Radiosensitization by Hyperthermia Critically Depends on the Time Interval.

PURPOSE: Hyperthermia is a potent sensitizer of radiation therapy that improves both tumor control and survival in women with locally advanced cervical cancer (LACC). The optimal sequence and interval between hyperthermia and radiation therapy are still under debate. METHODS AND MATERIALS: We investigated the interval and sequence in vitro in cervical cancer cell lines, patient-derived organoids, and SiHa cervical cancer hind leg xenografts in athymic nude mice and compared the results with retrospective results from 58 women with LACC treated with thermoradiotherapy. RESULTS: All 3 approaches confirmed that shortening the interval between hyperthermia and radiation therapy enhanced hyperthermic radiosensitization by 2 to 8 times more DNA double-strand breaks and apoptosis and 10 to 100 times lower cell survival, delayed tumor growth in mice, and increased the 5-year survival rate of women with LACC from 22% (interval ≥80 minutes) to 54% (interval <80 minutes). In vitro and in vivo results showed that the sequence of hyperthermia and radiation therapy did not affect the outcome. CONCLUSIONS: Shortening the interval between hyperthermia and radiation therapy significantly improves treatment outcomes. The sequence of hyperthermia and radiation therapy (before or after) does not seem to matter.

Temperature-sensitive polymers to promote heat-triggered drug release from liposomes: Towards bypassing EPR.

Heat-triggered drug release from temperature-sensitive nanocarriers upon the application of mild hyperthermia is a promising approach to achieve site-specific delivery of drugs. The combination of mild hyperthermia (41-42 °C) and temperature-sensitive liposomes (TSL) that undergo lipid phase-transition and drug release has been studied extensively and has shown promising therapeutic outcome in a variety of animal tumor models as well as initial indications of success in humans. Sensitization of liposomes to mild hyperthermia by means of exploiting the thermal behavior of temperature-sensitive polymers (TSP) provides novel opportunities. Recently, TSP-modified liposomes (TSPL) have shown potential for enhancing tumor-directed drug delivery, either by triggered drug release or by triggered cell interactions in response to heat. In this review, we describe different classes of TSPL, and analyze and discuss the mechanisms and kinetics of content release from TSPL in response to local heating. In addition, the impact of lipid composition, polymer and copolymer characteristics, serum components and PEGylation on the mechanism of content release and TSPL performance is addressed. This is done from the perspective of rationally designing TSPL, with the overall goal of conceiving efficient strategies to increase the efficacy of TSPL plus hyperthermia to improve the outcome of targeted anticancer therapy.

Externally triggered smart drug delivery system encapsulating idarubicin shows superior kinetics and enhances tumoral drug uptake and response.

Rationale: Increasing the bioavailable drug level in a tumor is the key to enhance efficacy of chemotherapy. Thermosensitive smart drug delivery systems (SDDS) in combination with local hyperthermia facilitate high local drug levels, thus improving uptake in the tumor. However, inability to rapidly and efficiently absorb the locally released drug results in reduced efficacy, as well as undesired redistribution of the drug away from the tumor to the system. Methods: Based on this paradigm we propose a novel approach in which we replaced doxorubicin (DXR), one of the classic drugs for nanocarrier-based delivery, with idarubicin (IDA), a hydrophobic anthracycline used solely in the free form for treatment hematologic cancers. We established a series of in vitro and in vivo experiments to in depth study the kinetics of SDDS-based delivery, drug release, intratumor biodistribution and subsequent cell uptake. Results: We demonstrate that IDA is taken up over 10 times more rapidly by cancer cells than DXR in vitro. Similar trend is observed in in vivo online imaging and less drug redistribution is shown for IDA, together resulting in 4-times higher whole tumor drug uptake for IDA vs. DXR. Together his yielded an improved intratumoral drug distribution for IDA-SDDS, translating into superior tumor response compared to DXR-SDDS treatment at the same dose. Thus, IDA - a drug that is not used for treatment of solid cancers - shows superior therapeutic index and better outcome when administered in externally triggered SDDS. Conclusions: We show that a shift in selection of chemotherapeutics is urgently needed, away from the classic drugs towards selection based on properties of a chemotherapeutic in context of the nanoparticle and delivery mode, to maximize the therapeutic efficacy.

Investigation of Particle Accumulation, Chemosensitivity and Thermosensitivity for Effective Solid Tumor Therapy Using Thermosensitive Liposomes and Hyperthermia.

Doxorubicin (Dox) loaded thermosensitive liposomes (TSLs) have shown promising results for hyperthermia-induced local drug delivery to solid tumors. Typically, the tumor is heated to hyperthermic temperatures (41-42 °C), which induced intravascular drug release from TSLs within the tumor tissue leading to high local drug concentrations (1-step delivery protocol). Next to providing a trigger for drug release, hyperthermia (HT) has been shown to be cytotoxic to tumor tissue, to enhance chemosensitivity and to increase particle extravasation from the vasculature into the tumor interstitial space. The latter can be exploited for a 2-step delivery protocol, where HT is applied prior to i.v. TSL injection to enhance tumor uptake, and after 4 hours waiting time for a second time to induce drug release. In this study, we compare the 1- and 2-step delivery protocols and investigate which factors are of importance for a therapeutic response. In murine B16 melanoma and BFS-1 sarcoma cell lines, HT induced an enhanced Dox uptake in 2D and 3D models, resulting in enhanced chemosensitivity. In vivo, therapeutic efficacy studies were performed for both tumor models, showing a therapeutic response for only the 1-step delivery protocol. SPECT/CT imaging allowed quantification of the liposomal accumulation in both tumor models at physiological temperatures and after a HT treatment. A simple two compartment model was used to derive respective rates for liposomal uptake, washout and retention, showing that the B16 model has a twofold higher liposomal uptake compared to the BFS-1 tumor. HT increases uptake and retention of liposomes in both tumors models by the same factor of 1.66 maintaining the absolute differences between the two models. Histology showed that HT induced apoptosis, blood vessel integrity and interstitial structures are important factors for TSL accumulation in the investigated tumor types. However, modeling data indicated that the intraliposomal Dox fraction did not reach therapeutic relevant concentrations in the tumor tissue in a 2-step delivery protocol due to the leaking of the drug from its liposomal carrier providing an explanation for the observed lack of efficacy.

EGFR targeted thermosensitive liposomes: A novel multifunctional platform for simultaneous tumor targeted and stimulus responsive drug delivery.

The epidermal growth factor receptor (EGFR) is a promising target for anti-cancer therapy. The aim of this study was to design thermosensitive liposomes (TSL), functionalized with anti-EGFR ligands for targeted delivery and localized triggered release of chemotherapy. For targeting, EGFR specific peptide (GE11) and Fab' fragments of cetuximab were used and the effect of ligand density on in vitro tumor targeting was investigated. Ligand conjugation did not significantly change the physicochemical characteristics of liposomes. Fab'-decorated TSL (Fab'-TSL) can specifically and more efficiently bind to the EGFR overexpressed cancer cells as compared to GE11 modified TSL. Calcein labeled Fab'-TSL showed adequate stability at 37°C in serum (<4% calcein released after 1h) and a temperature dependent release at above 40°C. FACS analysis and live cell imaging showed efficient and EGFR mediated cellular association as well as dramatic intracellular cargo release upon hyperthermia. Fab'-conjugation and hyperthermia induced enhanced tumor cell cytotoxicity of doxorubicin loaded TSL. The relative cytotoxicity of Fab'-TSL was also correlated to EGFR density on the tumor cells. These results suggest that Fab'-TSL showed great potential for combinational targeted and triggered release drug delivery.

Light Fractionation Significantly Increases the Efficacy of Photodynamic Therapy Using BF-200 ALA in Normal Mouse Skin.

BACKGROUND: Light fractionation significantly increases the efficacy of 5-aminolevulinic acid (ALA) based photodynamic therapy (PDT) using the nano-emulsion based gel formulation BF-200. PDT using BF-200 ALA has recently been clinically approved and is under investigation in several phase III trials for the treatment of actinic keratosis. This study is the first to compare BF-200 ALA with ALA in preclinical models. RESULTS: In hairless mouse skin there is no difference in the temporal and spatial distribution of protoporphyrin IX determined by superficial imaging and fluorescence microscopy in frozen sections. In the skin-fold chamber model, BF-200 ALA leads to more PpIX fluorescence at depth in the skin compared to ALA suggesting an enhanced penetration of BF-200 ALA. Light fractionated PDT after BF-200 ALA application results in significantly more visual skin damage following PDT compared to a single illumination. Both ALA formulations show the same visual skin damage, rate of photobleaching and change in vascular volume immediately after PDT. Fluorescence immunohistochemical imaging shows loss of VE-cadherin in the vasculature at day 1 post PDT which is greater after BF-200 ALA compared to ALA and more profound after light fractionation compared to a single illumination. DISCUSSION: The present study illustrates the clinical potential of light fractionated PDT using BF-200 ALA for enhancing PDT efficacy in (pre-) malignant skin conditions such as basal cell carcinoma and vulval intraepithelial neoplasia and its application in other lesion such as cervical intraepithelial neoplasia and oral squamous cell carcinoma where current approaches have limited efficacy.

Method of hyperthermia and tumor size influence effectiveness of doxorubicin release from thermosensitive liposomes in experimental tumors.

Systemic chemotherapy of solid tumors could be enhanced by local hyperthermia (HT) in combination with thermosensitive liposomes (TSL) as drug carriers. In such an approach, effective HT of the tumor is considered essential for successful triggering local drug release and targeting of the drug to the tumor. To investigate the effect of HT method on the effectiveness of drug delivery, a novel laser-based HT device designed for the use in magnetic resonance imaging (MRI) was compared systematically with the frequently used cold light lamp and water bath HT. Long circulating phosphatidyldiglycerol-based TSL (DPPG2-TSL) with encapsulated doxorubicin (DOX) were used as drug carrier enabling intravascular drug release. Experiments were performed in male Brown Norway rats with a syngeneic soft tissue sarcoma (BN 175) located on both hind legs. One tumor was heated while the second tumor remained unheated as a reference. Six animals were investigated per HT method. DPPG2-TSL were injected i.v. at a stable tumor temperature above 40°C. Thereafter, temperature was maintained for 60min. Total DOX concentration in plasma, tumor tissue and muscle was determined post therapy by HPLC. Finally, the new laser-based device was tested in a MRI environment at 3T using DPPG2-TSL with encapsulated Gd-based contrast agent. All methods showed effective DOX delivery by TSL with 4.5-23.1ng/mg found in the heated tumors. In contrast, DOX concentration in the non-heated tumors was 0.5±0.1ng/mg. Independent of used HT methods, higher DOX levels were found in the smaller tumors. In comparison water bath induced lowest DOX delivery but still showing fourfold higher DOX concentrations compared to the non-heated tumors. With the laser-based applicator, a 13 fold higher DOX deposition was possible for large tumors and a 15 fold higher for the small tumors, respectively. Temperature gradients in the tumor tissue were higher with the laser and cold light lamp (-0.3°C/mm to -0.5°C/mm) compared to the water bath (-0.1°C/mm and -0.2°C/mm). Visualization of HT in the MRI demonstrated successful localized heating throughout the entire tumor volume by contrast agent release from DPPG2-TSL. In conclusion, HT triggered drug delivery by using DPPG2-TSL is a promising tool in chemotherapy but effectiveness markedly depended on the method of heating and also on tumor size. Local HT using a cold light lamp or the new laser applicator allowed more efficient drug delivery than using a regional water bath heating. MR-compatibility of the new applicator gives the opportunity for future experiments investing drug delivery in more detail by MRI at low technical efforts.

Formulation and optimization of idarubicin thermosensitive liposomes provides ultrafast triggered release at mild hyperthermia and improves tumor response.

Drug delivery through thermosensitive liposomes (TSL) in combination with hyperthermia (HT) has shown great potential. HT can be applied locally forcing TSL to release their content in the heated tumor resulting in high peak concentrations. To perform optimally the drug is ideally released fast (seconds) and taken up rapidly by tumor cells. The aim of this study was to develop a novel thermosensitive liposome formulation of the anthracycline idarubicin (IDA-TSL). The hydrophobicity of idarubicin may improve its release from liposomes and subsequently rapid cellular uptake when combined mild hyperthermia. Here, we investigated a series of parameters to optimize IDA-TSL formulation. The results show that the optimal formulation for IDA-TSL is DPPC/DSPC/DSPE-PEG (6/3.5/0.5 mol%), with ammonium EDTA of 6.5 pH as loading buffer and a size of ~85 nm. In vitro studies demonstrated minimal leakage of ~20% in FCS at 37 °C for 1h, while an ultrafast and complete triggered release of IDA was observed at 42 °C. On tumor cells IDA-TSL showed comparable cytotoxicity to free IDA at 42 °C, but low cytotoxicity at 37 °C. Intravital microscopy imaging demonstrated an efficient in vivo intravascular triggered drug release of IDA-TSL under mild hyperthermia, and a subsequent massive IDA uptake by tumor cells. In animal efficacy studies, IDA-TSL plus mild HT demonstrated prominent tumor growth inhibition and superior survival rate over free IDA with HT or a clinically used Doxil treatment. These results suggest beneficial potential of IDA-TSL combined with local mild HT.

A novel two-step mild hyperthermia for advanced liposomal chemotherapy.

Liposomal chemotherapy brings the advantage of minimizing systemic toxicity towards healthy organs and tissues, while has the drawbacks of limited nanoparticle accumulation and low drug bioavailability at targeted tumors. The aim of our study is to apply a clinically available mild hyperthermia (HT) treatment with thermosensitive liposomes (TSL) to tackle both issues. A two-step HT approach was combined with systemic administration of doxorubicin (Dox) TSL, in a first step to maximize nanoparticle accumulation in tumors and second step to actively trigger Dox release. The therapeutic activity of the two-step approach was compared to a one-step HT triggering intravascular Dox release from circulating TSL. Whereas the intravascular drug release approach requires fast releasing Dox-TSL (Dox-fTSL), the TSL formulation used in the two-step approach is fine-tuned to prolong Dox retention at physiological temperature in circulation, while releasing their drug content at mild HT at a slower rate (Dox-sTSL). Cytotoxicity assays show that a first-step HT at 41°C for 1h causes no drug resistance on murine BFS-1 sarcoma, human BLM melanoma cell lines and Human Umbilical Vein Endothelial Cells (HUVEC) towards subsequent exposure to Dox. However, HT sensitizes HUVEC towards Dox at higher concentrations (10-100µM). After 2h of intratumoral Dox-TSL accumulation, HT at 42°C for 1h was applied to trigger Dox release from Dox-sTSL. Quantification of intratumoral Dox accumulation revealed that the two-step HT approach increased TSL accumulation and Dox bioavailability reaching levels comparable to the intravascular release approach. The two-step HT in combination with Dox-sTSL delayed tumor growth for 12days compared to PBS group, however, was less effective compared to intravascular Dox release from Dox-fTSL using one-step HT. The two-step approach focuses on interstitial drug release upon mild HT, instead of intravascular drug release. This novel two-step approach represents an attractive alternative for the treatment of large and deep seated tumors, which are difficult to heat precisely and require loco-regional HT of the tumor area and accumulated Dox-sTSL therein to obtain a precise intratumoral drug delivery.

Mild hyperthermia triggered doxorubicin release from optimized stealth thermosensitive liposomes improves intratumoral drug delivery and efficacy.

Liposome mediated anticancer drug delivery has the advantage of reducing cytotoxicity in healthy tissues. However, undesired slow drug release impedes the therapeutic efficacy of clinically applied PEG-liposomal doxorubicin (Dox). The aim of this study is to combine stealth thermosensitive liposomes (TSL) and local mild hyperthermia (HT) to increase bioavailable Dox levels in tumors. Dox was encapsulated in stealth TSL (~80nm) with optimized PEG concentration in the membrane, and compared with lysolipid-based Dox-LTSL for in vitro stability, release kinetics, and in vivo tumor growth control. In vitro cytotoxicity of Dox-TSL against murine BFS-1 sarcoma and, human BLM melanoma cell lines and Human Umbilical Vein Endothelial Cells (HUVEC) under normothermia (37°C) and HT (42°C) was compared with non-encapsulated Dox. In vitro Dox uptake in nuclei was imaged in BLM and HUVEC. In vivo intravascular Dox release from TSL in BFS-1 tumors under local mild HT in dorsal skin flap window chamber models was captured by intravital confocal microscopy. Intravascular Dox-TSL release kinetics, penetration depth and interstitial Dox density were subjected to quantitative image analysis. Systemic Dox-TSL administration in combination with local mild HT on subcutaneous tumor growth control was compared to Dox-LTSL plus local mild HT. Dox-TSL was stable at 37°C, while released over 95% Dox within 1min in 90% serum at 42°C. Dox-TSL demonstrated efficient in vivo intratumoral Dox release under local mild HT, followed by significant Dox uptake by tumor and tumor vascular endothelial cells. Dox-TSL plus mild HT showed improved tumor growth control over Dox-LTSL plus mild HT. Survival after a single treatment of Dox-TSL plus mild HT was 67%, while survival after Dox-LTSL plus mild HT was 22%. This combination of Dox-TSL and local mild HT offers promising clinical opportunities to improve liposomal Dox delivery to solid tumors.

Improved intratumoral nanoparticle extravasation and penetration by mild hyperthermia.

Accumulation of nanoparticles in solid tumors depends on their extravasation. However, vascular permeability is very heterogeneous within a tumor and among different tumor types, hampering efficient delivery. Local hyperthermia at a tumor can improve nanoparticle delivery by increasing tumor vasculature permeability, perfusion and interstitial fluid flow. The aim of this study is to investigate hyperthermia conditions required to improve tumor vasculature permeability, subsequent liposome extravasation and interstitial penetration in 4 tumor models. Tumors are implanted in dorsal skin flap window chambers and observed for liposome (~85 nm) accumulation by intravital confocal microscopy. Local hyperthermia at 41°C for 30 min initiates liposome extravasation through permeable tumor vasculature in all 4 tumor models. A further increase in nanoparticle extravasation occurs while continuing heating to 1h, which is a clinically relevant duration. After hyperthermia, the tumor vasculature remains permeable for 8h. We visualize gaps in the endothelial lining of up to 10 µm induced by HT. Liposomes extravasate through these gaps and penetrate into the interstitial space to at least 27.5 µm in radius from the vessel walls. Whole body optical imaging confirms HT induced extravasation while liposome extravasation was absent at normothermia. In conclusion, a thermal dose of 41°C for 1h is effective to induce long-lasting permeable tumor vasculature for liposome extravasation and interstitial penetration. These findings hold promise for improved intratumoral drug delivery upon application of local mild hyperthermia prior to administration of nanoparticle-based drug delivery systems.

Development of a liposomal delivery system for temperature-triggered release of a tumor targeting agent, Ln(III)-DOTA-phenylboronate.

Liposomes, capable of temperature-triggered content release at the site of interest, can be of great importance for imaging and therapy of tumors. The delivery of imaging agents or therapeutics can be improved by application of liposomes with a gel-to-liquid phase-transition temperature suitable for mild hyperthermia (41-43°C), and by prolonging their circulation time by incorporation of lipids containing polyethyleneglycol moieties. Still, the rapid wash out of the delivered material from the tumor tissue is a major obstacle for both imaging and therapy. In this study, we developed an optimized temperature sensitive liposomal system to be used with mild hyperthermia: highly stable at physiological temperature and with a sharp transition of the bilayer at 41.5°C, with subsequent rapid release of entrapped compounds such as calcein or tumor cell-targeting contrast agents. Intravital microscopy on calcein/rhodamine containing liposomes was applied to demonstrate the applicability of this system in vivo. The calcein loaded liposomes were injected iv into nude mice with a human BLM melanoma tumor implanted in a dorsal skin-fold window chamber. Arrival of the liposomes at the tumor site and content release after temperature increase were monitored. The results demonstrated not only accumulation of the liposomes at the tumor site, but also a massive release of calcein after increase of the temperature to 41°C. The versatility of the thermosensitive liposomes was further demonstrated by encapsulation of a tumor cell-targeting DOTA-phenylboronate conjugate and its release at elevated temperatures. The DOTA ligand in this system is able to chelate a variety of metals suitable for both diagnostic and therapeutic applications, whereas the phenylboronate function is able to target specifically to tumor cells through a covalent binding with sialic acid moieties over-expressed on their surface upon heat-triggered release from the liposomal carrier.

Triggered content release from optimized stealth thermosensitive liposomes using mild hyperthermia.

Liposomes are potent nanocarriers to deliver chemotherapeutic drugs to tumors. However, the inefficient drug release hinders their application. Thermosensitive liposomes (TSL) can release drugs upon heat. This study aims to identify the optimum 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG(2000) (DSPE-PEG(2000)) concentration in stealth TSL to improve content release efficiency under mild hyperthermia (HT). TSL were prepared with DSPE-PEG(2000) from 1 to 10 mol%, around 80 nm in size. Quenched carboxyfluorescein (CF) in aqueous phase represented encapsulated drugs. In vitro temperature/time-dependent CF release and TSL stability in serum were quantified by fluorometry. In vivo CF release in dorsal skin flap window chamber models implanted with human BLM melanoma was captured by confocal microscopy. In vitro heat triggered CF release increased with increasing DSPE-PEG(2000) density. However, 6 mol% and higher DSPE-PEG(2000) caused CF leakage at physiological temperature. TSL with 5 mol% DSPE-PEG(2000) were stable at 37 degrees C, while released 60% CF in 1 min and almost 100% CF in 1h at 42 degrees C. In vivo optical intravital imaging showed immediate massive CF release above 41 degrees C. In conclusion, incorporation of 5 mol% DSPE-PEG(2000) optimized stealth TSL content release triggered by HT.

Histamine combined with melphalan in isolated limb perfusion for the treatment of locally advanced soft tissue sarcomas: preclinical studies in rats

OBJETIVO: Avaliar o potencial benéfico da histamina combinada ao melfalano, na perfusão de membro isolado (PMI), como alternativa à combinacão TNF-alfa mais melfalano, no tratamento de sarcomas de partes moles irressecaveis em extremidades, em ratos de linhagem Brown Norway (BN). MÉTODOS: 20 ratos BN foram submetidos a implantacão de fragmentos de fibrosarcoma singênico BN-175 na pata traseira direita. Em cerca de 7-10 dias o tumor atingiu um diâmetro médio de 12-15 mm e foram aleatóriamente divididos em quatro grupos (controle, melfalano,histamina em doses progessivas combinada ao melfalano e histamina) sendo submetidos a PMI experimental por 30 minutos. Os tumores foram então medidos diariamente com o uso de paquímetro e o volume tumoral calculado. RESULTADOS: As curvas de resposta mostram um efeito significativo da combinacão de Histamina na concentracão de 200 mg/mL ao melfalano, com 66% de resposta global incluindo 33% de respostas completas (p < 0.01). Não houve efeitos colaterais sistêmicos e localmente apenas edema leve e transitório nos animais tratados com histamine. CONCLUSAO: A histamina em combinacão com o melfalano apresenta um efeito promissor na PMI garantindo maiores investigacões do seu mecanismo de acão e do seu potencial uso na perfusão de órgãos.