Overcoming Drug Resistance by Targeting Cancer Bioenergetics with an Activatable Prodrug

An activatable fluorescent prodrug of paclitaxel and BODIPY

A redox-activated paclitaxel prodrug (PTX-S-BDP) was synthesized. PTX-S-BDP NPs were fabricated by the coassembly of PTX-S-BDP with F-127, which can release PTX under redox conditions and exhibit superior cellular imaging and selectivity to cancer cells.

Red Light-Initiated Cross-Linking of NIR Probes to Cytoplasmic RNA: An Innovative Strategy for Prolonged Imaging and Unexpected Tumor Suppression

Improving the enrichment of drugs or theranostic agents within tumors is very vital to achieve effective cancer diagnosis and therapy while greatly reducing the dosage and damage to normal tissues. Herein, as a proof of concept, we for the first time report a red light-initiated probe-RNA cross-linking (RLIPRC) strategy that can not only robustly promote the accumulation and retention of the probe in the tumor for prolonged imaging but also significantly inhibits the tumor growth. A near-infrared (NIR) fluorescent probe f-CR consisting of a NIR dye (Cyanine 7) as a signal reporter, a cyclic-(arginine-glycine-aspartic acid) (cRGD) peptide for tumor targeting, and a singlet oxygen (¹O₂)-sensitive furan moiety for RNA cross-linking was rationally designed and synthesized. This probe possessed both passive and active tumor targeting abilities and emitted intense NIR/photoacoustic (PA) signals, allowing for specific and sensitive dual-modality imaging of tumors in vivo. Notably, probe f-CR could be specifically and covalently cross-linked to cytoplasmic RNAs via the cycloaddition reaction between furan and adenine, cytosine, or guanine under the oxidation of ¹O₂ generated in situ by irradiation of methylene blue (MB) with 660 nm laser light, which effectively blocks the exocytosis of the probes resulting in enhanced tumor accumulation and retention. More excitingly, for the first time, we revealed that the covalent cross-linking of probe f-CR to cytoplasmic RNAs could induce severe apoptosis of cancer cells leading to remarkable tumor suppression. This study thus represents the first red light-initiated RNA cross-linking system with high potential to improve the diagnostic and therapeutic outcomes of tumors in vivo.

Fused isoselenazolium salts suppress breast cancer cell growth by dramatic increase in pyruvate-dependent mitochondrial ROS production

The development of targeted drugs for the treatment of cancer remains an unmet medical need. This study was designed to investigate the mechanism underlying breast cancer cell growth suppression caused by fused isoselenazolium salts. The ability to suppress the proliferation of malignant and normal cells in vitro as well as the effect on NAD homeostasis (NAD⁺, NADH, and NMN levels), NAMPT inhibition and mitochondrial functionality were studied. The interactions of positively charged isoselenazolium salts with the negatively charged mitochondrial membrane model were assessed. Depending on the molecular structure, fused isoselenazolium salts display nanomolar to high micromolar cytotoxicities against MCF-7 and 4T1 breast tumor cell lines. The studied compounds altered NMN, NAD⁺, and NADH levels and the NAD⁺/NADH ratio. Mitochondrial functionality experiments showed that fused isoselenazolium salts inhibit pyruvate-dependent respiration but do not directly affect complex I of the electron transfer system. Moreover, the tested compounds induce an immediate dramatic increase in the production of reactive oxygen species. In addition, the isoselenazolothiazolium derivative selectively binds to cardiolipin in a liposomal model. Isoselenazolium salts may be a promising platform for the development of potent drug candidates for anticancer therapy that impact mitochondrial pyruvate-dependent metabolism in breast cancer cells.

Elucidating a Thermoresponsive Multimodal Photo-Chemotherapeutic Nanodelivery Vehicle to Overcome the Barriers of Doxorubicin Therapy

In an attempt to circumvent the major pitfalls associated with conventional chemotherapy including drug resistance and off-target toxicity, we have adopted a strategy to simultaneously target both mitochondrial DNA (Mt-DNA) and nuclear DNA (n-DNA) with the aid of a targeted theranostic nanodelivery vehicle (TTNDV). Herein, folic acid-anchored p-sulfo-calix[4]arene (SC₄)-capped hollow gold nanoparticles (HGNPs) were meticulously loaded with antineoplastic doxorubicin (Dox) and its mitochondrion-targeted analogue, Mt-Dox, in a pretuned ratio (1:100) for sustained thermoresponsive release of cargo. This therapeutic strategy was enabled to eradicate both n-DNA and Mt-DNA leaving no space to develop drug resistance. The SC₄-capped HGNPs (HGNPSC₄) were experimented for the first time as a photothermal (PTT) agent with 61.6% photothermal conversion efficiency, and they generated tunable localized heat more efficiently than bare HGNPs. Moreover, the cavity of SC₄ facilitated the formation of an inclusion complex with folic acid to target the folate receptor expressing cancer cells and imparted enhanced biocompatibility. The as-synthesized TTNDV was demonstrated to be an ideal substrate for surface-enhanced Raman scattering (SERS) to monitor the molecular-level therapeutic progression in cells and a spheroidal model. A significant reduction in the tumor mass with a marked survival benefit was achieved in syngraft murine models through this synergistic photo-chemotherapy. Collectively, this multifunctional nanoplatform offers a robust approach to treat cancer without any scope of generating Dox resistance and off-target toxicity.

PEGylated Bis-Quaternary Triphenyl-Phosphonium Tosylate Allows for Balanced Antibacterial Activity and Cytotoxicity

Quaternary triphenylphosphonium compounds (TPP⁺) have been widely recognized as an important antimicrobial because of their fast antimicrobial speed and broad antimicrobial spectrum. However, small-molecule TPP⁺ compounds have the defects of toxicity, which is the key factor that limits their practical applications. Here, two mono- and one bis-quaternary phosphonium tosylate compounds with different lengths of oligo(ethylene glycol) (OEG) chains and TPP⁺ as the active moiety were synthesized. Bis-TPP⁺ have a short OEG chain coupling two TPP⁺ at both ends, while mono-TPP⁺ attaches the OEG chain at one end in one molecule. In vitro antibacterial activities were evaluated against both Gram-positive as well as Gram-negative bacteria in terms of the inhibition zone (ZOI) and minimum inhibitory concentration (MIC). To investigate the antibacterial mechanism, β-galactosidase activity was monitored for measuring the degree of membrane permeability correlated to the abilities to disrupt the membranes of bacteria. Moreover, their structure-antibacterial activity and structure-cytotoxicity relationships were further analyzed. The results indicated that bis-TPP⁺ synthesized can reach the sterilization rate 90% or more against Escherichia coli and Staphylococcus aureus at MICs of 3.1 and 1.5 mg/mL, respectively, and meanwhile, the cell proliferation can reach more than 80%. This paper represents an excellent approach for development of bis-TPP⁺ bactericidal molecules that would achieve an optimal balance between antimicrobial activity and cytotoxicity.

Nano-Platelets as an Oxygen Regulator for Augmenting Starvation Therapy Against Hypoxic Tumor

The restriction of a tumor's energy supply is proven to be an effective means of treatment. Glucose oxidase (GOx), an enzyme that catalyzes the conversion of glucose to glucolactone, producing oxygen and hydrogen peroxide in the process, has proved useful in this regard. However, hypoxia, which is implicated in tumor growth, has been found to mediate resistance to this type of tumor starvation. Here, we describe the design and testing of a platelet membrane mimetic, PMS, consisting of mesoporous silica nanoparticles (MSNs) loaded with metformin (MET) as an inner layer and platelet membranes (PM) as an outer layer that inhibits oxygen consumption by the tumor cells' respiratory pathways and enhances the effectiveness of GOx. MET directly inhibits the activity of complex I in mitochondrial electron transport and is thus a potent inhibitor of cell respiration. PMS target tumor tissue effectively and, once internalized, MET can inhibit respiration. When oxygen is plentiful, GOx promotes glucose consumption, allowing amplification of its effects on tumor starvation. This combination of respiratory suppression by PMS and starvation therapy by GOx has been found to be effective in both targeting tumors and inhibiting their growth. It is hoped that this strategy will shed light on the development of next-generation tumor starvation treatments.

Pharmacological Targeting of Vacuolar H+-ATPase via Subunit V1G Combats Multidrug-Resistant Cancer

Multidrug resistance (MDR) in cancer remains a major challenge for the success of chemotherapy. Natural products have been a rich source for the discovery of drugs against MDR cancers. Here, we applied high-throughput cytotoxicity screening of an in-house natural product library against MDR SGC7901/VCR cells and identified that the cyclodepsipeptide verucopeptin demonstrated notable antitumor potency. Cytological profiling combined with click chemistry-based proteomics revealed that ATP6V1G directly interacted with verucopeptin. ATP6V1G, a subunit of the vacuolar H⁺-ATPase (v-ATPase) that has not been previously targeted, was essential for SGC7901/VCR cell growth. Verucopeptin exhibited strong inhibition of both v-ATPase activity and mTORC1 signaling, leading to substantial pharmacological efficacy against SGC7901/VCR cell proliferation and tumor growth in vivo. Our results demonstrate that targeting v-ATPase via its V1G subunit constitutes a unique approach for modulating v-ATPase and mTORC1 signaling with great potential for the development of therapeutics against MDR cancers.

Stimuli-responsive prodrug-based cancer nanomedicine

The rapid development of nanotechnology results in the emergence of nanomedicines, but the effective delivery of drugs to tumor sites remains a great challenge. Prodrug-based cancer nanomedicines thus emerged due to their unique advantages, including high drug load efficiency, reduced side effects, efficient targeting, and real-time controllability. A distinctive characteristic of prodrug-based nanomedicines is that they need to be activated by a stimulus or multi-stimulus to produce an anti-tumor effect. A better understanding of various responsive approaches could allow researchers to perceive the mechanism of prodrug-based nanomedicines effectively and further optimize their design strategy. In this review, we highlight the stimuli-responsive pathway of prodrug-based nanomedicines and their anticancer applications. Furthermore, various types of prodrug-based nanomedicines, recent progress and prospects of stimuli-responsive prodrug-based nanomedicines and patient data in the clinical application are also summarized. Additionally, the current development and future challenges of prodrug-based nanomedicines are discussed. We expect that this review will be valuable for readers to gain a deeper understanding of the structure and development of prodrug-based cancer nanomedicines to design rational and effective drugs for clinical use.

Stimulus-responsive surface-enhanced Raman scattering: a "Trojan horse" strategy for precision molecular diagnosis of cancer

Molecular diagnosis has played an increasingly important role in cancer detection. However, it remains challenging to develop an in situ analytical method capable of profiling the molecular phenotype of tumors for precision cancer diagnosis. A "Trojan horse" strategy based on stimulus-responsive surface-enhanced Raman scattering (SR-SERS) is reported here for selectively recording the comprehensive molecular information of tumors in situ, without resorting to destructive sample preparation and complex data analysis. This technique is employed to delineate the margin between tumors and normal tissues with high accuracy, and to further discriminate the molecular fingerprints of tumors in the early and late stages. Based on molecular profiling, we discovered that the signal ratios of fatty acid-to-phenylalanine could serve as promising indicators for identifying the primary tumors in different stages. This simple SR-SERS technique also provides a potential useful means for identifying tumor classifications or distinguishing primary and metastatic tumors.

Emerging insights of tumor heterogeneity and drug resistance mechanisms in lung cancer targeted therapy

The biggest hurdle to targeted cancer therapy is the inevitable emergence of drug resistance. Tumor cells employ different mechanisms to resist the targeting agent. Most commonly in EGFR-mutant non-small cell lung cancer, secondary resistance mutations on the target kinase domain emerge to diminish the binding affinity of first- and second-generation inhibitors. Other alternative resistance mechanisms include activating complementary bypass pathways and phenotypic transformation. Sequential monotherapies promise to temporarily address the problem of acquired drug resistance, but evidently are limited by the tumor cells' ability to adapt and evolve new resistance mechanisms to persist in the drug environment. Recent studies have nominated a model of drug resistance and tumor progression under targeted therapy as a result of a small subpopulation of cells being able to endure the drug (minimal residual disease cells) and eventually develop further mutations that allow them to regrow and become the dominant population in the therapy-resistant tumor. This subpopulation of cells appears to have developed through a subclonal event, resulting in driver mutations different from the driver mutation that is tumor-initiating in the most common ancestor. As such, an understanding of intratumoral heterogeneity-the driving force behind minimal residual disease-is vital for the identification of resistance drivers that results from branching evolution. Currently available methods allow for a more comprehensive and holistic analysis of tumor heterogeneity in that issues associated with spatial and temporal heterogeneity can now be properly addressed. This review provides some background regarding intratumoral heterogeneity and how it leads to incomplete molecular response to targeted therapies, and proposes the use of single-cell methods, sequential liquid biopsy, and multiregion sequencing to discover the link between intratumoral heterogeneity and early adaptive drug resistance. In summary, minimal residual disease as a result of intratumoral heterogeneity is the earliest form of acquired drug resistance. Emerging technologies such as liquid biopsy and single-cell methods allow for studying targetable drivers of minimal residual disease and contribute to preemptive combinatorial targeting of both drivers of the tumor and its minimal residual disease cells.

Recent Progress in Ferroptosis Inducers for Cancer Therapy

Ferroptosis is a newly discovered form of regulated cell death that is the nexus between metabolism, redox biology, and human health. Emerging evidence shows the potential of triggering ferroptosis for cancer therapy, particularly for eradicating aggressive malignancies that are resistant to traditional therapies. Recently, there has been a great deal of effort to design and develop anticancer drugs based on ferroptosis induction. Recent advances of ferroptosis-inducing agents at the intersection of chemistry, materials science, and cancer biology are presented. The basis of ferroptosis is summarized first to highlight the feasibility and characteristics of triggering ferroptosis for cancer therapy. A literature review of ferroptosis inducers (including small molecules and nanomaterials) is then presented to delineate their design, action mechanisms, and anticancer applications. Finally, some considerations for research on ferroptosis inducers are spotlighted, followed by a discussion on the challenges and future development directions of this burgeoning field.

Spatiotemporally Tracking the Programmable Mitochondrial Membrane Potential Evolutions by a Robust Molecular Rotor

Mitochondrial membrane potential (MMP) represents an essential parameter of cellular activities, and even a minute MMP variation could significantly affect the biological functions of living organisms. Thus, convenient and accurate MMP detection is highly desirable since conventional MMP probes are always constrained by photobleaching, inconvenience, and irreversibility. Herein, a spatial-dependent fluorescent molecular rotor Mito-Cy is introduced for efficiently tracking the varied MMP status through its restricted intramolecular rotation in mitochondria and nucleus compartments. Based on a systematic investigation, the specifically lit up fluorescent Mito-Cy enables us to explore different MMP situations by determining their varied distributions. Accordingly, Mito-Cy concentrates in mitochondria under normal MMP status. Yet Mito-Cy starts to migrate gradually from mitochondria to the nucleus in decreasing MMP status, as represented by the increasing distribution levels of fluorescent Mito-Cy in the nucleus. Mito-Cy exclusively accumulates in the nucleus at ultimate vanishing MMP status. The facile operation of Mito-Cy, together with its high photostability and sensitivity, facilitates the monitoring of the reversible and programmable MMP evolutions in living cells. The Mito-Cy-involved logic control over MMP, e.g., AND and OR gates, indicates that the robust and versatile Mito-Cy holds great potential for illuminating mitochondrial viscosity-related bioprocesses.

Targeting Heterogeneous Tumors Using a Multifunctional Molecular Prodrug

Reported here is a molecular construct (K1) designed to overcome hurdles associated with delivering active drugs to heterogeneous tumor environments. Construct K1 relies on two cancer environment triggers (GSH and H₂O₂) to induce prodrug activation. It releases an active drug form (SN-38) under conditions of both oxidative and reductive stress in vitro. Specific uptake of K1 in COX-2 positive aggressive colon cancer cells (SW620 and LoVo) was seen, along with enhanced anticancer activity compared with the control agent SN-38. These findings are attributed to environmentally triggered drug release, as well as simultaneous scavenging of species giving rise to intracellular redox stress. K1 serves to downregulate various cancer survival signaling pathways (AKT, p38, IL-6, VEGF, and TNF-α) and upregulate an anti-inflammatory response (IL-10). Compared with SN-38 and DMSO as controls, K1 also displayed an improved in vivo therapeutic efficacy in a xenograft tumor regrowth model with no noticeable systematic toxicity at the administrated dose. We believe that the strategy described here presents an attractive approach to addressing solid tumors characterized by intratumoral heterogeneity.

Regulation of mitochondrial function as a promising target in platelet activation-related diseases

Platelets are anucleated cell elements produced by fragmentation of the cytoplasm of megakaryocytes and have a unique metabolic phenotype compared with circulating leukocytes, exhibiting a high coupling efficiency to mitochondrial adenosine triphosphate production with reduced respiratory reserve capacity. Platelet mitochondria are well suited for ex vivo analysis of different diseases. Even some diseases induce mitochondrial changes in platelets without reflecting them in other organs. During platelet activation, an integrated participation of glycolysis and oxidative phosphorylation is mediated by oxidative stress production-dependent signaling. The platelet activation-dependent procoagulant activity mediated by collagen, thrombin and hyperglycemia induce mitochondrial dysfunction to promote thrombosis in oxidative stress-associated pathological conditions. Interestingly, some compounds exhibit a protective action on platelet mitochondrial dysfunction through control of mitochondrial oxidative stress production or inhibition of respiratory complexes. They can be grouped in a) Natural source-derived compounds (e.g. Xanthohumol, Salvianoloc acid A and Sila-amide derivatives of NAC), b) TPP⁺-linked small molecules (e.g. mitoTEMPO and mitoQuinone) and c) FDA-approved drugs (e.g. metformin and statins), illustrating the wide range of molecular structures capable of effectively interacting with platelet mitochondria. The present review article aims to discuss the mechanisms of mitochondrial dysfunction and their association with platelet activation-related diseases.

Mitochondria and Nuclei Dual-Targeted Hollow Carbon Nanospheres for Cancer Chemophotodynamic Synergistic Therapy

Dual-targeted nanoparticles are gaining increasing importance as a more effective anticancer strategy by attacking double key sites of tumor cells, especially in chemophotodynamic therapy. To retain the nuclei inhibition effect and enhance doxorubicin (DOX)-induced apoptosis by mitochondrial pathways simultaneously, we synthesized the novel nanocarrier (HKH) based on hollow carbon nitride nanosphere (HCNS) modified with hyaluronic acid (HA) and the mitochondrial localizing peptide D[KLAKLAK]2 (KLA). DOX-loaded HKH nanoparticles (HKHDs) showed satisfactory drug-loading efficiency, excellent solubility, and very low hemolytic effect. HA/CD44 binding and electrostatic attraction between positively charged KLA and A549 cells facilitated HKHD uptake via the endocytosis mechanism. Acidic microenvironment, hyaluronidase, and KLA targeting together facilitate doxorubicin toward the mitochondria and nuclei, resulting in apoptosis, DNA intercalation, cell-cycle arrest at the S phase, and light-induced reactive oxygen species production. Intravascular HKHD inhibited tumor growth in A549-implanted mice with good safety. The present study, for the first time, systemically reveals biostability, targetability, chemophotodynamics, and safety of the functionalized novel HKHD.

Lipoic acid-derived cross-linked liposomes for reduction-responsive delivery of anticancer drug

Liposomes have emerged as a fascinating nanocarriers for the delivery of cancer therapeutics. However, their efficacy for cancer therapy is reduced partially because of the serum-instability and incomplete drug release. In this study, a novel disulfide cross-linked liposomes (CLs) assembled from dimeric lipoic acid-derived glycerophosphorylcholine (di-LA-PC) conjugate was developed. The conjugate was synthesized by a facial esterification of lipoic acid (LA) and glycerophosphorylcholine (GPC) and characterized by MS, ¹H NMR and ¹³C NMR. Featuring the enhanced serum-stability and intracellular drug release determined by in vitro stability and GSH-responsive behavior, CLs prepared with dried thin film technique following 10 % dithiothreitol (DTT) cross-linking can attain effective delivery of anticancer candidates. Notably, CLs stably encapsulated doxorubicin (Dox) in their vesicular structures and showed a remarkable thiol-sensitive release of payload upon cellular uptake by cancer cells, compared to that of uncross-linked liposomes (uCLs) or Doxil-like liposome (DLLs). The cell viability and apoptosis of Dox-loaded CLs worked the pronounced cytotoxic effects to MCF-7 cells with an IC₅₀ value of 10.8 μg Dox equiv./mL comparable to free Dox and 2.8-fold higher than DLLs. More importantly, it is demonstrated that the nanoscale characteristics of Dox-loaded CLs could prevent the proliferation of adriamycin-resistant MCF-7/ADR cell line, highlighting their potential in reversal of drug resistance. Furthermore, the preliminary in vivo test (n = 3) showed that disulfide cross-linked liposomal formulation of Dox (Dox-CLs) improved the therapeutic efficacy compared to free Dox and DLLs in a human breast carcinoma xenograft mouse model. Therefore, the current thiol-responsive cross-linked liposome may provide a robust drug delivery platform for cancer therapy.

An organoruthenium complex overcomes ABCG2-mediated multidrug resistance via multiple mechanisms

An organoruthenium complex, RuF, via multiple mechanisms, exhibited effective anticancer activity in vitro and in vivo for surmounting multidrug resistance mediated by the ABCG2 transporter.

Glycyrrhetinic acid as a hepatocyte targeting unit for an anticancer drug delivery system with enhanced cell type selectivity

Herein, we explore glycyrrhetinic acid (GA) as an active targeting ligand for hepatocellular carcinoma (HCC) using a small molecule approach.