Combining Nanocarrier-Assisted Delivery of Molecules and Radiotherapy

Cancer is responsible for a significant proportion of death all over the world. Therefore, strategies to improve its treatment are highly desired. The use of nanocarriers to deliver anticancer treatments has been extensively investigated and improved since the approval of the first liposomal formulation for cancer treatment in 1995. Radiotherapy (RT) is present in the disease management strategy of around 50% of cancer patients. In the present review, we bring the state-of-the-art information on the combination of nanocarrier-assisted delivery of molecules and RT. We start with formulations designed to encapsulate single or multiple molecules that, once delivered to the tumor site, act directly on the cells to improve the effects of RT. Then, we describe formulations designed to modulate the tumor microenvironment by delivering oxygen or to boost the abscopal effect. Finally, we present how RT can be employed to trigger molecule delivery from nanocarriers or to modulate the EPR effect.

Triggered Drug Release From Liposomes: Exploiting the Outer and Inner Tumor Environment

Since more than 40 years liposomes have being extensively studied for their potential as carriers of anticancer drugs. The basic principle behind their use for cancer treatment consists on the idea that they can take advantage of the leaky vasculature and poor lymphatic drainage present at the tumor tissue, passively accumulating in this region. Aiming to further improve their efficacy, different strategies have been employed such as PEGlation, which enables longer circulation times, or the attachment of ligands to liposomal surface for active targeting of cancer cells. A great challenge for drug delivery to cancer treatment now, is the possibility to trigger release from nanosystems at the tumor site, providing efficacious levels of drug in the tumor. Different strategies have been proposed to exploit the outer and inner tumor environment for triggering drug release from liposomes and are the focus of this review.

The Emerging Role of miRNAs for the Radiation Treatment of Pancreatic Cancer

Simple Summary

Pancreatic cancer is an aggressive disease with a high mortality rate. Radiotherapy is one treatment option within a multimodal therapy approach for patients with locally advanced, non-resectable pancreatic tumors. However, radiotherapy is only effective in about one-third of the patients. Therefore, biomarkers that can predict the response to radiotherapy are of utmost importance. Recently, microRNAs, small non-coding RNAs regulating gene expression, have come into focus as there is growing evidence that microRNAs could serve as diagnostic, predictive and prognostic biomarkers in various cancer entities, including pancreatic cancer. Moreover, their high stability in body fluids such as serum and plasma render them attractive candidates for non-invasive biomarkers. This article describes the role of microRNAs as suitable blood biomarkers and outlines an overview of radiation-induced microRNAs changes and the association with radioresistance in pancreatic cancer.

Abstract

Today, pancreatic cancer is the seventh leading cause of cancer-related deaths worldwide with a five-year overall survival rate of less than 7%. Only 15–20% of patients are eligible for curative intent surgery at the time of diagnosis. Therefore, neoadjuvant treatment regimens have been introduced in order to downsize the tumor by chemotherapy and radiotherapy. To further increase the efficacy of radiotherapy, novel molecular biomarkers are urgently needed to define the subgroup of pancreatic cancer patients who would benefit most from radiotherapy. MicroRNAs (miRNAs) could have the potential to serve as novel predictive and prognostic biomarkers in patients with pancreatic cancer. In the present article, the role of miRNAs as blood biomarkers, which are associated with either radioresistance or radiation-induced changes of miRNAs in pancreatic cancer, is discussed. Furthermore, the manuscript provides own data of miRNAs identified in a pancreatic cancer mouse model as well as radiation-induced miRNA changes in the plasma of tumor-bearing mice.

Combined paclitaxel-doxorubicin liposomal results in positive prognosis with infiltrating lymphocytes in lung metastasis

Aim: To investigate the effect of liposomes containing the classical cytotoxic drugs paclitaxel and doxorubicin (Lipo-Pacli/Dox), against a metastatic breast cancer model. We also investigated if Lipo-Pacli/Dox was capable of reverting the tolerogenic environment of metastatic lesions. Materials & methods: Immunogenic cell death induction by the Pacli/Dox combination was assessed in vitro. Antitumor activity and in vivo safety of Lipo-Pacli/Dox were evaluated using a 4T1 breast cancer mouse model Results: Lipo-Pacli/Dox, with a size of 189 nm and zeta potential of -5.01 mV, promoted immune system activation and partially controlled the progression of pulmonary metastasis. Conclusion: Lipo-Pacli/Dox was useful to control both primary tumor and lung metastasis in breast cancer (4T1) mice model. Additionally, Lipo-Pacli/Dox acts as an immunological modulator for this metastatic breast cancer model.

Alpha-tocopheryl succinate improves encapsulation, pH-sensitivity, antitumor activity and reduces toxicity of doxorubicin-loaded liposomes

Doxorubicin (DOX) plays an important role in cancer treatment; however, high cardiotoxicity and low penetration in solid tumors are the main limitations of its use. Liposomal formulations have been developed to attenuate the DOX toxicity, but the technological enhancement of the liposomal formulation as well as the addition of another agent with antitumor properties, like alpha-tocopheryl succinate (TS), a semi-synthetic analog of vitamin E, could certainly bring benefits. Thus, in this study, it was proposed the development of liposomes composed of DOX and TS (pHSL-TS-DOX). A new DOX encapsulation method, without using the classic ammonium sulfate gradient with high encapsulation percentage was developed. Analysis of Small Angle X-ray Scattering (SAXS) and release study proved the pH-sensitivity of the developed formulation. It was observed stabilization of tumor growth using pHSL-TS-DOX when compared to free DOX. The toxicity tests showed the safety of this formulation since it allowed body weight initial recovery after the treatment and harmless to heart and liver, main target organs of DOX toxicity. The developed formulation also avoided the occurrence of myelosuppression, a typical adverse effect of DOX. Therefore, pHSL-TS-DOX is a promising alternative for the treatment of breast cancer since it has adequate antitumor activity and a safe toxicity profile.

Development of Long-Circulating and Fusogenic Liposomes Co-encapsulating Paclitaxel and Doxorubicin in Synergistic Ratio for the Treatment of Breast Cancer

Background:

The co-encapsulation of paclitaxel (PTX) and doxorubicin (DXR) in liposomes has the potential to offer pharmacokinetic and pharmacodynamic advantages, providing delivery of both drugs to the tumor at the ratio required for synergism.

Objective:

To prepare and characterize long-circulating and fusogenic liposomes co-encapsulating PTX and DXR in the 1:10 molar ratio (LCFL-PTX/DXR).

Methods:

LCFL-PTX/DXR was prepared by the lipid film formation method. The release of PTX and DXR from liposomes was performed using a dialysis method. Studies of cytotoxicity, synergism, and cellular uptake were also carried out.

Results:

The encapsulation percentage of PTX and DXR was 74.1 ± 1.8 % and 89.6 ± 12.3%, respectively, and the mean diameter of the liposomes was 244.4 ± 28.1 nm. The vesicles remained stable for 30 days after their preparation. The drugs were simultaneously released from vesicles during 36 hours, maintaining the drugs combination in the previously established ratio. Cytotoxicity studies using 4T1 breast cancer cells showed lower inhibitory concentration 50% (IC50) value for LCFL-PTX/DXR treatment (0.27 ± 0.11 µm) compared to the values of free drugs treatment. In addition, the combination index (CI) assessed for treatment with LCFL-PTX/DXR was equal to 0.11 ± 0.04, showing strong synergism between the drugs. Cell uptake studies have confirmed that the molar ratio between PTX and DXR is maintained when the drugs are administered in liposomes.

Conclusion:

It was possible to obtain LCFL-PTX/DXR suitable for intravenous administration, capable of releasing the drugs in a fixed synergistic molar ratio in the tumor region.

Short and Long-Term Effects of the Exposure of Breast Cancer Cell Lines to Different Ratios of Free or Co-Encapsulated Liposomal Paclitaxel and Doxorubicin

Background: Associating paclitaxel (PTX) to doxorubicin (DXR) is one of the main chemotherapy strategies for breast cancer (BC) management. Protocols currently available consist in administering both drugs on their maximum tolerated dose, not taking into account the possible differences in efficacy due to their combination ratio. In the present study, the short and long-term cytotoxic effects as well as migratory effects of PTX, DXR, and its combinations at 10:1; 1:1 and 1:10 PTX:DXR molar ratios either free or co-encapsulated in liposomes were evaluated against three human BC cell lines (MDA-MB-231, MCF-7, and SKBR-3). Method: The MTT assay was used to screen for synergy or antagonism between PTX and DXR and the combination index value was calculated using the CalcuSyn software. Nuclear morphological alterations were evaluated by staining the cells with Hoescht 33342. The investigation of senescence and clonogenicity of BC cell lines exposed to different treatments was also studied. In addition, the ability of these cells to migrate was assessed. Results: Taken together, the results presented herein allow us to suggest that there is no benefit in enhancing the PTX concentration above that of DXR in the combination for any of the three cell lines tested. Conclusion: The developed liposomes co-encapsulating PTX and DXR in different molar ratios retained the biological properties of the mixture of free drugs and are valuable for planning new therapeutic strategies.

Ratiometric drug delivery using non-liposomal nanocarriers as an approach to increase efficacy and safety of combination chemotherapy

The observation that different drug ratios of the same drug combination can lead to synergistic or antagonistic effects when tested against the same cancer cell line in vitro gave rise to a new trend, the ratiometric delivery. This strategy consists of co-encapsulating a specific synergistic ratio of a drug combination into a nanocarrier so that synergism observed in vitro will be faithfully translated to in vivo, optimizing combination therapy. In this review we focus on how to quantify synergism in vitro, followed by how this affected the evolution of nanocarriers culminating in the ratiometric delivery, and finally we summarize the results of the non-liposomal formulations that were built upon this concept.

Production of the Cytotoxic Cardenolide Glucoevatromonoside by Semisynthesis and Biotransformation of Evatromonoside by a Digitalis lanata Cell Culture

Recent studies demonstrate that cardiac glycosides, known to inhibit Na⁺/K⁺-ATPase in humans, have increased susceptibility to cancer cells that can be used in tumor therapy. One of the most promising candidates identified so far is glucoevatromonoside, which can be isolated from the endangered species Digitalis mariana ssp. heywoodii. Due to its complex structure, glucoevatromonoside cannot be obtained economically by total chemical synthesis. Here we describe two methods for glucoevatromonoside production, both using evatromonoside obtained by chemical degradation of digitoxin as the precursor. 1) Catalyst-controlled, regioselective glycosylation of evatromonoside to glucoevatromonoside using 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide as the sugar donor and 2-aminoethyldiphenylborinate as the catalyst resulted in an overall 30 % yield. 2) Biotransformation of evatromonoside using Digitalis lanata plant cell suspension cultures was less efficient and resulted only in overall 18 % pure product. Structural proof of products has been provided by extensive NMR data. Glucoevatromonoside and its non-natural 1-3 linked isomer neo-glucoevatromonoside obtained by semisynthesis were evaluated against renal cell carcinoma and prostate cancer cell lines.

Common-garden experiments reveal geographical variation in the interaction among Crotalaria pallida (Leguminosae: Papilionideae), Utetheisa ornatrix L. (Lepidoptera: Arctiidae), and extrafloral nectary visiting ants

The study of geographical variation is a key approach to understand evolution of ecological interactions. We investigated geographical variation in the interaction among Crotalaria pallida (Leguminosae: Papilionideae), its specialized herbivore, Utetheisa ornatrix L. (Lepidoptera: Arctiidae), and ants attracted to extrafloral nectaries (EFNs). First, we used common-garden experiments with plants collected in different sites at different geographical scales to test for differences among populations in C. pallida attractiveness to ants. When we compared three populations from Southeast Brazil (150 km apart), the number of visiting ants per plant, and the percent of termite baits attacked by ants, were significantly different among plant populations. In a comparison of populations from SE Brazil and Florida (USA), there was no significant difference between the populations in the number of ants per plant or the frequency of baits attacked. Second, we tested in a common garden if U. ornatrix larvae present any behavior to avoid ant predation, and if there were genetic differences among populations. We observed that most larvae moved away from the vicinity of the EFNs (flowers and fruits) to the plant leaves. Of the larvae that moved to leaves, only 10% were attacked by ants while 89% of larvae that stayed near the fruit/flower were attacked. There was a significant difference among populations in the frequency of larvae that moved to the leaves and the frequency of larvae attacked by ants. We discuss the possible causes of the geographical differences observed and propose future research directions in this system.

Increased cation permeability in mutant mouse red blood cells with defective membrane skeletons

Cellular cation homeostasis in mouse erythrocytes with defective membrane skeletons was examined in three mouse mutants, hemolytic anemia (sphha/sphha), spherocytosis (sph/sph), and normoblastosis (nb/nb), and compared with reticulocytes produced by repetitive bleeding of congenic normal mice. To assess reticulocyte maturity, nucleic acid and transferrin receptor contents were measured by fluorescence flow cytometry; mutant cells were somewhat more mature than normal reticulocytes by these criteria. Red blood cell (RBC) sodium contents (Nac+) in homozygous sphha/sphha, sph/sph, and nb/nb animals were 30.1 +/- 0.9, 28.9 +/- 0.3, and 26.9 +/- 1.5 mmol/L cell, respectively, whereas cellular potassium (Kc+) was 102 +/- 2.6, 101 +/- 7.8, and 97.4 +/- 3.0. Nac+ and Kc+ in normal reticulocyte preparations were 11.3 +/- 0.7 and 123 +/- 10, respectively. Net Na+ and K+ fluxes in the presence of ouabain were markedly increased in mutant RBCs. Sodium uptake was 14.8 +/- 1.6, 15.4 +/- 3.3, and 14.7 +/- 3.1 mmol/L cell/h in sphha/sphha, sph/sph, and nb/nb mutants, respectively, whereas K+ loss was 17.0 +/- 4.0, 15.0 +/- 3.8, and 14.1 +/- 2.6. Normal mouse reticulocytes gained Na+ at a rate of 3.9 +/- 1.0 mmol/L cell/h and lost K+ at 6.0 +/- 2.1, rates indistinguishable from those in mature mouse RBCs. Potassium loss from sphha/sphha and nb/nb cells was not dependent on the presence of a Na+ gradient, and net cation movements were insensitive to bumetanide (sphha/sphha and nb/nb RBCs) and to chloride replacement with sulfamate (nb/nb cells). We conclude that mutant mouse RBCs with dysfunctional membrane skeletons have increased passive permeability to monovalent cations. These findings support a role of the membrane skeleton in the maintenance of the membrane permeability barrier and suggest that the abnormal permeability associated with human hereditary spherocytosis and elliptocytosis may be a consequence of the membrane skeleton defects reported in these disorders.