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

Abstract

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.

Thermal combination therapies for local drug delivery by magnetic resonance-guided high-intensity focused ultrasound

“…For all groups, an increasing liposomal uptake in tumors was observed over time due to the "enhanced permeability and retention (EPR) effect" intrinsic to most tumor tissues (44,45). It is previously reported that hyperthermia can increase the EPRdriven uptake of liposomes in the tumor (41,(46)(47)(48), which could lead to additional dox uptake from residual nonreleased TSLs over time. However, this increase in EPR effect can be tumor-dependent (46) and for the R1 rhabdomyosarcomas studied here, no HIFU-induced increase in EPR effect was observed as all groups showed comparable TSL uptake 48 h after injection.…”

“…It is previously reported that hyperthermia can increase the EPRdriven uptake of liposomes in the tumor (41,(46)(47)(48), which could lead to additional dox uptake from residual nonreleased TSLs over time. However, this increase in EPR effect can be tumor-dependent (46) and for the R1 rhabdomyosarcomas studied here, no HIFU-induced increase in EPR effect was observed as all groups showed comparable TSL uptake 48 h after injection. For both hyperthermia-treated animals and animals that did not receive HIFU treatment, SPECT imaging showed a relatively homogeneous uptake across the tumor, with a trend of increasing TSL concentration over 48 h. Although uptake of TSLs is a slow process with typical maximum tumor concentration reached after 8-48 h (46), the therapeutically relevant process is the intravascular release of dox from TSLs, which takes place while hyperthermia is applied, that is, within the first 40 min after injection of TSLs.…”

Image-guided thermosensitive liposomes for focused ultrasound drug delivery: Using NIRF-labelled lipids and topotecan to visualise the effects of hyperthermia in tumours

“…showing that the two stage HT treatment protocol has substantial advantages [63]. In our study presented here we apply the repeated FUS protocols sequentially post injection.…”

Thermal-sensitive magnetic nanoparticles for dual-modal tumor imaging and therapy

“…10 Among the various types of combination therapies, combined hyperthermia and chemotherapy could trigger drug release from drug carriers inside cells, enhance drug uptake by cells, or enhance antitumor efficacy via a synergistic effect. 4,11 Recently, "nanotheranostics" has attracted much attention due to the development of nanomaterials with integrated diagnostic and therapeutic functions. [12][13][14][15][16] These nanomaterials can simultaneously serve as multifunctional contrast agents, such as for magnetic resonance (MR), ultrasound (US) or uorescence imaging of tumors and drug delivery or ablation of tumors.…”