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Biomedical subjects

M D'Incalci

Publications and source records attributed to M D'Incalci.

At least 163 records · Page 9Linked to original sources
PubMed1993

Effects of DNA damaging agents on gene expression in two human cancer cell lines.

In two human cancer cell lines, the breast mcf-7 and the T-cell leukemia MOLT4, we investigated the cytotoxicity of four antineoplastic agents having different mechanisms of action. We selected doxorubicin as a DNA-topoisomerase II inhibitor, FCE24517 (a Distamycin A derivative) as a DNA minor groove binder with specificity for AT bases, melphalan as an alkylating agent and cis-platinum as an alkylating agent able to form DNA-intrastrand crosslinks. From the cytotoxicity experiments a moderately toxic (less than 10% of growth inhibition) and a highly toxic (about 75% growth inhibition) dose were selected to evaluate the expression of genes involved in cell proliferation and in cell response to extracellular insults. The expression was evaluated at early times (60 min.) and 24 hrs. after treatment. At the concentrations utilized in both cell lines we could not find any alteration in the expression of p53, gas-1 and heat shock 70. After melphalan treatment down regulation of c-myc and of the H2A histone was seen at high doses, while no significant alteration of their expression was seen with the other drugs.

Antineoplastic Agents↗
PubMed1993

DNA-topoisomerase inhibitors.

The topology of DNA is regulated by DNA-topoisomerase enzymes, which induce either transient DNA single-strand breaks (topoisomerase I) or DNA double-strand breaks (topoisomerase II). The action of several anticancer drugs, eg, DNA intercalating agents (ie, anthracyclines, anthracenediones, anthrapyrazoles, amsacrines, and ellipticines) and epipodophyllotoxins, appears to be mediated by the enzyme topoisomerase II alpha. The action of camptothecins is mediated by topoisomerase I. All of these drugs cause the induction of DNA enzyme complexes. Some new topoisomerase inhibitors have instead the ability to inhibit the catalytic activity of the enzyme without inducing the formation of complexes. Inhibition of transcription and DNA replication have been implicated as the most likely mechanisms of cytotoxicity. The drugs stimulate DNA cleavage with a certain degree of sequence specificity, which is typical for each drug or class of drugs. The differences in the location of the cleavage sites may explain the different pharmacologic effects of the various topoisomerase inhibitors. Cellular resistance to topoisomerase inhibitors is due to decreased intracellular drug retention (eg, overexpression of P-170), to a decreased level of topoisomerase enzymes, or to mutations that reduce the drug sensitivity of the enzymes. Synergistic activity of the combination of topoisomerase I and topoisomerase II inhibitors or of topoisomerase inhibitors and radiotherapy has been found to be highly dependent on the sequence used.

Animals↗
PubMed1992

Apoptosis. Biochemical events and relevance to cancer chemotherapy.

Two distinct pathways for cell death exist. Compared to necrotic death, physiological or apoptotic cell death is an active suicidal process that consists of a cascade of well-regulated synthetic events. Participation of specific genes in apoptosis, and its possible molecular regulation, are considered in order to investigate the mechanism of cell death induced by some cancer chemotherapeutic agents.

Animals↗
PubMed1992

Expression of E. coli tag gene encoding 3-methyladenine glycosylase I in NIH-3T3 murine fibroblasts.

NIH-3T3 fibroblasts were co-transfected with pSV2neo and pSG5tag by the calcium-phosphate precipitation method. The stable integration of the tag gene sequence and its transcription was verified by Southern and Northern blot analysis. 3-Methyladenine glycosylase activity in pSG5tag transfected 3T3 cells was approximately 400 times higher than in cells transfected with the control plasmid pSG5 or in the parental cells and was inhibited by 3-methyladenine. Bacterial tag gene can thus be expressed in mammalian cells and the encoded enzyme is functionally active. These transfected cells could serve as an important tool to investigate the importance of the repair of N3-adenine as a mechanism of protection against the mutagenicity and cytotoxicity of alkylating agents.

3T3 Cells↗
PubMed1992

Activity of aphidicolin glycinate alone or in combination with cisplatin in a murine ovarian tumor resistant to cisplatin.

Aphidicolin, a reversible inhibitor of DNA polymerase alpha and delta, has recently been reported to reverse the resistance to cisplatin (DDP) of an ovarian cancer cell line. We investigated the pharmacokinetics of aphidicolin in mice and examined its activity either alone or in combination with DDP in the DDP-sensitive M5076 (M5) murine reticular cell sarcoma as well as in a DDP-resistant subline (M5/DDP). The drug was cleared from plasma very rapidly (clearance, 41.6 ml min-1 kg-1), showing a half-life of 15 min. Aphidicolin concentrations in the tumor were approximately 50% of those found in plasma at steady state. Using several dose schedules and continuous infusions we failed to detect significant antitumor activity for aphidicolin glycinate. Potentiation of the activity of DDP by aphidicolin glycinate was moderate in mice bearing M5 tumor as well as in those bearing M5/DDP tumor. These data do not support the possible clinical use of aphidicolin in combination with DDP. However, further studies should be carried out in different tumor models before this possibility is conclusively ruled out.

Animals↗
PubMed1992

O6-methylguanine-DNA methyltransferase activity and induction of novel immunogenicity in murine tumor cells treated with methylating agents.

To investigate the mechanism of the generation of immunogenic tumor variants by mutagenic drugs, murine leukemia cells exhibiting different sensitivity to killing by the alkylator 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and different ability to repair O6-methyl-guanine in their DNA were treated in vitro with a series of methylating agents, including triazene derivatives, temozolomide, and streptozotocin. At the population level, we found that BCNU-resistant cells (L1210/BCNU) that appeared to be cross-resistant to killing by a dimethyltriazene and expressed high levels of O6-methylguanine-DNA methyltransferase activity (mer+ phenotype) failed to generate highly immunogenic variant sublines on repeated exposure to the methylating agents. In contrast, all cells (L1210) that were susceptible to DNA alkylation damage and deficient in O6-methylguanine repair (mer-) developed immunogenic variant sublines. A noticeable exception was represented by streptozotocin treatment, which was equally effective in mer+ and mer- cells. At the clonal level, a single exposure to streptozotocin or a triazene derivative resulted in a high incidence (33% and 50%, respectively) of immunogenic cell generation in mer- cells only. In mer+ cells, streptozotocin treatment led to a 33% incidence of immunogenic clones only when the cells were concurrently exposed to O6-methylguanine as a free base. The activity of O6-methylguanine-DNA methyltransferase in mer+ cells was greatly reduced by treatment with O6-methylguanine or streptozotocin, and the combination of the two drugs led to enzyme levels similar to those observed in mer- cells. Taken together, these data suggest that the mechanism of O6-alkylation may be operative in the induction of novel tumor-cell antigenicity by methylating agents.

Alkylating Agents↗
PubMed1992

Do anticancer agents reach the tumor target in the human brain?

The development of effective chemotherapy for tumors of the central nervous system (CNS) is complicated in that the blood-brain barrier (BBB) hampers the penetration of most drugs into the brain and cerebrospinal fluid (CSF). This review summarizes the main reports on the distribution to CNS tumors and peritumoral normal brain of antitumor agents such as epipodophyllotoxins, cis-diamminedichloroplatinum(II), some nitrosoureas, bleomycin, vinblastine, and other clinically used antitumor agents as well as that of some experimental compounds with specific physicochemical properties. Drug levels were measured at surgical resection or in autopsy samples taken from patients who presented with different primary brain tumors or with brain metastases from extracerebral tumors. The observations made in each study were summarized in some detail, and the main points were then evaluated comparatively so as to highlight common aspects in the pharmacokinetic patterns of antitumor agents in human CNS tumors. Independently of their physicochemical properties, most antitumor agents appear to accumulate to a greater extent and to persist longer in intracerebral tumors than in the normal peritumoral brain. From in vitro cytotoxicity assays, it appears that epipodophyllotoxins, platinum compounds, bleomycin, and nitrosoureas reach potentially active therapeutic concentrations at the tumor target. However, all drugs have difficulty in reaching brain tissue adjacent to the tumor, as the intact BBB hampers their penetration. Plasma and CSF drug concentrations usually give little useful indication of the absolute quantity of drugs in brain tumors. To obtain a clear understanding of the CNS distribution of antitumor agents, one must determine whether the compound being measured is actually responsible for the observed activity and must consider the role of metabolites in the effect of the parent drug.

Antineoplastic Agents↗
PubMed1992

O6-Alkylguanine-DNA alkyltransferase content in synchronised human cancer cells.

The DNA repair enzyme O6-alkylguanine-DNA alkyltransferase (AT) was analysed in the human ovarian-cancer SW626 cell line and in the human promonocytic leukemia U937 cell line following their synchronisation with low non-toxic concentrations of methotrexate. In SW626, AT increased in the early S phase of the cell cycle and then declined during progression of the S phase to levels found in the G1 phase of unsynchronised cells. In contrast, at the G1/S-phase boundary and in the S phase, U937 cells showed a lower AT content than did exponentially growing unsynchronised cells. In addition, AT activity was greatly reduced in resting U937 cells but was not reduced appreciably in resting SW937 cells but was not reduced appreciably in resting SW626 cells. The results of these studies indicate that AT fluctuations do not follow a constant pattern during the cell cycle of different cell lines.

Cell Cycle↗
PubMed1992

Flow cytometric analysis of multidrug-resistance-associated antigen (P-glycoprotein) and DNA ploidy in human colon cancer.

In many cell systems, resistance to cytotoxic drugs is acquired by the amplification and/or overexpression of the multidrug resistance (mdr) gene, which codes for the glycoprotein, p170 (P-glycoprotein). Moreover, in a variety of malignant tumours there is increasing evidence of the relationship between the DNA ploidy pattern of patients and their prognosis. In this study we aimed to evaluate these two potential indicators of constitutive drug resistance in human colorectal tumours. We employed a method to quantify simultaneously, on a per cell basis, mdr gene expression (using the C219 monoclonal antibody for P-glycoprotein) and nuclear DNA content with high-resolution bivariate flow cytometry. The study was performed on a human colon-carcinoma-derived cell line (LoVo) and its doxorubicin-resistant variant (LoVo/Dx) and on tumour samples and adjacent normal mucosa from 35 untreated patients with colon cancer. The P-glycoprotein was found in both LoVo and LoVo/Dx cells with levels slightly lower in the parental than in the resistant subline (P, NS). A multi-drug-resistant specific probe for mRNA expression and Western blot assay confirmed the specificity of p170 expression. All of the colon cancer with unimodal diploid DNA distribution and all the normal colonic mucosa samples showed P-glycoprotein expression, without a statistically significant difference in median values between tumours and normal samples. Tumours with bimodal DNA distribution showed median values of P-glycoprotein expression of their hyperdiploid cell clones significantly higher than those of their diploid clones and of the tumours with unimodal DNA distribution (P less than 0.005). Our results show the feasibility of bivariate flow-cytometric analysis of P-glycoprotein expression and DNA content on clinical material and support the hypothesis that the MDR phenotype and DNA ploidy together may influence the biological behaviour of colon cancer in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Chinese hamster ovary cells deficient or proficient in O6-alkylguanine-DNA alkyltransferase activity are equally sensitive to X-rays.

In mammalian cells, under aerobic conditions, ionizing radiations and radiomimetic chemical agents can induce an enzymatic activity involved in DNA repair, O6-alkylguanine-DNA alkyltransferase (O6-AT). This catalytic protein is active against alkyl-radical-induced DNA damages. This induction was proposed to be linked to the formation of hydroxyl radicals. The possible involvement of O6-AT in the defense mechanism of the cell against aerobic radiation damage was investigated by comparing the X-ray sensitivity of two Chinese hamster ovary (CHO) cell lines, the first deficient (CHO mex-) and the second proficient by transfection of O6-AT (CHO mex+). The colony-forming ability after X-irradiation was appreciably reduced in CHO mex- in comparison to CHO mex+ cells. Nevertheless, pretreatment of proficient cells with O6-methylguanine, a specific inhibitor of O6-AT, reduced the DNA repair activity but did not modify the degree of sensitivity to X-rays of the CHO mex+ cells. Since the glutathione concentrations as well as the DNA damage amounts induced by X-irradiation were comparable in the variously treated cell lines, these results suggest that the observed induction of O6-AT by ionizing radiation in aerobic conditions could be a generalized rather than a specific response to damage by radicals.

Alkylation↗
PubMed1992

The unique interaction with immunity of FCE 24517, an antitumor drug with a novel mode of action.

The present study was designed to characterize in mice the effects on the immune system of the antineoplastic agent FCE 24517, a benzoic acid mustard derivative of distamycin A with specificity for AT-rich base pair sequences of beta-DNA. At antitumorally therapeutic doses, single injections of FCE 24517 caused profound leukopenia and a decrease of spleen cell numbers. However, primary and secondary antibody production to the T-dependent antigen sheep red blood cells were markedly increased by FCE 24517 given before or together with antigen. Antibody production to the T-independent antigen type III pneumococcal polysaccharide was not appreciably affected by FCE 24517. The delayed type hypersensitivity response to sheep erythrocytes was only marginally decreased, whereas proliferation of spleen cells to mitogens was markedly depressed. The ability of natural killer cells and macrophages to mediate cytotoxicity was not affected by FCE 24517 treatment. The ability of carrier-primed cells from drug-treated mice to cooperate for anti-trinitrophenyl antibody production increased twofold over that of vehicle-injected controls, suggesting an increase in T-helper cell activity. Serum cytokine levels were studied in mice injected with bacterial lipopolysaccharide used as a model stimulus. Peak levels of TNF and IL-6 were not modified by FCE 24517, but at later times higher amounts of cytokines were found in drug-treated mice compared with the control, suggesting a longer exposure of immunocompetent cells to these factors. Two compounds (FCE 24561 and CC-1065), also capable of binding AT-rich sequences in the minor groove of beta-DNA and containing an alkylating moiety, had immunomodulatory activity similar to FCE 24517 in increasing primary anti-sheep erythrocytes response. It is concluded that FCE 24517 exhibits a unique interaction with the immune system, markedly different from that of alkylating agents and may be representative of a novel group of antiproliferative-immunomodulating agents.

Animals↗
PubMed1992

DNA damage induced by alachlor after in vitro activation by rat hepatocytes.

We investigated the ability of alachlor to cause DNA damage by measuring single-strand breaks (SSB) in DNA, after metabolic activation by freshly isolated rat hepatocytes. Incubation of different concentrations of alachlor with rat hepatocytes led to numerous metabolites. The majority, isolated and identified by GC-MS analysis, were products arising from reactions catalyzed by the P-450 monooxygenase system, arylamidase and flavin mixed-function oxidase/cytochrome P-450 monooxygenase. The results, using freshly isolated rat hepatocytes, showed that in these conditions several potentially DNA damaging metabolites were produced; this experimental condition was used to assess DNA damage induced by the mixture of alachlor and its metabolites. The alkaline elution technique showed that at 200 microM and more clearly at 400 microM there were some small fragments that eluted in the first fraction. This fragmentation was probably due to alachlor cytotoxicity. In addition to the small DNA fragments eluting in the first fraction there were other larger DNA fragments. These DNA-SSB were most evident at the alachlor concentration of 400 microM, but also at 200 microM and 100 microM, whereas at 10 microM the DNA elution rate appeared comparable to that of controls. The results suggest that some unstable and DNA-reactive metabolites might interact with DNA causing SSB and such interaction might be important in relation to the mechanism of alachlor-induced DNA damage. However, it may not be possible to clarify whether SSB are the result of direct DNA interaction of the compound or of secondary cellular processes after chemical treatment.

Acetamides↗
PubMed1992

Potentiation of etoposide cytotoxicity against a human ovarian cancer cell line by pretreatment with non-toxic concentrations of methotrexate or aphidicolin.

Exposure of human ovarian cancer SW626 cell line to 0.08 mumol/l methotrexate or 25 mumol/l aphidicolin for 24 h caused no cytotoxicity but enhanced etoposide cytotoxicity. Methotrexate or aphidicolin treatment induced a reversible blockade at the beginning of S phase which was reversed upon drug removal with a consequent wave of synchronisation. The enhancement of etoposide cytotoxicity was not due to higher etoposide intracellular uptake in the methotrexate or aphidicolin-pretreated cells. The topoisomerase II content in methotrexate or aphidicolin pretreated SW626 cells was higher than in control cells assessed by western blotting or flow cytometry. The higher etoposide cytotoxicity observed after synchronization with methotrexate or aphidicolin was apparently unrelated to the number of drug-induced DNA-topoisomerase II complexes evaluated as DNA double strand breaks or DNA-protein crosslinks. These data support the view that etoposide-induced DNA-topoisomerase II complexes are more cytotoxic in cells which are in S-phase.

Aphidicolin↗
PubMed1992

Sequential administration of dacarbazine and fotemustine in patients with disseminated malignant melanoma--an effective combination with unexpected toxicity.

Resistance to alkylating agents is partly due to the presence of the DNA repair enzyme, termed O6 alkyltransferase (O6AT). Preclinical evidence of the transient restoration of sensitivity of cells resistant to nitrosoureas by pretreatment with a methylating agent, whose role is to deplete cells of O6AT activity and clinical evidence of such a depletion in patients lymphocytes, led us to test the sequential administration of dacarbazine 3 h prior to fotemustine, a chloroethylnitrosourea derivative. 24 patients with measurable advanced melanoma entered the trial and are evaluable. Toxicity was mainly haematological with early neutropenia and/or thrombocytopenia. Clinical activity (33%) was impressive especially on lung metastases with high complete response rate for that site (7/14). Unfortunately, the occurrence of a rapidly fatal pulmonary toxicity precludes further use of the regimen before a plausible explanation for this unexpected toxicity is obtained. Indeed, similar cases have been reported in other trials using the sequential schedule while no lung toxicity was reported in single agent or alternated administrations. Preclinical studies are ongoing to test the hypothesis of a glutathione depletion and the possibility of a rescue treatment.

Adult↗
PubMed1992

O6-alkylguanine DNA alkyltransferase is induced by human recombinant interferon-alpha A/D in mouse liver.

Treatment of C57Bl or BALB/C mice with human interferon-alpha A/D (HuIFN-alpha A/D) significantly increased hepatic levels of the DNA repair enzyme O6-alkylguanine DNA alkyltransferase (AT). The maximum induction was seen 24 h after a single dose of 50-100 micrograms/kg IFN-alpha A/D. No induction was observed in rat liver hepatocytes cultured in vitro. Liver AT was also induced by poly(I:C), which is a potent IFN inducer. By increasing AT levels, IFN could protect against the potentially mutagenic alkylation at guanine O6 position caused by some carcinogens. Moreover this finding suggests a link between immune response and the DNA repair system, possibly acting in concert to defend the body from potentially toxic compounds.

Animals↗
PubMed1992

Antitumor activity of 1,4-bis (2'-chloroethyl)-1,4-diazabicyclo-[2.2.1] heptane dimaleate (Dabis Maleate) in M5076 and its subline resistant to cyclophosphamide M5/CTX.

We investigated the antitumoral activity of Dabis Maleate given on different dosage schedules and as continuous infusion in a murine reticular cell sarcoma M5076 (M5) and in a subline made resistant to cyclophosphamide and other nitrogen mustards (M5/CTX). The therapeutic index of Dabis Maleate was clearly better when the drug was given as a continuous 72-h infusion. Dabis Maleate appeared non-cross-resistant to cyclophosphamide and this property renders it interesting for further clinical development.

Animals↗
PubMed1992

Influence of O6-methylguanine on DNA damage and cytotoxicity of temozolomide in L1210 mouse leukemia sensitive and resistant to chloroethylnitrosoureas.

Temozolomide is a new anticancer agent which in the early clinical investigation has shown promising antitumor activity. It decomposes spontaneously to the active metabolite of DTIC (MTIC). Temozolomide is more cytotoxic against L1210 than against a subline L1210/BCNU, resistant to chloroethylnitrosoureas. Using [methyl-3H] temozolomide we found that after 1 h exposure the amount of O6-methylguanine (O6mGua) was twice as high in L1210 than in L1210/BCNU whereas the amount of N7 mGua was approximately the same in the two cell lines. O6-alkylguanine DNA alkyltransferase (AT) levels were higher in L1210/BCNU than in L1210, supporting the view that the resistance to methyltriazenes is probably related to the efficient repair of O6mGua in L1210/BCNU. Exposure of L1210/BCNU cells to 0.4 mM O6mGua for 24 h resulted in a depletion of AT and in a higher temozolomide-induced cytotoxicity. In the sensitive cell line L1210, temozolomide activity was not potentiated by O6mGua pretreatment. Moreover, in L1210/BCNU, O6mGua increased DNA single-strand breaks caused by temozolomide, suggesting that O6-guanine alkylation induces an excision repair mechanism in cells depleted in AT.

Alkalies↗