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A Dritschilo

Publications and source records attributed to A Dritschilo.

At least 73 records · Page 4Linked to original sources
PubMed1994

Poly(ADP-ribose) polymerase in HeLa cells--a high resolution two-dimensional gel analysis.

PADPRP is an eukaryotic enzyme responsible for poly(ADP-ribosyl)ation of several chromatin-associated proteins. Consequently, the modified proteins acquire various lengths of negatively charged, covalently bound oligo or poly(ADP-ribosyl) homopolymers. The present study was undertaken to get an insight into the charge and size heterogeneity of the various auto-modified species of PADPRP and other protein acceptors of (ADP-ribose) polymers. Toward this end, we analyzed HeLa cells using high resolution two-dimensional gel electrophoresis (2D-PAGE). Resolution of HeLa total cellular lysates in the basic pH range combined with immunoblots and activity-blots revealed extensive modification and processing of the enzyme. In addition to the native enzyme, a protein of approximately 116 kDa, we observed several proteins that exhibit immunoreactivity to an antibody prepared against a peptide encompassing the N-terminal 20 amino acids of the polymerase. Several protein species showed auto-modifying potential in an in situ activity blot assay. We have also localized the ADP-ribosylated proteins in permeabilized HeLa cells to demonstrate protein acceptors of poly(ADP-ribose).

Adenosine Diphosphate Ribose↗
PubMed1994

Modification of the radiosensitivity of human testicular cancer cells by simian virus 40 sequences.

CRL7800 cells are of human testicular cancer origin and are sensitive to killing by ionizing radiation. After transfection with a plasmid expressing the T-antigen (pSC), cells show enhanced growth and an increased resistance to ionizing radiation. Cell cycle analysis reveals perturbation of a cell cycle checkpoint which, after irradiation, results in an increase in G2-phase arrest in CRL7800VA cells. These experiments demonstrate the modulation of radiation sensitivity and cell cycle arrest of human tumor cells by the introduction of viral genes.

Antigens, Polyomavirus Transforming↗
PubMed1993

Activation of phospholipase D participates in signal transduction pathways responsive to gamma-radiation.

Early responses of mammalian cells to ionizing radiation include the activation of a protein kinase C implicated in the regulation of gene expression, the stimulation of tyrosine kinase activities, and the enhancement of phosphatidylinositol turnover. In the present report we show that clinically relevant doses of gamma-radiation (2 Gy) stimulate phosphatidylcholine hydrolysis in human squamous carcinoma cells. Radiation induced the accumulation of intracellular [3H]choline and the simultaneous increase in [3H]myristoyl-phosphatidic acid, followed by a small increase in the levels of [3H]myristoyl-diacylglycerol. Furthermore, in the presence of ethanol, gamma-radiation stimulated the appearance of [32P]phosphatidylethanol, an indicator of phospholipase D transphosphatidylation activity. These data demonstrate for the first time that phospholipase D activation participates in signaling pathways in response to gamma-radiation.

Carcinoma, Squamous Cell↗
PubMed1993

Modulation of doxorubicin resistance in multidrug-resistant cells by liposomes.

In this study, we have confirmed the ability of liposome-encapsulated doxorubicin to modulate drug resistance, as previously observed in CH LZ cells (Thierry et al., Cancer Commun. 1, 311-316, 1989), in two human multidrug-resistant (MDR) cell lines, the breast cancer MCF-7/ADR cell line, and the ovarian carcinoma SKVLB cell line. This effect was specific to MDR cells, as liposomally encapsulated doxorubicin did not enhance cell sensitivity to the drug in the parental cell lines. Cytotoxicity assays demonstrated that empty liposomes in the presence of free doxorubicin (Dox) reversed resistance to the drug at a level that may be higher than that observed when liposome-encapsulated Dox is used. This effect seems to be due to the high affinity of Dox for cardiolipin, one of the liposome components, which leads to the association of the drug and the cardiolipin-containing liposomes in the culture medium before entry into the cells. Neither pretreatment of empty liposomes before drug treatment nor combined incubation of vincristine and empty liposomes alter MDR in CH LZ cells, suggesting that the drug must be encapsulated or complexed to the liposomes to overcome MDR. Because MDR in CH LZ cells does not seem to be related to GSH level, MDR modulation by liposome-encapsulated Dox apparently may not be effected by altering the GSH function. These results suggest that the enhancement of sensitivity of MDR cells using Dox encapsulated in liposomes or complexed with liposomes may be explained by an increase in cell drug incorporation and by an intracellular drug redistribution. Fluorescence confocal microscopy study indicated that Dox is transported and distributed mainly in intracytoplasmic vesicles in SKVLB and MCF-7/ADR cells, whereas in parental cells the drug is located mainly in the nucleus. In addition, presentation of Dox in liposomes modifies the drug distribution pattern in MDR cells by partially shifting the drug to nuclear compartments. Thus, liposome-associated Dox may bypass the vesicular drug transport in MDR cells, resulting in the enhancement of the drug biological activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Intraoperative high-dose rate interstitial irradiation of hepatic metastases from colorectal carcinoma. Results of a phase I-II trial.

BACKGROUND: Resection of liver metastases from colorectal carcinoma can be curative. Unresectable but liver-confined metastases might be ablated by high-dose radiation with a similar curative result. METHODS: At Georgetown University Hospital, 22 patients with unresectable hepatic metastases from colorectal carcinoma underwent 24 interstitial irradiation procedures at laparotomy in a Phase I-II study. A single dose was administered with a high-dose rate iridium-192 afterloader. Dose to the tumor periphery was 20 Gy, 25 Gy, and 30 Gy in 13, 9, and 2 procedures, respectively. RESULTS: No acute or chronic radiation toxicity has occurred at a median follow-up of 11 months. Median actuarial local control at irradiated sites was 8 months, with 26% actuarial local control at 26 months by computed tomography (CT) or magnetic resonance imaging (MRI) scanning. In the two patients undergoing two procedures each, a second biopsy of previously irradiated areas demonstrated tumor eradication. CONCLUSIONS: This innovative, radical approach to unresectable colorectal hepatic metastases proved safe. Additional study is needed to determine whether interstitial irradiation is as effective as surgical resection, or whether it alters the natural history of the disease or longevity.

Adult↗
PubMed1993

Overcoming multidrug resistance in human tumor cells using free and liposomally encapsulated antisense oligodeoxynucleotides.

Antisense oligonucleotides offer a molecular targeting tool for overcoming cellular multidrug resistance. In order to improve the in vitro and the in vivo transport of oligodeoxynucleotides, we developed a new liposomal delivery system, using the minimal volume entrapment (MVE) technique. We have demonstrated that cellular uptake and intracellular release of oligodeoxynucleotides were facilitated by delivery in liposomes. 15 mers cap phosphorothioate oligodeoxynucleotides complementary to the 5' end of the coding region or to a loop-forming site in the mdr-1 mRNA were encapsulated in liposomes by the MVE method. P-glycoprotein synthesis and doxorubicin resistance were greatly reduced by exposure of the multidrug resistant SKVLB cells to 5 microM liposomally encapsulated oligonucleotide. A lower effect was observed when free oligodeoxynucleotides were used. Oligomers antisense to the loop-forming site appeared to be more effective and more specific in modulating multidrug resistance than oligomers with antisense sequence to the 5' end coding region.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Identification of multiple repeat sequences and transcription-related elements within introns 4, 8 and 9 of human Raf-1.

Oncogenic activation of the human c-raf-1 protein (Raf-1) occurs by truncation of its aminoterminus (regulatory domain) and retention of the carboxyterminus (kinase domain). To gain insight into the structure of human raf-1 genomic DNA corresponding to the regulatory domain of Raf-1, we analyzed the nucleotide sequences of introns 4, 8, and 9. Very high frequencies of the direct and indirect repeats, and A/T nucleotides were observed within introns 4, 8, and 9; and the DNA sequences, 5'-TTAGTCA-3' and 5'-TGATTCA-3', like the DNA recognition site of transcription factor AP-1, were identified within intron 4 of raf-1 in human normal and tumor DNAs. In addition, several transcriptional elements (CAAT box, TATA sequences, eukaryotic transcription initiation sites, and cellular transcriptional elements) were found within introns 4, 8, and 9 of human raf-1. These data suggest: 1) the high frequency of intron-specific repeats is a possible recombinational mechanism for derivation of truncated oncogenic forms of Raf-1; and 2) the multiple transcriptional elements within introns 4, 8, and 9 may have important implications in the regulation of raf-1 transcription and, therefore, its role in cell growth and proliferation.

Base Sequence↗
PubMed1993

Neoplastic transformation of a human prostate epithelial cell line by the v-Ki-ras oncogene.

Investigations of mechanisms of human prostate carcinogenesis are limited by the unavailability of a suitable in vitro model system. We have demonstrated that an immortal, but nontumorigenic, human epithelial cell line (267B1) established from fetal prostate tissue can be malignantly transformed by a biological carcinogen, and can serve as a useful model for investigations of the progression steps of carcinogenesis. Activated Ki-ras was introduced into 267B1 cells by infection with the Kirsten murine sarcoma virus. Morphological alterations and anchorage-independent growth were observed; when cells were injected into nude mice, poorly differentiated adenocarcinomas developed. These findings represent the first evidence of malignant transformation of human prostate epithelial cells in culture, and support a role for Ki-ras activation in a multistep process for prostate neoplastic transformation.

Cell Line↗
PubMed1993

Radiation-induced neoplastic transformation of human cells.

Ionizing radiation can induce cancers in humans and animals and can cause in vitro neoplastic transformation of various rodent cell systems. However, numerous attempts to achieve neoplastic transformation of human cells by radiation have generally proven unsuccessful. Neoplastic transformation of immortalized human epidermal keratinocytes by X-ray irradiation has recently been reported. The carcinogenic effect of radiation on cultured human cells will be briefly reviewed. The current state-of-the-art in radiation-induced transformation of human cells in culture is presented. This will provide insight into the molecular and cellular mechanisms in the conversion of normal cells to a neoplastic state of growth.

Cell Transformation, Neoplastic↗
PubMed1992

High-resolution two-dimensional electrophoresis of nuclear proteins: a comparison of HeLa nuclei prepared by three different methods.

A comparative analysis of HeLa cell nuclear proteins is presented using Iso-Dalt methods of protein resolution in two dimensions. The nuclear proteins were prepared by (1) spin through glycerol cushion, (2) spin through sucrose cushion, or (3) Triton wash. Improved resolution of total nuclear proteins in the range of pH 4.5-6.0 was achieved by substituting longer isotubes in combination with broad-range ampholines during the isoelectric focusing step. An attempt to indicate silver stainable protein spots common to total cellular extracts and nuclear preparations has been made. Also, proteins that appear to be well represented in all three nuclear preparations and remain undetectable in the total cellular protein pattern have been marked as probably being enriched nuclear proteins. Such a comparative analysis of whole nuclear protein preparations made it possible to document that the different preparations preserved the same set of proteins. The Triton-wash method of obtaining nuclei was identified as the preferred choice. Coomassie-stained gels and blots of these nuclear proteins could serve as a guide for accessing relevant protein spots for further biochemical analysis such as immunoblotting.

Antibody Specificity↗
PubMed1992

Mutations in the p53 gene in radiation-sensitive and -resistant human squamous carcinoma cells.

Five of six human squamous cell carcinoma (SCC) cell lines characterized as radiation sensitive (SQ-38, SCC-9, SQ-9G) or radiation resistant (SQ-20B, SCC-35, JSQ-3) exhibited alterations of the p53 gene. The point mutations and a deletion were detected by using single-stranded conformational polymorphism analysis and polymerase chain reaction-direct sequencing. Interestingly, three of three radiation-sensitive and two of three radiation-resistant cell lines revealed mutations in the p53 gene. Point mutations were located in exons 4, 6, and 8 (at codons 72 and 298 in JSQ-3; 273 in SCC-35; 196 in SQ-38), and deletions consisted of 32 base pairs between codons 274 and 285 in SCC-9 and 1 base pair at codon 271 in SQ-9G. Three mutations resulted in substitutions for an arginine residue. Immunocytochemical analysis confirmed p53 protein overexpression in SCC-35 cells which contained a missense mutation at codon 273. In contrast to previous studies which linked alterations in ras, myc, and raf expression with radiation resistance, this study indicates that mutations in the tumor suppressor gene, p53, do not directly correlate with such resistance.

Carcinoma, Squamous Cell↗
PubMed1992

Intracellular availability of unmodified, phosphorothioated and liposomally encapsulated oligodeoxynucleotides for antisense activity.

We have studied factors which may effect the intracellular availability of oligonucleotides to achieve antisense activity. 15-20 mer unmodified, phosphorothioate modified and liposomally encapsulated oligodeoxynucleotides have been tested in leukemia MOLT-3 cells. Phosphorothioate analogs penetrated and accumulated intact in cells in contrast to unmodified oligomers, which showed a high instability in cell culture medium. A slow decrease of intracellular concentration of undegraded phosphorothioate oligodeoxynucleotides was observed after cell treatment and could be predominantly explained by a significant efflux transport. Using laser-assisted confocal microscopy we have observed that fluorescein 5-end-labeled phosphorothioate derivatives predominantly distributed in intracytoplasmic endocytic vesicles following cell treatment. The end-capped version of phosphorothioate oligodeoxynucleotides exhibited greater cellular uptake than fully modified analogues while exhibiting similar biological stability. Liposome encapsulation made possible oligomer protection in serum-containing medium and substantially improved cellular accumulation. Furthermore, the efflux rate of oligomer initially introduced within liposomes is 2-fold lower than that observed in cells which have been incubated with free oligonucleotides. Liposomal preparations of oligodeoxynucleotides facilitate release from endocytic vesicles, and thus, cytoplasmic and nuclear localization are observed following cell treatment. Furthermore, intracellular distribution studies demonstrate that intracellular transport of unmodified oligomers is effectively achieved using the liposomal carrier.

Base Sequence↗
PubMed1992

Effect of liposomes on P-glycoprotein function in multidrug resistant cells.

Presentation of doxorubicin in liposomes has shown to enhance the sensitivity of multidrug resistant CH LZ cells to the drug (Thierry et al. Cancer Commun. 1:311-316, 1989). We confirmed that liposomally encapsulated doxorubicin may partially overcome multidrug resistance in the human ovarian carcinoma SKVLB cell line and that this effect is, at least in part, due to an increase of cellular drug accumulation. When used at high concentration, empty liposomes appear to be specifically cytotoxic in the MDR SKVLB and CH LZ cells. As observed with certain multidrug resistance modulators, empty liposomes inhibited the specific [3H]-vincristine binding to P-glycoprotein-enriched membranes isolated from CH LZ cells (60% at 0.2 mg lipid/ml). Our data suggest that liposomes may alter the P-glycoprotein function by direct interaction.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Neoplastic transformation of immortalized human keratinocytes by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most powerful carcinogen ever tested in animals. Recent epidemiological studies have suggested its carcinogenic potential in humans. In the present study, nontumorigenic human epidermal keratinocytes immortalized by adenovirus 12-simian virus 40 (Ad12-SV40) were transformed by exposures of TCDD equal to or greater than 0.1 nM for 2 wk. These transformed cells showed morphological alterations and induced carcinomas when transplanted into nude mice, whereas no such transformation phenotypes were observed with exposures of less than 0.1 nM for 2 wk. Primary human epithelial keratinocytes exposed to various concentrations of TCDD failed to show any evidence of transformation. Induction of aryl hydrocarbon hydroxylase activity was dose dependent, as was transformation. Thus, the carcinogenicity of TCDD in this human cell system appears to be an Ah receptor-mediated process. The present study represents the first evidence of neoplastic conversion of human cells exposed to this environmentally important chemical.

Animals↗
PubMed1992

Differential expression of proteins in radioresistant and radiosensitive human squamous carcinoma cells.

BACKGROUND: Previous studies support a genetic basis for cellular radioresistance. The associated biochemical and molecular events, however, are not fully understood. PURPOSE: We investigated the differential protein pattern as a molecular determinant of resistance or sensitivity of head and neck squamous carcinoma cells to ionizing radiation. METHODS: Using two-dimensional polyacrylamide gel electrophoresis followed by computer-assisted quantitative analysis, we compared the protein profiles of three relatively radioresistant and three relatively radiosensitive head and neck squamous carcinoma cell lines (previously characterized by in vitro and clinical parameters as radioresistant or radiosensitive) to determine which proteins were consistently expressed or enhanced in the radioresistant compared with the radiosensitive phenotype. RESULTS: Our analysis indicated that 14 proteins were preferentially expressed in the radio-resistant cell lines SQ-20B, JSQ-3, and SCC-35, with one protein (molecular mass of 92 kd and pI of 5.5) distinctly expressed in the radioresistant cell lines. Four proteins were enhanced by greater than 10-fold, three were enhanced fivefold to 10-fold, and six were enhanced twofold to fivefold in the radioresistant cell lines. In addition, we observed a second set of 15 proteins preferentially expressed in the radio-sensitive cell lines SQ-9G, SQ-38, and SCC-9. A 40-kd protein (pI 7.1) was distinctly expressed in the radiosensitive cell lines. The remaining radiosensitive cell-specific proteins were enhanced by greater than 10-fold (two proteins), fivefold to 10-fold (two proteins), or twofold to fivefold (10 proteins) compared with their counterparts in the radioresistant cell lysates. CONCLUSION: These results provide evidence for differential protein expression associated with phenotypic expression of cellular radioresistance or radiosensitivity. IMPLICATIONS: This study will facilitate the characterization of these proteins correlated with the radiation response-specific phenotype.

Carcinoma, Squamous Cell↗
PubMed1992

Radiotherapy of malignant subdiaphragmatic implants in advanced ovarian carcinoma: a new technique.

We report the development of a new technique using remote afterloading intraoperative radiation therapy to deliver a tumoricidal dose to diaphragmatic tumor implants. A multi-positional lucite applicator was designed based on anatomic studies of the diaphragmatic surface to accommodate a high dose rate iridium source in a series of needles placed 1.5 cm apart. The applicator curvature can vary from planar to full accommodation of the diaphragmatic surface with a constant source to surface distance of 0.5 cm. The applicator has been piloted in three patients with ovarian carcinoma with residual subdiaphragmatic disease found at second look laparotomy, to deliver a dose of 1,500 to 2,000 cGy at 0.5 cm. Tolerance of the diaphragm and hepatic surface has been excellent. There were no postoperative complications and no deterioration in liver function studies. The additional postoperative external beam irradiation directed with the aid of surgically placed clips and gated to respiratory movements permits achievement of a tumoricidal dose while limiting the treated volume and related toxicities.

Brachytherapy↗