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G Toffoli

Publications and source records attributed to G Toffoli.

At least 19 recordsLinked to original sources
PubMed1995

Structure-activity relationship of verapamil analogs and reversal of multidrug resistance.

We studied the relationship between the chemical structure and multidrug resistance (MDR) reversal activity of racemic verapamil (VER) and 14 VER analogs (VAs). The LoVo-R human colon carcinoma cell line was used as an experimental model. This cell line exhibited a typical MDR phenotype and overexpressed the MDR1 gene products. Key structural features were identified as being related to MDR reversal and cytotoxic activity. In particular, we demonstrated that the methoxy groups in the VER molecule structure [1.7-Bis-(3.4-dimethoxyphenyl)-3-methylaza-7-cyan-8-methyl-n onane] prevented cytotoxicity when the VAs were used alone, whereas the 7-cyan-8-methyl groups were important for MDR reversal activity and interaction with P-glycoprotein (P-gp). Among the VAs tested, the most active compounds were gallopamil, R-isomer of VER (R-VER), and nor-VER, which potentiated doxorubicin (DOX) cytotoxicity by 52.3 +/- 7.2 (n = 3 +/- SD), 38.9 +/- 6.4 (n = 4 +/- SD), and 35.4 +/- 4.3 (n = 3 +/- SD) times, respectively. The reversal activity of these compounds was similar to that of VER, which enhanced DOX cytotoxicity by 41.3 +/- 5.0 (n = 3 +/- SD) times. The potentiation of DOX cytotoxicity was associated with an increase in DOX uptake in LoVo-R cells and with an increased [3H]azidopine P-gp photolabeling inhibition. Some compounds that had a high reversal potency (i.e. R-VER and nor-VER) showed a lower calcium antagonist activity than VER, and seem useful candidates for the treatment of MDR in cancer patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

P-glycoprotein but not topoisomerase II and glutathione-S-transferase-pi accounts for enhanced intracellular drug-resistance in LoVo MDR human cell lines.

The biochemical bases of the multidrug-resistant (MDR) phenotype were investigated in drug-resistant sublines derived from LoVo human colon carcinoma cell lines by doxorubicin (DOX) and teniposide (VM26) selection. In addition to P-glycoprotein-mediated drug extrusion through the plasma-membrane, LoVo MDR cells display a further drug-resistance mechanism. That is, to achieve equitoxic effects, LoVo MDR sublines require much higher intracellular drug concentrations than those required by LoVo drug-sensitive parent cell line. Involvement of mdr1, topoisomerase II and glutathione-S-transferase-pi (GST-pi) drug-resistance systems in intracellular drug resistance was investigated. Pharmacologic and biochemical data indicated that intracellular drug resistance in LoVo MDR sublines is uniquely consequent to the drug-transporting property of intracytoplasmic membrane-bound P-glycoprotein molecules which compartment drugs in vacuole-like structures.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Expression of the mdr1 gene in human colorectal carcinomas: relationship with multidrug resistance inferred from analysis of human colorectal carcinoma cell lines.

To investigate whether mdr1 gene products are involved in conferring the chemoresistant phenotype to human colorectal carcinomas (HCCs), we determined the mdr1 mRNA expression level (mdr1 EL) in surgical specimens from 29 pharmacologically untreated patients and analyzed the relationship between mdr1 EL and drug resistance in an in vitro experimental model. This consisted of 7 HCC cell lines chosen to cover the range of mdr1 ELs detected in the neoplastic specimens. No relationship was observed between the mdr1 EL of the HCC cell lines and the degree of chemosensitivity found for each drug tested, regardless of whether mdr1 gene products may [doxorubicin (DOX), vincristine (VCR), and actinomycin-D (ACT-D)] or may not affect [cis-diamminedichloroplatinum (CDDP)] drug-transmembrane equilibria. Conversely, a direct relationship was found between the mdr1 EL of HCC cell lines and the number of drug-resistant (DR) colonies arising from each parent cell line treated in continuous culture with high DOX concentrations. In addition, the chemoresistance index and mdr1 EL of the DR cell variants were roughly proportional to the mdr1 EL of the parent cell line. Our findings suggest that primary HCCs derive multidrug resistance from biochemical mechanism(s) other than mdr1 gene products. However, the mdr1 EL might be indicative of a predisposition to develop DR cell variants after chemotherapeutic treatment.

Antineoplastic Agents↗
PubMed1992

Mechanism of multidrug resistance in human tumour cell lines and complete reversion of cellular resistance.

The biochemical basis of the multidrug-resistant (MDR) phenotype has been investigated in drug-resistant sublines derived from LoVo and SW984 human colon carcinoma cell lines by doxorubicin selection. Besides drug extrusion through the plasma membrane, two further observations, both ascribable to the drug transport property of the gp170 glycoprotein, were made. First drug deposition into cytoplasmic membranous structures which allows cells to tolerate a high intracellular drug concentration since it prevents drugs from reaching their cellular target site(s). Secondly drug removal from the complexes formed by interaction of drug with target cellular macromolecules, a phenomenon which extends its an effect that continues after treatment and appears to be the most important resistance mechanism in MDR cells. Treatments based on the gp170 inhibitory property of verapamil were developed that allowed abrogation of resistance in MDR cell lines, a strategy that may be applicable to therapy treatments.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Expression of glutathione-S-transferase-pi in human tumours.

Expression of glutathione-S-transferase-pi (GST-pi) gene was quantitatively analysed on various human tumours (renal cell, colorectal, head and neck, ovarian carcinomas, soft tissue sarcomas; non-Hodgkin lymphomas) and on the corresponding normal tissues when available (kidney, colorectum and head and neck). GST-pi mRNA expression level was found to be significantly higher in tumours (P less than 0.01) than in the normal counterparts (mainly 7.3, 3.5- and 3.0-fold in colorectal, head and neck, and renal carcinomas, respectively). Most tumours displayed a significant relationship between higher GST-pi expression level and poor differentiation grade of tumour cells, thus suggesting a relationship between GST-pi activity, neoplastic transformation and cellular differentiation grade. The high requirement of GST-pi activity neoplastic cells displayed was not singularly related to cellular replication rate. Finally, GST-pi gene expression levels were not affected by chemotherapeutic treatments.

Adolescent↗
PubMed1992

Expression of MDR1 and GST-pi in human soft tissue sarcomas: relation to drug resistance and biological aggressiveness.

Human soft tissue sarcomas (HSTS) in adults are a family of mesenchymal tumors characterized by high biological aggressiveness and general refractoriness to chemotherapy. A series of 36 HSTS, 24 untreated and 12 homogeneously treated with a presurgical chemotherapeutic regimen consisting of doxorubicin (intra-arterial) and iphosphamide (intra-vein), was analyzed for expression of MDR1 and the glutathione-S-transferase-pi (GST-pi) gene in order to identify molecular phenomena which may be implicated in the chemoresistance displayed by these tumors. The MDR1 gene was expressed in a greater percentage of drug-treated tumors and at higher levels than in untreated ones. By contrast, chemotherapeutic treatment has no effect on GST-pi mRNA expression. The GST-pi expression level (EL) was much higher in the HSTS with biologically aggressive features. In fact, significant correlations were observed between GST-pi and histologic grade (p = 0.01); aneuploidy (p less than 0.01); and histone H3 EL (p = 0.01), suggesting a possible causal relationship between GST-pi activity and biological aggressiveness in HSTS.

Adult↗
PubMed1991

Frequent occurrence of Ha-rasl allelic deletion in human ovarian adenocarcinomas.

Fourteen human adenocarcinoma specimens were analyzed for somatic abnormalities affecting genes of the ras family. No amplification of the 3 ras genes was detected. Allelic deletion of the Ha-rasl gene (11p15.5) was found to be a very common abnormality in human ovarian adenocarcinomas (4 out of 7 informative cases). However, in these neoplasm deletion of a presumed normal Ha-rasl allele is not a contributory factor in strengthening the tumorigenic effect of a mutated allele. More probably, Ha-rasl allelic losses are markers of larger chromosomal deletions. Analyses at gamma globin loci (11p15.5) and int-2 locus (11q13) provided evidence that the deletions may extend from Ha-rasl locus towards the centromere but never involve loss of the entire chromosome 11. These findings may suggest that a putative tumor suppressor gene closely linked to Ha-rasl in 11p15.5 is involved in ovarian cancerogenesis.

Adenocarcinoma↗
PubMed1991

Pleiotropic-resistant phenotype is a multifactorial phenomenon in human colon carcinoma cell lines.

The biochemical basis of multidrug-resistant (MDR) phenotype has been investigated in drug-resistant sublines independently obtained in our laboratories by single step doxorubicin (DOX) selection of LoVo, DLD1, and SW948 human colon carcinoma (HCC) cell lines. All the chemoresistant sublines have been found to be cross-resistant to DOX, actinomycin-D (ACT-D) and vincristine (VCR) but not to cis-diamminedichloroplatinum (CDDP), and have exhibited an increased expression level of mdr1 mRNA and gp170 glycoprotein. Comparative analyses in drug-resistant and sensitive cells of resistance index, extracellular and intracellular equitoxic DOX concentrations, and mdr1 gene products expression have indicated that MDR phenotype is a multifactorial phenomenon due to different and possibly independent biochemical mechanisms which cooperate, in varying degrees from cell line to cell line, in conferring cellular chemoresistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

c-myc overexpression is a tumor-specific phenomenon in a subset of human colorectal carcinomas.

The transcriptional activity of the c-myc proto-oncogene was examined in 25 primary human colorectal carcinomas and their corresponding normal mucosae. The purpose was to determine whether the elevated levels of c-myc expression, frequently detected in this type of tumor, might be the consequence of alterations in the cell growth rate or the effect of a real transcriptional deregulation of the gene. In about 44% of the tumors the elevated c-myc expression was consequent to the enhanced growth rate of the neoplastic tissue, as estimated by the expression of the S-phase-specific histone H3 gene. In the other 56%, c-myc overexpression did not entirely depend on the proliferative activity of the neoplastic population. In this latter group, c-myc deregulation did not reside in structural modifications of the putative regulatory regions of the gene. Therefore, c-myc overexpression, at least in a subset of colorectal cancer, seems to be consequent to alterations in transregulative phenomena exerted on the c-myc gene by other genetic loci.

Adenocarcinoma↗
PubMed1989

Sensitivity pattern of normal and Ha-ras transformed NIH3T3 fibroblasts to antineoplastic drugs.

Ha-ras-transformed NIH3T3 fibroblasts were compared with the parental cell line to investigate the influence of the Ha-ras oncogene on cellular chemosensitivity to antineoplastic drugs. Four NIH3T3 cell clones independently transformed by the Ha-ras oncogene, activated by mutation or overexpression, were analyzed: 3 clones were obtained by transfection of NIH3T3 cells with a mutation-activated Ha-ras gene and 1 clone by transfection of a large copy number of the normal Ha-ras proto-oncogene. Chemosensitivity of the transformed clones and of the parental cell line was analyzed when cells were in the same condition of proliferative activity and cell cycle phase distribution. No significant differences in chemosensitivity were observed between transformed and untransformed cell lines to doxorubicin, VP-16, cis-platinum or mitomycin C. Therefore, data suggest that activated Ha-ras oncogenes have no role in sensitivity to these antineoplastic agents.

Animals↗
PubMed1989

Combination antibiotic treatment of chemotherapy-induced neutropenia in non-leukemic patients.

The use of more aggressive chemotherapies in the treatment of patients with some tumors has caused a higher frequency of neutropenia and subsequent serious infections. To verify the role in these patients of a combination therapy of amikacin (300 mg/m2 i.v. every 12 hours) plus ceftazidime (2 g/m2 i.v. every 8 hours) administered as initial empiric treatment, followed in non-responsive cases by a second-line therapy with clindamycin (300 mg/m2 i.v. every 8 hours), we conducted a prospective study in 45 febrile episodes (temperature greater than or equal to 38.5 degrees C) in neutropenic patients (neutrophils less than or equal to 500/ml). The patients' median age was 58 (range, 19-80); 29 were women and 16 were men. The median performance status was 50 (range, 30-90), and 71% of the patients had progressive tumoral disease. Before antibiotic therapy the median duration of fever was 12 hours (range, 4-48 hours). The median granulocyte count was 350/ml (range, 100-500 cells/ml), and the median peak temperature was 38.8 degrees C (range, 38.5-41 degrees C). The median time for neutrophils to rise towards 1000/ml was 4 days (range, 2-12), and the median duration of therapy was 8 days (range, 3-12). Documented bacterial infections were present in 28 patients whereas 17 had clinically possible infections or fever of unknown origin. The infection sites in microbiologically documented infections were: septicemia (12), multiple sites (4), tonsillitis (4), urinary tract (4), pneumonia (2) and fistula (2). Complete response to first-line therapy was obtained in 36 out of 45 episodes (80%; 95% confidence limits from 65% to 90%). Five out of 8 cases responded to second-line therapy with clindamycin for and overall recovery rate of 91%. The amikacin-ceftazidime combination followed by clindamycin in non-responsive cases is effective, with moderate toxicity in non-leukemic febrile neutropenic patients.

Adult↗
PubMed1989

In K562 leukemia cells treated with doxorubicin and hemin, a decrease in c-myc mRNA expression correlates with loss of self-renewal capability but not with erythroid differentiation.

The decrease in c-myc mRNA expression occurring in leukemia cell lines induced to differentiate is supposed to be an early event of the commitment to the differentiation program. Alternatively, the decrease in c-myc mRNA expression could be simply a consequence of loss of the self-renewal capability characteristic of the terminal differentiated phenotypes. In an attempt to clarify these hypotheses, we analysed comparatively the kinetics of variations in c-myc mRNA expression, hemoglobin synthesis, DNA and RNA syntheses, cell cycle kinetics and self-renewal capability in normal and hemin-treated K562 leukemia cells exposed for different periods of time to the antitumoral antibiotic doxorubicin. Times of exposure to doxorubicin were either 2 h, which resulted in reversible induction of hemoglobin synthesis without significant cytostatic effects, or continuously for more than 5 days, which resulted in an irreversible induction of hemoglobin synthesis and in the complete and irreversible loss of self-renewal activity. Comparative analysis of the experimental data indicated that the decrease in c-myc mRNA expression correlated with the loss of replicative activity, possibly due to an irreversible cytostatic effect of the long exposure to doxorubicin, but not with the commitment to the differentiation programs.

Blotting, Northern↗
PubMed1988

Accumulation of DNA strand breaks in cells exposed to methotrexate or N10-propargyl-5,8-dideazafolic acid.

N10-Propargyl-5,8-dideazafolic acid (CB 3717), a new antifolate which directly inhibits thymidylate synthase and which is now under early clinical investigation, was compared with methotrexate (MTX) for its antiproliferative activity and mode of action on M14 human melanoma cell line and NIH/3T3 murine fibroblasts transfected with human c-Ha-ras oncogene (NIH/3T3R). CB 3717 was as active as MTX on both cell lines in inhibiting colony formation, but 20-100 times less potent. After 24 h of exposure both drugs caused an accumulation of cells in the G1 phase of the cell cycle, probably because of inhibition of DNA synthesis and blockage at the G1-S boundary. In NIH/3T3R treated for 16 h with 2 microM MTX or 200 microM CB 3717, we found DNA single-strand breaks amounting to approximately 130 and 140 rad equivalents, respectively, and a considerable number of DNA double-strand breaks, far more than expected if they had been the result of the proximity of single-strand breaks on the two complementary DNA strands. No DNA-protein cross-links were detected. When cells were incubated in drug-free medium for 8 h, there was a further accumulation of single-strand breaks, possibly due to the effects of the drug retained intracellularly as polyglutamyl derivative. Simultaneous treatment with 1.77 microM cycloheximide prevented DNA damage produced by both drugs. Thymidine (10 microM), renewed in the culture medium every 24 h, also prevented DNA damage and cytotoxicity. Since after 16 h treatment with MTX or CB 3717 cells were completely viable, as assessed by [3H]thymidine release, trypan blue exclusion test, and 51Cr release, DNA damage appears to be an early event preceding cell death and may be a feature of the killing ability of the drugs. The involvement of a protein in the formation of DNA breaks is suggested by the fact that when protein synthesis was inhibited with cycloheximide DNA damage was no longer seen.

Cell Cycle↗
PubMed1988

Changes in chemosensitivity of K 562 leukemia cells after induction of erythroid differentiation by hemin.

The human leukemia cell line K 562, when treated with subcytotoxic doses of hemin, undergoes reversible erythroid commitment, as shown by the increased synthesis of hemoglobin. Hemin-treated cells maintain replicative capabilities, although perturbations in cell cycle kinetics are induced. K 562 cells were used to investigate changes in antitumor drug sensitivity as a consequence of cell differentiation induced by hemin treatment. K 562 leukemia cells, cultured in the presence of 20 microM hemin for 12 days, were treated with non-phase-specific (adriamycin, 4-OOH-cyclophosphamide, mitomycin C, bleomycin, cis-diamminedichloro platinum) and phase-specific (vincristine, methotrexate and 5-fluorouracil) antitumor drugs. The results obtained by chemosensitivity tests showed a generalized decrease in chemosensitivity of the K 562 cells to all the drugs tested as a consequence of the hemin-induced differentiation.

Antineoplastic Agents↗
PubMed1987

Combination of amikacin and ceftazidime as empiric treatment of febrile leukopenic patients affected by solid tumors.

A combination of amikacin and ceftazidime was used as initial empiric therapy for the treatment of 25 evaluable febrile episodes (temperature greater than or equal to 38.5 degrees C) in leukopenic adult patients (wbc less than or equal to 1,000/mm3) with solid tumors, characterized by poor prognosis because of low performance status (median Karnofsky score: 50) and progressive disease (76% of cases). Nineteen (76%) of the 25 episodes responded to the initial empiric antibiotic combination. In the microbiologically documented infections, there was no significant difference in the response rate between bacteremia (67%) and localized infections (81%). The response in localized infections caused by gram-negative organisms (81%) was similar to that obtained in gram-positive organisms (82%), whereas gram-positive bacteremia responded better than gram-negative (100 vs 50%). No serious side effects were observed. Reversible nephrotoxicity occurred in 12% and hypokalemia in 20% of the patients treated. This antibiotic combination is a safe and efficacious empiric therapy for infections in leukopenic patients with solid neoplasia.

Adult↗
PubMed1987

Doxorubicin distribution in human breast cancer.

Using a high-performance liquid chromatographic method coupled with fluorimetric detection, we evaluated plasma pharmacokinetics of doxorubicin (DX) and tissue distribution in seven patients suffering from locally advanced breast cancer. Tumor biopsies were performed 30 minutes and 24 hours after DX injection. In addition at 48 hours, during surgery, biopsies were obtained from primary breast cancer, nodes, and other accessible tissues, and DX concentrations were analyzed. A triexponential equation gave the best fit for plasma levels and the values (mean +/- SE) were: elimination half-life, 37.6 +/- 4.9 hours; volume of distribution, 605 +/- 61 L/m2; and clearance 200 +/- 27 ml/min/m2. There was greater interindividual variability in tumor DX concentrations than in plasma concentrations. DX reached much higher (range at 48 hrs, 1.54-14.17 micrograms/g) and longer-lasting concentrations in tumor than in plasma. At 48 hours tumor concentrations were 55.2-337.4 times the plasma concentrations. DX concentrations in normal breast were lower or similar to those in breast carcinoma. DX levels were very low in fat and skin, slightly higher in muscle, and very high in normal or metastasized lymph nodes.

Breast Neoplasms↗
PubMed1986

Effects of 6,6'-dithiodinicotinic acid (CPDS) and its metabolite 6-mercaptonicotinic acid (6-MNA) on murine and hamster fibroblasts (3T3 and BHK) and murine metastatic melanoma cells (F10).

We investigated the action of 6,6'-dithiodinicotinic acid (CPDS) and its metabolite 6-mercaptonicotinic acid (6-MNA) in vitro on murine (3T3) and baby hamster kidney (BHK) fibroblasts and an in vivo highly metastatic subline of murine B16 melanoma (F10). CPDS determined an inhibition of cell growth and a decrease in cell adhesion, while 6-MNA had no effect. When combined with data of the mitotic index and endogenous purine ribonucleotides (on which the drugs seem to have no effect), these observations are conceivable with the hypothesis that the primary target of CPDS is cell membrane.

Cell Adhesion↗