A pharmacokinetic and pharmacodynamic study on metronomic irinotecan in metastatic colorectal cancer patients

Thrombospondin-1 in drug activity and tumor response to therapies

Thrombospondins (TSPs) have numerous different roles in cancer, regulating the behavior of cancer cells and non-neoplastic cells, and defining the responses of tumor cells to environmental changes, thorough their ability to orchestrate cellular and molecular interactions in the tumor microenvironment (TME). As a result of these activities, TSPs can also control drug delivery and activity, tumor response and resistance to therapies, with different outcomes depending on the nature of TSP-interacting cell types, receptors, and ligands, in a highly context-dependent manner. This review, focusing primarily on TSP-1, discusses the effects of TSPs on tumor response to chemotherapy, antiangiogenic, low-dose metronomic chemotherapy, immunotherapy, and radiotherapy, by analyzing TSP activity on different cell compartments - tumor cells, vascular endothelial cells and immune cells. We review evidence of the value of TSPs, specifically TSP-1 and TSP-2, as biomarkers of prognosis and tumor response to therapy. Finally, we examine possible approaches to develop TSP-based compounds as therapeutic tools to potentiate the efficacy of anticancer therapy.

Lanthanide (Eu3+/Tb3+)-Loaded γ-Cyclodextrin Nano-Aggregates for Smart Sensing of the Anticancer Drug Irinotecan

The clinical use of anticancer drugs necessitates new technologies for their safe, sensitive, and selective detection. In this article, lanthanide (Eu³⁺ and Tb³⁺)-loaded γ-cyclodextrin nano-aggregates (ECA and TCA) are reported, which sensitively detects the anticancer drug irinotecan by fluorescence intensity changes. Fluorescent lanthanide (Eu³⁺ and Tb³⁺) complexes exhibit high fluorescence intensity, narrow and distinct emission bands, long fluorescence lifetime, and insensitivity to photobleaching. However, these lanthanide (Eu³⁺ and Tb³⁺) complexes are essentially hydrophobic, toxic, and non-biocompatible. Lanthanide (Eu³⁺ and Tb³⁺) complexes were loaded into naturally hydrophilic γ-cyclodextrin to form fluorescent nano-aggregates. The biological nontoxicity and cytocompatibility of ECA and TCA fluorescent nanoparticles were demonstrated by cytotoxicity experiments. The ECA and TCA fluorescence nanosensors can detect irinotecan selectively and sensitively through the change of fluorescence intensity, with detection limits of 6.80 μM and 2.89 μM, respectively. ECA can safely detect irinotecan in the cellular environment, while TCA can detect irinotecan intracellularly and is suitable for cell labeling.

Drug delivery strategies in maximizing anti-angiogenesis and anti-tumor immunity

Metronomic chemotherapy has been shown to elicit anti-tumor immune response and block tumor angiogenesis distinct from that observed with maximal tolerated dose (MTD) therapy. This review delves into the mechanisms behind anti-tumor immunity and seeks to identify the differential effect of dosing regimens, including daily low-dose and medium-dose intermittent chemotherapy (MEDIC), on both innate and adaptive immune populations involved in observed anti-tumor immune response. Given reports of VEGF/VEGFR blockade antagonizing anti-tumor immunity, drug choice, dose, and selective delivery determined by advanced formulations/vehicles are highlighted as potential sources of innovation for identifying anti-angiogenic modalities that may be combined with metronomic regimens without interrupting key immune players in the anti-tumor response. Engineered drug delivery mechanisms that exhibit extended and local release of anti-angiogenic agents both alone and in combination with chemotherapeutic treatments have also been demonstrated to elicit a potent and potentially systemic anti-tumor immune response, favoring tumor regression and stasis over progression. This review examines this interplay between various cancer models, the host immune response, and select anti-cancer agents depending on drug dosing, scheduling/regimen, and delivery modality.

Metronomic Therapy in Oral Squamous Cell Carcinoma

Metronomic therapy is characterized by drug administration in a low-dose, repeated, and regular manner without prolonged drug-free interval. The two main anticancer mechanisms of metronomic therapy are antiangiogenesis and immunomodulation, which have been demonstrated in several delicate in vitro and in vivo experiments. In contrast to the traditional maximum tolerated dose (MTD) dosing of chemotherapy, metronomic therapy possesses comparative efficacy but greatlydecreases the incidence and severity of treatment side-effects. Clinical trials of metronomic anticancer treatment have revealed promising results in a variety cancer types and specific patient populations such as the elderly and pediatric malignancies. Oral cavity squamous cell carcinoma (OCSCC) is an important health issue in many areas around the world. Long-term survival is about 50% in locally advanced disease despite having high-intensity treatment combined surgery, radiotherapy, and chemotherapy. In this article, we review and summarize the essence of metronomic therapy and focus on its applications in OCSCC treatment.

Metronomic Chemotherapy

Simple Summary

The present article reviews the state of the art of metronomic chemotherapy use to treat the principal types of cancers, namely breast, non-small cell lung cancer and colorectal ones, and of the most recent progresses in understanding the underlying mechanisms of action. Areas of novelty, in terms of new regimens, new types of cancer suitable for Metronomic chemotherapy (mCHT) and the overview of current ongoing trials, along with a critical review of them, are also provided.

Abstract

Metronomic chemotherapy treatment (mCHT) refers to the chronic administration of low doses chemotherapy that can sustain prolonged, and active plasma levels of drugs, producing favorable tolerability and it is a new promising therapeutic approach in solid and in hematologic tumors. mCHT has not only a direct effect on tumor cells, but also an action on cell microenvironment, by inhibiting tumor angiogenesis, or promoting immune response and for these reasons can be considered a multi-target therapy itself. Here we review the state of the art of mCHT use in some classical tumour types, such as breast and no small cell lung cancer (NSCLC), see what is new regarding most recent data in different cancer types, such as glioblastoma (GBL) and acute myeloid leukemia (AML), and new drugs with potential metronomic administration. Finally, a look at the strategic use of mCHT in the context of health emergencies, or in low –and middle-income countries (LMICs), where access to adequate healthcare is often not easy, is mandatory, as we always need to bear in in mind that equity in care must be a compulsory part of our medical work and research.

Camptothecin Induces PD-L1 and Immunomodulatory Cytokines in Colon Cancer Cells

: Background: Immunotherapy has changed the options for the treatment of various cancer types, but not colon cancer. Current checkpoint blockade approaches are ineffective in a large proportion of colon cancer cases, necessitating studies to elucidate its mechanisms and to identify new targets and strategies against it. Methods: Here, we examined Programmed Death-Ligand 1(PD-L1), cytokine and receptor responses of colon cancer cells exposed to camptothecin (CPT), a clinically used topoisomerase inhibitor. Colon cancer cells were treated with CPT at concentrations of up to 10 µM, and the expressions of PD-L1 and immunoregulatory cytokine genes and receptors were analyzed. Results: PD-L1, a current immunotherapy target for various cancers, was shown to be upregulated in colon cancer cells independent of the cellular p53 status. In metastasis-derived SW620 cells, CPT most extensively upregulated cytokines with T-cell attraction or growth factor functions. Of those modulated genes, SPP1, IL1RN, IL1A, TNFSF13B, OSM, and CSF3 had the most clinical relevance, as their high expression was associated with poor cancer patient overall survival. Conclusions: These findings highlight the need to examine, in preclinical and clinical situations, the potential benefits of combining topoisomerase inhibitors with immune-checkpoint inhibitors.

Metronomic Chemotherapy: A Systematic Review of the Literature and Clinical Experience

Metronomic chemotherapy, continuous and dose-dense administration of chemotherapeutic drugs with lowered doses, is being evaluated for substituting, augmenting, or appending conventional maximum tolerated dose regimens, with preclinical and clinical studies for the past few decades. To date, the principle mechanisms of its action include impeding tumoral angiogenesis and modulation of hosts' immune system, affecting directly tumor cells, their progenitors, and neighboring stromal cells. Its better toxicity profile, lower cost, and easier use are main advantages over conventional therapies. The evidence of metronomic chemotherapy for personalized medicine is growing, starting with unfit elderly patients and also for palliative treatment. The literature reviewed in this article mainly demonstrates that metronomic chemotherapy is advantageous for selected patients and for certain types of malignancies, which make it a promising therapeutic approach for filling in the gaps. More clinical studies are needed to establish a solidified role for metronomic chemotherapy with other treatment models in modern cancer management.

Tumor endothelial cells as a potential target of metronomic chemotherapy

Drug resistance and toxic side effects are major therapeutic hurdles affecting cancer patients receiving conventional chemotherapy based on the maximum tolerated dose. Metronomic chemotherapy (MCT), a new therapeutic approach developed to avoid these problems generally, consists of the continuous administration of low-dose cytotoxic agents without extended intervals. This therapy targets the tumor microenvironment, rather than exerting a direct effect on tumor cells. As a result, the MCT regimen functionally impairs tumor endothelial cells and circulating endothelial progenitor cells, leading to tumor dormancy via anti-angiogenesis. Over the past 10 years, several studies have highlighted the impact of MCT on the tumor microenvironment and angiogenesis and demonstrated its potential as a switch from the pro-angiogenic to the anti-angiogenic state. However, the mechanisms of action are still obscure. Here, we systematically review the evidence regarding the anti-angiogenic potential of MCT as a crucial determinant of tumor dormancy and cancer treatment.

Oral administration of irinotecan in patients with solid tumors: an open-label, phase I, dose escalating study evaluating safety, tolerability and pharmacokinetics

BACKGROUND

Oral drug formulations have several advantages compared to intravenous formulation. Apart from patient convenience and favorable pharmacoeconomics, they offer the possibility of frequent drug administration at home. In this study, we present a new oral irinotecan formulation designed as an enteric coated immediate release tablet which in pre-clinical studies has shown good exposure with low variability.

METHODS

A phase I, dose escalating study to assess safety, tolerability, pharmacokinetics and efficacy of an oral irinotecan formulation and to establish the maximum tolerated dose (MTD). Each treatment cycle was once-daily irinotecan for 14 days followed by 1 week rest.

RESULTS

25 patients were included across four cohorts; 3 patients were included in cohort 1 (20 mg/m²), 7 patients were included in cohort 2 (30 mg/m²), 3 patients were included in cohort 3 (25 mg/m²) and 12 patients were included in cohort 4 (21 mg/m²). Median age was 67 years, 52% were performance status (PS) 0 while 48% were PS 1. Median number of prior therapies was 3 (range 1-6). MTD was established at 21 mg/m². No responses were observed. Nine patients (36%) had stable disease (SD), lasting median 19 weeks (range 7-45 weeks). Among these five patients had previously received irinotecan. No grade 3/4 hematologic toxicities were reported. Totally six patients experienced grade 1/2 anemia, three patients had grade 1/2 leucopenia and 1 patient had grade 1 thrombocytopenia. Most common non-hematological grade 1 and 2 adverse events were nausea, fatigue, diarrhea, vomiting and cholinergic syndrome. Grade 3 toxicities included diarrhea, fatigue, nausea and vomiting, no grade 4 events were reported. PK data showed consistent daily exposures during treatment at days 1 and 14 and no drug accumulation. SN-38 interpatient variability was in the same range as after infusion.

CONCLUSIONS

Oral irinotecan was generally well tolerated; side effects were manageable and similar in type to those observed with intravenous irinotecan. Hematological toxicities were few and only grade 1/2. In this heavily pre-treated patient population, oral irinotecan demonstrated activity even among patients previously treated with irinotecan.

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.

Does metronomic chemotherapy induce tumor angiogenic dormancy? A review of available preclinical and clinical data

Tumor dormancy is the ability of cancer cells to survive in a non-proliferating state. This condition can depend on three main mechanisms: cell cycle arrest (quiescence or cell dormancy), immunosurveillance (immunologic dormancy), or lack of functional blood vessels (angiogenic dormancy). In particular, under angiogenic dormancy, cancer cell proliferation is counterbalanced by apoptosis owing to poor vascularization, impeding tumor mass expansion beyond a microscopic size, with an asymptomatic and non-metastatic state. Tumor vasculogenic or non-angiogenic switch is essential to promote escape from tumor dormancy, leading to tumor mass proliferation and metastasis. In avascular lesions angiogenesis process results blocked from the equilibrium between pro- and anti-angiogenic factors, such as vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1), respectively. The angiogenic switch mainly depends on the disruption of this balance, in favor of pro-angiogenic factors, and on the recruitment of circulating endothelial progenitors (CEPs) that promote the formation of new blood vessels. Metronomic chemotherapy, the regular intake of doses able to sustain low but active concentrations of chemotherapeutic drugs during protracted time periods, is an encouraging therapeutic approach that has shown to upregulate anti-angiogenic factors such as TSP-1 and decline pro-angiogenic factors such as VEGF, suppressing the proangiogenic cells such as CEPs. In this perspective, metronomic chemotherapy may be one of the available therapeutic approaches capable to modulate favorably the angiogenic tumor dormancy, but further research is essential to better define this particular characteristic.

Synergistic efficacy of irinotecan and sunitinib combination in preclinical models of anaplastic thyroid cancer

The identification of new therapeutic strategies is urgently needed for the management of patients affected by anaplastic thyroid cancer (ATC) due to their short survival and poor prognosis. Aim of the study was to determine the activity of the combination irinotecan/sunitinib on ATC cell growth in vitro and the antitumor effects in vivo. Proliferation assays were performed for 72 h on ATC cell lines exposed to the combination of SN-38, the active metabolite of irinotecan, and sunitinib. The simultaneous combination of sunitinib and SN-38, quantified by the combination index, determined a high synergism on ATC cells, increasing the intracellular concentrations of SN-38. Moreover, the synergistic combination greatly decreases the gene expression and the protein levels of vascular endothelial growth factor, colony stimulating factor 1 and ATP-binding cassette transporter G2 in ATC cells. A significant in vivo antitumor effect was observed in ATC xenografts with the simultaneous combination of irinotecan and sunitinib if compared to monotherapy. The simultaneous combination of irinotecan and sunitinib, in vitro and in vivo demonstrated a significant, synergistic ATC antitumor activity, suggesting a possible and rapid translation of this schedule into the clinics.

Metronomic chemotherapy in metastatic colorectal cancer

Overall survival and quality of life of patients with metastatic colorectal cancer (mCRC) have improved due to the development of standard systemic treatment. However, many patients are still suffering from the eventual progression of cancer, treatment-related toxicities, and the economic burden of new drugs. Salvage or maintenance therapy, which consistently controls or stabilizes tumor progression without debilitating quality of life, is required. Recently, metronomic capecitabine maintenance therapy after disease control using conventional chemotherapy with maximal tolerated doses has demonstrated beneficial results in a phase III trial. Metronomic chemotherapy has been known to control tumors through antiangiogenesis and immunomodulation as well as a direct effect on tumor-initiating cells. It has the characteristics of being minimally toxic, inexpensive, and durable for maintaining disease stabilization. Therefore, patients with mCRC, who tend to be elderly and frail and have been previously treated, might be suitable for metronomic therapeutic strategies. Furthermore, antiangiogenic therapy has been an important component in treating mCRC, but the schedules and doses of metronomic chemotherapy have not yet been established. Here we review translational and clinical research on metronomic chemotherapy in colorectal cancer (CRC).

Metronomic chemotherapy and immunotherapy in cancer treatment

Systemic chemotherapy given at maximum tolerated doses (MTD) has been the mainstay of cancer treatment for more than half a century. In some chemosensitive diseases such as hematologic malignancies and solid tumors, MTD has led to complete remission and even cure. The combination of maintenance therapy and standard MTD also can generate good disease control; however, resistance to chemotherapy and disease metastasis still remain major obstacles to successful cancer treatment in the majority of advanced tumors. Metronomic chemotherapy, defined as frequent administration of chemotherapeutic agents at a non-toxic dose without extended rest periods, was originally designed to overcome drug resistance by shifting the therapeutic target from tumor cells to tumor endothelial cells. Metronomic chemotherapy also exerts anti-tumor effects on the immune system (immunomodulation) and tumor cells. The goal of immunotherapy is to enhance host anti-tumor immunities. Adding immunomodulators such as metronomic chemotherapy to immunotherapy can improve the clinical outcomes in a synergistic manner. Here, we review the anti-tumor mechanisms of metronomic chemotherapy and the preliminary research addressing the combination of immunotherapy and metronomic chemotherapy for cancer treatment in animal models and in clinical setting.

Metronomics in the neoadjuvant and adjuvant treatment of breast cancer

The concept of metronomic chemotherapy (MC) has evolved from a descriptive preclinical phenomenon encompassing inhibition of angiogenesis to a clinically validated treatment concept involving multiple potential mechanisms of action. Clinicians are progressively more incline to consider MC as a component of mainstream medical oncology practice in advanced breast cancer. However, more recently MC has been tested even in the adjuvant/neoadjuvant setting, taking the opportunity to obtain tumor specimens and blood samples, in order to identify tumor-specific or patient-specific biomarkers for personalizing treatments. In addition, the antiangiogenic and pro-immune nature of metronomic chemotherapy made triple negative breast cancer (TNBC) a good candidate for exploring low-dose maintenance treatment in the adjuvant setting or in combination with immunomodulatory drugs. The potential development of MC in breast cancer pass through the research to identify biomarkers and individual tumor characteristics that can better address the use of this treatment strategy in the future. Finally, the subjective attitude of patients represents one of the major factors that influence the choice and acceptance of a therapeutic program. Personal preference and considerations about quality of life should guide the treatment choice eventually prioritizing the use of MC. Nevertheless, more robust data from randomized phase III trials are needed in the future, in order to make clinicians more confident in using metronomic strategies.

Immunological and angiogenic markers during metronomic temozolomide and cyclophosphamide in canine cancer patients

Metronomic chemotherapy stimulates the immune response via depletion of regulatory T cells (Tregs) and suppresses angiogenesis by modulating the secretion of thrombospondin-1 (TSP-1) and vascular endothelial growth factor (VEGF). In this study, blood was collected from 10 healthy dogs and from 30 canine cancer patients before and 2 and 4 weeks after treatment with metronomic temozolomide (6.6 mg m^-2 ), cyclophosphamide (12.5 mg m^-2 ) or cyclophosphamide and temozolomide. The percentage of circulating CD25⁺ Foxp3⁺ CD4⁺ Tregs and the plasma levels of TSP-1 and VEGF were measured. There was a significant difference in the percentage of Tregs between cancer patients and healthy dogs. A significant decrease in Tregs was noted in patients treated with metronomic cyclophosphamide and the combination. Treatment with temozolomide had no effect on the percentage of Tregs. TSP-1 and VEGF levels were, respectively, significantly lower and higher in cancer patients than in healthy dogs, but they were not influenced by any of the studied metronomic treatment regimens.

Metronomic oral vinorelbine in advanced breast cancer and non-small-cell lung cancer: current status and future development

Metronomic chemotherapy (mCT), a frequent administration of low-dose chemotherapy, allows prolonged treatment duration and minimizes the toxicity of standard-dose chemotherapy. mCT has multiple actions against cancer cells including inhibition of angiogenesis and modulation of the immune system. A number of studies lend support to the clinical efficacy of mCT in advanced breast cancer and non-small-cell lung cancer. However, further evidence is necessary to describe the optimal use of mCT and to identify suitable patients. Oral vinorelbine has emerged as a promising metronomic treatment in patients with metastatic breast cancer and non-small-cell lung cancer and is the only orally available microtubule-targeting agent. This paper reviews current evidence on metronomic oral vinorelbine, discusses its management and defines a suitable patient profile on the basis of a workshop of Italian experts.

Metronomic chemotherapy: an attractive alternative to maximum tolerated dose therapy that can activate anti-tumor immunity and minimize therapeutic resistance

The administration of chemotherapy at reduced doses given at regular, frequent time intervals, termed 'metronomic' chemotherapy, presents an alternative to standard maximal tolerated dose (MTD) chemotherapy. The primary target of metronomic chemotherapy was originally identified as endothelial cells supporting the tumor vasculature, and not the tumor cells themselves, consistent with the emerging concept of cancer as a systemic disease involving both tumor cells and their microenvironment. While anti-angiogenesis is an important mechanism of action of metronomic chemotherapy, other mechanisms, including activation of anti-tumor immunity and a decrease in acquired therapeutic resistance, have also been identified. Here we present evidence supporting a mechanistic explanation for the improved activity of cancer chemotherapy when administered on a metronomic, rather than an MTD schedule and discuss the implications of these findings for further translation into the clinic.

Lessons from the Fourth Metronomic and Anti-angiogenic Therapy Meeting, 24-25 June 2014, Milan

The Fourth Metronomic and Anti-angiogenic Therapy Meeting was held in Milan 24–25 June 2014. The meeting was a true translational meeting where researchers and clinicians shared their results, experiences, and insights in order to continue gathering useful evidence on metronomic approaches. Several speakers emphasised that exact mechanisms of action, best timing, and optimal dosage are still not well understood and that the field would learn a lot from ancillary studies performed during the clinical trials of metronomic chemotherapies. From the pre-clinical side, new research findings indicate additional possible mechanisms of actions of metronomic schedule on the immune and blood vessel compartments of the tumour micro-environment. New clinical results of metronomic chemotherapy were presented in particular in paediatric cancers [especially neuroblastoma and central nervous system (CNS) tumours], in angiosarcoma (together with beta-blockers), in hepatocellular carcinoma, in prostate cancer, and in breast cancer. The use of repurposed drugs such as metformin, celecoxib, or valproic acid in the metronomic regimen was reported and highlighted the potential of other candidate drugs to be repurposed. The clinical experiences from low- and middle-income countries with affordable regimens gave very encouraging results which will allow more patients to be effectively treated in economies where new drugs are not accessible. Looking at the impact of metronomic approaches that have been shown to be effective, it was admitted that those approaches were rarely used in clinical practice, in part because of the absence of commercial interest for companies. However, performing well-designed clinical trials of metronomic and repurposing approaches demonstrating substantial improvement, especially in populations with the greatest unmet needs, may be an easier solution than addressing the financial issue. Metronomics should always be seen as a chance to come up with new innovative affordable approaches and not as a cheap rescue strategy.

Intermittent metronomic drug schedule is essential for activating antitumor innate immunity and tumor xenograft regression

Metronomic chemotherapy using cyclophosphamide (CPA) is widely associated with antiangiogenesis; however, recent studies implicate other immune-based mechanisms, including antitumor innate immunity, which can induce major tumor regression in implanted brain tumor models. This study demonstrates the critical importance of drug schedule: CPA induced a potent antitumor innate immune response and tumor regression when administered intermittently on a 6-day repeating metronomic schedule but not with the same total exposure to activated CPA administered on an every 3-day schedule or using a daily oral regimen that serves as the basis for many clinical trials of metronomic chemotherapy. Notably, the more frequent metronomic CPA schedules abrogated the antitumor innate immune and therapeutic responses. Further, the innate immune response and antitumor activity both displayed an unusually steep dose-response curve and were not accompanied by antiangiogenesis. The strong recruitment of innate immune cells by the 6-day repeating CPA schedule was not sustained, and tumor regression was abolished, by a moderate (25%) reduction in CPA dose. Moreover, an ∼20% increase in CPA dose eliminated the partial tumor regression and weak innate immune cell recruitment seen in a subset of the every 6-day treated tumors. Thus, metronomic drug treatment must be at a sufficiently high dose but also sufficiently well spaced in time to induce strong sustained antitumor immune cell recruitment. Many current clinical metronomic chemotherapeutic protocols employ oral daily low-dose schedules that do not meet these requirements, suggesting that they may benefit from optimization designed to maximize antitumor immune responses.

Anti-angiogenesis participates in antitumor effects of metronomic capecitabine on colon cancer

Inhibitory effects and potential mechanisms of capecitabine metronomic chemotherapy on colon cancer were investigated in this study. Metronomic chemotherapy with fluorouracil or capecitabine inhibited proliferation of colon cancer cells both in vitro and in vivo. Capecitabine metronomic chemotherapy demonstrated equal effects as CTX metronomic chemotherapy. Metronomic capecitabine or CTX chemotherapy decreased vascular endothelial growth factor (VEGF) but elevated thrombospondin-1 (TSP-1) expression, reduced CEP levels and decreased microvessel density (MVD). These results indicated anti-angiogenesis may be correlated with the antitumor effects of metronomic capecitabine in colon cancer.

Macromolecular prodrug that provides the irinotecan (CPT-11) active-metabolite SN-38 with ultralong half-life, low C(max), and low glucuronide formation

We have recently reported a chemical approach for half-life extension that utilizes β-eliminative linkers to attach amine-containing drugs or prodrugs to macromolecules. The linkers release free drug or prodrug over periods ranging from a few hours to over 1 year. We adapted these linkers for use with phenol-containing drugs. Here, we prepared PEG conjugates of the irinotecan (CPT-11) active metabolite SN-38 via a phenyl ether that release the drug with predictable long half-lives. Pharmacokinetic studies in the rat indicate that, in contrast to other SN-38 prodrugs, the slowly released SN-38 shows a very low C(max), is kept above target concentrations for extended periods, and forms very little SN-38 glucuronide (the precursor of enterotoxic SN-38). The low SN-38 glucuronide is attributed to low hepatic uptake of SN-38. These macromolecular prodrugs have unique pharmacokinetic profiles that may translate to less intestinal toxicity and interpatient variability than the SN-38 prodrugs thus far studied.

A phase 1 trial of imatinib, bevacizumab, and metronomic cyclophosphamide in advanced colorectal cancer

Background:

This phase 1 clinical trial was conducted to determine the safety, maximum-tolerated dose (MTD), and pharmacokinetics of imatinib, bevacizumab, and metronomic cyclophosphamide in patients with advanced colorectal cancer (CRC).

Methods:

Patients with refractory stage IV CRC were treated with bevacizumab 5 mg kg⁻¹ i.v. every 2 weeks (fixed dose) plus oral cyclophosphamide q.d. and imatinib q.d. or b.i.d. in 28-day cycles with 3+3 dose escalation. Response was assessed every two cycles. Pharmacokinetics of imatinib and cyclophosphamide and circulating tumour, endothelial, and immune cell subsets were measured.

Results:

Thirty-five patients were enrolled. Maximum-tolerated doses were cyclophosphamide 50 mg q.d., imatinib 400 mg q.d., and bevacizumab 5 mg kg⁻¹ i.v. every 2 weeks. Dose-limiting toxicities (DLTs) included nausea/vomiting, neutropaenia, hyponatraemia, fistula, and haematuria. The DLT window required expansion to 42 days (1.5 cycles) to capture delayed toxicities. Imatinib exposure increased insignificantly after adding cyclophosphamide. Seven patients (20%) experienced stable disease for >6 months. Circulating tumour, endothelial, or immune cells were not associated with progression-free survival.

Conclusion:

The combination of metronomic cyclophosphamide, imatinib, and bevacizumab is safe and tolerable without significant drug interactions. A subset of patients experienced prolonged stable disease independent of dose level.

Orally administered S-1 suppresses circulating endothelial cell counts in metastatic breast cancer patients

BACKGROUND

S-1 is an oral cytotoxic preparation that contains tegafur. Gamma-butyrolactone (GBL) is a metabolite of tegafur that is known to suppress vascular endothelial growth factor (VEGF)-mediated angiogenic activity. The aim of this study was to determine the change in circulating endothelial cell (CEC) counts, GBL levels, and angiogenesis-related factors during S-1 administration in metastatic breast cancer (MBC) patients.

METHODS

Patients with HER2-negative MBC were eligible. S-1 was administered orally twice daily in a 4 week on/2 week off cycle until disease progression or unacceptable toxicity occurred. Blood was collected on the following: days 1, 43, 85 (before each cycle of S-1 administration), days 15, 57 (1 h after S-1 administration), and day 29. The CellSearch(®) system was used to count the CECs. The gas chromatographic-mass spectrometric method was used to measure plasma GBL and 5-FU levels. Levels of VEGF were assayed by enzyme-linked immunosorbent assay.

RESULTS

A total of 18 patients were enrolled. The plasma GBL levels on days 15 and 57 were 41.3 ± 15.8 and 41.0 ± 11.2 ng/mL, respectively. The CEC levels decreased on day 15, and significantly low levels were maintained until day 85 (P = 0.002 vs day 1). The plasma VEGF levels significantly decreased on day 15 (P = 0.012 vs day 1) and had a tendency to decrease until day 57.

CONCLUSIONS

This exploratory study showed that GBL levels increased, VEGF levels decreased, and CEC levels were suppressed during S-1 administration. S-1 appears to have anti-angiogenic activity.

Metronomic chemotherapy for cancer treatment: a decade of clinical studies

PURPOSE

Over the past few years, more and more new selective molecules directed against specific cellular targets have become available for cancer therapy, leading to impressive improvements. In this evolving scenario, a new way of delivering older cytotoxic drugs has also been developing. Many studies demonstrated that several cytotoxic drugs have antiangiogenic properties if administered frequently and at lower doses compared with standard schedules containing maximal tolerated doses (MTD). Such a new strategy, named metronomic chemotherapy, focuses on a different target: the slowly proliferating tumour endothelial cells. About 10 years ago, metronomic chemotherapy was firstly enunciated and hereafter many clinical experiences were published related to almost any cancer disease. This review analyses available studies dealing with metronomic chemotherapy and its combination with several targeted agents in solid tumours.

METHODS

A computerized literature search of MEDLINE was performed using the following search terms: metronomic OR "continuous low dose" AND chemotherapy AND cancer OR solid tumours.

RESULTS

Satisfactory results have been achieved in diverse tumour types, such as breast and prostate cancer or paediatric sarcomas. Moreover, many studies have reported that metronomic chemotherapy determined minimal toxicity compared to MTD chemotherapy. Overall, published series on metronomic schedules are very heterogeneous often reporting on retrospective data, while only very few studies were randomized trials. These limitations still prevent to draw definitive conclusions in diverse tumour types.

CONCLUSIONS

Large well-designed studies are eagerly awaited for confirming the promises of metronomic schedules and their combinations with targeted molecules.

The pharmacological bases of the antiangiogenic activity of paclitaxel

In the mid 1990s, researchers began to investigate the antiangiogenic activity of paclitaxel as a possible additional mechanism contributing to its antineoplastic activity in vivo. In the last decade, a number of studies showed that paclitaxel has antiangiogenic activity that could be ascribed to the inhibition of either tubule formation or cell migration, and to an antiproliferative effect towards activated endothelial cells. Furthermore, paclitaxel was shown to downregulate VEGF and Ang-1 expression in tumor cells, and to increase the secretion of TSP-1 in the tumor microenvironment. Moreover, the new pharmaceutical formulations of paclitaxel (such as liposome-encapsulated paclitaxel, ABI-007, and paclitaxel entrapped in emulsifying wax nanoparticles) enhanced the in vivo antiangiogenic activity of the drug. Thus, the preclinical data of paclitaxel may be exploited to implement a novel and rational therapeutic strategy to control tumor progression in patients.

Metronomic oral topotecan prolongs survival and reduces liver metastasis in improved preclinical orthotopic and adjuvant therapy colon cancer models

OBJECTIVE

Advanced and recurrent diseases are the major causes of death in colon cancer. No standard preclinical model addresses advanced disease and spontaneous metastasis after orthotopic tumour growth. In this study, the authors report the establishment of such standardised orthotopic mouse models of colon cancer and their use in evaluating metronomic topotecan alone or in combination with standard chemotherapy.

DESIGN

Human colon cancer cell lines, transfected with human chorionic gonadotropin and luciferase, were injected orthotopically into the caecal wall of severe combined immunodeficient mice, intrasplenically or subcutaneously. For adjuvant therapy, caecal resections were performed 3-5 weeks after tumour cell injection. Chemotherapy drugs tested included uracil/tegafur, folinic acid, oxaliplatin, topotecan, pazopanib and various combinations.

RESULTS

Subcutaneous tumours showed exaggerated sensitivity to treatment by delayed tumour growth (p=0.002) and increased survival (p=0.0064), but no metastatic spread. Intrasplenic cell injection resulted in rapid and extensive but artefactual metastasis without treatment effect. Intracaecal cell injection with tumour take rates of 87.5-100% showed spontaneous metastases at clinically relevant rates. Metronomic topotecan significantly polonged survival and reduced metastasis. In the adjuvant setting, metronomic maintenance therapy (after FOLFOX-like induction) prolonged survival compared with vehicle controls (p=0.0003), control followed by topotecan (p=0.0161) or FOLFOX-like therapy (p=0.0003).

CONCLUSION

The refined orthotopic implantation technique proved to be a clinically relevant model for metastasis and therapy studies. Furthermore, metronomic therapy with oral topotecan may be promising to consider for clinical trials of metastatic colon cancer and long-term adjuvant maintenance therapy of colon cancer.

Lipid-based nanoformulation of irinotecan: dual mechanism of action allows for combination chemo/angiogenic therapy

A number of studies have outlined the antiangiogenic effects of cytotoxic agents when administered frequently at low doses. These studies suggest that the effect of the cytotoxic agent is on the vasculature within the tumor and it is assumed that there is little or negligible cytotoxicity. Liposomal drug delivery systems have the ability to provide a dual mechanism of activity where tumor accumulation can deliver high local concentrations of the drug at the site of action with concomitant slow release of the drug from carriers in the blood compartment that results in antivascular effects, similar to that achieved when dosing frequently at low levels. Although this dual mechanism of activity may be linked to other lipid nanoparticle formulations of anticancer drugs, this article summarizes the evidence supporting direct (cytotoxic) and indirect (antivascular) actions of a liposomal formulation of irinotecan.

Clinical, pharmacokinetic and pharmacodynamic evaluations of metronomic UFT and cyclophosphamide plus celecoxib in patients with advanced refractory gastrointestinal cancers

Aims

To evaluate UFT and cyclophosphamide (CTX) based metronomic chemotherapy plus celecoxib (CXB) for the treatment of patients with heavily pre-treated advanced gastrointestinal malignancies.

Methods

Thirty-eight patients received 500 mg/mq² CTX i.v bolus on day 1 and, from day 2, 50 mg/day CTX p.o. plus 100 mg/twice a day UFT p.o. and 200 mg/twice a day CXB p.o. Tegafur, 5-FU, 5-FUH₂, GHB and uracil pharmacokinetics were assessed. Plasma vascular endothelial growth factor (VEGF), soluble VE-cadherin (sVE-C) and thrombospondin-1 (TSP-1) levels were detected by ELISA and real-time PCR of CD133 gene expression on peripheral blood mononuclear cell was also performed.

Results

Seventeen patients (45%) obtained stable disease (SD) with a median duration of 5.8 ms (range, 4.2–7.4). Median progression free survival (PFS) and overall survival (OS) were 2.7 ms (95% CI, 1.6–3.9 ms) and 7.1 ms (95% CI, 4.3–9.9 ms), respectively. No toxicities of grade >1 were observed. Pharmacokinetics of 27 patients (13/14, SD/progressive disease, PD) after the first treatment of UFT revealed that 5-FU AUC and C_max values greater than 1.313 h × μg/ml and 0.501 μg/ml, respectively, were statistically correlated with stabilization of disease and prolonged PFS/OS. VEGF and sVE-C plasma levels were greater in the PD group when compared to SD group. CD133 expression increased only in the PD patients.

Conclusion

Metronomic UFT and CTX with CXB in heavily pre-treated gastrointestinal patients were well tolerated and associated with interesting activity. Potential predictive pharmacokinetic parameters and pharmacodynamic biomarkers have been found.

Inhibition of Cathepsin S by Fsn0503 enhances the efficacy of chemotherapy in colorectal carcinomas

Cathepsin S is a lysosomal cysteine protease implicated in tumourigenesis with key roles in invasion and angiogenesis. We have previously shown that the specific inhibition of Cathepsin S using a monoclonal antibody (Fsn0503) blocks colorectal carcinoma tumour growth and angiogenesis in vivo. We investigated whether Cathepsin S expression levels were affected by chemotherapy in human cancer cell lines by RT-PCR. Using colorectal xenograft models, we examined the therapeutic benefit of Cathepsin S inhibition using Fsn0503 in combination with a metronomic dosing regimen of CPT-11. We analysed the effects of the combination therapy on tumour progression and on tumour vascularisation by immunohistochemical staining of tumours. Cathepsin S expression levels are upregulated in HCT116, LoVo, Colo205 cell lines and HUVECs after exposure to CPT-11 in vitro. The administration of Fsn0503 in combination with CPT-11 significantly attenuated tumour growth in comparison to CPT-11 alone in colorectal HCT116 xenograft models. Furthermore, analysis of tumour vascularisation revealed that this was also significantly disrupted by the combination treatment. These results show that the combination of Cathepsin S inhibition with CPT-11 enhances the therapeutic effect of the chemotherapy. This rationale may have clinical application in the treatment of colorectal cancer upon further evaluation.

Irinotecan synergistically enhances the antiproliferative and proapoptotic effects of axitinib in vitro and improves its anticancer activity in vivo

AIMS

To demonstrate the synergistic antiproliferative and proapoptotic activity of irinotecan and axitinib in vitro and the improvement of the in vivo effects on angiogenesis and pancreatic cancer.

METHODS

Proliferation and apoptotic assays were performed on human dermal microvascular endothelial cells and pancreas cancer (MIAPaCa-2, Capan-1) cell lines exposed to SN-38, the active metabolite of irinotecan, axitinib, or their simultaneous combination for 72 hours. ERK1/2 and Akt phosphorylation, the vascular endothelial growth factor (VEGF), VEGF receptor-2, and thrombospondin-1 (TSP-1) concentration were measured by ELISAs. ATP7A and ABCG2 gene expression was performed with real-time polymerase chain reaction and SN-38 intracellular concentrations were measured by high-performance liquid chromatography. Capan-1 xenografts in nude mice were treated with irinotecan and axitinib alone or in simultaneous combination.

RESULTS

A strong synergistic effect on antiproliferative and proapoptotic activity was found with the axitinib/SN-38 combination on endothelial and cancer cells. ERK1/2 and Akt phosphorylation were significantly inhibited by lower concentrations of the combined drugs in all the cell lines. Axitinib and SN-38 combined treatment greatly inhibited the expression of the ATP7A and ABCG2 genes in endothelial and cancer cells, increasing the SN-38 intracellular concentration. Moreover, TSP-1 secretion was increased in cells treated with both drugs, whereas VEGFR-2 levels significantly decreased. In vivo administration of the simultaneous combination determined an almost complete regression of tumors and tumor neovascularization.

CONCLUSIONS

In vitro results show the highly synergistic properties of simultaneous combination of irinotecan and axitinib on endothelial and pancreas cancer cells, suggesting a possible translation of this schedule into the clinics.

Metronomic irinotecan chemotherapy combined with ultrasound irradiation for a human uterine sarcoma xenograft

Metronomic chemotherapy is the frequent administration of low doses of chemotherapeutic agents targeting tumor-associated endothelial cells. We examined the efficacy of metronomic irinotecan combined with low-intensity ultrasound (US) in human uterine sarcoma and evaluated its antiangiogenesis mechanism by measuring the circulating endothelial progenitor cells (CEP), a surrogate marker of angiogenesis. A human uterine sarcoma cell line, FU-MMT-3, was used in the present study because this tumor is one of the most malignant neoplasms of human solid tumors and it also has a high angiogenesis property. The combination of low-dose irinotecan and US irradiation significantly inhibited the tube formation of HUVEC and vascular endothelial growth factor expression of tumor cells in vitro. The FU-MMT-3 xenografts in nude mice were treated using US at a low intensity (2.0 w/cm(2), 1 MHz) for 4 min three times per week each after the intraperitoneal administration of irinotecan; this treatment was continued for 5 weeks. The tumor vascularity was assessed by contrast-enhanced color Doppler US in real time. The combination treatment significantly inhibited the mobilization of CEP and intratumoral vascularity compared with the control. This combination therapy showed a significant reduction in tumor volume, resulting in a significant prolongation of survival, in comparison with each treatment alone. These results suggest that the effect of metronomic chemotherapy for human uterine sarcoma was accelerated by US irradiation in vivo and this combination might therefore be potentially effective for new cancer therapy.

Thrombospondin-1 as a Paradigm for the Development of Antiangiogenic Agents Endowed with Multiple Mechanisms of Action

Uncontrolled neovascularization occurs in several angiogenesis-dependent diseases, including cancer. Neovascularization is tightly controlled by the balance between angiogenic growth factors and antiangiogenic agents. The various natural angiogenesis inhibitors identified so far affect neovascularization by different mechanisms of action. Thrombospondin-1 (TSP-1) is a matricellular modular glycoprotein that acts as a powerful endogenous inhibitor of angiogenesis. It acts both indirectly, by sequestering angiogenic growth factors and effectors in the extracellular environment, and directly, by inducing an antiangiogenic program in endothelial cells following engagement of specific receptors including CD36, CD47, integrins and proteoglycans (all involved in angiogenesis ). In view of its central, multifaceted role in angiogenesis, TSP-1 has served as a source of antiangiogenic tools, including TSP-1 fragments, synthetic peptides and peptidomimetics, gene therapy strategies, and agents that up-regulate TSP-1 expression. This review discusses TSP-1-based inhibitors of angiogenesis, their mechanisms of action and therapeutic potential, drawing our experience with angiogenic growth factor-interacting TSP-1 peptides, and the possibility of exploiting them to design novel antiangiogenic agents.

Potent preclinical impact of metronomic low-dose oral topotecan combined with the antiangiogenic drug pazopanib for the treatment of ovarian cancer

Low-dose metronomic chemotherapy has shown promising activity in many preclinical and some phase II clinical studies involving various tumor types. To evaluate further the potential therapeutic impact of metronomic chemotherapy for ovarian cancer, we developed a preclinical model of advanced human ovarian cancer and tested various low-dose metronomic chemotherapy regimens alone or in concurrent combination with an antiangiogenic drug, pazopanib. Clones of the SKOV-3 human ovarian carcinoma cell line expressing a secretable beta-subunit of human choriogonadotropic (beta-hCG) protein and firefly luciferase were generated and evaluated for growth after orthotopic (i.p.) injection into severe combined immunodeficient mice; a highly aggressive clone, SKOV-3-13, was selected for further study. Mice were treated beginning 10 to 14 days after injection of cells when evidence of carcinomatosis-like disease in the peritoneum was established as assessed by imaging analysis. Chemotherapy drugs tested for initial experiments included oral cyclophosphamide, injected irinotecan or paclitaxel alone or in doublet combinations with cyclophosphamide; the results indicated that metronomic cyclophosphamide had no antitumor activity whereas metronomic irinotecan had potent activity. We therefore tested an oral topoisomerase-1 inhibitor, oral topotecan, at optimal biological dose of 1 mg/kg/d. Metronomic oral topotecan showed excellent antitumor activity, the extent of which was significantly enhanced by concurrent pazopanib, which itself had only modest activity, with 100% survival values of the drug combination after six months of continuous therapy. In conclusion, oral topotecan may be an ideal agent to consider for clinical trial assessment of metronomic chemotherapy for ovarian cancer, especially when combined with an antiangiogenic drug targeting the vascular endothelial growth factor pathway, such as pazopanib. Mol Cancer Ther; 9(4); 996-1006. (c)2010 AACR.

Practical strategies for suppressing hypoxia-inducible factor activity in cancer therapy

The utility of anti-angiogenic strategies for cancer control is strongly compromised by hypoxia-driven phenotypic changes in cancer cells, which make cancer cells more invasive and more prone to give rise to metastases. A key mediator of this phenotypic shift is the transcription factor hypoxia-inducible factor-1 (HIF-1), which acts directly and indirectly to promote the epidermal-mesenchymal transition, boost cancer invasiveness, increase production of angiogenic factors, and induce chemoresistance. In some cancers, HIF-1 activity is constitutively elevated even in aerobic environments, making the cancer harder to treat and control. Practical strategies for suppressing HIF-1 activation may include the following: inhibiting NF-kappaB activation with salicylic acid and/or silibinin, which should decrease transcription of the HIF-1alpha gene; suppressing translation of HIF-1alpha mRNA with drugs that inhibit mTOR or topoisomerase I; supporting the effective activity of prolyl hydroxylases - which promote proteasomal degradation of HIF-1alpha under aerobic conditions - with antioxidant measures, alpha-ketoglutarate, and possibly dichloroacetate; promoting the O(2)-independent proteasomal degradation of HIF-1alpha with agents that inhibit the chaperone protein Hsp90; and blocking HIF-1 binding to its DNA response elements with anthracyclines. The utility of various combinations of these strategies should be tested in cancer cell cultures and rodent xenograft models; initial efforts in this regard have yielded encouraging results. Comprehensive strategies for suppressing HIF-1 activity can be expected to complement the efficacy of cancer chemotherapy and of effective anti-angiogenic regimens.

Metronomic 5-fluorouracil, oxaliplatin and irinotecan in colorectal cancer

Metronomic chemotherapy (the frequent, long term, low dose administration of chemotherapeutic drugs) is a promising therapy because it enhances the anti-endothelial activity of conventional chemotherapeutics, but with lower or no toxic effects compared to maximum tolerated dose administration. The aims of the present study were to compare, in vitro and in vivo, the antiangiogenic and antitumor activities of metronomic irinotecan (CPT-11), oxaliplatin (L-OHP) and 5-fluorouracil (5-FU) in colorectal cancer and to investigate the metronomic combination of these drugs. In vitro cell proliferation, combination studies and vascular endothelial growth factor (VEGF) secretion analyses were performed on endothelial (HMVEC-d) and colorectal cancer (HT-29) cells exposed for 144 h to metronomic concentrations of SN-38, the active metabolite of CPT-11, L-OHP and 5-FU. HT-29 human colorectal cancer xenograft model was used and tumour growth, microvessel density and VEGF quantification were performed in tumours after the administration of metronomic CPT-11, L-OHP, 5-FU and their simultaneous combination. Low concentrations of SN-38, but not 5-FU and L-OHP, preferentially inhibited endothelial cell proliferation. Simultaneous and continuous exposure of HT-29 and HMVEC-d cells to low concentrations SN-38+L-OHP+5-FU for 144 h showed a strong antagonism and an unfavorable dose-reduction index. Moreover, the ternary combination resulted in a significant increase of VEGF secretion in HT-29 cancer cells. In a xenograft model metronomic CPT-11, but not 5-FU and L-OHP, significantly inhibits HT-29 tumor growth and microvessel density in the absence of toxicity. On the contrary, metronomic 5-FU+L-OHP+CPT-11 therapy did not affect the microvascular count. The metronomic concept might not universally apply to every cytotoxic drug in colorectal cancer and metronomic combination regimens should be used with caution.

Irinophore C, a novel nanoformulation of irinotecan, alters tumor vascular function and enhances the distribution of 5-fluorouracil and doxorubicin

PURPOSE

To examine the antitumor effects of Irinophore C, a nanopharmaceutical formulation of irinotecan, on the tissue morphology and function of tumor vasculature in HT-29 human colorectal tumors.

EXPERIMENTAL DESIGN

Fluorescence microscopy was used to map and quantify changes in tissue density, tumor vasculature, hypoxia, and the distribution of Hoechst 33342, a perfusion marker, and the anticancer drug, doxorubicin. Noninvasive magnetic resonance imaging was used to quantify Ktrans, the volume transfer constant of a solute between the blood vessels and extracellular tissue compartment of the tumor, as a measure of vascular function. Following treatment with Irinophore C, 19F magnetic resonance spectroscopy was used to monitor the delivery of 5-fluorouracil (5-FU) to the tumor tissue, whereas scintigraphy was used to quantify the presence of bound [14C]5-FU.

RESULTS

Irinophore C decreased cell density (P = 8.42 x 10(-5)), the overall number of endothelial cells in the entire section (P = 0.014), tumor hypoxia (P = 5.32 x 10(-9)), and K(trans) (P = 0.050). However, treatment increased the ratio of endothelial cells to cell density (P = 0.00024) and the accumulation of Hoechst 33342 (P = 0.022), doxorubicin (P = 0.243 x 10(-5)), and 5-FU (P = 0.0002) in the tumor. Vascular endothelial growth factor and interleukin-8, two proangiogenic factors, were down-regulated, whereas the antiangiogenic factor TIMP-1 was up-regulated in Irinophore C-treated tumors.

CONCLUSIONS

Irinophore C treatment improves the vascular function of the tumor, thereby reducing tumor hypoxia and increasing the delivery and accumulation of a second drug. Reducing hypoxia would enhance radiotherapy, whereas improving delivery of a second drug to the tumor should result in higher cell kill.