Multifunctional Magnetic Nanoplatform Eliminates Cancer Stem Cells via Inhibiting the Secretion of Extracellular Heat Shock Protein 90

Biomimetic liposome amplifying mitochondrial damage to potential cancer radio-immunotherapy

Radiotherapy, despite its precision and non-invasiveness, often fails due to the resistance of cancer stem cells (CSCs), which are characterized by high self-renewal capabilities and superior DNA repair mechanisms. These cells can evade RT and lead to tumor recurrence and metastasis. To address this challenge, a novel delivery system named PB has been introduced. This system combines liposomes with platelet membranes to encapsulate Bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl) ethyl sulfide (BPTES), thus enhancing its delivery and release specifically at tumor sites. In addition, this system not only targets CSCs effectively but also increases the local concentration of BPTES upon X-ray irradiation, which reduces glutathione levels in tumor cells, thereby increasing oxidative stress and damaging mitochondria. PB-elicited mitochondrial damage as the STING signal initiator, which mediated significant upregulation in the expression of a cGAS-STING pathway-related protein thereby amplifying the STING signal. Systemic intravenous administration of PB remarkably promoted DC maturation and CD8+ T cell infiltration, thus eliciting strong antitumor effects. Overall, this PB system presents a potent method to overcome CSC-related resistance and offers a promising approach for future cancer treatment protocols.

Surface Engineering of Magnetic Iron Oxide Nanoparticles for Breast Cancer Diagnostics and Drug Delivery

Data published in 2020 by the International Agency for Research on Cancer (IARC) of the World Health Organization show that breast cancer (BC) has become the most common cancer globally, affecting more than 2 million women each year. The complex tumor microenvironment, drug resistance, metastasis, and poor prognosis constitute the primary challenges in the current diagnosis and treatment of BC. Magnetic iron oxide nanoparticles (MIONPs) have emerged as a promising nanoplatform for diagnostic tumor imaging as well as therapeutic drug-targeted delivery due to their unique physicochemical properties. The extensive surface engineering has given rise to multifunctionalized MIONPs. In this review, the latest advancements in surface modification strategies of MIONPs over the past five years are summarized and categorized as constrast agents and drug delivery platforms. Additionally, the remaining challenges and future prospects of MIONPs-based targeted delivery are discussed.

Biomimetic Nano-Cancer Stem Cell Scavenger for Inhibition of Breast Cancer Recurrence and Metastasis after FLASH-Radiotherapy

Compared to conventional radiotherapy (RT), FLASH-RT delivers ultra-high dose radiation, significantly reducing damage to normal tissue while guaranteeing the effect of cancer treatment. However, cancer recurrence and metastasis frequently occur after all RT due to the existence of intractable cancer stem cells (CSCs). To address this, a biomimetic nanoplatform (named TAFL) of tumor-derived exosome fusion liposomes is designed by co-loading aggregation-induced emission photothermal agents, TPE-BBT, and anti-cancer drugs, aspirin, aiming to clear CSCs for inhibiting cancer recurrence and metastasis after FLASH-RT therapy . Aspirin released in TAFL system triggered by laser irradiation can induce apoptosis and DNA damage of 4T1 CSCs, comprehensively downregulate their stemness phenotype, and inhibit their sphericity. Furthermore, the TPE-BBT mediated mild-photothermal therapy can alleviate the hypoxic tumor microenvironment, inhibit the DNA repair of CSCs, which further amplifies the effect of aspirin against CSCs, therefore reduces the effective dose of aspirin, making TAFL more biologically safe. In vivo experimental results demonstrated that decreased CSCs population mediated by TAFL system treatment significantly inhibited tumor recurrence and metastasis after FLASH-RT therapy. In summary, this TAFL system   provides a new idea for the future clinical application of FLASH-RT therapy.

One-Minute Preparation of Iron Foam-Drug Implant for Ultralow-Power Magnetic Hyperthermia-Based Combination Therapy of Tumors in Vivo

The magnetic hyperthermia-based combination therapy (MHCT) is a powerful tumor treatment approach due to its unlimited tissue penetration depth and synergistic therapeutic effect. However, strong magnetic hyperthermia and facile drug loading are incompatible with current MHCT platforms. Herein, an iron foam (IF)-drug implant is established in an ultra-facile and universal way for ultralow-power MHCT of tumors in vivo for the first time. The IF-drug implant is fabricated by simply immersing IF in a drug solution at an adjustable concentration for 1 min. Continuous metal structure of IF enables ultra-high efficient magnetic hyperthermia based on eddy current thermal effect, and its porous feature provides great space for loading various hydrophilic and hydrophobic drugs via "capillary action". In addition, the IF has the merits of low cost, customizable size and shape, and good biocompatibility and biodegradability, benefiting reproducible and large-scale preparation of IF-drug implants for biological application. As a proof of concept, IF-doxorubicin (IF-DOX) is used for combined tumor treatment in vivo and achieves excellent therapeutic efficacy at a magnetic field intensity an order of magnitude lower than the threshold for biosafety application. The proposed IF-drug implant provides a handy and universal method for the fabrication of MHCT platforms for ultralow-power combination therapy.

An iron oxyhydroxide-based nanosystem sensitizes ferroptosis by a "Three-Pronged" strategy in breast cancer stem cells

The anti-apoptotic mechanism of breast cancer stem cells (BCSCs) makes it an obstacle to traditional apoptosis as the primary way of death. Ferroptosis is a recently reported mode of programmed cell death caused by the accumulation of iron-dependent lipid peroxidation (LPO) in cells. High dependence on iron makes BCSCs more sensitive to ferroptosis. However, the high level of the Prominin2 protein and high concentration of GSH in BCSCs make BCSCs able to efflux excess iron ions and clear LPO, which limits the therapeutic efficacy of ferroptosis in BCSCs. To overcome this obstacle, we designed a hyaluronic acid (HA)-coated siProminin2-loaded FeOOH nanoparticle (FeOOH/siPROM2@HA) to amplify ferroptosis. The FeOOH/siPROM2@HA is stable under physiologically neutral conditions but generates Fe³⁺ in an acidic microenvironment; meanwhile, the released siProminin2 inhibits its efflux, and then Fe³⁺ undergoes a redox reaction with endogenous GSH to produce Fe²⁺, which initiates the Fenton reaction-based ferroptosis by LPO elevation. Both in vitro and in vivo studies showed that these pH-sensitive NPs significantly inhibited tumor growth by downregulating glutathione peroxidase 4 (GPX4). Overall, this work demonstrates a "three-pronged" strategy for amplified ferroptotic therapy by simultaneously promoting intracellular iron, inhibiting iron efflux, and depleting GSH, which presents a potential strategy for CSC-targeted cancer therapy. STATEMENT OF SIGNIFICANCE: As the root of recurrence and metastasis, breast cancer stem cells (BCSCs) are resistant to traditional apoptotic death, so it is urgent to explore a new death mode for BCSCs. It has been reported that BCSCs are highly iron-dependent and, therefore, more sensitive to ferroptosis; however, the therapeutic efficacy is greatly limited by the overexpression of Prominin2 in BCSCs, which is correlated with resistance to ferroptosis by exocytosis of iron ions. In this work, we designed a hyaluronic acid-coated siProminin2-loaded FeOOH nano-drug (FeOOH/siPROM2@HA) to accelerate ferroptosis of BCSCs by simultaneously increasing iron ion content, inhibiting iron efflux, and scavenging GSH. This "three-pronged" strategy has significant implications for BCSC-targeted cancer therapy.

Targeting extracellular Hsp90: A unique frontier against cancer

The molecular chaperone Heat Shock Protein-90 (Hsp90) is known to interact with over 300 client proteins as well as regulatory factors (eg. nucleotide and proteins) that facilitate execution of its role as a chaperone and, ultimately, client protein activation. Hsp90 associates transiently with these molecular modulators during an eventful chaperone cycle, resulting in acquisition of flexible structural conformations, perfectly customized to the needs of each one of its client proteins. Due to the plethora and diverse nature of proteins it supports, the Hsp90 chaperone machinery is critical for normal cellular function particularly in response to stress. In diseases such as cancer, the Hsp90 chaperone machinery is hijacked for processes which encompass many of the hallmarks of cancer, including cell growth, survival, immune response evasion, migration, invasion, and angiogenesis. Elevated levels of extracellular Hsp90 (eHsp90) enhance tumorigenesis and the potential for metastasis. eHsp90 has been considered one of the new targets in the development of anti-cancer drugs as there are various stages of cancer progression where eHsp90 function could be targeted. Our limited understanding of the regulation of the eHsp90 chaperone machinery is a major drawback for designing successful Hsp90-targeted therapies, and more research is still warranted.

Advances of nanomedicines in breast cancer metastasis treatment targeting different metastatic stages

Breast cancer is the most common tumor in women, and the metastasis further increases the malignancy with extremely high mortality. However, there is almost no effective method in the clinic to completely inhibit breast cancer metastasis due to the dynamic multistep process with complex pathways and scattered occurring site. Nowadays, nanomedicines have been evidenced with great potential in treating cancer metastasis. In this review, we summarize the latest research advances of nanomedicines in anti-metastasis treatment. Strategies are categorized according to the metastasis dynamics, including primary tumor, circulating tumor cells, pre-metastatic niches and secondary tumor. In each different stage of metastasis process, nanomedicines are designed specifically with different functions. At the end of the review, we give our perspectives on current limitations and future directions in anti-metastasis therapy. We expect the review provides comprehensive understandings of anti-metastasis therapy for breast cancer, and boosts the clinical translation in the future to improve women's health.

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.

Molecular Chaperones in Cancer Stem Cells: Determinants of Stemness and Potential Targets for Antitumor Therapy

Cancer stem cells (CSCs) are a great challenge in the fight against cancer because these self-renewing tumorigenic cell fractions are thought to be responsible for metastasis dissemination and cases of tumor recurrence. In comparison with non-stem cancer cells, CSCs are known to be more resistant to chemotherapy, radiotherapy, and immunotherapy. Elucidation of mechanisms and factors that promote the emergence and existence of CSCs and their high resistance to cytotoxic treatments would help to develop effective CSC-targeting therapeutics. The present review is dedicated to the implication of molecular chaperones (protein regulators of polypeptide chain folding) in both the formation/maintenance of the CSC phenotype and cytoprotective machinery allowing CSCs to survive after drug or radiation exposure and evade immune attack. The major cellular chaperones, namely heat shock proteins (HSP90, HSP70, HSP40, HSP27), glucose-regulated proteins (GRP94, GRP78, GRP75), tumor necrosis factor receptor-associated protein 1 (TRAP1), peptidyl-prolyl isomerases, protein disulfide isomerases, calreticulin, and also a transcription heat shock factor 1 (HSF1) initiating HSP gene expression are here considered as determinants of the cancer cell stemness and potential targets for a therapeutic attack on CSCs. Various approaches and agents are discussed that may be used for inhibiting the chaperone-dependent development/manifestations of cancer cell stemness.

A nano-based thermotherapy for cancer stem cell-targeted therapy

Cancer stem cells (CSCs) exhibit high resistance to conventional therapy and are responsible for cancer metastasis and tumor relapse.