Pronounced Antitumor Research Articles

Influence of bioactive sulfated polysaccharide-protein complexes on hepatocarcinogenesis, angiogenesis and immunomodulatory activities

To explore the invivo anticancer, anti-angiogenesis and immunomodulatory efficacies of the bioactive polysaccharide isolated from cold aqueous extract of Jania rubens (JCEM) and Pterocladia capillacea (PCEM) as well as hot aqueous extract of Enteromorpha intestinalis (EHEM) against hepatocellular carcinoma rat model (HCC) and to study their chemical composition. The sugars and amino acids composition of the bioactive polysaccharides of JCEM, PCEM and EHEM were determined using gas liquid chromatography and amino acid analyzer, respectively. These polysaccharide extracts (20mg/kg b.wt. for 5 weeks) were assessed on hepatocarcinogenesis in rats and α-fetoprotein (AFP), carcinoembryonic antigen (CEA), glypican-3 (GPC-3), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) and Ig G levels were evaluated. The GLC analysis of JCEM, PCEM and EHEM polysaccharide revealed the presence of 10, 9 and 10 sugars, in addition the amino acid analyzer enable identification of 16, 15 and 15 amino acids, respectively. These polysaccharide extracts of JCEM, PCEM and EHEM produced significant decrease in serum AFP, CEA, GPC-3, HGF and VEGF compared with untreated HCC group. JCEM, PCEM and EHEM had an immunostimulatory responses by increasing the IgG levels as compared by naïve value (1.23, 1.53 and 1.17 folds), respectively. The bioactive polysaccharides in HCC induced rats improved the humoral immune response. The photomicrographs of liver tissue sections of the groups of HCC treated with polysaccharide extracts of Jania rubens and Enteromorpha intestinalis showed intact histological structure. Moreover, fractions HE1, HE4, HE7 obtained from polysaccharide of EHEM showed moderate cytotoxic activity against HepG2 invitro with IC50 73.1, 42.6, 76.2μg/mL. However, fractions of PCEM and JCEM show no or weak cytotoxicity against HepG2 invitro where the cytotoxic activity of their crude polysaccharide extract proved synergetic effect. The pronounced antitumor activity of sulfated polysaccharide-protein complexes of JCEM and EHEM is due to direct cytotoxic activity, anti-hepatocarcinogenesis, and anti-angiogenesis. In addition, JCEM, PCEM and EHEM had an immunostimulatory response and improved the humoral immune response in HCC induced rats.

Utilization of Structure-Based Design to Identify Novel, Irreversible Inhibitors of EGFR Harboring the T790M Mutation.

A novel series of covalent inhibitors of EGFR (epidermal growth factor receptor) kinase was discovered through a combination of subset screening and structure-based design. These compounds preferentially inhibit mutant forms of EGFR (activating mutant and T790M mutant) over wild-type EGFR in cellular assays measuring EGFR autophosphorylation and proliferation, suggesting an improved therapeutic index in non-small cell lung cancer patients would be achievable relative to established EGFR inhibitors. We describe our design approaches, resulting in the identification of the lead compound 5, and our efforts to develop an understanding of the structure-activity relationships within this series. In addition, strategies to overcome challenges around metabolic stability and aqueous solubility are discussed. Despite limitations in its physical properties, 5 is orally bioavailable in mice and demonstrates pronounced antitumor activity in in vivo models of mutant EGFR-driven cancers.

The kinesin Eg5 inhibitor K858 induces apoptosis but also survivin-related chemoresistance in breast cancer cells.

Inhibitors of kinesin spindle protein Eg5 are characterized by pronounced antitumor activity. Our group has recently synthesized and screened a library of 1,3,4-thiadiazoline analogues with the pharmacophoric structure of K858, an Eg5 inhibitor. We herein report the effects of K858 on four different breast cancer cell lines: MCF7 (luminal A), BT474 (luminal B), SKBR3 (HER2 like) and MDA-MB231 (basal like). We demonstrated that K858 displayed anti-proliferative activity on every analyzed breast cancer cell line by inducing apoptosis. However, at the same time, we showed that K858 up-regulated survivin, an anti-apoptotic molecule. We then performed a negative regulation of survivin expression, with the utilization of wortmannin, an AKT inhibitor, and obtained a significant increase of K858-dependent apoptosis. These data demonstrate that K858 is a potent inhibitor of replication and induces apoptosis in breast tumor cells, independently from the tumor phenotype. This anti-proliferative response of tumor cells to K858 can be limited by the contemporaneous over-expression of survivin; consequently, the reduction of survivin levels, obtained with AKT inhibitors, can sensitize tumor cells to K858-induced apoptosis.

Antitumor and Antimetastatic Effect of Small Immunostimulatory RNA against B16 Melanoma in Mice

Small interfering RNAs, depending on their structure, delivery system and sequence, can stimulate innate and adaptive immunity. The aim of this study was to investigate the antitumor and antimetastatic effects of immunostimulatory 19-bp dsRNA with 3’- trinucleotide overhangs (isRNA) on melanoma B16 in C57Bl/6 mice. Recently developed novel cationic liposomes 2X3-DOPE were used for the in vivo delivery of isRNA. Administration of isRNA/2X3-DOPE complexes significantly inhibits melanoma tumor growth and metastasis. Histopathological analysis of spleen cross sections showed hyperplasia of the lymphoid white pulp and formation of large germinal centers after isRNA/2X3-DOPE administration, indicating activation of the immune system. The treatment of melanoma-bearing mice with isRNA/2X3-DOPE decreases the destructive changes in the liver parenchyma. Thus, the developed isRNA displays pronounced immunostimulatory, antitumor and antimetastatic properties against melanoma B16 and may be considered a potential agent in the immunotherapy of melanoma.

Antitumor Activity of Rat Mesenchymal Stem Cells during Direct or Indirect Co-Culturing with C6 Glioma Cells.

The tumor-suppressive effect of rat mesenchymal stem cells against low-differentiated rat C6 glioma cells during their direct and indirect co-culturing and during culturing of C6 glioma cells in the medium conditioned by mesenchymal stem cells was studied in an in vitro experiment. The most pronounced antitumor activity of mesenchymal stem cells was observed during direct co-culturing with C6 glioma cells. The number of live C6 glioma cells during indirect co-culturing and during culturing in conditioned medium was slightly higher than during direct co-culturing, but significantly differed from the control (C6 glioma cells cultured in medium conditioned by C6 glioma cells). The cytotoxic effect of medium conditioned by mesenchymal stem cells was not related to medium depletion by glioma cells during their growth. The medium conditioned by other "non-stem" cells (rat astrocytes and fibroblasts) produced no tumor-suppressive effect. Rat mesenchymal stem cells, similar to rat C6 glioma cells express connexin 43, the main astroglial gap junction protein. During co-culturing, mesenchymal stem cells and glioma C6 cells formed functionally active gap junctions. Gap junction blockade with connexon inhibitor carbenoxolone attenuated the antitumor effect observed during direct co-culturing of C6 glioma cells and mesenchymal stem cells to the level produced by conditioned medium. Cell-cell signaling mediated by gap junctions can be a mechanism of the tumor-suppressive effect of mesenchymal stem cells against C6 glioma cells. This phenomenon can be used for the development of new methods of cell therapy for high-grade malignant gliomas.

Ameliorated or Acquired Cytostatic/Cytotoxic Properties of Nucleosides by Lipophilization.

A series of nucleolipids, containing one of the β-D-ribonucleosides 5-fluorouridine, 6-azauridine, uridine, or 5-methyluridine were lipophilized, either at the O-2',3'-position and/or at N(3) of the nucleobase with a large variety of hydrophobic residues. The resulting nucleolipids as well as the parent nucleosides and the lipid precursors were investigated in vitro with respect to their antitumor activity towards i) ten human tumor cell lines from the NCI 60 panel and ii) partly against three further tumor cell lines, namely a) human astrocytoma/oligodendro glioma GOs-3, b) rat malignantneuroectodermal BT4Ca, and c) differentiated human THP-1 macrophages. Inspection of the doseresponse curves allows two main conclusions concerning lipid determinants lending the corresponding nucleoside an ameliorated or an acquired antitumor activity: i) introduction of either a symmetrical O-2',3'-nonadecylidene ketal group or introduction of an O-2',3'-ethyl levulinate moiety plus an N(3)-farnesyl group leads often to nucleolipids with significant cytostatic/cytotoxic properties; ii) for the two canonical and non-toxic nucleosides uridine and 5-methyluridine, the condensation with also non-toxic lipids gives nucleolipids with a pronounced antitumor activity.

P17: Antitumor activity of allogeneic bone marrow cells immobilized in porous-permeable TiNi-based alloy scaffold

The most effective method in treatment of inoperable cancer is currently miniallogeneic transplantation. This type of treatment focuses on reaction of “graft-versus-tumor”. According to preliminary data, such treatment leads to long-term remission in patients with metastatic cancer, who did not respond to previous therapy. Anti-tumor immune response after transplant may be extended or enhanced by additional infusion of donor lymphocytes. Research has shown that introduction of donor lymphocytes achieves complete remission of the tumor, even in case of relapse after allogeneic transplantation from the same donor, but these effects are unstable and not so long because of rapid elimination of donor lymphocytes [1] . The main problem is the preservation of cell transplantation viability and functional activity of the cells in patient’s body, and protecting them from recipient’s immune system. In recent years, most suitable for this purpose are the three-dimensional porous biomaterials (3D-scaffold). Specific pore space does not allow immunity effectors quickly destroy the cells in scaffold [2] , [3] . Research Institute of medical materials and implants with shape memory at the Tomsk State University created a porous-permeable incubators (scaffold) of TiNi-based shape memory alloy (TiNi). The material has unique properties: permeable porous structure by open interconnected pores, characterized by high degree of wettability with tissue media and nanoporous inner surface of the pore walls, exhibits high adhesion to various cell types, so all mentioned meet requirements of the bio-chemical and bio-mechanical compatibility. Porous TiNi-based scaffolds allow continually to keep the functionality cells and prolong their action [4] , [5] . The purpose of this study was to investigate possibility of modulation of antitumor response in allogeneic bone marrow transplantation in porous-permeable incubator of TiNi. Results Intraperitoneal injection of allogeneic bone marrow (BM) reduces metastasis by 30% and has easy 10%-antitumor effect. At the same time, the implantation of bone marrow cells on incubator of TiNi (BM + TiNi) leads to more pronounced antitumor (25%) and significant antimetastatic effects (45%). Life span of animals with tumors and implanted bone marrow cells on incubator TiNi is increased by 60% Since bone marrow cells do not have direct antiproliferative effect on tumor target cells in vitro, it is assumed that one of the mechanisms effecting the bone marrow transplantation on neoplastic process is the stimulation of endogenous effectors of antitumor immunity. The study of morphological parameters immunocompetent organs showed that administration of allogeneic bone marrow cells can reduce thymic regression, decrease splenomegaly at animals with transplanted tumors. Conclusion Allogeneic transplantation of bone marrow cells on porous incubator was shown to prolong and enhance antitumor and antimetastatic action compared to injecting the cells. This effect is directly due to the stimulation of antitumor immunity, that is described by the study of immunity factors. The results show perspectives of porous TiNi-based scaffolds in complex treatment of neoplastic diseases.

Synthesis, Transformations, and Study of Some Biological Properties of New 3,4,5-Substituted 1,2,4-Triazoles

A series of new 3,4,5-substituted 1,2,4-triazoles were synthesized. Their SH-alkylation by various alkylating compounds and aminomethylation leading to the formation of Mannich bases were studied. The influence of the synthesized compounds on the level of DNA methylation and their antitumor and antibacterial properties were investigated. Several compounds with pronounced demethylation and weak antitumor and antibacterial activities were identified. Correlations among the investigated biological properties were not found.

Impact of kinesin Eg5 inhibition by 3,4-dihydropyrimidin-2(1H)-one derivatives on various breast cancer cell features.

BackgroundBreast cancer is a complex heterogeneous disease and is one of the leading causes of death among women. In addressing the need for treatments of this life-threatening illness, we studied 3,4-dihydropyrimidin-2(1H)-one (or thione) derivatives (DHPMs), a class of inhibitor molecules of the Eg5 motor spindle protein that shows pronounced antitumor activity against several cancer cell lines.MethodsAn in vitro screening was performed for identification of DHPMs with potent antitumor effects on MCF-7 and MDA-MB-231 cells and the selected DHPMs were evaluated for their inhibitory activity on Eg5 both in silico, using Molecular dynamics, and in vitro Eg5 inhibition assays. Analysis of cell death induction, proliferation, cell cycle and cancer stem cells (CSC) profile were performed by flow cytometry to assess the influence of the selected DPHMs on these important tumor features. Finally, the effects of DHPM treatment on tube formation were evaluated in vitro using HUVEC cells, and in vivo using a model on chorioallantoic membrane (CAM) of fertilized eggs.ResultsWe identified five DHPMs with pronounced inhibitory activity on Eg5 motor protein interfering with the proper mitotic spindle assembly during cell division. These compounds impair the correct conclusion of cell cycle of the breast cancer cells and showed to be selective for tumor cells. Moreover, DHPMs modulate the CD44+/CD24− phenotype leading to a decrease in the CSC population in MDA-MB-231 cells, an important effect since CSC are resistant to many conventional cancer therapies and play a pivotal role in tumor initiation and maintenance. This observation was confirmed by the results which demonstrated that DHPM treated cells had impaired proliferation and were unable to sustain angiogenesis events. Finally, the DHMP treated cells were induced to apoptosis, which is one of the most pursued goals in drug development.ConclusionsThe results of our study strongly suggest that DHPMs inhibit important tumorigenic features of breast cancer cells leading them to death by apoptosis. These findings firmly point to DHPM molecular architecture as a promising alternative against breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1274-1) contains supplementary material, which is available to authorized users.

New synthesis of syn-stereodiad building block for polyketides. Formal synthesis of arenamides A and C

An efficient procedure has been developed for the transformation of (7S)-7-(3-bromoprop-1-en-2-yl)-5,5-dimethyl-4,6-dioxaspiro[2.5]octane [available from diethyl (S)-malate] into methyl 2-[(4S)-2,2-dimethyl-5-methylidene-1,3-dioxan-4-yl]acetate, and conditions for diastereoselective reduction of the double C=C bond in the latter have been optimized. The reduction product has been converted into (3S,4S)-3-[tert-butyl(dimethyl)siloxy]-4-methyldecanoic acid which is a building block for the synthesis of arenamides A and C, natural compounds possessing pronounced antitumor activity and efficiently inhibiting nitrogen(II) oxide and prostaglandin E2 (PGE2).

Combined influence of teichoic acids from Staphylococcus aureus and heterometallik Cu/Cd ethylenediamine complex on peritoneal macrophages and tumor cells

We investigated the effects of teichoic acid (TA) from Staphylococcus aureus Wood 46 on tumor growth and metastasis of the experimental Lewis lung carcinoma (LLC) in mice. Intranasal administration of TA alone aggravated both tumor growth and metastasis, whereas combined administration of TA with a synthetic bimetallic (copper : cadmium) ethylene diamine complex PO244 resulted in pronounced antitumor and antimetastatic effects. The group of animals subjected to the combined treatment with TA and PO244 manifested the highest degree of lymphocyte infiltration into the tumor tissue, compared to the control group and those exposed to TA or PO244 alone. Moreover, the combined treatment negatively affected the adhesive properties of peritoneal macrophages in the LLC bearing mice. Co-cultivation of the isolated macrophages with primary LLC cultures revealed significant (p < 0.05) cytotoxic and cytostatic effects, detected as an increased level of apoptosis and a reduced fraction of replicating cells.

Signs of Cell-Cell Interactions in Sarcoma 45 Tissue Under Conditions of Antitumor Effect Caused by Injection of Magnetite Nanoparticles

Changes in transplanted sarcoma 45 tissue in outbred albino rats with tumor regression under the effect of magnetite nanoparticles (magnetic fluid) were studied by light and electron microscopy. The ultrastructure and cell death types in regressing tumors and signs of cell-cell interactions with participation of macrophages, lymphocytes, neutrophils, and degranulating mast cells were described. Some possible mechanisms of a pronounced antitumor activity of magnetite nanoparticles were discussed.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Galactose-Decorated Reduction-Sensitive Degradable Chimaeric Polymersomes as a Multifunctional Nanocarrier To Efficiently Chaperone Apoptotic Proteins into Hepatoma Cells

Hepatoma-targeting reduction-sensitive chimaeric biodegradable polymersomes were designed and developed based on galactose-poly(ethylene glycol)-poly(ε-caprolactone) (Gal-PEG-PCL), PEG-PCL-poly(2-(diethylamino)ethyl methacrylate) (PEG-PCL-PDEA, asymmetric), and PEG-SS-PCL for facile loading and triggered intracellular delivery of proteins. The chimaeric polymersomes formed from PEG-PCL-PDEA and PEG-SS-PCL had a monodisperse distribution with average sizes ranging from 95.5 to 199.2 nm depending on PEG-SS-PCL contents. Notably, these polymersomes displayed decent loading of bovine serum albumin (BSA), ovalbumin (OVA), and cytochrome C (CC) proteins likely due to presence of electrostatic and hydrogen bonding interactions between proteins and PDEA block located in the interior of polymersomes. The in vitro release studies showed that protein release was largely accelerated under a reductive condition containing 10 mM dithiothreitol (DTT). For example, ca. 77.2 and 22.1% of FITC-BSA were released from CP(SS50) (chimaeric polymersomes containing 50 wt % PEG-SS-PCL) at 37 °C in 12 h in the presence and absence of 10 mM DTT, respectively. Confocal microscopy showed that FITC-CC-loaded Gal-decorated CP(SS40) could efficiently deliver and release FITC-CC into HepG2 cells following 24 h treatment, in contrast to little or negligible fluorescence detected in HepG2 cells treated with FITC-CC-loaded nontargeting polymersomes or free CC. MTT assays revealed that CC-loaded Gal-decorated CP(SS40) exhibited apparent targetability and pronounced antitumor activity to HepG2 cells, in which cell viabilities decreased from 81.9, 60.6, 49.5, 42.2 to 31.5% with increasing Gal-PEG-PCL contents from 0, 10, 20, 30 to 40 wt %. Most remarkably, granzyme B-loaded Gal-decorated chimaeric polymersomes effectively caused apoptosis of HepG2 cells with a markedly low half-maximal inhibitory concentration (IC(50)) of 2.7 nM. These reduction-responsive chimaeric biodegradable polymersomes offer a multifunctional platform for efficient intracellular protein delivery.

Вплив похідних дигідропіролу та малеїміду на стан печінки і товстої кишки щурів у нормі та в умовах індукованого диме

No liver and colon alterations in rats, caused by cytostatic compounds 5-amino-4-(1,3-benzothyazol-2-yl)-1-(3-methoxyphenyl)-1,2-dihydro-3H-pyrrol-3-one (D1) and 1-(4-Cl-benzyl)-3-Cl-4-(CF3-phenylamino)-1H-pyrrol-2,5-dione (MI-1) when administered over a long time were found, as evidenced by the histopathological data and the data of activity of transaminases, alkaline phosphatase and lactate dehydrogenase in the blood serum. D1 and MI-1 in vivo decrease the total area of DMH-induced colon tumors in rats by 46-60%. Furthermore, D1 and MI-1 partially protect the liver and colon mucosa from toxic effects caused by 1,2-dimethylhydrazine (DMH) reducing DNA oxidative modifications, as evidenced by urine 8-hydroxydeoxyguanosine level. The effects of both compounds are similar, but MI-1 is less toxic for the liver and colon of intact animals possessing more pronounced antitumor activity and protective properties in the setting of chemically induced carcinogenesis.

Radiosensitizing effect of intratumoral interleukin-12 gene electrotransfer in murine sarcoma

BackgroundInterleukin-12 (IL-12) based radiosensitization is an effective way of tumor treatment. Local cytokine production, without systemic shedding, might provide clinical benefit in radiation treatment of sarcomas. Therefore, the aim was to stimulate intratumoral IL-12 production by gene electrotransfer of plasmid coding for mouse IL-12 (mIL-12) into the tumors, in order to explore its radiosensitizing effect after single or multiple intratumoral gene electrotransfer.MethodsSolid SA-1 fibrosarcoma tumors, on the back of A/J mice, were treated intratumorally by mIL-12 gene electrotransfer and 24 h later irradiated with a single dose. Treatment effectiveness was measured by tumor growth delay and local tumor control assay (TCD50 assay). With respect to therapeutic index, skin reaction in the radiation field was scored. The tumor and serum concentrations of cytokines mIL-12 and mouse interferon γ (mIFNγ) were measured. Besides single, also multiple intratumoral mIL-12 gene electrotransfer before and after tumor irradiation was evaluated.ResultsSingle intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral but not serum mIL-12 and mIFNγ concentrations, and had good antitumor (7.1% tumor cures) and radiosensitizing effect (21.4% tumor cures). Combined treatment resulted in the radiation dose-modifying factor of 2.16. Multiple mIL-12 gene electrotransfer had an even more pronounced antitumor (50% tumor cures) and radiosensitizing (86.7% tumor cures) effect.ConclusionsSingle or multiple intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral mIL-12 and mIFNγ cytokine level, and may provide an efficient treatment modality for soft tissue sarcoma as single or adjuvant therapy to tumor irradiation.

QSAR Modeling on Benzo[c]phenanthridine Analogues as Topoisomerase I Inhibitors and Anti-cancer Agents

Benzo[c]phenanthridine (BCP) derivatives were identified as topoisomerase I (TOP-I) targeting agents with pronounced antitumor activity. In this study, hologram-QSAR, 2D-QSAR and 3D-QSAR models were developed for BCPs on topoisomerase I inbibitory activity and cytotoxicity against seven tumor cell lines including RPMI8402, CPT-K5, P388, CPT45, KB3-1, KBV-1and KBH5.0. The hologram, 2D, and 3D-QSAR models were obtained with the square of correlation coefficient R2 = 0.58 − 0.77, the square of the crossvalidation coefficient q2 = 0.41 − 0.60 as well as the external set’s square of predictive correlation coefficient r2 = 0.51 − 0.80. Moreover, the assessment method based on reliability test with confidence level of 95% was used to validate the predictive power of QSAR models and to prevent over-fitting phenomenon of classical QSAR models. Our QSAR model could be applied to design new analogues of BCPs with higher antitumor and topoisomerase I inhibitory activity.

A Support Vector Machine Classification Model for Benzo[c]phenathridine Analogues with Topoisomerase-I Inhibitory Activity

Benzo[c]phenanthridine (BCP) derivatives were identified as topoisomerase I (TOP-I) targeting agents with pronounced antitumor activity. In this study, a support vector machine model was performed on a series of 73 analogues to classify BCP derivatives according to TOP-I inhibitory activity. The best SVM model with total accuracy of 93% for training set was achieved using a set of 7 descriptors identified from a large set via a random forest algorithm. Overall accuracy of up to 87% and a Matthews coefficient correlation (MCC) of 0.71 were obtained after this SVM classifier was validated internally by a test set of 15 compounds. For two external test sets, 89% and 80% BCP compounds, respectively, were correctly predicted. The results indicated that our SVM model could be used as the filter for designing new BCP compounds with higher TOP-I inhibitory activity.

Abstract 3856: Dimerized single chain TRAIL-receptor agonists do not depend on Fc-gamma-receptor cross-linking for anti-tumor efficacy in vivo

Abstract APG350 is a TRAIL-receptor (TRAIL-R) agonist comprising two single-chain TRAIL-R binding domains (scTRAIL-RBD) that are dimerized via the Fc-part of a human IgG1-mutein thereby creating six receptor binding sites per molecule. This improved ability to form clusters on target cells composed of six TRAIL-Rs each, distinguishes APG350 from current clinical development candidates. In vitro, comparison of APG350 with recombinant APO2L/TRAIL and a TRAIL-R2 specific agonistic antibody revealed superior apoptosis induction for APG350 on primary and established human tumor cell-lines. Treatment of mice bearing Colo205 xenograft tumors with APG350, APO2L/TRAIL or an agonistic TRAIL-R2 specific antibody showed superior anti-tumor efficacy for APG350. Pronounced anti tumor efficacy was also shown on colon cancer stem cell (CSC) derived xenografts and successful APG350 re-treatment of relapsed CSC derived tumors demonstrated that tumors did not develop drug resistance. For most agonistic TRAIL-R antibodies effective apoptosis induction is achieved only upon additional cross-linking. SEC-based fractionation of a TRAIL-R2 specific agonistic antibody indicates a small amount of multimerized antibody that showed efficient apoptosis induction in vitro. However, the respective monomeric antibody showed poor apoptosis induction in vitro that could be enhanced upon cross-linking. In contrast apoptosis induction by APG350 was only marginally enhanced by cross-linking. Although monomeric agonistic TRAIL-R antibodies are poor apoptosis inducers in vitro, they show efficient apoptosis induction on xenograft tumors in vivo. A likely explanation for this difference is given by a recent publication showing that anti-tumor efficacy of an agonistic TRAIL-R2 specific antibody (Drozitumab) depends on cross-linking by Fcα-receptors (FcαR) in vivo. These data suggest that FcαR cross-linking might be a common requirement for the anti-tumor efficacy of agonistic TRAIL-R antibodies. To exclude that in vivo efficacy of APG350 depends on cross-linking by FcαRs we designed APG350-muteins with strongly reduced (APG808) or lacking FcαR binding (APG780). Side by side comparison of APG808, APG780 and APG350 in mice bearing Colo205-derived xenograft tumors showed identical anti-tumor efficacy for all respective proteins. Given that APG780 cannot bind to FcαRs these results suggest that the anti-tumor efficacy of APG808, APG780 and APG350 is solely based on the unique construction principle of the dimerized scTRAIL-RBD. APG350 induces superior clustering of TRAIL-Rs that in contrast to agonistic TRAIL-R antibodies does not require cross-linking via FcαRs for its potent anti-tumor efficacy. APG350 based dimerized scTRAIL-RBD formats may therefore have the capacity to bridge the current gap seen between preclinical and clinical efficacy for agonistic TRAIL-R specific antibodies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3856. doi:1538-7445.AM2012-3856

Computational QSAR models with high-dimensional descriptor selection improve antitumor activity design of ARC-111 analogues

ARC-111 has potent topoisomerase I-targeting activity and pronounced antitumor activity. To design ARC-111 analogues with improved efficiency, we performed analyses on the quantitative structure–activity relationship of 22 ARC-111 analogues assessed in P388 tumor cells. First, the support vector regression (SVR) models were constructed and optimized based on literature descriptors (the low-dimensional descriptor space) and the worst descriptor elimination multi-round (WDEM) method. The optimized SVR model had greater generalization ability than multiple linear regression (MLR) and stepwise linear regression (SLR) in the independence test, which indicated that our nonlinear WDEM method could remove redundant descriptors more effectively, and our optimized SVR was a more powerful modeling technique. Second, to identify more accessible and effective descriptors, our modeling descriptors with clear meanings were selected from a large number of descriptors calculated by the software PCLIENT. Through the high-dimensional descriptor selection nonlinear method and the WDEM method, seven independent variable combinations with tens of descriptors were selected out of 2,923 descriptors. The seven corresponding SVR models performed better in the independent test, compared to MLR and SLR. The evaluation measures supported the excellent predictive power of the new models. According to the interpretability analysis of the SVR model, the regression significance of the model and the importance of single indicator were evaluated based on F tests. Our study offers some useful theories for understanding the function mechanism and finds parameters for designing ARC-111 analogues with enhanced antitumor activity.