Combined treatment of murine fibrosarcoma with chemotherapy (Paclitaxel), radiotherapy, and intratumoral injection of dendritic cells

Targeting CD8+ T cells with natural products for tumor therapy: Revealing insights into the mechanisms

BACKGROUND

Despite significant advances in cancer immunotherapy over the past decades, such as T cell-engaging chimeric antigen receptor (CAR)-T cell therapy and immune checkpoint blockade (ICB), therapeutic failure resulting from various factors remains prevalent. Therefore, developing combinational immunotherapeutic strategies is of great significance for improving the clinical outcome of cancer immunotherapy. Natural products are substances that naturally exist in various living organisms with multiple pharmacological or biological activities, and some of them have been found to have anti-tumor potential. Notably, emerging evidences have suggested that several natural compounds may boost the anti-tumor effects through activating immune response of hosts, in which CD8+ T cells play a pivotal role.

METHODS

The data of this review come from PubMed, Web of Science, Google Scholar, and ClinicalTrials (https://clinicaltrials.gov/) with the keywords "CD8+ T cell", "anti-tumor", "immunity", "signal 1", "signal 2", "signal 3", "natural products", "T cell receptor (TCR)", "co-stimulation", "co-inhibition", "immune checkpoint", "inflammatory cytokine", "hesperidin", "ginsenoside", "quercetin", "curcumin", "apigenin", "dendrobium officinale polysaccharides (DOPS)", "luteolin", "shikonin", "licochalcone A", "erianin", "resveratrol", "procyanidin", "berberine", "usnic acid", "naringenin", "6-gingerol", "ganoderma lucidum polysaccharide (GL-PS)", "neem leaf glycoprotein (NLGP)", "paclitaxel", "source", "pharmacological activities", and "toxicity". These literatures were published between 1993 and 2023.

RESULTS

Natural products have considerable advantages as anti-tumor drugs based on the various species, wide distribution, low price, and few side effects. This review summarized the effects and mechanisms of some natural products that exhibit anti-tumor effects via targeting CD8+ T cells, mainly focused on the three signals that activate CD8+ T cells: TCR, co-stimulation, and inflammatory cytokines.

CONCLUSION

Clarifying the role and underlying mechanism of natural products in cancer immunotherapy may provide more options for combinational treatment strategies and benefit cancer therapy, to shed light on identifying potential natural compounds for improving the clinical outcome in cancer immunotherapy.

Natural Products and their Derivatives as Immune Check Point Inhibitors: Targeting Cytokine/Chemokine Signalling in Cancer

Cancer immunotherapy is the new generation and widely accepted form of tumour treatment. It is, however, associated with exclusive challenges which include organ-specific inflammation, and single-target strategies. Therefore, approaches that can enhance the efficiency of existing immunotherapies and expand their indications are required for the further development of immunotherapy. Natural products and medicines are stated to have this desired effect on cancer immunotherapy (adoptive immune-cells therapy, cancer vaccines, and immune-check point inhibitors). They refurbish the immunosuppressed tumour microenvironment, which is the primary location of interaction of tumour cells with the host immune system. Various immune cell subsets, via interaction with cytokine/chemokine receptors, are recruited into this microenvironment, and these subsets have roles in tumour progression and treatment responsiveness. This review summarises cytokine/chemokine signalling, types of cancer immunotherapy and the herbal medicine-derived natural products targeting cytokine/chemokines and immune checkpoints. These natural compounds possess immunomodulatory activities and exert their anti-tumour effect by either blocking the interaction or modulating the expression of the proteins linked with immune checkpoint signaling pathways. Some compounds also show a synergistic effect in combination with existing monoclonal antibody drugs to reverse the tumour microenvironment. Additionally, we have also reported some studies about the derivatives and formulations used to overcome the limitations of natural forms. This review can provide important insights for directing future research.

Nab-paclitaxel promotes the cancer-immunity cycle as a potential immunomodulator

Paclitaxel is a widely used anti-tumor chemotherapeutic drug. Solvent-based paclitaxel causes bone marrow suppression, allergic reactions, neurotoxicity and systemic toxicity, which are associated with non-specific cytotoxicity and side effects of fat-soluble solvents. Studies have explored various new nano-drug strategies of paclitaxel, including nanoparticle albumin-bound paclitaxel (nab-paclitaxel) to improve the water solubility and safety of paclitaxel. Nab-paclitaxel is a targeted solvent-free formulation that inhibits microtubule depolymerization to anticancer. It is easily taken up by tumor and immune cells owing to the nano-scaled size and superior biocompatibility. The internalized nab-paclitaxel exhibits significant immunostimulatory activities to promote cancer-immunity cycle. The aim of this study was to explore the synergistic effect of nab-paclitaxel in tumor antigen presentation, T cell activation, reversing the immunosuppressive pattern of tumor microenvironment (TME), and the synergistic effect with cytotoxic lymphocytes (CTLs) in clearance of tumor cells. The effects of nab-paclitaxel on modulation of cancer-immunity cycle, provides potential avenues for combined therapeutic rationale to improve efficacy of immunotherapy.

Natural products and their derivatives: Promising modulators of tumor immunotherapy

A wealth of evidence supports the role of tumor immunotherapy as a vital therapeutic option in cancer. In recent decades, accumulated studies have revealed the anticancer activities of natural products and their derivatives. Increasing interest has been driven toward finding novel potential modulators of tumor immunotherapy from natural products, a hot research topic worldwide. These works of research mainly focused on natural products, including polyphenols (e.g., curcumin, resveratrol), cardiotonic steroids (e.g., bufalin and digoxin), terpenoids (e.g., paclitaxel and artemisinins), and polysaccharide extracts (e.g., lentinan). Compelling data highlight that natural products have a promising future in tumor immunotherapy. Considering the importance and significance of this topic, we initially discussed the integrated research progress of natural products and their derivatives, including target T cells, macrophages, B cells, NKs, regulatory T cells, myeloid‐derived suppressor cells, inflammatory cytokines and chemokines, immunogenic cell death, and immune checkpoints. Furthermore, these natural compounds inactivate several key pathways, including NF‐κB, PI3K/Akt, MAPK, and JAK/STAT pathways. Here, we performed a deep generalization, analysis, and summarization of the previous achievements, recent progress, and the bottlenecks in the development of natural products as tumor immunotherapy. We expect this review to provide some insight for guiding future research.

Progress in research on paclitaxel and tumor immunotherapy

Paclitaxel is a well-known anticancer agent with a unique mechanism of action. It is considered to be one of the most successful natural anticancer drugs available. This study summarizes the recent advances in our understanding of the sources, the anticancer mechanism, and the biosynthetic pathway of paclitaxel. With the advancement of biotechnology, improvements in endophytic fungal strains, and the use of recombination techniques and microbial fermentation engineering, the yield of extracted paclitaxel has increased significantly. Recently, paclitaxel has been found to play a large role in tumor immunity, and it has a great potential for use in many cancer treatments.

Irradiation enhances dendritic cell potential antitumor activity by inducing tumor cell expressing TNF-α

Dendritic cells (DCs)-based tumor vaccines have shown to be the promising methods for inducing therapeutic antitumor response. However, DCs alone rarely carry curative antitumor activity, and the immunosuppressive microenvironment may contribute to this defect of DC vaccinal function. Irradiation in combination with DCs has been shown to promote immune-mediated tumor destruction in preclinical studies. However, little is known about how irradiation alters the tumor microenvironment, and what host pathways modulate the activity of administrated DCs. In this study, BALB/c mice and the 4T1 breast cancer cell line were used in a tumor-bearing model. The tumor-bearing mice were irradiated locally up to 10 Gy for 3 consecutive days or a single dose of 30 Gy using a cesium source. Studies of dynamic change of the tumor microenvironment in irradiated versus untreated tumors revealed that there was no obvious change on IL-10, IL-6 and TGF-β expression or production, whereas increased TNF-α level within the first 2 weeks of irradiation. The increased TNF-α level is exactly right timing window for DCs injection, corresponding to the significant elevation of intratumoral CD8⁺ T infiltration and the regression of tumor size. With attention to scheduling, combination X-ray with DCs i.t. injection may offer a practical strategy to improve treatment outcomes.

Anti-tumor and anti-invasion effects of a combination of 4-methylumbelliferone and ionizing radiation in human fibrosarcoma cells

Hyaluronan (HA) is a major component of the extracellular matrix that is synthesized in excess in cancer tissues. 4-methylumbelliferone (MU) inhibits the synthesis of HA and is closely related to the invasion and metastasis of cancer. However, the effects of MU in conjunction with cancer radiotherapy remain unknown. The present study assessed the anti-tumor and anti-invasion effects of the concomitant use of ionizing radiation (IR) and 100 µM MU on human fibrosarcoma HT1080 cells. Cell viability and cellular invasion potency assays were performed. There was a greater decrease in the viability of cells cultured with a combination of 2 Gy IR and MU compared with untreated control cells. In addition, cell cycle distribution analysis demonstrated that a higher proportion of these cells were in the sub-G1 phase and higher fractions of annexin-V positive, propidium iodide positive cells (i.e., apoptotic cells) were observed. HA concentration in the 2 Gy irradiated culture was similar to that in the non-irradiated control culture, however, it significantly decreased following the administration of both MU alone and 2 Gy IR with MU. Furthermore, treatment with 2 Gy IR and MU resulted in a significant decrease in the invasion rate and matrix metalloproteinase (MMP)-2 and MPP-9 expression. Taken together, these results suggest that the administration of MU with 2 Gy IR is effective at reducing HA production, cell invasion and the metastatic potential of cancer cells.