Combined cancer therapeutics-Tackling the complexity of the tumor microenvironment

Adjuvant role of Salvia miltiorrhiza bunge in cancer chemotherapy: A review of its bioactive components, health-promotion effect and mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Chemotherapy is a common cancer treatment strategy. However, its effectiveness is constrained by toxicity and adverse effects. The Lamiaceae herb Salvia miltiorrhiza Bunge has a long history of therapeutic use in the treatment of blood stasis illnesses, which are believed by traditional Chinese medicine to be connected to cancer.

AIM OF THE STUDY

This review summarized the common toxicity of chemotherapy and the potential chemo-adjuvant effect and mechanisms of active ingredients from S. miltiorrhiza, hoping to provide valuable information for the development and application of S. miltiorrhiza resources.

MATERIALS AND METHODS

The literatures were retrieved from PubMed, Web of Science, Baidu Scholar and Google Scholar databases from 2002 to 2022. The inclusion criteria were studies reporting that S. miltiorrhiza or its constituents enhanced the efficiency of chemotherapy drugs or reduced the side effects.

RESULTS

Salvianolic acid A, salvianolic acid B, salvianolic acid C, rosmarinic acid, tanshinone I, tanshinone IIA, cryptotanshinone, dihydrotanshinone I and miltirone are the primary adjuvant chemotherapy components of S. miltiorrhiza. The mechanisms mainly involve inhibiting proliferation, metastasis, and angiogenesis, inducing apoptosis, regulating autophagy and tumor microenvironment. In addition, they also improve chemotherapy drug-induced side effects.

CONCLUSIONS

The bioactive compounds of S. miltiorrhiza are shown to inhibit proliferation, metastasis, and angiogenesis, induce apoptosis and autophagy, regulate immunity and tumor microenvironment when combined with chemotherapy drugs. However, further clinical studies are required to validate the current studies.

Doxorubicin-sensitive and -resistant colorectal cancer spheroid models: assessing tumor microenvironment features for therapeutic modulation

Introduction: The research on tumor microenvironment (TME) has recently been gaining attention due to its important role in tumor growth, progression, and response to therapy. Because of this, the development of three-dimensional cancer models that mimic the interactions in the TME and the tumor structure and complexity is of great relevance to cancer research and drug development. Methods: This study aimed to characterize colorectal cancer spheroids overtime and assess how the susceptibility or resistance to doxorubicin (Dox) or the inclusion of fibroblasts in heterotypic spheroids influence and modulate their secretory activity, namely the release of extracellular vesicles (EVs), and the response to Dox-mediated chemotherapy. Different characteristics were assessed over time, namely spheroid growth, viability, presence of hypoxia, expression of hypoxia and inflammation-associated genes and proteins. Due to the importance of EVs in biomarker discovery with impact on early diagnostics, prognostics and response to treatment, proteomic profiling of the EVs released by the different 3D spheroid models was also assessed. Response to treatment was also monitored by assessing Dox internalization and its effects on the different 3D spheroid structures and on the cell viability. Results and Discussion: The results show that distinct features are affected by both Dox resistance and the presence of fibroblasts. Fibroblasts can stabilize spheroid models, through the modulation of their growth, viability, hypoxia and inflammation levels, as well as the expressions of its associated transcripts/proteins, and promotes alterations in the protein profile exhibit by EVs. Summarily, fibroblasts can increase cell-cell and cell-extracellular matrix interactions, making the heterotypic spheroids a great model to study TME and understand TME role in chemotherapies resistance. Dox resistance induction is shown to influence the internalization of Dox, especially in homotypic spheroids, and it is also shown to influence cell viability and consequently the chemoresistance of those spheroids when exposed to Dox. Taken together these results highlight the importance of finding and characterizing different 3D models resembling more closely the in vivo interactions of tumors with their microenvironment as well as modulating drug resistance.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.

Recent Advances in Biomimetic Nanocarrier-Based Photothermal Therapy for Cancer Treatment

Nanomedicine presents innovative solutions for cancer treatment, including photothermal therapy (PTT). PTT centers on the design of photoactivatable nanoparticles capable of absorbing non-toxic near-infrared light, generating heat within target cells to induce cell death. The successful transition from benchside to bedside application of PTT critically depends on the core properties of nanoparticles responsible for converting light into heat and the surface properties for precise cell-specific targeting. Precisely targeting the intended cells remains a primary challenge in PTT. In recent years, a groundbreaking approach has emerged to address this challenge by functionalizing nanocarriers and enhancing cell targeting. This strategy involves the creation of biomimetic nanoparticles that combine desired biocompatibility properties with the immune evasion mechanisms of natural materials. This review comprehensively outlines various strategies for designing biomimetic photoactivatable nanocarriers for PTT, with a primary focus on its application in cancer therapy. Additionally, we shed light on the hurdles involved in translating PTT from research to clinical practice, along with an overview of current clinical applications.

Stimuli-responsive nanoassemblies for targeted delivery against tumor and its microenvironment

Despite the emergence of various cancer treatments, such as surgery, chemotherapy, radiotherapy, and immunotherapy, their use remains restricted owing to their limited tumor elimination efficacy and side effects. The use of nanoassemblies as delivery systems in nanomedicine for tumor diagnosis and therapy is flourishing. These nanoassemblies can be designed to have various shapes, sizes, and surface charges to meet the requirements of different applications. It is crucial for nanoassemblies to have enhanced delivery of payloads while inducing minimal to no toxicity to healthy tissues. In this review, stimuli-responsive nanoassemblies capable of combating the tumor microenvironment (TME) are discussed. First, various TME characteristics, such as hypoxia, oxidoreduction, adenosine triphosphate (ATP) elevation, and acidic TME, are described. Subsequently, the unique characteristics of the vascular and stromal TME are differentiated, and multiple barriers that have to be overcome are discussed. Furthermore, strategies to overcome these barriers for successful drug delivery to the targeted site are reviewed and summarized. In conclusion, the possible challenges and prospects of using these nanoassemblies for tumor-targeted delivery are discussed. This review aims at inspiring researchers to develop stimuli-responsive nanoassemblies for tumor-targeted delivery for clinical applications.

A Nanosized Codelivery System Based on Intracellular Stimuli-Triggered Dual-Drug Release for Multilevel Chemotherapy Amplification in Drug-Resistant Breast Cancer

Lacking nano-systems for precisely codelivering the chemotherapeutics paclitaxel (PTX) and the natural P-glycoprotein (P-gp) inhibitor, quercetin (QU), into cancer cells and controlling their intracellular release extremely decreased the anticancer effects in multidrug resistant (MDR) tumors. To overcome this hurdle, we constructed hybrid polymeric nanoparticles (PNPs) which consist of redox-sensitive PTX/polyethyleneimine-tocopherol hydrogen succinate-dithioglycollic acid PNPs and pH-sensitive hyaluronic acid-QU conjugates. The obtained hybrid PNPs can be internalized into drug-resistant breast cancer cells by the hyaluronic acid/CD44-mediated endocytosis pathway and escape from the lysosome through the “proton sponge effect”. Under the trigger of intracellular stimuli, the nanoplatform used the pH/glutathione dual-sensitive disassembly to release QU and PTX. The PTX diffused into microtubules to induce tumor cell apoptosis, while QU promoted PTX retention by down-regulating P-gp expression. Moreover, tocopherol hydrogen succinate and QU disturbed mitochondrial functions by generating excessive reactive oxygen species, decreasing the mitochondrial membrane potential, and releasing cytochrome c into the cytosol which consequently achieved intracellular multilevel chemotherapy amplification in MDR cancers. Importantly, the PNPs substantially suppressed tumors growth with an average volume 2.54-fold lower than that of the control group in the MCF-7/ADR tumor-bearing nude mice model. These presented PNPs would provide a valuable reference for the coadministration of natural compounds and anticarcinogens for satisfactory combination therapy in MDR cancers.

Platinum(II) and Copper(II) complexes of asymmetric halogen-substituted [NN'O] ligands: Synthesis, characterization, structural investigations and antiproliferative activity

In order to better understand the effect of structure, halogen substitution, metal ions and ligand flexibility on antiproliferative activity, eight Cu(II) complexes and eight Pt(II) complexes were obtained of 2,4-X₁,X₂-6-((pyridine-2-ylmethylamino)methyl)phenol and 2,4-X₁,X₂-6-((pyridine-2-ylmethylamino)ethyl)phenol (where X is Cl, Br, or I) ligands. The compounds were characterized with various techniques, such as FT-IR, NMR, elemental analysis and single-crystal X-ray diffraction (SCXRD). The X-ray structures showed that ligand acts as a bidentate and tridentate donor in Cu(II) and Pt(II) complexes, respectively. This difference in structures is due to the use or non-use of base in the preparation of complexes. Also, complexation of Cl₂-H₂L₁ with CuCl₂·2H₂O gives two different types of structures: polymer (Cl₂-H₂L₁-Cu^polymer) and dimer (Cl₂-H₂L₁-Cu^dimer), according to the crystal color. In addition, ¹H NMR spectrum for platinum complexes display two set of signals that can be attributed to the presence of two isomers in solution. All complexes induced moderate to high reduction in A2780 and HCT116 cancer cell viability. However, only complexes bearing iodo- substituted in ligands exhibited significantly low cytotoxicity in normal fibroblasts when compared with cancer cell lines. The antiproliferative effect exhibited by I₂-H₂L₂-Cu complex in A2780 cell line was due to induction of cell death mechanisms, namely by apoptosis and autophagy. I₂-H₂L₂-Cu complex does not cause DNA cleavage but a slight delay in cell cycle was observed for the first 24 h of exposition. High cytotoxicity was related with the induction of intracellular ROS. This increase in intracellular ROS was not accompanied by destabilization of the mitochondrial membrane which is an indication that ROS are being triggered externally by I₂-H₂L₂-Cu complex and in agreement with an extrinsic apoptosis activation. I₂-H₂L₂-Cu complex has a pro-angiogenic effect, increasing the vascularization of the CAM in chicken embryos. This is also a very important characteristic in cancer treatment since the increased vascularization in tumors might facilitate the delivery of therapeutic drugs. Taken together, these results support the potential therapeutic of the I₂-H₂L₂-Cu complex.

Tumor Microenvironment-Responsive Shell/Core Composite Nanoparticles for Enhanced Stability and Antitumor Efficiency Based on a pH-Triggered Charge-Reversal Mechanism

High systemic stability and effective tumor accumulation of chemotherapeutic agents are indispensable elements that determine their antitumor efficacy. PEGylation of nanoparticles (NPs) could prolong the retention time in vivo by improving their stability in circulation, but treatment suffers reduced tumor penetration and cellular uptake of nanomedicines. The tumor microenvironment (TME)-responsive NPs maintain their stealth features during circulation and undergo a stimuli-responsive dePEGylation once exposed to the site of action, thereby achieving enhanced internalization in tumor cells. Herein, TME-responsive shell/core composite nanoparticles were prepared and optimized with enhanced stability and tumor intake efficiency. We synthesized 12-hydroxystearic acid-poly (ethylene glycol)-YGRKKRRQRRR (HA-PEG-TAT) as a post-insert apparatus in disulfiram (DSF)-encapsulated naked nanoparticles (N-NPs) in order to form a cationic core (TAT-NPs). Accordingly, the negatively charged poly (glutamate acid)-graft-poly (ethylene glycol) (PGlu-PEG) was further applied to the surface of TAT-NPs as a negative charged shell (PGlu-PEG/TAT-NPs) via the electrostatic interaction between glutamic acids and arginine at the outer ring of the TAT-NPs. PGlu-PEG/TAT-NPs displayed a huge loading capability for DSF with reduced degradation in plasma and exhibited rapid charge reversal when pH decreased from 7.4 to pH 6.5, demonstrating an excellent systemic stability as well as intelligent stimuli-responsive performance within the acidic TME. Furthermore, the in vivo antitumor study revealed that PGlu-PEG/TAT-NPs provided greater antitumor efficacy compared with free DSF and N-NPs with no obvious systemic toxicity. In conclusion, the TME-responsive shell/core composite NPs, consisting of PGlu-PEG and HS-PEG-TAT, could mediate an effective and biocompatible delivery of chemotherapeutic agents with clinical potential.