Anti-Cancer Agents in Medicinal Chemistry (v.16, #6)

Meet Our Editorial Board Member: by Roy M. Golsteyn (657-657).

CD47 is a widely expressed cell membrane receptor belonging to the immunoglobulin (Ig) superfamily. CD47 is involved in a number of cellular processes, including proliferation, apoptosis, adhesion and migration through interacting with integrin, thrombospondins and SIRP?. CD47 also plays an important role in the immune system and homeostasis. In recent few years, numerous studies have demonstrated that targeting CD47 exhibits noticeable effects on inhibition of tumor growth and prevention of metastasis in various types of cancers, while the mechanisms is complicated. In this review, we stated three possible mechanisms of targeting CD47 for cancer treatment. First, blockade of CD47 interrupts the CD47-SIRP? pathway which helps cancer cells escape from phagocytosis by macrophages. Second, ligation of CD47 induces cancer cells apoptosis. Third, targeting CD47 improves the tumor microenvironment. We also described several prospective strategies that have been used for targeting CD47 in cancer therapy, including antibodies, miRNA/siRNA and recombinant protein, etc. In conclusion, CD47 is a promising cancer biomarker, and targeting CD47 presents an effective and potential therapeutic strategy through synthesized mechanisms.

A Review of the Recent Developments in Synthetic Anti-Breast Cancer Agents by Parvesh Singh, Nomandla Ngcoya, Vipan Kumar (668-685).
The perceptible decrease in the incidence of breast cancer in recent years has not influenced its societal and economic impact and it remains as the most commonly diagnosed malignancies among females. Recent reports of clinical trials in preventive settings suggested chemoprevention as an appealing strategy zeroing heavily on endocrine intervention using selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs). Unfortunately, these drugs are only effective in prevention of endocrine responsive lesions with essentially no effect in reducing the risk of estrogen-negative breast cancer. Further, the existing drugs for breast cancer treatment are invariably associated with several drawbacks such as poor oral bioavailability, non-selectivity and poor pharmacodynamics properties, limiting their clinical utility. Thus, the identification of new molecular targets and the development of agents with better pharmacological profiles will streamline the development of rational, effective and safe anticancer drugs with minimal side-effects. Over the past few years, different research groups have been actively involved in the design and synthesis of novel anti-breast cancer agents. In this review article, the recent developments (2013 onwards) made in the direction of synthesis of new scaffolds with promising anti-breast cancer activity, are briefly described. Hopefully, the data compiled in this article will update scientific community with recent endeavors in this field, and will certainly be encouraging for further research in this direction.

Metal Containing Cytostatics and Their Interaction with Cellular Thiol Compounds Causing Chemoresistance by Jan Hrabeta, Vojtech Adam, Tomas Eckschlager, Eva Frei, Marie Stiborova, Rene Kizek (686-698).
The history of metal based cytostatics began in the 1970s by discovering the effects of cisplatin. Since then several generations of platinum based cytostatics have started to be the key weapon against tumor development and metastasis occurrence. Nevertheless, some attention has been also paid to non-platinum metals, such as ruthenium, titanium, gallium, iron, cobalt, gold, and palladium. Ruthenium, titanium, and gallium complexes have been also tested in clinical studies. This boom in metal based cytostatics can be explained by great effort paid to the elucidation of mechanisms of tumor resistance to these drugs. The known mechanisms of drug resistance are: (i) down regulation, over-expression, or modification of molecules of interest; (ii) increased drug efflux; (iii) induction of anti-apoptotic mechanisms or inactivation of pro-apoptotic mechanisms; (iv) changes in enzymes with an ability to activate or detoxify a drug; (v) low access of the drug to a tumor; and/or (vi) alteration in drug metabolism or excretion [1]. Often discussed but not largely reviewed and summarized is the intracellular inactivation of platinum drugs by coordination to thiol containing biomolecules glutathione (GSH) and metallothioneins (MTs). Overexpression of MT and/or GSH may cause resistance to anticancer drugs. Thus, greater attention should be paid to these interactions in case to overcome the resistance of tumor to cytostatics.

In recent years, there has been an expansion of the understanding of how epigenetic dysregulation plays a role in tumorigenesis, progression, metastasis and treatment resistance. Evidence has focused on two common and well-studied “epigenetic codes”, i.e., DNA methylation and histone posttranslational modification, which regulate the transcriptional status in various types of cancer and the corresponding target agents.
Aside from “writers” and “erasers”, which refer to enzymes that catalyze and remove posttranslational modifications, respectively, “readers” bind to target proteins and recruit “writers” and “erasers” for regulating gene expression. A number of selective and potent anticancer compounds have been reported, some of which are in preclinical or clinical trials that have shown promising results, primarily against malignant neoplasms such as hematologic malignancies, with the subsequent emerging development of both monotherapy and co-administration with traditional cytotoxic medicines against solid tumors. Second-generation epigenetic agents such as EZH2 and BET inhibitors have greatly progressed. Epigenetic dysregulation has also provided feasibility for the diagnosis and treatment of cancer. In this review, we summarize the progress in epigenetics and drug discovery for cancer and certain clinical trials that may provide a perspective for future development.

Synthesis of 9-O-3-(1-piperazinyl/morpholinyl/piperidinyl)pentyl-berberines as Potential Antioxidant and Cytotoxic Agents by Bhupendra M. Mistry, Rahul V. Patel, Young-Soo Keum, Doo Hwan Kim (713-721).
A new series of 9-O-3-(1-piperazinyl/morpholinyl/piperidinyl)pentyl-berberines has been efficiently formulated via coupling 1,5-dibromopentane with berberrubine which was obtained by treating berberine in a vacuum oven at optimum temperature and pressure. Nucleophilic substitution of a variety of substituted piperazines, morpholine, carbazole and piperidine furnished analogues 5a-i. Final compounds were evaluated for their in vitro antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6- sulphonic acid) (ABTS) bioassays. Also, cancer cell inhibitory potential of titled compounds was screened for cervical cancer, HeLa and CaSki employing SRB assay in terms of cytotoxicity. A minimum inhibitory concentration of 5a-i towards normal cells was studied using Madin-Darby canine kidney (MDCK) cell line. Final compounds with carbazole and 1-(naphthalen-2-yl)piperazine showed excellent free radical scavenging efficacies in DPPH and ABTS bioassays, respectively. The presence of naphthyl, benzhydryl, benzoyl, furoyl and heterocyclic rings on the piperazine system was essential to exert anticipated cytotoxic effects against cancer cell lines. The structure of the final compounds was adequately confirmed via spectroscopic techniques, elemental analysis analysis and characterization of physical properties.

Design and Synthesis of Novel Schiff Base-Benzothiazole Hybrids as Potential Epidermal Growth Factor Receptor (EGFR) Inhibitors by Meenakshi Singh, Sudhir Kumar Singh, Bhushan Thakur, Pritha Ray, Sushil K. Singh (722-739).
A series of novel Schiff bases -benzothiazole hybrids was designed, synthesized and evaluated for their anticancer activity by MTT assay and western blot method. Antiproliferative screening indicated that compound containing dihydroxy substituents had potent inhibitory activity with IC50 value 34µg/ml against SKOV3, A2780-S and A2780-CR cell lines. It showed more potent cytotoxicity in combination with cisplatin and paclitaxel than alone in the selected cell lines (SKOV3, A2780 and A2780-CR models). The in vitro cytotoxicity of the compounds on IOSE 364 cell line was evaluated to establish the selectivity. Molecular docking study exhibited good binding against epidermal growth factor receptor, which was further ascertained by immunoblot assay using specific antibody against phosphorylated EGFR, and thus unravelling the targeted anticancer mechanism.

A series of novel thiohydantoin derivatives were synthesized and evaluated for the abilities of inhibiting cell proliferation and prostate specific antigen (PSA) expression in prostate cancer cells. These derivatives selectively inhibited proliferation of AR positive LNCaP cells and PSA expression except compounds 5i and 5j. Compound 5t was approximately 15-fold more potent than MDV3100 to inhibit LNCaP cell proliferation. Compounds 5i and 5j inhibited cell growth of both AR positive LNCaP cells and AR negative PC-3 cells with potential to be developed as novel agents to treat antiandrogen resistant prostate cancer.

The combination of medicinal plant extracts with known chemotherapeutics offers significant potential for the development of novel therapies in cancer disease. Cucurbitacin B (CuB) is one of the most potent and widely used members of cucurbitacin family and it is known to have important effects on several diseases including cancer. To determine whether CuB can enhance chemosensitivity to imatinib mesylate (IM), in the present study, the combined effects of CuB with IM on MCF-7 and SW480 cells were investigated. The cells were treated with CuB alone or in combination with IM and the results showed that the combination treatment synergistically inhibited cell proliferation and induced apoptosis. Furthermore, the combined effect of CuB and IM on matrix metalloproteinase-2 (MMP-2) gene expression, a member of MMP family which is responsible for the degradation of extracellular matrix was also evaluated. CuB increased the inhibitory effect of IM on MMP-2 expression synergistically in a dose dependent manner. The results suggest that CuB in combination with IM may serve as a potentially useful therapeutic strategy for patients with breast and colorectal cancer.

Synthesis and Pharmacological Evaluation of Maleopimaric N-arylimides: Identification of Novel Proapoptotic Agents by Guiyang Yao, Manyi Ye, Yongtao Zhu, Zhixin Liao, Hengshan Wang (755-762).
Several N-aryl maleopimaric acid diimides (3a-3d, 4a-4g) were synthesized and evaluated their topoisomerase I inhibitory activities along with cytotoxicities against NCI, MGC-803, Bel-7404 and Hct-116 cell lines. The pharmacological dates revealed that most of structure analogs exhibited moderate to high levels of anticancer activities against the tested cancer cell lines. Compound 4g with phenylalanine substituent exhibited significant cytotoxicity against MGC-803 and Hct-116 cells (IC50 was 9.85±1.24 and 8.47±0.95 µM, respectively). All the synthesized compounds exhibited no cytotoxicity against HUVEC cells. In addition, maleopimaric diimides showed stronger cytotoxicity and topoisomerase I inhibitory activity compared to that of maleopimaric acid. Structure-activity relationship study showed that carboxyl and diimide moieties were important to display Topo I inhibitory activities. Further experiments proved that 4g could induce apoptosis of MGC-803 cells. In addition, the further mechanisms of compound 4g-induced apoptosis in MGC-803 cells demonstrated that compound 4g induced the activations of caspase-4, caspase-8 and caspase-3 for causing cell apoptosis, and altered antiand pro-apoptotic proteins. Moreover, cell cycle analysis indicated that the derivative 4g mainly arrested MGC-803 cells in S stage.

Photodynamic therapy (PDT) as a clinical cancer therapy, is a mild therapy, which involves application of photosensitizers (PSs) located in target cells and then irradiated by corresponding wavelength. The activation of PSs generates radical oxygen species (ROS) to exert a selective cytotoxic activity for the target cells. Aloe-emodin (AE) has been found to be an anti-tumor agent in many studies, and has also been demonstrated as a photosensitizer, in the recent years. In order to study the mechanisms of aloe-emodin as a photosensitizer, we investigated the mechanisms of photo-cytotoxicity induced by aloe-emodin in breast cancer MCF-7 cells in the present study. Analysis of cell proliferation evidenced that there was a drastic depression after photodynamic treatment with a series of aloe-emodin concentrations and light doses. We observed changes in apoptosis and demonstrated that the mechanisms of apoptosis were involved in mitochondrial and endoplasmic reticulum death pathways. The capacity of adhesion, migration and invasion of breast cells was measured using WST8 and transwell assay and demonstrated that AE-PDT significantly inhibited adhesion, migration and invasion of MCF-7cells. The expression of MMP2, MMP9, VEGF and Nrf2 demonstrated that the metastasis was related to oxidative stress. Analysis of changes in cytoskeleton components (F-actin) evidenced cytoskeleton disorganization after treatment with AE-PDT. Taken together, the present results indicated that PDT with aloe-emodin effectively suppressed cancer development in MCF-7cells, suggesting the potential of AE as a new photosensitizer in PDT which can provide a new modility for treating cancer.

Multiple Pharmacological Properties of a Novel Parthenin Analog P16 as Evident by its Cytostatic and Antiangiogenic Potential Against Pancreatic Adenocarcinoma PANC -1 Cells by Akshra Goswami, Bhahwal Ali Shah, Navneet Batra, Ajay Kumar, Santosh Kumar Guru, Shashi Bhushan, Fayaz Ahmad Malik, Amit Joshi, Jagtar Singh (771-780).
Pancreatic ductal adenocarcinoma (PDA) remains one of the deadliest types of cancers. Median survival rate is very poor with the currently available chemotherapeutical regimens. Therefore, discovery of new antineoplastic agents against PDA is one of the focused areas of contemporary research. The present study was undertaken to explore the antitumour activity of a potent parthenin analog P16. Among PANC-1, Mia PaCa-2 and AsPC-1 pancreatic cancer cells, PANC-1 showed highest sensitivity to P16 with an IC50 value of 3.4 ?M. Time dependent cell cycle studies revealed that P16 suppressed the growth of PANC-1 cells by arresting the progression through the cell cycle in G2/M phase via downregulation of cyclin B1 and cyclin A. However, P16 did not alter the expressions of CDK-1 and CDC25C in PANC-1 cells. The P16 induced cell cycle arrest, which consequently, led to induction of apoptosis, which was accompanied by activation of caspase-9 and -3. Interestingly, PANC-1 cells displayed increasing loss of mitochondrial potential, which seemed to be correlated to the activation of caspase-3. Additionally, P16 was also able to down-regulate the cell migration in PANC-1 cells. Furthermore, P16 treatment of hypoxic PANC-1 cells strongly suppressed the expression of proangiogenic factors VEGFR-2, HIF1? and HIF1β. Antiangiogenic ability of P16 was also reflected in the human umbilical vascular endothelial cells (HUVECs), where it effectively suppressed the migration and inhibited the formation of the tube in a matrigel based assay. Therefore, cytostatic and antiangiogenic properties of P16 against pancreatic adenocarcinoma cells make it a suitable candidate for further investigation.

The aim of this study was to investigate the effects of plant phenolic compound tannic acid (TA) on proliferative, metastatic, invasive properties of prostate cancer (PCa) cells; PC-3 and LNCaP, as well as drug metabolizing and antioxidant enzymes. Characterization of TA was done by using FT-IR and NMR. TA dose dependently inhibited the proliferation of PC-3 and LNCaP cells with IC50 values 35.3 ?M and 29.1 ?M, respectively. Wound healing assay showed that TA significantly inhibited (92.7%) migration of PCa cells (p<0.0001). In addition, TA was found to have anti-invasive potential on PC-3 cells and it inhibited (80.9%, p<0.0001) invasion of PC-3 cells into matrigel. Only 17.8% of PC-3 cells can form colony in the 0.7% agarose after treatment of cells with TA at the IC50 value concentration. Furthermore, flow cytometry analyses with Annexin V-APC and 7-AAD staining demonstrated that TA increases early apoptosis rate of PC-3 cells by 25.8% and LNCaP cells by 20.9%. Besides, Western blot and qRT-PCR analyses also demonstrated that TA regulates protein and mRNA expressions of CYP17A1, CYP3A4, CYP2B6, NQO1, GSTM1 and GSTP1 enzymes. The results obtained from this study show that TA might be a good candidate for combinational therapy and highly effective strategic molecule for reducing the occurrence of PCa.