br Corresponding author br E mail address torsko
E-mail address: [email protected] (T. Skotland).
1 Equal contribution.
Available online 04 December 2018
0168-3659/ © 2018 Oslo University Hospital. Published by Elsevier B.V. This is an open access article under the CC BY license
Chemotherapy has during recent years improved the treatment and prognosis of different cancers, but the therapeutic effect is not sufficient for certain cancer types and the treatment may also result in unwanted side effects. Several products of drug-loaded NPs have reached the market, and many new product candidates are in clinical trials. These aspects, including the challenges and opportunities of using nano-particles in cancer drug delivery, have been discussed in several reviews [1,2]. In addition to improving efficacy by benefiting from the en-hanced permeability and retention (EPR) effect , NP encapsulated drug delivery may demonstrate reduced toxicity. The main advantage of the drug-loaded NPs that have reached the market is that they give less adverse effects than free drug, while the therapeutic efficacy is rather similar .
Poly(alkyl cyanoacrylate) (PACA) was first developed and approved as surgical glue, and has later demonstrated promising abilities as a drug carrier, being biodegradable and allowing high drug loading ca-pacity . We have earlier shown that the degradation rate of PACA NPs can be controlled by the choice of the alkyl chain of the cyanoa-crylate monomer , and we recently demonstrated, using a panel of cell lines, that the cytotoxicity was dependent on the monomers used, i.e. n-butyl-, 2-ethyl-butyl-, or octyl cyanoacrylate (PBCA, PEBCA and POCA, respectively) . Based on this experience the present study was initiated to evaluate the effect of PEBCA NPs in breast cancer.
The PEBCA NPs used in this study contain the cytotoxic drug ca-bazitaxel (CBZ), a semi-synthetic taxane derivative which inhibits mi-crotubule disassembly . CBZ is approved by the US Food and Drug Administration (FDA) for treatment of refractory prostate cancer as a second line drug after docetaxel chemotherapy [9,10]. One advantage of CBZ is its low affinity for P-glycoprotein, thus reducing the possibi-lity of obtaining drug resistance [8,11]. The very low water solubility of CBZ complicates administration of the free drug. However, the ex-cellent compatibility and solubility of CBZ in alkyl cyanoacrylate monomer solution allows for encapsulation of high concentrations of the drug in PACAs. The NPs were surface modified with the poly-ethylene glycol (PEG)-containing PX478 Pluronic F68 and Kolliphor HS15 to obtain an increased circulation time after intravenous (i.v.) injection .
Breast cancer can be classified into major subgroups based on the gene expression pattern. Tumors belonging to the most aggressive subtypes are commonly treated with antracycline- and taxane-based chemotherapy regimens. In particular, for hormone receptor and HER2 negative (often basal-like) tumors no targeted therapies are available, and the patients would therefore benefit from improved chemotherapy regimens . One strategy may be to use NPs as encapsulation of doxorubicine in liposomes has been reported to increase drug uptake into breast cancer [14,15]. In the current study, the growth inhibitory effect of CBZ encapsulated into PEBCA NPs was evaluated in breast cancer models in vitro and in vivo. Three breast cancer cell lines re-presenting the two main types of breast cancer, the luminal and basal-like subgroups, were used. One of the cell lines was also injected and grown in the mammary fat pad of immunodeficient mice. Additionally, one patient-derived xenograft (PDX) model previously demonstrated to be triple negative and representative for aggressive basal like breast cancer  was included in the study.
The main finding is the improved therapeutic effect of PEBCA-CBZ compared to free CBZ (i.e. the Jevtana® formulation) demonstrated in the basal-like PDX model. Immunohistochemical staining revealed a lower content of pro-tumorigenic macrophages in the PEBCA-CBZ treated tumors than in tumors treated with free CBZ, which may partly explain the improved efficacy. To elucidate the difference in efficacy of PEBCA-CBZ and free CBZ, we also showed in vivo biodistribution of particles loaded with the lipophilic fluorescent substance NR668. Furthermore, we used quantitative LC-MS/MS analyses to describe the biodistribution of CBZ in tissues and the kinetics of CBZ in blood plasma Journal of Controlled Release 293 (2019) 183–192
after injection of both PEBCA-CBZ and free CBZ.
2. Materials and methods
2.1. Synthesis and characterization of nanoparticles
PEGylated PEBCA NPs were synthesized by miniemulsion poly-merization. An oil phase consisting of 2.5 g 2-ethylbutyl cyanoacrylate (monomer, Cuantum Medical Cosmetics, Spain) containing 0.2% (w/w) butylated hydroxytoluene (Fluka, Switzerland), and 2% (w/w) Miglyol 812 (Cremer, USA) was prepared. Fluorescent particles for optical imaging were prepared by adding NR668 (modified Nile Red) , custom synthesis, 0.2% (w/w) to the oil phase. Particles containing cytostatic drug for treatment were prepared by adding CBZ (10% (w/ w), Biochempartner Co. Ltd., China, product item number BCP02404) to the oil phase, whereas vanillin (10% (w/w), Sigma-Aldrich, France) was used as an inert model drug in control particles.