Anti-Cancer Agents in Medicinal Chemistry (v.15, #7)

Meet Our Editorial Board Member: by Pawel Kafarski (805-805).

Is Notch Signaling a Specific Target in Hepatocellular Carcinoma? by Lichun Sun, Guangchun Sun, Yan Yu, David H. Coy (809-815).
Hepatocellular carcinoma (HCC) is one of the most malignant cancers, with the second highest cancer death rate world-wide, next to lung cancer. The signaling mechanisms in HCC are currently not clear. Notch signaling, which is highly conserved and plays a critical role in many cancers, was found to be aberrantly upregulated in HCC tissues compared to normal liver tissues. Accumulating evidence supports that Notch signaling plays a significantly important role in HCC carcinogenesis. This review discusses the functions of Notch signaling in HCC and its potential therapeutic applications against this cancer.

Recent Advance in Drug Development of Squamous Cell Carcinoma by Jun Lei, Bing Fu, Hang Yin, Guanxiu Tang, Shujuan Zhu, Chunli Yan, Quanyong He (816-827).
Squamous cell carcinoma (SCC) has a high worldwide incidence that is commonly seen as head and neck cancers, esophageal cancers, and non-small cell lung cancers. There is a poor prognosis for SCC due to potential recurrence and its metastatic tendency so the 5-year survival rate is very low. Target therapy is a novel and promising treatment strategy exhibiting great anti-tumor effects and survival benefits in SCC. This review summarizes current treatment strategies from clinical and experimental studies, including the agents targeting epidermal growth factor receptors, RNA polymerase, toll-like receptors, p38α MAPK, CXCR, and the related combination therapy regimens. However, there are still many challenges we have to face. It is a burning need to improve the development and availability of drug formulations.

Antibody-drug conjugates (ADCs) showed strong anticancer efficacy in the clinic. However, the current conventional technologies generate conjugates with undefined attachment sites and heterogeneous profiles containing different sub-populations, leading to potential off-target toxicity. In order to reduce the variability and heterogeneity associated with the ADCs generated using conventional technologies, several site-specific antibody-drug conjugation strategies were developed for the next generation of ADCs. These strategies include cysteine-targeted conjugation by engineering a free cysteine into the antibody or by placing a thiol bridge on cysteines in hinge disulfides. Glutamine-targeted conjugation was also demonstrated by coupling the drug-linker to glutamine residues through an engineered glutamine tag or a native glutamine, as well as an additionally introduced glutamine residue in aglycosylated antibody mutant using microbial transglutaminase. The site-specific conjugation of drug-linker to antibody carbohydrates was developed either through metabolic engineering or a chemo-enzymatic approach. Other amino acids, such as unnatural amino acids or amino acid derivatives introduced through protein engineering, have also been shown to be efficient targets for site-specific conjugation. The sitespecific ADCs with homogeneous profiles and well-defined conjugation sites were obtained using these second generation ADC methods and showed potent in vitro cytotoxicity and strong in vivo antitumor activity. These results suggest that newly developed site-specific conjugation technologies can potentially be applied in producing the next generation ADC for cancer treatment in the clinic with high therapeutic index.

A Role for the Inflammatory Mediators Cox-2 and Metalloproteinases in Cancer Stemness by G.K. Chimal-Ramírez, N.A. Espinoza-Sanchez, E.M. Fuentes-Panana (837-855).
In solid tumors, neoplastic cells are surrounded by a specific microenvironment that integrates the extracellular matrix, lymphatic and blood vessels, and mesenchymal and immune cells, which together are known as the tumor microenvironment (TME). The TME governs many of the aggressive features of tumors, such as local invasion and metastasis. Additionally, new evidence indicates that the TME can trigger stem cell-like programs in cancer cells, forming cancer stem cells (CSC). Experimental and clinical studies suggest that CSCs are resistant to current common cancer therapies and are responsible for tumor recurrence. In this review, we will describe the TME by focusing on how matrix metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2) induce stemness and sustain stem cell maintenance. This reprogramming toward a CSC phenotype may be critical in tumor cell responses to chemotherapy and relapse with more aggressive tumor clones. Therefore, therapeutic agents targeting MMPs and COX-2 in the tumor microenvironment may become important drugs to control the establishment of CSCs and in the overall prognosis of the disease.

Current Molecularly Targeting Therapies in NSCLC and Melanoma by Supriya Rajanna, Ichwaku Rastogi, Luke Wojdyla, Hiroko Furo, Agnes Kulesza, Leo Lin, Bonnie Sheu, Mark rakes, Marko Ivanovich, Neelu Puri (856-868).
Surgery, radiation therapy, and chemotherapy are the traditional options to control tumor progression. However, these strategies are fraught with harmful side effects and are ineffective in metastatic and advanced cancers. Biomarkers that are overexpressed in cancers and are involved in cell growth, proliferation, migration, and survival have recently become the focus of new molecular targeting therapies. Novel therapies targeting biomarkers have roles in tumorigenesis that are overexpressed in cancers may be more efficacious and less toxic in comparison to traditional therapies. These therapies include the use of tyrosine kinase inhibitors and monoclonal antibodies for the treatment of cancer. However, the efficacy of these therapies is limited due to the development of drug resistance after prolonged treatment. Current research is focused on understanding mechanisms of resistance to overcome the barriers limiting the use of these targeting therapies in the treatment of cancer. In this review, we will discuss the clinical status of tyrosine kinase inhibitors and monoclonal antibodies against several prevalent biomarkers that are candidates for therapy in non-small cell lung cancer (NSCLC) and melanoma.

The Applications of Targeting Anti-Cancer Agents in Cancer Therapeutics by Guang-Chun Sun, X u Yang, Yan Yu, Dai-Wei Zhao (869-880).
Anti-cancer targeting drugs appear to be a new and powerful "weapon" for cancer therapies. These targeting drugs are directed against specific molecules that are over-expressed or where certain unique factors are aberrantly expressed either in cancer cells or in diseased cell sites. Compared with traditional chemotherapeutic drugs, these targeting drugs have the advantages of high specificity, efficacy and less side effects. Target therapy is a breakthrough and revolutionary advance in the field of cancer therapy. Tumor angiogenesis plays a key role in tumor growth and metastasis and the mutation of tyrosine kinases is also strongly associated with cancer progression. Thus, in this review, we will discuss the advances in the development of targeting anti-cancer drugs by narrowing it down to small molecule tyrosine kinase inhibitors, monoclonal antibodies against epidermal growth factor receptors belonging to the ErbB family of receptor tyrosine kinases and angiogenic inhibitors. It will also address concerns for drug resistance and adverse events.

RUNX2 and Osteosarcoma by Na Li, Dongwei Luo, Xiaoxia Hu, Wei Luo, Guanghua Lei, Qian Wang, Ting Zhu, Junxia Gu, Yaojuan Lu, Qiping Zheng (881-887).
Osteosarcoma (OS) is the most common pediatric bone cancer in children and young adults. Previous studies have suggested the importance of osteoblast activity in OS tumorigenesis and metastasis, as OS is characterized by abnormal bone formation, while osteoblast is the predominant cell type both in OS and in metastatic tumor tissues. RUNX2 is a known essential transcription factor for osteoblast differentiation. RUNX2 has also been linked to many human cancers, including bone cancers and cancer metastasis in bone. However, the view of RUNX2 during OS tumorigenesis has not been unanimous. In this manuscript, we reviewed the osteoblastic origin in OS etiology. The oncogenic property of RUNX2 in human OS studies was briefly summarized. RUNX2 may be involved in OS pathogenesis by regulating cell cycle controlling of (pre)-osteoblasts, which subsequently convert to OS cells. The roles and mechanisms of RUNX2 during OS metastasis and bone metastasis in target cancers (herein prostate and breast cancers), were as described. The potential involvement of Runx2 in multiple mouse OS models that use human OS cell lines (Xenografts), tumor suppressor genes p53 and Rb1 were also discussed. Finally, we updated some microRNAs studies and their relation with RUNX2 in OS pathogenesis. This review provides a comprehensive understanding of RUNX2's function during OS pathogenesis and will help with the research designing and strategy in controlling OS.

Molecular Targets of Omega-3 Fatty Acids for Cancer Therapy by K. Pandima Devi, T. Rajavel, G. L. Russo, M. Daglia, S. F. Nabavi, S. M. Nabavi (888-895).
Nowadays, dietary guidelines acknowledge the therapeutic role of omega-3 polyunsaturated fatty acids, as the most important class of fatty acids, against different human diseases. During the last two decades, the average level of consumption of omega-3 polyunsaturated fatty acids has increased from 0.1 to 0.2 g per day. Omega-3 polyunsaturated fatty acids are a group of long-chain polyunsaturated fatty acids which are identified in different foods such as fatty fish, shellfish, and vegetable oils. A growing body of epidemiological and experimental evidence supports the anticancer effects of omega-3 polyunsaturated fatty acids, which led to the identification of their molecular targets in several cancer models. The present review focuses on the basic evidence supporting the potential applications of omega-3 polyunsaturated fatty acids in cancer therapy.

Inhibition of Testosterone Aromatization by the Indole-3-carbinol Derivative CTet in CYP19A1-overexpressing MCF-7 Breast Cancer Cells by Mauro De Santi, Elisa Carloni, Luca Galluzzi, Aurora Diotallevi, Simone Lucarini, Mauro Magnani, Giorgio Brandi (896-904).
Natural products such as aromatase inhibitors have been the object of growing attention in recent years because of their potential to inhibit aromatase with fewer side effects and the possible translation of their current use as chemotherapeutic agents to future clinical applications in breast cancer chemoprevention. We have previously investigated CTet, a novel anticancer agent obtained from the broccoli-derived compound indole-3- carbinol (I3C), that shows great anticancer potential in both in vitro and in vivo studies. Here we evaluated the potential of CTet as a chemopreventive agent in aromatase expressing MCF-7/AROM-1 breast cancer cells. The testosterone (TE) aromatization in estradiol (E2) was indirectly evaluated in terms of inhibition of TE-induced cell proliferation, ERα phosphorylation/activation and Bcl-2 and IGF-1R ERE-regulated protein accumulation. Our results showed that CTet inhibited TE-driven ERα phosphorylation of both cytosolic and nuclear ERα pools, suggesting an inhibitory effect of TE aromatization in E2. CTet did not inhibit E2-driven nuclear ERα phosphorylation, but partially inhibited E2-driven cytosolic ERα phosphorylation. Moreover, CTet inhibited Bcl-2 and IGF-1R accumulation induced by TE but not that which was induced by E2. A cell-free enzymatic assay showed that CTet did not inhibit aromatase activity directly; however, since CTet treatment induced endoplasmic reticulum stress, the TE aromatization could be affected because the aromatase enzyme is located within the endoplasmic reticulum. Finally, CTet and letrozole synergistically inhibited TE-induced cell proliferation. These results showed the potential of the I3C derivative CTet as a chemopreventive agent that interferes with aromatase activity.

In Vivo Anti-Tumor Effects of Flavokawain A in 4T1 Breast Cancer Cell-Challenged Mice by Nadiah Abu, Nurul Elyani Mohamed, Swee Keong Yeap, Kian Lam Lim, M Nadeem Akhtar, Aimi Jamil Zulfadli, Beh Boon Kee, Mohd Puad Abdullah, Abdul Rahman Omar, Noorjahan Banu Alitheen (905-915).
Flavokawain A is a chalcone that can be found in the kava-kava plant (Piper methsyticum) extract. The kava-kava plant has been reported to possess anti-cancer, anti-inflammatory and antinociceptive activities. The state of the immune system, and the inflammatory process play vital roles in the progression of cancer. The immunomodulatary effects and the anti-inflammatory effects of flavokawain A in a breast cancer murine model have not been studied yet. Thus, this study aimed to elucidate the basic mechanism as to how flavokawain A regulates and enhance the immune system as well as impeding the inflammatory process in breast cancer-challenged mice. Based on our study, it is interesting to note that flavokawain A increased the T cell population; both Th1 cells and CTLs, aside from the natural killer cells. The levels of IFN-γ and IL-2 were also elevated in the serum of flavokawain A-treated mice. Apart from that, flavokawain A also decreased the weight and volume of the tumor, and managed to induce apoptosis in them. In terms of inflammation, flavokawain A-treated mice had reduced level of major pro-inflammatory mediators; NO, iNOS, NF-KB, ICAM and COX-2. Overall, flavokawain A has the potential to not only enhance antitumor immunity, but also prevents the inflammatory process in a cancer-prone microenvironment.

Inhibition of the Hsp90 function is an essential therapeutic approach and several inhibitors were designed as anti-cancer agents. These inhibitors are ATPases and they aim to deregulate Hsp90 folding function. ATPase proteins are common in human metabolism but they form nonspecific targets. Hsp90 functions as dimer with coordinating chaperones. Heat Shock Organizing Protein (Hop) forms a bridge between Hsp90 and Hsp70-Hsp40 complex to form Hsp90-Hsp70 coordination. Perturbing conformational changes of these Hsp proteins, dimer formation, and protein-protein interactions inhibit Hsp90 substrate protein folding function. This approach does not target all ATPase proteins but targets Hsp90 function solely. For this purpose, we designed compounds to block Hsp90 function. Moreover, molecular docking studies as well as competition analysis of the compounds were performed with Hsp90. Novel thiazolyl coumarine compounds were determined as valuable C-terminal Hsp90 inhibitors and provide promising templates for the drug design. Anticancer activities of these novel compounds were tested by employing human colon (DLD-1) and liver cancer (HepG2) cell lines. Thiazolyl coumarine compounds are found to be significant and useful for the treatment of human colon and liver cancer as evidenced by in vitro and in silico results.