The biologically functional identification of a novel TIM3-binding peptide P26 in vitro and in vivo

Cholesterol-modified peptide nanomicelles as a promising platform for cancer therapy: A review

Drug resistance, systemic toxicity, low solubility, and rapid clearance are common issues with chemotherapy drugs and other molecules used to treat cancer. The development of new therapeutic compounds and nanotherapy offers a solution to these issues. Therapeutic peptides have attracted great interest among these molecules due to their unique advantages, including low immunogenicity, efficient cellular internalization, deep tissue penetration, and low systemic toxicity. They have shown promise in cancer treatment by inducing apoptosis, necrosis, or cell lysis and promoting immunotherapy. In addition, peptides can deliver a range of cargoes, such as drugs, nucleic acids, imaging agents, and nanoparticles, and can specifically target cancer cells. However, problems such as their short half-life and low solubility limit their therapeutic use. Recent developments have addressed these constraints through structural alterations and nanoparticle formulations. In particular, cholesterol modification makes it possible for peptides to self-assemble into nanomicelles, which enhances their stability, half-life, and cell penetration. In this review, therapeutic peptides are presented as a versatile and successful cancer treatment option. The potential of cholesterol-modified peptide micelles as a reliable drug, nucleic acid, and imaging agent delivery system is also examined.

Peptide‑based therapeutic strategies for glioma: Current state and prospects

Glioma is a prevalent form of primary malignant central nervous system tumor, characterized by its cellular invasiveness, rapid growth, and the presence of the blood-brain barrier (BBB)/blood-brain tumor barrier (BBTB). Current therapeutic approaches, such as chemotherapy and radiotherapy, have shown limited efficacy in achieving significant antitumor effects. Therefore, there is an urgent demand for new treatments. Therapeutic peptides represent an innovative class of pharmaceutical agents with lower immunogenicity and toxicity. They are easily modifiable via chemical means and possess deep tissue penetration capabilities which reduce side effects and drug resistance. These unique pharmacokinetic characteristics make peptides a rapidly growing class of new therapeutics that have demonstrated significant progress in glioma treatment. This review outlines the efforts and accomplishments in peptide-based therapeutic strategies for glioma. These therapeutic peptides can be classified into four types based on their anti-tumor function: tumor-homing peptides, inhibitor/antagonist peptides targeting cell surface receptors, interference peptides, and peptide vaccines. Furthermore, we briefly summarize the results from clinical trials of therapeutic peptides in glioma, which shows that peptide-based therapeutic strategies exhibit great potential as multifunctional players in glioma therapy.

Novel Peptide-Based 68Ga-Labeled Radiotracer for Preclinical Studies of TIM3 Expression

T-cell immunoglobulin and mucin domain-3 (TIM3) is an immune checkpoint that plays a negative regulatory role in the immune response. TIM3-targeted drugs inhibit this negative regulation, thereby modulating the level of immune response activation. In the previous investigation, several peptides targeting TIM3 were identified through screening from a phage peptide library. In this research, three peptides were selected to construct the radioactive molecular probes according to the characteristic that targeting TIM3 drugs would lead to the increase of interferon-γ (IFN-γ) secretion. Molecular docking was performed to assess the binding properties of the selected peptides with the TIM3 protein. To further enhance the targeting properties, one of the peptides with a higher-affinity peptide was structurally modified. Then, 68Ga was used to construct the peptide probe 68Ga-DOTA-peptide by labeling the six peptides with 68Ga riboprobes, and the binding affinity and specificity were assessed using TIM3 overexpressing cell line A549TIM3 and the parental A549 cells. In addition, in Micro-PET/CT imaging, transfected model mice were dynamically imaged for 30 min after injection of 3.7-7.4 MBq 68Ga-DOTA-peptides via the tail vein. Meanwhile, the same dose of molecular probes was injected in the MC38 model (colorectal cancer in mice) and the CCRCC (clear cell renal cell carcinoma) xenografted model, followed by static scans at 15, 30, and 60 min postinjection. Finally, immunohistochemical (IHC) staining was performed to assess TIM3 expression in the dissected tumor tissues. The molecular docking results showed that the binding energy of P26 to TIM3 protein was -6.5 kcal/mol, which was lower than that of P24 to TIM3 protein, -3.6 kcal/mol, indicating that the affinity of P26 peptide to TIM3 protein was higher than that of P24 and P20 peptide. After structural modification of the P26 peptide, P26NH2, r-NH2, and P26X2 were obtained, and the above peptides were successfully constructed into six targeting TIM3 peptide probes by 68Ga labeling. Cellular uptake experiments demonstrated that 68Ga-DOTA-P26, 68Ga-DOTA-P26NH2, and 68Ga-DOTA-r-NH2 showed significantly higher uptake in A549TIM3 cells than in A549 cells and could be blocked by the unlabeled peptide. Micro-PET imaging experiments showed that the uptake of each probe in the A549TIM3 model tumor tissue was significantly higher than that in the A549 model tumor tissue, and a comparison of the tumor-to-cardiac uptake ratios of each group showed that the 68Ga-DOTA-P26 had a better tumor-to-cardiac uptake ratio in the A549TIM3 model than several other molecular probes, and in the MC38 model, similar results were obtained, with the difference that the 68Ga-DOTA-P26NH2 had the highest tumor-to-cardiac uptake ratio in the CCRCC model. Finally, validation by IHC showed that A549TIM3, MC38, and CCRCC tumor tissues had varying degrees of TIM3 expression. Upon comparison of ex vivo and in vivo studies, one of them, the 68Ga-DOTA-P26 probe, demonstrated significant target specificity for TIM3. These results suggest that studying peptide probes targeting TIM3 will promote the process of TIM3-targeted drug research and is expected to guide the application of TIM3 immune checkpoint drugs in immunotherapy.

Structure-Based Rational Design of Constrained Peptides as TIM-3 Inhibitors

Blocking the immunosuppressive function of T-cell immunoglobulin mucin-3 (TIM-3) is an established therapeutic strategy to maximize the efficacy of immune checkpoint inhibitors for cancer immunotherapy. Currently, effective inhibition of TIM-3 interactions relies on monoclonal antibodies (mAbs), which come with drawbacks such as immunogenicity risk, limited tumor penetration, and high manufacturing costs. Guided by the X-ray cocrystal structures of TIM-3 with mAbs, we report an in silico structure-based rational design of constrained peptides as potent TIM-3 inhibitors. The top cyclic peptide from our study (P2) binds TIM-3 with a K D value of 166.3 ± 12.1 nM as determined by surface plasmon resonance (SPR) screening. Remarkably, P2 efficiently inhibits key TIM-3 interactions with natural TIM-3 ligands at submicromolar concentrations in a panel of cell-free and cell-based assays. The capacity of P2 to reverse immunosuppression in T-cell/cancer cell cocultures, coupled with favorable in vitro pharmacokinetic properties, highlights the potential of P2 for further evaluation in preclinical models of immuno-oncology.

Galectin-9, a pro-survival factor inducing immunosuppression, leukemic cell transformation and expansion

Leukemia is a malignancy of the bone marrow and blood originating from self-renewing cancerous immature blast cells or transformed leukocytes. Despite improvements in treatments, leukemia remains still a serious disease with poor prognosis because of disease heterogeneity, drug resistance and relapse. There is emerging evidence that differentially expression of co-signaling molecules play a critical role in tumor immune evasion. Galectin-9 (Gal-9) is one of the key proteins that leukemic cells express, secrete, and use to proliferate, self-renew, and survive. It also suppresses host immune responses controlled by T and NK cells, enabling leukemic cells to evade immune surveillance. The present review provides the molecular mechanisms of Gal-9-induced immune evasion in leukemia. Understanding the complex immune evasion machinery driven by Gal-9 expressing leukemic cells will enable the identification of novel therapeutic strategies for efficient immunotherapy in leukemic patients. Combined treatment approaches targeting T-cell immunoglobulin and mucin domain-3 (Tim-3)/Gal-9 and other immune checkpoint pathways can be considered, which may enhance the efficacy of host effector cells to attack leukemic cells.

Prediction of the Peptide-TIM3 Binding Site in Inhibiting TIM3-Galectin 9 Binding Pathways

T-cell immunoglobulin and mucin domain-containing protein-3 (TIM3) is an important receptor protein that modulates the immune system. The binding of TIM3 with Galectin 9 (GAL9) triggers immune system suppression, but the TIM3-GAL9 binding can be inhibited by binding of the peptide P26 to TIM3. A fast and accurate prediction of the P26-TIM3 binding site is crucial and a prerequisite for the investigation of P26-TIM3 interactions and TIM3-GAL9 binding pathways. Here, we present a machine learning approach, which considers protein conformational changes, to quickly identify the ligand-binding site on TIM3. Our results show that the P26 binding site is located near the C″-D loop of TIM3. Further simulations show that the binding pose is stabilized by a variety of electrostatic and hydrophobic interactions. Binding of P26 can alter the conformations of nearby glycan side chains on TIM3, providing possible mechanisms of how P26 inhibits TIM3-GAL9 binding pathways. The insights from this work will facilitate the identification of other peptides or antibodies that may also inhibit the TIM3-GAL9 pathways and eventually lead to improved attempts in the modulation of the TIM3-GAL9 immunosuppression pathways. The strategies and machine learning method can be generalized to study ligand-receptor binding when the conformational changes during the binding are important.

Peptides as multifunctional players in cancer therapy

Peptides exhibit lower affinity and a shorter half-life in the body than antibodies. Conversely, peptides demonstrate higher efficiency in tissue penetration and cell internalization than antibodies. Regardless of the pros and cons of peptides, they have been used as tumor-homing ligands for delivering carriers (such as nanoparticles, extracellular vesicles, and cells) and cargoes (such as cytotoxic peptides and radioisotopes) to tumors. Additionally, tumor-homing peptides have been conjugated with cargoes such as small-molecule or chemotherapeutic drugs via linkers to synthesize peptide-drug conjugates. In addition, peptides selectively bind to cell surface receptors and proteins, such as immune checkpoints, receptor kinases, and hormone receptors, subsequently blocking their biological activity or serving as hormone analogs. Furthermore, peptides internalized into cells bind to intracellular proteins and interfere with protein-protein interactions. Thus, peptides demonstrate great application potential as multifunctional players in cancer therapy.

Identification of a novel small-molecule inhibitor targeting TIM-3 for cancer immunotherapy

PD-1/PD-L1 blockade has achieved substantial clinical results in cancer treatment. However, the expression of other immune checkpoints leads to resistance and hinders the efficacy of PD-1/PD-L1 blockade. T cell immunoglobulin and mucin domain 3 (TIM-3), a non-redundant immune checkpoint, synergizes with PD-1 to mediate T cell dysfunction in tumor microenvironment. Development of small molecules targeting TIM-3 is a promising strategy for cancer immunotherapy. Here, to identify small molecule inhibitors targeting TIM-3, the docking pocket in TIM-3 was analyzed by Molecular Operating Environment (MOE) and the Chemdiv compound database was screened. The small molecule SMI402 could bind to TIM-3 with high affinity and prevent the ligation of PtdSer, HMGB1, and CEACAM1. SMI402 reinvigorated T cell function in vitro. In the MC38-bearing mouse model, SMI402 inhibited tumor growth by increasing CD8⁺ T and natural killing (NK) cells infiltration at the tumor site, as well as restoring the function of CD8⁺ T and NK cells. In conclusions, the small molecule SMI402 shows promise as a leading compound which targets TIM-3 for cancer immunotherapy.

Modulation of the Gal-9/TIM-3 Immune Checkpoint with α-Lactose. Does Anomery of Lactose Matter?

Simple Summary

The disaccharide lactose is a common excipient in pharmaceutical products. In addition, the two anomers α- and β-lactose can exert immuno-modulatory effects. α-Lactose functions as a major regulator of the T-cell immunoglobulin mucin-3 (Tim-3)/Galectin-9 (Gal-9) immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of TIM-3 with monoclonal antibodies or small molecules represents a promising approach to combat onco-hematological diseases, in particular myelodysplastic syndromes, and acute myeloid leukemia. Alternatively, the activity of the checkpoint can be modulated via targeting of Gal-9 with both α- and β-lactose. In fact, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. This review discusses the capacity of lactose and Gal-9 to modulate the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. The immuno-regulatory roles of lactose and Gal-9 are highlighted.

Abstract

The disaccharide lactose is an excipient commonly used in pharmaceutical products. The two anomers, α- and β-lactose (α-L/β-L), differ by the orientation of the C-1 hydroxyl group on the glucose unit. In aqueous solution, a mutarotation process leads to an equilibrium of about 40% α-L and 60% β-L at room temperature. Beyond a pharmaceutical excipient in solid products, α-L has immuno-modulatory effects and functions as a major regulator of TIM-3/Gal-9 immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of the co-inhibitory checkpoint TIM-3 expressed on T cells with anti-TIM-3 antibodies represents a promising approach to combat different onco-hematological diseases, in particular myelodysplastic syndromes and acute myeloid leukemia. In parallel, the discovery and development of anti-TIM-3 small molecule ligands is emerging, including peptides, RNA aptamers and a few specifically designed heterocyclic molecules. An alternative option consists of targeting the different ligands of TIM-3, notably Gal-9 recognized by α-lactose. Modulation of the TIM-3/Gal-9 checkpoint can be achieved with both α- and β-lactose. Moreover, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. The present review provides a complete analysis of the pharmaceutical and galectin-related biological functions of (α/β)-lactose. A focus is made on the capacity of lactose and Gal-9 to modulate both the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. Modulation of the TIM-3/Gal-9 checkpoint is a promising approach for the treatment of cancers and the role of lactose in this context is discussed. The review highlights the immuno-regulatory functions of lactose, and the benefit of the molecule well beyond its use as a pharmaceutical excipient.