Total coliform detection in drinking water: comparison of membrane filtration with Colilert and Coliquik

The Colilert (CL) and Coliquik (CQ) systems were compared in a presence-absence format against the Standard Methods membrane filtration (MF) technique to determine whether differences existed in total coliform detection. Approximately 750 water samples were collected from distribution systems, covered and uncovered storage reservoirs, well sites, and the influent to drinking water treatment plants. Samples were analyzed for total coliforms and heterotrophic bacteria with MF, CL, and CQ. The agreements between CL and MF and between CQ and MF were both greater than 94.8%, which indicates that both may be acceptable methods for total coliform detection. Disagreement between the CL and CQ methods was primarily due to false-negative results. Furthermore, laboratory and field inoculation methods were compared for CL, more than 98% agreement was obtained. This finding indicates that sampling and immediate field inoculation may be an alternative to the traditional laboratory inoculation.     

Total coliform detection in drinking water: comparison of membrane filtration with Colilert and Coliquik.

The Colilert (CL) and Coliquik (CQ) systems were compared in a presence-absence format against the Standard Methods membrane filtration (MF) technique to determine whether differences existed in total coliform detection. Approximately 750 water samples were collected from distribution systems, covered and uncovered storage reservoirs, well sites, and the influent to drinking water treatment plants. Samples were analyzed for total coliforms and heterotrophic bacteria with MF, CL, and CQ. The agreements between CL and MF and between CQ and MF were both greater than 94.8%, which indicates that both may be acceptable methods for total coliform detection. Disagreement between the CL and CQ methods was primarily due to false-negative results. Furthermore, laboratory and field inoculation methods were compared for CL, more than 98% agreement was obtained. This finding indicates that sampling and immediate field inoculation may be an alternative to the traditional laboratory inoculation.     

Simultaneous determination of chloroquine and metronidazole in human biological fluid by high pressure liquid chromatography

Chloroquine (CQ) and metronidazole (MZ) were measured in human urine and plasma by HPLC with UV detection. This method was used to analyse plasma levels in 4 African volunteers after an oral dose of 1000 mg CQ and 750 mg MZ, in a European on weekly prophylaxis of 500 mg CQ, and on 50 hospital urine samples. In the Africans peak plasma levels were over 1 microgram/ml and peak time was 1 1/2-2 hr. In the European plasma levels ranged from 0.58 to 0.36 microgram/ml. Over 80% of the urine samples contained CQ, MZ or both. The assay system was found flexible and economical for the therapeutic monitoring of these two important tropical drugs.     

近海柴油降解菌群的构建及其对柴油的降解特性

【目的】实施近海柴油污染的生物治理。【方法】以柴油为唯一碳源,从深圳港口海域富集筛选柴油降解菌;采用复配、正交试验等方式构建混合菌群;通过单因素试验研究环境因素对菌群降解柴油的影响;使用气相色谱-氢火焰检测器(GC-FID)分析降解前后柴油各组分的变化;通过生理生化试验和16S rRNA基因序列分析对菌株进行鉴定。【结果】获得了16株柴油降解菌,7 d内对柴油的降解率最高达40.8%;选择菌株C1-8、C2-10、C3-13构建了混合菌群CQ1,投加量分别为0.5%、2.0%和1.0%,CQ1对柴油去除率比单菌提高了10%以上;CQ1的最适环境条件为：温度30 °C、pH 7.6、摇床转速220 r/min、柴油浓度20 g/L,优化后9 d内对柴油去除率达60%以上;GC-FID结果显示,菌群CQ1可降解大部分C11?C27的正构烷烃,对C21?C27的烷烃降解可达100%。经鉴定,菌株C1-8、C2-10和C3-13分别为微杆菌(Microbacterium sp.)、剑菌(Ensifer sp.)和变异棒杆菌(Corynebacterium variabile)。【结论】CQ1在近海柴油污染的生物修复中具有良好的应用前景。     

In vivo interaction between mouse liver lysosomes and chloroquine

Particles sedimenting at 27,000 g X 10 min (MLCQ) were separated from liver homogenates of mice injected with chloroquine (CQ). The MLCQ contained most of the drug recovered in the organ as well as 50% of the liver aryl sulphatase activity. The release of CQ from MLCQ was studied in some physicochemical conditions, and in the presence of various agents known to modify membrane composition and stability. At pH 7.4, the equilibrium between free and bound CQ depended on the dilution of the MLCQ, and the time to reach equilibrium was strongly influenced by the temperature of incubation. Several agents causing membrane disruption and lysosomal enzyme leakage, such as osmotic shock, sonication and digitonin, had little effect on the CQ release. Acid and alkaline buffers, 0.55 M KCl and 0.1% Triton X-100 caused, instead, the immediate release of most of the bound CQ. Concentrations of digitonin causing the release of aryl sulphatase activity had little effect on bound CQ, suggesting that the drug is retained in lysosomes by forces and/or structures different in nature from those retaining most of the lysosomal enzyme activity. We think that the CQ trapped in lysosomes is bound to high affinity sites in membranous structures which are particularly altered by agents known to extract peripheral proteins from biological membranes or to change the conformation of molecular structures.     

PfCRT and the trans-vacuolar proton electrochemical gradient: regulating the access of chloroquine to ferriprotoporphyrin IX

It is accepted that resistance of Plasmodium falciparum to chloroquine (CQ) is caused primarily by mutations in the pfcrt gene. However, a consensus has not yet been reached on the mechanism by which resistance is achieved. CQ-resistant (CQR) parasite lines accumulate less CQ than do CQ-sensitive (CQS) parasites. The CQR phenotype is complex with a component of reduced energy-dependent CQ uptake and an additional component that resembles energy-dependent CQ efflux. Here we show that the required energy input is in the form of the proton electrochemical gradient across the digestive vacuole (DV) membrane. Collapsing the DV proton gradient (or starving the parasites of glucose) results in similar levels of CQ accumulation in CQS and CQR lines. Under these conditions the accumulation of CQ is stimulated in CQR parasite lines but is reduced in CQS lines. Energy deprivation has no effect on the rate of CQ efflux from CQR lines implying that mutant PfCRT does not function as an efflux pump or active carrier. Using pfcrt-modified parasite lines we show that the entire CQ susceptibility phenotype is switched by the single K76T amino acid change in PfCRT. The efflux of CQ in CQR lines is not directly coupled to the energy supply, consistent with a model in which mutant PfCRT functions as a gated channel or pore, allowing charged CQ species to leak out of the DV.     

Very small injected samples to study chloroquine and quinine in human serum using capillary-LC and native fluorescence

A comparison between HPLC with conventional fluorescence detection and capillary-LC (microHPLC) with native laser-induced fluorescence (LIF) detection was done to determine chloroquine (CQ) and quinine (Q) in human serum. HPLC experiments were run with parameters of the conventional fluorimeter set at the highest level of sensitivity. Results were compared with those obtained on microHPLC coupled to a ZETALIF (He-Cd 325 nm) detector which provided a 50-fold increase in sensitivity. In microHPLC-LIF injection volumes were 200 nL instead of 10 microL in conventional HPLC. The separation was completed within 3 min (6 min on HPLC). The limit of detection on microHPLC-LIF was 1.9 and 1.3 fmol for CQ and Q, respectively. Both experiments were validated on serum samples. The mean recovery was more than 95% for CQ and Q. The intra- and inter-day precision and accuracy were found to be within the acceptable limits (<10%).     

Chloroquine and Hydroxychloroquine Increase Retinal Pigment Epithelial Layer Permeability

Antimalarials chloroquine (CQ) and hydroxychloroquine (HCQ) are widely used as antiinflammatory drugs, but side effects include retinopathy and vision loss. The objective of this study was to examine the effect of CQ and HCQ on the barrier integrity of retinal pigment epithelial (RPE) cell monolayers in vitro. Permeability of ARPE‐19 cell monolayers was determined using Fluorescein isothiocyanate (FITC)‐labeled dextran. The influence of CQ and HCQ on cell death and the expression tight junction molecules was examined. CQ and HCQ significantly increased ARPE‐19 monolayer permeability after 3 and 18 h, respectively, and enhanced mRNA levels for claudin‐1 and occludin. Cytotoxicity was only observed after 18 h exposure. Thus, CQ and HCQ rapidly enhance RPE barrier permeability in vitro, independent of cytotoxicity or loss of zonula occludens‐1, claudin‐1, and occludin expression. Our findings suggest that CQ/HCQ‐induced permeability of the RPE layer may contribute to blood–retinal barrier breakdown in case of CQ/HCQ‐induced retinopathy.     

Cellular uptake of chloroquine is dependent on binding to ferriprotoporphyrin IX and is independent of NHE activity in Plasmodium falciparum

Here we provide definitive evidence that chloroquine (CQ) uptake in Plasmodium falciparum is determined by binding to ferriprotoporphyrin IX (FPIX). Specific proteinase inhibitors that block the degradation of hemoglobin and stop the generation of FPIX also inhibit CQ uptake. Food vacuole enzymes can generate cell-free binding, using human hemoglobin as a substrate. This binding accounts for CQ uptake into intact cells and is subject to identical inhibitor specificity. Inhibition of CQ uptake by amiloride derivatives occurs because of inhibition of CQ-FPIX binding rather than inhibition of the Na+/H+ exchanger (NHE). Inhibition of parasite NHE using a sodium-free medium does not inhibit CQ uptake nor does it alter the ability of amilorides to inhibit uptake. CQ resistance is characterized by a reduced affinity of CQ-FPIX binding that is reversible by verapamil. Diverse compounds that are known to disrupt lysosomal pH can mimic the verapamil effect. These effects are seen in sodium-free medium and are not due to stimulation of the NHE. We propose that these compounds increase CQ accumulation and overcome CQ resistance by increasing the pH of lysosomes and endosomes, thereby causing an increased affinity of binding of CQ to FPIX.     

Chloroquine sensitizes breast cancer cells to chemotherapy independent of autophagy

Chloroquine (CQ) is a 4-aminoquinoline drug used for the treatment of diverse diseases. It inhibits lysosomal acidification and therefore prevents autophagy by blocking autophagosome fusion and degradation. In cancer treatment, CQ is often used in combination with chemotherapeutic drugs and radiation because it has been shown to enhance the efficacy of tumor cell killing. Since CQ and its derivatives are the only inhibitors of autophagy that are available for use in the clinic, multiple ongoing clinical trials are currently using CQ or hydroxychloroquine (HCQ) for this purpose, either alone, or in combination with other anticancer drugs. Here we show that in the mouse breast cancer cell lines, 67NR and 4T1, autophagy is induced by the DNA damaging agent cisplatin or by drugs that selectively target autophagy regulation, the PtdIns3K inhibitor LY294002, and the mTOR inhibitor rapamycin. In combination with these drugs, CQ sensitized to these treatments, though this effect was more evident with LY294002 and rapamycin treatment. Surprisingly, however, in these experiments CQ sensitization occurred independent of autophagy inhibition, since sensitization was not mimicked by Atg12, Beclin 1 knockdown or bafilomycin treatment, and occurred even in the absence of Atg12. We therefore propose that although CQ might be helpful in combination with cancer therapeutic drugs, its sensitizing effects can occur independently of autophagy inhibition. Consequently, this possibility should be considered in the ongoing clinical trials where CQ or HCQ are used in the treatment of cancer, and caution is warranted when CQ treatment is used in cytotoxic assays in autophagy research.     

Synthesis and antimalarial activity of new heterocyclic hybrids based on chloroquine and thiazolidinone scaffolds

A series of new 21 chloroquine heterocyclic hybrids containing either benzylamino fragment or N-(aminoalkyl)thiazolidin-4-one moiety were synthesized and screened for their antimalarial activity against chloroquine (CQ)-sensitive 3D7 and multidrug-resistance Dd2 strains of Plasmodium falciparum. Although no compounds more active than CQ against 3D7 was found; against Dd2 strain, six compounds, four of them with benzylamino fragment, showed an excellent activity, up to 3-fold more active than CQ. Non specific cytotoxicity on J774 macrophages was observed in some compounds whereas only two of them showed liver toxicity on HepG2 cells. In addition, all active compounds inhibited the ferriprotoporphyrin IX biocrystalization process in concentrations around to CQ. In vivo preliminary results have shown that at least two compounds are as active as CQ against Plasmodium berghei ANKA.     

Chloroquine sensitizes breast cancer cells to chemotherapy independent of autophagy

Chloroquine (CQ) is a 4-aminoquinoline drug used for the treatment of diverse diseases. It inhibits lysosomal acidification and therefore prevents autophagy by blocking autophagosome fusion and degradation. In cancer treatment, CQ is often used in combination with chemotherapeutic drugs and radiation because it has been shown to enhance the efficacy of tumor cell killing. Since CQ and its derivatives are the only inhibitors of autophagy that are available for use in the clinic, multiple ongoing clinical trials are currently using CQ or hydroxychloroquine (HCQ) for this purpose, either alone, or in combination with other anticancer drugs. Here we show that in the mouse breast cancer cell lines, 67NR and 4T1, autophagy is induced by the DNA damaging agent cisplatin or by drugs that selectively target autophagy regulation, the PtdIns3K inhibitor LY294002, and the mTOR inhibitor rapamycin. In combination with these drugs, CQ sensitized to these treatments, though this effect was more evident with LY294002 and rapamycin treatment. Surprisingly, however, in these experiments CQ sensitization occurred independent of autophagy inhibition, since sensitization was not mimicked by Atg12, Beclin 1 knockdown or bafilomycin treatment, and occurred even in the absence of Atg12. We therefore propose that although CQ might be helpful in combination with cancer therapeutic drugs, its sensitizing effects can occur independently of autophagy inhibition. Consequently, this possibility should be considered in the ongoing clinical trials where CQ or HCQ are used in the treatment of cancer, and caution is warranted when CQ treatment is used in cytotoxic assays in autophagy research.     

Multiple transporters associated with malaria parasite responses to chloroquine and quinine

Mutations and/or overexpression of various transporters are known to confer drug resistance in a variety of organisms. In the malaria parasite Plasmodium falciparum, a homologue of P-glycoprotein, PfMDR1, has been implicated in responses to chloroquine (CQ), quinine (QN) and other drugs, and a putative transporter, PfCRT, was recently demonstrated to be the key molecule in CQ resistance. However, other unknown molecules are probably involved, as different parasite clones carrying the same pfcrt and pfmdr1 alleles show a wide range of quantitative responses to CQ and QN. Such molecules may contribute to increasing incidences of QN treatment failure, the molecular basis of which is not understood. To identify additional genes involved in parasite CQ and QN responses, we assayed the in vitro susceptibilities of 97 culture-adapted cloned isolates to CQ and QN and searched for single nucleotide polymorphisms (SNPs) in DNA encoding 49 putative transporters (total 113 kb) and in 39 housekeeping genes that acted as negative controls. SNPs in 11 of the putative transporter genes, including pfcrt and pfmdr1, showed significant associations with decreased sensitivity to CQ and/or QN in P. falciparum. Significant linkage disequilibria within and between these genes were also detected, suggesting interactions among the transporter genes. This study provides specific leads for better understanding of complex drug resistances in malaria parasites.     

The potentiating action of tetrandrine in combination with chloroquine or qinghaosu against chloroquine-sensitive and resistant falciparum malaria

Using chloroquine-sensitive (CS) and chloroquine-resistant (CR) strains of Plasmodium falciparum in vitro, interactions between tetrandrine (TT) and either chloroquine (CQ) or qinghaosu (QHS, artemisinin) were assessed using isobolograms. Sums of the fractional inhibitory concentration for the combination of the two drugs are less than one and therefore, we can conclude that in vitro TT and CQ or QHS act synergistically against CS and CR falciparum malaria. Remarkably, using CR malaria, TT can lower the IC50 dose of CQ as much as 40 fold. These drug combinations may impair the advantage that the development of CQ resistance conveys on the parasite.     

Efficacy of chloroquine plus primaquine treatment and pfcrt mutation in uncomplicated falciparum malaria patients in Rangamati, Bangladesh

A combination of chloroquine (CQ) and primaquine (PQ) had been used as the first-line treatment of uncomplicated Plasmodium falciparum malaria in Rangamati, Bangladesh until the end of 2004. Doctors or medical staffs had felt that CQ plus PQ had become less effective against uncomplicated falciparum malaria patients, but that it was more effective against the minority-indigenous patients than the Bengali patients. The efficacy of CQ plus PQ and the mutation status of the CQ resistance transporter (pfcrt) gene of infecting P. falciparum were, thus, investigated for 45 uncomplicated falciparum malaria patients in Rangamati in 2004. The total failure rate was 57.8%. One or two pfcrt sequences (CIETH and SMNTH at positions 72, 74-76, and 97, mutation underlined) with K76T mutation known to be related to CQ-resistant phenotype were detected in 38 patients' blood samples. Of the 38 patients, in total 15 patients (14/25 minority-indigenous and 1/13 Bengali patients) resulted in adequate clinical and parasitological response (ACPR). There was a statistically significant difference in ACPR rate between the minority-indigenous patients and the Bengali patients. P. falciparum with mutant or resistant pfcrt (pfcrt-resistant) was detected by PCR in blood samples on day 28 for 10 ACPR minority-indigenous patients but not for the only one Bengali ACPR patient, who all were infected with pfcrt-resistant P. falciparum on day 0. The minority-indigenous patients, but not Bengalis, are suggested to be often cured by CQ plus PQ, leaving a very few parasites detectable only by PCR, even when they are infected with pfcrt-resistant P. falciparum.     

Inhibition of ethinyloestradiol and tolbutamide metabolism by quinoline derivatives in vitro

The effects of the quinoline derivatives amodiaquine (AQ), chloroquine (CQ), mefloquine (MQ), primaquine (PQ), quinine (Q) and quinidine (QD) on in vitro hepatic metabolism has been studied using as substrates ethinyloestradiol (EE2) and tolbutamide (TOL). The 2-hydroxylation of EE2 and the hydroxylation of TOL were determined in the presence of variable concentrations of each compound. MQ, PQ, AQ and Q significantly inhibited EE2 metabolism at each of the concentrations studied (0.1, 0.2 and 0.5 mM) as shown by an increase in the percentage of unmetabolised EE2. QD significantly inhibited metabolism at 0.2 and 0.5 mM but CQ was without effect. In terms of recovery of 2-OHEE2, PQ was the most potent inhibitor. At an inhibitor concentration of 0.5 mM the order of potency was PQ greater than or equal to MQ greater than or equal to Q greater than or equal to QD greater than or equal to AQ greater than or equal to CQ. TOL hydroxylase activity in control microsomes was 1.52 +/- 0.33 nmol. min-1 X mg protein-1. The order of potency of the inhibitors (0.5 mM) was PQ greater than or equal to MQ greater than or equal to Q greater than or equal to QD greater than or equal to AQ greater than or equal to CQ. These data provide further evidence of the inhibitory potential of some of the quinoline derivatives. PQ, MQ, and to a lesser extent Q produce the most marked inhibitory effects. QD and AQ are of intermediate potency and CQ is essentially non-inhibitory.     

Radioiodinated clioquinol as a biomarker for beta-amyloid: Zn complexes in Alzheimer's disease

Neocortical beta-amyloid (Abeta) aggregates in Alzheimer's disease (AD) are enriched in transition metals that mediate assembly. Clioquinol (CQ) targets metal interaction with Abeta and inhibits amyloid pathology in transgenic mice. Here, we investigated the binding properties of radioiodinated CQ ([(125)I]CQ) to different in vitro and in vivo Alzheimer models. We observed saturable binding of [(125)I]CQ to synthetic Abeta precipitated by Zn(2+) (K(d)=0.45 and 1.40 nm for Abeta(1-42) and Abeta(1-40), respectively), which was fully displaced by free Zn(2+), Cu(2+), the chelator DTPA (diethylene triamine pentaacetic acid) and partially by Congo red. Sucrose density gradient of post-mortem AD brain indicated that [(125)I]CQ concentrated in a fraction enriched for both Abeta and Zn, which was modulated by exogenous addition of Zn(2+) or DTPA. APP transgenic (Tg2576) mice injected with [(125)I]CQ exhibited higher brain retention of tracer compared to non-Tg mice. Autoradiography of brain sections of these animals confirmed selective [(125)I]CQ enrichment in the neocortex. Histologically, both thioflavine-S (ThS)-positive and negative structures were labeled by [(125)I]CQ. A pilot SPECT study of [(123)I]CQ showed limited uptake of the tracer into the brain, which did however, appear to be more rapid in AD patients compared to age-matched controls. These data support metallated Abeta species as the neuropharmacological target of CQ and indicate that this drug class may have potential as in vivo imaging agents for Alzheimer neuropathology.     

Clioquinol inhibits peroxide-mediated toxicity through up-regulation of phosphoinositol-3-kinase and inhibition of p53 activity

A growing body of evidence supports a central role for biometals in neurodegenerative disorders. Biometals induce oxidative stress through the generation of reactive oxygen species and contribute to neuronal cell dysfunction in Alzheimer's disease (AD), prion disorders and Parkinson's disease (PD). Therapies based on modulation of biometal metabolism are currently being developed and the metal ligand, 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol or CQ) has been investigated for the treatment of AD. CQ has also shown therapeutic benefits in an animal model of PD. However, little is known about the neuroprotective processes of CQ in vivo. In this study, we examined the effect of CQ in BE(2)-M17 human neuroblastoma cells exposed to increased oxidative stress (hydrogen peroxide (H2O2) treatment). Although CQ alone induced a moderate toxic effect on cells, when added to H2O2-treated M17 cells, CQ induced a significant inhibition of H2O2 toxicity. This correlated with up-regulation of phosphoinositol-3-kinase (PI3K) activity in CQ-treated cells. The protective action of CQ was not observed in murine N2a neuroblastoma cells treated with H2O2 and this cell-line did not reveal CQ-mediated increases in PI3K activation. The protective effect was specific for CQ and was not induced by a number of different metal ligands. Inhibition of PI3K activity with LY294002 prevented CQ protection against H2O2 toxicity, demonstrating a crucial role for CQ activation of PI3K in protection against oxidative stress. Furthermore, CQ inhibited H2O2-mediated up-regulation of p53 activity in the M17 cells and this was dependent on PI3K activation. Our studies demonstrate that in human M17 cells, CQ can protect against oxidative stress by activating the PI3K-dependent survival pathway and blocking p53-mediated cell death. These findings have important implications for the development of protective metal ligand-based therapies for treatment of disorders involving oxidative stress.     

Glutathione is involved in the antimalarial action of chloroquine and its modulation affects drug sensitivity of human and murine species of Plasmodium

Ferriprotoporphyrin IX (FP) is released inside the food vacuole of the malaria parasite during the digestion of host cell hemoglobin. FP is detoxified by its biomineralization to hemozoin. This process is effectively inhibited by chloroquine (CQ) and amodiaquine (AQ). Undegraded FP accumulates in the membrane fraction and inhibits enzymes of infected cells in parallel with parasite killing. FP is demonstrably degraded by reduced glutathione (GSH) in a radical-mediated mechanism. This degradation is inhibited by CQ and AQ in a competitive manner, thus explaining the ability of increased GSH levels in Plasmodium falciparum-infected cells to increase resistance to CQ and vice versa, and to render Plasmodium berghei that were selected for CQ resistance in vivo sensitive to the CQ when glutathione synthesis is inhibited. Some over-the-counter drugs that are known to reduce GSH in body tissues when used in excess were found to enhance the antimalarial action of CQ and AQ in mice infected either with P. berghei or Plasmodium vinckei. In contrast, N-acetyl-cysteine which is expected to increase the cellular levels of GSH, antagonized the action of CQ. These results suggest that some over-the-counter drugs can be used in combination with some antimalarials to which the parasite has become resistant.     

Autophagy inhibition enhances vorinostat‐induced apoptosis via ubiquitinated protein accumulation

Autophagy is an evolutionarily conserved cell survival pathway that enables cells to recoup ATP and other critical biosynthetic molecules during nutrient deprivation or exposure to hypoxia, which are hallmarks of the tumour microenvironment. Autophagy has been implicated as a potential mechanism of resistance to anticancer agents as it can promote cell survival in the face of stress induced by chemotherapeutic agents by breaking down cellular components to generate alternative sources of energy. Disruption of autophagy with chloroquine (CQ) induces the accumulation of ubiquitin‐conjugated proteins in a manner similar to the proteasome inhibitor bortezomib (BZ). However, CQ‐induced protein accumulation occurs at a slower rate and is localized to lysosomes in contrast to BZ, which stimulates rapid buildup of ubiquitinated proteins and aggresome formation in the cytosol. The histone deacetylase (HDAC) inhibitor vorinostat (VOR) blocked BZ‐induced aggresome formation, but promoted CQ‐mediated ubiquitinated protein accumulation. Disruption of autophagy with CQ strongly enhanced VOR‐mediated apoptosis in colon cancer cells. Accordingly, knockdown of the essential autophagy gene Atg7 also sensitized cells to VOR‐induced apoptosis. Knockdown of HDAC6 greatly enhanced BZ‐induced apoptosis, but only marginally sensitized cells to CQ. Subsequent studies determined that the CQ/VOR combination promoted a large increase in superoxide generation that was required for ubiquitinated protein accumulation and cell death. Finally, treatment with the CQ/VOR combination significantly reduced tumour burden and induced apoptosis in a colon cancer xenograft model. Collectively, our results establish that inhibition of autophagy with CQ induces ubiquitinated protein accumulation and VOR potentiates CQ‐mediated aggregate formation, superoxide generation and apoptosis.