Nanotechnology-based combinational drug delivery: an emerging approach for cancer therapy

Combination therapy for the treatment of cancer is becoming more popular because it generates synergistic anticancer effects, reduces individual drug-related toxicity and suppresses multi-drug resistance through different mechanisms of action. In recent years, nanotechnology-based combination drug delivery to tumor tissues has emerged as an effective strategy by overcoming many biological, biophysical and biomedical barriers that the body stages against successful delivery of anticancer drugs. The sustained, controlled and targeted delivery of chemotherapeutic drugs in a combination approach enhanced therapeutic anticancer effects with reduced drug-associated side effects. In this article, we have reviewed the scope of various nanotechnology-based combination drug delivery approaches and also summarized the current perspective and challenges facing the successful treatment of cancer.     

Nanoparticle-based combination therapy toward overcoming drug resistance in cancer

The use of multiple therapeutic agents in combination has become the primary strategy to treat drug resistant cancers. However, administration of combinatorial regimens is limited by the varying pharmacokinetics of different drugs, which results in inconsistent drug uptake and suboptimal drug combination at the tumor sites. Conventional combination strategies in aim to maximize therapeutic efficacy based on maximum tolerated dose does not account for the therapeutic synergism that is sensitive to both dosing and scheduling of multiple drugs. In the present review, we will discuss the development of multidrug-loaded nanoparticles against drug resistant cancers. Nanoparticle-based combination therapy against experimental multidrug resistant (MDR) cancer models will be summarized. In addition, we will highlight the recent advances in nanoparticle-based combination strategies against clinical cancer drug resistance, including co-encapsulation of drugs with different physicochemical properties, ratiometric control over drug loading, and temporal sequencing on drug release. These emerging strategies promise novel and better tailored combinatorial regimens for clinical cancer treatment.     

Pharmacometrics in dose finding or dose optimization of anti-retroviral and anti-tubercular drugs

Drug development continues to be time consuming, expensive and less efficient, while drug therapy is often administered at suboptimal levels. This is particularly true with anti-infectives for HIV and tuberculosis. The application of pharmacometric principles and models to drug development and pharmacotherapy will improve the drug approval process and selection of optimal dosage regimens or therapeutic combinations. In this review we mainly focus on the utilities of pharmacometrics in the dose selections of anti-retroviral and anti-tubercular drugs. We will examine how pharmacometrics have been useful in the area of dose selections, preclinical to clinical scaling, subpopulation selections, combination therapies, adherence assessments, and resistance prevention dosing strategies.     

克服肿瘤多药耐药的药物共递送纳米载体的设计及研究新方向

多药耐药（multidrug resistance，MDR）是肿瘤治疗成功的主要障碍，药物共递送纳米载体因其肿瘤靶向、控制释放、一致的药动学曲线而被认为是克服MDR的有效策略。本综述总结了当前克服MDR的药物共递送纳米载体的设计思路，并分析了具有前景的研究方向，包括精确药物负载纳米载体、呈时序释放的纳米载体和对肿瘤微环境设计纳米载体，这些新兴策略为临床肿瘤治疗提供了新颖且更好的定制组合方案。     

Emerging drugs for endometrial cancer

Introduction: From the dualistic classification that divides endometrial cancer (EC) into two types with distinct underlying molecular profiling, histopathology and clinical behavior, arises a deeper understanding of the carcinogenesis pathways. EC treatment comprises different and multimodal therapeutic approaches, such as chemotherapy, radiation therapy or combinations of novel drugs; however, few of these regimens have truly improved progression-free or survival rates in advanced and metastatic settings.

Areas covered: We reviewed the main molecular pathways involved in EC carcinogenesis through a wide literature search of novel compounds that alone or in combination with traditional drugs have been investigated or are currently under investigation in randomized clinical trials.

Expert opinion: The molecular therapies mainly discussed in this review are potential therapeutic candidates for more effective and specific treatments. In the genomic era, a deeper knowledge about molecular characteristics of cancer provides the hope for the development of better therapeutic approaches. Targeting both genetic and epigenetic alterations, attacking tumor cells using cell-surface markers overexpressed in tumor tissue, reactivating antitumor immune responses and identifying predictive biomarkers represent the emerging strategies and the major challenges.     

Monoclonal antibody‐based therapeutics,targeting the epidermal growth factor receptor family: from herceptin to Pan HER

Objectives

Monoclonal antibody‐based of cancer therapy has been considered as one of the most successful therapeutic strategies for both haematologic malignancies and solid tumours in the last two decades. Epidermal growth factor receptor (EGFR ) family signalling pathways play a key role in the regulation of cell proliferation, survival and differentiation. Hence, anti‐EGFR family mA bs is one of the most promising approaches in cancer therapy.

Key findings

Here, recent advances in anti‐EGFR mA b including approved or successfully tested in preclinical and clinical studies have been reviewed. Although we focus on monoclonal antibodies against the EGF receptor, but the mechanisms underlying the effects of EGFR ‐specific mA b in cancer therapy, to some extend the resistance to existing anti‐EGFR therapies and some therapeutic strategies to overcome resistance such as combination of mA bs on different pathways are briefly discussed as well.

Summary

The EGFR family receptors, is considered as an attractive target for mA b development to inhibit their consecutive activities in tumour growth and resistance. However, due to resistance mechanisms, the combination therapies may become a good candidate for targeting EGFR family receptors.

     

Preclinical development of cancer stem cell drugs

Background: Despite recent progress in cancer treatment, the current cancer chemotherapy can mainly produce remission but often fails to cure cancer due to the existence of cancer stem cells. The emerging cancer stem cell hypothesis offers new insight into the failure of current cancer drugs and suggests new approaches for improved understanding of cancer biology and cancer drug development. Objective: In this review, we discuss the concept of cancer stem cells, origin of cancer stem cells and different approaches for isolating or enriching cancer stem cells. We also review the resistance of cancer stem cells to standard chemotherapy and radiation therapy and potential mechanisms for the resistance. Finally, based on the current knowledge on cancer stem cells, we discuss potential approaches for developing new drugs that target cancer stem cells and propose new methods for evaluation of cancer stem cell drugs. Conclusion: Improved cancer treatment is likely to be achieved by a combination of drugs that kill both replicating cancer cells and more quiescent cancer stem cells.     

Biomarkers and multiple drug resistance in breast cancer

Breast cancer, the most common form of cancer among women in North America and almost all of Europe, is a significant health problem in terms of both morbidity and mortality. It is estimated that each year this disease is diagnosed in over one million people worldwide and is the cause of more than 400,000 deaths. Although chemotherapy forms part of a successful treatment regime in many cases, as few as 50% patients may benefit from this, as a result of intrinsic or acquired multiple drug resistance (MDR). Through the use of in vitro cell culture models, a number of mechanisms of MDR have been identified; many, if not all, of which may contribute to breast cancer resistance in the clinical setting. This phenomenon is complicated by the likely multi-factorial nature of clinical resistance combined with the fact that, although apparently studied extensively in breast cancer, reported analyses have been performed using a range of analytical techniques; many on small sub-groups of patients, with different clinicopathological characteristics and receiving a range of therapeutic approaches. Larger defined studies, using standardised genomic and proteomics profiling approaches followed by functional genomics studies, are necessary in order to definitively establish the degree of complexity contributing to drug resistance and to identify novel therapeutic approaches - possibly involving chemotherapy, drug resistance modulators, and novel targeted therapies - to combat this disease.     

Recent trends in cancer drug resistance reversal strategies using nanoparticles

INTRODUCTION: Resistance to chemotherapy is a major obstacle in the successful amelioration of tumors in many cancer patients. Resistance is either intrinsic or acquired, involving mechanisms such as genetic aberrations, decreased influx and increased efflux of drugs. Strategies for the reversal of resistance involve the alteration of enzymes responsible for drug resistance, the modulation of proteins regulating apoptosis mechanisms and improving the uptake of drugs using nanotechnology. Novel strides in the reversal of drug resistance are emerging, involving the use of nanotechnology, targeting stem cells, etc. AREAS COVERED: This paper reviews the most recent cancer drug reversal strategies involving nanotechnology for targeting cancer cells and cancer stem cells (CSCs), for enhanced uptake of micro- and macromolecular inhibitors. EXPERT OPINION: Nanotechnology used in conjunction with existing therapies, such as gene therapy and P-glycoprotein inhibition, has been shown to improve the reversal of drug resistance; the mechanisms involved in this include specific targeting of drugs and nucleotide therapeutics, enhanced cellular uptake of drugs and improved bioavailability of drugs with poor physicochemical characteristics. Important strategies in the reversal of drug resistance include: a multifunctional nanoparticulate system housing a targeting moiety; therapeutics to kill resistant cancer cells and CSCs; cytotoxic drugs and a tumor microenvironment stimuli-responsive element, to release the encapsulated therapeutics.     

Optimum management of nausea and vomiting in cancer chemotherapy

Nausea and vomiting continue to be critical problems in cancer chemotherapy, although considerable progress has been made toward understanding the neuropharmacological mechanisms of vomiting and how chemotherapeutic agents and antiemetics affect these mechanisms. The principles of behavioural psychology have also been applied in an effort to understand and effectively manage these complications which have potentially serious consequences. For example, there is now some degree of rationality to our use of metoclopramide for cisplatin-induced nausea and vomiting, the use of combination antiemetic regimens, and use of lorazepam for the prevention (albeit unproven) of anticipatory nausea and vomiting. It must be admitted, however, that our approach is for the most part still empirical. Selecting an antiemetic programme is not a simple task. The emetogenic potential of the chemotherapy being used, the presence of coexisting diseases, the potential toxicity of the antiemetic drug and whether antiemetic therapy is to take place in the hospital or in an outpatient setting, the familiarity of the clinician with the various antiemetic therapies, and cost are all factors which need to be considered. Although phenothiazines remain the standard treatment, they are of little value against chemotherapy programmes that produce moderate or severe problems. Newer pharmacological approaches including butyrophenones, cannabinoids, metoclopramide, high-dose corticosteroids, and benzodiazepines have shown increased antiemetic efficacy, as have combinations of these agents which are directed against multiple sites of emetogenic activity. The role of behavioural therapies, which have been shown to be effective particularly in children and in anticipatory nausea and vomiting, needs to be more firmly established. Rather than recommending a given antiemetic programme for any particular chemotherapy, it is preferable to think in terms of initial approaches and how they can be modified. No one antiemetic programme is effective or safe in all situations.     

Modeling therapy resistance in genetically engineered mouse cancer models

Resistance to anti-cancer drugs is a major obstacle in successful treatment of cancer. Multidrug resistance is not only observed with clinically established chemotherapeutics, but also with novel targeted therapies. Although a range of drug resistance mechanisms have been identified up till now, for most drugs it is still controversial which mechanisms are responsible for resistance and therapy failure in patients. Hence, the development of strategies to circumvent drug resistance is often unfocused. Since several years genetically engineered mouse models have been generated which develop tumors that closely resemble cancer in humans. We argue that such models can be used to investigate relevant in vivo mechanisms of resistance. This includes the analysis of intrinsic and acquired resistance, and the characterization of residual cells which survive the treatment. In such model systems different drugs and therapy combinations can be optimized prior to clinical trials.     

Bugs and drugs: oncolytic virotherapy in combination with chemotherapy

Single agent therapies are rarely successful in treating cancer, particularly at metastatic or end stages, and survival rates with monotherapies alone are generally poor. The combination of multiple therapies to treat cancer has already driven significant improvements in the standard of care treatments for many types of cancers. The first combination treatments exploited for cancer therapy involved the use of several cytotoxic chemotherapy agents. Later, with the development of more targeted agents, the use of novel, less toxic drugs, in combination with the more classic cytotoxic drugs has proven advantageous for certain cancer types. Recently, the combination of oncolytic virotherapy with chemotherapy has shown that the use of these two therapies with very distinct anti-tumor mechanisms may also lead to synergistic interactions that ultimately result in increased therapeutic effects not achievable by either therapy alone. The mechanisms of synergy between oncolytic viruses (OVs) and chemotherapeutic agents are just starting to be elucidated. It is evident, however, that the success of these OV-drug combinations depends greatly on the particular OV, the drug(s) selected, and the cancer type targeted. This review summarizes the different OV-drug combinations investigated to date, including the use of second generation armed OVs, which have been studied with the specific purpose of generating synergistic interactions with particular chemotherapy agents. The known mechanisms of synergy between these OV-drug combinations are also summarized. The importance of further investigating these mechanisms of synergy will be critical in order to maximize the therapeutic efficacy of OV-drug combination therapies in the future.     

Recent advances in novel targeted therapies for HER2-positive breast cancer

The monoclonal antibody trastuzumab has improved the outcomes of patients with breast cancer that overexpresses the human epidermal growth factor receptor 2 (HER2). However, despite this advancement, many tumors develop resistance and novel approaches are needed. Recently, a greater understanding of cellular biology has translated into the development of novel anti-HER2 agents with varying mechanisms of action. The small molecule tyrosine kinase inhibitor lapatinib has demonstrated activity in HER2-positive metastatic breast cancer (MBC) and in the preoperative setting. Pertuzumab is a monoclonal antibody with a distinct binding site from trastuzumab, which inhibits receptor dimerization. In recent studies, the addition of pertuzumab to combination therapy has led to improvements in progression-free survival in patients with HER2-positive MBC and higher response rates in the preoperative setting. An alternative approach is the use of novel antibody-drug conjugates such as trastuzumab-emtansine, which recently demonstrated activity in MBC. Neratinib, a pan-HER tyrosine kinase inhibitor, which irreversibly inhibits HER1 and HER2, also has proven activity in MBC. A range of compounds is being developed to attempt to overcome trastuzumab resistance by targeting heat shock protein 90, a molecular chaperone required for the stabilization of cellular proteins. Furthermore, agents are being developed to inhibit the mammalian target of rapamycin, a downstream component of the PTEN/PI3K pathway, which has been implicated in trastuzumab resistance. Finally, there are emerging data indicating that combinations of anti-HER2 agents may circumvent resistance mechanisms and improve patient outcomes. In this review, recent data on these emerging agents and novel combinations for HER2-positive breast cancer are discussed.     

Exploiting evolution to treat drug resistance: combination therapy and the double bind

Although many anticancer therapies are successful in killing a large percentage of tumor cells when initially administered, the evolutionary dynamics underpinning tumor progression mean that, often, resistance is an inevitable outcome. Research in the field of ecology suggests that an evolutionary double bind could be an effective way to treat tumors. In an evolutionary double bind two therapies are used in combination such that evolving resistance to one leaves individuals more susceptible to the other. In this paper we present a general evolutionary game theory framework of a double bind to study the effect that such an approach would have in cancer. Furthermore we use this mathematical framework to understand recent experimental results that suggest a synergistic effect between a p53 cancer vaccine and chemotherapy. Our model recapitulates the latest experimental data and provides an explanation for its effectiveness based on the commensalistic relationship between the tumor phenotypes.     

Hematological side-effect profiles of individualized chemotherapy regimen for recurrent ovarian cancer

The long-term results for patients with recurrent ovarian cancer (ROC) are poor. There is a need to optimize treatment strategies to improve outcome by avoiding ineffective regimens which are often associated with exacerbated side-effects. Individualized chemotherapy regimens guided by a chemosensitivity assay (ATP-tumor chemosensitivity assay) have already been used successfully to direct chemotherapy. Taking the results of this assay into account, application of drug combinations appears more advisable. Here we present a systematic evaluation of toxicities seen with individualized chemotherapy for ROC. A total of 62 patients who received 314 cycles of antineoplastic therapies were evaluated. Three single agents (topotecan, paclitaxel and gemcitabine) and five combinations (cisplatin/gemcitabine, carbopatin/gemcitabine, gemcitabine/treosulfan, mitoxantrone/paclitaxel and carboplatin/paclitaxel) were examined. With respect to myelotoxicity, most single agents except topotecan revealed favorable results in comparison to drug combinations. However, this observation lacks statistical significance. Generally, severe myelosuppression was rare. The highest incidence of leukopenia was seen in regimens with mitoxantrone/paclitaxel or gemcitabine/treosulfan, respectively. Thrombocytopenia accompanied most commonly a topotecan therapy. In the present study combination regimens tend to be more toxic than monotherapies. When response rates are comparable, empirically chosen treatment combination therapies should only be practiced in carefully planned clinical studies.     

Machine learning to design antimicrobial combination therapies: Promises and pitfalls

Combination therapies can overcome antimicrobial resistance (AMR) and repurpose existing drugs. However, the large combinatorial space to explore presents a daunting challenge. In response, machine learning (ML) algorithms are being applied to identify novel synergistic drug interactions from millions of potential combinations. Here, we compare ML-based approaches for combination therapy design based on the type of input information used, specifically: drug properties, microbial response and infection microenvironment. We also provide a compilation of publicly available drug interaction datasets relevant to AMR. Finally, we discuss limitations of current ML-based methods and propose new strategies for designing efficacious combination therapies. These include consideration of in vivo conditions, design of sequential combinations, enhancement of model interpretability and application of deep learning algorithms.     

Recent trends in cancer drug resistance reversal strategies using nanoparticles

Introduction: Resistance to chemotherapy is a major obstacle in the successful amelioration of tumors in many cancer patients. Resistance is either intrinsic or acquired, involving mechanisms such as genetic aberrations, decreased influx and increased efflux of drugs. Strategies for the reversal of resistance involve the alteration of enzymes responsible for drug resistance, the modulation of proteins regulating apoptosis mechanisms and improving the uptake of drugs using nanotechnology. Novel strides in the reversal of drug resistance are emerging, involving the use of nanotechnology, targeting stem cells, etc.

Areas covered: This paper reviews the most recent cancer drug reversal strategies involving nanotechnology for targeting cancer cells and cancer stem cells (CSCs), for enhanced uptake of micro- and macromolecular inhibitors.

Expert opinion: Nanotechnology used in conjunction with existing therapies, such as gene therapy and P-glycoprotein inhibition, has been shown to improve the reversal of drug resistance; the mechanisms involved in this include specific targeting of drugs and nucleotide therapeutics, enhanced cellular uptake of drugs and improved bioavailability of drugs with poor physicochemical characteristics. Important strategies in the reversal of drug resistance include: a multifunctional nanoparticulate system housing a targeting moiety; therapeutics to kill resistant cancer cells and CSCs; cytotoxic drugs and a tumor microenvironment stimuli-responsive element, to release the encapsulated therapeutics.     

Tumour heterogeneity and drug resistance: personalising cancer medicine through functional genomics

Intrinsic and acquired drug resistance leads to the eventual failure of cancer treatment regimens in the majority of advanced solid tumours. Understanding drug resistance mechanisms will prove vital in the future development of personalised therapeutic approaches. Functional genomics technologies may permit the discovery of predictive biomarkers by unravelling pathways involved in drug resistance and allow the systematic identification of novel therapeutic targets. Such technologies offer the opportunity to develop personalised treatments and diagnostic tools that may improve the survival and quality of life of patients with cancer. However, despite progress in biomarker and drug target discovery, inter-tumour and intra-tumour molecular heterogeneity will limit the effective treatment of this disease. Combining an improved understanding of cancer cell survival mechanisms associated with intra-tumour heterogeneity and drug resistance may allow the selection of patients for specific treatment regimens that will maximise benefit, limit the acquisition of drug resistance and lessen the impact of deleterious side effects.     

Molecular targeted therapy in melanoma: a way to reverse resistance to conventional drugs

Cutaneous melanoma is the most aggressive skin cancer. Beside surgery, it is treated with chemotherapy and immunotherapy. However, many patients relapse after adjuvant therapy. The recent identification of several key molecular pathways implicated in the pathogenesis of melanoma is spreading development of a number of new translational targeted therapies which could play an important role in overcoming or minimizing resistance to chemotherapeutic drugs and proapoptotic therapies. This review summarizes environmental factors and the most significant molecular events involved in melanoma pathogenesis, disclosing mechanisms responsible for drug resistance and pointing out the clinical view for emerging targeted therapies. Standard therapies and an update on the current clinical trials are also described.     

Cancer vaccines entering Phase III clinical trials

The last 10 years have seen a growth in the number of tumour antigens identified from immune responses raised in patients. The discovery that tumours can be recognised by the immune system stimulated a great deal of work characterising the molecular mechanisms underlying immune recognition. This in turn has led to an impressive array of immunological approaches to the generation of cancer vaccines; these range from molecularly defined T cell epitopes, antibody-based vaccines, cytokine therapies, immune modulators and DNA vaccines, to whole cell vaccines and, more recently, combinations of these methods. Many of these approaches have entered Phase I/II trials and have shown interesting clinical results. Moreover, they have extended our knowledge of the immune system and our understanding of the mechanisms required to design a successful cancer vaccine. This review outlines some of the approaches that have led to some of these vaccines entering Phase III clinical trials, discusses their modes of action and reports on their current status in trial.