Anti-Cancer Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Anti-Cancer Agents) - Volume 16, Issue 2, 2016

Acetogenins (ACG) are naturally occurring compounds that are chemically one of the least investigated families. In the review, we have provided a comprehensive listing of 133 of these compounds for which anti-tumor activity has been documented within the literature. We have compiled and studied their chemical structure, in-vitro as well as in-vivo anticancer biological activity. We observed that the relative potency of acetogenins can be categorized as adjacent bis-THF ACGs > nonadjacent bis-THF ACGs > mono-THF ACGs > linear-THF ACGs. Among adjacent bis-THF ACGs, asiminocin (A100), asiminecin (A101), asiminacin (A102) and asimin (A103) are the most active compounds with in-vitro activity (ED50) in the range of 10-9 to 10-12 μg/mL. For the nonadjacent bis-THF ACGs, gigantecin (A53) exhibited better cytotoxicity as compared to others in the series with an ED50 in the range of 10-6 to 10-8 μg/mL. Similarly, muricatetrocin-C (A36), a mono-THF and coriadienin (A116) a linear ACG has been reported to show promising cytotoxicity with an ED50 of 10-5 μg/mL. Moreover, in-vivo studies indicate that compounds like bullatacin (A83), desacetyluvaricin (A76), bullatalicin (A58) and annonacin (A8) have demonstrated significant activity in mouse models and thereby exhibiting potential for lead development as a potential anticancer agent/drug. Also, globally oncologists are looking towards compounds from natural origin that inhibits the growth of resistant tumor cells. We find that several acetogenins like bullatacin (A83), motrilin (A95), asimicin (A77), trilobacin (A96), annonacin (A8), gigantetronenin (A108) and squamocin (A73) are efficacious in suppressing the proliferation of the MDR MCF-7/Adr cells. The present analysis suggests that acetogenins can act as yet another important source for obtaining promising lead compounds in order to contribute to cancer prevention, however, in future extensive in-vivo studies in animal models will be needed to provide insight for lead development.

Breast cancer (BC) is the second most common cause of cancer-related deaths in women throughout the world. Multiple drugs have been approved by US-FDA for breast related malignancies. Frequent emergence of resistances creates the severe need of newer moieties that are free from such problems. Drugs targeting breast cancer have been observed to be based on the multiple mechanisms of action, and various indole based anticancer agents have also been explored. Moreover, indoles have promising anti-cancer potential; there has been the emphasis on the synthesis of indole derivatives to overcome problems faced by existing therapeutic agents. Taking into consideration the above-mentioned facts we have analyzed in detail the possible role of indole based anticancer agents typically for breast related malignancies. This is the first exhaustive review that jointly covers various synthetic anticancer indole derivatives and related signaling pathways by which these derivatives have shown promising anti-breast cancer potential.

p53 protein is a prominent tumor suppressor to induce cell cycle arrest, apoptosis and senescence, which attracts significant interest to cancer treatment. Therefore, it would be particularly important to restore the wild–type p53 that retains latent functions in the approximately 50% of tumors. MDM2 (murine double minute 2), the principal cellular antagonist of p53, has long been believed to suppress p53 activity through two main mechanisms: promoting degradation via its E3 ligase activity and masking p53 transcriptional activation by direct binding. Targeting MDM2 E3 ligase activity is becoming a potential antitumor strategy resulting from MDM2’s decisive role in controlling the fate of p53: p53 is going to degradation when entrapped into MDM2-mediated ubiquitination, where p53 can escape by abrogating MDM2 E3 ligase activity using regulators. The intensive focus on regulating MDM2 ubiquitin E3 ligase activity has led to the rapid progress of its inhibitors, which may be possible to help p53 escape from degradation and restore its function to control tumor growth. This review summarizes the current inhibitors of MDM2 E3 ligase in cancer therapy based on the understanding the regulation of MDM2 E3 ubiquitin ligase activity, including post-translational modification, interactions between MDM2 and its cofactors, and regulation of MDM2 stability.

ROS have vital roles in cellular signaling and homeostasis. At low concentration, ROS promotes cancer cell survival by the activation of growth factors and MAP-kinases (MAPKs) that further activates cell cycle progression. At high concentration, ROS produces oxidative stress that activates programmed cell death or apoptosis. However, this fine distinction of ROS action either as a growth promoter or pro-apoptotic agent depends not only on dosage (concentration) but also on the duration, type, and site of ROS generation. The female steroid estrogens and their various metabolites generate ROS in the breast cancer cells. Slow, sustained and moderate level of ROS generated by estrogens and their metabolites cause initiation and progression of breast cancer. ROS generated by estrogens affect pro-proliferative (e.g. cyclin D1, Cdc2), prosurvival (e.g. AKT), antiapoptotic (e.g. BCl2) and pro-inflammatory (e.g. NF-ΚB) molecules. These multipronged actions of ROS lead to the activation of several signaling pathways involved in the breast cancer cell survival and proliferation, resulting in the progression of breast cancer. Present review article provides insights into the role of estrogen generated ROS and its associated signaling pathways in the initiation and progression of breast cancer. The importance of ROS as breast cancer drug target has also been discussed.

Chalcones comprise a characteristic framework of 1, 3-diaryl-2-propen-1-one. They have been heralded as promising anti cancer drugs and have received much attention in the field of cancer research and drug development. The cytotoxicity of these potent pharmacophores is attributable to a wide spectrum of biological activities like anti inflammatory, anti proliferative, anti fungal, etc. These anti tumor activities are effectuated through apoptosis, cell cycle arrest, anti tubulin and so forth. This review summarizes the recent developments on anti tumor activity of synthetic and natural chalcones and their detailed underlying mechanisms as reported in the past.

Treatment of brain tumour is a major challenge. This is mainly because of the limited bioavailability of chemotherapeutics in the brain. The major hurdle for brain availability of anticancer agents is the blood brain barrier (BBB). BBB is supposed to protect the brain and maintain homeostasis. It allows vital nutrient for normal brain function and effluxes out foreign toxic substance. Advance in knowledge of bidirectional movement across BBB has allowed development of strategies to enhance brain availability of chemotherapeutics for management of brain tumour. In this review we have focussed on various approaches adopted for enhancing delivery of anticancer agents. We have given a critical analysis of the approaches for further research

DNA interstrand crosslinks (ICLs) can be induced by numerous endogenous and exogenous chemical agents with the capacity of covalently binding to two base sites in the two strands of the DNA duplex. A series of normal DNA metabolism processes are affected by ICLs. For example, DNA replication and transcription are interfered during cell division, which is fatal to cell survival. In cancer cells, the induction of ICLs is a significant target for cancer chemotherapies. However, the formation of ICLs in cancer cells can be weakened by the repair mechanisms of DNA damage, which results in resistance to chemotherapies. Therefore, it is necessary to develop highly effective ICL agents for the purpose of achieving good chemotherapeutic effects. Furthermore, the combination of ICL agents with inhibitors of ICL repair is a promising strategy for the clinical treatment of cancer. This review summarizes the development of several types of ICL agents as chemotherapies over the past decades and the mechanisms underlying the repair of DNA ICLs. The potential of ICL repair inhibitors for combination therapy with ICL agents in cancer treatment is also discussed.

MicroRNAs (miRNAs) have a major role in cancer pathogenesis, cells growth and apoptosis. We studied the dysregulation of miRNAs after the induction of apoptosis by 4 μM dose of ATO in glioblastoma cell line, U87. The anticancer effect of ATO was verified using MTT, BrdU cell proliferation assay and flow cytometric analysis. Differential expressions of 88 cancer-related miRNAs were analyzed by real-time reverse transcription PCR using miRNA PCR cancer-array system. The fold changes of miRNAs were calculated by comparing the results of treated to untreated control. Among the 88 cancer-related miRNAs, 2-fold upregulation was detected in 26 miRNAs and downregulation in 10 miRNAs compared to the control. The role of some of the miRNAs with significant changes was investigated by searching the literature and studying their roles in apoptosis, cell cycle and in various cellular signalling pathways. Our results showed that ATO modified the expression of a significant number of cancer-related miRNAs in glioblastoma cell line; most of these especially the upregulated miRNAs, were known as tumor suppressors with extensive roles in cancer associated processes and pathways. This study supports the mediatory role of miRNAs in anticancer effect of ATO.

Treatment of non melanoma skin cancer and its precancerous skin lesions is associated with severe topical and systemic toxicity. So, it has become necessary to develop an efficient novel delivery system with less side effects and better patient compliance. Topical w/o microemulsion of 5-FU were prepared using sorbitan monooleate (Span 80), sorbitan trioleate (Span 85), polysorbate 80 (Tween 80), isopropyl alcohol (IPA) with different oils such as oleic acid, triacetin and isopropyl myristate (IPM). Evaluation tests of microemulsions like determination of thermodynamic stability, droplet size, viscosity, pH, conductivity and ex vivo release studies were performed. Spherical shape and Droplet size of microemulsion, which was around 100nm, was supported by Transmission electron microscopy. The lesser flux across skin for all microemulsion batches and higher skin retention of 5-FU loaded in microemulsion in comparison to topical 5-FU marketed cream resulted in better control over the drug release. Skin irritation studies on rats were performed to evaluate chronic toxicity of optimized microemulsion formulation on skin for 21 days and were compared with control group. Formalin (0.8%) was taken as standard irritant. Rat skin was observed for erythema and edema and the formulation was found safe for chronic use (p#131;0.01). Histopathology studies showed the epidermal and dermal layers to be normal, showing the 5-FU microemulsion formulation to be safe for topical use. Better control of the drug release through skin can curtail topical and systemic toxicity which is supported by the skin irritation and histopathology studies.

A series of novel 5-(substituted phenyl)-3-[(substituted phenylamino)methyl]-3H-[1,3,4]oxadiazole-2- thione derivatives were prepared and their in vitro cytotoxicity was evaluated against a panel of three cancer cell lines, namely, hepatocarcinoma HepG2, breast adenocarcinoma MCF-7, and leukemia HL-60 cells, using the widely accepted MTT assay. In general, the synthesized compounds displayed weak to moderate cytotoxic activity against the three tested cell lines. Compound 5a, which has trimethoxy substituents on both phenyl rings, exhibited the highest cytotoxic effect against all cell lines tested with IC50 values of 12.01, 7.52 and 9.7 μM against HepG2, MCF-7 and HL-60 cells, respectively. Mechanistic studies revealed that the test compounds showed a good inhibitory effect on cellular tubulin of hepatocellular carcinoma. Compound 5h was the most potent tubulin inhibitor in HepG2 cells, with 81.1 % inhibition of the original control tubulin. Moreover, the mechanism of tubulin polymerization inhibition was confirmed by immunofluorescence assay, flow cytometry, and docking study.