Metronomic chemotherapy and nanocarrier platforms

The future of metronomic chemotherapy: experimental and computational approaches of drug repurposing

Metronomic chemotherapy (MC), long-term continuous administration of anticancer drugs, is gaining attention as an alternative to the traditional maximum tolerated dose (MTD) chemotherapy. By combining MC with other treatments, the therapeutic efficacy is enhanced while minimizing toxicity. MC employs multiple mechanisms, making it a versatile approach against various cancers. However, drug resistance limits the long-term effectiveness of MC, necessitating ongoing development of anticancer drugs. Traditional drug discovery is lengthy and costly due to processes like target protein identification, virtual screening, lead optimization, and safety and efficacy evaluations. Drug repurposing (DR), which screens FDA-approved drugs for new uses, is emerging as a cost-effective alternative. Both experimental and computational methods, such as protein binding assays, in vitro cytotoxicity tests, structure-based screening, and several types of association analyses (Similarity-Based, Network-Based, and Target Gene), along with retrospective clinical analyses, are employed for virtual screening. This review covers the mechanisms of MC, its application in various cancers, DR strategies, examples of repurposed drugs, and the associated challenges and future directions.

Modulating cancer mechanopathology to restore vascular function and enhance immunotherapy

Solid tumor pathology, characterized by abnormalities in the tumor microenvironment (TME), challenges therapeutic effectiveness. Mechanical factors, including increased tumor stiffness and accumulation of intratumoral forces, can determine the success of cancer treatments, defining the tumor's "mechanopathology" profile. These abnormalities cause extensive vascular compression, leading to hypoperfusion and hypoxia. Hypoperfusion hinders drug delivery, while hypoxia creates an unfavorable TME, promoting tumor progression through immunosuppression, heightened metastatic potential, drug resistance, and chaotic angiogenesis. Strategies targeting TME mechanopathology, such as vascular and stroma normalization, hold promise in enhancing cancer therapies with some already advancing to the clinic. Normalization can be achieved using anti-angiogenic agents, mechanotherapeutics, immune checkpoint inhibitors, engineered bacterial therapeutics, metronomic nanomedicine, and ultrasound sonopermeation. Here, we review the methods developed to rectify tumor mechanopathology, which have even led to cures in preclinical models, and discuss their bench-to-bedside translation, including the derivation of biomarkers from tumor mechanopathology for personalized therapy.

Nanoparticle-mediated metronomic chemotherapy in cancer: A paradigm of precision and persistence

Current methods of cancer therapy have demonstrated enormous potential in tumor inhibition. However, a high dosage regimen of chemotherapy results in various complications which affect the normal body cells. Tumor cells also develop resistance against the prescribed drugs in the whole treatment regimen increasing the risk of cancer relapse. Metronomic chemotherapy is a modern treatment method that involves administering drugs at low doses continuously, allowing the drug sufficient time to take its effect. This method ensures that the toxicity of the drugs is to a minimum in comparison to conventional chemotherapy. Nanoparticles have shown efficacy in delivering drugs to the tumor cells in various cancer therapies. Combining nanoparticles with metronomic chemotherapy can yield better treatment results. This combination stimulates the immune system, improving cancer cells recognition by immune cells. Evidence from clinical and pre-clinical trials supports the use of metronomic delivery for drug-loaded nanoparticles. This review focuses on the functionalization of nanoparticles for improved drug delivery and inhibition of tumor growth. It emphasizes the mechanisms of metronomic chemotherapy and its conjunction with nanotechnology. Additionally, it explores tumor progression and the current methods of chemotherapy. The challenges associated with nano-based metronomic chemotherapy are outlined, paving the way for prospects in this dynamic field.

Accumulation of liposomes in metastatic tumor sites is not necessary for anti-cancer drug efficacy

BACKGROUND

The tumor microenvironment is profoundly heterogeneous particularly when comparing sites of metastases. Establishing the extent of this heterogeneity may provide guidance on how best to design lipid-based drug delivery systems to treat metastatic disease. Building on our previous research, the current study employs a murine model of metastatic cancer to explore the distribution of ~ 100 nm liposomes.

METHODS

Female NCr nude mice were inoculated with a fluorescently labeled, Her2/neu-positive, trastuzumab-resistant breast cancer cell line, JIMT-1mkate, either in the mammary fat pad to create an orthotopic tumor (OT), or via intracardiac injection (IC) to establish tumors throughout the body. Animals were dosed with fluorescent and radio-labeled liposomes. In vivo and ex vivo fluorescent imaging was used to track liposome distribution over a period of 48 h. Liposome distribution in orthotopic tumors was compared to sites of tumor growth that arose following IC injection.

RESULTS

A significant amount of inter-vessel heterogeneity for DiR distribution was observed, with most tumor blood vessels showing little to no presence of the DiR-labelled liposomes. Further, there was limited extravascular distribution of DiR liposomes in the perivascular regions around DiR-positive vessels. While all OT tumors contained at least some DiR-positive vessels, many metastases had very little or none. Despite the apparent limited distribution of liposomes within metastases, two liposomal drug formulations, Irinophore C and Doxil, showed similar efficacy for both the OT and IC JIMT-1mkate models.

CONCLUSION

These findings suggest that liposomal formulations achieve therapeutic benefits through mechanisms that extend beyond the enhanced permeability and retention effect.

CAG (cytarabine, aclarubicin and granulocyte colony-stimulating factor) regimen for core binding factor acute myeloid leukaemia with measurable residual disease

Acute myeloid leukaemia (AML) with t (8;21) or inv (16), called core binding factor (CBF) AML, has a favourable prognosis. However, some CBF-AML patients have persistent measurable residual disease (MRD) and are more likely to relapse after standard chemotherapy treatment. The CAG regimen, composed of cytarabine, aclarubicin and granulocyte colony-stimulating factor, has been proven to be effective and safe in treating refractory AML patients. We performed a retrospective study to evaluate the efficacy of the CAG regimen to eliminate MRD detected by RUNX1::RUNX1T1 and CBFβ::MYH11 transcript levels by quantitative polymerase chain reaction (Q-PCR) among 23 patients. Molecular response was defined as the ratio of fusion transcript after treatment to that before treatment less than or equal to 0.5. The molecular response rate and median decrease ratio of fusion transcripts at the molecular level of the CAG regimen were 52% and 0.53, respectively. The median fusion transcripts before CAG treatment was 0.25% whereas after CAG was 0.11%. Among the 15 patients who had a poor molecular response to the high/intermediate-dose cytarabine regimen, the median decrease ratios of transcripts at the molecular level of high/intermediate-dose cytarabine and CAG were 1.55 and 0.53 (P = 0.028), respectively, and 6 of 15 patients achieved a molecular response to CAG (40%). The median disease-free survival was 18 months, and the overall survival rate at 3 years among all patients was 72.7% ± 10.7%. The common grades 3-4 adverse events were nausea (100%), thrombocytopenia (39%) and neutropenia (37.5%). The CAG regimen may have activity in CBF-AML patients and could provide a new option for patients who have a poor molecular response to high/intermediate-dose cytarabine.

Multifunctional Nano-Biomaterials for Cancer Therapy via Inducing Enhanced Immunogenic Cell Death

Immunotherapy is considered to be one of the most promising methods to overcome cancer. Immunogenic cell death (ICD), as a special form of cell death that can trigger an antitumor immune response, has attracted increasing attention for cancer immunotherapy. Presently, ICD-mediating immunotherapy needs to overcome many hurdles including a lack of targeted delivery systems for ICD inducers, insufficient antitumor immunity, and the immunosuppressive tumor microenvironment. Recent research has demonstrated that nano-biomaterials exhibit unique biochemphysical properties at the nanoscale, providing a prospective approach to overcoming these obstacles. In this review, the authors first survey the occurrence, processes, and detection methods of ICD. Subsequently, the recent advances of nano-biomaterials applied to enhance ICD according to the key steps in the process of ICD, particularly with a focus on the mechanisms and lifting schemes are investigated. Finally, based on the achievement in the representative studies, the prospects and challenges of nanotechnology in ICD for cancer therapy are discussed to enable clinical translation.

Normalizing tumor microenvironment with nanomedicine and metronomic therapy to improve immunotherapy

Nanomedicine offered hope for improving the treatment of cancer but the survival benefits of the clinically approved nanomedicines are modest in many cases when compared to conventional chemotherapy. Metronomic therapy, defined as the frequent, low dose administration of chemotherapeutics – is being tested in clinical trials as an alternative to the conventional maximum tolerated dose (MTD) chemotherapy schedule. Although metronomic chemotherapy has not been clinically approved yet, it has shown better survival than MTD in many preclinical studies. When beneficial, metronomic therapy seems to be associated with normalization of the tumor microenvironment including improvements in tumor perfusion, tissue oxygenation and drug delivery as well as activation of the immune system. Recent preclinical studies suggest that nanomedicines can cause similar changes in the tumor microenvironment. Here, by employing a mathematical framework, we show that both approaches can serve as normalization strategies to enhance treatment. Furthermore, employing murine breast and fibrosarcoma tumor models as well as ultrasound shear wave elastography and contrast-enhanced ultrasound, we provide evidence that the approved nanomedicine Doxil can induce normalization in a dose-dependent manner by improving tumor perfusion as a result of tissue softening. Finally, we show that pretreatment with a normalizing dose of Doxil can improve the efficacy of immune checkpoint inhibition.

Evaluation of solid tumor response to sequential treatment cycles via a new computational hybrid approach

The development of an in silico approach that evaluates and identifies appropriate treatment protocols for individuals could help grow personalized treatment and increase cancer patient lifespans. With this motivation, the present study introduces a novel approach for sequential treatment cycles based on simultaneously examining drug delivery, tumor growth, and chemotherapy efficacy. This model incorporates the physical conditions of tumor geometry, including tumor, capillary network, and normal tissue assuming real circumstances, as well as the intravascular and interstitial fluid flow, drug concentration, chemotherapy efficacy, and tumor recurrence. Three treatment approaches-maximum tolerated dose (MTD), metronomic chemotherapy (MC), and chemo-switching (CS)-as well as different chemotherapy schedules are investigated on a real tumor geometry extracted from image. Additionally, a sensitivity analysis of effective parameters of drug is carried out to evaluate the potential of using different other drugs in cancer treatment. The main findings are: (i) CS, MC, and MTD have the best performance in reducing tumor cells, respectively; (ii) multiple doses raise the efficacy of drugs that have slower clearance, higher diffusivity, and lower to medium binding affinities; (iii) the suggested approach to eradicating tumors is to reduce their cells to a predetermined rate through chemotherapy and then apply adjunct therapy.

Metronomic Anti-Cancer Therapy: A Multimodal Therapy Governed by the Tumor Microenvironment

Simple Summary

Metronomic chemotherapy with different mechanisms of action against cancer cells and their microenvironment represents an exceptional holistic cancer treatment. Each type of tumor has its own characteristics, including each individual tumor in each patient. Understanding the complexity of the dynamic interactions that take place between tumor and stromal cells and the microenvironment in tumor progression and metastases, as well as the response of the host and the tumor itself to anticancer therapy, will allow therapeutic actions with long-lasting effects to be implemented using metronomic regimens. This study aims to highlight the complexity of cellular interactions in the tumor microenvironment and summarize some of the preclinical and clinical results that explain the multimodality of metronomic therapy, which, together with its low toxicity, supports an inhibitory effect on the primary tumor and metastases. We also highlight the possible use of nano-therapeutic agents as good partners for metronomic chemotherapy.

Abstract

The concept of cancer as a systemic disease, and the therapeutic implications of this, has gained special relevance. This concept encompasses the interactions between tumor and stromal cells and their microenvironment in the complex setting of primary tumors and metastases. These factors determine cellular co-evolution in time and space, contribute to tumor progression, and could counteract therapeutic effects. Additionally, cancer therapies can induce cellular and molecular responses in the tumor and host that allow them to escape therapy and promote tumor progression. In this study, we describe the vascular network, tumor-infiltrated immune cells, and cancer-associated fibroblasts as sources of heterogeneity and plasticity in the tumor microenvironment, and their influence on cancer progression. We also discuss tumor and host responses to the chemotherapy regimen, at the maximum tolerated dose, mainly targeting cancer cells, and a multimodal metronomic chemotherapy approach targeting both cancer cells and their microenvironment. In a combination therapy context, metronomic chemotherapy exhibits antimetastatic efficacy with low toxicity but is not exempt from resistance mechanisms. As such, a better understanding of the interactions between the components of the tumor microenvironment could improve the selection of drug combinations and schedules, as well as the use of nano-therapeutic agents against certain malignancies.

Oral lipid nanomedicines: Current status and future perspectives in cancer treatment

Oral anticancer drugs have earned a seat at the table, as the need for homecare treatment in oncology has increased. Interest in this field is growing as a result of their proven efficacy, lower costs and positive patient uptake. However, the gastrointestinal barrier is still the main obstacle to surmount in chemotherapeutic oral delivery. Anticancer nanomedicines have been proposed to solve this quandary. Among these, lipid nanoparticles are described to be efficiently absorbed while protecting drugs from early degradation in hostile environments. Their intestinal lymphatic tropism or mucoadhesive/penetrative properties give them unique characteristics for oral administration. Considering that chronic cancer cases are increasing over time, it is important to be able to provide treatments with low toxicity and low prices. The challenges, opportunities and therapeutic perspectives of lipid nanoparticles in this area will be discussed in this review, taking into consideration the pre-clinical and clinical progress made in the last decade.

Combination of metronomic administration and target delivery strategies to improve the anti-angiogenic and anti-tumor effects of triptolide

The metronomic administration of a low-dose cytotoxic agent with no prolonged drug-free breaks is an anti-angiogenic cancer treatment method. The use of nano-formulations in this manner enhances anti-tumor efficacy and reduces toxicity by inhibiting angiogenic activity, reduces adverse effects, and changes the biodistribution of TP in the body, steering TP away from potentially endangering healthy tissues. The present study uses liposomes and Asn-Gly-Arg (NGR) peptide conjugated aminopeptidase N(APN)-targeted liposomes for triptolide (TP), as a model for the investigation of targeted metronomic administration and subsequent effects on the toxicity profile and efficacy of the chemotherapeutic agent. Metronomic NGR-PEG-TP-LPs have been found to have enhanced anti-tumor activity, a phenomenon that is attributed to an increase in angiogenic inhibition properties. In vitro experiments demonstrate that the viability, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) are obviously suppressed in comparison with that of other treatment groups. In vivo experiments also demonstrate that the anti-tumor efficacy of targeted metronomic administration is superior to that of liposome-administered treatments given at maximum tolerated dose (MTD) schemes, as is evidenced by markedly decreased tumor volume, vessel density, and the volume of circulating endothelial progenitor cells (CEPCs) in serum. Moreover, we observed that the metronomic administration of NGR-PEG-TP-LPs could elevate thrombospondin-1 (TSP-1) expression in tumors, a finding that is consistent with the promotion of TSP-1 secretion specifically from HUVECs. Additionally, metronomic NGR-PEG-TP-LPs have minimal drug-associated toxicity (weight loss, hepatotoxicity and nephrotoxicity in mice). Our research demonstrates the significance of targeted metronomic administration using liposomes for anti-angiogenic cancer therapy.

TGF-β inhibition combined with cytotoxic nanomedicine normalizes triple negative breast cancer microenvironment towards anti-tumor immunity

Tumor normalization strategies aim to improve tumor blood vessel functionality (i.e., perfusion) by reducing the hyper-permeability of tumor vessels or restoring compressed vessels. Despite progress in strategies to normalize the tumor microenvironment (TME), their combinatorial antitumor effects with nanomedicine and immunotherapy remain unexplored. Methods: Here, we re-purposed the TGF-β inhibitor tranilast, an approved anti-fibrotic and antihistamine drug, and combined it with Doxil nanomedicine to normalize the TME, increase perfusion and oxygenation, and enhance anti-tumor immunity. Specifically, we employed two triple-negative breast cancer (TNBC) mouse models to primarily evaluate the therapeutic and normalization effects of tranilast combined with doxorubicin and Doxil. We demonstrated the optimized normalization effects of tranilast combined with Doxil and extended our analysis to investigate the effect of TME normalization to the efficacy of immune checkpoint inhibitors. Results: Combination of tranilast with Doxil caused a pronounced reduction in extracellular matrix components and an increase in the intratumoral vessel diameter and pericyte coverage, indicators of TME normalization. These modifications resulted in a significant increase in tumor perfusion and oxygenation and enhanced treatment efficacy as indicated by the notable reduction in tumor size. Tranilast further normalized the immune TME by restoring the infiltration of T cells and increasing the fraction of T cells that migrate away from immunosuppressive cancer-associated fibroblasts. Furthermore, we found that combining tranilast with Doxil nanomedicine, significantly improved immunostimulatory M1 macrophage content in the tumorigenic tissue and improved the efficacy of the immune checkpoint blocking antibodies anti-PD-1/anti-CTLA-4. Conclusion: Combinatorial treatment of tranilast with Doxil optimizes TME normalization, improves immunostimulation and enhances the efficacy of immunotherapy.

Apoferritin nanocages with Au nanoshell coating as drug carrier for multistimuli-responsive drug release

Cancer is one of the major causes of mortality worldwide. Therefore, it is necessary to provide an effective method of tumor therapy. Herein, we designed a new type of composite particle, apoferritin (APO) encapsulated doxorubicin (DOX), and the surface of APO was modified with Au nanoshell. As a nanocarrier, APO can carry chemotherapy drug DOX (APODOX) and release drug under acidic and high temperature conditions to reduce side effects of anticancer drugs. After covering Au nanoshell (APODOX-Au), the photothermal effect can be produced because of the unique surface plasmon resonance properties of gold nanoshell. This nanoplatform also provides the multi-stimuli responsive drug release system, which can achieve drug release in different conditions and have great potential in biomedical applications. Our investigation has demonstrated that APODOX-Au has good stability, high dispersibility and biocompatibility in vitro. The strong near-infrared absorption and good photothermal effect make sure the quick response to environmental changes (pH, temperature) to achieve drug release. These findings indicate that these nanoparticles have a potential application value in cancer treatment.

Rationale for the use of metronomic chemotherapy in gastrointestinal cancer

INTRODUCTION

Metronomic chemotherapy (mCT) is endowed with various properties, ranging from antiangiogenic to immunomodulation, and may revert tumor resistance to conventional drug administration. A variety of antineoplastic agents displayed activity when administered with metronomic schedules in preclinical models of gastrointestinal cancers. However, most of the field is still unexplored.

AREAS COVERED

Herein, the authors review the existing literature from PubMed, concerning the use of mCT in gastrointestinal oncology.

EXPERT OPINION

A mounting body of evidence is emerging in support of mCT as a treatment option for gastrointestinal tumors, but the frequent signs of clinical activity inconsistently translate into a benefit for survival. Research in this field should focus on providing high-quality evidence on the safety and efficacy of mCT, with more prospective, comparative trials; identifying the subgroups of patients for whom mCT would be the best approach; establishing standardized protocols based on mCT pharmacokinetics and pharmacodynamics; developing drug activity biomarkers. mCT is also potentially suitable for combinations with targeted antiangiogenic drugs and may be incorporated with conventional administration into dual regimens.