Examination of novel 4-aminoquinoline derivatives designed and synthesized by a hybrid pharmacophore approach to enhance their anticancer activities.

In an attempt to develop effective and potentially safe anticancer agents, thirty-six 4-aminoquinoline derived sulfonyl analogs were designed and synthesized using a hybrid pharmacophore approach. The cytotoxicity of these compounds was determined using three breast tumor cell lines (MDA-MB231, MDA-MB468 and MCF7) and two matching non-cancer breast epithelial cell lines (184B5 and MCF10A). Although most of the compounds were quite effective on the breast cancer cells, the compound 7-chloro-4-(4-(2,4-dinitrophenylsulfonyl)piperazin-1-yl)quinoline (13; VR23) emerged as potentially the most desirable one in this series of compounds. Data from the NCI-60 cancer panel screening show that compound 13 is effective on a wide range of different cancers. Importantly, compound 13 is needed up to 17.6-fold less doses to achieve the same IC50 against cancer than non-cancer cells (MDA-MB468 vs MCF10A), suggesting that it can potentially be less toxic to normal cells. Cancer cells formed multiple centrosomes in the presence of compound 13, resulting in the cell cycle arrest at prometa-meta phase. This abnormality leads to eventual cell demise with sub-G1 DNA content typically shown with apoptotic cells. In addition, compound 13 also causes an increase in lysosomal volume in cancer but not in non-cancer cells, which may contribute at least in part to its preferential cancer cell-killing. The cancer cell-killing effect of compound 13 is highly potentiated when combined with either bortezomib or monastrol.

An overview of quinazolines: Pharmacological significance and recent developments.

Most of the drugs and pharmacologically relevant molecules possess heterocyclic ring structures and presence of hetero atoms or groupings divulges privileged specificities in their pharmacological targets. Especially the heterocyclic systems, quinazoline is a biologically imperative scaffold known to be linked with several pharmacological activities. Some of the protuberant pharmacological responses attributed to this system are analgesic, anti-inflammatory, anti-convulsant, sedative-hypnotic, anti-histaminic, anti-hypertensive, anti-cancer, anti-microbial, anti-tubercular and anti-viral activities. This multiplicity in the pharmacological response contours of quinazoline has attracted the consideration of medicinal chemists to explore this system to its multiple potential against numerous activities. Several of these synthetic and pharmacological investigations have been successively studied for structure-activity relationship (SAR) to correlate the particular structural features for their pharmacological target. The emerging understanding of quinazoline derivatives on their pharmacological target offer opportunities for novel therapeutics. This review principally emphases on the medicinal chemistry aspects including drug design, structure-activity relationships (SARs), and mechanism of actions of quinazoline derivatives. This review gives detailed attention on in vitro and in vivo pharmacological activities of quinazoline and its analogs in the perspective of drug discovery and its development.

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.

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.

Investigating the Role of Loop C Hydrophilic Residue 'T244' in the Binding Site of ρ1 GABAC Receptors via Site Mutation and Partial Agonism.

The loop C hydrophilic residue, threonine 244 lines the orthosteric binding site of ρ1 GABAC receptors was studied by point mutation into serine, alanine and cysteine, and tested with GABA, some representative partial agonists and antagonists. Thr244 has a hydroxyl group essential for GABA activity that is constrained by the threonine methyl group, orienting it toward the binding site. Significant decreases in activation effects of the studied ligands at ρ1 T244S mutant receptors, suggests a critical role for this residue. Results of aliphatic and heteroaromatic partial agonists demonstrate different pharmacological effects at ρ1 T244S mutant receptors when co-applied with GABA EC50 responses. ρ1 T244A and ρ1 T244C mutant receptors have minimal sensitivity to GABA at high mM concentrations, whereas, the ρ1 WT partial agonists, ß-alanine and MTSEA demonstrate more efficacy and potency, respectively, than GABA at these mutant receptors. This study explores the role of Thr244 in the binding of agonists as an initial step during channel gating by moving loop C towards the ligand.

VR23: A Quinoline-Sulfonyl Hybrid Proteasome Inhibitor That Selectively Kills Cancer via Cyclin E-Mediated Centrosome Amplification.

The proteasome is clinically validated as a target for cancer therapeutics. However, proteasome-inhibitory agents that are cancer selective have yet to be developed. In this study, we report the identification of a safe and effective proteasome inhibitor with selective anticancer properties. We screened a chemical library constructed using a hybrid approach that incorporated a 4-piperazinylquinoline scaffold and a sulfonyl phamarcophore. From this library, we identified 7-chloro-4-(4-(2,4-dinitrophenylsulfonyl)piperazin-1-yl)quinoline (VR23) as a small molecule that potently inhibited the activities of trypsin-like proteasomes (IC50 = 1 nmol/L), chymotrypsin-like proteasomes (IC50 = 50-100 nmol/L), and caspase-like proteasomes (IC50 = 3 µmol/L). Data from molecular docking and substrate competition assays established that the primary molecular target of VR23 was ß2 of the 20S proteasome catalytic subunit. Notably, VR23 was structurally distinct from other known proteasome inhibitors and selectively killed cancer cells by apoptosis, with little effect on noncancerous cells. Mechanistic investigations showed that cancer cells exposed to VR23 underwent an abnormal centrosome amplification cycle caused by the accumulation of ubiquitinated cyclin E. In combinations with the clinically approved chymotrypsin-like proteasome inhibitor bortezomib, VR23 produced a synergistic effect in killing multiple myeloma cells, including those that were resistant to bortezomib. VR23 was effective in vivo in controlling multiple myelomas and metastatic breast cancer cells, in the latter case also enhancing the antitumor activity of paclitaxel while reducing its side effects. Overall, our results identify VR23 as a structurally novel proteasome inhibitor with desirable properties as an anticancer agent.

The potential of quinoline derivatives for the treatment of Toxoplasma gondii infection.

Here we reported our investigation, as part of our drug repositioning effort, on anti-Toxoplasma properties of newly synthesized quinoline compounds. A collection of 4-aminoquinoline and 4-piperazinylquinoline analogs have recently been synthesized for use in cancer chemotherapy. Some analogs were able to outperform chloroquine, a quinoline derivative drug which is commonly used in the treatment of malaria and other parasitic infections. Herein 58 compounds containing one or two quinoline rings were examined for their effectiveness as potential anti-Toxoplasma compounds. Of these 58 compounds, 32 were efficient at inhibiting Toxoplasma growth (IC50<100 µM). Five compounds with single and simple quinoline rings exhibited similar cLogP values of ∼2 and IC50 values between 5 and 6 µM, with one exception of 8-hydroxyquinoline whose IC50 value was 213 nM. The addition of one hydroxyl group at position 8 caused a 40-fold increase in the inhibitory effect of quinoline. A significant improvement in anti-Toxoplasma effect among quinoline derivatives was detected in B11, B12, B23, and B24, whose structures carry two quinoline rings, and their resultant cLogP values are ⩾7. Among these compounds, B23 was the most effective compound with IC50 value of 425±35 nM, and TI value of 4.9. It was also noted that compounds with at least one quinoline ring, displaying anti-Toxoplasma effects were capable of causing the disappearance of the apicoplast, a plastid-like organelle. When treated with quinoline, 8-hydroxyquinoline or B23, 40-45% of the parasites lost their apicoplasts. Our findings recapitulate the properties of quinoline derivatives in diminishing apicoplast. This could aid further investigations of anti-parasitic treatments specific to Apicomplexan. More importantly, B12 and B23 which harbor superior anti-cancer properties than chloroquine, have effective anti-Toxoplasma activity. These compounds therefore have significant potential for future development of chemotherapeutic agents for patients suffering from breast cancers and parasitic infection.

Anti-breast cancer activity of heteroaryl chalcone derivatives.

In an attempt to develop effective anticancer therapeutics, a new series of heteroaryl chalcone compounds were designed, synthesized, and examined for their antiproliferative effects on two breast cancer cell lines and one matching non-cancer breast cell line. The structure-activity relationship (SAR) analysis suggested that the compounds derived from thiophene chalcones (6-17) exhibited generally better antiproliferative activity than those derived from bioisoteric replacement of furan chalcones (18-29) on MDA-MB231 breast cancer cells. In contrast, the compounds derived from furan chalcones showed generally better antiproliferative activity on MDA-MB468 breast cancer cells. Among 24 compounds examined, compounds 21 and 23 showed significantly improved antiproliferative activity against MDA-MB231 and MDA-MB468 cancer cells. However, compound 23 ((E)-1-(4-chlorophenyl)-3-(5-(4-methoxyphenyl)furan-2-yl)prop-2-en-1-one) is considered to be most desirable among this series, since its antiproliferative activity was 3 to 7-fold higher on cancer than non-cancer cells. Compound 23 showed not only more effective activity than the widely prescribed cisplatin on cancer cells, but it also showed differential antiproliferative activity against cancer cells, a property that is not shown with cisplatin. If this property shown in cell culture stands in vivo test, compound 23 can be an effective and safe anticancer drug.

Quinoline as a privileged scaffold in cancer drug discovery.

Quinoline (1-azanaphthalene) is a heterocyclic aromatic nitrogen compound characterized by a double-ring structure that contains a benzene ring fused to pyridine at two adjacent carbon atoms. Quinoline compounds are widely used as "parental" compounds to synthesize molecules with medical benefits, especially with anti-malarial and anti-microbial activities. Certain quinoline-based compounds also show effective anticancer activity. This broad spectrum of biological and biochemical activities has been further facilitated by the synthetic versatility of quinoline, which allows the generation of a large number of structurally diverse derivatives. This includes numerous analogues derived from substitution of the quinoline ring system, and derivatization of quinoline ring structure. Quinoline and its analogs have recently been examined for their modes of function in the inhibition of tyrosine kinases, proteasome, tubulin polymerization and DNA repair. In this review, we have summarized our knowledge on quinoline compounds with respect to their anticancer activities, mechanisms of action, structure-activity relationship (SAR), and selective and specific activity against various cancer drug targets. In particular, we focus our review on in vitro and in vivo anticancer activities of quinoline and its analogs in the context of cancer drug development and refinement.

HAX-1: a family of apoptotic regulators in health and disease.

HAX-1 comprises a family of ubiquitously expressed proteins that play important roles in the regulation of programmed cell death. Herein, we provide a comprehensive review of the expression profile of HAX-1 and its functional implications during health and disease, highlighting its direct involvement in the development of congenital neutropenia and neural abnormalities, when absent, and its contribution to the progression of psoriasis and cancer, when overexpressed. Moreover, we provide new information on the differential expression of the HAX-1 subfamily in three distinct types of epithelial cancers, including breast, skin, and colon. Our results demonstrate a significant up-regulation of the anti-apoptotic HAX-1 variant 001 in skin and colon, but not in breast and cancer cells, indicating tissue-specific differences in its expression pattern and properties during cancer formation and progression. Our findings further reveal a considerable down-regulation, if not abrogation, of three distinct, yet to be characterized, HAX-1 isoforms in breast cancer cells, suggesting that they may function in an opposite manner to the anti-apoptotic variant 001. This study aims to summarize our current knowledge on the physiological implications of the expression profile of the HAX-1 subfamily in health and disease, and provide new information on the differential expression and activities of HAX-1 members in three distinct types of cancer.

Design and synthesis of chloroquine analogs with anti-breast cancer property.

A series of chloroquine (CQ) analogs were designed and synthesized in a repositioning approach to develop compounds with high anti-breast cancer property. The compounds were then examined for their antiproliferative effects on two human breast tumor cell lines and a matching non-cancer cell line. Although many of them showed substantial antiproliferative effects on breast cancer cells examined, two compounds, 7-chloro-N-(3-(4-(7-(trifluoromethyl)quinolin-4-yl)piperazin-1-yl)propyl)quinolin-4-amine (14) and {3-[4-(7-chloro-quinolin-4-yl)-piperazin-1-yl]-propyl}-(7-trifluoromethyl-quinolin-4-yl)-amine (26), emerged as the most active among this series. They were particularly potent against MCF7 cells when compared to CQ and cisplatin, a widely prescribed anti-cancer drug. The results suggest that these CQ analogs could serve as bases for the development of a new group of effective cancer chemotherapeutics.

Design and synthesis of anti-breast cancer agents from 4-piperazinylquinoline: a hybrid pharmacophore approach.

A novel class of 4-piperazinylquinoline derivatives based on the isatin scaffold were designed by molecular hybridization approach and synthesized for biological evaluation. Subsequently, the compounds were examined for their cytotoxic effects on two human breast tumor cell lines, MDA-MB468 and MCF7, and two non-cancer breast epithelial cell lines, 184B5 and MCF10A. Although all compounds examined were quite effective on the breast cancer cell lines examined, the compound 4-bromo-1-[4-(7-chloro-quinolin-4-yl)-piperazin-1-ylmethyl]-1H-indole-2,3-dione (5b) and N(1)-[4-(7-trifluoromethyl-quinolin-4-yl)]-piperazin-1-ylmethyl-4-chloro-1H-indole-2,3-dione-3-thiosemicarbazone (8a) emerged as the most active among this series. It appeared that both 5b and 8a caused apoptosis to MCF7 cancer cells, but not MCF10A non-cancer cells. Thus, 4-piperazinylquinoline linked isatin analog can serve as the prototype molecule for further development of a new class of anti-breast cancer agents.

A 4-aminoquinoline derivative that markedly sensitizes tumor cell killing by Akt inhibitors with a minimum cytotoxicity to non-cancer cells.

The purpose of this study was to evaluate the enhancement value of chloroquine analogs when used in combination with Akt inhibitors on the MDA-MB468, MDA-MB231 and MCF7 human breast cancer cell lines. The result showed that the combination of certain chloroquine analogs and Akt inhibitors are highly effective. In particular, the chloroquine analog N'-(7-fluoro-quinolin-4-yl)-N,N-dimethyl-ethane-1,2-diamine (compound 5) was highly effective in sensitizing cancer cell killing when combined with either Akt inhibitor 8 (1-{1-[4-(7-phenyl-1H-imidazo[4,5-g]quinoxalin-6-yl)-benzyl]-piperidin-4-yl}-1,3-dihydro-benzoimidazol-2-one) or 9 ([4-(2-chloro-4a,10a-dihydro-phenoxazin-10-yl)-butyl]-diethyl-amine hydrochloride). Importantly, the enhancement of chloroquine analogs 5 on cell killing by Akt inhibitors 8 and 9 was cancer-specific. Thus, this combinational approach is highly promising in controlling tumors with a minimum side effect. Structural analysis of effective and ineffective chloroquine analogs suggests that the 4-aminoquinoline scaffold and lateral side chain of dimethylamino functionality play an important role for the enhancement of cell killing by Akt inhibitors.

Chloroquine and its analogs: a new promise of an old drug for effective and safe cancer therapies.

Chloroquine (CQ), N'-(7-chloroquinolin-4-yl)-N,N-diethyl-pentane-1,4-diamine, is widely used as an effective and safe anti-malarial and anti-rheumatoid agent. CQ was discovered 1934 as "Resochin" by Andersag and co-workers at the Bayer laboratories. Ironically, CQ was initially ignored for a decade because it was considered too toxic to use in humans. CQ was "re-discovered" during World War II in the United States in the course of anti-malarial drug development. The US government-sponsored clinical trials during this period showed unequivocally that CQ has a significant therapeutic value as an anti-malarial drug. Consequently, CQ was introduced into clinical practice in 1947 for the prophylaxis treatment of malaria (Plasmodium vivax, ovale and malariae). CQ still remains the drug of choice for malaria chemotherapy because it is highly effective and well tolerated by humans. In addition, CQ is widely used as an anti-inflammatory agent for the treatment of rheumatoid arthritis, lupus erythematosus and amoebic hepatitis. More recently, CQ has been studied for its potential as an enhancing agent in cancer therapies. Accumulating lines of evidence now suggest that CQ can effectively sensitize cell-killing effects by ionizing radiation and chemotherapeutic agents in a cancer-specific manner. The lysosomotrophic property of CQ appears to be important for the increase in efficacy and specificity. Although more studies are needed, CQ may be one of the most effective and safe sensitizers for cancer therapies. Taken together, it appears that the efficacy of conventional cancer therapies can be dramatically enhanced if used in combination with CQ and its analogs.

Hybrid pharmacophore design and synthesis of isatin-benzothiazole analogs for their anti-breast cancer activity.

A hybrid pharmacophore approach was used to design and synthesize isatin-benzothiazole analogs to examine their anti-breast cancer activity. The cytotoxicity of these compounds were determined using three different human breast tumor cell lines, MDA-MB231, MDA-MB468, MCF7, and two non-cancer breast epithelial cell lines, 184B5 and MCF10A. Although all compounds examined were quite effective on all the cancer cell lines examined, the compounds 4-bromo-1-diethylaminomethyl-1H-indole-2,3-dione (2l) and 4-chloro-1-dimethylaminomethyl-3-(6-methyl-benzothiazol-2-ylimino)-1,3-dihydro-indol-2-one (5e) emerged as the most active compounds of this series. Importantly, the cytotoxic effect of 2l was 10-15-fold higher on cancer than non-cancer cells, suggesting that this compound can be very effective for the control of breast cancer with low side effects. Since 2l showed effective cytotoxicity on MCF7 cells and arrested the cells at G2/M at a similar concentration, these two phenomena may be closely correlated. We conclude that the isatin-linked benzothiazole analog can serve as a prototype molecule for further development of a new class of anti-breast cancer agents.

The efficacy and selectivity of tumor cell killing by Akt inhibitors are substantially increased by chloroquine.

This study was to evaluate the enhancement value of chloroquine (CQ) in cancer cell killing when used in combination with Akt inhibitors. The results showed that the combination of CQ and Akt inhibitors is much more effective than either one alone. Importantly, the CQ-mediated chemosensitization of cell killing effects by Akt inhibitors is cancer specific. In particular, when combined with 10 microM CQ, 1,3-dihydro-1-(1-((4-(6-phenyl-1H-imidazo[4,5-g]quinoxalin-7-yl)phenyl)methyl)-4-piperidinyl)-2H-benzimidazol-2-one (an Akt1 and 2 inhibitor; compound 8) killed cancer cells 10-120 times more effectively than normal cells. Thus, CQ is a very effective and cancer-specific chemosensitizer when used in combination with Akt inhibitors.

Synthesis and in vitro cytotoxicity evaluation of 4-aminoquinoline derivatives.

A series of 4-aminoquinoline derivatives were synthesized by the reaction of 4-chloro-7-substituted-quinolines with the corresponding mono/dialkyl amines. The structures of the synthesized compounds were confirmed by NMR and FAB-MS spectral and elemental analyses. Subsequently, the compounds were examined for their cytotoxic effects on two different human breast tumor cell lines: MCF7 and MDA-MB468. Although all compounds examined were quite effective on both cell lines, the compound N'-(7-chloro-quinolin-4-yl)-N,N-dimethyl-ethane-1,2-diamine emerged as the most active compound of the series. It was particularly potent against MDA-MB 468 cells when compared to chloroquine and amodiaquine. The compound butyl-(7-fluoro-quinolin-4-yl)-amine showed more potent effects on MCF-7 cells when compared to chloroquine. Therefore, 4-aminoquinoline can serve as the prototype molecule for further development of a new class of anticancer agents.

Design, synthesis and antimalarial activity of a new class of iron chelators.

Iron is crucial for many biochemical reactions involved in the growth and multiplication of the malaria parasite Plasmodium falciparum. There are many reports indicating that the iron chelators have antimalarial activity in vitro, in vivo and in human studies. However, these compounds suffer from a number of serious problems such as limited membrane permeability, short half-life and require long subcutaneous infusions. To circumvent these drawbacks we have designed a new class of iron chelators, wherein EDTA is tethered to 4-aminoquinoline. Here 4-aminoquinoline scaffold is used as a carrier to penetrate biological membrane and facilitate targetting the compounds to acidic food vacuole of the parasite. This study describes the synthesis of novel iron chelators and their in vitro antimalarial activity against P. falciparum strain of NF-54. The calculated LogP values of these compounds suggest the importance of lipophilicity for the antimalarial activity. The EDTA esters are more active than the corresponding acids. The biophysical studies suggest that these compounds may inhibit the parasite growth by iron chelation mechanism.

Insulin suppresses the increased activities of lysosomal cathepsins and ubiquitin conjugation system in burn-injured rats.

BACKGROUND: Burn injury results in increased rate of skeletal muscle protein degradation. In vitro studies on incubated muscles indicate that increased rate of protein degradation is due to activation of multiple proteolytic systems, but the supporting evidence is of an indirect nature. The present study was carried out to investigate the role of various lysosomal cathepsins, ubiquitin conjugation, and proteasome systems in accelerated proteolysis, and the effect of insulin in burn-induced muscle wasting syndrome. MATERIALS AND METHODS: Fifteen to twenty percent total body surface area scald burn injury was inflicted on the shaved dorsum of young growing rats. Insulin-treated rats received a daily single subcutaneous injection for 3 days (0.25-1.0 U/day). The rate of ubiquitin conjugation to endogenous proteins and exogenously added (125)I-lysozyme and the activities of various proteases were measured in muscle homogenates. RESULTS: Burn injury resulted in increased rate of ubiquitin conjugation to endogenous proteins and (125)I-lysozyme. Activities of cathepsins B, C, H, and L were also up-regulated following burn injury. When the burn-injured rats were treated with insulin, the increased rate of ubiquitin conjugation and cathepsin activities were suppressed to the control levels. CONCLUSIONS: The increased ubiquitin conjugation and lysosomal cathepsins contribute to accelerated protein degradation in burn-injured rats and insulin suppresses the muscle protein degradation at least in part by suppressing the activities of lysosomal cathepsins and of ubiquitin conjugation system.