Cytotoxicity In Human Cell Lines Research Articles

Characterization of silver nanoparticles (AgNPs) synthesized using polyphenolic compounds from Phyllanthus emblica L. and their impact on cytotoxicity in human cell lines

The Phyllanthus emblica L. highly medicinal value used for jaundice, anticancer, antioxidant, antiviral, antimicrobial etc., activities so for that current research explored the application of nanotechnology in developing anticancer strategies through the synthesis of silver nanoparticles (AgNPs) using natural extracts from leaves. Various characterization techniques were employed to assess the anticancer properties against the human MCF-7 Breast Cancer Cell Line. This study in UV‒visible spectroscopy AgNPs detected at 436 nm, FT-IR analysis indicated the presence of specific functional groups with high peak intensity at 3105 cm−1. In SEM measurements revealed synthesized AgNPs at 25.4 nm, TEM exposed perfectly round particles with a lattice spacing of 0.295 nm, and XRD analysis revealed reflections at (111), (200), (220), and (310) with corresponding 2θ values of 39.1°, 46.1°, 68.7°, and 79.2°, respectively, along with the observation of (311). EDX analysis confirmed the composite nature of quartz with AgNPs at a 50:50 ratio. Atomic force microscopy (AFM) images of AgNPs 30 nm in size. Furthermore, breast cancer one of the major disease, targeted application of our study focused anticancer activity against MCF-7 breast cancer cell line, observed that plant extract exhibits 92% cancer cell death at 500 µg/ml, showed potential anticancer activity against breast cancer cells. In flowcytometry cancer cells phase distribution was observed at AgNPs (100 to 200 µg/ml). Prolonged exposure to the extract led to cell death and arrested the apoptotic cell death cycle after 24 hours. Research has also evaluated the potential of nanoparticles to inhibit cancer progression, revealing promising prospects for enhancing anticancer therapies. During the treatment against cancer cells observed cell deaths, concluded that green, nanotechnology potential tool for modern world.

Discovery of Lactomodulin, a Unique Microbiome-Derived Peptide That Exhibits Dual Anti-Inflammatory and Antimicrobial Activity against Multidrug-Resistant Pathogens.

The human body is a superorganism that harbors trillions of microbes, most of which inhabit the gut. To colonize our bodies, these microbes have evolved strategies to regulate the immune system and maintain intestinal immune homeostasis by secreting chemical mediators. There is much interest in deciphering these chemicals and furthering their development as novel therapeutics. In this work, we present a combined experimental and computational approach to identifying functional immunomodulatory molecules from the gut microbiome. Based on this approach, we report the discovery of lactomodulin, a unique peptide from Lactobacillus rhamnosus that exhibits dual anti-inflammatory and antibiotic activities and minimal cytotoxicity in human cell lines. Lactomodulin reduces several secreted proinflammatory cytokines, including IL-8, IL-6, IL-1β, and TNF-α. As an antibiotic, lactomodulin is effective against a range of human pathogens, and is most potent against antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). The multifunctional activity of lactomodulin affirms that the microbiome encodes evolved functional molecules with promising therapeutic potential.

In Vitro Biological Activity of Natural Products from the Endophytic Fungus Paraboeremia selaginellae against Toxoplasma gondii.

Toxoplasma gondii is an apicomplexan pathogen able to infect a wide range of warm-blooded animals, including humans, leading to toxoplasmosis. Current treatments for toxoplasmosis are associated with severe side-effects and a lack efficacy to eradicate chronic infection. Thus, there is an urgent need for developing novel, highly efficient agents against toxoplasmosis with low toxicity. For decades, natural products have been a useful source of novel bioactive compounds for the treatment of infectious pathogens. In the present study, we isolated eight natural products from the crude extract of the endophytic fungus Paraboeremia selaginellae obtained from the leaves of the plant Philodendron monstera. The natural products were tested for inhibiting Toxoplasma gondii proliferation, and their cytotoxicity was evaluated in different human cell lines. Six natural products showed antitoxoplasma activity with low or no cytotoxicity in human cell lines. Together, these findings indicate that biphenyl ethers, bioxanthracenes, and 5S,6S-phomalactone from P. selaginellae are potential candidates for novel anti-toxoplasma drugs.

Cytotoxicity of Peruvian propolis and Psidium guajava on human gingival fibroblasts, PBMCs and HeLa cells

It is indisputable that every day it is demonstrated that natural products present diverse therapeutic benefits, which has boosted their incorporation within various products for clinical use. However, this must be accompanied by knowledge of their effect on cell lines to ensure their use is safe. The objective of this study was to evaluate the cytotoxic effect of two ethanolic extracts based on Peruvian natural products, on three human cell lines. Cervical cancer cell lines (HeLa), human gingival fibroblasts (HGF-1 - ATCC CRL-2014) (HGF-1) and peripheral blood mononuclear cells (PBMCs) were cultured and subsequently treated with preparations of ethanolic extracts of propolis (EEP) and Psidium guajava (EEG) from a concentration of 50 mg/mL to 0.024 mg/mL, by the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazole bromide reduction assay. At a concentration of 0.24 mg/mL EEG, viability of 99.7±1.24%, 99.8±2.2% and 99.7±2.7% was observed in HeLa, HGF-1 and PBMCs, respectively; >90% cell viability values were observed with EPP at 0.024 mg/mL, with HGF-1 showing the highest viability (96.9±1.15%). A dose-dependent effect was observed for both extracts with a decrease in cell viability as concentrations increased (up to 50 mg/mL). EEP and EEG extracts at low concentrations do not show cytotoxicity in human cell lines, these findings are an advance in the preclinical evaluation on their safety and open a continuity to further studies for their potential applications in dentistry and medicine.

Cytotoxicity of Peruvian propolis and Psidium guajava on human gingival fibroblasts, PBMCs and HeLa cells

It is indisputable that every day it is demonstrated that natural products present diverse therapeutic benefits, which has boosted their incorporation within various products for clinical use. However, this must be accompanied by knowledge of their effect on cell lines to ensure their use is safe. The objective of this study was to evaluate the cytotoxic effect of two ethanolic extracts based on Peruvian natural products, on three human cell lines. Cervical cancer cell lines (HeLa), human gingival fibroblasts (HGF-1 - ATCC CRL-2014) (HGF-1) and peripheral blood mononuclear cells (PBMCs) were cultured and subsequently treated with preparations of ethanolic extracts of propolis (EEP) and Psidium guajava (EEG) from a concentration of 50 mg/mL to 0.024 mg/mL, by the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazole bromide reduction assay. At a concentration of 0.24 mg/mL EEG, viability of 99.7±1.24%, 99.8±2.2% and 99.7±2.7% was observed in HeLa, HGF-1 and PBMCs, respectively; >90% cell viability values were observed with EPP at 0.024 mg/mL, with HGF-1 showing the highest viability (96.9±1.15%). A dose-dependent effect was observed for both extracts with a decrease in cell viability as concentrations increased (up to 50 mg/mL). EEP and EEG extracts at low concentrations do not show cytotoxicity in human cell lines, these findings are an advance in the preclinical evaluation on their safety and open a continuity to further studies for their potential applications in dentistry and medicine.

Cytotoxicity of Peruvian propolis and Psidium guajava on human gingival fibroblasts, PBMCs and HeLa cells.

It is indisputable that every day it is demonstrated that natural products present diverse therapeutic benefits, which has boosted their incorporation within various products for clinical use. However, this must be accompanied by knowledge of their effect on cell lines to ensure their use is safe. The objective of this study was to evaluate the cytotoxic effect of two ethanolic extracts based on Peruvian natural products, on three human cell lines. Cervical cancer cell lines (HeLa), human gingival fibroblasts (HGF-1 - ATCC CRL-2014) (HGF-1) and peripheral blood mononuclear cells (PBMCs) were cultured and subsequently treated with preparations of ethanolic extracts of propolis (EEP) and Psidium guajava (EEG) from a concentration of 50 mg/mL to 0.024 mg/mL, by the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazole bromide reduction assay. At a concentration of 0.24 mg/mL EEG, viability of 99.7±1.24%, 99.8±2.2% and 99.7±2.7% was observed in HeLa, HGF-1 and PBMCs, respectively; >90% cell viability values were observed with EPP at 0.024 mg/mL, with HGF-1 showing the highest viability (96.9±1.15%). A dose-dependent effect was observed for both extracts with a decrease in cell viability as concentrations increased (up to 50 mg/mL). EEP and EEG extracts at low concentrations do not show cytotoxicity in human cell lines, these findings are an advance in the preclinical evaluation on their safety and open a continuity to further studies for their potential applications in dentistry and medicine.

Procainamide-SAHA Fused Inhibitors of hHDAC6 Tackle Multidrug-Resistant Malaria Parasites.

Epigenetic post-translational modifications are essential for human malaria parasite survival and progression through its life cycle. Here, we present new functionalized suberoylanilide hydroxamic acid (SAHA) derivatives that chemically combine the pan-histone deacetylase inhibitor SAHA with the DNA methyltransferase inhibitor procainamide. A three- or four-step chemical synthesis was designed starting from cheap raw materials. Compared to the single drugs, the combined molecules showed a superior activity in Plasmodium and a potent inhibition against human HDAC6, exerting no cytotoxicity in human cell lines. These new compounds are fully active in multidrug-resistant Plasmodium falciparum Cambodian isolates. They target transmission of the parasite by inducing irreversible morphological changes in gametocytes and inhibiting exflagellation. The compounds are slow-acting and have an additive antimalarial effect in combination with fast-acting epidrugs and dihydroartemisinin. The lead compound decreases parasitemia in mice in a severe malaria model. Taken together, this novel fused molecule offers an affordable alternative to current failing antimalarial therapy.

Clonal Evolution Mechanisms and Collateral Sensitivity to Impdh Inhibitor Therapy in Relapsed Lymphoblastic Leukemia

Improved support and intensified chemotherapy regimens have increased the overall survival rates of newly diagnosed pediatric ALL to over 80%. However the outcomes of patients with relapsed or refractory ALL remain poor, with cure rates of about only 40%. Thus, leukemia relapse and chemotherapy resistance are now the most prominent challenges in the treatment of ALL. Leukemia-initiating cells capable of self-renewal, protective microenvironment safe-haven niches and clonal evolution with acquisition of secondary genetic alterations driving chemotherapy resistance have all been implicated as drivers of ALL disease progression and relapse. In this context, heterozygous activating mutations in the NT5C2 nucleotidase gene are present in about 20% of relapsed pediatric T-cell ALL (T-ALL) cases and 3-10% of relapsed B-precursor ALLs. Yet, the mechanisms involved in NT5C2 mutation-driven clonal evolution during leukemia initiation, disease progression and relapse remain unknown. Using a conditional inducible leukemia model, we demonstrate that expression of Nt5c2 p.R367Q, a highly prevalent relapsed-ALL NT5C2 mutation, induces resistance to chemotherapy with 6-MP at the cost of impaired leukemia cell growth and leukemia-initiating cell activity. Consistently ultra-deep sequencing with molecular barcodes, allele specific PCR and droplet PCR analyses showed that NT5C2 mutations are typically absent at the time of diagnosis or represent very small clones below the threshold of detection (1:1000). Metabolomic profiling of isogenic Nt5c2 wild type and Nt5c2 p.R367Q mutant lymphoblasts showed that the loss of fitness phenotype of Nt5c2 mutant cells is associated with excess export of purines to the extracellular space and depletion of the intracellular purine nucleotide pool. Consequently, blocking guanosine synthesis via inosine-5'-monophosphate dehydrogenase (IMPDH) inhibition induced increased cytotoxicity against NT5C2-mutant leukemia lymphoblasts. Similar results -increased resistance to 6-MP, depleted intracellular nucleoside pool and excess export of purines to the culture media and increased sensitivity to mizoribine- were documented in human ALL cell lines with expression of relapse associated NT5C2 mutations (p.R238W, p.K359Q, p.R367Q and p.D407A). The specificity of these interactions was supported by metabolic rescue of mizoribine-induced cytotoxicity in cultures supplemented with guanosine. Similarly shRNA knockdown of IMPDH2 induced increased cytotoxicity in human cell lines expressing mutant NT5C2. Finally, we verified increased response to mizoribine in relapsed-leukemia derived xenograft cells harboring NT5C2 mutations compared with their corresponding NT5C2 wild type diagnostic-sample derived counterparts. In all, these results identify NT5C2 mutation-associated fitness cost and resistance to chemotherapy as key evolutionary drivers shaping clonal evolution in relapsed ALL and support a role for IMPDH inhibition in the treatment of ALL. DisclosuresNo relevant conflicts of interest to declare.

Tissue distribution of polystyrene nanoplastics in mice and their entry, transport, and cytotoxicity to GES-1cells.

With the widespread use of plastics and nanotechnology products, nanoplastics (NPs) have become a potential threat to human health. It is of great practical significance to study and evaluate the distribution of NPs in mice as mammal models and their entry, transport, and cytotoxicity in human cell lines. In this study, we detected the tissue distribution of fluorescent polystyrene nanoplastics (PS-NPs) in mice and assessed their endocytosis, transport pathways, and cytotoxic effects in GES-1cells. We found that PS-NPs were clearly visible in gastric, intestine, and liver tissues of mice and in GES-1cells treated with PS-NPs. Entry of PS-NPs into GES-1cells decreased with the inhibition of caveolae-mediated endocytosis (nystatin), clathrin-mediated endocytosis (chlorpromazine HCl), micropinocytosis (ethyl-isopropyl amiloride), RhoA (CCG-1423), and F-actin polymerization (lantrunculin A). Rac1 inhibitors (NSC 23766) had no significant effect on PS-NPs entering GES-1cells. F-actin levels significantly decreased in CCG-1423-pretreated GES-1cells exposed to PS-NPs. GES-1cell ultrastructural features indicated that internalized PS-NPs can be encapsulated in vesicles, autophagosomes, lysosomes, and lysosomal residues. RhoA, F-actin, RAB7, and LAMP1 levels in PS-NPs-treated GES-1cells were remarkably up-regulated and the Rab5 level was significantly down-regulated compared to levels in untreated cells. PS-NPs treatment decreased cell proliferation rates and increased cell apoptosis. The formation of autophagosomes and autolysosomes and levels of LC3II increased with the length of PS-NPs treatment. The results indicated that cells regulated endocytosis in response to PS-NPs through the RhoA/F-actin signaling pathway and internalized PS-NPs in the cytoplasm, autophagosomes, or lysosomes produced cytotoxicity. These results illustrate the potential threat of NPs pollution to human health.

Polyhexamethyleneguanidine phosphate induces cytotoxicity through disruption of membrane integrity

Polyhexamethyleneguanidine phosphate (PHMG-P) is a polymeric biocide with a guanidine group. It has multiple positive charges in physiological conditions due to nitrogen atom in the guanidine and this cationic property contributes antimicrobial effect by disrupting cell membranes. To determine whether the cationic nature of PHMG-P results in cytotoxicity in human cell lines, anionic compounds were treated with PHMG-P. The cytotoxic effect was evaluated with ROS production and HMGB1 release into media. To verify the protection effect of anion against PHMG-P-induced cell death in vivo, a zebrafish assay was adopted. In addition, membrane disruption by PHMG-P was evaluated using fluorescein diacetate and propidium iodine staining. As a result, anionic substances such as DNA and poly-l-glutamic acids, decreased PHMG-P induced cell death in a dose-dependent manner. While HMGB1 and ROS production increased with PHMG-P concentration, the addition of anionic compounds with PHMG-P reduced the ROS production and HMGB1 release. The mortality of the zebrafish increased with PHMG-P concentration and co-treatment of anionic compounds with PHMG-P decreased mortality in a dose-dependent manner. In addition, FDA and PI staining confirmed that PHMG-P disrupts plasma membrane. Taken together, a cationic property is considered to be one of the main causes of PHMG-P-induced mammalian cell toxicity.

Novel N-Substituted 2-(2-(Adamantan-1-yl)-1H-Indol-3-yl)-2-Oxoacetamide Derivatives: Synthesis and Biological Evaluation.

In this study, a series of novel N-substituted 2-(2-(adamantan-1-yl)-1H-indol-3-yl)-2-oxoacetamide derivatives were synthesized, and evaluated for their cytotoxicity in human cell lines including Hela (cervical cancer), MCF7 (breast cancer ) and HepG2 (liver cancer). Several compounds were found to have potent anti-proliferative activity against those human cancer cell lines and compound 5r showed the most potent biological activity against HepG2 cells with an IC50 value of 10.56 ± 1.14 μΜ. In addition, bioassays showed that compound 5r induced time-dependent and dose-dependent cleavage of poly ADP-ribose polymerase (PARP), and also induced a dose-dependent increase in caspase-3 and caspase-8 activity, but had little effect on caspase-9 protease activity in HepG2 cells. These results provide evidence that 5r-induced apoptosis in HepG2 cell is caspase-8-dependent.

GS-5806 Inhibits a Broad Range of Respiratory Syncytial Virus Clinical Isolates by Blocking the Virus-Cell Fusion Process.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in infants and young children. In addition, RSV causes significant morbidity and mortality in hospitalized elderly and immunocompromised patients. Currently, only palivizumab, a monoclonal antibody against the RSV fusion (F) protein, and inhaled ribavirin are approved for the prophylactic and therapeutic treatment of RSV, respectively. Therefore, there is a clinical need for safe and effective therapeutic agents for RSV infections. GS-5806, discovered via chemical optimization of a hit from a high-throughput antiviral-screening campaign, selectively inhibits a diverse set of 75 RSV subtype A and B clinical isolates (mean 50% effective concentration [EC50] = 0.43 nM). The compound maintained potency in primary human airway epithelial cells and exhibited low cytotoxicity in human cell lines and primary cell cultures (selectivity > 23,000-fold). Time-of-addition and temperature shift studies demonstrated that GS-5806 does not block RSV attachment to cells but interferes with virus entry. Follow-up experiments showed potent inhibition of RSV F-mediated cell-to-cell fusion. RSV A and B variants resistant to GS-5806, due to mutations in F protein (RSV A, L138F or F140L/N517I, and RSV B, F488L or F488S), were isolated and showed cross-resistance to other RSV fusion inhibitors, such as VP-14637, but remained fully sensitive to palivizumab and ribavirin. In summary, GS-5806 is a potent and selective RSV fusion inhibitor with antiviral activity against a diverse set of RSV clinical isolates. The compound is currently under clinical investigation for the treatment of RSV infection in pediatric, immunocompromised, and elderly patients.

A new antibiotic with potent activity targets MscL.

The growing problem of antibiotic-resistant bacteria is a major threat to human health. Paradoxically, new antibiotic discovery is declining, with most of the recently approved antibiotics corresponding to new uses for old antibiotics or structurally similar derivatives of known antibiotics. We used an in silico approach to design a new class of nontoxic antimicrobials for the bacteria-specific mechanosensitive ion channel of large conductance, MscL. One antimicrobial of this class, compound 10, is effective against methicillin-resistant Staphylococcus aureus with no cytotoxicity in human cell lines at the therapeutic concentrations. As predicted from in silico modeling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL. Moreover we show that compound 10 cured a methicillin-resistant S. aureus infection in the model nematode Caenorhabditis elegans. Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.

Investigation of gene transferring efficacy through nano-polyplex consisting of methylated N-(4-pyridinylmethyl) chitosan chloride and poly(ethylenimine) in human cell lines

In this study, gene transfection efficiencies using nano-polyplex as gene carriers were investigated in a variety of human cell lines. Gene carriers were prepared using cationic polymer methylated N-(4-pyridinylmethyl) chitosan chloride (MPyMeChC) and/or poly(ethylenimine) (PEI) to form polyplex via electrostatic interaction with 1 μg of plasmid pGL-3-basic containing CMV promoter/enhancer at different weight ratios. Polyplex formations were confirmed by gel retardation assay. The result suggested that packaging of DNA in PEI-containing polyplexes occurred without interference of DNA integrity. Both size and zeta-potential were increased when PEI was incorporated in polyplex. In vitro transfection was performed in three different cell lines which are a human cervical cancer cell line (HeLa), a human lung adenocarcinoma epithelial cell line (A549) and a human neuroblastoma cell line (SH-SY5Y). The results revealed that transfection profiles were different among the three cell lines which indicated that transfection efficiency through MPyMeChC/PEI polyplex was cell-type dependent. A synergistic effect of MPyMeChC/PEI polyplex was found in HeLa cells with the maximum transfection efficiency at a weight ratio of 1/0.5/1 providing 95% cell viability, approximately. Our study demonstrated an alternative carrier in a non-viral gene delivery system which is able to promote high gene delivery efficiency with low cytotoxicity in human cell lines.

Caffeine augments Alprazolam induced cytotoxicity in human cell lines

Combined effects of alprazolam (Alp), a member of benzodiazepine group of drugs and caffeine on human cell lines, HeLa and THP1 were investigated in this study. Alp mediated cytotoxicity was enhanced while caffeine was present. The cell death was confirmed by observing morphological changes, LDH assay and membrane anisotropic study. Also such combined effects induced elevated level of ROS and depletion of GSH. The mechanism of cell death induced by simultaneous treatment of Alp and caffeine was associated with the calcium-mediated activation of μ-calpain, release of lysosomal protease cathepsin B, activation of PARP and cleavage of caspase 3. Our results indicate that, Alp alone induces apoptosis in human cells but in the presence of caffeine it augments necrosis in a well-regulated pathway. Thus our observations strongly suggest that, alprazolam and caffeine together produce severe cytotoxicity in human cell lines.

Protein precipitation In Vitro as a measure of chemical-induced cytotoxicity: an EDIT sub-programme.

As a priority area of the Evaluation-Guided Development of In Vitro Toxicity and Toxicokinetic Tests (EDIT) programme, an in vitro protein precipitation (PP) assay was used on the 50 reference chemicals of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) project, to confirm and extend the MEIC results. Dose-response curves were generated for only 30 of the chemicals, and the concentrations causing 10% (EC10) and 50% (EC50) protein precipitation versus the positive control were chosen as endpoints. The number of chemicals with a positive response increased to 46 when a new endpoint, the minimum effect concentration (MEC) that induces protein precipitation with respect to the negative control, was used. When the results were correlated with in vitro cytotoxicity in human cell lines, a similarly good correlation was found between the various endpoints of the PP assay at 5 hours and the 24-hour IC50 average cytotoxicity in human cell lines, even though the number of chemicals included in the correlation was larger for the MEC. Using the prediction error, the endpoint that gave the best correlation between the PP assay and human cell cytotoxicity was once more found to be the 5-hour MEC, and this was chosen for the PP assay. The sensitivity of the PP assay is lower than that of the in vitro cell-line cytotoxicity assay, possibly due to its shorter exposure period and because precipitation is the ultimate event in the sequence of a protein disturbance. It is expected that earlier denaturation steps would give better sensitivity. However, this simple, inexpensive and rapid assay could be useful in the early stages of testing chemicals.

Cell Cycle Dependency of Gallium Uptake and Cytotoxicity in Human Cell Lines of Hematological Malignancies

67Gallium (67Ga) is a radionuclide which accumulates in hematological malignancies and is used for diagnostic imaging. We investigated in this in vitro study the cell cycle dependency of cellular uptake and cytotoxicity of 67Ga. Cell cycle synchronization of cells was achieved by counterflow centrifugal elutriation and the use of cytostatic drugs. The human lymphoma cell lines U-937 and U-715 were used and in elutriation experiments we also used the leukemic cell line HL-60. The transferrin receptor (CD71) expression, 67Ga uptake and cell proliferation inhibition were the parameters measured. We also studied cytotoxicity in various schedules for combination of 67Ga and drugs and the residual proliferative capacity was measured. The CD71 expression in the three cell lines increased from 106-177% on S phase cells and from 118-233% on G2M cells, as compared to the G0/G1 cell fraction. The 67Ga uptake varied from 108-127% for S cells and 128-139% for G2M cells. The drugs chosen induced cell cycle phase accumulation in S and/or G2M phase during preincubation. 67Ga preincubation induced accumulation in the G2M phase. Almost all combinations of 67Ga and drugs resulted in a non-interactive effect, except for methotrexate which resulted in an antagonistic effect. No preferential effect of any of the incubation schemes was seen. CD71 expression and 67Ga uptake were increased in S and G2M cells. Combination of 67Ga with drugs which arrest cells in these cell cycle phases did not result in a change in cytotoxicity. However, these results implicate that 67Ga and the cytostatic drugs tested except for methotrexate might be used together or sequentially in therapy.

Synthesis, antiproliferative, and antiviral activity of 4-amino-1-(beta-D-ribofuranosyl)pyrrolo[2,3-d]pyridazin-7(6H)-one and related derivatives.

The synthesis of 4-amino-1-beta-D-ribofuranosylpyrrolo[2,3-d]pyridazin-7 (6H)-one (3) from the reaction of ethyl 3-cyano-1-beta-D-ribofuranosylpyrrole-2-carboxylate (10) and hydrazine is described. The 5:6 pyrrolo[2,3-d]pyridazin-7(6H)-one structure of 3 was established via a three-step conversion of 3 into 1-beta-D-ribofuranosylpyrrolo[2,3-d]pyridazin-4,7(5H,6H)- dio ne (14). 4-Amino-3-chloro-1-beta-D-ribofuranosylpyrrolo[2,3-d]pyridazin+ ++-7(6H)-one (16) 4-amino-3-bromo-1-beta-D-ribofuranosylpyrrolo[2,3-d]pyridazin++ +-7(6H)-one (18) were prepared via N-chlorosuccinimide or N-bromosuccinimide treatment of 4-amino-1-(2,3,5-tri-O-benzyl-beta- D-ribofuranosyl)pyrrolo[2,3-d]pyridazin-7(6H)-one (7) followed by a removal of the benzyl groups with boron trichloride. Direct treatment of 3 with N-iodosuccinimide furnished 4-amino-3-iodo-1-beta-D-ribofuranosylpyrrolo[2,3-d]pyridazin -7(6H)-one (19). The antiproliferative activity of the compounds was determined in L1210, H. Ep. 2 and several additional human tumor cell lines. In L1210 cells, the 3-halo-substituted compounds 16, 18, and 19 exhibited significant cytotoxicity (IC50 = 0.2, 0.1, 0.08 microM, respectively), in contrast to the 3-unsubstituted compound 3, which had only slight activity. The greater antiproliferative activity of 18 and 19 in contrast to 3 was confirmed in H. Ep. 2 cells and KB cells. The antiviral evaluation of these compounds revealed that compounds 16, 18, and 19 were active against human cytomegalovirus in both plaque- and yield-reduction assays. However, this activity was only partially separated from cytotoxicity in human cell lines.