Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 17, Issue 5, 2017

Cyclin-Dependent Kinases 4 (CDK4) belongs to a family of serine-threonine protein kinase and plays key regulatory role in G1-phase of cell cycle progression. Compelling evidences have shown that targeting CDK4 pathway is an attractive proposition for tumor therapy. Recent progresses of selective small molecule CDK4 inhibitors in cancer therapy have endorsed the field to be interested and attractive. In this review, we will discuss the recent developments of CDK4 inhibitors on several aspects such as the structure of CDK4, the working mechanism of CDK4 inhibitors, the structure activity relationships (SARs) of the selective CDK4 inhibitors and the latest developments of the selective CDK4 inhibitors in clinical trials.

Selenium (Se) is a ubiquitous, albeit not uniformly distributed metalloid present in earth crust. Consequently, its human intake with food products, particularly grains and vegetables, is also very uneven, and in certain cases can result in a severe Se deficiency. It was also documented that Se deficiency observed in some countries and/or geographic regions (e.g. Keshan region in China), is associated with an increased morbidity and mortality of neoplastic diseases. To correct this problem a number of organic and inorganic selenium compounds were developed and tested. However, it is now firmly established that only an inorganic sodium selenite with four-valent Se, and not that with six-valent (selenate) cation shows anticancer activity. This difference in their biological activities is due to their physicochemical properties. Thus selenite (Se+4) can undergo redox reaction, for example with protein’s sulfhydryl groups expressed on the surface of tumor cells. In this way selenite prevents non-enzymatic formation of parafibrin that coats tumors cells and hence presents them as ‘self’ to the innate cellular immune system. Consequently, macrophages of the lymphatic system do not recognize neoplastic cells as ‘foreign’ bodies and spare them from the immune destruction. This mechanism can explain the failure of various immunotherapies to completely eliminate tumors from human bodies. Another contributing factor to carcinogenesis is the excessive consumption of red meat containing redox-active iron (Fe+3) that initiates parafibrin formation from blood fibrinogen. In conclusion, sodium selenite is a readily available and inexpensive drug of choice in the cancer treatment and prevention.

Objective: The aim of this paper is to investigate the effect of dendrosomal curcumin (DNC) on the expression of p53 in both p53 mutant cell lines SKBR3/SW480 and p53 wild-type MCF7/HCT116 in both RNA and protein levels. Background: Curcumin, derived from Curcumin longa, is recently considered in cancer related researches for its cell growth inhibition properties. p53 is a common tumor-suppressor gene involved in cancers and its mutation not only inhibits tumor suppressor activity but also promotes oncogenic activity. Method: Here, p53 mutant/Wild-type cells were employed to study the toxicity of DNC using MTT assay, Flow cytometry and Annexin-V, Real-time PCR and Western blot were used to analyze p53, BAX, Bcl-2, p21 and Noxa changes after treatment. Results: During the time, DNC increased the SubG1 cells and decreased G1, S and G2/M cells, early apoptosis also indicated the inhibition of cell growth in early phase. Real-Time PCR assay showed an increased mRNA of BAX, Noxa and p21 during the time with decreased Bcl-2. The expression of p53 mutant decreased in SKBR3/SW480, and the expression of p53 wild-type increased in MCF7/HCT116. Conclusion: Consequently, p53 plays an important role in mediating the survival by DNC, which can prevent tumor cell growth by modulating the expression of genes involved in apoptosis and proliferation.

Background: In recent years, the relationship between overexpression of matrix metalloproteinases (MMPs) and tumor invasion/metastasis has prompted researchers to develop MMP inhibitors as anticancer drugs. Objective: The aim of this study was to design and synthesize new thiazole-based anticancer agents targeting MMPs. Method: New thiazole derivatives were synthesized and investigated for their cytotoxic effects on A549 human lung adenocarcinoma, MCF-7 human breast adenocarcinoma and NIH/3T3 mouse embryonic fibroblast cell lines using MTT assay. The potential inhibitory effects of the best candidates on gelatinases (MMP-2, MMP-9), and collagenases (MMP-1, MMP-8, MMP-13) were evaluated. Results: Ethyl 2-[2-((4-amino-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl)thio)acetamido]-4-methylthiazole-5-carboxylate (3) was found to be the most promising anticancer agent against MCF-7 cell line due to its selective inhibitory effect on MCF-7 cells with an IC50 value of 20.6±0.3 μg/mL when compared with cisplatin (IC50= 35.31±0.51 μg/mL). Compound 3 also showed multiple MMP (MMP-1, MMP-8 and MMP-9) inhibitory activity (10.56±1.70, 20 and 7.28±1.49%, respectively). Conclusion: The notable anticancer activity and selectivity of compound 3 on MCF-7 cell line can be attributed to multiple MMP inhibition potential.

Background: Quinoxalines have shown a wide variety of biological activities including as antitumor agents. The aims of this study were to evaluate the activity of quinoxaline 1,4-di-N-oxide derivatives on K562 cells, the establishment of the mechanism of induced cell death, and the construction of predictive QSAR models. Material and Methods: Sixteen esters of quinoxaline-7-carboxylate 1,4-di-N-oxide were evaluated for antitumor activity on K562 chronic myelogenous leukemia cells and their IC50 values were determined. The mechanism of induced cell death by the most active molecule was assessed by flow cytometry and an in silico study was conducted to optimize and calculate theoretical descriptors of all quinoxaline 1,4-di-N-oxide derivatives. QSAR and QPAR models were created using genetic algorithms. Results & Conclusions: Our results show that compounds C5, C7, C10, C12 and C15 had the lowest IC50 of the series. C15 was the most active compound (IC50= 3.02 μg/mL), inducing caspase-dependent apoptotic cell death via the intrinsic pathway. QSAR and QPAR studies are discussed.

Background: Hepatocellular carcinoma (HCC) is one of the leading cancers in the world, including Taiwan. The chemoresistance of advanced HCC frequently results in the poor prognosis of patients. Previous studies demonstrated the quinoline derivative, 9-bis[2-(pyrrolidin-1-yl)ethoxy]-6-{4-[2-(pyrrolidin-1-yl)ethoxy]phenyl}-11Hindeno[ 1,2-c]quinolin-11-one (BPIQ) exerts the inhibitory potential against several cancer cells, including liver cancer cells. Objective: We further investigated the anti-HCC effects of BPIQ, including apoptosis and the modulation of ER stress. Methods: Both trypan blue exclusion assay and colony formation assay were performed to examine whether BPIQ affects the growth of HCC cell lines Ha22T and Huh7. Flow cytometry-based assay was performed for determining the cell cycle distribution and apoptosis. Western blot assay was conducted for detecting the changes in apoptosis- and endoplasmic reticulum (ER) stress-associated proteins. Results: BPIQ inhibits cell growth and induces the apoptosis of both Ha22T and Huh7 cell lines significantly. The level of γH2AX, an endogenous DNA damage biomarker was dramatically increased suggesting the involvement of DNA damage pathway in BPIQ-induced apoptosis. Further, BPIQ down-regulates the pro-survival proteins, survivin, XIAP and cyclin D1. BPIQ also may regulate ER stress response through modulating the levels of ER stress-related proteins Glucose-regulated protein of 78 kD (GRP78), Inositol-requiring kinase-1α (IREα), C/EBP homologous protein (Chop) and calnexin. Conclusions: The anti-HCC effect of BPIQ may occur through down-regulating pro-survival proteins, and the modulation of ER stress may contribute to the BPIQ-induced apoptosis of HCC cells. The chemotherapeutic or chemopreventive applications of BPIQ for HCC treatment will be worthy of further investigation in future.

Background: Despite of significant progress achieved in the chemotherapy of cancer; it is still among the leading cause of morbidity and mortality worldwide. Objective: Taking cognizance of the extensive biological potential of reported thieno[2,3-d]pyrimidines and inspired by the clinically available anticancer agents dasatinib and gefitinib, 4-substituted thieno[2,3-d]pyrimidines have been synthesized. Methods: The compounds were synthesized via microwave-assisted methods and screened for their cytotoxic activity against liver HepG-2, lung NCI-H522, melanoma A-375, pancreatic MIA PaCa-2 and colon CaCo-2 human cancer cell lines using MTT assay. Results: The antiproliferative potential of most active compounds 20b and 20f (piperidino substituted); and 22d (hybrid analogue of Dasatinib) was further assessed and confirmed by calcein AM and colony formation assay, which revealed the higher potency of hybrid analogue 22d in comparison to piperidino substituted derivative 20f. Conclusion: Flow cytometer based cell cycle perturbation experiments revealed that antiproliferative effects of the most active compound 22d was associated with increased proportion of cells in the G2/M and subG0/G1 phases of the cell cycle. In silico ADME studies also confer the drug like characteristics of the potent compounds.

Background: Gemin D (GD) is an ellagitannin found in several plant species rich in phenolic compounds. Its many beneficial properties include antioxidant and antitumoral. Objective: The present study assessed the genotoxicity, cytotoxicity, antigenotoxicity, and anticytotoxicity of GD by in vitro and in vivo assays. Method: The Ames mutagenicity assay in Salmonella typhimurium, Micronucleus and Comet tests in mice were used to evaluate the biological activities mentioned above. To assess the GD’s protective effects against DNA damage induced by different mutagens we performed co-, pre- and/or post-treatment in these assays. Results: There was no genotoxic effect of GD via Ames and Micronucleus tests, but in the Comet assay the highest dose induced DNA damage. This same highest dose presented a significant cytotoxicity in mice. In the antigenotoxicity, GD protected DNA against the action of 4-nitroquinoline-1-oxide and sodium azide by Ames test, and also against the harmful action of cyclophosphamide in pre- and co-treatment by Micronucleus and Comet tests, but it did not protect DNA in post-treatment. Regarding to anticytotoxicity, GD provoked an anticytotoxic effect only during pre-treatment. Conclusion: Therefore, GD showed relevant antigenotoxic, anticytotoxic and cytotoxic effects, which indicate that it may be a probable candidate for chemoprevention or for the development of new cancer therapies.

Background: Pyrimidines have widespread activity and have shown potent antibacterial and anticancer activity. Objective: To synthesise a range of pyrimidine diones and test them for their antibacterial and anticancer activity. Method: The pyranopyrimidin-2,4-dione derivatives (1-7) were synthesized in a one-pot reaction by reacting malononitrile and barbituric acid with several aromatic aldehydes in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) in aqueous medium. The compounds were tested for their antibacterial activity using the broth microdilution method and for their cytotoxicity against three cell lines, HeLa (cervical cancer), Caco-2 (human colon adenocarcinoma) and HEK 293 (human embryonic kidney cells) using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) assay. Results: Compounds 1-7 were successfully synthesized in yields of >90%. The 3,4-dihydroxyaryl (3) and the 2,5- dimethoxyaryl (7) derivatives were novel. Compounds 3, 5 (4'-methoxy derivative) and 6 (2',3'-dimethoxy derivative) showed antibacterial activity comparable to or better than the standard ampicillin. All the test compounds 1-7 showed good anticancer activity. The IC50 values ranged from 3.46 to 37.13 μM (HeLa); 136.78 to 297.05 μM (Caco-2) and 137.84 to 333.81 μM (HEK293). The best activity was seen in the HeLa cell line when compared to the standard 5FU (5-Fluorouracil IC50 of 41.85 μM), with 1, 2, 5 and 7 having IC50 values of 10.64, 3.46, 4.36 and 4.44 μM respectively. Additionally, two representative compounds (1 and 7) found to be potent against the two cell lines (HeLa and HEK 293) were docked into the binding site of human kinesin Eg5 with the aim of predicting their binding propensities and to establish their mechanism of action. The Lipinski parameters of these compounds were also computed and analysed for their drug-likeness. Conclusion: Compound 6 is an excellent candidate for a broad spectrum antibiotic with MBCs of 45.6-365.2 μM, while both 3 and 6 have the potential to be developed into an antibiotic against MRSA, with MBCs of 183-199 μM. Since all synthesized compounds showed IC50 values of 10 μM or less especially against the HeLa cells, they can be considered good lead compounds for anticancer agents. Additionally, the docking simulations suggested a good binding affinity of the compounds with Eg5 and indicated their anti-cancer action, at least partially, through its inhibition. The predicted Lipinski descriptors also indicated the potential of these compounds as an orally active drug.

Background: Chemoprevention using natural agents has emerged as a new and promising strategy for reducing cancer burden. Sesamol, a water soluble lignin, is a potent antioxidant with potential anticancer activities. Its small size (molecular weight: 138.34g) coupled with easy permeability (log P: 1.29) results in its excessive systemic loss therefore, compromising local bioavailability. Furthermore, irritant nature of sesamol limits its application on skin per se. Objective: Present study aims to evaluate chemopreventive efficacy of free and encapsulated (SLNs) sesamol, at gross and molecular level, in DMBA induced skin cancer animal model. Methods: Evaluation is done in terms of tumor burden quantification, histological evaluation of skin, determination of oxidative stress, and quantification of apoptotic proteins, bcl-2 and bax, using both western blot analysis and immunofluorescence studies. Results: Sesamol administration (both in free and encapsulated form) significantly decreased the tumor burden and lipid peroxidation level and increased anti-oxidant levels, thereby hampering the development and promotion of skin tumors. Further, downregulation of bcl-2 and stimulation of bax protein expression on treatment with both free and encapsulated sesamol was responsible for the induction of apoptosis in tumor cells. Encapsulating sesamol into SLNs not only reduced its irritant nature which limits its direct topical application but also improved its local targeting to skin. Conclusion: Both free and encapsulated sesamol demonstrated the inhibition of tumor progression by inducing skin cell apoptosis via bcl-2/bax mediated pathway.

Objective: The aim of this study was to evaluate the 99mTc-HYNIC-D4 peptide as a new radiotracer for tumor targeting in non small cell lung tumor that overexpresses epidermal growth factor receptor (EGFR). Method: D4 small peptide (Leu-Ala-Arg-Leu-Leu-Thr) was selected as a candidate for specific targeting on EGFR. It was conjugated with HYNIC on N-terminus and labeled with 99mTc using tricine as a co-ligand. The cellular and animal studies were evaluated for specific binding of this labeled peptide. Result: Radiochemical purity was determined to be 98% by instant thin layer chromatography and reverse-phase high performance liquid chromatography. Stability of radiolabeled peptide was more than 90% up to 24 h incubation in solution at 37°C. Specific binding of the radiolabeled peptide to the EGFR showed dissociation constant of 181 ± 41 nM. Animal biodistribution in normal and A-549 xenografted nude mice showed rapid clearance from blood and other non target organs. Tumor uptake values as %ID/g (percentage of injection dose per gram of tissue) were 8.07% at 1 h and 3.82% at 4 h after injection that was blocked by presaturation of EGFR using an excess of cold peptide. Conclusion: This study showed that 99mTc-HYNIC-D4 is a promising tumor targeting radiotracer on the non small cell lung tumor.

Background: Thiosemicarbazone (TSC) is a Schiff base that has been receiving considerable attention owing to its promising biological implication and remarkable pharmacological properties. The most promising drug candidate of this class would be Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone) which has entered phase II clinical trials as a potent anti-cancer chemotherapeutic agent. Objective: The current research aimed to synthesize several Schiff base ligands from (3-formyl-4-hydroxyphenyl) methyltriphenylphosphonium (T). Additionally, the current research aimed to study the growth inhibitory effect of triphenylphosphonium containing thiosemicarbazone derivatives on PC-3 cells by deciphering the mechanisms involved in cell death. Method: The compounds were characterized by various spectroscopic methods (infrared spectra, 1H NMR, 13C NMR, HRESIMS and X-ray crystallography) and the results were in conformity with the structure of the targeted compounds. Growth inhibitory effect of the compounds were performed against six human cell lines. Results: DM(tsc)T displayed most potent activity against PC-3 cells with IC50 value of 2.64 ± 0.33 μM, surpassing that of the positive control cisplatin (5.47 ± 0.06 μM). There were marked morphological changes observed in DM(tsc)T treated cells stained with acridine orange and ethidium bromide which were indicative of cell apoptosis. Treatment with DM(tsc)T showed that the cell cycle is arrested in the G0/G1 phase after 72 hours. Mitochondrial membrane potential loss was observed in cells treated with DM(tsc)T, indicating the apoptosis could be due to mitochondria mediated pathway. Conclusion: This study indicates that DM(tsc)T would serve as a lead scaffold for rational anticancer agent development.

Background: Malignant melanoma is a fast growing form of skin cancer with increasing global incidence. Clinically, canine malignant melanoma and human melanoma share comparable treatment-resistances, metastatic phenotypes and site selectivity. Objective: Both interferon-β (IFN&β) and bortezomib (BTZ) display inhibitory activities on melanoma cells. Here, we evaluated the cytotoxic effects of the combination of BTZ and IFNβ gene lipofection on cultured melanoma cell lines. Method: Cell viability determined by the acid phosphatase method, cell migration mesasured by the wound healing assay, DNA fragmentation and cell cycle by flow cytometry after propidium iodide staining and reactive oxygen species (ROS) production by H2DCF-DA fluorescence. Results: Four canine mucosal (Ak, Br, Bk and Ol) and two human dermal (A375 and SB2) melanoma cell lines were assayed. BTZ sub-pharmacological concentrations (5 nM) enhanced the cytotoxic effects of IFNβ transgene expression on melanoma cells monolayers and spheroids. The combination was also more effective than the single treatments when assayed for clonogenic survival and cell migration. The combined treatment produced a significant raise of apoptosis evidenced by DNA fragmentation as compared to either BTZ or IFNβ gene lipofection single treatments. Furthermore, BTZ significantly increased the intracellular ROS generation induced by IFNβ gene transfer in melanoma cells, an effect that was reversed by the addition of the ROS inhibitor N-acetyl-L-cystein. Conclusion: The present work encourages further studies about the potential of the combination of interferon gene transfer with proteasome inhibitors as a new combined therapy for malignant melanoma, both in veterinary and/or human clinical settings.

Background: Matrix metalloproteinases are known as extracellular matrix degrading enzymes and have important role on tumor progression. Objective: This study reports the effects of 1,3,5-trisubstituted indole derivatives on cytotoxicity, apoptosis and MMP- 2/MMP-9 mRNA expression of MCF-7 human breast carcinoma cells. Method: The cytotoxic effects of the compounds on MCF-7 cells were performed by MTT test, and cell proliferation was determined via BrdU incorporation. The apoptotic effects were observed by cell death detection elisa. The effects of the compounds on MMP-2/-9 enzyme activity and mRNA expression were also performed. Results: The compounds inhibited the proliferation of MCF-7 breast carcinoma cells significantly in a dose dependent manner. All compounds were able to induce DNA fragmentation, especially compound 1. The IC50 values of compound 2 and 4 for MMP-2 were 0.42 μM and 1.88 μM, respectively. MMP-2 mRNA expression results were correlated with the inhibition of enzyme activity, such compound 4 inhibited MMP-2 mRNA expression at all treated concentrations. Docking simulation has also been performed to analyze the binding mode of compounds and the results showed that compound 2, the most active compound, formed a hydrogen bond with Glu202 for binding to the MMP-2 active site. In addition, the hydrophobic parts of compound 2 are in contact with nonpolar surface areas of MMP-2, such as His201, His211, Tyr223 and Tyr193. Conclusion: According to the molecular docking results along with the biological assay data, it is suggested that compound 2 might be used for further design and development of MMP-2 inhibitors.