Actively targeting solid tumours with thermoresponsive drug delivery systems that respond to mild hyperthermia

Different Applications of Temperature responsive nanogels as a new drug delivery system mini review

Temperature-sensitive drug delivery systems (TSDDS) are one of the systems that have received more attention in medical science these days due to their advantages. As these systems are sensitive to temperature, drug delivery to the target becomes more specific. Temperature-sensitive nanogels have many applications, including microbial infections, cancer therapy, transdermal use and tissue repair. These systems are characterized by minimal toxicity, improved therapeutic efficacy and reduced exposure to normal cells. This mini-review is prepared with different types of temperature-sensitive nanogel formation, release mechanisms, and their different applications. Various systems reported under these categories for targeted and controlled delivery of different classes of drugs, such as anti-cancer and antibiotic drugs with special emphasis on anti-cancer drugs and tissue healing, are discussed in this mini-review.

Validation of Potential Protein Markers Predicting Chemoradioresistance in Early Cervical Cancer by Immunohistochemistry

Background

In a previous study, a proteomic panel consisting of BCL-2, HER2, CD133, CAIX, and ERCC1 significantly predicted survival in patients with locally advanced cervical cancer. However, the prognostic significance of these proteins has not been assessed in early cervical cancer. The present study investigated the clinical significance and chemoradioresistance prediction power of these proteins in patients with early-stage cervical cancer.

Materials and Methods

BCL-2, HER2, CD133, CAIX, and ERCC1 expression was determined by the immunohistochemical staining of 336 cervical cancer tissue microarrays. The associations of these proteins with clinicopathologic characteristics and disease progression were assessed.

Results

There was a trend of low CAIX expression (p=0.082) and high ERCC1 expression (p=0.059) in patients with a favorable response to adjuvant radiation. High HER2 expression was significantly associated with shorter disease-free survival (DFS) in the total group (5-year DFS of 80.1% vs. 92.2%, p=0.004). A prognostic significance remained in multivariate analysis (Hazard ratio, HR=2.10, p=0.029). In the adjuvant radiation group, low CAIX and high ERCC1 expression indicated significantly unfavorable DFS (75.0% vs. 89.0%, p=0.026 and 76.8% vs. 88.6%, p=0.022, respectively). Low CAIX expression remained an independent prognostic marker in multivariate analysis (HR=0.45, p=0.037). The combined molecular-clinical model using random survival forest method predicted DFS with improved power compared with that of the clinical variable model (C-index 0.77 vs. 0.71, p=0.006).

Conclusion

HER2, CAIX, and ERCC1 expression can be predictive protein markers for clinical outcomes in early cervical cancer patients treated primarily with radical surgery with or without adjuvant radiation.

Direct treatment versus indirect: Thermo-ablative and mild hyperthermia effects

Hyperthermia is a rapidly growing field in cancer therapy and many advances have been made in understanding and applying the mechanisms of hyperthermia. Secondary effects of hyperthermia have been increasingly recognized as important in therapeutic effects and multiple studies have started to elucidate their implications for treatment. Immune effects have especially been recognized as important in the efficacy of hyperthermia treatment of cancer. Both thermo-ablative and mild hyperthermia activate the immune system, but mild hyperthermia seems to be more effective at doing so. This may suggest that mild hyperthermia has some advantages over thermo-ablative hyperthermia and research into immune effects of mild hyperthermia should continue. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

An MRI-guided HIFU-triggered wax-coated capsule for supertargeted drug release: a proof-of-concept study

BACKGROUND

Externally controlling and monitoring drug release at a desired time and location is currently lacking in the gastrointestinal tract. The aim of the study was to develop a thermoresponsive wax-coated capsule and to trigger its release upon applying a magnetic resonance imaging (MRI)-guided high-intensity focused ultrasound (HIFU) pulse.

METHODS

Capsules containing a lyophilised gadolinium-based contrast agent (GBCA) were coated with a 1:1 (mass/mass) mixture of lanolin and cetyl alcohol (melting point ≈43 °C) and exposed to simulated gastric and intestinal fluids (United States Pharmacopoeia) at 37 °C for 2 and 24 h, respectively. In a HIFU gel phantom, wax-coated capsules (n = 3) were tracked based on their T1- and T2-hypointensity by 1.5-T T1- and T2-weighted MRI pre- and post-exposure to an MRI-guided HIFU pulse.

RESULTS

Lanolin/cetyl alcohol-coated capsules showed high resistance to simulated gastrointestinal fluids. In a gel phantom, an MRI-guided HIFU pulse punctured the wax coating, resulting in the hydration and release of the encapsulated lyophilised GBCA and yielding a T1-hyperintense signal close to the wax-coated capsule.

CONCLUSION

We provide the proof-of-concept of applying a non-invasive MRI-guided HIFU pulse to actively induce the disintegration of the wax-coated capsule, and a method to monitor the release of the cargo via T1-weighted MRI based on the hydration of an encapsulated lyophilised GBCA. The wax-coated capsule platform enables temporally and spatially supertargeted drug release via the oral route and promises to address a currently unmet clinical need for personalised local therapy in gastrointestinal diseases such as inflammatory bowel diseases and cancer.

High peak and high average radiofrequency power transmit/receive switch for thermal magnetic resonance

PURPOSE

To study the role of temperature in biological systems, diagnostic contrasts and thermal therapies, RF pulses for MR spin excitation can be deliberately used to apply a thermal stimulus. This application requires dedicated transmit/receive (Tx/Rx) switches that support high peak powers for MRI and high average powers for RF heating. To meet this goal, we propose a high-performance Tx/Rx switch based on positive-intrinsic-negative diodes and quarter-wavelength (λ/4) stubs.

METHODS

The λ/4 stubs in the proposed Tx/Rx switch design route the transmitted RF signal directly to the RF coil/antenna without passing through any electronic components (e.g., positive-intrinsic-negative diodes). Bench measurements, MRI, MR thermometry, and RF heating experiments were performed at f = 297 MHz (B₀  = 7 T) to examine the characteristics and applicability of the switch.

RESULTS

The proposed design provided an isolation of -35.7dB/-41.5dB during transmission/reception. The insertion loss was -0.41dB/-0.27dB during transmission/reception. The switch supports high peak (3.9 kW) and high average (120 W) RF powers for MRI and RF heating at f = 297 MHz. High-resolution MRI of the wrist yielded image quality competitive with that obtained with a conventional Tx/Rx switch. Radiofrequency heating in phantom monitored by MR thermometry demonstrated the switch applicability for thermal modulation. Upon these findings, thermally activated release of a model drug attached to thermoresponsive polymers was demonstrated.

CONCLUSION

The high-power Tx/Rx switch enables thermal MR applications at 7 T, contributing to the study of the role of temperature in biological systems and diseases. All design files of the switch will be made available open source at www.opensourceimaging.org.

Transport of drugs from blood vessels to tumour tissue

The effectiveness of anticancer drugs in treating a solid tumour is dependent on delivery of the drug to virtually all cancer cells in the tumour. The distribution of drug in tumour tissue depends on the plasma pharmacokinetics, the structure and function of the tumour vasculature and the transport properties of the drug as it moves through microvessel walls and in the extravascular tissue. The aim of this Review is to provide a broad, balanced perspective on the current understanding of drug transport to tumour cells and on the progress in developing methods to enhance drug delivery. First, the fundamental processes of solute transport in blood and tissue by convection and diffusion are reviewed, including the dependence of penetration distance from vessels into tissue on solute binding or uptake in tissue. The effects of the abnormal characteristics of tumour vasculature and extravascular tissue on these transport properties are then discussed. Finally, methods for overcoming limitations in drug transport and thereby achieving improved therapeutic results are surveyed.

Elastin-like polypeptides: the power of design for smart cell encapsulation

INTRODUCTION

Cell encapsulation technology is still a challenging issue. Innovative methodologies such as additive manufacturing, and alternative bioprocesses, such as cell therapeutic delivery, where cell encapsulation is a key tool are rapidly gaining importance for their potential in regenerative medicine. Responsive materials such as elastin-based recombinant expression products have features that are particularly attractive for cell encapsulation. They can be designed and tailored to meet desired requirements. Thus, they represent promising candidates for the development of new concept-based materials that can be employed in this field. Areas covered: An overview of the design and employment of elastin-like polypeptides for cell encapsulation is given to outline the state of the art. Special attention is paid to the design of the macromolecule employed as well as to the method of matrix formation and the biological system involved. Expert opinion: As a result of recent progress in regenerative medicine there is a compelling need for materials that provide specific properties and demonstrate defined functional features. Rationally designed materials that may adapt according to applied external stimuli and that are responsive to biological systems, such as elastin-like polypeptides, belong to this class of smart material. A run through the components described to date represents a good starting point for further advancement in this area. Employment of these components in cell encapsulation application will promote its advance toward 'smart cell encapsulation technology'.

DCE-MRI and IVIM-MRI of rabbit Vx2 tumors treated with MR-HIFU-induced mild hyperthermia

Background

The purpose of this study is to investigate whether changes could be detected in dynamic contrast-enhanced (DCE) and intra-voxel incoherent motion (IVIM) MR parameters upon MR-guided high-intensity focused ultrasound (MR-HIFU)-induced hyperthermia in a rabbit Vx2 tumor model.

Methods

Five Vx2 tumor-bearing New Zealand white rabbits were treated with hyperthermia using a clinical MR-HIFU system. Data were acquired before and after hyperthermia. For the DCE analysis, the extended Tofts model was used. For the IVIM analysis, a Bayesian approach was used. Maps were reconstructed of the DCE parameters (K^trans, k_ep, and v_p) and IVIM parameters (D_t, f_p, and D_p). Individual parameter histograms and two-dimensional cross-correlation histograms were constructed to analyze changes in the parameters after hyperthermia. Changes in median values were tested for statistical significance with the Mann-Whitney U test.

Results

The MR temperature measurements confirmed that mild hyperthermia (40 to 42 °C) was successfully achieved in all rabbits. One rabbit died during treatment and was excluded from the analysis. In the remaining four rabbits, an increase in D_t was observed. In three rabbits, an increase in K^trans was observed, while in the other rabbits, all three DCE parameter values decreased. Mixed changes were seen for v_p and f_p.

Conclusions

Changes in DCE and IVIM parameters were detected after hyperthermia and were variable between the rabbits. DCE- and IVIM-MRI may be promising tools to assess tumor responses to hyperthermia. Further research in a larger number of subjects is necessary in order to assess their value for treatment response monitoring.

Imaging the intratumoral-peritumoral extracellular pH gradient of gliomas

Solid tumors have an acidic extracellular pH (pHe ) but near neutral intracellular pH (pHi ). Because acidic pHe milieu is conducive to tumor growth and builds resistance to therapy, simultaneous mapping of pHe inside and outside the tumor (i.e., intratumoral-peritumoral pHe gradient) fulfills an important need in cancer imaging. We used Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), which utilizes shifts of non-exchangeable protons from macrocyclic chelates (e.g., 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) or DOTP(8-) ) complexed with paramagnetic thulium (Tm(3) (+) ) ion, to generate in vivo pHe maps in rat brains bearing 9L and RG2 tumors. Upon TmDOTP(5-) infusion, MRI identified the tumor boundary by enhanced water transverse relaxation and BIRDS allowed imaging of intratumoral-peritumoral pHe gradients. The pHe measured by BIRDS was compared with pHi measured with (31) P-MRS. In normal tissue, pHe was similar to pHi , but inside the tumor pHe was lower than pHi . While the intratumoral pHe was acidic for both tumor types, peritumoral pHe varied with tumor type. The intratumoral-peritumoral pHe gradient was much larger for 9L than RG2 tumors because in RG2 tumors acidic pHe was found in distal peritumoral regions. The increased presence of Ki-67 positive cells beyond the RG2 tumor border suggested that RG2 was more invasive than the 9L tumor. These results indicate that extensive acidic pHe beyond the tumor boundary correlates with tumor cell invasion. In summary, BIRDS has sensitivity to map the in vivo intratumoral-peritumoral pHe gradient, thereby creating preclinical applications in monitoring cancer therapeutic responses (e.g., with pHe -altering drugs). Copyright © 2016 John Wiley & Sons, Ltd.

Fabrication of thermo-sensitive complex micelles for reversible cell targeting

To ideally solve the contradiction between enhanced cellular uptake and prolonged blood circulation, reversible targeting polymeric micelles based on the expanding and shrinking behavior of a temperature-responsive polymer were developed. The micelle contained a hydrophobic PCL core and a mixed shell consisting of poly(N-isopropylacrylamide) (PNIPAAm) and biotin-terminated poly(ethylene glycol) (Biotin-PEG), and its targeting ability could be switched on/off by temperature. The cellular uptake of the complex polymeric micelles was studied. The results from a quantitative enzyme-linked immunosorbent assay (ELISA) indicated that the surface biotin content increased by as much as 11.6-fold when the temperature increased above the lower critical solution temperature (LCST). More importantly, the ELISA confirmed that biotin-mediated targeting on the surface was reversibly switched on and off for at least five cycles. In addition, the results from quantitative flow cytometry and confocal spectroscopy indicated that the cellular uptake of the targeted micelles at temperatures above the LCST was much higher than that at temperatures below the LCST. This complex polymeric micelle with reversible targeting property could be a promising alternative for drug delivery.

Effects of Doxorubicin Delivery Systems and Mild Hyperthermia on Tissue Penetration in 3D Cell Culture Models of Ovarian Cancer Residual Disease

Current chemotherapy strategies for second-line treatment of relapsed ovarian cancer are unable to effectively treat residual disease post-cytoreduction. The findings presented herein suggest that tissue penetration of drug is not only an issue for large, unresectable tumors, but also for invisible, microscopic lesions. The present study sought to investigate the potential of a block copolymer micelle (BCM) formulation, which may reduce toxicities of doxorubicin (DOX) in a similar way to pegylated liposomal doxorubicin (PLD, Doxil/Caelyx), while enhancing penetration into tumor tissue and improving intratumoral availability of drug. To achieve this goal, 50 nm-sized BCMs capable of high DOX encapsulation (BCM-DOX) at drug levels ranging from 2 to 7.6 mg/mL were formulated using an ultrafiltration technique. BCM-DOX was evaluated in 2D and 3D cell culture of the human ovarian cancer cell lines HEYA8, OV-90, and SKOV3. Additionally, the current study examines the impact of mild hyperthermia (MHT) on the cytotoxicity of DOX. The BCM-DOX formulation fulfilled the goal of controlling drug release while providing up to 9-fold greater cell monolayer cytotoxicity in comparison to PLD. In 3D cell culture, using multicellular tumor spheroids (MCTS) as a model of residual disease postsurgery, BCM-DOX achieved the benefits of an extended release formulation of DOX and resulted in improvements in drug accumulation over PLD, while yielding drug levels approaching that achievable by exposure to DOX alone. In comparison to PLD, this translated into superior MCTS growth inhibition in the short term and comparable inhibition in the long term. Overall, although MHT appeared to enhance drug accumulation in HEYA8 MCTS treated with BCM-DOX and DOX alone in the short term, improved growth inhibition of MCTS by MHT was not observed after 48 h of drug treatment. Evaluation of BCM-DOX in comparison to PLD as well as the effects of MHT is warranted in vivo.

Recent advances of thermally responsive nanogels for cancer therapy

Thermally responsive nanogel drug delivery systems (TRNDDS) have been widely investigated as a new strategy for active targeting tumor therapy, as these can accumulate on the tumor site and/or release the payload at the desired site by structure changes rapidly once stimulated by temperature changes. In this review, we discuss the evolution of TRNDDS and future perspectives for antitumor drug and gene delivery. With further understanding of the specificity of tumor site at the cellular and molecular level, in parallel with the development of nanomaterial design and preparation, TRNDDS show great potential for tumor targeting therapy.

Temperature matters! And why it should matter to tumor immunologists

A major goal of cancer immunology is to stimulate the generation of long-lasting, tumor antigen-specific immune responses that recognize and destroy tumor cells. This article discusses advances in thermal medicine with the potential to improve cancer immunotherapy. Accumulating evidence indicates that survival benefits are accorded to individuals who achieve an increase in body temperature (i.e. fever) following infection. Furthermore, accumulating evidence indicates that physiological responses to hyperthermia impact the tumor microenvironment through temperature-sensitive check-points that regulate tumor vascular perfusion, lymphocyte trafficking, inflammatory cytokine expression, tumor metabolism, and innate and adaptive immune function. Nevertheless, the influence of thermal stimuli on the immune system, particularly the antitum or immune response, remains incompletely understood. In fact, temperature is still rarely considered as a critical variable in experimental immunology. We suggest that more attention should be directed to the role of temperature in the regulation of the immune response and that thermal therapy should be tested in conjunction with immunotherapy as a multi-functional adjuvant that modulates the dynamics of the tumor microenvironment.

Sonosensitive theranostic liposomes for preclinical in vivo MRI-guided visualization of doxorubicin release stimulated by pulsed low intensity non-focused ultrasound

The main goal of this study was to assess the theranostic performance of a nanomedicine able to generate MRI contrast as a response to the release from liposomes of the antitumor drug Doxorubicin triggered by the local exposure to pulsed low intensity non focused ultrasounds (pLINFU). In vitro experiments showed that Gadoteridol was an excellent imaging agent for probing the release of Doxorubicin following pLINFU stimulation. On this basis, the theranostic system was investigated in vivo on a syngeneic murine model of TS/A breast cancer. MRI offered an excellent guidance for monitoring the pLINFU-stimulated release of the drug. Moreover, it provided: i) an in vivo proof of the effective release of the liposomal content, and ii) a confirmation of the therapeutic benefits of the overall protocol. Ex vivo fluorescence microscopy indicated that the good therapeutic outcome was originated from a better diffusion of the drug in the tumor following the pLINFU stimulus. Very interestingly, the broad diffusion of the drug in the tumor stroma appeared to be mediated by the presence of the liposomes themselves. The results of this study highlighted either the great potential of US-based stimuli to safely trigger the release of a drug from its nanocarrier or the associated significant therapeutic improvement. Finally, MRI demonstrated to be a valuable technique to support chemotherapy and monitoring the outcome. Furthermore, in this specific case, the theranostic agent developed has a high clinical translatability because the MRI agent utilized is already approved for human use.

Magnetic nanoparticle-based therapeutic agents for thermo-chemotherapy treatment of cancer

Magnetic nanoparticles have been widely investigated for their great potential as mediators of heat for localised hyperthermia therapy. Nanocarriers have also attracted increasing attention due to the possibility of delivering drugs at specific locations, therefore limiting systematic effects. The enhancement of the anti-cancer effect of chemotherapy with application of concurrent hyperthermia was noticed more than thirty years ago. However, combining magnetic nanoparticles with molecules of drugs in the same nanoformulation has only recently emerged as a promising tool for the application of hyperthermia with combined chemotherapy in the treatment of cancer. The main feature of this review is to present the recent advances in the development of multifunctional therapeutic nanosystems incorporating both magnetic nanoparticles and drugs, and their superior efficacy in treating cancer compared to either hyperthermia or chemotherapy as standalone therapies. The principle of magnetic fluid hyperthermia is also presented.

Review: the role of hyperthermia in treating pancreatic tumors

There is only marginal improvement in outcome of treating pancreatic cancer in the last two decades. Time to open up and have a fresh look at complementary adjuvant treatment options. Hyperthermia may be one such option. Hyperthermic intraperitoneal chemotherapy (HIPEC) predominantly as a intrasurgical procedure has already proved its justification. Non-invasive loco regional hyperthermia as complement to either chemo or radiation has not yet reached a comparable status of evidence. However the potential to eventually grow into such evidence is already clearly observable. This review presents the various methodologies available for hyperthermia, covers the initial clinical data that has been published and gives an outlook to what can be expected in the next 2-3 years to come. Hyperthermia has the potential to significantly prolong life expectancies and this while maintaining a satisfying quality of life!

Science to practice: Can we turn the undesired heating effects of MR imaging into effective cancer therapies?

In this basic research study, Zhang et al created and report on a clever magnetic resonance (MR)-guided radiofrequency (RF) system that enables focal hyperthermic heating, targeting, and visualization for the treatment of cholangiocarcinoma. The key novelty is creating localized MR-induced heating around a metallic guidewire, which they subsequently demonstrate can be successfully combined with chemotherapy to (a) reduce cell proliferation in vitro, (b) decrease tumor growth in mouse xenografts, and (c) increase biliary uptake of chemotherapeutic drugs in swine. An added benefit of the system is using the wire as an intraluminal receiver antenna to improve the resolution of intraprocedural imaging guidance.