Theranostic Platforms Based on Silica and Magnetic Nanoparticles Containing Quinacrine, Chitosan, Fluorophores, and Quantum Dots.

In this paper, we describe the synthesis of multilayer nanoparticles as a platform for the diagnosis and treatment of ischemic injuries. The platform is based on magnetite (MNP) and silica (SNP) nanoparticles, while quinacrine is used as an anti-ischemic agent. The synthesis includes the surface modification of nanoparticles with (3-glycidyloxypropyl)trimethoxysilane (GPMS), the immobilization of quinacrine, and the formation of a chitosan coating, which is used to fix the fluorophore indocyanine green (ICG) and colloidal quantum dots AgInS2/ZnS (CQDs), which serve as secondary radiation sources. The potential theranostic platform was studied in laboratory animals.

Antimalarial Quinacrine and Chloroquine Lose Their Activity by Decreasing Cationic Amphiphilic Structure with a Slight Decrease in pH.

Quinacrine (QC) and chloroquine (CQ) have antimicrobial and antiviral activities as well as antimalarial activity, although the mechanisms remain unknown. QC increased the antimicrobial activity against yeast exponentially with a pH-dependent increase in the cationic amphiphilic drug (CAD) structure. CAD-QC localized in the yeast membranes and induced glucose starvation by noncompetitively inhibiting glucose uptake as antipsychotic chlorpromazine (CPZ) did. An exponential increase in antimicrobial activity with pH-dependent CAD formation was also observed for CQ, indicating that the CAD structure is crucial for its pharmacological activity. A decrease in CAD structure with a slight decrease in pH from 7.4 greatly reduced their effects; namely, these drugs would inefficiently act on falciparum malaria and COVID-19 pneumonia patients with acidosis, resulting in resistance. The decrease in CAD structure at physiological pH was not observed for quinine, primaquine, or mefloquine. Therefore, restoring the normal blood pH or using pH-insensitive quinoline drugs might be effective for these infectious diseases with acidosis.

Anti-Cancer Stem Cells Potentiality of an Anti-Malarial Agent Quinacrine: An Old Wine in a New Bottle.

Quinacrine (QC) is a tricyclic compound and a derivative of 9-aminoacridine. It has been widely used to treat malaria and other parasitic diseases since the last century. Interestingly, studies have revealed that it also displays anti-cancer activities. Here, we have discussed the anti-cancer mechanism of QC along with its potentiality to specifically target cancer stem cells. The anti-cancer action of this drug includes DNA intercalation, inhibition of DNA repair mechanism, prevention of cellular growth, cell cycle arrest, inhibition of DNA and RNA polymerase activity, induction of autophagy, promotion of apoptosis, deregulation of cell signaling in cancer cells and cancer stem cells, inhibition of metastasis and angiogenesis. In addition, we have also emphasized on the synergistic effect of this drug with other potent chemotherapeutic agents and mentioned its different applications in anti-cancer therapy.

Nanoformulated quinacrine regulates NECTIN-4 domain specific functions in cervical cancer stem cells.

NECTIN-4 [a poliovirus receptor-related-4 (PVRL-4) encoded gene] has vital roles in cancer proliferation, metastasis and angiogenesis. It possesses three different domains and it is predicted that they have different roles in cancer but the structure-function relationship is still unknown and hence carrying out a detailed study to elucidate the domain-specific functions of NECTIN-4 in cancer is necessary. Using 5-Fluouracil-resistant cervical cancer stem cells (PEMT-5FU-R-MC) and different NECTIN-4 domain-specific constructs, different domains of NECTIN-4 were over-expressed in PEMT-5FU-R-MC cells. Biochemical assays like comet, γ-H2AX immunofluorescence, western blot, in vitro tube formation, gelatin zymography, in ovo CAM assay, etc. were used to delineate the function of each domain of NECTIN-4 in cancer and their regulation by nano-formulated quinacrine (NQC). Endo-domain (lacking extracellular region corresponding to aa 30-347) and ecto-domain (lacking signal peptide and cytoplasmic region corresponding to aa 1-29 and 348-509, respectively) of NECTIN-4 were largely overexpressed in nucleus and cytoplasm, respectively. Endo-domain translocates into nucleus by physically interacting with IMPORTIN-α2, activates the DNA repair and enhances cell growth, whereas ecto-domain specifically activates angiogenesis by modulating representative angiogenic markers, inducing in vitro tube formation and in ovo blood vessel formation. Full-length NECTIN-4 (aa 1-509) was overexpressed in both nucleus and cytoplasm and modulated both DNA repair and angiogenesis. NQC down-regulated these phenomena by modulating the endo-domain and ecto-domain of NECTIN-4. Thus, current study suggested that endo-domain of NECTIN-4 translocated into nucleus and increased the DNA repair and ecto-domain of NECTIN-4 enhanced the angiogenesis, whereas NQC inhibits these processes.

Development of inhalable quinacrine loaded bovine serum albumin modified cationic nanoparticles: Repurposing quinacrine for lung cancer therapeutics.

Drug repurposing is on the rise as an atypical strategy for discovery of new molecules, involving use of pre-existing molecules for a different therapeutic application than the approved indication. Using this strategy, the current study aims to leverage effects of quinacrine (QA), a well-known anti-malarial drug, for treatment of non-small cell lung cancer (NSCLC). For respiratory diseases, designing a QA loaded inhalable delivery system has multiple advantages over invasive delivery. QA-loaded nanoparticles (NPs) were thus prepared using polyethyleneimine (PEI) as a cationic stabilizer. While the use of PEI provided cationic charge on the particles, it also mediated a burst release of QA and demonstrated potential particle toxicity. These concerns were circumvented by coating nanoparticles with bovine serum albumin (BSA), which retained the cationic charge, reduced NP toxicity and modulated QA release. Prepared nanoparticles were characterized for physicochemical properties along with their aerosolization potential. Therapeutic efficacy of the formulations was tested in different NSCLC cells. Mechanism of higher anti-proliferation was evaluated by studying cell cycle profile, apoptosis and molecular markers involved in the progression of lung cancer. BSA coated QA nanoparticles demonstrated good aerosolization potential with a mass median aerodynamic diameter of significantly less than 5 µm. Nanoparticles also demonstrated improved therapeutic efficacy against NSCLC cells in terms of low IC50 values, cell cycle arrest at G2/M phase and autophagy inhibition leading to increased apoptosis. BSA coated QA NPs also demonstrated enhanced therapeutic efficacy in a 3D cell culture model. The present study thus lays solid groundwork for pre-clinical and eventual clinical studies as a standalone therapy and in combination with existing chemotherapeutics.

Comparative and Mechanistic Study on the Anticancer Activity of Quinacrine-Based Silver and Gold Hybrid Nanoparticles in Head and Neck Cancer.

Using oral cancer cells ( in vitro) and in vivo xenograft mice model, we have systematically studied the detailed mechanism of anticancer activity of quinacrine-based hybrid silver (QAgNP) and gold (QAuNP) nanoparticles (NPs) and compared their efficacies. Both the NPs showed characteristic anti-cell proliferation profile in various cancer cells with minimally affecting the normal nontransformed breast epithelial MCF-10A cells. The IC50 values of QAuNP in various cancer cells were less compared to QAgNP and also found to be the lowest (0.5 µg/mL) in SCC-9 oral cancer cells. Although both NPs caused apoptosis by increased DNA damage, arresting at S phase and simultaneously inhibiting the DNA repair activity in cells, efficacy of QAuNP was better than that of QAgNP. NPs intercalated with DNA and inhibited the topoisomerase activity in cells. Alteration in expression of cell cycle regulatory (cyclins B1, E1, A2, etc.) and replication-related (MRE11, RPA, RFC, etc.) proteins were also observed after NP exposure to the cells. Accumulation of cells resulted in extended G/M phase after prolonged exposure of QAuNP in SCC-9 cells. Interestingly, depletion of geminin and increase of Cdt-1 along with CDC-6 suggest the formation of re-replication. Recovery of body weight and reduction in tumor volume were found in NP-treated xenograft mice. Induction of Bax/Bcl-xL, PARP-1 cleavage, p53, and p21 were noted in NP-treated xenograft mice tissue samples. Thus, data suggest that NP inhibits topoisomerase activity, thereby inhibiting DNA replication and inducing re-replication, which causes S-phase arrest, DNA damage, and finally apoptosis of the oral cancer cells. Also, it was found that anticancer activity of QAuNP is better than that of QAgNP.

Metallic gold and bioactive quinacrine hybrid nanoparticles inhibit oral cancer stem cell and angiogenesis by deregulating inflammatory cytokines in p53 dependent manner.

Complete eradication of aggressive oral cancer remains a challenge due to the presence of CSCs. They resist conventional chemotherapeutic agents due to their self-renewal, drug efflux, and efficient DNA repair capacity. Here, we formulated a hybrid-nanoparticle (QAuNP) using quinacrine and gold and characterized/investigated its anti-angiogenic and anti-metastatic effect on OSCC-CSCs. QAuNP significantly inhibited cellular proliferation, caused apoptosis in vitro, and disrupted angiogenesis in vivo and tumor regression in xenograft mice model. It not only inhibited crucial angiogenic markers Ang-1, Ang-2 and VEGF but also depleted MMP-2 in H-357-PEMT cells in a p53 and p21-dependent manner. QAuNP also increased the ROS and NO generation in OSCC-CSCs and reduced the mitochondrial membrane potential. It altered the level of inflammatory cytokines IL-6, IL-1ß, TNF-α and metastasis-associated markers (CD-44, CD-133) in H-357-PEMT and CM-treated endothelial cells (HUVEC) in p53/p21-dependent manner. Therefore, QAuNP will be a useful therapeutic agent against metastatic OSCC.

Biophysical insight into the heparin-peptide interaction and its modulation by a small molecule.

The heparin-protein interaction plays a vital role in numerous physiological and pathological processes. Not only is the binding mechanism of these interactions poorly understood, studies concerning their therapeutic targeting are also limited. Here, we have studied the interaction of the heparin interacting peptide (HIP) from Tat (which plays important role in HIV infections) with heparin. Isothermal titration calorimetry binding exhibits distinct biphasic isotherm with two different affinities in the HIP-heparin complex formation. Overall, the binding was mainly driven by the nonionic interactions with a small contribution from ionic interactions. The stoichiometric analysis suggested that the minimal site for a single HIP molecule is a chain of 4 to 5 saccharide molecules, also supported by docking studies. The investigation was also focused on exploiting the possibility of using a small molecule as an inhibitor of the HIP-heparin complex. Quinacrine, because of its ability to mimic the HIP interactions with heparin, was shown to successfully modulate the HIP-heparin interactions. This result demonstrates the feasibility of inhibiting the disease relevant heparin-protein interactions by a small molecule, which could be an effective strategy for the development of future therapeutic agents.

Design and synthesis of novel quinacrine-[1,3]-thiazinan-4-one hybrids for their anti-breast cancer activity.

In an attempt to develop effective and safe anticancer agents, we designed, synthesized and examined 23 novel quinacrine (QC) derivatives by combining the 9-aminoacridine scaffold and the [1,3]thiazinan-4-ones group. Most of these hybrids showed strong anticancer activities, among which 3-(3-(6-chloro-2-methoxyacridin-9-ylamino)propyl)-2-(thiophen-2-yl)-1,3-thiazinan-4-one (25; VR151) effectively killed many different cancer cell types, including eight breast cancer cell lines with different genetic background, two prostate cancer and two lung cancer cell lines. In contrast, compound 25 is less effective against non-cancer cells, suggesting it may be less toxic to humans. Our data showed that cancer cells are arrested in S phase for a prolonged period due to the down-regulation of DNA replication, leading to eventual cell death. We have also shown that the S phase arrest may be resulted by the down-regulation of cyclin A coupled with the continued up-regulation of cyclin E, which coincide with the down-regulation of mTor-S6K and mTor-4EBP1 pathways.

Binding affinity toward human prion protein of some anti-prion compounds - Assessment based on QSAR modeling, molecular docking and non-parametric ranking.

The present study is based on the quantitative structure-activity relationship (QSAR) analysis of binding affinity toward human prion protein (huPrPC) of quinacrine, pyridine dicarbonitrile, diphenylthiazole and diphenyloxazole analogs applying different linear and non-linear chemometric regression techniques, including univariate linear regression, multiple linear regression, partial least squares regression and artificial neural networks. The QSAR analysis distinguished molecular lipophilicity as an important factor that contributes to the binding affinity. Principal component analysis was used in order to reveal similarities or dissimilarities among the studied compounds. The analysis of in silico absorption, distribution, metabolism, excretion and toxicity (ADMET) parameters was conducted. The ranking of the studied analogs on the basis of their ADMET parameters was done applying the sum of ranking differences, as a relatively new chemometric method. The main aim of the study was to reveal the most important molecular features whose changes lead to the changes in the binding affinities of the studied compounds. Another point of view on the binding affinity of the most promising analogs was established by application of molecular docking analysis. The results of the molecular docking were proven to be in agreement with the experimental outcome.

Ultrafast Spectroscopic Dynamics of Quinacrine-Riboflavin Binding Protein Interactions.

Redox active cofactors play a dynamic role inside protein binding active sites because the amino acids responsible for binding participate in electron transfer (ET) reactions. Here, we use femtosecond transient absorption (FsTA) spectroscopy to examine the ultrafast ET between quinacrine (Qc), an antimalarial drug with potential anticancer activity, and riboflavin binding protein (RfBP) with a known Kd = 264 nM. Steady-state absorption reveals a ∼ 10 nm red-shift in the ground state when QcH32+ is titrated with RfBP, and a Stern-Volmer analysis shows ∼84% quenching and a blue-shift of the QcH32+ photoluminescence to form a 1:1 binding ratio of the QcH32+-RfBP complex. Upon selective photoexcitation of QcH32+ in the QcH32+-RfBP complex, we observe charge separation in 7 ps to form 1[QcH3_red•+-RfBP•+], which persists for 138 ps. The FsTA spectra show the spectroscopic identification of QcH3_red•+, determined from spectroelectrochemical measurements in DMSO. We correlate our results to literature and report lifetimes that are 10-20× slower than the natural riboflavin, Rf-RfBP, complex and are oxygen independent. Driving force (ΔG) calculations, corrected for estimated dielectric constants for protein hydrophobic pockets, and Marcus theory depict a favorable one-electron ET process between QcH32+ and nearby redox active tyrosine (Tyr) or tryptophan (Trp) residues.

Design, synthesis and characterization of novel quinacrine analogs that preferentially kill cancer over non-cancer cells through the down-regulation of Bcl-2 and up-regulation of Bax and Bad.

Both quinacrine, which contains a 9-aminoacridine scaffold, and thiazolidin-4-one are promising anticancer leads. In an attempt to develop effective and potentially safe anticancer agents, we synthesized 23 novel hybrid compounds by linking the main structural unit of the 9-aminoacridine ring with the thiazolidin-4-one ring system, followed by examination of their anticancer effects against three human breast tumor cell lines and matching non-cancer cells. Most of the hybrid compounds showed good activities, and many of them possessed the preferential killing property against cancer over non-cancer cells. In particular, 3-[3-(6-chloro-2-methoxy-acridin-9-ylamino)-propyl]-2-(2,6-difluoro-phenyl)-thiazolidin-4-one (11; VR118) effectively killed/inhibited proliferation of cancer cells at IC50 values in the range of 1.2-2.4 µM. Furthermore, unlike quinacrine or cisplatin, compound 11 showed strong selectivity for cancer cell killing, as it could kill cancer cells 7.6-fold (MDA-MB231 vs MCF10A) to 14.7-fold (MCF7 vs MCF10A) more effectively than matching non-cancer cells. Data from flow cytometry, TUNEL and Western blot assays showed that compound 11 kills cancer cells by apoptosis through the down-regulation of Bcl-2 (but not Bcl-XL) survival protein and up-regulation of Bad and Bax pro-apoptotic proteins. Thus, compound 11 is a highly promising lead for an effective and potentially anticancer therapy.

Targeting Conformational Activation of CDK2 Kinase.

Cyclin-dependent kinases constitute attractive pharmacological targets for cancer therapeutics, yet inhibitors in clinical trials target the ATP-binding pocket of the CDK and therefore suffer from limited selectivity and emergence of resistance. The more recent development of allosteric inhibitors targeting conformational plasticity of protein kinases offers promising perspectives for therapeutics. In particular tampering with T-loop dynamics of CDK2 kinase would provide a selective means of inhibiting this kinase, by preventing its conformational activation. To this aim we engineered a fluorescent biosensor that specifically reports on conformational changes of CDK2 activation loop and is insensitive to ATP or ATP-competitive inhibitors, which constitutes a highly sensitive probe for identification of selective T-loop modulators. This biosensor was successfully applied to screen a library of small chemical compounds leading to discovery of a family of quinacridine analogs, which potently inhibit cancer cell proliferation, and promote accumulation of cells in S phase and G2. These compounds bind CDK2/ Cyclin A, inhibit its kinase activity, compete with substrate binding, but not with ATP, and dock onto the T-loop of CDK2. The best compound also binds CDK4 and CDK4/Cyclin D1, but not CDK1. The strategy we describe opens new doors for the discovery of a new class of allosteric CDK inhibitors for cancer therapeutics.

Antiviral activities of selected antimalarials against dengue virus type 2 and Zika virus.

In a previous study, twelve antimalarial compounds, amodiaquine (AQ) and derivatives, were shown to have potent anti-dengue viral (DENV) activity by using the stable DENV2 Renilla luciferase reporter replicon expressing BHK-21 cells, infectivity (plaque), and the qRT-PCR assays. In this study, we performed molecular modeling on these compounds to determine their stereo-electronic properties required for optimal antiviral activity. Based on the similarity of calculated stereo-electronic profiles, specifically the electrostatic potential profiles of the compounds, and in silico screening of related compounds from literature, we identified three additional compounds, Quinacrine (QC), Mefloquine (MQ), and GSK369796. Analysis of their antiviral activities indicated that all three compounds have high anti-DENV activity in the DENV2 replicon expressing cells with EC50 values of 5.30 ± 1.31 µM (QC), 3.22 ± 0.37 µM (MQ), and 5.06 ± 0.86 µM (GSK369796). The infectivity assays revealed the EC50 values of 7.09 ± 1.67 µM (QC), 4.36 ± 0.31 µM (MQ) and 3.03 ± 0.35 µM (GSK369796). The mode of action of these compounds is through inhibition of autophagy, thereby affecting DENV2 replication. Moreover, these compounds also showed antiviral activity against the rapidly emerging Zika virus (ZIKV) with EC50 values of 2.27 ± 0.14 µM (QC), 3.95 ± 0.21 µM (MQ), and 2.57 ± 0.09 µM (GSK369796).

Reactivity of 9-aminoacridine drug quinacrine with glutathione limits its antiprion activity.

Quinacrine-the drug based on 9-aminoacridine-failed in clinical trials for prion diseases, whereas it was active in in vitro studies. We hypothesize that aromatic nucleophilic substitution at C9 could be contributing factor responsible for this failure because of the transfer of acridine moiety from quinacrine to abundant glutathione. Here, we described the semi-large-scale synthesis of the acridinylated glutathione and the consequences of its formation on biological and biophysical activities. The acridinylated glutathione is one order of magnitude weaker prion protein binder than the parent quinacrine. Moreover, according to log DpH 7.4 , the glutathione conjugate is two orders of magnitude more hydrophilic than quinacrine. Its higher hydrophilicity and higher dsDNA binding potency will significantly decrease its bioavailability in membrane-like environment. The glutathione deactivates quinacrine not only directly but also decreases its bioavailability. Furthermore, the conjugate can spontaneously decompose to practically insoluble acridone, which is precipitated out from the living systems.

A Quinacrine Analogue Selective Against Gastric Cancer Cells: Insight from Biochemical and Biophysical Studies.

One of the earliest synthetic antimalarial drugs, quinacrine, was recently reported as interesting for the treatment of acute myeloid leukemia. Inspired by this and similar findings, we evaluated a set of quinacrine analogues against gastric (MKN-28), colon (Caco-2), and breast (MFC-7) cancer cell lines and one normal human fibroblast cell line (HFF-1). All the compounds, previously developed by us as dual-stage antimalarial leads, displayed antiproliferative activity, and one of the set stood out as selective toward the gastric cancer cell line, MKN-28. Interestingly, this compound was transported across an in vitro MKN-28 model cell line in low amounts, and approximately 80 % was trapped inside those cells. Nuclear targeting of the same compound and its interactions with calf thymus DNA were assessed through combined fluorescence microscopy, spectroscopy, and calorimetry studies, which provided evidence for the compound's ability to reach the nucleus and to interact with DNA.

ATP-containing vesicles in stria vascular marginal cell cytoplasms in neonatal rat cochlea are lysosomes.

We confirmed that ATP is released from cochlear marginal cells in the stria vascular but the cell organelle in which ATP stores was not identified until now. Thus, we studied the ATP-containing cell organelles and suggest that these are lysosomes. Primary cultures of marginal cells of Sprague-Dawley rats aged 1-3 days was established. Vesicles within marginal cells stained with markers were identified under confocal laser scanning microscope and transmission electron microscope (TEM). Then ATP release from marginal cells was measured after glycyl-L-phenylalanine-ß- naphthylamide (GPN) treatment using a bioluminescent assay. Quinacrine-stained granules within marginal cells were labeled with LysoTracker, a lysosome tracer, and lysosomal-associated membrane protein 1(LAMP1), but not labeled with the mitochondrial tracer MitoTracker. Furthermore, LysoTracker-labelled puncta showed accumulation of Mant-ATP, an ATP analog. Treatment with 200 µM GPN quenched fluorescently labeled puncta after incubation with LysoTracker or quinacrine, but not MitoTracker. Quinacrine-labeled organelles observed by TEM were lysosomes, and an average 27.7 percent increase in ATP luminescence was observed in marginal cells extracellular fluid after GPN treatment. ATP-containing vesicles in cochlear marginal cells of the stria vascular from neonatal rats are likely lysosomes. ATP release from marginal cells may be via Ca(2+)-dependent lysosomal exocytosis.

Enhancement of Cytotoxicity and Inhibition of Angiogenesis in Oral Cancer Stem Cells by a Hybrid Nanoparticle of Bioactive Quinacrine and Silver: Implication of Base Excision Repair Cascade.

A poly(lactic-co-glycolic acid) (PLGA)-based uniform (50-100 nm) hybrid nanoparticle (QAgNP) with positive zeta potential (0.52 ± 0.09 mV) was prepared by single emulsion solvent evaporation method with bioactive small molecule quinacrine (QC) in organic phase and silver (Ag) in aqueous phase. Physiochemical properties established it as a true hybrid nanoparticle and not a mixture of QC and Ag. Antitumor activity of QAgNP was evaluated by using various cancer cell lines including H-357 oral cancer cells and OSCC-cancer stem cell in an in vitro model system. QAgNP caused more cytotoxicity in cancer cells than normal epithelial cells by increasing BAX/BCL-XL, cleaved product PARP-1, and arresting the cells at S phase along with DNA damage. In addition, QAgNPs offered greater ability to kill the OSCC-CSCs compared to NQC and AgNPs. QAgNP offered anticancer action in OSCC-CSCs by inhibiting the base excision repair (BER) within the cells. Interestingly, alteration of BER components (Fen-1 and DNA polymerases (ß, δ, and ε) and unalteration of NHEJ (DNA-PKC) or HR (Rad-51) components was noted in QAgNP treated OSCC-CSC cells. Furthermore, QAgNP significantly reduced angiogenesis in comparison to physical mixture of NQC and AgNP in fertilized eggs. Thus, these hybrid nanoparticles caused apoptosis in OSCC-CSCs by inhibiting the angiogenesis and BER in cells.

Targeting Epirubicin Plus Quinacrine Liposomes Modified with DSPE-PEG2000-C(RGDfK) Conjugate for Eliminating Invasive Breast Cancer.

Recurrence of invasive breast cancer could arise from the residual cancer cells after comprehensive treatment. It is possible that residual invasive cancer cells are capable of forming highly patterned vasculogenic mimicry (VM) channels, leading to relapse and metastasis. In the present study, a new type of targeting epirubicin plus quinacrine liposomes was developed by modifying functional DSPE-PEG2000 with C(RGDfK), a cyclic peptide containing Arg-Gly-Asp. These liposomes could potentially eliminate invasive breast cancer and destroy VM channels. Evaluations were made in human invasive breast cancer cells and their xenografts in nude mice. The results showed that the targeting epirubicin plus quinacrine liposomes could enhance the accumulation and uptake of the drugs in cancer tissues, kill cancer cells directly, activate apoptotic enzymes, destroy the VM channels and downregulate the VM channel-forming marker molecules (EphA2, FAK, PI3K, MMP 9, MMP 14, VE-Cad and HIF-α), thereby exhibiting a strong overall anticancer efficacy. The targeting epirubicin plus quinacrine liposomes provided a promising strategy to treat invasive breast cancer and to prevent the relapse arising from VM channels after chemotherapy.

Synthesis of improved lysomotropic autophagy inhibitors.

Autophagy is a conserved cellular pathway used to recycle nutrients through lysosomal breakdown basally and under times of stress (e.g., nutrient deprivation, chemotherapeutic treatment). Oncogenes are known to induce autophagy, which may be exploited by cancers for cell survival. To identify autophagy inhibitors with potential therapeutic value for cancer, we screened a panel of antimalarial agents and found that quinacrine (QN) had 60-fold higher potency of autophagy inhibition than chloroquine (CQ), a well-known autophagy inhibitor that functions by disrupting lysosomal activity. Despite desirable autophagy inhibiting properties, QN showed considerable cytotoxicity. Therefore, we designed and synthesized a novel series of QN analogs and investigated their effects on autophagy inhibition and cell viability. Notably, we found two compounds (33 and 34), bearing a backbone of 1,2,3,4-tetrahydroacridine, had limited cytotoxicity yet strong autophagy inhibition properties. In conclusion, these improved lysomotropic autophagy inhibitors may have use as anticancer agents in combination with conventional therapies.