scholarly journals The Mechanism of Action of Cyclophosphamide and Its Consequences for the Development of a New Generation of Oxazaphosphorine Cytostatics

2020 ◽  
Vol 88 (4) ◽  
pp. 42
Author(s):  
Georg Voelcker
Keyword(s):  
Mechanism Of Action ◽  
Active Metabolite ◽  
Dna Alkylation ◽  
In Vivo Metabolism ◽  
Pharmacologically Active ◽  
New Generation ◽  
Anti Tumor Activity ◽  
Oxazaphosphorine Cytostatics

Although cyclophosphamide (CP) has been used successfully in the clinic for over 50 years, it has so far not been possible to elucidate the mechanism of action and to use it for improvement. This was not possible because the basis of the mechanism of action of CP, which was found by lucky coincidence, is apoptosis, the discovery of which was honored with the Nobel Prize only in 2002. Another reason was that results from cell culture experiments were used to elucidate the mechanism of action, ignoring the fact that in vivo metabolism differs from in vitro conditions. In vitro, toxic acrolein is formed during the formation of the cytotoxic metabolite phosphoreamidemustard (PAM), whereas in vivo proapoptotic hydroxypropanal (HPA) is formed. The CP metabolites formed in sequence 4-hydroxycyclophosphamide (OHCP) are the main cause of toxicity, aldophosphamide (ALDO) is the pharmacologically active metabolite and HPA amplifies the cytotoxic apoptosis initiated by DNA alkylation by PAM. It is shown that toxicity is drastically reduced but anti-tumor activity strongly increased by the formation of ALDO bypassing OHCP. Furthermore, it is shown that the anti-tumor activity against advanced solid P388 tumors that grow on CD2F1 mice is increased by orders of magnitude if DNA damage caused by a modified PAM is poorly repairable.

scholarly journals Lack of blocking activity in anti-CTLA-4 antibodies reduces toxicity, but not anti-tumor efficacy

2021 ◽  
Author(s):  
Erica L Stone ◽  
Kyle P Carter ◽  
Ellen K Wagner ◽  
Michael A Asensio ◽  
Emily Benzie ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Checkpoint Inhibitor ◽  
Checkpoint Inhibition ◽  
Treg Depletion ◽  
Primary Mechanism ◽  
Improved Outcomes ◽  
Immune Oncology ◽  
Anti Tumor Activity

Anti-CTLA-4 antibodies such as ipilimumab were among the first immune-oncology agents to show significantly improved outcomes for patients. However, existing anti-CTLA-4 therapies fail to induce a response in a majority of patients and can induce severe, immune-related adverse events. It has been assumed that checkpoint inhibition, i.e., blocking the interaction between CTLA-4 and its ligands, is the primary mechanism of action for ipilimumab. In this study we present evidence that checkpoint inhibition is not a primary mechanism of action for efficacy of anti-CTLA-4 antibodies. Instead, the primary mechanism for efficacy is FcR-mediated Treg depletion in the tumor microenvironment. First, we identified a monoclonal antibody (mAb) that binds to CTLA-4 at an epitope that differs from ipilimumab's by only a few amino acids, yet has limited checkpoint inhibitor activity. Surprisingly, the weak checkpoint inhibitor has superior anti-tumor activity compared to ipilimumab in a murine model. The weak checkpoint inhibitor also induces less Treg proliferation and has increased ability to induce in vitro FcR signaling and in vivo depletion of intratumoral Tregs. Further experiments showed that the enhanced FcR activity of the weak checkpoint inhibitor likely contributes to its enhanced anti-tumor activity. Importantly, we also showed that weak checkpoint inhibition was associated with lower toxicity in murine models. Our work suggests that new anti-CTLA-4 drugs should be optimized for Treg depletion rather than checkpoint inhibition.

Eradication of Tumors in Pre-Clinical Models of Multiple Myeloma by Anti-CS1 Monoclonal Antibody HuLuc63: Mechanism of Action Studies.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3503-3503 ◽  
Author(s):  
Audie Rice ◽  
Myles Dillon ◽  
Anne van Abbema ◽  
Lynne Jesaitis ◽  
Melanie Wong ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Mechanism Of Action ◽  
Xenograft Model ◽  
Fc Receptor ◽  
Cell Surface Glycoprotein ◽  
Xenograft Models ◽  
Anti Tumor Activity ◽  
Tumor Eradication

Abstract Introduction: We have recently shown that CS1 (CD2 subset 1, CRACC, SLAMF7), a cell surface glycoprotein of the CD2 family, is uniformly expressed on myeloma cells from multiple myeloma (MM) patients. Based on its high expression in MM and limited expression in normal cells, we propose CS1 as a novel and specific antibody target for the treatment of MM. Methods: A panel of monoclonal anti-CS1 antibodies (mAbs) was generated to identify a potential therapeutic candidate. MAb clones MuLuc63 and MuLuc90 were selected for testing in CS1 positive MM xenograft models in vivo in severe combined immunodeficient mice. HuLuc63, a humanized IgG1 version of MuLuc63, was generated as the potential therapeutic candidate for the treatment of MM. HuLuc63 and Fc-modified versions of HuLuc63 were tested for anti-tumor activity in mouse models vivo. In vitro antibody-dependent cellular cytotoxicity (ADCC) assays were performed to define the potential mechanism of action for HuLuc63. Results: Both MuLuc63 and MuLuc90 exhibited significant in vivo anti-tumor activity compared to isotype control antibodies in the L363 MM xenograft model. MuLuc63 was significantly more potent, resulting in rapid tumor eradication in most of the animals for the length of the study (~4 months). Based on these results, MuLuc63 was humanized to generate HuLuc63, which exhibited similar affinity for CS1 when compared to the mouse parent antibody. In two different MM xenograft models, L363 and OPM2, HuLuc63 exhibited significant anti-tumor activity resulting in tumor eradication in a high proportion of animals. To investigate the mechanism of action, two modified versions of HuLuc63 were tested in xenograft models. One version, HuLuc63-Ala,Ala, exhibits a mutation in the Fc region that decreases the ability to interact with the Fc receptor on natural killer (NK) cells. The second version, HuLuc63-LF, exhibits low levels of fucosylation in the Fc region that would result in increased binding to the Fc receptor. Compared to HuLuc63, the LF version exhibited significantly better in vivo anti-tumor activity towards, while the Ala,Ala mutant exhibited no anti-tumor activity. These data indicate that the Fc region of HuLuc63 is critical for its anti-tumor activity, and suggest ADCC as a possible mechanism of action. In vitro, HuLuc63 exhibits substantial ADCC towards L363 and OPM2 cells. The activity was dose-dependent, with increasing cytotoxicity being observed with concentrations ranging from 0.01μg/mL to10 μg/mL. Conclusions: These pre-clinical data support HuLuc63 as a new therapeutic for the treatment of MM and suggest that ADCC is part of the mechanism of action. HuLuc63 will be entering a phase I clinical study for multiple myeloma.

Entinostat, a Novel Histone Deacetylase (HiDAC) Inhibitor Is Active in B-Cell Lymphoma and Enhances the Anti-Tumor Activity of Rituximab, Chemotherapy Agents and Proteasome Inhibitors

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1649-1649
Author(s):  
Sarah Frys ◽  
Matthew J. Barth ◽  
Cory Mavis ◽  
Juan Gu ◽  
John Gibbs ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mechanism Of Action ◽  
Single Agent ◽  
Mechanisms Of Action ◽  
Tail Vein Injection ◽  
Dual Mechanism ◽  
Chemotherapy Agents ◽  
Anti Tumor Activity

Abstract Abstract 1649 Deacetylases (DACs) are enzymes that remove the acetyl groups from target protein lysines leading to regulation of gene transcription and other cellular processes. Entinostat is a novel and potent class I DAC inhibitor undergoing pre-clinical and clinical testing. We previously demonstrated that entinostat was active against a panel of rituximab-sensitive (RSCL) and –resistant cell lines (RRCL); and enhanced the anti-tumor activity of chemotherapy agents. In the current work, we studied the mechanisms-of-action of entinostat and its effect on rituximab activity and proteasome inhibition. Our results indicate that entinostat potentiates both rituximab and proteasome inhibitor activity in NHL cells through a dual caspase dependent and independent mechanism-of-action. Studies were conducted in RSCL, RRCL and in primary tumor cells isolated from patients with B-cell non-Hodgkin's lymphoma (n = 43). For studies with a proteasome inhibitor, cells were exposed to escalating doses of entinostat +/− bortezomib of up to 72 hrs. Studies were repeated with or without a pan-caspase inhibitor (Q-VD-OPh, 5uM). Changes in mitochondrial potential and ATP synthesis were determined by alamar blue reduction and cell titer glo luminescent assays, respectively. Flow cytometric analysis was used to determine changes in cell cycle. Protein lysates from entinostat +/− BTZ exposed cells were evaluated for changes in members of Bcl-2 and cell cycle family proteins. Microarray analysis was performed to discern differences in gene expression between RRCL and RSCL after incubation with entinostat. Separately, we studied the effects of entinostat in vitro and in vivo on rituximab-associated complement-mediated cytotoxicity (CMC) or antibody-dependent cellular cytotoxicity (ADCC). NHL cells were exposed to entinostat or DMSO 0.01% for 48hrs and then labeled with 51Cr. Labeled target cells were then exposed to rituximab or isotype control (10mg/ml) and human serum (25%) (CMC) or PBMCs (Effector:Target ratio, 40:1) (ADCC). For in vivo studies, 6–8 week old SCID mice were inoculated with 1′106 Raji cells via tail vein injection and after a period of 72 hours animals were divided into six cohorts: control, entinostat alone at 5mg/kg/dose, entinostat alone at 20mg/kg/dose alone, rituximab single agent at 10mg/kg/dose, rituximab and entinostat at 5mg/kg/dose and rituximab + entinostat at 20mg/kg/dose. Entinostat was administered by gastric lavage daily on days +3–8 and +11–16, and rituximab was administered via tail vein injection on days +3, +8, +11, and +16. Difference in survival between treatment groups was performed by Kaplan-Meier analysis. Entinostat exhibited dose-dependent activity as a single agent against RSCL, RRCL and patient-derived primary lymphoma cells. In vitro exposure of lymphoma cells to entinostat resulted in an increase in G1 and a decrease in S phase. Synergistic activity was observed by combining entinostat with BTZ but not rituximab in vitro. Microarray data demonstrated that p21 was up-regulated after exposure to entinostat. Additionally, we found an upregulation of ICAM2, down-regulation of E2F2 but no changes in CD20 mRNA. Findings were confirmed at the protein level. Caspase inhibition diminished entinostat anti-tumor activity in RSCL but not in RRCL suggesting that entinostat has a dual mechanism-of-action and can induce cell death by caspase-dependent and independent pathways (i.e. cell cycle arrest). Furthermore, In vivo treatment of SCID mice with high dose entinostat in combination with rituximab led to prolongation of the mean survival (87 days, 72–103 95% C.I. P=0.05) compared to rituximab (67 days, 52–82 95% C.I.) entinostat 20 mg/kg (19 days, 19–20 95% C.I.) alone. Our data suggests that entinostat is active against RSCL and RRCL and potentiates the anti-tumor activity of BTZ or rituximab. In addition, entinostat appears to have a dual mechanism of action that supports its clinical development in rituximab-sensitive or resistant lymphomas. Ongoing studies are aimed to further define the molecular events responsible for entinostat mechanisms-of-action and optimize its spectrum of anti-tumor activity. (Research, in part, supported by a NIH grant R01 CA136907-01A1 awarded to Roswell Park Cancer Institute). Disclosures: No relevant conflicts of interest to declare.

Flavonoids as P-gp Inhibitors: A Systematic Review of SARs

2019 ◽  
Vol 26 (25) ◽  
pp. 4799-4831 ◽  
Author(s):  
Jiahua Cui ◽  
Xiaoyang Liu ◽  
Larry M.C. Chow
Keyword(s):  
Molecular Mechanisms ◽  
Metastatic Cancer ◽  
Drug Candidates ◽  
Chemical Structures ◽  
Transporter Family ◽  
Promising Area ◽  
New Generation ◽  
Nontoxic Inhibitors

P-glycoprotein, also known as ABCB1 in the ABC transporter family, confers the simultaneous resistance of metastatic cancer cells towards various anticancer drugs with different targets and diverse chemical structures. The exploration of safe and specific inhibitors of this pump has always been the pursuit of scientists for the past four decades. Naturally occurring flavonoids as benzopyrone derivatives were recognized as a class of nontoxic inhibitors of P-gp. The recent advent of synthetic flavonoid dimer FD18, as a potent P-gp modulator in reversing multidrug resistance both in vitro and in vivo, specifically targeted the pseudodimeric structure of the drug transporter and represented a new generation of inhibitors with high transporter binding affinity and low toxicity. This review concerned the recent updates on the structure-activity relationships of flavonoids as P-gp inhibitors, the molecular mechanisms of their action and their ability to overcome P-gp-mediated MDR in preclinical studies. It had crucial implications on the discovery of new drug candidates that modulated the efflux of ABC transporters and also provided some clues for the future development in this promising area.

Derivatives of Deoxypodophyllotoxin Induce Apoptosis Through Bcl-2/Bax Proteins Expression

2020 ◽  
Vol 20 ◽  
Author(s):  
Ya-Nan Li ◽  
Ni Ning ◽  
Lei Song ◽  
Yun Geng ◽  
Jun-Ting Fan ◽  
...  
Keyword(s):  
Annexin V ◽  
Mtt Method ◽  
Anthriscus Sylvestris ◽  
Anti Tumor Activity ◽  
Derivatives Of ◽  
Toxicity In Vitro ◽  
Ht 29 ◽  
Mcf 7

Background: Deoxypodophyllotoxin, isolated from theTraditional Chinese Medicine Anthriscus sylvestris, is well-known because of its significant antitumor activity with strong toxicity in vitro and in vivo. Objective: In this article, we synthesized a series of deoxypodophyllotoxin derivatives, and evaluated their antitumor effectiveness.Methods:The anti tumor activity of deoxypodophyllotoxin derivatives was investigated by the MTT method. Apoptosis percentage was measured by flow cytometer analysis using Annexin-V-FITC. Results: The derivatives revealed obvious cytotoxicity in the MTT assay by decreasing the number of late cancer cells. The decrease of Bcl-2/Bax could be observed in MCF-7, HepG2, HT-29 andMG-63 using Annexin V-FITC. The ratio of Bcl-2/Bax in the administration group was decreased, which was determined by the ELISA kit. Conclusion: The derivatives of deoxypodophyllotoxin could induce apoptosis in tumor cell lines by influencing Bcl-2/Bax.

scholarly journals Effect of ethanol and cocaine on [11C]MPC-6827 uptake in SH-SY5Y cells

2021 ◽  
Author(s):  
Naresh Damuka ◽  
Miranda Orr ◽  
Paul W. Czoty ◽  
Jeffrey L. Weiner ◽  
Thomas J. Martin ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Ex Vivo ◽  
Neuroblastoma Cells ◽  
Proper Function ◽  
Brain Functions ◽  
Biodistribution Studies ◽  
Positron Emission ◽  
Vitro Binding

AbstractMicrotubules (MTs) are structural units in the cytoskeleton. In brain cells they are responsible for axonal transport, information processing, and signaling mechanisms. Proper function of these processes is critical for healthy brain functions. Alcohol and substance use disorders (AUD/SUDs) affects the function and organization of MTs in the brain, making them a potential neuroimaging marker to study the resulting impairment of overall neurobehavioral and cognitive processes. Our lab reported the first brain-penetrant MT-tracking Positron Emission Tomography (PET) ligand [11C]MPC-6827 and demonstrated its in vivo utility in rodents and non-human primates. To further explore the in vivo imaging potential of [11C]MPC-6827, we need to investigate its mechanism of action. Here, we report preliminary in vitro binding results in SH-SY5Y neuroblastoma cells exposed to ethanol (EtOH) or cocaine in combination with multiple agents that alter MT stability. EtOH and cocaine treatments increased MT stability and decreased free tubulin monomers. Our initial cell-binding assay demonstrated that [11C]MPC-6827 may have high affinity to free/unbound tubulin units. Consistent with this mechanism of action, we observed lower [11C]MPC-6827 uptake in SH-SY5Y cells after EtOH and cocaine treatments (e.g., fewer free tubulin units). We are currently performing in vivo PET imaging and ex vivo biodistribution studies in rodent and nonhuman primate models of AUD and SUDs and Alzheimer's disease.

scholarly journals Anti-tumor activity of a novel proteasome inhibitor D395 against multiple myeloma and its lower cardiotoxicity compared with carfilzomib

2021 ◽  
Vol 12 (5) ◽  
Author(s):  
Xuxing Shen ◽  
Chao Wu ◽  
Meng Lei ◽  
Qing Yan ◽  
Haoyang Zhang ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Proteasome Inhibitor ◽  
Osteoclast Differentiation ◽  
Dependent Manner ◽  
Serum Enzyme ◽  
Herg Channels ◽  
Anti Tumor Activity ◽  
Dose Dependent

AbstractCarfilzomib, a second-generation proteasome inhibitor, has significantly improved the survival rate of multiple myeloma (MM) patients, but its clinical application is still restricted by drug resistance and cardiotoxicity. Here, we identified a novel proteasome inhibitor, D395, and assessed its efficacy in treating MM as well as its cardiotoxicity at the preclinical level. The activities of purified and intracellular proteasomes were measured to determine the effect of D395 on the proteasome. CCK-8 and flow cytometry experiments were designed to evaluate the effects of D395 on cell growth and apoptosis. The effects of D395 and carfilzomib on serum enzyme activity, echocardiography features, cardiomyocyte morphology, and hERG channels were also compared. In our study, D395 was highly cytotoxic to MM cell lines and primary MM cells but not normal cells, and it was well tolerated in vivo. Similar to carfilzomib, D395 inhibited osteoclast differentiation in a dose-dependent manner. In particular, D395 exhibited lower cardiotoxicity than carfilzomib in all experiments. In conclusion, D395 is a novel irreversible proteasome inhibitor that has remarkable anti-MM activity and mild cardiotoxicity in vitro and in vivo.

scholarly journals Marine-Derived Compounds with Anti-Alzheimer’s Disease Activities

Marine Drugs ◽  
2021 ◽  
Vol 19 (8) ◽  
pp. 410
Author(s):  
Salar Hafez Ghoran ◽  
Anake Kijjoa
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Thinking Skills ◽  
Mechanisms Of Action ◽  
Brain Disorder ◽  
Brain Functioning ◽  
Pharmacologically Active ◽  
Pharmacologically Active Compounds

Alzheimer’s disease (AD) is an irreversible and progressive brain disorder that slowly destroys memory and thinking skills, and, eventually, the ability to perform simple tasks. As the aging population continues to increase exponentially, AD has become a big concern for society. Therefore, neuroprotective compounds are in the spotlight, as a means to tackle this problem. On the other hand, since it is believed—in many cultures—that marine organisms in an individual diet cannot only improve brain functioning, but also slow down its dysfunction, many researchers have focused on identifying neuroprotective compounds from marine resources. The fact that the marine environment is a rich source of structurally unique and biologically and pharmacologically active compounds, with unprecedented mechanisms of action, marine macroorganisms, such as tunicates, corals, sponges, algae, as well as microorganisms, such as marine-derived bacteria, actinomycetes, and fungi, have been the target sources of these compounds. Therefore, this literature review summarizes and categorizes various classes of marine-derived compounds that are able to inhibit key enzymes involved in AD, including acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), β-secretase (BACE-1), and different kinases, together with the related pathways involved in the pathogenesis of AD. The compounds discussed herein are emerging as promising anti-AD activities for further in-depth in vitro and in vivo investigations, to gain more insight of their mechanisms of action and for the development of potential anti-AD drug leads.

scholarly journals Bacteriophage-derived CHAP domain protein, P128, kills Staphylococcus cells by cleaving interpeptide cross-bridge of peptidoglycan

Microbiology ◽  
2014 ◽  
Vol 160 (10) ◽  
pp. 2157-2169 ◽  
Author(s):  
Sudarson Sundarrajan ◽  
Junjappa Raghupatil ◽  
Aradhana Vipra ◽  
Nagalakshmi Narasimhaswamy ◽  
Sanjeev Saravanan ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Mechanism Of Action ◽  
Catalytic Domain ◽  
Antibiotic Sensitivity ◽  
High Sensitivity ◽  
Common Mechanism ◽  
Cross Bridge ◽  
Sensitivity Pattern

P128 is an anti-staphylococcal protein consisting of the Staphylococcus aureus phage-K-derived tail-associated muralytic enzyme (TAME) catalytic domain (Lys16) fused with the cell-wall-binding SH3b domain of lysostaphin. In order to understand the mechanism of action and emergence of resistance to P128, we isolated mutants of Staphylococcus spp., including meticillin-resistant Staphylococcus aureus (MRSA), resistant to P128. In addition to P128, the mutants also showed resistance to Lys16, the catalytic domain of P128. The mutants showed loss of fitness as shown by reduced rate of growth in vitro. One of the mutants tested was found to show reduced virulence in animal models of S. aureus septicaemia suggesting loss of fitness in vivo as well. Analysis of the antibiotic sensitivity pattern showed that the mutants derived from MRSA strains had become sensitive to meticillin and other β-lactams. Interestingly, the mutant cells were resistant to the lytic action of phage K, although the phage was able to adsorb to these cells. Sequencing of the femA gene of three P128-resistant mutants showed either a truncation or deletion in femA, suggesting that improper cross-bridge formation in S. aureus could be causing resistance to P128. Using glutathione S-transferase (GST) fusion peptides as substrates it was found that both P128 and Lys16 were capable of cleaving a pentaglycine sequence, suggesting that P128 might be killing S. aureus by cleaving the pentaglycine cross-bridge of peptidoglycan. Moreover, peptides corresponding to the reported cross-bridge of Staphylococcus haemolyticus (GGSGG, AGSGG), which were not cleaved by lysostaphin, were cleaved efficiently by P128. This was also reflected in high sensitivity of S. haemolyticus to P128. This showed that in spite of sharing a common mechanism of action with lysostaphin, P128 has unique properties, which allow it to act on certain lysostaphin-resistant Staphylococcus strains.

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