Calcitriol-Loaded Dual-pH-Sensitive Micelle Counteracts Pro-Metastasis Effect of Paclitaxel in Triple-Negative Breast Cancer Therapy

Bruceine A: Suppressing metastasis via MEK/ERK pathway and invoking mitochondrial apoptosis in triple-negative breast cancer

Triple-negative breast cancer (TNBC), as the most aggressive subtype of breast cancer, presents a scarcity of miraculous drugs in suppressing its proliferation and metastasis. Bruceine A (BA) is a functional group-rich quassin compound with extensive and distinctive pharmacological activities. Within the present study, we investigated the capabilities of BA in suppressing TNBC proliferation and metastasis as well as its potential mechanisms. The results displayed that BA dramatically repressed the proliferation of MDA-MB-231 and 4T1 cells with corresponding IC50 values of 78.4 nM and 524.6 nM, respectively. Concurrently, BA arrested cells in G1 phase by downregulating cycle-related proteins Cyclin D1 and CDK4. Furthermore, BA distinctly induced mitochondrial dysfunction as manifested by diminished mitochondrial membrane potential, elevated reactive oxygen species generation, minimized ATP production, and Caspase-dependent activation of the mitochondrial apoptosis pathway. Additionally, BA restrained the invasion and metastasis of TNBC cells by repressing MMP9 and MMP2 expression. Intriguingly, after pretreatment with MEK activator C16-PAF, the inhibitory effect of BA on MEK/ERK pathway was notably diminished, while the proliferation suppression and metastasis repression exerted by BA were all strikingly curtailed. Molecular docking illustrated that BA potently combined with residues on the MEK1 protein with the presence of diverse intermolecular interactions. Ultimately, BA effectively suppressed tumor growth in the 4T1 xenograft tumor model with no detectable visceral toxicity in the high-dose group and, astonishingly, repressed tumor metastasis in the 4T1-luc lung metastasis model. Collectively, our study demonstrates that BA is a promising chemotherapeutic agent for treating TNBC and suppressing lung metastasis.

Breaking Tumor Immunosuppressive Network by Regulating Multiple Nodes with Triadic Drug Delivery Nanoparticles

Inside the tumor microenvironment, a complicated immunosuppressive network is constituted by tumor cells and suppressive immune cells as its nodes, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and regulatory T cells, which have mutual promotion on each other and superimposed inhibition on natural killer (NK) cells and cytotoxic T cells. Breaking the whole balance of this web is critical to tumor immunotherapy since modulation on a single node may be diluted by other factors in the network. To achieve multifaceted regulation on antitumor immunity against triple-negative breast cancer, in this work, a micelle, termed BEM, co-delivering the MDSC inhibitor, entinostat (ENT), and the immune checkpoint inhibitor, BMS-1, was constructed with pH-sensitive amphiphilic poly(β-amino ester) derivatives. Then, BEM and the scavenger receptor A (SR-A) ligand dextran sulfate (DXS) formed a negatively charged nanoparticle (BEN). DXS detached from BEN in the weakly acidic tumor microenvironment and blocked SR-A on TAMs, reprogramming TAMs toward the M1 type. The positively charged BEM with facilitated intratumoral penetration and cellular uptake dissociated in the lysosomes, accompanied by the release of ENT and BMS-1 to suppress MDSCs and block the programmed cell death protein (PD)-1/PD-ligand 1 pathway, respectively. As a result, NK cells and CD8+ T cells in tumors were increased, as were their effector cytokines. The activated innate and adaptive antitumor immune responses suppressed the growth and metastasis of tumors and prolonged survival of 4T1 tumor-bearing mice. BEN provides a reliable approach for improving cancer immunotherapy by destroying the immunosuppression web in tumors via multinode regulation.

Therapeutic Copolymer from Salicylic Acid and l-Phenylalanine as a Nanosized Drug Carrier for Orthotopic Breast Cancer with Lung Metastasis

Nanoparticle (NP)-mediated drug delivery systems are promising for treating various diseases. However, clinical translation has been delayed by a variety of limitations, such as weak drug loading, nonspecific drug leakage, lack of bioactivity, and short blood circulation. These issues are in part due to the unsatisfactory function of biomaterials for nanocarriers. In addition, the synthesis procedures of drug carrier materials, especially polymers, were usually complicated and led to high cost. In this report, a bioactive copolymer of hydroxy acid and amino acid, poly(salicylic acid-co-phenylalanine) (PSP), was developed for the first time via a one-step rapid and facile synthesis strategy. The PSP could self-assemble into NPs (PSP-NPs) to co-load relatively hydrophilic sphingosine kinase 1 inhibitor (PF543 in HCl salt format) and highly hydrophobic paclitaxel (PTX) to form PF543/PTX@PSP-NPs with efficient dual drug loading. Encouragingly, PF543/PTX@PSP-NPs showed long blood circulation, good stability, and high tumor accumulation, leading to significantly enhanced therapeutic effects on breast cancer. Furthermore, PF543/PTX@PSP-NPs could additionally suppress the lung metastasis of breast cancer, and more importantly, the PSP-NPs themselves as therapeutic nanocarriers also showed an anti-breast cancer effect. With these combined advantages, this new polymer and corresponding NPs will provide valuable insights into the development of new functional polymers and nanomedicines for important diseases.

Vitamin D: an essential adjuvant therapeutic agent in breast cancer

Low serum levels of vitamin D have been reported as a risk factor for breast cancer. This narrative review provides an update on the impact of vitamin D on hormone receptors, notably estrogen receptor subunits, and gives insights on possible therapeutic interventions to overcome breast cancer. In addition, evidence that supports the beneficial use of vitamin D as adjuvant treatment of breast cancer is summarized. Vitamin D deficiency is significantly widespread in patients with triple-negative tumors. Several studies have observed a possible modulatory effect of vitamin D or its analogues on the expression of different hormone receptors in breast cancer and increased sensitivity to tamoxifen. Vitamin D possesses anti-inflammatory and immunomodulatory effects in patients with breast cancer, and the mechanism of action of vitamin D in patients with breast cancer is discussed. In conclusion, vitamin D appears to have a beneficial role in the prevention and management of breast cancer, however, large-scale, randomized controlled trials are needed to confirm the effects of vitamin D in breast cancer prevention or treatment.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Lipid-Based Nanoparticles for Targeted Delivery of the Anti-Cancer Drugs: A Review

Abstract:

Cancer is one of the main reasons for mortality worldwide. Chemotherapeutic agents have been effectively designed to increase certain patients' survival rates, but ordinarily designed chemotherapeutic agents necessarily deliver toxic chemotherapeutic drugs to healthy tissues, resulting in serious side effects. Cancer cells can often acquire drug resistance after repeated dosing of current chemotherapeutic agents, restricting their efficacy. Given such obstacles, investigators have attempted to distribute chemotherapeutic agents using targeted drug delivery systems (DDSs), especially nanotechnology-based DDSs. Lipid-Based Nanoparticles (LBNPs) are a large and complex class of substances that have been utilized to manage a variety of diseases, mostly cancer. Liposomes seem to be the most frequently employed LBNPs, owing to their high biocompatibility, bioactivity, stability, and flexibility; howbeit Solid Lipid Nanoparticles (SLNs) and Non-structured Lipid Carriers (NLCs) have lately received a lot of interest. Besides that, there are several reports that concentrate on novel therapies via LBNPs to manage various forms of cancer. In the present research, the latest improvements in the application of LBNPs have been shown to deliver different therapeutic agents to cancerous cells and have been demonstrated LBNPs also can be a quite successful candidate in cancer therapy for subsequent use.

High-dose vitamin D metabolite delivery inhibits breast cancer metastasis

Besides its well-known benefits on human health, calcitriol, the hormonally active form of vitamin D3, has been being evaluated in clinical trials as an anticancer agent. However, currently available results are contradictory and not fundamentally deciphered. To the best of our knowledge, hypercalcemia caused by high-dose calcitriol administration and its low bioavailability limit its anticancer investigations and translations. Here, we show that the one-step self-assembly of calcitriol and amphiphilic cholesterol-based conjugates leads to the formation of a stable minimalist micellar nanosystem. When administered to mice, this nanosystem demonstrates high calcitriol doses in breast tumor cells, significant tumor growth inhibition and antimetastasis capability, as well as good biocompatibility. We further reveal that the underlying molecular antimetastatic mechanisms involve downregulation of proteins facilitating metastasis and upregulation of paxillin, the key protein of focal adhesion, in primary tumors.

Nano drug delivery systems improve metastatic breast cancer therapy

Despite continual progress in the technologies and regimens for cancer therapy, the treatment outcome of fatal metastatic breast cancer is far from satisfactory. Encouragingly, nanotechnology has emerged as a valuable tool to optimize drug delivery process in cancer therapy via preventing the cargos from degradation, improving the tumor-targeting efficiency, enhancing therapeutic agents' retention in specific sites, and controlling drug release. In the last decade, several mechanisms of suppressing tumor metastasis by functional nano drug delivery systems (NDDSs) have been revealed and a guidance for the rational design of anti-metastasis NDDSs is summarized, which consist of three aspects: optimization of physiochemical properties, tumor microenvironment remodeling, and biomimetic strategies. A series of medicinal functional biomaterials and anti-metastatic breast cancer NDDSs constructed by our team are introduced in this review. It is hoped that better anti-metastasis strategies can be inspired and applied in clinic.

Combinations of Calcitriol with Anticancer Treatments for Breast Cancer: An Update

Preclinical, clinical, and epidemiological studies indicate that vitamin D3 (VD) deficiency is a risk factor for the development of breast cancer. Underlying mechanisms include the ability of calcitriol to induce cell differentiation, inhibit oncogenes expression, and modify different signaling pathways involved in the control of cell proliferation. In addition, calcitriol combined with different kinds of antineoplastic drugs has been demonstrated to enhance their beneficial effects in an additive or synergistic fashion. However, a recognized adjuvant regimen based on calcitriol for treating patients with breast cancer has not yet been fully established. Accordingly, in the present work, we review and discuss the preclinical and clinical studies about the combination of calcitriol with different oncological drugs, aiming to emphasize its main therapeutic benefits and opportunities for the treatment of this pathology.

Stromal Barrier-Dismantled Nanodrill-Like and Cancer Cell-Targeted pH-Responsive Polymeric Micelles for Further Enhancing the Anticancer Efficacy of Doxorubicin

Cancer-associated fibroblasts (CAFs) were believed to establish a tight physical barrier and a dense scaffold for tumor cells to make them maintain immunosuppression and drug resistance, strongly hindering nanoparticles to penetrate into the core of tumor tissues and limiting the performance of tumor cell-targeted nanoparticles. Here, we fabricated the substrate Z-Gly-Pro of fibroblast activation protein α (FAPα) and folic acid-codecorated pH-responsive polymeric micelles (dual ligand-modified PEOz-PLA polymeric micelles, DL-PP-PMs) that possessed nanodrill and tumor cell-targeted functions based on Z-Gly-pro-conjugated poly(2-ethyl-2-oxazoline)-poly(D,l-lactide) (ZGP-PEOz-PLA), folic acid (FA)-conjugated PEOz-PLA (FA-PEOz-PLA), and PEOz-PLA for cancer therapy. The micelles with about 40 nm particle size and a narrow distribution exhibited favorable pH-activated endo/lysosome escape induced by their pH responsibility. In addition, the enhancement of in vitro cellular uptake and cytotoxicity to folate receptors or FAPα-positive cells for doxorubicin (DOX)/DL-PP-PMs compared with DOX/PP-PMs evidenced the dual target ability of DOX/DL-PP-PMs, which was further supported by in vivo biodistribution results. As expected, in the human oral epidermal carcinoma (KB) cells xenograft nude mice model, the remarkable enhancement of antitumor efficacy for DOX/DL-PP-PMs with low toxicity was observed compared with DOX/FA-PP-PMs and DOX/ZGP-PP-PMs. The possible mechanism was elucidated to be the dismantling of the stromal barrier by nanodrill-like DOX/DL-PP-PMs via the deletion of CAFs evidenced by the downregulation of α-SMA and inhibition of their functions proved by the decrease in the microvascular density labeled with CD31 and the reduction in the extracellular matrix detected by the collagen content, thereby promoting tumor penetration and enhancing their uptake by tumor cells. The present research offered an alternative approach integrating anticancer and antifibrosis effects in one delivery system to enhance the delivery efficiency and therapeutic efficacy of anticancer drugs.

Construction and antitumor properties of a targeted nano-drug carrier system responsive to the tumor microenvironment

Doxorubicin (DOX) is one of the most commonly used and effective chemotherapy drugs among anthracyclines. An inherent limitation of DOX is its nonspecificity, which can cause serious side effects, thereby preventing the therapeutic use of high drug doses. In this study, we designed and created a simple nano-drug delivery system (PEG-MAF = P) with low biological toxicity that was responsive to the tumor environment. PEG-MAF = P was designed to self-assemble into nanospheres via control of a phenylalanine dipeptide (FF). The N-terminus of the peptide was linked to aldehyde groups at both ends of oxidized Pluronic F127 (F127-CHO) via Schiff bonds. The acidic environment surrounding the tumors was suitable for triggering the Schiff bonds, causing the nanospheres to disintegrate. The C-terminus of FF was connected to a ligand peptide, ATN-161, which was able to recognize cells expressing high levels of integrin α5β1 antigens both in vivo and in vitro. To prevent the impediment in drug release, PEG was linked via a matrix metalloproteinase-9 response peptide. Therefore, in an acidic tumor microenvironment containing MMP-9, PEG-MAF = P disintegrated and rapidly released the drug. PEG-MAF = P exhibited low cytotoxicity, high drug-loading rate, and excellent antitumor properties both in vivo and in vitro. Compared with free DOX, PEG-MAF = P-DOX reduced injury to normal tissues.

Smart Polymeric Nanoparticles with pH-Responsive and PEG-Detachable Properties (II): Co-Delivery of Paclitaxel and VEGF siRNA for Synergistic Breast Cancer Therapy in Mice

Background

The dual-loaded nano-delivery system can realize chemotherapeutic drug and small interfering RNA (siRNA) co-loading as well as enhance the therapeutic effect of drugs on tumors through a synergistic effect, while reducing their toxic and side effects on normal tissues.

Methods

Previously, we developed layered smart nanoparticles (NPs) to co-deliver survivin siRNA as well as small molecule drugs for lung cancer. In this study, we used such smart NPs to co-deliver paclitaxel (PTX) and siRNA against vascular endothelial growth factor (VEGF) gene for breast cancer therapy in mice models. For the prepared NPs, characterizations such as particle size, zeta potential, gel electrophoresis imaging and in vitro stability were investigated. Then, 4T1 cells were used to evaluate the in vitro VEGF silencing capacity, tumor cell inhibitory and anti-apoptotic abilities. Finally, an orthotopic model of mouse breast cancer was established to evaluate the in vivo antitumor effects and safety properties of PTX-siRNA^VEGF-NPs.

Results

We prepared PTX-siRNA^VEGF-NPs with particle size of 85.25 nm, PDI of 0.261, and zeta potential of 5.25 mV. The NPs with VEGF siRNA effectively knocked down the expression of VEGF mRNA. Cell counting kit-8 (CCK-8) and apoptosis assays revealed that the PTX-siRNA^VEGF-NPs exhibited antiproliferation effect of PTX on 4T1 cells. The in vivo anti-tumor study indicated that PTX-siRNA^VEGF-NPs could exert an antitumor effect by inhibiting the formation and development of new blood vessels in tumor tissues, thereby cutting off nutrient and blood supplies required for tumor tissue growth. Both the anti-tumor efficacy and in vivo safety of the PTX-siRNA^VEGF-NPs group were better than that of the PTX-NPs and siRNA^VEGF-NPs groups.

Conclusion

The combination of PTX and VEGF siRNA exerts good antitumor effect on 4T1 tumor cells. This study provides a theoretical and practical basis for breast cancer therapy.

Emerging nanotaxanes for cancer therapy

The clinical application of taxane (including paclitaxel, docetaxel, and cabazitaxel)-based formulations is significantly impeded by their off-target distribution, unsatisfactory release, and acquired resistance/metastasis. Recent decades have witnessed a dramatic progress in the development of high-efficiency, low-toxicity nanotaxanes via the use of novel biomaterials and nanoparticulate drug delivery systems (nano-DDSs). Thus, in this review, the achievements of nanotaxanes-targeted delivery and stimuli-responsive nano-DDSs-in preclinical or clinical trials have been outlined. Then, emerging nanotherapeutics against tumor resistance and metastasis have been overviewed, with a particular emphasis on synergistic therapy strategies (e.g., combination with surgery, chemotherapy, radiotherapy, biotherapy, immunotherapy, gas therapy, phototherapy, and multitherapy). Finally, the latest oral nanotaxanes have been briefly discussed.