Nanomedicine strategies for sustained, controlled and targeted treatment of cancer stem cells

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

PLGA nanomedical consignation: A novel approach for the management of prostate cancer

The malignancy of the prostate is a complicated ailment which impacts millions of male populations around the globe. Despite the multitude of endeavour accomplished within this domain, modalities that are involved in the ameliorative management of predisposed infirmity are still relent upon non-specific and invasive procedures, thus imposing a detrimental mark on the living standard of the individual. Also, the orchestrated therapeutic interventions are still incompetent in substantiating a robust and unabridged therapeutic end point owing to their inadequate solubility, low bioavailability, limited cell assimilation, and swift deterioration, thereby muffling the clinical application of these existing treatment modalities. Nanotechnology has been employed in an array of modalities for the medical management of malignancies. Among the assortment of available nano-scaffolds, nanocarriers composed of a bio-decomposable and hybrid polymeric material like PLGA hold an opportunity to advance as standard chemotherapeutic modalities. PLGA-based nanocarriers have the prospect to address the drawbacks associated with conventional cancer interventions, owing to their versatility, durability, nontoxic nature, and their ability to facilitate prolonged drug release. This review intends to describe the plethora of evidence-based studies performed to validate the applicability of PLGA nanosystem in the amelioration of prostate malignancies, in conjunction with PLGA focused nano-scaffold in the clinical management of prostate carcinoma. This review seeks to explore numerous evidence-based studies confirming the applicability of PLGA nanosystems in ameliorating prostate malignancies. It also delves into the role of PLGA-focused nano-scaffolds in the clinical management of prostate carcinoma, aiming to provide a comprehensive perspective on these advancements.

Targeting Cancer Stem Cells as the Key Driver of Carcinogenesis and Therapeutic Resistance

The emerging concept of cancer stem cells (CSCs) as the key driver behind carcinogenesis, progression, and diversity has displaced the prior model of a tumor composed of cells with similar subsequently acquired mutations and an equivalent capacity for renewal, invasion, and metastasis. This significant change has shifted the research focus toward targeting CSCs to eradicate cancer. CSCs may be characterized using cell surface markers. They are defined by their capacity to self-renew and differentiate, resist conventional therapies, and generate new tumors following repeated transplantation in xenografted mice. CSCs' functional capabilities are governed by various intracellular and extracellular variables such as pluripotency-related transcription factors, internal signaling pathways, and external stimuli. Numerous natural compounds and synthetic chemicals have been investigated for their ability to disrupt these regulatory components and inhibit stemness and terminal differentiation in CSCs, hence achieving clinical implications. However, no cancer treatment focuses on the biological consequences of these drugs on CSCs, and their functions have been established. This article provides a biomedical discussion of cancer at the time along with an overview of CSCs and their origin, features, characterization, isolation techniques, signaling pathways, and novel targeted therapeutic approaches. Additionally, we highlighted the factors endorsed as controlling or helping to promote stemness in CSCs. Our objective was to encourage future studies on these prospective treatments to develop a framework for their application as single or combined therapeutics to eradicate various forms of cancer.

Hydrogels: Properties and Applications in Biomedicine

Hydrogels are crosslinked polymer chains with three-dimensional (3D) network structures, which can absorb relatively large amounts of fluid. Because of the high water content, soft structure, and porosity of hydrogels, they closely resemble living tissues. Research in recent years shows that hydrogels have been applied in various fields, such as agriculture, biomaterials, the food industry, drug delivery, tissue engineering, and regenerative medicine. Along with the underlying technology improvements of hydrogel development, hydrogels can be expected to be applied in more fields. Although not all hydrogels have good biodegradability and biocompatibility, such as synthetic hydrogels (polyvinyl alcohol, polyacrylamide, polyethylene glycol hydrogels, etc.), their biodegradability and biocompatibility can be adjusted by modification of their functional group or incorporation of natural polymers. Hence, scientists are still interested in the biomedical applications of hydrogels due to their creative adjustability for different uses. In this review, we first introduce the basic information of hydrogels, such as structure, classification, and synthesis. Then, we further describe the recent applications of hydrogels in 3D cell cultures, drug delivery, wound dressing, and tissue engineering.

[Targeted killing of CD133+ lung cancer stem cells using paclitaxel-loaded PLGA-PEG nanoparticles with CD133 aptamers]

OBJECTIVE

To construct a polylactic acid-glycolic acid-polyethylene glycol (PLGA-PEG) nanocarrier (N-Pac-CD133) coupled with a CD133 nucleic acid aptamer carrying paclitaxel for eliminating lung cancer stem cells (CSCs).

METHODS

Paclitaxel-loaded N-Pac-CD133 was prepared using the emulsion/solvent evaporation method and characterized. CD133⁺ lung CSCs were separated by magnetic bead separation and identified for their biological behaviors and gene expression profile. The efficiency of paclitaxel-loaded N-Pac-CD133 for targeted killing of lung cancer cells was assessed in vitro. SCID mice were inoculated with A549 cells and received injections of normal saline, empty nanocarrier linked with CD133 aptamer (N-CD133), paclitaxel, paclitaxel-loaded nanocarrier (N-Pac) or paclitaxel-loaded N-Pac-CD133 (n=8, 5 mg/kg paclitaxel) on days 10, 15 and 20, and the tumor weight and body weight of the mice were measured on day 40.

RESULTS

Paclitaxel-loaded N-Pac-CD133 showed a particle size of about 100 nm with a high encapsulation efficiency (>80%) and drug loading rate (>8%), and was capable of sustained drug release within 48 h. The CD133⁺ cell population in lung cancer cells showed the characteristic features of lung CSCs, including faster growth rate (30 days, P=0.001) and high expressions of tumor stem cell markers OV6(P < 0.001), CD133 (P=0.001), OCT3/4 (P=0.002), EpCAM (P=0.04), NANOG (P=0.005) and CD44 (P=0.02). Compared with N-Pac and free paclitaxel, paclitaxel-loaded N-Pac-CD133 showed significantly enhanced targeting ability and cytotoxicity against lung CSCs in vitro (P < 0.001) and significantly reduced the formation of tumor spheres (P < 0.001). In the tumor-bearing mice, paclitaxel-loaded N-Pac-CD133 showed the strongest effects in reducing the tumor mass among all the treatments (P < 0.001).

CONCLUSION

CD133 aptamer can promote targeted delivery of paclitaxel to allow targeted killing of CD133⁺ lung CSCs. N-Pac-CD133 loaded with paclitaxel may provide an effective treatment for lung cancer by targeting the lung cancer stem cells.

Nanosized Drug Delivery Systems for Breast Cancer Stem Cell Targeting

Breast cancer stem cells (BCSCs), also known as breast cancer initiating cells, are reported to be responsible for the initiation, progression, therapeutic resistance, and relapse of breast cancer. Conventional therapeutic agents mainly kill the bulk of breast tumor cells and fail to eliminate BCSCs, even enhancing the fraction of BCSCs in breast tumors sometimes. Therefore, it is essential to develop specific and effective methods of eliminating BCSCs that will enhance the efficacy of killing breast tumor cells and thereby, increase the survival rates and quality of life of breast cancer patients. Despite the availability of an increasing number of anti-BCSC agents, their clinical translations are hindered by many issues, such as instability, low bioavailability, and off-target effects. Nanosized drug delivery systems (NDDSs) have the potential to overcome the drawbacks of anti-BCSC agents by providing site-specific delivery and enhancing of the stability and bioavailability of the delivered agents. In this review, we first briefly introduce the strategies and agents used against BCSCs and then highlight the mechanism of action and therapeutic efficacy of several state-of-the-art NDDSs that can be used to treat breast cancer by eliminating BCSCs.

89Zr-Labeled Multifunctional Liposomes Conjugate Chitosan for PET-Trackable Triple-Negative Breast Cancer Stem Cell Targeted Therapy

Purpose

Therapy for triple-negative breast cancer (TNBC) is a global problem due to lack of specific targets for treatment selection. Cancer stem cells (CSCs) are responsible for tumor formation and recurrence but also offer a promising target for TNBC-targeted therapy. Here, zirconium-89 (⁸⁹Zr)-labelled multifunctional liposomes (MLPs) surface-decorated with chitosan (CS) were fabricated to specifically target and trace cluster of differentiation 44⁺ (CD44⁺) TNBC CSCs specifically.

Patients and Methods

The biological basis of CS targeting CD44 for cancer therapy was investigated by detecting the expression of CD44 in TNBC CSCs and TNBC tissues. Molecular docking and dynamics simulations were performed to investigate the molecular basis of CS targeting CD44 for cancer therapy. Gambogic acid (GA)-loaded, ⁸⁹Zr@CS-MLPs (⁸⁹Zr-CS-GA-MLPs) were prepared, and their uptake and biodistribution were observed. The anti-tumor efficacy of ⁸⁹Zr@CS-GA-MLPs was investigated in vivo.

Results

CD44 is overexpressed in TNBC CSCs and tissues. Molecular docking and dynamics simulations showed that CS could be stably docked into the active site of CD44 in a reasonable conformation. Furthermore, ⁸⁹Zr@CS-GA-MLPs were able to bind specifically to CD44⁺ TNBC stem-like cells and accumulated in tumors of xenograft-bearing mice with excellent radiochemical stability. ⁸⁹Zr@CS-GA-MLPs loaded with GA showed remarkable anti-tumor efficacy in vivo.

Conclusion

The GA-loaded, ⁸⁹Zr-labelled, CS-decorated MLPs developed in this study represent a novel strategy for TNBC imaging and therapy.

Tuning the Surface Chemistry of Melanin-Mimetic Polydopamine Nanoparticles Drastically Enhances Their Accumulation into Excised Human Skin

Melanin-mimetic polydopamine nanoparticles (PDA NPs) are emerging as promising candidates for topical and transdermal drug delivery because they mimic melanin, a naturally occurring skin pigment. However, our knowledge of their interactions with human skin remains limited. Hence, we set out to investigate the role of PDA NP surface chemistry in modulating their skin deposition. PDA NPs were synthesized by base-catalyzed oxidative self-polymerization of dopamine and functionalized with poly(ethylene glycol) (PEG) bearing different termini to obtain neutral, anionic, cationic, and hydrophobic PEGylated NPs. NPs were characterized by dynamic light scattering, transmission electron microscopy, Fourier transform-infrared spectroscopy, and X-ray photoelectron spectroscopy. The NPs were then labeled with rhodamine B, and their skin interactions were investigated both in vitro, using a Strat-M membrane, and ex vivo, using excised whole thickness human skin. In vitro diffusion studies revealed that the NPs did not permeate transdermally, rather the NPs accumulated in the Strat-M membrane after 24 h of incubation. Membrane deposition of the NPs showed a strong dependence on surface chemistry, with anionic (unmodified and carboxyl-terminated PEGylated) NPs achieving the highest accumulation, followed by neutral and cationic NPs, whereas hydrophobic NPs achieved the lowest degree of accumulation. In ex vivo permeation studies, we observed that surface modification of PDA NPs with PEG serving as an antifouling coating is essential to maintaining colloidal stability upon skin contact. Moreover, anionic PEGylated NPs were able to achieve 78% skin accumulation, which was significantly higher than neutral and cationic NPs (51 and 34% accumulation, respectively). Our findings provide important insights into the role of surface chemistry in enhancing the skin accumulation of melanin-mimetic PDA NPs as potential sunscreens and carriers for skin-targeted treatments.

Effects of D-α-tocopherol polyethylene glycol succinate-emulsified poly(lactic-co-glycolic acid) nanoparticles on the absorption, pharmacokinetics, and pharmacodynamics of salinomycin sodium

Although salinomycin sodium (SS) has shown in-vitro potential to inhibit cancer stem cell growth and development, its low water solubility makes it a poor candidate as an oral chemotherapeutic agent. To improve the bioavailability of SS, SS was encapsulated here using D-α-tocopherol polyethylene glycol succinate (TPGS)-emulsified poly(lactic-co-glycolic acid) (PLGA) nanoparticles and compared with its parent SS in terms of absorption, pharmacokinetics, and efficacy in suppressing nasopharyngeal carcinomas stem cells. The pharmacokinetics of SS and salinomycin sodium-loaded D-α-tocopherol polyethylene glycol succinate-emulsified poly(lactic-co-glycolic acid) nanoparticles (SLN) prepared by nanoprecipitation were analyzed in-vivo by timed-interval blood sampling and oral administration of SS and SLN to rats. Sensitive liquid chromatography-mass spectrometry (LC-MS) was developed to quantify plasma drug concentrations. SS and SLN transport in Caco-2 cells was also investigated. The therapeutic efficacy of SS and SLN against cancer stem cells was determined by orally administering the drugs to mice bearing CNE1 and CNE2 nasopharyngeal carcinoma xenografts and then evaluating CD133 cell proportions and tumorsphere formation. The in-vivo trial with rats showed that the Cmax, AUC(0-t), and Tmax for orally administered SLN were all significantly higher than those for SS (P<0.05). These findings were corroborated by a Caco-2 cell Transwell assay showing that relative SLN absorption was greater than that of SS on the basis of their apparent permeability coefficients (Papp). Significantly, therapeutic SLN efficacy against nasopharyngeal carcinoma stem cells was superior to that of SS. TPGS-emulsified PLGA nanoparticles effectively increase SS solubility and bioavailability. SLN is, therefore, promising as an oral chemotherapeutic agent against cancer stem cells.

Enhanced and Prolonged Antitumor Effect of Salinomycin-Loaded Gelatinase-Responsive Nanoparticles via Targeted Drug Delivery and Inhibition of Cervical Cancer Stem Cells

Background

Cervical cancer stem cells (CCSCs) represent a subpopulation of tumor cells that possess self-renewal capacity and numerous intrinsic mechanisms of resistance to conventional chemotherapy and radiotherapy. These cells play a crucial role in relapse and metastasis of cervical cancer. Therefore, eradication of CCSCs is the primary objective in cervical cancer therapy. Salinomycin (Sal) is an agent used for the elimination of cancer stem cells (CSCs); however, the occurrence of several side effects hinders its application. Nanoscale drug-delivery systems offer great promise for the diagnosis and treatment of tumors. These systems can be used to reduce the side effects of Sal and improve clinical benefit.

Methods

Sal-loaded polyethylene glycol-peptide-polycaprolactone nanoparticles (Sal NPs) were fabricated under mild and non-toxic conditions. The real-time biodistribution of Sal NPs was investigated through non-invasive near-infrared fluorescent imaging. The efficacy of tumor growth inhibition by Sal NPs was evaluated using tumor xenografts in nude mice. Flow cytometry, immunohistochemistry, and Western blotting were used to detect the apoptosis of CSCs after treatment with Sal NPs. Immunohistochemistry and Western blotting were used to examine epithelial–mesenchymal transition (epithelial interstitial transformation) signal-related molecules.

Results

Sal NPs exhibited antitumor efficacy against cervical cancers by inducing apoptosis of CCSCs and inhibiting the epithelial–mesenchymal transition pathway. Besides, tumor pieces resected from Sal NP-treated mice showed decreased reseeding ability and growth speed, further demonstrating the significant inhibitory ability of Sal NPs against CSCs. Moreover, owing to targeted delivery based on the gelatinase-responsive strategy, Sal NPs was more effective and tolerable than free Sal.

Conclusion

To the best of our knowledge, this is the first study to show that CCSC-targeted Sal NPs provide a potential approach to selectively target and efficiently eradicate CCSCs. This renders them a promising strategy to improve the therapeutic effect against cervical cancer.

Dual-targeting nanomicelles with CD133 and CD44 aptamers for enhanced delivery of gefitinib to two populations of lung cancer-initiating cells

Lung cancer is an aggressive type of cancer that is associated with a high mortality rate. Lung cancer-initiating cells are populations of self-renewing cancer cells with pluripotent differentiation ability. Cancers typically originate from multiple phenotypically distinct cancer-initiating cells. CD133 and CD44 are specific markers that maybe used to distinguish lung cancer-initiating cells. The ability to target a variety of subsets of cancer-initiating cells instead of targeting only one population of cancer initiating-cells has the potential to increase the cancer therapeutic efficacy. In the present study, CD133 and CD44 aptamer-conjugated nanomicelles loaded with gefitinib (CD133/CD44-NM-Gef) were developed to target CD133⁺ and CD44⁺ lung cancer-initiating cells. The therapeutic efficacy of CD133/CD44-NM-Gef against lung cancer-initiating cells was assessed by evaluating cell proliferation, tumorsphere formation and detection of CD44⁺ and CD133⁺ cells using flow cytometry. The results indicated that CD133/CD44-NM-Gef targeted CD133⁺ and CD44⁺ lung cancer-initiating cells and exhibited greater therapeutic efficacy against lung cancer-initiating cells than single-target and non-targeted nanomicelles, suggesting that CD133/CD44-NM-Gef represents a promising treatment for lung cancer by specifically targeting lung cancer-initiating cells. To the best of our knowledge, the present study was the first to report on drug delivery via nanomedicines targeted to multiple populations of cancer-initiating cells using aptamers. As cancer is typically derived from phenotypically distinct cancer-initiating cells, the nanomicelle-based multiple targeting strategy provided is promising for targeting multiple subsets of cancer-initiating cell within a tumor.

Next-generation nanotheranostics targeting cancer stem cells

Cancer is depicted as the most aggressive malignancy and is one the major causes of death worldwide. It originates from immortal tumor-initiating cells called 'cancer stem cells' (CSCs). This devastating subpopulation exhibit potent self-renewal, proliferation and differentiation characteristics. Dynamic DNA repair mechanisms can sustain the immortality phenotype of cancer to evade all treatment strategies. To date, current conventional chemo- and radio-therapeutic strategies adopted against cancer fail in tackling CSCs. However, new advances in nanotechnology have paved the way for creating next-generation nanotheranostics as multifunctional smart 'all-in-one' nanoparticles. These particles integrate diagnostic, therapeutic and targeting agents into one single biocompatible and biodegradable carrier, opening up new avenues for breakthroughs in early detection, diagnosis and treatment of cancer through efficient targeting of CSCs.

Poly(lactic-co-glycolic acid) nanoparticle-mediated interleukin-12 delivery for the treatment of diabetic retinopathy

Background

Diabetic retinopathy (DR) is a complication of diabetes that affects the eyes and vision. It is a leading cause of visual impairment and blindness in working-age people. Vascular endothelial growth factor-A (VEGF-A) is a primary initiator and potential mediator of DR. Matrix metalloproteinase-9 (MMP-9) plays a progressive role in the onset and severity of DR. Interleukin-12 (IL-12) is a cytokine of the chemokine family that could reduce the levels of MMP-9 and VEGF-A and suppress tumor angiogenesis. We hypothesize that IL-12 may also have superior therapeutic efficacy against DR. However, protein drugs are prone to degradation by various proteases after drug injection. Therefore, they have short half-lives and low blood concentrations. The objective of this study was to develop IL-12-loaded nanoparticles for long-term and sustained DR treatment.

Methods

IL-12-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (IL-12-PNP) were developed by double emulsion. The characteristics, anti-DR activity, and mechanisms of IL-12-PNP were examined in vitro and in vivo.

Results

The nanoparticles had suitable particle size (~132.8 nm), drug encapsulation efficiency (~34.7%), and sustained drug release profile. Compared with IL-12 and blank nanoparticles, IL-12-PNP showed better inhibitory efficacy against VEGF-A and MMP-9 expression in rat endothelial cells and DR mouse retina. Intraocular IL-12-PNP administration significantly reduced retinal damage in DR mice as they presented with increased thickness and decreased neovascularization after treatment.

Conclusion

These data indicate that IL-12-PNP is an effective drug delivery platform for DR therapy. It restores the thickness and reduces neovascularization of the retinas of DR mice.

The sustained and targeted treatment of hemangiomas by propranolol-loaded CD133 aptamers conjugated liposomes-in-microspheres

We previously developed propranolol-encapsulated liposomes-in-microspheres (PLIM) to realize the sustained propranolol release for the treatment of hemangiomas. However, the liposomes released from the microspheres still lacked specificity for CD133-positive hemangioma-derived stem cells (HemSCs) which are considered to be the seeds of hemangiomas. Therefore, we hereby encapsulated propranolol-loaded CD133 aptamers conjugated liposomes in poly(lactic-co-glycolic acid (PLGA) microspheres to develop propranolol-loaded CD133 aptamers conjugated liposomes-in-microspheres (PCLIM), to realize the aim of the sustained and targeted therapy of hemangiomas. The evaluation of the release of propranolol from PCLIM was carried out, and the cytotoxic effect and angiogenic growth factor expression inhibitory ability of PCLIM were performed in HemSCs. The in vivo hemangioma inhibitory ability of PCLIM was also investigated in nude mice with subcutaneous human hemangiomas. PCLIM possessed a desired size of 29.2 μm, drug encapsulation efficiency (25.3%), and a prolonged drug release for 40 days. Importantly, PCLIM could inhibit HemSCs proliferation and the protein expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor-A (VEGF) in HemSCs to a greater extent compared with PLIM. In nude mice bearing hemangioma xenograft, PCLIM showed the best therapeutic efficacy towards hemangiomas, as reflected by remarkably decreased hemangioma volume, weight and microvessel density (MVD). Thus, our results demonstrated that PCLIM realized the sustained and targeted treatment of hemangiomas, resulting in remarkable inhibition of hemangiomas.

Enhanced targeting of prostate cancer-initiating cells by salinomycin-encapsulated lipid-PLGA nanoparticles linked with CD44 antibodies

Prostate cancer is the fifth most common cause of cancer-associated mortality in males worldwide. The survival of prostate cancer-initiating cells (CICs) is an important factor behind the metastasis and recurrence of prostate cancer. The cluster of differentiation (CD) 44 antigen is considered an important marker for prostate CICs. Salinomycin is a potent therapeutic drug against CICs. The present study demonstrated that salinomycin exerts potent activity against CD44⁺ prostate CICs. To further enhance this anticancer effect, salinomycin-encapsulated lipid-poly(lactic-co-glycolic acid) nanoparticles linked with CD44 antibodies (SM-LPN-CD44) were generated. The anticancer effect of the nanoparticles was investigated in a series of assays, including a cytotoxicity assay, flow cytometry and anticancer assay in prostate cancer-bearing mice in vivo. The results revealed that SM-LPN-CD44 could efficiently and specifically promote the delivery of salinomycin to CD44⁺ prostate CICs, and there by achieve greater inhibition of the cells compared with that achieved by salinomycin and non-targeted nanoparticles. To the best of our knowledge, this is the first study to report improved therapeutic effects against prostate CICs achieved by the enhancement of targeted drug delivery via nanoparticles conjugated with CD44 antibodies. Therefore, SM-LPN-CD44 nanoparticle-based therapy represents a novel approach to eliminate prostate CICs and is a promising potential treatment strategy for prostate cancer.

Lipid-polymer nanoparticles with CD133 aptamers for targeted delivery of all-trans retinoic acid to osteosarcoma initiating cells

Osteosarcoma, a common type of bone cancer in children, and represents an aggressive and fetal cancer worldwide. Osteosarcoma initiating cells are considered to be a subpopulation of cancer cells which contribute to the progression, recurrence, metastasis and multi-drug resistance of osteosarcoma. CD133 is considered to be one marker for osteosarcoma initiating cells. All-trans retinoic acid (ATRA), an active metabolite of vitamin A under the family retinoid, is an up-and-coming drug which was able to effectively treat various cancer initiating cells. Nevertheless, there have been no research that reported the activity of ATRA against osteosarcoma initiating cells. In this research, we hereby examined the potential activity of ATRA in osteosarcoma initiating cells, and developed lipid-polymer nanoparticles with CD133 aptamers for targeted ATRA delivery to osteosarcoma initiating cells. Using the cytotoxicity assay, colony formation assay, tumorsphere formation assay and flow cytometry, the therapeutic effect of ATRA and ATRA-loaded lipid-polymer nanoparticles conjugated with CD133 aptamers (ATRA-PLNP-CD133) against osteosarcoma initiating cells were investigated. The results showed that ATRA exerted potent activity towards osteosarcoma initiating cells. ATRA-PLNP-CD133, which showed a size of 129.9 nm and a sustained release of ATRA during 144 h, was demonstrated to efficiently and specifically promote the ATRA delivery to osteosarcoma initiating cells, and achieve superior therapeutic efficacy in osteosarcoma compared with ATRA and non-targeted nanoparticles. This is the first report of the therapeutic efficacy of ATRA towards osteosarcoma initiating cells, and the increased ATRA delivery by nanoparticles to osteosarcoma initiating cells using CD133 aptamers. ATRA-PLNP-CD133 represent an up-and coming approach for the therapy of osteosarcoma initiating cells.

Codelivery of doxorubicin and elacridar to target both liver cancer cells and stem cells by polylactide-co-glycolide/d-alpha-tocopherol polyethylene glycol 1000 succinate nanoparticles

Purpose

Liver cancer is the third leading cause of cancer-related deaths worldwide. Liver cancer stem cells (LCSCs) are a subpopulation of cancer cells that are responsible for the initiation, progression, drug resistance, recurrence, and metastasis of liver cancer. Recent studies have suggested that the eradication of both LCSCs and liver cancer cells is necessary because the conversion of cancer stem cells (CSCs) to cancer cells occasionally occurs. As ATP-binding cassette (ABC) transporters are overexpressed in both CSCs and cancer cells, combined therapies using ABC transporter inhibitors and chemotherapy drugs could show superior therapeutic efficacy in liver cancer. In this study, we developed poly(lactide-co-glycolide)/d-alpha-tocopherol polyethylene glycol 1000 succinate nanoparticles to accomplish the simultaneous delivery of an optimized ratio of doxorubicin (DOX) and elacridar (ELC) to target both LCSCs and liver cancer cells.

Methods

Median-effect analysis was used for screening of DOX and ELC for synergy in liver cancer cells (HepG2 cells) and LCSCs (HepG2 tumor sphere [HepG2-TS]). Then, nanoparticles loaded with DOX and ELC at the optimized ratio (NDEs) were prepared by nanoprecipitation method. The cytotoxicity and colony and tumor sphere formation ability of nanoparticles were investigated in vitro, and the tissue distribution and antitumor activity of nanoparticles were evaluated in vivo.

Results

We demonstrated that a DOX/ELC molar ratio of 1:1 was synergistic in HepG2 cells and HepG2-TS. NDEs were shown to exhibit significantly increased cytotoxic effects against both HepG2 and HepG2-TS compared with DOX-loaded nanoparticles (NDs) or ELC-loaded nanoparticles (NEs) in vitro. In vivo studies demonstrated that the nanoparticles exhibited better tumor targeting, with NDE showing the strongest antitumor activity with lower systemic toxicity.

Conclusion

These results suggested that NDE represented a promising combination therapy against liver cancer by targeting both liver cancer cells and CSCs.

All-trans retinoic acid-encapsulated, CD20 antibody-conjugated poly(lactic-co-glycolic acid) nanoparticles effectively target and eliminate melanoma-initiating cells in vitro

Purpose

Melanoma, which is initiated from melanocytes, is the most fatal type of skin cancer. Melanoma-initiating cells significantly contribute to the initiation, metastasis, and recurrence of melanoma, and CD20 is a marker of melanoma-initiating cells. All-trans retinoic acid (ATRA) has been demonstrated to induce differentiation, inhibit proliferation, and promote the apoptosis of cancer cells and cancer-initiating cells (CICs). However, there has been no report on ATRA activity against melanoma-initiating cells. In this study, we examined the activity of ATRA against melanoma-initiating cells and developed ATRA-encapsulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles, which were conjugated with a CD20 antibody (ATRA-PNP-CD20) for targeted delivery of ATRA to CD20⁺ melanoma-initiating cells.

Materials and methods

The effects of ATRA and ATRA-PNP-CD20 against melanoma-initiating cells were investigated using a cytotoxicity assay, tumorsphere formation assay, and flow cytometry.

Results

ATRA-PNP-CD20 had a size of 126.9 nm and a negative zeta potential. The drug-loading capacity of ATRA-PNP-CD20 was 8.7%, and ATRA-PNP-CD20 displayed a sustained release of ATRA for 144 hours. The results showed that ATRA-PNP-CD20 could effectively and specifically deliver ATRA to CD20⁺ melanoma-initiating cells, achieving superior inhibitory effects against CD20⁺ melanoma-initiating cells compared with those of free ATRA and nontargeted nanoparticles. To the best of our knowledge, we report for the first time a potent activity of ATRA against CD20⁺ melanoma-initiating cells, targeted drug delivery of ATRA via nanoparticles to melanoma-initiating cells, and the achievement of a superior inhibitory effect against melanoma-initiating cells by using a CD20 antibody.

Conclusion

ATRA-PNP-CD20 represents a promising tool for eliminating melanoma-initiating cells and shows a potential for the therapy of melanoma.

The enhanced delivery of salinomycin to CD133+ ovarian cancer stem cells through CD133 antibody conjugation with poly(lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles

Ovarian cancer is the most lethal gynecologic malignancy, and ovarian cancer stem cells (CSCs) serve a pivotal function in the metastasis and recurrence of ovarian cancer. Multiple previous studies have validated CD133 as a marker of ovarian CSCs. Although salinomycin is a promising therapeutic agent that has been demonstrated to kill CSCs in various types of cancer, poor aqueous solubility hampers its clinical application. The present study used salinomycin-loaded poly(lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles conjugated with CD133 antibodies (CD133-SAL-NP) to eliminate CD133⁺ ovarian CSCs. The results revealed that CD133-SAL-NPs were of an appropriate size (149.2 nm) and exhibited sustained drug release. CD133-SAL-NPs efficiently bound to CD133⁺ ovarian cancer cells, resulting in an increased cytotoxic effect in CD133⁺ ovarian cancer cells, compared with the untargeted SAL-NPs and salinomycin. CD133-SAL-NPs reduced the percentage of CD133⁺ ovarian CSCs in ovarian cells more effectively than treatment with salinomycin or SAL-NPs, suggesting that CD133-SAL-NP targeted CD133⁺ ovarian CSCs. In nude mice bearing ovarian cancer xenografts, CD133-SAL-NPs exerted improved therapeutic effects compared with SAL-NPs and salinomycin. Thus, CD133 was demonstrated to be a promising target for drug delivery to ovarian CSCs, and may be useful as an agent to inhibit the growth of ovarian cancer by targeting CD133⁺ ovarian CSCs. CD133-SAL-NPs may therefore represent a promising approach for the treatment of ovarian cancer.

Salinomycin-loaded lipid-polymer nanoparticles with anti-CD20 aptamers selectively suppress human CD20+ melanoma stem cells

Melanoma is the deadliest type of skin cancer. CD20+ melanoma stem cells (CSCs) are pivotal for metastasis and initiation of melanoma. Therefore, selective elimination of CD20+ melanoma CSCs represents an effective treatment to eradicate melanoma. Salinomycin has emerged as an effective drug toward various CSCs. Due to its poor solubility, its therapeutic efficacy against melanoma CSCs has never been evaluated. In order to target CD20+ melanoma CSCs, we designed salinomycin-loaded lipid-polymer nanoparticles with anti-CD20 aptamers (CD20-SA-NPs). Using a single-step nanoprecipitation method, salinomycin-loaded lipid-polymer nanoparticles (SA-NPs) were prepared, then CD20-SA-NPs were obtained through conjugation of thiolated anti-CD20 aptamers to SA-NPs via a maleimide-thiol reaction. CD20-SA-NPs displayed a small size of 96.3 nm, encapsulation efficiency higher than 60% and sustained drug release ability. The uptake of CD20-SA-NPs by CD20+ melanoma CSCs was significantly higher than that of SA-NPs and salinomycin, leading to greatly enhanced cytotoxic effects in vitro, thus the IC₅₀ values of CD20-SA-NPs were reduced to 5.7 and 2.6 μg/mL in A375 CD+20 cells and WM266-4 CD+ cells, respectively. CD20-SA-NPs showed a selective cytotoxicity toward CD20+ melanoma CSCs, as evidenced by the best therapeutic efficacy in suppressing the formation of tumor spheres and the proportion of CD20+ cells in melanoma cell lines. In mice bearing melanoma xenografts, administration of CD20-SA-NPs (salinomycin 5 mg·kg^-1·d^-1, iv, for 60 d) showed a superior efficacy in inhibition of melanoma growth compared with SA-NPs and salinomycin. In conclusion, CD20 is a superior target for delivering drugs to melanoma CSCs. CD20-SA-NPs display effective delivery of salinomycin to CD20+ melanoma CSCs and represent a promising treatment for melanoma.

Epidermal growth factor receptor aptamer-conjugated polymer-lipid hybrid nanoparticles enhance salinomycin delivery to osteosarcoma and cancer stem cells

Osteosarcoma is a common childhood bone cancer with a poor survival rate. Osteosarcoma cancer stem cells (CSCs) contribute to the recurrence, drug resistance and metastasis of this disease. Previous evidence suggested that cancer cells are able to spontaneously turn into CSCs, thus it is crucial to simultaneously target osteosarcoma cells and CSCs. Our previous studies have demonstrated that salinomycin preferably eliminated osteosarcoma CSCs. In addition, amplification of the epidermal growth factor receptor (EGFR) is a common genetic aberration in osteosarcoma, and thus EGFR is a promising target in osteosarcoma. The present study aimed to develop EGFR aptamer-conjugated salinomycin-loaded polymer-lipid hybrid nanoparticles (EGFR-SNPs) to target both osteosarcoma cells and CSCs. The results revealed that EGFR was overexpressed in these cells, and that EGFR-SNPs possessed a small size of 95 nm, suitable drug encapsulation efficiency (63%) and sustained drug release over 120 h. EGFR-SNPs targeted EGFR-overexpressing osteosarcoma cells and CSCs, resulting in an enhanced cytotoxic effect compared with non-targeted SNPs and salinomycin. Notably, EGFR-SNPs was able to reduce the osteosarcoma tumorsphere formation rate and proportion of CD133⁺ osteosarcoma CSCs in the osteosarcoma cell lines more effectively compared with SNPs and salinomycin, suggesting that EGFR-SNPs effectively reduced the proportion of osteosarcoma CSCs. In conclusion, the interaction of EGFR aptamers and EGFR is a potential approach to promote the effective delivery of salinomycin to osteosarcoma. The study results suggested that EGFR-SNPs represents a promising approach to target osteosarcoma cells and CSCs.

The combination therapy of salinomycin and gefitinib using poly(d,l-lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles for targeting both lung cancer stem cells and cancer cells

Purpose

Lung cancer (LC) is the leading cause of cancer death worldwide. Evidences suggest that both LC cancer stem cells (CSCs) and cancer cells are supposed to be eliminated to achieve superior treatment effect against LC. Salinomycin could eradiate CSCs in various types of cancers, and gefitinib is a first-line therapy in LC. The purpose of the present study was to develop salinomycin-loaded nanoparticles (salinomycin-NPs) combined with gefitinib-loaded nanoparticles (gefitinib-NPs) to eradicate both LC CSCs and cancer cells.

Methods

Salinomycin and gefitinib were encapsulated separately by poly(d,l-lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles by the emulsion/solvent evaporation approach. The anti-LC activity of salinomycin-NPs and gefitinib-NPs was investigated.

Results

Salinomycin-NPs and gefitinib-NPs are of ~140 nm in size, high drug encapsulation efficacy and sustained release of drugs. CD133⁺ LC CSCs showed the characteristics of CSCs, including significantly enhanced stem cell gene expression, tumorsphere formation ability, and tumorigenicity in mice. Both salinomycin and salinomycin-NPs are capable of selectively inhibiting LC CSCs, as reflected by their enhanced cytotoxic effects toward CD133⁺ LC CSCs and ability to reduce tumorsphere formation in LC cell lines, whereas gefitinib and gefitinib-NPs could significantly inhibit LC cells. Salinomycin-NPs and salinomycin could reduce the population of LC CSCs in the tumors in vivo. It is noteworthy that salinomycin-NPs combined with gefitinib-NPs inhibited the growth of tumors more efficiently compared with salinomycin combined with gefitinib or single salinomycin-NPs or gefitinib-NPs.

Conclusion

Salinomycin-NPs combined with gefitinib-NPs represent a potential approach for LC by inhibiting both LC CSCs and cancer cells.

Targeted inhibition of human hematological cancers in vivo by doxorubicin encapsulated in smart lipoic acid-crosslinked hyaluronic acid nanoparticles

The chemotherapy of hematological cancers is challenged by its poor selectivity that leads to low therapeutic efficacy and pronounced adverse effects. Here, we report that doxorubicin encapsulated in lipoic acid-crosslinked hyaluronic acid nanoparticles (LACHA-DOX) mediate highly efficacious and targeted inhibition of human hematological cancers including LP-1 human multiple myeloma (MM) and AML-2 human acute myeloid leukemia xenografted in nude mice. LACHA-DOX had a size of ca. 183 nm and a DOX loading content of ca. 12.0 wt.%. MTT and flow cytometry assays showed that LACHA-DOX possessed a high targetability and antitumor activity toward CD44 receptor overexpressing LP-1 human MM cells and AML-2 human acute myeloid leukemia cells. The in vivo and ex vivo images revealed that LACHA-DOX achieved a significantly enhanced accumulation in LP-1 and AML-2 tumor xenografts. Notably, LACHA-DOX effectively suppressed LP-1 as well as AML-2 tumor growth and drastically increased mice survival rate as compared to control groups receiving free DOX or PBS. Histological analyses exhibited that LACHA-DOX caused little damage to the major organs like liver and heart. This study provides a proof-of-concept that lipoic acid-crosslinked hyaluronic acid nanoparticulate drugs may offer a more safe and effective treatment modality for CD44 positive hematological malignancies.

Concentration-dependent protein adsorption at the nano-bio interfaces of polymeric nanoparticles and serum proteins

AIM

A comprehensive understanding of nanoparticle (NP)-protein interaction (protein corona formation) is required. So far, many factors influencing this interaction have been investigated, like size and ζ potential. However, NPs exposure concentration has always been ignored. Herein, we aim to disclose the correlation of NPs exposure concentration with protein adsorption.

MATERIALS & METHODS

Four polymeric NPs systems possessing similar sizes (230 ± 20 nm) but varied ζ potentials (-30 ∼ +40 mv) were prepared. Physicochemical properties and protein adsorption upon NP-protein interaction were characterized.

RESULTS

Protein adsorption capacity and adsorbed protein types were NPs concentration-dependent.

CONCLUSION

Considering the critical impacts of protein adsorption on NPs delivery, our work could be an urgent warning about the possible risks of dosage adjustment of nanoformulations.

PLGA nanoparticles with CD133 aptamers for targeted delivery and sustained release of propranolol to hemangioma

AIM

To develop propranolol-loaded poly(lactic-co-glycolic acid) nanoparticle with CD133 aptamers (PPN-CD133) to treat infantile hemangioma.

MATERIALS & METHODS

The antihemangioma activity and mechanism of PPN-CD133 were evaluated.

RESULTS & CONCLUSION

PPN-CD133 are of desired size (143.7 nm), drug encapsulation efficiency (51.8%) and sustained drug release for 8 days. PPN-CD133 could effectively bind to CD133⁺ hemangioma stem cells, resulting in enhanced cytotoxic effect and reduced expression of angiogenesis factors in hemangioma stem cells. The therapeutic effect of PPN-CD133 in hemangioma was superior to that of untargeted PPN and propranolol in vivo, as reflected by reduced hemangioma volume, weight and microvessel density. PPN-CD133 represents a very promising approach to locally and efficiently deliver propranolol leading to significant inhibition of infantile hemangioma.

Polymer-lipid hybrid anti-HER2 nanoparticles for targeted salinomycin delivery to HER2-positive breast cancer stem cells and cancer cells

PURPOSE

Breast cancer stem cells (CSCs) are responsible for the initiation, recurrence, and metastasis of breast cancer. Sufficient evidence has established that breast cancer cells can spontaneously turn into breast CSCs. Thus, it is essential to simultaneously target breast CSCs and cancer cells to maximize the efficacy of breast cancer therapy. HER2 has been found to be overexpressed in both breast CSCs and cancer cells. We developed salinomycin-loaded polymer-lipid hybrid anti-HER2 nanoparticles (Sali-NP-HER2) to target both HER2-positive breast CSCs and cancer cells.

METHODS

The antitumor activity of Sali-NP-HER2 constructed by conjugating anti-HER2 antibodies to polymer-lipid salinomycin nanoparticles was evaluated in vitro and in vivo.

RESULTS

Sali-NP-HER2 efficiently bound to HER2-positive breast CSCs and cancer cells, resulting in enhanced cytotoxic effects compared with non-targeted nanoparticles or salinomycin. In mice bearing breast cancer xenografts, administration of Sali-NP-HER2 exhibited superior efficacy in inhibiting tumor growth. Sali-NP-HER2 reduced the breast tumorsphere formation rate and the proportion of breast CSCs more effectively than non-targeted nanoparticles or salinomycin alone.

CONCLUSION

Sali-NP-HER2 represents a promising approach in treating HER2-positive breast cancer by targeting both breast CSCs and cancer cells.

Gefitinib-loaded DSPE-PEG2000 nanomicelles with CD133 aptamers target lung cancer stem cells

Background

Lung cancer stem cells (CSCs) are considered to be the seed of lung cancer, and CD133 is a marker of lung CSCs. Here, we developed gefitinib-loaded poly(ethylene glycol) 2000-distearoylphosphatidylethanolamine nanomicelles with CD133 aptamers (M-Gef-CD133) to eliminate CD133⁺ lung CSCs.

Methods

M-Gef-CD133 was prepared using a lipid-film-based approach. The targeting and activity of M-Gef-CD133 towards lung CSCs were evaluated.

Results

M-Gef-CD133 were small (25 nm) and showed enhanced cytotoxic effect towards CD133⁺ lung CSCs compared with non-targeted M-Gef and gefitinib. Notably, M-Gef-CD133 could significantly reduce tumor sphere formation and the percentage of CD133⁺ lung CSCs, indicating that it possesses selective toxicity against CD133⁺ lung CSCs.

Conclusions

The interaction of CD133 aptamers and CD133 shows promise in the delivery of gefitinib to CD133⁺ lung CSCs, and M-Gef-CD133 represents a promising treatment to target lung CSCs.

Selective Therapeutic Intervention: A Challenge against Off-Target Effects

Despite the massive global spend on biology-driven drug discovery, tackling the issue of side effects and adverse events resulting from drug promiscuity represents a persistent challenge. Although delivering authentic medical innovations today is more complex than ever, minimization of off-target effects should be a priority.