In vitro and in vivo anticancer activity of novel synthetic makaluvamine analogues

MDM2 Inhibitors for Cancer Therapy: The Past, Present, and Future

Since its discovery over 35 years ago, MDM2 has emerged as an attractive target for the development of cancer therapy. MDM2's activities extend from carcinogenesis to immunity to the response to various cancer therapies. Since the report of the first MDM2 inhibitor more than 30 years ago, various approaches to inhibit MDM2 have been attempted, with hundreds of small-molecule inhibitors evaluated in preclinical studies and numerous molecules tested in clinical trials. Although many MDM2 inhibitors and degraders have been evaluated in clinical trials, there is currently no Food and Drug Administration (FDA)-approved MDM2 inhibitor on the market. Nevertheless, there are several current clinical trials of promising agents that may overcome the past failures, including agents granted FDA orphan drug or fast-track status. We herein summarize the research efforts to discover and develop MDM2 inhibitors, focusing on those that induce MDM2 degradation and exert anticancer activity, regardless of the p53 status of the cancer. We also describe how preclinical and clinical investigations have moved toward combining MDM2 inhibitors with other agents, including immune checkpoint inhibitors. Finally, we discuss the current challenges and future directions to accelerate the clinical application of MDM2 inhibitors. In conclusion, targeting MDM2 remains a promising treatment approach, and targeting MDM2 for protein degradation represents a novel strategy to downregulate MDM2 without the side effects of the existing agents blocking p53-MDM2 binding. Additional preclinical and clinical investigations are needed to finally realize the full potential of MDM2 inhibition in treating cancer and other chronic diseases where MDM2 has been implicated. SIGNIFICANCE STATEMENT: Overexpression/amplification of the MDM2 oncogene has been detected in various human cancers and is associated with disease progression, treatment resistance, and poor patient outcomes. This article reviews the previous, current, and emerging MDM2-targeted therapies and summarizes the preclinical and clinical studies combining MDM2 inhibitors with chemotherapy and immunotherapy regimens. The findings of these contemporary studies may lead to safer and more effective treatments for patients with cancers overexpressing MDM2.

Anticancer Drug Discovery Based on Natural Products: From Computational Approaches to Clinical Studies

Globally, malignancies cause one out of six mortalities, which is a serious health problem. Cancer therapy has always been challenging, apart from major advances in immunotherapies, stem cell transplantation, targeted therapies, hormonal therapies, precision medicine, and palliative care, and traditional therapies such as surgery, radiation therapy, and chemotherapy. Natural products are integral to the development of innovative anticancer drugs in cancer research, offering the scientific community the possibility of exploring novel natural compounds against cancers. The role of natural products like Vincristine and Vinblastine has been thoroughly implicated in the management of leukemia and Hodgkin's disease. The computational method is the initial key approach in drug discovery, among various approaches. This review investigates the synergy between natural products and computational techniques, and highlights their significance in the drug discovery process. The transition from computational to experimental validation has been highlighted through in vitro and in vivo studies, with examples such as betulinic acid and withaferin A. The path toward therapeutic applications have been demonstrated through clinical studies of compounds such as silvestrol and artemisinin, from preclinical investigations to clinical trials. This article also addresses the challenges and limitations in the development of natural products as potential anti-cancer drugs. Moreover, the integration of deep learning and artificial intelligence with traditional computational drug discovery methods may be useful for enhancing the anticancer potential of natural products.

Role of p53 in breast cancer progression: An insight into p53 targeted therapy

The transcription factor p53 is an important regulator of a multitude of cellular processes. In the presence of genotoxic stress, p53 is activated to facilitate DNA repair, cell cycle arrest, and apoptosis. In breast cancer, the tumor suppressive activities of p53 are frequently inactivated by either the overexpression of its negative regulator MDM2, or mutation which is present in 30-35% of all breast cancer cases. Notably, the frequency of p53 mutation is highly subtype dependent in breast cancers, with majority of hormone receptor-positive or luminal subtypes retaining the wild-type p53 status while hormone receptor-negative patients predominantly carry p53 mutations with gain-of-function oncogenic activities that contribute to poorer prognosis. Thus, a two-pronged strategy of targeting wild-type and mutant p53 in different subtypes of breast cancer can have clinical relevance. The development of p53-based therapies has rapidly progressed in recent years, and include unique small molecule chemical inhibitors, stapled peptides, PROTACs, as well as several genetic-based approaches using vectors and engineered antibodies. In this review, we highlight the therapeutic strategies that are in pre-clinical and clinical development to overcome p53 inactivation in both wild-type and mutant p53-bearing breast tumors, and discuss their efficacies and limitations in pre-clinical and clinical settings.

Current Perspectives on Pyrroloiminoquinones: Distribution, Biosynthesis and Drug Discovery Potential

Pyrroloiminoquinones are a group of cytotoxic alkaloids most commonly isolated from marine sponges. Structurally, they are based on a tricyclic pyrrolo[4,3,2-de]quinoline core and encompass marine natural products such as makaluvamines, tsitsikammamines and discorhabdins. These diverse compounds are known to exhibit a broad spectrum of biological activities including anticancer, antiplasmodial, antimicrobial, antifungal and antiviral activities as well as the inhibition of several key cellular enzymes. The resurgence of interest in pyrroloiminoquinones and the convoluted understanding regarding their biological activities have prompted this review. Herein, we provided a concise summary of key findings and recent developments pertaining to their structural diversity, distribution, biogenesis, and their potential as chemical probes for drug development, including a discussion of promising synthetic analogs.

Anticancer potential of indole derivatives: an update

The heterocyclic indole is one of the most prevalent pharmacophores in nature. It has been a highly privileged scaffold for designing targeted and anticancer therapeutics. Countless fused heterocyclic templates have been developed with diverse physicochemical and biological properties. Due to their versatile ethanobotanical and pharmacological values, indole and its derivatives seek high demand in the chemical and healthcare sectors. Extensive anticancer research has been conducted in this decade to evaluate their efficacy for diverse malignancies. The chapter explores the anticancer activity of natural and synthetic indole derivatives expressed through targeting different biological receptors and enzymes.

Marine Alkaloids: Compounds with In Vivo Activity and Chemical Synthesis

Marine alkaloids comprise a class of compounds with several nitrogenated structures that can be explored as potential natural bioactive compounds. The scientific interest in these compounds has been increasing in the last decades, and many studies have been published elucidating their chemical structure and biological effects in vitro. Following this trend, the number of in vivo studies reporting the health-related properties of marine alkaloids has been increasing and providing more information about the effects in complex organisms. Experiments with animals, especially mice and zebrafish, are revealing the potential health benefits against cancer development, cardiovascular diseases, seizures, Alzheimer's disease, mental health disorders, inflammatory diseases, osteoporosis, cystic fibrosis, oxidative stress, human parasites, and microbial infections in vivo. Although major efforts are still necessary to increase the knowledge, especially about the translation value of the information obtained from in vivo experiments to clinical trials, marine alkaloids are promising candidates for further experiments in drug development.

Caspase-3: A primary target for natural and synthetic compounds for cancer therapy

Caspases, a group of protease enzymes (cysteine proteases), exist as inactive zymogens in the cells and execute apoptosis (programmed cell death). Caspase-3, an executioner caspase, plays an imperative role in apoptosis and becomes a primary target for cancer treatment. A number of analogues of quinazoline, quinazolinone, indoloquinazolines, quinone, naphthoquinones, pyrroloiminoquinones, styrylquinolines, tetheredtetrahydroquinoline, fluoroquinolone, thiosemicarbazones, benzotriazole, pyrimidines, chalcone, and carbazoles have been reported till date, representing caspase-3 mediated apoptosis for cancer therapy. Simultaneously, plant isolates, including lysicamine, podophyllotoxin, and majoranolide, have also been claimed for caspase-3-mediated apoptosis-induced cytotoxicity. Procaspase-activating compound-1 (PAC-1) is the first FDA approved orphan drug, and its synthetic derivative WF-208 also showed fascinating caspase-3 mediated anticancer activity. Till date, a large number of compounds have been reported and patented for their caspase-3-mediated cytotoxicity and now scientist is also focusing to introduce new compounds in market to encompass anticancer activity.

Targeting MDM2 for Neuroblastoma Therapy: In Vitro and In Vivo Anticancer Activity and Mechanism of Action

Simple Summary

Neuroblastoma is a malignant tumor of the sympathetic nervous system that causes aggressive disease in children. The overall survival rate of high-risk patients is very low, therefore developing effective and safe therapies for neuroblastoma is an urgent unmet medical need. The mouse double minute 2 (MDM2) homolog gene is amplified and overexpressed in neuroblastoma and contributes to the poor response to treatment and poor prognosis in patients with high-risk neuroblastoma. Therefore, targeting MDM2 provides a promising approach to neuroblastoma therapy, especially for advanced disease. In the present study, we tested a unique MDM2 inhibitor, SP141, for its therapeutic efficacy and safety in neuroblastoma tumor models. We found that SP141 has significant anti- neuroblastoma activity in cell culture and inhibits tumor growth in animal models of human neuroblastoma, without any noticeable host toxicity. These results provide the basis for targeting MDM2 to treat high-risk neuroblastoma.

Abstract

Background: Neuroblastoma is an aggressive pediatric solid tumor with an overall survival rate of <50% for patients with high-risk disease. The majority (>98%) of pathologically-diagnosed neuroblastomas have wild-type p53 with intact functional activity. However, the mouse double minute 2 (MDM2) homolog, an E3 ubiquitin ligase, is overexpressed in neuroblastoma and leads to inhibition of p53. MDM2 also exerts p53-independent oncogenic functions. Thus, MDM2 seems to be an attractive target for the reactivation of p53 and attenuation of oncogenic activity in neuroblastoma. Methods: In this study, we evaluated the anticancer activities and underlying mechanisms of action of SP141, a first-in-class MDM2 inhibitor, in neuroblastoma cell lines with different p53 backgrounds. The findings were confirmed in mouse xenograft models of neuroblastoma. Results: We demonstrate that SP141 reduces neuroblastoma cell viability, induces apoptosis, arrests cells at the G2/M phase, and prevents cell migration, independent of p53. In addition, in neuroblastoma xenograft models, SP141 inhibited MDM2 expression and suppressed tumor growth without any host toxicity at the effective dose. Conclusions: MDM2 inhibition by SP141 results in the inhibition of neuroblastoma growth and metastasis, regardless of the p53 status of the cells and tumors. These findings provide proof-of-concept that SP141 represents a novel treatment option for both p53 wild-type and p53 null neuroblastoma.

Synthetic Makaluvamine Analogs Decrease c-Kit Expression and Are Cytotoxic to Neuroendocrine Tumor Cells

In an effort to discover viable systemic chemotherapeutic agents for neuroendocrine tumors (NETs), we screened a small library of 18 drug-like compounds obtained from the Velu lab against pulmonary (H727) and thyroid (MZ-CRC-1 and TT) neuroendocrine tumor-derived cell lines. Two potent lead compounds (DHN-II-84 and DHN-III-14) identified from this screening were found to be analogs of the natural product makaluvamine. We further characterized the antitumor activities of these two compounds using pulmonary (H727), thyroid (MZ-CRC-1) and pancreatic (BON) neuroendocrine tumor cell lines. Flow cytometry showed a dose-dependent increase in apoptosis in all cell lines. Induction of apoptosis with these compounds was also supported by the decrease in myeloid cell leukemia-1 (MCL-1) and X-chromosome linked inhibitor of apoptosis (XIAP) detected by Western blot. Compound treatment decreased NET markers chromogranin A (CgA) and achaete-scute homolog 1 (ASCL1) in a dose-dependent manner. Moreover, the gene expression analysis showed that the compound treatment reduced c-Kit proto-oncogene expression in the NET cell lines. Induction of apoptosis could also have been caused by the inhibition of c-Kit expression, in addition to the known mechanisms such as damage of DNA by topoisomerase II inhibition for this class of compounds. In summary, makaluvamine analogs DHN-II-84 and DHN-III-14 induced apoptosis, decreased neuroendocrine tumor markers, and showed promising antitumor activity in pulmonary, thyroid, and pancreatic NET cell lines, and hold potential to be developed as an effective treatment to combat neuroendocrine tumors.

Targeting the p53-MDM2 pathway for neuroblastoma therapy: Rays of hope

Despite being the subject of extensive research and clinical trials, neuroblastoma remains a major therapeutic challenge in pediatric oncology. The p53 protein is a central safeguard that protects cells against genome instability and malignant transformation. Mutated TP53 (the gene encoding p53) is implicated in many human cancers, but the majority of neuroblastomas have wild type p53 with intact transcriptional function. In fact, the TP53 mutation rate does not exceed 1-2% in neuroblastomas. However, overexpression of the murine double minute 2 (MDM2) gene in neuroblastoma is relatively common, and leads to inhibition of p53. It is also associated with other non-canonical p53-independent functions, including drug resistance and increased translation of MYCN and VEGF mRNA. The p53-MDM2 pathway in neuroblastoma is also modulated at several different molecular levels, including via interactions with other proteins (MYCN, p14^ARF). In addition, the overexpression of MDM2 in tumors is linked to a poorer prognosis for cancer patients. Thus, restoring p53 function by inhibiting its interaction with MDM2 is a potential therapeutic strategy for neuroblastoma. A number of p53-MDM2 antagonists have been designed and studied for this purpose. This review summarizes the current understanding of p53 biology and the p53-dependent and -independent oncogenic functions of MDM2 in neuroblastoma, and also the regulation of the p53-MDM2 axis in neuroblastoma. This review also highlights the use of MDM2 as a molecular target for the disease, and describes the MDM2 inhibitors currently being investigated in preclinical and clinical studies. We also briefly explain the various strategies that have been used and future directions to take in the development of effective MDM2 inhibitors for neuroblastoma.

Marine compounds targeting the PI3K/Akt signaling pathway in cancer therapy

Cancer is a disease characterized by overproliferation, including that due to transformation, apoptosis disorders, proliferation, invasion, angiogenesis and metastasis, and is one of the deadliest diseases. Currently, conservative chemotherapy is used for cancer treatment due to a lack of effective drugs. The PI3K/Akt signaling pathway plays a very essential role in the pathogenesis of many cancers, and abnormal activation of this pathway leads to abnormal expression of a series of downstream proteins, which ultimately results in the excessive proliferation of cancer cells. Therefore, the PI3K/Akt signaling pathway is a critical target in cancer treatment. Marine drugs have attracted much attention in recent years, and studies have found that many extracts from oceanic animals, plants and microorganisms or their metabolites exert antitumor effects, including antiproliferative effects or the induction of cell cycle arrest, apoptosis or autophagy. However, most anticancer targets and the mechanisms of marine compounds remain unclear. The great potential of the development of marine drugs provides a new direction for cancer treatment. This review focuses on marine compounds that target the PI3K/Akt signaling pathway for the prevention and treatment of cancer and provides comprehensive information for those interested in research on marine drugs.

Two Birds with One Stone: NFAT1-MDM2 Dual Inhibitors for Cancer Therapy

The tumor suppressor p53 is believed to be the mostly studied molecule in modern biomedical research. Although p53 interacts with hundreds of molecules to exert its biological functions, there are only a few modulators regulating its expression and function, with murine double minute 2 (MDM2) playing a key role in this regard. MDM2 also contributes to malignant transformation and cancer development through p53-dependent and -independent mechanisms. There is an increasing interest in developing MDM2 inhibitors for cancer prevention and therapy. We recently demonstrated that the nuclear factor of activated T cells 1 (NFAT1) activates MDM2 expression. NFAT1 regulates several cellular functions in cancer cells, such as cell proliferation, migration, invasion, angiogenesis, and drug resistance. Both NFAT isoforms and MDM2 are activated and overexpressed in several cancer subtypes. In addition, a positive correlation exists between NFAT1 and MDM2 in tumor tissues. Our recent clinical study has demonstrated that high expression levels of NFAT1 and MDM2 are independent predictors of a poor prognosis in patients with hepatocellular carcinoma. Thus, inhibition of the NFAT1-MDM2 pathway appears to be a novel potential therapeutic strategy for cancer. In this review, we summarize the potential oncogenic roles of MDM2 and NFAT1 in cancer cells and discuss the efforts of discovery and the development of several newly identified MDM2 and NFAT1 inhibitors, focusing on their potent in vitro and in vivo anticancer activities. This review also highlights strategies and future directions, including the need to focus on the development of more specific and effective NFAT1-MDM2 dual inhibitors for cancer therapy.

Fastidious Anatomization of Biota Procured Compounds on Cancer Drug Discovery

BACKGROUND

Natural products are the rootstock for identifying new drugs since ancient times. In comparison with synthetic drugs, they have abounding beneficial effects in bestowing protection against many diseases, including cancer. Cancer has been observed as a major threat in recent decades, and its prevalence is expected to increase over the next decades. Also, current treatment methods in cancer therapy such as radiation therapy and chemotherapy cause severe adverse side effects among the cancer population. Therefore, it is exigent to find a remedy without any side effects.

METHODS

In recent years, research has focused on obtaining naturally derived products to encounter this complication. The current pace of investigations, such as gene identification and advancement in combinatorial chemistry, leads to the aberrant access to a wide range of new synthetic drugs. In fact, natural products act as templates in structure predictions and synthesis of new compounds with enhanced biological activities.

RESULTS

Recent developments in genomics have established the importance of polymorphism, which implies that patients require different drugs for their treatment. This demands the discovery of a large number of drugs, but limited sources restrict the pharmaceutical industry to overcome these major obstacles. The use of natural products and their semisynthetic and synthetic analogues could alleviate these problems. However, the lack of standardization in terms of developing methods for evaluating the chemical composition, efficacy, isolation and international approval is still a major limitation in this field. In the past few years, several drug-approval authorities, including the FDA and WHO have allowed using these naturally derived compounds in humans.

CONCLUSION

In this review, we described the use of some natural products from plant and marine sources in cancer treatment and shed some light on semi-synthetic and synthetic compounds derived from natural sources used in cancer therapy.

Study of molecular interactions by hydrogen bond of charged forms of makaluvamines and complex stability with H2O and glutamic acid (Glu Ac) by the theory of the functional of density (B3LYP)

This work was undertaken to understand the mode of interaction of makaluvamines, a class of marine pyrroloiminoquinone alkaloids isolated from sponges of the genus Zyzzya, used in the treatment of several human cancer cell lines. This analysis was done by the quantum chemistry method. First, we used electrostatic potential (ESP) to reveal the different sites that accept and donate hydrogen bonds (HB) of charged forms (protonated and methylated) of makaluvamines (at level B3LYP/6-311++G(d,p)). In a second step, we studied the interactions by hydrogen bond between these molecules and water molecule on the one hand (at level B3LYP/6-311++G(d,p)) and on the other hand glutamic acid a protein residue of topoisomerase II (at level B3LYP/6-31+G(d,p)). Finally, we calculated the corrected BSSE interaction energies and estimated the relative stability of the formed complexes.

A Novel Marine Natural Product Derived Pyrroloiminoquinone with Potent Activity against Skin Cancer Cells

Non-melanoma skin cancer is one of the major ailments in the United States. Effective drugs that can cure skin cancers are limited. Moreover, the available drugs have toxic side effects. Therefore, skin cancer drugs with less toxic side effects are urgently needed. To achieve this goal, we focused our work on identifying potent lead compounds from marine natural products. Five lead compounds identified from a class of pyrroloiminoquinone natural products were evaluated for their ability to selectively kill squamous cell carcinoma (SCC13) skin cancer cells using an MTT assay. The toxicity of these compounds was also evaluated against the normal human keratinocyte HaCaT cell line. The most potent compound identified from these studies, C278 was further evaluated for its ability to inhibit cancer cell migration and invasion using a wound-healing assay and a trans-well migration assay, respectively. To investigate the molecular mechanism of cell death, the expression of apoptotic and autophagy proteins was studied in C278 treated cells compared to untreated cells using western blot. Our results showed that all five compounds effectively killed the SCC13 cells, with compound C278 being the most effective. Compound C278 was more effective in killing the SCC13 cells compared to HaCaT cells with a two-fold selectivity. The migration and the invasion of the SCC13 cells were also inhibited upon treatment with compound C278. The expression of pro-apoptotic and autophagy proteins with concomitant downregulation in the expression of survival proteins were observed in C278 treated cells. In summary, the marine natural product analog compound C278 showed promising anticancer activity against human skin cancer cells and holds potential to be developed as an effective anticancer agent to combat skin cancer.

New Drugs from the Sea: Pro-Apoptotic Activity of Sponges and Algae Derived Compounds

Natural compounds derived from marine organisms exhibit a wide variety of biological activities. Over the last decades, a great interest has been focused on the anti-tumour role of sponges and algae that constitute the major source of these bioactive metabolites. A substantial number of chemically different structures from different species have demonstrated inhibition of tumour growth and progression by inducing apoptosis in several types of human cancer. The molecular mechanisms by which marine natural products activate apoptosis mainly include (1) a dysregulation of the mitochondrial pathway; (2) the activation of caspases; and/or (3) increase of death signals through transmembrane death receptors. This great variety of mechanisms of action may help to overcome the multitude of resistances exhibited by different tumour specimens. Therefore, products from marine organisms and their synthetic derivates might represent promising sources for new anticancer drugs, both as single agents or as co-adjuvants with other chemotherapeutics. This review will focus on some selected bioactive molecules from sponges and algae with pro-apoptotic potential in tumour cells.

Natural products targeting the p53-MDM2 pathway and mutant p53: Recent advances and implications in cancer medicine

The p53 tumor suppressor plays a major role in controlling the initiation and development of cancer by regulating cell cycle arrest, apoptosis, senescence, and DNA repair. The MDM2 oncogene is a major negative regulator of p53 that inhibits the activity of p53 and reduces its protein stability. MDM2, p53, and the p53-MDM2 pathway represent well-documented targets for preventing and/or treating cancer. Natural products, especially those from medicinal and food plants, are a rich source for the discovery and development of novel therapeutic and preventive agents against human cancers. Many natural product-derived MDM2 inhibitors have shown potent efficacy against various human cancers. In contrast to synthetic small-molecule MDM2 inhibitors, the majority of which have been designed to inhibit MDM2-p53 binding and activate p53, many natural product inhibitors directly decrease MDM2 expression and/or MDM2 stability, exerting their anticancer activity in both p53-dependent and p53-independent manners. More recently, several natural products have been reported to target mutant p53 in cancer. Therefore, identification of natural products targeting MDM2, mutant p53, and the p53-MDM2 pathway can provide a promising strategy for the development of novel cancer chemopreventive and chemotherapeutic agents. In this review, we focus our discussion on the recent advances in the discovery and development of anticancer natural products that target the p53-MDM2 pathway, emphasizing several emerging issues, such as the efficacy, mechanism of action, and specificity of these natural products.

Experimental Therapy of Advanced Breast Cancer: Targeting NFAT1-MDM2-p53 Pathway

Advanced breast cancer, especially advanced triple-negative breast cancer, is typically more aggressive and more difficult to treat than other breast cancer phenotypes. There is currently no curable option for breast cancer patients with advanced diseases, highlighting the urgent need for novel treatment strategies. We have recently discovered that the nuclear factor of activated T cells 1 (NFAT1) activates the murine double minute 2 (MDM2) oncogene. Both MDM2 and NFAT1 are overexpressed and constitutively activated in breast cancer, particularly in advanced breast cancer, and contribute to its initiation, progression, and metastasis. MDM2 regulates cancer cell proliferation, cell cycle progression, apoptosis, migration, and invasion through both p53-dependent and -independent mechanisms. We have proposed to target the NFAT1-MDM2-p53 pathway for the treatment of human cancers, especially breast cancer. We have recently identified NFAT1 and MDM2 dual inhibitors that have shown excellent in vitro and in vivo activities against breast cancer, including triple-negative breast cancer. Herein, we summarize recent advances made in the understanding of the oncogenic functions of MDM2 and NFAT1 in breast cancer, as well as current targeting strategies and representative inhibitors. We also propose several strategies for inhibiting the NFAT1-MDM2-p53 pathway, which could be useful for developing more specific and effective inhibitors for breast cancer therapy.

Highly efficient delivery of potent anticancer iminoquinone derivative by multilayer hydrogel cubes

We report a novel delivery platform for a highly potent anticancer drug, 7-(benzylamino)-3,4-dihydro-pyrrolo[4,3,2-de]quinolin-8(1H)-one (BA-TPQ), using pH- and redox-sensitive poly(methacrylic acid) (PMAA) hydrogel cubes of micrometer size as the encapsulating matrix. The hydrogels are obtained upon cross-linking PMAA with cystamine in PMAA/poly(N-vinylpyrrolidone) multilayers assembled within mesoporous sacrificial templates. The BA-TPQ-loaded hydrogels maintain their cubical shape and pH-sensitivity after lyophilization, which is advantageous for long-term storage. Conversely, the particles degrade in vitro in the presence of glutathione (5mM) providing 80% drug release within 24h. Encapsulating BA-TPQ into hydrogels significantly increases its transport via Caco-2 cell monolayers used as a model for oral delivery where the apparent permeability of BA-TPQ-hydrogel cubes was∼2-fold higher than that of BA-TPQ. BA-TPQ-hydrogel cubes exhibit better anticancer activity against HepG2 (IC50=0.52µg/mL) and Huh7 (IC50=0.29µg/mL) hepatoma cells with a 40% decrease in the IC50 compared to the non-encapsulated drug. Remarkably, non-malignant liver cells have a lower sensitivity to BA-TPQ-hydrogel cubes with 2-fold increased IC50 values compared to those of cancer cells. In addition, encapsulating BA-TPQ in the hydrogels amplifies the potency of the drug via down-regulation of MDM2 oncogenic protein and upregulation of p53 (a tumor suppressor) and p21 (cell proliferation suppressor) expression in HepG2 liver cancer cells. Moreover, enhanced inhibition of MDM2 protein expression by BA-TPQ-hydrogel cubes is independent of p53 status in Huh7 cells. This drug delivery platform of non-spherical shape provides a facile method for encapsulation of hydrophobic drugs and can facilitate the enhanced efficacy of BA-TPQ for liver cancer therapy.

STATEMENT OF SIGNIFICANCE

Many potent anticancer drugs are hydrophobic and lack tumor selectivity, which limits their application in cancer therapy. Although cubical hydrogels of poly(methacrylic acid) exhibit excellent biocompatibility and versatility, they have not been investigated for hydrophobic drug delivery due to poor mechanical stability and incompatibility between hydrophobic drugs and a hydrophilic hydrogel network. In this study, we provide a facile method to prepare a multilayer hydrogel-based platform with controlled nanostructure, cubical shape and redox-responsiveness for delivery of highly potent anticancer therapeutics, hydrophobic BA-TPQ. The BA-TPQ-hydrogel cubes have exceptional structural stability upon lyophilization which is advantageous for a long-term storage. The greatly enhanced trans-epithelial permeability and amplified anti-tumor activity of BA-TPQ are achieved by encapsulation in these hydrogel cubes. Furthermore, the anticancer BA-TPQ-hydrogel platform retains the selective activity of BA-TPQ to hepatocellular carcinoma cells. Overall, the produced BA-TPQ-hydrogel cubes demonstrate a high potential for clinical liver cancer therapy.

Another Look at Pyrroloiminoquinone Alkaloids-Perspectives on Their Therapeutic Potential from Known Structures and Semisynthetic Analogues

This study began with the goal of identifying constituents from Zyzzya fuliginosa extracts that showed selectivity in our primary cytotoxicity screen against the PANC-1 tumor cell line. During the course of this project, which focused on six Z. fuliginosa samples collected from various regions of the Indo-Pacific, known compounds were obtained consisting of nine makaluvamine and three damirone analogues. Four new acetylated derivatives were also prepared. High-accuracy electrospray ionization mass spectrometry (HAESI-MS) m/z ions produced through MS² runs were obtained and interpreted to provide a rapid way for dereplicating isomers containing a pyrrolo[4,3,2-de]quinoline core. In vitro human pancreas/duct epithelioid carcinoma (PANC-1) cell line IC₅₀ data was obtained for 16 compounds and two therapeutic standards. These results along with data gleaned from the literature provided useful structure activity relationship conclusions. Three structural motifs proved to be important in maximizing potency against PANC-1: (i) conjugation within the core of the ABC-ring; (ii) the presence of a positive charge in the C-ring; and (iii) inclusion of a 4-ethyl phenol or 4-ethyl phenol acetate substituent off the B-ring. Two compounds, makaluvamine J (9) and 15-O-acetyl makaluvamine J (15), contained all three of these frameworks and exhibited the best potency with IC₅₀ values of 54 nM and 81 nM, respectively. These two most potent analogs were then tested against the OVCAR-5 cell line and the presence of the acetyl group increased the potency 14-fold from that of 9 whose IC₅₀ = 120 nM vs. that of 15 having IC₅₀ = 8.6 nM.

Pharmacokinetics and Pharmacodynamics in Breast Cancer Animal Models

The study of pharmacokinetics (PK) and pharmacodynamics (PD) in cancer drug discovery and development is often paired and described in reciprocal terms, where PK is the analysis of the change in drug concentration with time and PD is the analysis of the biological effects of the drug at various concentrations over different time courses. While PK is defined by how a compound is absorbed, distributed, metabolized, and eliminated, PD refers to the measure of a compound's ability to interact with its intended target, leading to a biologic effect. Recent advances in anti-breast cancer drug discovery have resulted in several new drugs, but there is still a high attrition rate during clinical development. One reason for this failure is attributed to inappropriate correlation between the PK and PD parameters and subsequent extrapolation to human subjects. In this chapter, we describe the protocols of PK and PD studies in breast cancer models to assess the efficacy of an anti-breast cancer compound, noting the types and endpoints employed, and explain why it is important to link PK and PD in order to establish and evaluate dose/concentration-response relationships and subsequently describe and predict the effect-time courses for a given drug dose.

Inhibiting NFAT1 for breast cancer therapy: New insights into the mechanism of action of MDM2 inhibitor JapA

Transcription factor NFAT1 has been recently identified as a new regulator of the MDM2 oncogene. Targeting the NFAT1-MDM2 pathway represents a novel approach to cancer therapy. We have recently identified a natural product MDM2 inhibitor, termed JapA. As a specific and potent MDM2 inhibitor, JapA inhibits MDM2 at transcriptional and post-translational levels. However, the molecular mechanism remains to be fully elucidated for its inhibitory effects on MDM2 transcription. Herein, we reported that JapA inhibited NFAT1 and NFAT1-mediated MDM2 transcription, which contributed to the anticancer activity of JapA. Its effects on the expression and activity of NFAT1 were examined in various breast cancer cell lines in vitro and in MCF-7 and MDA-MB-231 xenograft tumors in vivo. The specificity of JapA in targeting NFAT1 and NFAT1-MDM2 pathway and the importance of NFAT1 inhibition in JapA's anticancer activity were demonstrated using NFAT1 overexpression and knockdown cell lines and the pharmacological activators and inhibitors of NFAT1 signaling. Our results indicated that JapA inhibited NFAT1 signaling in breast cancer cells in vitro and in vivo, which plays a pivotal role in its anticancer activity. JapA inhibited the nuclear localization of NFAT1, disrupted the NFAT1-MDM2 P2 promoter complex, and induced NFAT1 proteasomal degradation, resulting in the repression of MDM2 transcription. In conclusion, JapA is a novel NFAT1 inhibitor and the NFAT1 inhibition is responsible for the JapA-induced repression of MDM2 transcription, contributing to its anticancer activity. The results may pave an avenue for validating the NFAT1-MDM2 pathway as a novel molecular target for cancer therapy.

Identification of lineariifolianoid A as a novel dual NFAT1 and MDM2 inhibitor for human cancer therapy

There is an increasing interest in development of novel anticancer agents that target oncogenes. We have recently discovered that nuclear factor of activated T cells 1 (NFAT1) is a novel regulator of the Mouse Double Minute 2 (MDM2) oncogene and the NFAT1-MDM2 pathway has been implicated in human cancer development and progression, justifying that targeting the NFAT1-MDM2 pathway could be a novel strategy for discovery and development of novel cancer therapeutics. The present study was designed to examine the anticancer activity and underlying mechanisms of action of lineariifolianoid A (LinA), a novel natural product inhibitor of the NFAT1-MDM2 pathway. The cytotoxicity of LinA was first tested in various human cancer cell lines in comparison with normal cell lines. The results showed that the breast cancer cells were highly sensitive to LinA treatment. We next demonstrated the effects of LinA on cell proliferation, colony formation, cell cycle progression, and apoptosis in breast cancer MCF7 and MDA-MB-231 cells, in dose-dependent and p53-independent manners. LinA also inhibited the migration and invasion of these cancer cells. Our mechanistic studies further indicated that its anticancer activities were attributed to its inhibitory effects on the NFAT1-MDM2 pathway and modulatory effects on the expression of key proteins involved in cell cycle progression, apoptosis, and DNA damage. In summary, LinA is a novel NFAT1-MDM2 inhibitor and may be developed as a preventive and therapeutic agent against human cancer.

Antitumor Effect of the Mannich Base(1,3-bis-((3-Hydroxynaphthalen-2-yl)phenylmethyl)urea) on Hepatocellular Carcinoma

The present study was designed to evaluate the antitumor effects of the synthetic Mannich base 1,3-bis-((3-hydroxynaphthalen-2-yl)phenylmethyl)urea (1,3-BPMU) against HEP-G2 hepatoma cells and diethylnitrosamine (DEN)-induced hepatocarcinoma (HCC) in albino rats. In vitro analysis results revealed that 1,3-BPMU showed significant cytotoxicity and cell growth inhibition in HEP-G2 hepatoma cells in a concentration-dependent manner. Furthermore, flow cytometry results indicated that 1,3-BPMU enhanced early and late apoptosis. The maximum apoptosis was exhibited at a concentration of 100 μg/mL of 1,3-BPMU. In in vivo analysis, DEN treatment increased the content of nucleic acids, LPO and the activities of AST, ALT, ALP, LDH, γGT and 5'NT with decreased antioxidant activity as compared to control rats. However, 1,3-BPMU treatment to DEN-induced rats decreased the content of nucleic acids, LPO and the activities of AST, ALT, ALP, LDH, γGT and 5'NT and increased the activities of SOD, CAT, GPx, GST and GR (p < 0.05). Furthermore, 1,3-BPMU enhanced the apoptosis via upregulation of caspase-3 and caspase-9 and the downregulation of Bcl-2 and Bcl-XL mRNA expression as compared to DEN-induced rats. Histological and ultrastructural investigation showed that 1,3-BPMU treatment renovated the internal architecture of the liver in DEN-induced rats. In this study, the molecular and pre-clinical results obtained by treatment of DEN-induced rats with 1,3-BPMU suggested that 1,3-BPMU might be considered as an antitumor compound in the future.

Identification of a new class of natural product MDM2 inhibitor: In vitro and in vivo anti-breast cancer activities and target validation

The MDM2 oncogene has been suggested as a molecular target for treating human cancers, including breast cancer. Most MDM2 inhibitors under development are targeting the MDM2-p53 binding, and have little or no effects on cancers without functional p53, such as advanced breast cancer. The present study was designed to develop a new class of MDM2 inhibitors that exhibit anticancer activity in MDM2-dependent and p53-independent manners. The selective MDM2 inhibitors were discovered by a computational structure-based screening, yielding a lead compound, termed JapA. We further found that JapA inhibited cell growth, decreased cell proliferation, and induced G2/M phase arrest and apoptosis in breast cancer cells through an MDM2-dependent mechanism, regardless of p53 status. It also inhibited the tumor growth and lung metastasis in breast cancer xenograft models without causing any host toxicity. Furthermore, JapA directly bound to MDM2 protein and reduced MDM2 levels in cancer cells in vitro and in vivo by promoting MDM2 protein degradation and inhibiting MDM2 transcription, which is distinct from the existing MDM2 inhibitors. In conclusion, JapA represents a new class of MDM2 inhibitor that exerts its anticancer activity through directly down-regulating MDM2, and might be developed as a novel cancer therapeutic agent.

RYBP expression is associated with better survival of patients with hepatocellular carcinoma (HCC) and responsiveness to chemotherapy of HCC cells in vitro and in vivo

RYBP is a member of the polycomb group (PcG) proteins that typically act as transcriptional repressors via epigenetic modification of chromatin. The present study was designed to investigate the role of RYBP in HCC progression, chemosensitivity, and patient survival, and to explore the underlying molecular mechanism(s). In this study we investigated the expression of RYBP in 400 pairs of human HCC tissues and matched noncancerous samples. The effects of RYBP on HCC tumor growth and metastasis and chemosensitivity were determined both in vitro and in vivo. We herein demonstrate that the RYBP expression in HCC tissue samples was significantly lower than that in matched noncancerous liver tissues. Clinically, the low expression of RYBP was an independent predictor of a poor prognosis in patients with HCC. In in vitro HCC models, enforced RYBP expression inhibited cell growth and invasion, induced apoptosis, and increased the chemosensitivity of the cells, while RYBP knockdown led to the opposite effects. Furthermore, RYBP expression was induced by cisplatin, and adenovirus-mediated RYBP expression inhibited HCC tumor growth and sensitized HCC to conventional chemotherapy in vivo. Our results demonstrate that reactivating RYBP in cancer cells may provide an effective and safe therapeutic approach to HCC therapy.

RYBP predicts survival of patients with non-small cell lung cancer and regulates tumor cell growth and the response to chemotherapy

Ring1 and YY1 binding protein (RYBP) is a member of the Polycomb group (PcG) proteins and regulates cell growth through both PcG-dependent and -independent mechanisms. Our initial study indicated that RYBP is down-regulated in human non-small cell lung cancer (NSCLC) tissues. The present study determined the molecular role of RYBP in the development of NSCLC. We systemically investigated the association between the RYBP expression and the survival of patients with NSCLC. We also carried out in vitro and in vivo studies to explore the molecular basis for the tumor suppressor role of RYBP in NSCLC. Our clinical results demonstrated that the RYBP mRNA and protein expressions were significantly down-regulated in NSCLC and significantly linked to the poor prognosis in NSCLC patients. The enforced expression of RYBP inhibited cell survival, induced apoptosis, and increased chemosensitivity in NSCLC cells; knockdown of RYBP showed the opposite effects. Moreover, adenoviral delivery of RYBP sensitized the NSCLC cells to chemotherapy in vivo. In addition, RYBP expression was induced by paclitaxel, the first-line chemotherapeutic agent for NSCLC. Our results reveal that RYBP inhibits the aggressiveness of NSCLC cells and downregulation of RYBP is associated with poor prognosis, suggesting that RYBP could be developed as a biomarker and a novel target for therapy in patients with lung cancer.

Development and validation of an HPLC-MS/MS analytical method for quantitative analysis of TCBA-TPQ, a novel anticancer makaluvamine analog, and application in a pharmacokinetic study in rats

We have recently designed and synthesized several novel iminoquinone anticancer agents that have entered preclinical development for the treatment of human cancers. Herein we developed and validated a quantitative HPLC-MS/MS analytical method for one of the lead novel anticancer makaluvamine analog, TCBA-TPQ, and conducted a pharmacokinetic study in laboratory rats. Our results indicated that the HPLC-MS/MS method was precise, accurate, and specific. Using this method, we carried out in vitro and in vivo evaluations of the pharmacological properties of TCBA-TPQ and plasma pharmacokinetics in rats. Our results provide a basis for future preclinical and clinical development of this promising anticancer marine analog.

Anticancer properties of lamellarins

In 1985 the first lamellarins were isolated from a small oceanic sea snail. Today, more than 50 lamellarins have been inventoried and numerous derivatives synthesized and tested as antiviral or anticancer agents. The lead compound in the family is lamellarin D, characterized as a potent inhibitor of both nuclear and mitochondrial topoisomerase I but also capable of directly interfering with mitochondria to trigger cancer cell death. The pharmacology and chemistry of lamellarins are discussed here and the mechanistic portrait of lamellarin D is detailed. Lamellarins frequently serve as a starting point in the design of anticancer compounds. Extensive efforts have been devoted to create novel structures as well as to improve synthetic methods, leading to lamellarins and related pyrrole-derived marine alkaloids.

Eight pairs of epimeric triterpenoids involving a characteristic spiro-E/F ring from Abies faxoniana

Five pairs of new epimeric lanostane-type triterpenoids, abiespirones A-D (1-4) and G (7), two pairs of new epimeric cycloartane-type triterpenoids, abiespirones E and F (5, 6), and a pair of new epimeric 7(8→9)abeo-spirolanostane abiespirones H (8) with spiro-B/C and -E/F ring systems were isolated from Abies faxoniana as inseparable mixtures of C-23 epimers in a specific proportion. The HPLC plots showed that each purified isomer rapidly equilibrated with the C-23 epimer in solution. The structures of compounds 1-8 were elucidated by analysis of the NMR spectra and single-crystal X-ray diffraction. Compound 6 showed cytotoxicity against three hepatoma cell lines, namely, HepG2, Huh7, and SMMC7721, with IC50 values of 9.8, 7.5, and 10.7 μM, respectively, but exerted low cytotoxicity on normal QSG7701 hepatic cells, indicating its selective cytotoxicity for hepatoma cells. Compound 6 arrests the cell cycle at G2/M and induces cell apoptosis in Huh7 cells. In addition, the generation of reactive oxygen species (ROS) was detected in Huh7 cells when treated with compound 6, and a ROS scavenger partly blocked the effects of compound 6-induced Huh7 cell death, suggesting that compound 6-induced apoptosis is associated with elevated levels of ROS in Huh7 cells.

Development and validation of a rapid HPLC method for quantitation of SP-141, a novel pyrido[b]indole anticancer agent, and an initial pharmacokinetic study in mice

There is an increasing interest in targeting the MDM2 oncogene for cancer therapy. SP-141, a novel designed small molecule MDM2 inhibitor, exerts excellent in vitro and in vivo anticancer activity. To facilitate the preclinical development of this candidate anticancer agent, we have developed an HPLC method for the quantitative analysis of SP-141. The method was validated to be precise, accurate, and specific, with a linear range of 16.2-32,400 ng/mL in plasma, 16.2-6480 ng/mL in homogenates of brain, heart, liver, kidneys, lungs, muscle and tumor, and 32.4-6480 ng/mL in spleen homogenates. The lower limit of quantification was 16.2 ng/mL in plasma and all the tissue homogenates, except for spleen homogenates, where it was 32.4 ng/mL. The intra- and inter-assay precisions (coefficient of variation) were between 0.86 and 13.39%, and accuracies (relative errors) ranged from -8.50 to 13.92%. The relative recoveries were 85.6-113.38%. SP-141 was stable in mouse plasma, modestly plasma bound and metabolized by S9 microsomal enzymes. We performed an initial pharmacokinetic study in tumor-bearing nude mice, demonstrating that SP-141 has a short half-life in plasma and wide tissue distribution. In summary, this HPLC method can be used in future preclinical and clinical investigations of SP-141.

Identification of a new class of MDM2 inhibitor that inhibits growth of orthotopic pancreatic tumors in mice

BACKGROUND & AIMS

The oncogene MDM2, which encodes an E3 ubiquitin ligase, is overexpressed in pancreatic cancers and is therefore a therapeutic target. Current inhibitors of MDM2 target the interaction between MDM2 and P53; these would have no effect on cancer cells that do not express full-length P53, including many pancreatic cancer cells. We searched for a compound that specifically inhibits MDM2 itself.

METHODS

We performed a virtual screen and structure-based design to identify specific inhibitors of MDM2. We tested the activities of compounds identified on viability, proliferation, and protein levels of HPAC, Panc-1, AsPC-1, and Mia-Paca-2 pancreatic cancer cell lines. We tested whether intraperitoneal injections of one of the compounds identified affected growth of xenograft tumors from Panc-1 cells, or orthotopic tumors from Panc-1 and AsPC-1 cells (injected into pancreata), in nude mice.

RESULTS

We identified a compound, called SP141, which bound directly to MDM2, promoting its auto-ubiquitination and degradation by the proteasome. The compound reduced levels of MDM2 in pancreatic cancer cell lines, as well as their proliferation, with 50% inhibitory concentrations <0.5 μM (0.38-0.50 μM). Increasing concentrations of SP141 induced increasing levels of apoptosis and G2-M-phase arrest of pancreatic cancer cell lines, whether or not they expressed functional P53. Injection of nude mice with SP141 (40 mg/kg/d) inhibited growth of xenograft tumors (by 75% compared with control mice), and led to regression of orthotopic tumors.

CONCLUSIONS

In a screen for specific inhibitors of MDM2, we identified a compound called SP141 that reduces levels of MDM2 in pancreatic cancer cell lines, as well as their proliferation and ability to form tumors in nude mice. SP141 is a new class of MDM2 inhibitor that promotes MDM2 auto-ubiquitination and degradation. It might be further developed as a therapeutic agent for pancreatic cancer.

The pyrido[b]indole MDM2 inhibitor SP-141 exerts potent therapeutic effects in breast cancer models

A requirement for Mouse Double Minute 2 (MDM2) oncogene activation has been suggested to be associated with cancer progression and metastasis, including breast cancer. To date, most MDM2 inhibitors have been designed to block the MDM2-p53-binding interphase, and have low or no efficacy against advanced breast cancer with mutant or deficient p53. Here we use a high-throughput screening and computer-aided, structure-based rational drug design, and identify a lead compound, SP-141, which can directly bind to MDM2, inhibit MDM2 expression and induce its autoubiquitination and proteasomal degradation. SP-141 has strong in vitro and in vivo antibreast cancer activity, with no apparent host toxicity. While further investigation is needed, our data indicate that SP-141 is a novel targeted therapeutic agent that may especially benefit patients with advanced disease.

Total Synthesis of Calothrixins A and B via Oxidative Radical Reaction of Cyclohexenone with Aminophenanthridinedione

Bioactive indolo[3,2-j]phenanthridine alkaloids, calothrixin B and its N-oxide derivative calothrixin A have been synthesized via an oxidative free radical reaction. calothrixin B is generated from the commercially available 2,4,5-trimethoxybenzaldehyde in only 7 steps. The key step in this synthesis is the Mn(OAc)₃ mediated oxidative free radical reaction of 9-(benzylamino)phenanthridine -7,10-dione with cyclohexenone to form 12-benzyl-12H-indolo[3,2-j]phenanthridine-7,13-dione.

A quantitative LC-MS/MS method for determination of SP-141, a novel pyrido[b]indole anticancer agent, and its application to a mouse PK study

In the present study, a specific and sensitive liquid chromatography-triple quadrupole mass spectrometry method was developed and validated for the determination of SP-141, a novel pyrido[b]indole anticancer agent. After a liquid-liquid extraction with n-hexane-dichloromethane-2-propanol (20:10:1, v/v/v) mixture, the analyte was separated on a Kinetex C18 column (50×2.1mm, 2.6μm) with mobile phases comprising of water (0.1% formic acid, v/v) and acetonitrile (0.1% formic acid, v/v) at a flow rate of 0.4mL/min. The test compound (SP-141) and the internal standard (SP-157) were analyzed in the multiple reaction-monitoring mode using the mass transitions m/z 325.1 → 282.0. The method was linear in the concentration range of 0.648-162ng/mL with coefficients of determination (R(2)) of 0.999 in mouse plasma. The lower limit of quantification was 0.648ng/mL. The intra- and inter-day assay precisions (coefficient of variation, %CV) were less than 4.2% and accuracies (relative error, %RE) ranged from -6.1% to 2.1%. The extraction recoveries were between 97.1 and 103.1% and the relative matrix effect was minimal. In addition, SP-141 was found to be stable in the plasma after three freeze-thaw cycles, at 37°C and 4°C for 24h, and at -80°C for 4 weeks. It was also stable in the stock solution at room temperature for 24h and after preparation in the autosampler for 36h. The validated method was successfully applied to an initial pharmacokinetic study of SP-141 in CD-1 mice following intraperitoneal and intravenous administrations.

Identification of the ZAK-MKK4-JNK-TGFβ signaling pathway as a molecular target for novel synthetic iminoquinone anticancer compound BA-TPQ

Identification and validation of molecular targets are considered as key elements in new drug discovery and development. We have recently demonstrated that a novel synthetic iminoquinone analog, termed [7-(benzylamino)- 1,3,4,8-tetrahydropyrrolo [4,3, 2-de]quinolin-8(1H)-one] (BA-TPQ), has significant anti-breast cancer activity both in vitro and in vivo, but the underlying molecular mechanisms are not fully understood. Herein, we report the molecular studies for BA-TPQ's effects on JNK and its upstream and downstream signaling pathways. The compound up-regulates the JNK protein levels by increasing its phosphorylation and decreasing its polyubiquitination-mediated degradation. It activates ZAK at the MAPKKK level and MKK4 at the MAPKK level. It also up-regulates the TGFβ2 mRNA level, which can be abolished by the JNK-specific inhibitor SP600125, but not TGFβ pathway-specific inhibitor SD-208, indicating that both JNK and TGFβ signaling pathways are activated by BA-TPQ and that the JNK pathway activation precedes TGFβ activation. The pro-apoptotic and anti-growth effects of BA-TPQ are significantly blocked by both the JNK and TGFβ pathway inhibitors. In addition, BA-TPQ activates the ZAK-MKK4-JNK pathway in MCF7 cells, but not normal MCF10A cells, demonstrating its cancer-specific activities. In conclusion, our results demonstrate that BA-TPQ activates the ZAK-MKK4-JNK-TGFβ signaling cascade as a molecular target for its anticancer activity.

Targeting MDM2-p53 interaction for cancer therapy: are we there yet?

Inactivation of the tumor suppressor p53 and/or overexpression of the oncogene MDM2 frequently occur in human cancers, and are associated with poor prognosis, advanced forms of the disease, and chemoresistance. MDM2, the major negative regulator of p53, induces p53 degradation and inactivates its tumor suppressing activity. In turn, p53 regulates MDM2 expression. This MDM2-p53 negative feedback loop has been widely studied and presents an attractive target for cancer therapy, with a few of the inhibitors of this interaction already having advanced into clinical trials. Additionally, there is an increasing interest in understanding MDM2's p53-independent activities in carcinogenesis and cancer progression, which may also have implications for cancer therapy. This review aims to highlight the various roles that the MDM2-p53 interaction plays in cancer, the p53 independent oncogenic activities of MDM2 and the various strategies that may be used to target MDM2 and the MDM2-p53 interaction. We will summarize the major preclinical and clinical evidences of MDM2 inhibitors for human cancer treatment and make suggestions to further improve efficacy and safety of this interesting class of cancer therapeutics.

Selective cytotoxicity, inhibition of cell cycle progression, and induction of apoptosis in human breast cancer cells by sesquiterpenoids from Inula lineariifolia Turcz

Four new sesquiterpenoid dimers (lineariifolianoids E-H, 1-4), five new sesquiterpenoids (5-9), and seven known sesquiterpenoids (10-16) were isolated from the aerial parts of Inula lineariifolia Turcz. Their structures were determined by spectroscopic data analysis and X-ray diffraction studies. The compounds were then evaluated for their in vitro cytotoxicity against two human breast cancer cell lines (MCF-7 and MDA-MB-231) and one normal breast cell line (MCF-10A). Lineariifolianoid E (1) showed IC50 values of 1.56 μM and 2.75 μM against MCF-7 and MDA-MB-231, respectively. However, lineariifolianoid E demonstrated low toxicity to MCF-10A cells, which indicated a selective cytotoxicity for tumor cells. Further studies also presented that lineariifolianoid E had significant, dose-dependent effects on cell cycle progression and apoptosis in breast cancer cells.

Natural product MDM2 inhibitors: anticancer activity and mechanisms of action

The mdm2 oncogene has recently been suggested to be a valuable target for cancer therapy and prevention. Overexpression of mdm2 is often seen in various human cancers and correlates with high-grade, late-stage, and more treatment-resistant tumors. The MDM2-p53 auto-regulatory loop has been extensively investigated and is an attractive cancer target, which indeed has been the main focus of anti-MDM2 drug discovery. Much effort has been expended in the development of small molecule MDM2 antagonists targeting the MDM2-p53 interaction, and a few of these have advanced into clinical trials. However, MDM2 exerts its oncogenic activity through both p53-dependent and -independent mechanisms. Recently, there is an increasing interest in identifying natural MDM2 inhibitors; some of them have been shown to decrease MDM2 expression and activity in vitro and in vivo. These identified natural MDM2 inhibitors include a plethora of diverse chemical frameworks, ranging from flavonoids, steroids, and sesquiterpenes to alkaloids. In addition to a brief review of synthetic MDM2 inhibitors, this review focuses on natural product MDM2 inhibitors, summarizing their biological activities in vitro and in vivo and the underlying molecular mechanisms of action, targeting MDM2 itself, regulators of MDM2, and/or the MDM2-p53 interaction. These MDM2 inhibitors can be used alone or in combination with conventional treatments, improving the prospects for cancer therapy and prevention. Their complex and unique molecular architectures may provide a stimulus for developing synthetic analogs in the future.

Total synthesis of zyzzyanones A-D

Zyzzyanones A-D is a group of biologically active marine alkaloids isolated from Australian marine sponge Zyzzya fuliginosa. They contain a unique bispyrroloquinone ring system as the core structure. The first total synthesis of all four zyzzyanones is described here. The synthesis of these alkaloids started from a previously known 6-benzylamino indole-4,7-quinone derivative and involves 6-7 steps. The key step in the synthesis involves the construction of a pyrrole ring in one step using a Mn(OAc)3 mediated oxidative free radical cyclization reaction of a 6-benzylamino indole-4,7-quinone derivative with 4-benzyloxyphenyl acetaldehyde diethyl acetal in CH3CN.

A survey of marine natural compounds and their derivatives with anti-cancer activity reported in 2011

Cancer continues to be a major public health problem despite the efforts that have been made in the search for novel drugs and treatments. The current sources sought for the discovery of new molecules are plants, animals and minerals. During the past decade, the search for anticancer agents of marine origin to fight chemo-resistance has increased greatly. Each year, several novel anticancer molecules are isolated from marine organisms and represent a renewed hope for cancer therapy. The study of structure-function relationships has allowed synthesis of analogues with increased efficacy and less toxicity. In this report, we aim to review 42 compounds of marine origin and their derivatives that were published in 2011 as promising anticancer compounds.

Natural product ginsenoside 25-OCH3-PPD inhibits breast cancer growth and metastasis through down-regulating MDM2

Although ginseng and related herbs have a long history of utility for various health benefits, their application in cancer therapy and underlying mechanisms of action are not fully understood. Our recent work has shown that 20(S)-25-methoxyl-dammarane-3β, 12β, 20-triol (25-OCH₃-PPD), a newly identified ginsenoside from Panax notoginseng, exerts activities against a variety of cancer cells in vitro and in vivo. This study was designed to investigate its anti-breast cancer activity and the underlying mechanisms of action. We observed that 25-OCH₃-PPD decreased the survival of breast cancer cells by induction of apoptosis and G1 phase arrest and inhibited the growth of breast cancer xenografts in vivo. We further demonstrated that, in a dose- and time-dependent manner, 25-OCH₃-PPD inhibited MDM2 expression at both transcriptional and post-translational levels in human breast cancer cells with various p53 statuses (wild type and mutant). Moreover, 25-OCH₃-PPD inhibited in vitro cell migration, reduced the expression of epithelial-to-mesenchymal transition (EMT) markers, and prevented in vivo metastasis of breast cancer. In summary, 25-OCH₃-PPD is a potential therapeutic and anti-metastatic agent for human breast cancer through down-regulating MDM2. Further preclinical and clinical development of this agent is warranted.

Synthesis of chalcones with anticancer activities

Several chalcones were synthesized and their in vitro cytotoxicity against various human cell lines, including human breast adenocarcinoma cell line MCF-7, human lung adenocarcinoma cell line A549, human prostate cancer cell line PC3, human adenocarcinoma cell line HT-29 (colorectal cancer) and human normal liver cell line WRL-68 was evaluated. Most of the compounds being active cytotoxic agents, four of them with minimal IC₅₀ values were chosen and studied in detail with MCF-7 cells. The compounds 1, 5, 23, and 25 were capable in eliciting apoptosis in MCF-7 cells as shown by multiparameter cytotoxicity assay and caspase-3/7, -8, and -9 activities (p < 0.05). The ROS level showed 1.3-fold increase (p < 0.05) at the low concentrations used and thus it was concluded that the compounds increased the ROS level eventually leading to apoptosis in MCF-7 cells through intrinsic as well as extrinsic pathways.

Preclinical evaluation of anticancer efficacy and pharmacological properties of FBA-TPQ, a novel synthetic makaluvamine analog

We have recently designed and synthesized a novel iminoquinone anticancer agent, 7-(4-fluorobenzylamino)-1,3,4,8-tetrahydropyrrolo[4,3,2-de]quinolin-8(1H)-one (FBA-TPQ) and initiated its preclinical development. Herein we investigated its efficacy, safety, and pharmacokinetics in in vitro and in vivo models of human pancreatic cancer. Our results demonstrated that FBA-TPQ inhibited pancreatic cancer cell growth, induced apoptosis, and caused cell cycle arrest in vitro. It inhibited the growth of xenograft tumors with minimal host toxicity. To facilitate future preclinical and clinical development of the agent, we also developed and validated a Rapid Resolution Liquid Chromatography (RRLC) method for quantitative analysis of FBA-TPQ in plasma and tissue samples. The method was found to be precise, accurate, and specific. Using this method, we carried out in vitro and in vivo evaluations of the pharmacological properties of FBA-TPQ, including stability in plasma, plasma protein binding, metabolism by S9 enzymes, plasma pharmacokinetics, and tissue distribution. Our results indicate that FBA-TPQ is a potential therapeutic agent for pancreatic cancer, providing a basis for future preclinical and clinical development.

JKA97, a novel benzylidene analog of harmine, exerts anti-cancer effects by inducing G1 arrest, apoptosis, and p53-independent up-regulation of p21

JKA97, a benzylidene analog of harmine, has been found to be a promising drug candidate for human cancer therapy, although the underlying molecular mechanisms have not been fully demonstrated. In this study, we evaluated the effects of JKA97 on human breast cancer cells in vitro and in vivo. JKA97 inhibited the growth and proliferation of MCF7 (p53 wild-type), MCF7 (p53 knockdown), and MDA-MB-468 (p53 mutant) cells in a dose-dependent manner. Treatment with JKA97 arrested breast cancer cells in G1 phase and induced apoptosis. JKA97 also significantly suppressed the growth of MCF7 and MDA-MB-468 xenograft tumors. It regulated the expression levels of G1 phase regulators, such as p21, p27, cyclinE, and cylinD1. JKA97 activated p21 transcription, independent of p53, but had little effect on p21 protein stability/degradation. In summary, our results suggest that JKA97 inhibits human breast cancer cell growth through activating p21, independent of p53, which provides a basis for developing this compound as a novel drug for human breast cancer therapy.

Marine pyrroloiminoquinone alkaloids

Recent reports on the synthetic studies of marine pyrroloiminoquinone alakloids and their analogs are reviewed.