A novel sulindac derivative protects against oxidative damage by a cyclooxygenase-independent mechanism.

Oxidative damage is believed to play a major role in the etiology of many age-related diseases and the normal aging process. We previously reported that sulindac, a cyclooxygenase (COX) inhibitor and FDA approved anti-inflammatory drug, has chemoprotective activity in cells and intact organs by initiating a pharmacological preconditioning response, similar to ischemic preconditioning (IPC). The mechanism is independent of its COX inhibitory activity as suggested by studies on the protection of the heart against oxidative damage from ischemia/reperfusion and retinal pigmented endothelial (RPE) cells against chemical oxidative and UV damage . Unfortunately, sulindac is not recommended for long-term use due to toxicities resulting from its COX inhibitory activity. To develop a safer and more efficacious derivative of sulindac, we screened a library of indenes and identified a lead compound, MCI-100, that lacked significant COX inhibitory activity but displayed greater potency than sulindac to protect RPE cells against oxidative damage. MCI-100 also protected the intact rat heart against ischemia/reperfusion damage following oral administration. The chemoprotective activity of MCI-100 involves a preconditioning response similar to sulindac, which is supported by RNA sequencing data showing common genes that are induced or repressed by sulindac or MCI-100 treatment. Both sulindac and MCI-100 protection against oxidative damage may involve modulation of Wnt/ß-catenin signaling resulting in proliferation while inhibiting TGFb signaling leading to apoptosis. In summary MCI-100, is more active than sulindac in protecting cells against oxidative damage, but without significant NSAID activity, and could have therapeutic potential in treatment of diseases that involve oxidative damage. Significance Statement In this study, we describe a novel sulindac derivative, MCI-100, that lacks significant COX inhibitory activity, but is appreciably more potent than sulindac in protecting retinal pigmented epithelial (RPE) cells against oxidative damage. Oral administration of MCI-100 markedly protected the rat heart against ischemia/reperfusion damage. MCI-100 has potential therapeutic value as a drug candidate for age-related diseases by protecting cells against oxidative damage and preventing organ failure.

Novel thiazolidine derivatives as potent selective pro-apoptotic agents.

A series of 2-arylthiazolidine-4-carboxylic acid amide derivatives were synthesized and their cytotoxic activity against three cancer cell lines (PC-3, SKOV3 and MDA-MB231) was evaluated. Various structural modifications were tried including modifications of the length of the amide chain and modifications of the 2-aryl part using disubstituted phenyl and thiophene derivatives. The structure activity relationship was evaluated based on the in vitro biological evaluation against the above mentioned three cancer cell lines. The most selective compounds towards cancer cells were further evaluated against DLD-1, NCI-H520, Du145, MCF-7 and NCI-N87 cancer cells. The dodecyl amide having the 4-bromothienyl as the 2-aryl, compound 2e, exhibited the highest selectivity for cancer cells vs non-tumor cells. Mechanistic studies of the anticancer effect of compound 2e in prostate cancer PC-3 and colorectal cancer DLD-1 cells revealed that 2e could prevent the cell cycle in the G0/G1 phase by up-regulating the expression of p21 and reducing the expression of CDK2 and cyclin E. It increased the pro-apoptotic protein Bax and cleaved caspase 3, and down-regulated the expression of anti-apoptotic protein Bcl-2 to induce apoptosis. In addition, 2e also downregulated AKT, N-cadherin, and vimentin proteins expression giving indication that 2e inhibit the PI3K/AKT pathway to regulate cell cycle arrest and induce apoptosis, and can regulate the expression of epithelial-mesenchymal transition-related proteins.

Discovery of trisubstituted pyrazolines as a novel scaffold for the development of selective phosphodiesterase 5 inhibitors.

Celecoxib, is a selective cyclooxygenase-2 (COX2) inhibitor with a 1,5-diaryl pyrazole scaffold. Celecoxib has a better safety profile compared to other COX2 inhibitors having side effects of systemic hypertension and thromboembolic complications. This may be partly attributed to an off-target activity involving phosphodiesterase 5 (PDE5) inhibition and the potentiation of NO/cGMP signalling allowing coronary vasodilation and aortic relaxation. Inspired by the structure of celecoxib, we synthesized a chemically diverse series of compounds containing a 1,3,5-trisubstituted pyrazoline scaffold to improve PDE5 inhibitory potency, while eliminating COX2 inhibitory activity. SAR studies for PDE5 inhibition revealed an essential role for a carboxylic acid functionality at the 1-phenyl and the importance of the non-planar pyrazoline core over the planar pyrazole with the 5-phenyl moiety tolerating a range of substituents. These modifications led to new PDE5 inhibitors with approximately 20-fold improved potency to inhibit PDE5 and no COX-2 inhibitory activity compared with celecoxib. PDE isozyme profiling of compound 11 revealed a favorable selectivity profile. These results suggest that trisubstituted pyrazolines provide a promising scaffold for further chemical optimization to identify novel PDE5 inhibitors with potential for less side effects compared with available PDE5 inhibitors used for the treatment of penile erectile dysfunction and pulmonary hypertension.

Extending the use of tadalafil scaffold: Development of novel selective phosphodiesterase 5 inhibitors and histone deacetylase inhibitors.

Herein we present the synthesis and characterization of a novel chemical series of tadalafil analogues that display different pharmacological profiles. Compounds that have the 6R, 12aR configuration and terminal carboxylic acid group at the side chain arising from the piperazinedione nitrogen were potent PDE5 inhibitors, with compound 11 having almost equal potency to tadalafil and superior selectivity over PDE11, the most common off-target for tadalafil. Modifying the stereochemistry into 6S, 12aS configuration and adopting the hydroxamic acid moiety as a terminal group gave rise to compounds that only inhibited HDAC. Dual PDE5/HDAC inhibition could be achieved with compounds having 6R, 12aR configuration and hydroxamic acid moiety as a terminal group. The anticancer activity of the synthesized compounds was evaluated against a diverse number of cell lines of different origin. The compounds elicited anticancer activity against cell lines belonging to lymphoproliferative cancer as well as solid tumors. Despite the previous reports suggesting anticancer activity of PDE5 inhibitors, the growth inhibitory activity of the compounds seemed to be solely dependent on HDAC inhibition. Compound 26 (pan HDAC IC50 = 14 nM, PDE5 IC50 = 46 nM) displayed the most potent anticancer activity in the present series and was shown to induce apoptosis in Molt-4 cells. HDAC isoform selectivity testing for compound 26 showed that it is more selective for HDAC6 and 8 over HDAC1 by more than 20-fold.

Design and synthesis of 1,2,4-triazolo[1,5-a]pyrimidine derivatives as PDE 4B inhibitors endowed with bronchodilator activity.

A series of 1,2,4-triazolo[1,5-a]pyrimidine derivatives was designed, synthesized, and screened for their phosphodiesterase (PDE 4B) inhibitory activity and bronchodilation ability. Compound 7e showed 41.80% PDE 4B inhibition at 10 µM. Eight compounds were screened for their bronchodilator activity, where compounds 7f and 7e elicited promising bronchodilator activity with EC50 values of 18.6 and 57.1 µM, respectively, compared to theophylline (EC50 = 425 µM). Molecular docking at the PDE 4B active site revealed a binding mode and docking scores comparable to those of a reference ligand, consistent with their PDE 4B inhibition activity.

Exploiting RAS Nucleotide Cycling as a Strategy for Drugging RAS-Driven Cancers.

Oncogenic mutations in RAS genes result in the elevation of cellular active RAS protein levels and increased signal propagation through downstream pathways that drive tumor cell proliferation and survival. These gain-of-function mutations drive over 30% of all human cancers, presenting promising therapeutic potential for RAS inhibitors. However, many have deemed RAS "undruggable" after nearly 40 years of failed drug discovery campaigns aimed at identifying a RAS inhibitor with clinical activity. Here we review RAS nucleotide cycling and the opportunities that RAS biochemistry presents for developing novel RAS inhibitory compounds. Additionally, compounds that have been identified to inhibit RAS by exploiting various aspects of RAS biology and biochemistry will be covered. Our current understanding of the biochemical properties of RAS, along with reports of direct-binding inhibitors, both provide insight on viable strategies for the discovery of novel clinical candidates with RAS inhibitory activity.

Synthesis and biological evaluation of certain hydrazonoindolin-2-one derivatives as new potent anti-proliferative agents.

In connection with our research program on the development of novel indolin-2-one-based anticancer candidates, herein we report the design and synthesis of different series of hydrazonoindolin-2-ones 3a-e, 5a-e, 7a-c, and 10a-l. The synthesised derivatives were in vitro evaluated for their anti-proliferative activity towards lung A-549, colon HT-29, and breast ZR-75 human cancer cell lines. Compounds 5b, 5c, 7b, and 10e emerged as the most potent derivatives with average IC50 values of 4.37, 2.53, 2.14, and 4.66 µM, respectively, which are superior to Sunitinib (average IC50 = 8.11 µM). Furthermore, compounds 7b and 10e were evaluated for their effects on cell cycle progression and levels of phosphorylated retinoblastoma (Rb) protein in the A-549 cancer cell line. Moreover, 7b and 10e inhibited the cell growth of the multidrug-resistant lung cancer NCI-H69AR cell line with IC50 = 16 µM. In addition, the cytotoxic activities of 7b and 10e were assessed towards three non-tumorigenic cell lines (Intestine IEC-6, Breast MCF-10A, and Fibroblast Swiss-3t3) where both compounds displayed mean tumor selectivity index (1.6 and 1.8) higher than that of Sunitinib (1.4).

Design and synthesis of novel annulated thienopyrimidines as phosphodiesterase 5 (PDE5) inhibitors.

Novel cycloalkene-fused thienopyrimidine analogues with enhanced phosphodiesterase 5 (PDE5) inhibitory properties are presented. The structure of the reported scaffold was modulated through variation of the terminal cycloalkene ring size, as well as by varying the substituents at position 4 through the attachment of different groups including aniline, benzylamine, cyclohexylethylamine, methyl/acetyl/aryl piperazines, and aryl hydrazones. Compound 15Y with a benzylamine substituent and cycloheptene as terminal ring showed the highest PDE5 inhibitory activity with an IC50 value as low as 190 nM and with good selectivity versus PDE7 and PDE9.

Rad6 upregulation promotes stem cell-like characteristics and platinum resistance in ovarian cancer.

Ovarian cancer is the fifth most deadly cancer in women in the United States and despite advances in surgical and chemotherapeutic treatments survival rates have not significantly improved in decades. The poor prognosis for ovarian cancer patients is largely due to the extremely high (80%) recurrence rate of ovarian cancer and because the recurrent tumors are often resistant to the widely utilized platinum-based chemotherapeutic drugs. In this study, expression of Rad6, an E2 ubiquitin-conjugating enzyme, was found to strongly correlate with ovarian cancer progression. Furthermore, in ovarian cancer cells Rad6 was found to stabilize ß-catenin promoting stem cell-related characteristics, including expression of stem cell markers and anchorage-independent growth. Cancer stem cells can promote chemoresistance, tumor recurrence and metastasis, all of which are limiting factors in treating ovarian cancer. Thus it is significant that Rad6 overexpression led to increased resistance to the chemotherapeutic drug carboplatin and correlated with tumor cell invasion. These findings show the importance of Rad6 in ovarian cancer and emphasize the need for further studies of Rad6 as a potential target for the treatment of ovarian cancer.

Design and Synthesis of Substituted Pyridazinone-1-Acetylhydrazones as Novel Phosphodiesterase 4 Inhibitors.

A series of novel pyridazin-6-one-1-acetylhydrazone hybrids were rationally designed to inhibit phosphodiesterase 4 (PDE4B). The prepared compounds were evaluated for their in vitro ability to inhibit the PDE4B enzyme; several of these compounds showed moderate activity compared to the reference drug, rolipram. Compounds 6, 12, and 14 emerged as the most potent inhibitors in this series. The [3-(4-methoxyphenyl)-6-oxo-5,6-dihydro-4H-pyridazin-1-yl]acetic acid [1-(3,4,5-trimethoxyphenyl)ethylidene]hydrazide (12) showed an IC50 value of 13 µM against PDE4B. Docking of 6, 12, and 14 into the active site of PDE4B illustrates their possible binding mode and provides insights for further optimization of this drug scaffold.

Chemoprevention in gastrointestinal physiology and disease. Anti-inflammatory approaches for colorectal cancer chemoprevention.

Colorectal cancer (CRC) is one of the most common human malignancies and a leading cause of cancer-related deaths in developed countries. Identifying effective preventive strategies aimed at inhibiting the development and progression of CRC is critical for reducing the incidence and mortality of this malignancy. The prevention of carcinogenesis by anti-inflammatory agents including nonsteroidal anti-inflammatory drugs (NSAIDs), selective cyclooxygenase-2 (COX-2) inhibitors, and natural products is an area of considerable interest and research. Numerous anti-inflammatory agents have been identified as potential CRC chemopreventive agents but vary in their mechanism of action. This review will discuss the molecular mechanisms being studied for the CRC chemopreventive activity of NSAIDs (i.e., aspirin, sulindac, and ibuprofen), COX-2 inhibitors (i.e., celecoxib), natural products (i.e., curcumin, resveratrol, EGCG, genistein, and baicalein), and metformin. A deeper understanding of how these anti-inflammatory agents inhibit CRC will provide insight into the development of potentially safer and more effective chemopreventive drugs.

An undesired effect of chemotherapy: gemcitabine promotes pancreatic cancer cell invasiveness through reactive oxygen species-dependent, nuclear factor κB- and hypoxia-inducible factor 1α-mediated up-regulation of CXCR4.

Recently, we have shown that CXCL12/CXCR4 signaling plays an important role in gemcitabine resistance of pancreatic cancer (PC) cells. Here, we explored the effect of gemcitabine on this resistance mechanism. Our data demonstrate that gemcitabine induces CXCR4 expression in two PC cell lines (MiaPaCa and Colo357) in a dose- and time-dependent manner. Gemcitabine-induced CXCR4 expression is dependent on reactive oxygen species (ROS) generation because it is abrogated by pretreatment of PC cells with the free radical scavenger N-acetyl-L-cysteine. CXCR4 up-regulation by gemcitabine correlates with time-dependent accumulation of NF-κB and HIF-1α in the nucleus. Enhanced binding of NF-κB and HIF-1α to the CXCR4 promoter is observed in gemcitabine-treated PC cells, whereas their silencing by RNA interference causes suppression of gemcitabine-induced CXCR4 expression. ROS induction upon gemcitabine treatment precedes the nuclear accumulation of NF-κB and HIF-1α, and suppression of ROS diminishes these effects. The effect of ROS on NF-κB and HIF-1α is mediated through activation of ERK1/2 and Akt, and their pharmacological inhibition also suppresses gemcitabine-induced CXCR4 up-regulation. Interestingly, our data demonstrate that nuclear accumulation of NF-κB results from phosphorylation-induced degradation of IκBα, whereas HIF-1α up-regulation is NF-κB-dependent. Lastly, our data demonstrate that gemcitabine-treated PC cells are more motile and exhibit significantly greater invasiveness against a CXCL12 gradient. Together, these findings reinforce the role of CXCL12/CXCR4 signaling in gemcitabine resistance and point toward an unintended and undesired effect of chemotherapy.

Novel quinazolin-4(3H)-one/Schiff base hybrids as antiproliferative and phosphodiesterase 4 inhibitors: design, synthesis, and docking studies.

A novel series of quinazolin-4(3H)-one/Schiff base hybrids was rationally designed and synthesized. The prepared compounds were evaluated for in vitro activity to inhibit phosphodiesterase 4 (PDE4), where several of them showed good-to-moderate activity compared to rolipram. Compound 7 showed potent PDE4 inhibition in this series, with an IC50 of 1.60 µM. Compounds that showed PDE4 inhibition were further assessed for antiproliferative activity using different human tumor cell lines. Compound 10 exhibited significant antiproliferative activity with IC50 values of 140, 79, and 320 nM in breast, lung, and colon tumor cells, respectively. Docking of compound 7 in the active site of PDE4B illustrates its possible binding mode and provides insight for further optimizations of this novel scaffold for inhibiting PDE4.

Novel non-cyclooxygenase inhibitory derivatives of naproxen for colorectal cancer chemoprevention.

A structure-based medicinal chemistry strategy was applied to design new naproxen derivatives that show growth inhibitory activity against human colon tumor cells through a cyclooxygenase (COX)-independent mechanism. In vitro testing of the synthesized compounds against the human HT-29 colon tumor cell line revealed enhanced growth inhibitory activity compared to the parent naproxen with 3a showing IC50 of 11.4 µM (two orders of magnitude more potent than naproxen). Selectivity of 3a was investigated against a panel of three tumor and one normal colon cell lines and showed up to six times less toxicity against normal colonocytes. Compound 3a was shown to induce dose-dependent apoptosis of HT116 colon tumor cells as evidenced by measuring the activity of caspases-3 and 7. None of the synthesized compounds showed activity against COX-1 or COX-2 isozymes, confirming a COX-independent mechanism of action. Compound 3k was found to have no ulcerogenic effect in rats as indicated by electron microscope scanning of the stomach after oral administration. A pharmacophore model was developed for elucidating structure-activity relationships and subsequent chemical optimization for this series of compounds as colorectal cancer chemopreventive drugs.

N-Benzylated 5-Hydroxybenzothiophene-2-carboxamides as Multi-Targeted Clk/Dyrk Inhibitors and Potential Anticancer Agents.

Numerous studies have reported that Dyrk1A, Dyrk1B, and Clk1 are overexpressed in multiple cancers, suggesting a role in malignant disease. Here, we introduce a novel class of group-selective kinase inhibitors targeting Dyrk1A, Dyrk1B, and Clk1. This was achieved by modifying our earlier selective Clk1 inhibitors, which were based on the 5-methoxybenzothiophene-2-carboxamide scaffold. By incorporating a 5-hydroxy group, we increased the potential for additional hydrogen bond interactions that broadened the inhibitory effect to include Dyrk1A and Dyrk1B kinases. Within this series, compounds 12 and 17 emerged as the most potent multi-kinase inhibitors against Dyrk1A, Dyrk1B, and Clk1. Furthermore, when assessed against the most closely related kinases also implicated in cancer, the frontrunner compounds revealed additional inhibitory activity against Haspin and Clk2. Compounds 12 and 17 displayed high potency across various cancer cell lines with minimal effect on non-tumor cells. By examining the effect of these inhibitors on cell cycle distribution, compound 17 retained cells in the G2/M phase and induced apoptosis. Compounds 12 and 17 could also increase levels of cleaved caspase-3 and Bax, while decreasing the expression of the antiapoptotic Bcl-2 protein. These findings support the further study and development of these compounds as novel anticancer therapeutics.

A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer.

Here, we describe a novel pan-RAS inhibitor, ADT-007, that potently inhibited the growth of RAS mutant cancer cells irrespective of the RAS mutation or isozyme. RAS WT cancer cells with activated RAS from upstream mutations were equally sensitive. Conversely, cells from normal tissues or RAS WT cancer cells harboring downstream BRAF mutations were insensitive. Insensitivity to ADT-007 was attributed to low activated RAS levels and metabolic deactivation by UDP-glucuronosyltransferases expressed in normal cells but repressed in RAS mutant cancer cells. Cellular, biochemical, and biophysical experiments show ADT-007 binds nucleotide-free RAS to block GTP activation of RAS and MAPK/AKT signaling. Local administration of ADT-007 strongly inhibited tumor growth in syngeneic immune-competent and xenogeneic immune-deficient mouse models of colorectal and pancreatic cancer while activating innate and adaptive immunity in the tumor immune microenvironment. Oral administration of ADT-007 prodrug inhibited tumor growth, supporting further development of this novel class of pan-RAS inhibitors for treating RAS-driven cancers. SIGNIFICANCE: ADT-007 is a 1 st -in-class pan-RAS inhibitor with ultra-high potency and unique selectivity for cancer cells with mutant or activated RAS capable of circumventing resistance and activating antitumor immunity. Further development of ADT-007 analogs or prodrugs with oral bioavailability as a generalizable monotherapy or combined with immunotherapy is warranted.

New NSAID targets and derivatives for colorectal cancer chemoprevention.

Clinical and preclinical studies provide strong evidence that nonsteroidal anti-inflammatory drugs (NSAIDs) can prevent numerous types of cancers, especially colorectal cancer. Unfortunately, the depletion of physiologically important prostaglandins due to cyclooxygenase (COX) inhibition results in potentially fatal toxicities that preclude the long-term use of NSAIDs for cancer chemoprevention. While studies have shown an involvement of COX-2 in colorectal tumorigenesis, other studies suggest that a COX-independent target may be at least partially responsible for the antineoplastic activity of NSAIDs. For example, certain NSAID derivatives have been identified that do not inhibit COX-2 but have demonstrated efficacy to suppress carcinogenesis with potential for reduced toxicity. A number of alternative targets have also been reported to account for the tumor cell growth inhibitory activity of NSAIDs, including the inhibition of cyclic guanosine monophosphate phosphodiesterases (cGMP PDEs), generation of reactive oxygen species (ROS), the suppression of the apoptosis inhibitor protein, survivin, and others. Here, we review several promising mechanisms that are being targeted to develop safer and more efficacious NSAID derivatives for colon cancer chemoprevention.

Trisubstituted and tetrasubstituted pyrazolines as a novel class of cell-growth inhibitors in tumor cells with wild type p53.

Derivatives with scaffolds of 1,3,5-tri-substituted pyrazoline and 1,3,4,5-tetra-substituted pyrazoline were synthesized and tested for their inhibitory effects versus the p53(+/+) HCT116 and p53(-/-) H1299 human tumor cell lines. Several compounds were active against the two cell lines displaying IC50 values in the low micromolar range with a clearly more pronounced effect on the p53(+/+) HCT116 cells. The compound class shows excellent developability due to the modular synthesis, allowing independent optimization of all three to four key substituents to improve the properties of the molecules.

Hypoxia-regulated microRNAs in human cancer.

Hypoxia plays an important role in the tumor microenvironment by allowing the development and maintenance of cancer cells, but the regulatory mechanisms by which tumor cells adapt to hypoxic conditions are not yet well understood. MicroRNAs are recognized as a new class of master regulators that control gene expression and are responsible for many normal and pathological cellular processes. Studies have shown that hypoxia inducible factor 1 (HIF1) regulates a panel of microRNAs, whereas some of microRNAs target HIF1. The interaction between microRNAs and HIF1 can account for many vital events relevant to tumorigenesis, such as angiogenesis, metabolism, apoptosis, cell cycle regulation, proliferation, metastasis, and resistance to anticancer therapy. This review will summarize recent findings on the roles of hypoxia and microRNAs in human cancer and illustrate the machinery by which microRNAs interact with hypoxia in tumor cells. It is expected to update our knowledge about the regulatory roles of microRNAs in regulating tumor microenvironments and thus benefit the development of new anticancer drugs.

MicroRNAs are involved in the self-renewal and differentiation of cancer stem cells.

MicroRNAs (miRNAs) are small non-coding RNA molecules, whose primary function is to regulate gene expression at the post-transcriptional/translational levels. MiRNAs play crucial roles in normal biological processes and are commonly dys-regulated in human diseases. Stem cells are regarded as the "mother" cells of all types of differentiated cells that comprise tissues and organs of the body. A novel hypothesis proposes that tumors are composed of heterogeneous cells derived from cancer stem cells, which have self-renewal and differentiation capabilities similar to those of normal stem cells. Cancer stem cells have been isolated and characterized from various tumors. Given recent studies supporting the critical regulatory roles of miRNAs in the self-renewal and differentiation of cancer stem cells, better understanding the functions of miRNAs will provide invaluable insights into the prevention of tumorigenesis and tumor progression. In this review, we will summarize the research progress in the study of miRNAs involved in the self-renewal and differentiation of cancer stem cells.