Re-evaluation of the mutagenic potential of quinacrine dihydrochloride dihydrate

Quinacrine-CASIN combination overcomes chemoresistance in human acute lymphoid leukemia

Chemoresistance posts a major hurdle for treatment of acute leukemia. There is increasing evidence that prolonged and intensive chemotherapy often fails to eradicate leukemic stem cells, which are protected by the bone marrow niche and can induce relapse. Thus, new therapeutic approaches to overcome chemoresistance are urgently needed. By conducting an ex vivo small molecule screen, here we have identified Quinacrine (QC) as a sensitizer for Cytarabine (AraC) in treating acute lymphoblastic leukemia (ALL). We show that QC enhances AraC-mediated killing of ALL cells, and subsequently abrogates AraC resistance both in vitro and in an ALL-xenograft model. However, while combo AraC+QC treatment prolongs the survival of primary transplanted recipients, the combination exhibits limited efficacy in secondary transplanted recipients, consistent with the survival of niche-protected leukemia stem cells. Introduction of Cdc42 Activity Specific Inhibitor, CASIN, enhances the eradication of ALL leukemia stem cells by AraC+QC and prolongs the survival of both primary and secondary transplanted recipients without affecting normal long-term human hematopoiesis. Together, our findings identify a small-molecule regimen that sensitizes AraC-mediated leukemia eradication and provide a potential therapeutic approach for better ALL treatment.

Reversible inhibition of sperm under guidance as an intratubular and reversible contraception in female rats: An experimental study

Background

Reversible inhibition of sperm under guidance (“RISUGⓇ”) is a promising intravasal male contraceptive.

Objective

An exploratory study was conducted with a concept of non-invasive, transcervical, single-intervention and reversible contraception using RISUGⓇ in females.

Materials and Methods

In this experimental study, 60 adult Wistar albino female rats weighing 150-155 g, 3-4 months old were divided into four groups: group I: sham-operated control; group II: tubal occlusion with RISUG for 90 days; group III: tubal occlusion with RISUGⓇ for 90 days and reversal with dimethyl sulphoxide and group IV: tubal occlusion with RISUGⓇ for 90 days and reversal with 5% NaHCO. Animals were subjected to bilateral fallopian tube occlusion with RISUGⓇ and reversal with DMSO and NaHCO3. The estrous cycle, fertility and histology of fallopian tube were evaluated.

Results

Group I showed 100% fertility during all mating schedules. Animals of experimental groups indicated positive mating, but 0% fertility was evident following 30, 60, and 90 days of tubal occlusion. However, after reversal, fertility steadily increased to normalcy in groups III (50% at 45 days, 80% at 105 days, 100% at 150 and 195 days) and IV (70% at 45 and 105 days, 100% at 150 and 195 days) animals. Group II illustrated disorganized inner cell linings and eosinated RISUGⓇimplant-filled lumen. Reversal groups (III and IV) revealed complete restoration of cellular histo-architecture. Regular estrous cycle was noticed in all experimental groups.

Conclusion

RISUGⓇ is suitable for single intervention, intratubular, reversible contraception in female rats.

Multiple-endpoint in vitro carcinogenicity test in human cell line TK6 distinguishes carcinogens from non-carcinogens and highlights mechanisms of action

Current in vitro genotoxicity tests can produce misleading positive results, indicating an inability to effectively predict a compound's subsequent carcinogenic potential in vivo. Such oversensitivity can incur unnecessary in vivo tests to further investigate positive in vitro results, supporting the need to improve in vitro tests to better inform risk assessment. It is increasingly acknowledged that more informative in vitro tests using multiple endpoints may support the correct identification of carcinogenic potential. The present study, therefore, employed a holistic, multiple-endpoint approach using low doses of selected carcinogens and non-carcinogens (0.001-770 µM) to assess whether these chemicals caused perturbations in molecular and cellular endpoints relating to the Hallmarks of Cancer. Endpoints included micronucleus induction, alterations in gene expression, cell cycle dynamics, cell morphology and bioenergetics in the human lymphoblastoid cell line TK6. Carcinogens ochratoxin A and oestradiol produced greater Integrated Signature of Carcinogenicity scores for the combined endpoints than the "misleading" in vitro positive compounds, quercetin, 2,4-dichlorophenol and quinacrine dihydrochloride and toxic non-carcinogens, caffeine, cycloheximide and phenformin HCl. This study provides compelling evidence that carcinogens can successfully be distinguished from non-carcinogens using a holistic in vitro test system. Avoidance of misleading in vitro outcomes could lead to the reduction and replacement of animals in carcinogenicity testing.

A Unified Approach to Targeting the Lysosome's Degradative and Growth Signaling Roles

Lysosomes serve dual roles in cancer metabolism, executing catabolic programs (i.e., autophagy and macropinocytosis) while promoting mTORC1-dependent anabolism. Antimalarial compounds such as chloroquine or quinacrine have been used as lysosomal inhibitors, but fail to inhibit mTOR signaling. Further, the molecular target of these agents has not been identified. We report a screen of novel dimeric antimalarials that identifies dimeric quinacrines (DQ) as potent anticancer compounds, which concurrently inhibit mTOR and autophagy. Central nitrogen methylation of the DQ linker enhances lysosomal localization and potency. An in situ photoaffinity pulldown identified palmitoyl-protein thioesterase 1 (PPT1) as the molecular target of DQ661. PPT1 inhibition concurrently impairs mTOR and lysosomal catabolism through the rapid accumulation of palmitoylated proteins. DQ661 inhibits the in vivo tumor growth of melanoma, pancreatic cancer, and colorectal cancer mouse models and can be safely combined with chemotherapy. Thus, lysosome-directed PPT1 inhibitors represent a new approach to concurrently targeting mTORC1 and lysosomal catabolism in cancer.Significance: This study identifies chemical features of dimeric compounds that increase their lysosomal specificity, and a new molecular target for these compounds, reclassifying these compounds as targeted therapies. Targeting PPT1 blocks mTOR signaling in a manner distinct from catalytic inhibitors, while concurrently inhibiting autophagy, thereby providing a new strategy for cancer therapy. Cancer Discov; 7(11); 1266-83. ©2017 AACR.See related commentary by Towers and Thorburn, p. 1218This article is highlighted in the In This Issue feature, p. 1201.

Endometrial abnormalities on transvaginal ultrasonography and histopathology in women after quinacrine sterilization

OBJECTIVE

To describe endometrial abnormalities on transvaginal ultrasonography and histopathology in women after quinacrine sterilization.

METHODS

It was an analytical cross sectional study conducted during February 2012 to April 2013. The sample size calculated at 95% confidence level was 540. Sampling technique used was simple random sampling. The medical history, examination, transvaginal ultrasonography and biopsy of suspected lesion was performed in quinacrine sterilized women.

RESULTS

The calculation of statistics showed the mean age at quinacrine sterilization was 38.5 years, standard deviation 6.517, and standard error 0.461. The endometrium was regular and smooth with homogenous images in 86% (n= 466), irregular endometrium with heterogeneous images on transvaginal ultrasound in 9.4% (n =51) and endometrial growth with high level echoes in 4.2% women (n= 23). The histological findings included hyperplasia and well differentiated adenocarcinoma in two patients respectively.

CONCLUSION

The irregular endometrium, adhesions, and growths were found after quinacrine sterilization. The risk of endometrial growth was more after 10 years duration of quinacrine sterilization.

Quinacrine has anticancer activity in breast cancer cells through inhibition of topoisomerase activity

The small molecule Quinacrine (QC, a derivative of 9-aminoacridine), an anti-malaria drug, displays activity against cancer cell lines and can simultaneously suppress nuclear factor-κB (NF-κB) and activate p53 signaling. In this study, we investigated the anticancer mechanism underlying these drug activities in breast cancer cell lines. QC caused a dose-dependent decrease of both anchorage dependent and independent growth of breast cancer cells (MCF-7 and MDA-MB-231) without affecting normal breast epithelial cells (MCF-10A), as evident from clonogenic cell survival, [3-(4,5-dimethylthiazol-2yl-)-2,5-diphenyl tetrazolium bromide] viability, wound healing and soft agar growth. QC activated the proapoptotic marker Bax, PARP cleavage, p53 and its downstream target, p21 (Cip1/Waf1) and downregulated the antiapoptotic marker Bcl-xL and relative luciferase activity of NF-κB in MCF-7 cells. Results of DAPI nuclear staining and FACS analysis show that QC increased apoptosis in a dose-dependent manner. QC caused apoptosis by increasing the cell population in S-phase and simultaneously decreasing the G1 and G2/M populations. A dose-dependent increase of DNA damage as measured by the comet assay was seen in MCF-7 cells after exposure to QC. With regards to the mechanism of DNA damage, we found that QC inhibited topoisomerase activity in MCF-7 cells by increasing the unwinding of supercoiled DNA. Collectively, the results demonstrate that QC has efficient anticancer potential against breast cancer cells via not only an induction of p53 and p21 but also an induction of S phase arrest, DNA damage and inhibition of topoisomerase activity.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

New hopes from old drugs: revisiting DNA-binding small molecules as anticancer agents

Most of the anticancer chemotherapeutic drugs that are broadly and successfully used today are DNA-damaging agents. Targeting of DNA has been proven to cause relatively potent and selective destruction of tumor cells. However, the clinical potential of DNA-damaging agents is limited by the adverse side effects and increased risk of secondary cancers that are consequences of the agents' genotoxicity. In this review, we present evidence that those agents capable of targeting DNA without inducing DNA damage would not be limited in these ways, and may be as potent as DNA-damaging agents in the killing of tumor cells. We use as an example literature data and our own research of the well-known antimalarial drug quinacrine, which binds to DNA without inducing DNA damage, yet modulates a number of cellular pathways that impact tumor cell survival.

Enhancement of the recombinagenic and mutagenic activities of bleomycin in yeast by intercalation of acridine compounds into DNA

Strain D7 of Saccharomyces cerevisiae was used to measure the induction by bleomycin (BLM) of mitotic recombination at the trp5 locus and point mutations at ilv1 in the presence and absence of acridine compounds. BLM is a potent mutagen and recombinagen in the D7 assay. The acridines vary, some being mutagenic or recombinagenic and others not. Combined treatments were used to distinguish whether a genetically inactive acridine has no effect on the genetic activity of BLM or modulates its action. When an acridine is itself genetically active, combined treatments were used to determine whether its effects are additive with those of BLM or whether there is interaction between the two compounds. Acridine compounds that share the ability to intercalate between the base pairs of DNA but differ in their mutagenic specificity owing to the presence of different substituent groups were analysed. Clear potentiation and synergistic interactions were detected in combined treatments with BLM and aminoacridines, nitroacridines or an acridine mustard. Potentiation and synergy were also observed in sequential exposures in which the yeast were grown in the presence of acridine compounds and then treated with BLM in the absence of free acridine. The results are consistent with an increase in BLM susceptibility conferred by acridine intercalation. It is likely that the intercalating agents increase the access of BLM to the minor groove of DNA, where it abstracts a hydrogen from the 4' position of deoxyribose, creating a free radical that is processed into strand breaks.

Inhibition of rat hepatic CYP2E1 by quinacrine: molecular modeling investigation and effects on 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mutagenicity

Increased activity of CYP2E1 has been associated with increased risk of chemically-mediated cancers, through enhanced activation of a variety of procarcinogens. In this context, inhibition of CYP2E1 is potentially of significance in xenobiotic toxicity. The aim of the present study was to test the hypothesis that quinacrine inhibits hepatic CYP2E1. For this purpose, disulfiram (75 mg/kg i.p) as an inhibitor and isoniazid (100 mg/kg i.p) as an inducer of CYP2E1, as well as quinacrine (50 mg/kg i.p) were administered to Wistar rats and the hepatic activity of CYP2E1 was measured. The expression of CYP2E1 was further assessed by Western blot analysis. As expected, disulfiram inhibited, while isoniazid induced the activity and expression of the enzyme. Interestingly, treatment with quinacrine resulted in a significant decrease of CYP2E1 activity and expression. To investigate any similarities in the inhibition of CYP2E1 by quinacrine and disulfiram, molecular modeling techniques were adopted and revealed that quinacrine molecule anchors inside the same binding pocket of the protein where disulfiram is also attached. Finally, as assessed by the sister chromatid exchanges (SCE) assay, quinacrine was demonstrated to reduce the mutagenic effects of the tobacco-specific N-nitrosamine 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is known to be converted to active mutagen in the liver principally through CYP2E1. We suggest that these antimutagenic effects of quinacrine could be possibly attributed, at least in part, to its ability to block the bioactivation of NNK, mainly by the inhibition of CYP2E1. Our results, even preliminary, indicate that quinacrine as an inhibitor of CYP2E1 might be protective against chemically-induced toxicities such as NNK-induced mutagenicity.

DNA-damaging activity and mutagenicity of 16 newly synthesized thiazolo[5,4-a]acridine derivatives with high photo-inducible cytotoxicity

The discovery of the potent anticancer properties of natural alkaloids in the pyrido-thiazolo-acridine series has suggested that thiazolo-acridine derivatives could be of great interest. In a continuous attempt to develop DNA-binding molecules and DNA photo-cleavers, 16 new thiazolo[5,4-a]acridines were synthesized and studied for their photo-inducible DNA-intercalative, cytotoxic and mutagenic activities, by use of the DNA methyl-green bioassay, the Alamar Blue viability assay and the Salmonella mutagenicity test using strains TA97a and TA98 with and without metabolic activation and photo-activation. Without photo-activation, one compound showed a DNA-intercalative activity in the DNA major groove while three compounds displayed intercalating properties after photo-activation. In the dark, four molecules possessed cytotoxic activities against a THP1 acute monocytic leukemia cell line while 15 derivatives displayed photo-inducible cytotoxic activity against this cell line. All compounds were mutagenic in strain TA97a with metabolic activation (+S9mix) and 15 molecules were mutagenic in strain TA98 without activation (-S9mix). Study of the quantitative structure-activity relationships (QSAR) from the Salmonella mutagenicity data revealed that several descriptors could describe cytotoxic and mutagenic activities after photo-activation. From the results of the mutagenicity test, four compounds with elevated mutagenic activities were selected for additional experiments. Their capacities to induce single-strand breaks (SSB) and chromosome-damaging effects were monitored by the comet and the micronucleus assays in normal human keratinocytes. Comparison of the minimal genotoxic concentrations showed that two compounds possessed higher capacities to induce SSB after photo-activation. In the micronucleus assay, three molecules were able to induce high numbers of micronuclei following photo-activation. Overall, the results of this study confirm that acridines are predominantly genotoxic via a DNA-intercalating mechanism in the dark, while DNA-adducts were probably induced following photo-activation.

Genotoxicity of non-covalent interactions: DNA intercalators

This review provides an update on the mutagenicity of intercalating chemicals, as carried out over the last 17 years. The most extensively studied DNA intercalating agents are acridine and its derivatives, that bind reversibly but non-covalently to DNA. These are frameshift mutagens, especially in bacteria and bacteriophage, but do not otherwise show a wide range of mutagenic properties. Di-acridines or di-quinolines may be either mono- or bis-intercalators, depending upon the length of the alkyl chain separating the chromophores. Those which monointercalate appear as either weak frameshift mutagens in bacteria, or as non-mutagens. However, some of the bisintercalators act as "petite" mutagens in Saccharomyces cerevisiae, suggesting that they may be more likely to target mitochondrial as compared with nuclear DNA. Some of the new methodologies for detecting intercalation suggest this may be a property of a wider range of chemicals than previously recognised. For example, quite a number of flavonoids appear to intercalate into DNA. However, their mutagenic properties may be dominated by the fact that many of them are also able to inhibit topoisomerase II enzymes, and this property implies that they will be potent recombinogens and clastogens. DNA intercalation may serve to position other, chemically reactive molecules, in specific ways on the DNA, leading to a distinctive (and wider) range of mutagenic properties, and possible carcinogenic potential.

A one-year neonatal mouse carcinogenesis study of quinacrine dihydrochloride

Quinacrine is an acridine derivative under investigation for its use in nonsurgical female sterilization. Safety issues regarding the carcinogenic potential of quinacrine have been raised because it is mutagenic and clastogenic in vitro. The objective of the study was to evaluate the carcinogenic potential of quinacrine dihydrochloride (quinacrine) in neonatal mice treated with single intraperitoneal doses on postpartum days 8 and 15 and observed for 52 weeks. Neonatal Crl: CD-1 mice of each sex were randomly allocated into four treatment groups (0, 10, 50, and 150 mg/kg), dosed twice with quinacrine suspended in carboxymethylcellulose, observed for 52 weeks post dose, and then euthanized, necropsied, and subjected to a full histopathological examination. In male mice, tumor incidence was not significantly increased at any site at any dose level. In female mice, the incidence of benign uterine endometrial stromal polyps was slightly greater at the mid and high dose (> or = 50 mg/kg), as was the incidence of endometrial hyperplasia. The incidence of polyps in these groups was not significantly greater than in controls by pair-wise comparison but was significantly greater (p = .042) by the linear trend test. The authors conclude that quinacrine administered twice to neonatal mice may have enhanced or accelerated the development of endometrial hyperplasia and uterine stromal polyps at higher doses. Because uterine stromal polyps are a commonly observed benign tumor in older mice, the significance of this finding is unclear and will require a weight of evidence evaluation for a conclusion on the carcinogenic potential of quinacrine.

Frameshift mutations induced by three classes of acridines in the lacZ reversion assay in Escherichia coli: potency of responses and relationship to slipped mispairing models

The frameshift mutagenicity of 9-aminoacridine (9AA) was compared with that of quinacrine, the acridine mustards ICR-191 and quinacrine mustard (QM), and the nitroacridine Entozon in the lacZ reversion assay in Escherichia coli. As intercalating agents, 9AA and quinacrine cause mutations through noncovalent associations with DNA. Mustards and nitroacridines form covalent adducts in DNA and give rise to different spectra of mutations. Quinacrine and 9AA most effectively induced -1 frameshifts in a run of guanine residues, with 9AA being the more potent mutagen. They also induced +G frameshifts. The acridine mustard ICR-191 was a stronger mutagen than 9AA, owing largely to its potent induction of +G frameshifts. QM induced +G frameshifts more strongly than did its nonreactive counterpart quinacrine. The nitroacridine Entozon differed from the other acridines in being a potent inducer of -2 frameshifts, but it was less effective in inducing +/-1 frameshifts. Quinacrine, although a simple intercalator, induced all five kinds of frameshift mutations detected in the assay, as did the acridine mustards. Although +A and -A frameshifts were induced, adenine runs were less susceptible to acridine mutagenesis than guanine runs. The patterns of frameshift mutagenicity in the lacZ assay are similar to those in an assay based on the reversion of mutations in the tetracycline-resistance gene of the plasmid pBR322. The similarity suggests that the responses reflect the inherent bacterial mutagenicity of the compounds in the local sequence context and are not highly dependent on the broader sequence context. The results are interpreted with respect to slipped mispairing models of frameshift mutagenesis.

Non-surgical female sterilization with quinacrine: an update

The intrauterine installation of quinacrine represents a simple, inexpensive, effective, and seemingly safe method of non-surgical female sterilization. Existing clinical data on its use are very encouraging: Results of a large study conducted in Vietnam with an overall sample of over 30,000 women showed high effectiveness; in addition, when a retrospective study was conducted in these women, cumulative 5-year pregnancy rates were estimated to be 13% in women younger than 35 years and 6.8% in the women older than 35. Overall, failure rates with quinacrine have been estimated, at 10 years, to be between 1.9 and 4 times higher than those obtainable with conventional surgical procedures of tubal interruption. Unfortunately, existing toxicology for topical use of quinacrine pellets is incomplete. This prompted an expert group convened by WHO, to comment, in 1994, that the toxicology of locally applied quinacrine is inadequate. To counter this statement the proponents of the method argue that it is unfair to apply the stringent pre-clinical requirements that are mandatory in the industrialized world, to methods utilized in countries plagued by both high fertility and high maternal mortality. This controversy will soon be resolved since conventional toxicological evaluation is now underway. In conclusion, the future of quinacrine for non-surgical female sterilization will depend on the results of long-term animal studies, as well as the retrospective human studies now being carried out.