Cheng-Qiong Mao

Tailor-Made Dual pH-Sensitive Polymer–Doxorubicin Nanoparticles for Efficient Anticancer Drug Delivery

Efficient delivery of therapeutics into tumor cells to increase the intracellular drug concentration is a major challenge for cancer therapy due to drug resistance and inefficient cellular uptake. Herein, we have designed a tailor-made dual pH-sensitive polymer-drug conjugate nanoparticulate system to overcome the challenges. The nanoparticle is capable of reversing its surface charge from negative to positive at tumor extracellular pH (∼6.8) to facilitate cell internalization. Subsequently, the significantly increased acidity in subcellular compartments such as the endosome (∼5.0) further promotes doxorubicin release from the endocytosed drug carriers. This dual pH-sensitive nanoparticle has showed enhanced cytotoxicity in drug-resistant cancer stem cells, indicating its great potential for cancer therapy.

Surface charge switchable nanoparticles based on zwitterionic polymer for enhanced drug delivery to tumor.

Two faced nanoparticles: A zwitterionic polymer-based nanoparticle with response to tumor acidity is developed for enhanced drug delivery to tumors. The nanoparticles are neutrally charged at physiological conditions and show prolonged circulation time; after leaking into tumor sites, in the acidic extracellular tumor environment (pH(e) ), nanoparticles are activated and become positively charged and are therefore efficiently taken up by tumor cells, leading to enhanced therapeutic effects in cancer treatment.

Sheddable Ternary Nanoparticles for Tumor Acidity-Targeted siRNA Delivery

Drug delivery systems for cancer therapy usually need to be sterically stabilized by a poly(ethylene glycol) (PEG) layer during blood circulation to minimize nonspecific interactions with serum components. However, PEGylation significantly reduces cellular uptake of the delivery systems after they accumulate at the tumor site, which markedly impairs the in vivo antitumor efficiency. Here, we develop a ternary small interfering RNA (siRNA) delivery system with tumor acidity-activated sheddable PEG layer to overcome the challenge. The sheddable nanoparticle is fabricated by introducing a tumor acidity-responsive PEGylated anionic polymer to the surface of positively charged polycation/siRNA complexes via electrostatic interaction. We show clear evidence that introducing the PEGylated anionic polymer to the surface of a nanoparticle markedly reduces its nonspecific interactions with protein. We further demonstrate that the nanoparticle is capable of deshielding the PEG layer at the slightly acidic tumor extracellular microenvironment to facilitate the delivery of siRNA to the tumor cells after accumulation at the tumor site. Accordingly, this promotes the RNA-interfering efficiencies and enhances the inhibition of tumor growth. Such delivery system with the ability to deshield the PEG layer at the target tissues has remarkable potential in cancer therapy.

Systemic delivery of siRNA with cationic lipid assisted PEG-PLA nanoparticles for cancer therapy.

Delivery of small interfering RNA (siRNA) has been one of the major hurdles for the application of RNA interference in therapeutics. Here, we describe a cationic lipid assisted polymeric nanoparticle system with stealthy property for efficient siRNA encapsulation and delivery, which was fabricated with poly(ethylene glycol)-b-poly(d,l-lactide), siRNA and a cationic lipid, using a double emulsion-solvent evaporation technique. By incorporation of the cationic lipid, the encapsulation efficiency of siRNA into the nanoparticles could be above 90% and the siRNA loading weight ratio was up to 4.47%, while the diameter of the nanoparticles was around 170 to 200nm. The siRNA retained its integrity within the nanoparticles, which were effectively internalized by cancer cells and escaped from the endosome, resulting in significant gene knockdown. This effect was demonstrated by significant down-regulation of luciferase expression in HepG2-luciferase cells which stably express luciferase, and suppression of polo-like kinase 1 (Plk1) expression in HepG2 cells, following delivery of specific siRNAs by the nanoparticles. Furthermore, the nanoparticles carrying siRNA targeting the Plk1 gene were found to induce remarkable apoptosis in both HepG2 and MDA-MB-435s cancer cells. Systemic delivery of specific siRNA by nanoparticles significantly inhibited luciferase expression in an orthotopic murine liver cancer model and suppressed tumor growth in a MDA-MB-435s murine xenograft model, suggesting its therapeutic promise in disease treatment.

Combating the Drug Resistance of Cisplatin Using a Platinum Prodrug Based Delivery System

Platinum-based anticancer drugs are widely used in the clinic for the treatment of a broad spectrum of human malignancies. These drugs are administered to 40–80% of all patients undergoing cancer chemotherapy, either as single agents or in combination with other agents. However, their application is limited by the presence of side effects and drug resistance. Although some tumors are intrinsically resistant to platinumbased drugs, other tumors acquire resistance only after initial treatment. The sensitivity of cells toward platinum-based drugs, such as cisplatin, is dependent on DNA platination because DNA is the ultimate drug target of cisplatin. Tumor cells can acquire cisplatin resistance, that is, can achieve a reduction in the level of DNA platination, through several mechanisms, for example, through reduced drug uptake, through drug deactivation in cells, through DNA repair, and through increased drug efflux. Several cellular processes can be associated with sensitivity of cells toward cisplatin. The uptake of cisplatin into cells is facilitated by the copper transport protein (Ctr1), which is expressed in low levels in some cisplatin-resistant cells. Metallothionein (MT) is a thiol-rich protein that binds strongly to many heavy-metal ions, including platinum(II). MT plays a role in cellular detoxification by sequestering these heavy-metal compounds, and an increased concentration of this protein in cells is associated with low efficacy of cisplatin. The small peptide glutathione (GSH), which also has high affinity toward cisplatin and is found in increased concentrations in some cisplatin-resistant cells, can play a similar role. Additionally, DNA repair proteins (such as NER) and efflux proteins (such as P-type ATPases) can also reduce the efficacy of cisplatin and contribute to cisplatin resistance. To avoid the problems of resistance associated with the use of cisplatin, several types of nonclassical platinum complexes have been developed, including trans-coordinated complexes, polynuclear platinum complexes, and platinum(IV) complexes. These platinum complexes differ from cisplatin in their uptake pathway, their reactivity toward cellular proteins, and their DNA binding modes. Because of these differences, some of these nonclassical platinum complexes, such as trans-EE, BBR3464, and satraplatin, have shown promising activity in cisplatin-resistant cells. These findings suggest that the design of platinum-based drugs that have different responses to cellular processes is a feasible approach toward circumventing the problems of resistance that affect the use of cisplatin. Drug delivery systems have drawn particular attention in recent years because they can facilitate the delivery of platinum-based drugs, thus enhancing drug efficacy. A number of drug delivery systems have been developed for the delivery of platinum-based drugs. These systems have been based on polymers, solid lipids, and inorganic nanoparticles; the latter can be further subdivided into magnetic iron oxide, single-walled carbon nanotubes, metallofullerene nanoparticles, gold nanoparticles, nanoscale metal-organic frameworks, and mesoporous silica microparticles. [17] Some of these systems have entered clinical trials. With the conjugation of biologically active molecules, some delivery systems have shown high selectivity in targeting tumor cells. Although the use of drug-delivery systems has been successful in improving the efficacy of platinum-based drugs, it remains a challenge to develop drug conjugates that combat drug resistances. We have previously reported that PEGylated gold nanorods (PEG-GNRs) can facilitate the delivery of platinum(IV) prodrugs and significantly enhance the cytotoxicity of these prodrugs in tumor cells. Herein, we report that the use of this drug-delivery system avoids the drug resistance that affects the use of cisplatin. We show that impaired drug uptake that results from the low expression of Ctr1 in the cisplatin-resistant cells A549R can be overcome by using a conjugate of a cisplatin prodrug and PEGylated gold nanorods (Pt-PEG-GNRs conjugate); this conjugate facilitates the delivery of the platinum-based drug into cells through endocytosis. Additionally, the platinum(IV) prodrug is less susceptible to deactivation by the detoxification protein MT and the peptide GSH, which were found in high concentrations in A549R cells. Consequently, the Pt-PEGGNRs conjugate was highly cytotoxic to tumor cells, especially cisplatin-resistant cells. [*] Y. Min, S. Chen, G. Ma, Prof. Y. Liu CAS Key Laboratory of Soft Matter Chemistry and Department of Chemistry University of Science and Technology of China Hefei, Anhui, 230026 (China) E-mail: liuyz@ustc.edu.cn

Targeted delivery of PLK1-siRNA by ScFv suppresses Her2 + breast cancer growth and metastasis

Antibody-mediated delivery of anticancer siRNAs suppresses Her2+ breast cancer growth and metastasis. A Bull’s-Eye for Breast Cancer The goal in archery is to hit the center of the target. Although this could be accomplished by randomly shooting a barrage of arrows, it would be more efficient—and less likely to provoke emergency room visits—to aim straight at the bull’s-eye. Cancer therapies work on a similar principle. Broad therapies may treat the cancer but have many unwanted effects on healthy tissue. Yao et al. now target cancer drugs directly to the tumor using single-chain fragmented antibodies (ScFvs). About 60% of metastatic breast cancers that express human epidermal growth factor receptor 2 (Her2) do not respond to the anti-Her2 therapeutic antibody trastuzumab. The authors hypothesized that ScFvs specific to Her2 could deliver small interfering RNA (siRNA) to Her2+ breast cancer cells. They complexed siRNA for Polo-like kinase 1 (PLK1), which promotes cell division, with a Her2-ScFv-protamine peptide fusion protein (F5-P). This complex suppressed Her2+ breast cancer cell lines and primary human cancers in orthotopic breast cancer models. The siRNA complexes slowed tumor cell growth, reduced metastasis, and prolonged survival with no observed toxicity. The antitumor effects were even greater when a mix of siRNAs was delivered. These results suggest that as a new platform to deliver siRNAs to specifically treat Her2+ breast cancers, F5-P may be on target. A major obstacle to developing small interfering RNAs (siRNAs) as cancer drugs is their intracellular delivery to disseminated cancer cells. Fusion proteins of single-chain fragmented antibodies (ScFvs) and positively charged peptides deliver siRNAs into specific target cells. However, the therapeutic potential of ScFv-mediated siRNA delivery has not been evaluated in cancer. Here, we tested whether Polo-like kinase 1 (PLK1) siRNAs complexed with a Her2-ScFv-protamine peptide fusion protein (F5-P) could suppress Her2+ breast cancer cell lines and primary human cancers in orthotopic breast cancer models. PLK1-siRNAs transferred by F5-P inhibited target gene expression, reduced proliferation, and induced apoptosis of Her2+ breast cancer cell lines and primary human cancer cells in vitro without triggering an interferon response. Intravenously injected F5-P/PLK1-siRNA complexes concentrated in orthotopic Her2+ breast cancer xenografts and persisted for at least 72 hours, leading to suppressed PLK1 gene expression and tumor cell apoptosis. The intravenously injected siRNA complexes retarded Her2+ breast tumor growth, reduced metastasis, and prolonged survival without evident toxicity. F5-P–mediated delivery of a cocktail of PLK1, CCND1, and AKT siRNAs was more effective than an equivalent dose of PLK1-siRNAs alone. These data suggest that F5-P could be used to deliver siRNAs to treat Her2+ breast cancer.

A biodegradable amphiphilic and cationic triblock copolymer for the delivery of siRNA targeting the acid ceramidase gene for cancer therapy

One of the key challenges in the development of RNA interference-based cancer therapy is the lack of an efficient delivery system for synthetic small interfering RNAs (siRNAs) that would enable efficient uptake by tumor cells and allow for significant knockdown of a target transcript in vivo. Here, we describe a micelleplex system based on an amphiphilic and cationic triblock copolymer, which can systemically deliver siRNA targeting the acid ceramidase (AC) gene for cancer therapy. This triblock copolymer, consisting of monomethoxy poly(ethylene glycol), poly(ε-caprolactone) and poly(2-aminoethyl ethylene phosphate), self-assembles into micellar nanoparticles (MNPs) in aqueous solution with an average diameter of 60 nm and a zeta potential of approximately 48 mV. The resulting micelleplex, formed by the interaction of MNPs and siRNA, was effectively internalized by BT474 breast cancer cells and siRNA was subsequently released, resulting in significant gene knockdown. This effect was demonstrated by significant down-regulation of luciferase expression in BT474-luciferase cells which stably express luciferase, and suppression of AC expression in BT474 cells at both the transcriptional and protein level, following delivery of specific siRNAs by the micelleplex. Furthermore, a micelleplex carrying siRNA targeting the AC (micelleplex(siAC)) gene was found to induce remarkable apoptosis and reduce the proliferation of cancer cells. Systemic delivery of micelleplex(siAC) significantly inhibited tumor growth in a BT474 xenograft murine model, with depressed expression of AC and no positive activation of the innate immune response, suggesting therapeutic promise for micelleplex siRNA delivery in cancer therapy.

Single-step assembly of cationic lipid-polymer hybrid nanoparticles for systemic delivery of siRNA.

The clinical success of therapeutics of small interfering RNA (siRNA) is still hindered by its delivery systems. Cationic polymer or lipid-based vehicles as the major delivery systems of siRNA cannot sufficiently satisfy siRNA therapeutic applications. It is hypothesized that cationic lipid-polymer hybrid nanoparticles may take advantage of both polymeric and lipid-based nanoparticles for siRNA delivery, while diminishing the shortcomings of both. In this study, cationic lipid-polymer hybrid nanoparticles were prepared by a single-step nanoprecipitation of a cationic lipid (N,N-bis(2-hydroxyethyl)-N-methyl-N-(2-cholesteryloxycarbonyl aminoethyl) ammonium bromide, BHEM-Chol) and amphiphilic polymers for systemic delivery of siRNA. The formed hybrid nanoparticles comprised a hydrophobic polylactide core, a hydrophilic poly(ethylene glycol) shell, and a cationic lipid monolayer at the interface of the core and the shell. Such hybrid nanoparticles exhibited excellent stability in serum and showed significantly improved biocompatibility compared to that of pure BHEM-Chol particles. The hybrid nanoparticles were capable of delivering siRNA into BT474 cells and facilitated the escape of loaded siRNA from the endosome into the cytoplasm. The hybrid nanoparticles carrying polo-like kinase 1 (Plk1)-specific siRNA (siPlk1) remarkably and specifically downregulated expression of the oncogene Plk1 and induced cancer cell apoptosis both in vitro and in vivo and significantly suppressed tumor growth following systemic administration. We demonstrate that this system is stable, nontoxic, highly efficient, and easy to scale up, bringing the clinical application of siRNA therapy one important step closer to reality.

Cancer stem cell therapy using doxorubicin conjugated to gold nanoparticles via hydrazone bonds

Nanoparticle-mediated delivery of chemotherapies has demonstrated enhanced anti-cancer efficacy, mainly through the mechanisms of both passive and active targeting. Herein, we report other than these well-elucidated mechanisms, rationally designed nanoparticles can efficiently deliver drugs to cancer stem cells (CSCs), which in turn contributes significantly to the improved anti-cancer efficacy. We demonstrate that doxorubicin-tethered gold nanoparticles via a poly(ethylene glycol) spacer and an acid-labile hydrazone bond mediate potent doxorubicin delivery to breast CSCs, which reduces their mammosphere formation capacity and their cancer initiation activity, eliciting marked enhancement in tumor growth inhibition in murine models. The drug delivery mediated by the nanoparticles also markedly attenuates tumor growth during off-therapy stage by reducing breast CSCs in tumors, while the therapy with doxorubicin alone conversely evokes an enrichment of breast CSCs. Our findings suggest that with well-designed drug delivery system, the conventional chemotherapeutic agents are promising for cancer stem cell therapy.

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy.

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pHe) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pHe-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pHe-activated NPs, with special emphasis on pHe-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.