperative diagnosis.

CD73 and PD-L1 dual blockade amplifies antitumor efficacy of SBRT in murine PDAC models

BACKGROUND

Stereotactic body radiotherapy (SBRT) induces immunogenic cell death, leading to subsequent antitumor immune response that is in part counterbalanced by activation of immune evasive processes, for example, upregulation of programmed cell death-ligand 1 (PD-L1) and adenosine generating enzyme, CD73. CD73 is upregulated in pancreatic ductal adenocarcinoma (PDAC) compared with normal pancreatic tissue and high expression of CD73 in PDACs is associated with increased tumor size, advanced stage, lymph node involvement, metastasis, PD-L1 expression and poor prognosis. Therefore, we hypothesized that blockade of both CD73 and PD-L1 in combination with SBRT might improve antitumor efficacy in an orthotopic murine PDAC model.

METHODS

We assessed the combination of systemic blockade of CD73/PD-L1 and local SBRT on tumor growth in primary pancreatic tumors, and investigated systemic antitumor immunity using a metastatic murine model bearing both orthotopic primary pancreatic tumor and distal hepatic metastases. Immune response was quantified by flow cytometric and Luminex analyses.

RESULTS

We demonstrated that blockade of both CD73 and PD-L1 significantly amplified the antitumor effect of SBRT, leading to superior survival. The triple therapy (SBRT+anti-CD73+anti-PD-L1) modulated tumor-infiltrating immune cells with increases of interferon-γ+CD8+ T cells. Additionally, triple therapy reprogramed the profile of cytokines/chemokines in the tumor microenvironment toward a more immunostimulatory phenotype. The beneficial effects of triple therapy are completely abrogated by depletion of CD8+ T cells, and partially reversed by depletion of CD4+ T cells. Triple therapy promoted systemic antitumor responses illustrated by: (1) potent long-term antitumor memory and (2) enhanced both primary and liver metastases control along with prolonged survival.

Basic and translational research on carbon-ion radiobiology

Carbon-ion beam irradiation (IR) has evident advantages over the conventional photon beams in treating tumors. It releases enormous amount of energy in a well-defined range with insignificant scatter in surrounding tissues based on well-localized energy deposition. Over the past 28 years, more than 14,000 patients with various types of cancer have been treated by carbon ion radiotherapy (CIRT) with promising results at QST. I have provided an overview of the basic and translational research on carbon-ion radiobiology including mechanisms underlying high linear energy transfer (LET) carbon-ion IR-induced cell death (apoptosis, autophagy, senescence, mitotic catastrophe etc.) and high radiocurability produced by carbon-ion beams in combination with DNA damaging drugs or with molecular-targeted drugs, micro-RNA therapeutics and immunotherapy. Additionally, I have focused on the application of these treatment in human cancer cells, especially cancer stem cells (CSCs). Finally, I have summarized the current studies on the application of basic carbon-ion beam IR according to the cancer types and clinical outcomes.

Sulforaphane regulates Nrf2-mediated antioxidant activity and downregulates TGF-β1/Smad pathways to prevent radiation-induced muscle fibrosis

AIMS

This study aimed to examine the efficacy of sulforaphane (SFN) in preventing radiation-induced muscle fibrosis (RIMF) and the potential role in nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant stress.

MAIN METHODS

The RIMF model was established by a single irradiation of the left thigh of C57BL/6 J mice, and the mice were then randomly divided into control, SFN, irradiation (IR), and IR + SFN (IR/SFN) groups. The serum and skeletal muscle were collected eight weeks after irradiation, and changes in oxidative stress and muscle fibrosis were detected.

KEY FINDINGS

The IR group showed a more obvious skeletal muscle fiber atrophy, significantly higher number of collagen fibers, and higher inflammatory cell infiltration compared to control group. Compared to the IR group, the IR/SFN group had orderly arranged muscle fibers, decreased collagen fibers, and infiltration of inflammatory cells. In addition, compared with the control group, the expression of oxidative stress-related indexes was significantly increased, accompanied by activation of the transforming growth factor (TGF-β)/Smad pathway and its downstream fibrogenic molecules in the skeletal muscle of the IR group. After SFN intervention, the above indices were significantly restored. Furthermore, SFN induced the upregulation of Nrf2, activation of AKT, and inhibition of GSK-3β and Fyn accumulation.

SIGNIFICANCE

These results revealed that Nrf2 plays a central role in protecting against RIMF. Furthermore, SFN prevents RIMF by activating Nrf2 via the AKT/GSK-3β/Fyn pathway.

Dynamic alterations in PD-1/PD-L1 expression level and immune cell profiles based on radiation response status in mouse tumor model

Introduction

Based on the immunologic effects of anti-cancer treatment and their therapeutic implications, we evaluated radiotherapy (RT)-induced dynamic alterations in programmed death-1 (PD-1)/PD ligand-1 (PD-L1) expression profiles.

Methods

Local RT with 2 Gy × 5 or 7.5 Gy × 1 was administered to the CT26 mouse model. Thereafter, tumors were resected and evaluated at the following predefined timepoints according to radiation response status: baseline, early (immediately after RT), middle (beginning of tumor shrinkage), late (stable status with RT effect), and progression (tumor regrowth). PD-1/PD-L1 activity and related immune cell profiles were quantitatively assessed.

Results

RT upregulated PD-L1 expression in tumor cells from the middle to late phase; however, the levels subsequently decreased to levels comparable to baseline in the progression phase. RT with 2 Gy × 5 induced a higher frequency of PD-L1+ myeloid-derived suppressor cells, with a lesser degree of tumor regression, compared to 7.5 Gy. The proportion of PD-1+ and interferon (IFN)-γ+CD8α T cells continued to increase. The frequency of splenic PD-1+CD8+ T cells was markedly elevated, and was sustained longer with 2 Gy × 5. Based on the transcriptomic data, RT stimulated the transcription of immune-related genes, leading to sequentially altered patterns.

Discussion

The dynamic alterations in PD-1/PD-L1 expression level were observed according to the time phases of tumor regression. This study suggests the influence of tumor cell killing and radiation dosing strategy on the tumor immune microenvironment.

Current progress and future perspectives of neoadjuvant anti-PD-1/PD-L1 therapy for colorectal cancer

Immunotherapies, especially the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) inhibitors, have revolutionized the therapeutic strategies of various cancers. As for colorectal cancer (CRC), the current clinical application of PD-1/PD-L1 inhibitors are mainly used according to the mutation pattern, which is categorized into deficient mismatch repair (dMMR)/high levels of microsatellite instability (MSI-H) and proficient mismatch repair (pMMR), or non-high levels of microsatellite instability (non-MSI-H). PD-1/PD-L1 inhibitors have been proven to have favorable outcomes against dMMR/MSI-H CRC because of more T-cell infiltration into tumor tissues. Nevertheless, the effectiveness of PD-1/PD-L1 inhibitors in pMMR/non-MSI-H CRC is still uncertain. Because of the quite-lower proportion of dMMR/MSI-H in CRC, PD-1/PD-L1 inhibitors have been reported to combine with other antitumor treatments including chemotherapy, radiotherapy, and targeted therapy for better therapeutic effect in recent clinical trials. Neoadjuvant therapy, mainly including chemotherapy and radiotherapy, not only can reduce clinical stage but also benefit from local control, which can improve clinical symptoms and the quality of life. Adding immunotherapy into neoadjuvant therapy may change the treatment strategy of primary resectable or some metastatic CRC. In this review, we focus on the development of neoadjuvant anti-PD-1/PD-L1 therapy and discuss the future perspectives in CRC.

Clinical Efficacy and Safety Analysis of PD-1/PD-L1 Inhibitor vs. Chemotherapy in the Treatment of Advanced Non-Small-Cell Lung Cancer: A Systematic Review and Meta-Analysis

Objective

To systematically evaluate the efficacy and safety of pembrolizumab (PD-1/PD-L inhibitor) and adjuvant chemotherapy to treat NSCLC and provide evidence-based reference for clinical use.

Methods

By searching the Cochrane Library, EMBASE, PubMed, and Web of Science, according to the inclusion criteria, literature selection, data extraction, and quality evaluation were carried out for the included literature. The I ² test was used to evaluate heterogeneity between studies, and the meta-analysis was performed using RevMan 5.3 software provided by Cochrane.

Results

Finally, 14 relevant documents meeting the standards were included. It is a statistical difference in one-year survival rate [OR = 1.50, 95% CI (1.28, 1.76), P < 0.00001, I ² = 0%, Z = 4.99]; overall response rate[OR =1.57, 95% CI (1.29, 1.90), P < 0.00001, I ² = 0%, Z = 4.58]; progression-free survival [OR = 2.99, 95% CI (2.29, 3.91), P < 0.00001, I ² = 26%, Z = 8.00]; and overall survival [OR = 1.38, 95% CI (1.07, 1.78), P = 0.01, I ² = 46%, Z = 2.50] and reduces the incidence of adverse drug reactions [OR = 2.54, 95% CI (1.99, 3.25), P < 0.00001, I ² = 69%, Z = 7.43].

Conclusion

Pembrolizumab adjuvant chemotherapy is effective in the treatment of advanced NSCLC, but attention should be paid to the occurrence of adverse reactions in clinical. Due to the limitations of the methodology included in the study, this conclusion required more validation of large-sample RCT.