Inhibition of N-methyl-N'-nitro-N-nitrosoguanidine-induced methotrexate and adriamycin resistance in CHO cells by adeno-associated virus type 2

Discovery of phenylsulfonylfuroxan derivatives as gamma globin inducers by histone acetylation

N-oxide derivatives 5(a-b), 8(a-b), and 11(a-c) were designed, synthesized and evaluated in vitro and in vivo as potential drugs that are able to ameliorate sickle cell disease (SCD) symptoms. All of the compounds demonstrated the capacity to releasing nitric oxide at different levels ranging from 0.8 to 30.1%, in vivo analgesic activity and ability to reduce TNF-α levels in the supernatants of monocyte cultures. The most active compound (8b) protected 50.1% against acetic acid-induced abdominal constrictions, while dipyrone, which was used as a control only protected 35%. Compounds 8a and 8b inhibited ADP-induced platelet aggregation by 84% and 76.1%, respectively. Both compounds increased γ-globin in K562 cells at 100 μM. The mechanisms involved in the γ-globin increase are related to the acetylation of histones H3 and H4 that is induced by these compounds. In vitro, the most promising compound (8b) was not cytotoxic, mutagenic and genotoxic.

Immiscible poly(lactic acid)/poly(ε-caprolactone) for temporary implants: Compatibility and cytotoxicity

This manuscript focuses on the effect of the addition of a low molecular weight triblock copolymer derived from ε-caprolactone and tetrahydrofuran (CT) on the compatibility and cytotoxicity of immiscible poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) blends. Binary and tertiary PLA/PCL blends were prepared by melt mixing in a twin-screw extruder and their morphological, mechanical and thermal behaviors were investigated by scanning electron microscopy (SEM), tensile and Izod impact test, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). SEM micrographs showed the CT copolymer suppressed the coalescence phenomena and maintained the size of dispersed PCL domains at approximately 0.35µm. Bioresorbable PLA/PCL blends containing 5wt% of CT copolymer exhibited a remarkable increase in ductility and improved toughness at room temperature. Although the CT copolymer increased the interfacial adhesion, the DMA results suggest it also acts as a plasticizer exclusively for the PCL phase. The cell viability evaluated by the XTT assay confirmed PLA/PCL blends compatibilized by CT copolymer exerted no cytotoxic effect.

Characterization and in vitro evaluation of bacterial cellulose membranes functionalized with osteogenic growth peptide for bone tissue engineering

The aim of this study was to characterize the physicochemical properties of bacterial cellulose (BC) membranes functionalized with osteogenic growth peptide (OGP) and its C-terminal pentapeptide OGP[10-14], and to evaluate in vitro osteoinductive potential in early osteogenesis, besides, to evaluate cytotoxic, genotoxic and/or mutagenic effects. Peptide incorporation into the BC membranes did not change the morphology of BC nanofibers and BC crystallinity pattern. The characterization was complemented by Raman scattering, swelling ratio and mechanical tests. In vitro assays demonstrated no cytotoxic, genotoxic or mutagenic effects for any of the studied BC membranes. Culture with osteogenic cells revealed no difference in cell morphology among all the membranes tested. Cell viability/proliferation, total protein content, alkaline phosphatase activity and mineralization assays indicated that BC-OGP membranes enabled the highest development of the osteoblastic phenotype in vitro. In conclusion, the negative results of cytotoxicity, genotoxicity and mutagenicity indicated that all the membranes can be employed for medical supplies, mainly in bone tissue engineering/regeneration, due to their osteoinductive properties.

Cellular chemosensitivity assays: an overview

Data on cell viability have long been obtained from in vitro cytotoxicity assays. Today, there is a focus on markers of cell death, and the MTT cell survival assay is widely used for measuring cytotoxic potential of a compound. However, a comprehensive evaluation of cytotoxicity requires additional assays which -measure short and long-term cytotoxicity. Assays which measure the cytostatic effects of compounds are not less important, particularly for newer anticancer agents. This overview discusses the advantages and disadvantages of different non-clonogenic assays for measuring short and medium-term cytotoxicity. It also discusses clonogenic assays, which accurately measure long-term cytostatic effects of drugs and toxic agents. For certain compounds and cell types, the advent of high throughput, multiparameter, cytotoxicity assays, and gene expression assays have made it possible to predict cytotoxic potency in vivo.

Differential growth inhibitory effects ofW. somnifera root andE. officinalis fruits on CHO cells

The Chinese Hamster ovary (CHO) cell line is widely used for measuring drug cytotoxicity and resistance. Therefore, the effects of two major Ayurvedic drugs (W. somnifera root and E. officinalis fruits) on the short and long-term growth of these cells were investigated. A standard 96-well plate assay was used to measure short-term growth. For assessment of long-term growth, the colony formation assay (CFA) was used, which measures clonogenic potential. This assay is the best measure of the cytotoxicity of anticancer drugs and the radio-sensitivity of tumor cells. As reported by others, the aqueous extracts of both herbal drugs were found to have short-term growth inhibitory effects on CHO cells when added to cells at the time of cell plating. However, this is the first report showing that these two herbal drugs have significantly different effects on the long-term growth of CHO cells. Thus, extracts of W. somnifera root, but not E. officinalis fruit, caused a reproducible, dose dependent, inhibition of colony formation of CHO cells.

Enhanced sensitivity of small cell lung cancer cell lines to cisplatin and etoposide after infection with adeno-associated virus type 2

In previous studies we have reported the sensitisation of human tumour cells to gamma irradiation and chemotherapeutic drugs upon infection with the human non-pathogenic adeno-associated virus type 2 (AAV-2) in vitro and in vivo. Treatment of small cell lung cancer (SCLC) is consistently hampered by relapses due to the selection of chemotherapy-resistant cell clones. Hence, we were interested to test whether selection of chemotherapy-resistant SCLC cells might be reduced or even prevented if chemotherapy is applied in combination with AAV-2 infection. In vitro proliferation assays indicated that the number of proliferating cells, after combined treatment with cisplatin and etoposide, can be significantly reduced by concomitant AAV-2 infection, as compared with treated but non-infected controls. H446 SCLC cells, which show resistance to etoposide/cisplatin chemotherapy (compared with a cell line which was never chemotherapeutically treated before, like NCI-H209) were significantly more sensitive after AAV-2 infection, suggesting that the therapeutic efficacy of chemotherapy in SCLC can be enhanced even if the cells are already relatively resistant to chemotherapy. Similarly, in vivo growth of tumours induced by inoculation of SCLC cells into immunocompromised nude mice was reduced more efficiently in AAV-2-infected animals compared with tumours in mice treated with chemotherapeutic drugs alone. These data extend and further support our previous reports on AAV functions which might be useful in improving the efficacy of chemotherapeutic drugs used in human cancer treatment.

Improved efficacy of chemotherapy by parvovirus-mediated sensitisation of human tumour cells

Increasing resistance of tumour cells towards the cytotoxic action of chemotherapeutic drugs is a major limitation in the treatment of cancer patients. The non-pathogenic human adeno-associated viruses (AAV) have been reported to sensitise HeLa cervical cancer cells to gamma irradiation in vivo and in vitro. To test whether these parvoviruses might render other human tumour cells more sensitive towards chemotherapeutic drugs, we analysed the effects of AAV type 2 (AAV-2) infection on established cancer cell lines and freshly explanted tumour biopsies treated with chemotherapeutic agents (e.g. cisplatin). AAV-2 infection significantly increased the cytotoxic activity of chemotherapeutic drugs compared with uninfected controls. AAV-2 infection without concomitant chemotherapeutic treatment had no significant effect on viability of the cells. In nude mice, combined application of AAV-2 infection and chemotherapeutic treatment significantly increased the therapeutic activity on tumours arising from subcutaneously injected tumour cells compared with tumours treated by chemotherapeutics only. These results indicate that AAV-2 infection sensitises human cancer cells towards the cytotoxic action of chemotherapeutic drugs.

Selective effects of DNA damaging agents on HIV long terminal repeat activation and virus replication in vitro

Much attention has recently focused on the observation that UV light can activate the long terminal repeat (LTR) of the human immunodeficiency virus (HIV). Although the mechanism of LTR activation remains obscure, several lines of investigation have suggested that it is a result of activation of the NF-kappa B transcription factor(s) following signaling events related to generalized DNA damage. In this report, we present data demonstrating that HIV LTR activation is not a general consequence of cellular DNA damage, but rather a process unique to specific genotoxic stimuli, and that it does not necessarily depend on activation of NF-kappa B. Furthermore, we demonstrate that several of these agents can significantly increase HIV replication and accelerate CD4-positive lymphocyte cytotoxicity in vitro. These findings, therefore, could have clinical significance to AIDS patients with malignancies who are undergoing radiotherapy and chemotherapy.

Modulation of the cellular phenotype by integrated adeno-associated virus

The adeno-associated virus (AAV) rep gene encodes a series of overlapping, multifunctional, nonstructural proteins (Rep proteins) which regulate the viral life cycle and which are also capable of trans-regulating nonviral gene expressions (reviewed in Berns, 1990, Microbiol. Rev. 54, 316-329). To investigate the expression of the AAV rep gene in a cellular chromosomal context, SV40-transformed Chinese hamster embryo (OD4) cells were infected with an AAV/neo hybrid virus and progeny resistant to the antibiotic G418 were selected and amplified. Chromosomal integration and RNA transcription of the AAV and neo DNA inserts were confirmed by Southern and Northern blotting procedures. One of the G418R cell lines stably expressed a protein which reacted specifically with AAV anti-Rep antiserum in Western immunoblots. The stable integration of AAV rep DNA, which did not interfere with cell proliferation under normal growth conditions, was associated with two changes in cellular phenotype: eight of nine lines were markedly more sensitive to UV light (254 nm) than were the parental OD4 cells; and seven of the nine lines had lost the capacity to promote SV40 origin DNA amplification in vitro, in contrast to the parental OD4 cells. OD4 cells transformed to G418R by AAV/neo DNA constructs with a deleted rep gene, or by a neo DNA construct lacking AAV DNA, did not display these phenotypic changes. It is suggested that stable integration of the AAV rep gene interferes with cellular processes connected with DNA repair and gene amplification.

Modification of some biological properties of HeLa cells containing adeno-associated virus DNA integrated into chromosome 17

Parvoviruses are known to interfere with cellular transformation and carcinogenesis. Since infecting adeno-associated virus (AAV) frequently integrates its DNA into the cellular genome, we analyzed whether this integration influences the transformed phenotype of the human tumor cell line HeLa. Analysis of three independent HeLa cell clones with integrated AAV DNA (HA-3x, HA-16, and HA-28) revealed the following phenotypic changes of these cells: (i) reduced growth rate, (ii) increased serum requirement, (iii) reduced capacity for colony formation in soft agar, (iv) reduced cloning efficiency on plastic, (v) elevated sensitivity to genotoxic agents (N-methyl-N'-nitro-N-nitrosoguanidine, 7,12-dimethylbenz[a]anthracene, human tumor necrosis factor alpha, UV irradiation [256 nm], and heat [42 degrees C]), and (vi) reduced sensitivity to the cytolytic effect of parvovirus H-1. Reduced growth rate and enhanced sensitivity to gamma irradiation were also observed in vivo when tumors from AAV DNA-containing HeLa cells were transplanted into nude mice. This alteration of the biological properties of HeLa cells was independent of the number of AAV genomes integrated, the physical structure of integrated AAV DNA, and the transcription of AAV genes. Integration of AAV DNA was found to occur preferentially on the long arm of chromosome 17 in the three HeLa cell clones analyzed. These findings demonstrate that genomic integration of AAV DNA can alter the biological properties of human tumor cells.

Antineoplastic activity of parvoviruses

The family of Parvoviridae is composed of small, nuclear-replicating viruses that are without envelope and contain an essentially single-stranded, linear DNA genome. Certain parvoviruses proved to have the remarkable capacity to prevent the formation of spontaneous as well as virtually- and chemically-induced tumors in laboratory animals. Established tumor cells serve as targets for the antineoplastic activity of parvoviruses, since the growth of preformed cancer cells transplanted in recipient animals can also be inhibited by these viruses. Furthermore, epidemiological studies in humans have revealed a correlation between serological evidence of parvoviral infection and a lower incidence of certain cancers. The parvoviral life-cycle appears to depend on cellular factors that are expressed as a function of proliferation and differentiation. This subordination may account for the oncotropism of parvoviruses in vivo and for the specificity of their interactions with (pre-)neoplastic cells under appropriate culture conditions. Thus, certain parvoviruses were found to preferentially lyse initiated or stably transformed cells in vitro, as a possible result of the stimulation of the production and/or activity of cytotoxic viral proteins. Parvoviruses can also have a cytostatic effect and cause the reversion of transformation traits, parallel to the down-modulation of the expression of defined genes, in particular oncogenes. Such direct disturbance of neoplastic cells or their precursors may participate in the oncosuppressive activity of parvoviruses, although indirect viral effects mediated by host defense mechanisms also deserve to be considered. Altogether, these properties suggest the possible use of parvoviruses as probes to investigate the process of malignant transformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Origin of adeno-associated virus DNA replication is a target of carcinogen-inducible DNA amplification

DNA amplification of the helper-dependent parvovirus AAV (adeno-associated virus) can be induced by a variety of genotoxic agents in the absence of coinfecting helper virus. Here we investigated whether the origin of AAV type 2 DNA replication cloned into a plasmid is sufficient to promote replication activity in cells treated by the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). A pUC19-based plasmid, designated pA2Y1, which contains the left terminal repeat sequences (TRs) representing the AAV origin of replication and the p5 and p19 promoter but lacks any functional parvoviral genes is shown to confer replication activity and to allow selective DNA amplification in carcinogen-treated cells. Following transfection of plasmid pA2Y1 or plasmid pUC19 as a control, density labeling by a bromodeoxyuridine and DpnI resistance assay suggested a semi-conservative mode of replication of the AAV origin-containing plasmid. Furthermore, the amount of DpnI-resistant full-length pA2Y1 DNA molecules was increased by MNNG treatment of cells in a dose-dependent manner. In addition, DNA synthesis of plasmid pA2Y1 was studied in vitro. Extracts derived from MNNG-treated CHO-9 and L1210 cells displayed greater synthesis of DpnI-resistant full-length pA2Y1 molecules than did nontreated controls. Experiments with specific enzyme inhibitors suggested that the reaction is largely dependent on DNA polymerase alpha, DNA primase, and DNA topoisomerase I. Furthermore, restriction endonuclease mapping analysis of the in vitro reaction products revealed the occurrence of specific initiation at the AAV origin of DNA replication. Though elongation was not very extensive, extracts from carcinogen-treated cells markedly amplified the AAV origin region. Our results, including electron microscopic examination, suggest that the AAV origin/terminal repeat structure is recognized by the cellular DNA replicative machinery induced or modulated by carcinogen treatment in the absence of parvoviral gene products.