Biomedical subjects

C Geroni

Publications and source records attributed to C Geroni.

At least 37 records · Page 2Linked to original sources

PubMed1997

Synthesis, solvolytic stability and cytotoxicity of a modified derivative of CPzI, a pyrazole analog of the alkylation subunit of the antitumor agent CC-1065: effect of the nitrogen substitution on the functional reactivity.

The synthesis and the comparative preliminary biological evaluation of a new pyrazole analog (16) of the CC-1065 alkylating unit (CPI) are described. This new derivative showed low cytotoxicity against L1210 murine leukemia (IC50 3064 nM) with respect to reference compound, but contrarily to literature data, was found to be more stable to solvolysis than the natural derivative (+/-)-N-Boc-CPI (pH 3, t1/2 = 212 h vs. 37 h). The results of such investigation showed that alkylation of the pyrazole nitrogen caused a loss of cytotoxic activity in vitro against tumor cells. This experimental observation allowed us to confirm the importance of free N-H for the anticellular activity.

Alkylation↗

PubMed1995

Decreased tyrosine phosphorylation in tumour cells resistant to FCE 24517 (tallimustine).

Resistance to FCE 24517 is not related to the emergence of any of the most frequently observed phenotypes. We have found that two resistant cell lines (L1210/24517 murine leukaemia and LoVo/24517 human colon adenocarcinoma) present congenital modifications in tyrosyl phosphatase and kinase activities. Moreover, the cytotoxic activity of FCE 24517 is increased in combination with a tyrosine phosphatase inhibitor and decreased in combination with protein kinase inhibitors, this being in agreement with the hypothesis that the activity of this drug is strictly dependent on the presence of tyrosine phosphorylated protein(s).

Adenocarcinoma↗

PubMed1995

Sequence-specific DNA interactions by novel alkylating anthracycline derivatives.

New alkylating anthracycline derivatives with promising antitumor activity have been synthesized. We selected two of these compounds, 4-demethoxy-N,N-bis(2 chloroethyl)-4'-methylsulfonyl-daunorubicin (FCE 27726) and 4-demethoxy-3'-deamino-3'aziridinyl-4'-methylsulfonyl daunorubicin (FCE 28729), comparing their interaction with DNA and that of the non-alkylating derivative 4-demethoxy-4'-methylsulfonyl-daunorubicin (FCE 27894). The two alkylating derivatives were more cytotoxic than idarubicin and presented low cross-resistance with doxorubicin. Both FCE 27726 and FCE 28729 were found to alkylate guanines at the N7 position in the major groove with roughly the same specificity, but at different concentrations. FCE 27726 was 10 times more potent than FCE 28729 in alkylating DNA. At higher concentrations, FCE 27726 was able to alkylate adenines, possibly at the N3 position contained in a sequence 5'-PyAA. FCE 27726, as expected, was able to form DNA interstrand cross-links either in vitro and in vivo in treated cells. FCE 28729 did not form DNA interstrand cross-links in vivo. In vitro, at high concentrations, some DNA interstrand cross-links were evident. The non-alkylating derivative FCE 27894 did not produce any alkylation or DNA interstrand cross-links either in vitro or in vivo.

Animals↗

PubMed1994

L1210 cells selected for resistance to methoxymorpholinyl doxorubicin appear specifically resistant to this class of morpholinyl derivatives.

We investigated the mechanism of resistance in murine L1210 leukaemia cells selected after treatment with FCE 23762 methoxymorpholinyl doxorubicin: (MMRDX), a methoxymorpholinyl derivative of doxorubicin active in vitro and in vivo on multidrug-resistant (mdr) cells, currently undergoing phase I clinical trials. The resistant subline obtained after repeated in vitro treatments, L1210/MMRDX, is resistant in vitro and in vivo to all tested methoxymorpholinyl derivatives and to cyanomorpholinyl doxorubicin, but shows resistance to morpholinyl derivatives only in vivo or following their activation with rat S9-liver fractions in vitro. L1210/MMRDX cells are sensitive to classic mdr- and altered topoisomerase (AT)-mdr-associated drugs. These cells do not appear to overexpress the mdr1 gene, nor do they exhibit impaired intracellular drug accumulation and efflux or altered levels of glutathione and glutathione S-transferase. The extent of DNA single-strand break formation and, after microsomal activation, of DNA interstrand cross-links after treatment with MMRDX was similar in the parent and the resistant subline. The mechanism of resistance in L1210/MMRDX cells remains to be identified but may prove a novel one, highly specific for this class of mdr-active anthracyclines.

Animals↗

PubMed1993

Intracellular glutathione heterogeneity in L1210 murine leukemia sublines made resistant to DNA-interacting anti-neoplastic agents.

Intracellular glutathione (GSH) content was measured by flow cytometry using monochlorobimane (mBCl) and by the enzymatic assay in a set of 6 sublines of murine L1210 leukemia cells made resistant to DNA-interacting agents having distinct mechanisms of action: L-phenylalanine mustard (L-PAM), 1,3-bis(2-chloroethyl)-I-nitrosourea (BCNU), cisplatin (DDP), N-deformyl-N-(4-N,N-bis(2-chloroethylamino) benzoyl) distamycin A (FCE 24517), doxorubicin (DX) and 3'-deamino-3' (2-methoxy-4-morpholinyl)-doxorubicin (FCE 23762). A significant correlation was demonstrated between the mean intracellular mBCl fluorescence values measured by flow cytometry and levels of GSH measured by the classical enzymatic assay, despite the possible influence of glutathione-S-transferases and of other thiols on the mBCl fluorescence. Although less specific, the flow cytometric method is more informative than the enzymatic assay, allowing detection of fluorescence distributions, which we proved to be characteristic of each subline. In order to assess a procedure enabling a quantitative analysis to be made of intercellular GSH heterogeneity, we propose the use of appropriate thresholds and parameters of the mBCl flow cytometric distribution. By use of this analysis procedure, distinct types of alterations, with respect to the heterogeneity distribution of the parental L1210 cell line, have been evidenced in resistant cells. A uniform increase in mBCl fluorescence was observed among cells of the sublines resistant to L-PAM and FCE-24517. The mean mBCl fluorescence increase in sublines resistant to DX and DDP was due to a higher number of cells with fairly high mBCl fluorescence, but still within the range spanned by the parental cell line. A less heterogeneous mBCl fluorescence distribution was found in the L1210 subline resistant to FCE 23762, which was, however, similar to a cloned sensitive line. Though GSH was linked to the principal cause of drug resistance only in the L-PAM-resistant cell line, alterations in heterogeneity, as detected by mBCl fluorescence distributions, were found in 5 out of 6 resistant lines.

Animals↗

PubMed1993

Establishment of L1210 leukemia cells resistant to the distamycin-A derivative (FCE 24517): characterization and cross-resistance studies.

N-deformyl-N-[4-N,N-bis(2-chloroethylamino)benzoyl] distamycin-A (FCE 24517) is a new cytotoxic anti-tumor agent in phase-1 clinical trials. We have isolated stable FCE-24517-resistant cell sublines from murine leukemia L1210 cells by in vitro exposure to the drug. FCE 24517 selects a mixed population of resistant cells: the L1210/24517(1) cell line in vitro was in fact resistant to the selecting agent (RI 48.3), as well as to L-PAM (RI 5.4) and DX (RI 8.6) and over-expressed the mdr-I gene. When L1210/24517(1) cells were implanted in vivo and evaluated for sensitivity to the same agents, resistance was observed only to FCE 24517 and partially to L-PAM, whereas DX had the same anti-tumor efficacy as on the sensitive line. The clone derived from the above subline (L1210/24517(2)) was resistant to FCE 24517, distamycin-A and other cytotoxic compounds bearing the distamycin-A skeleton, and fully sensitive to DX and other anti-tumor compounds involved in the multi-drug resistance mechanisms, with a complete disappearance of the mdr phenotype. L1210/24517(2) cell line is partially cross-resistant to L-PAM, this resistance being accounted for by higher GSH intracellular levels, which however do not influence the resistance to FCE 24517. In fact, BSO treatment was capable of significantly modifying only the cytotoxicity of L-PAM. Our data suggest that L1210/24517(2) cells present a mechanism of resistance specific for FCE 24517 and related molecules.

Animals↗

PubMed1991

Selective DNA interaction of the novel distamycin derivative FCE 24517.

N-Deformyl-N-(4-N-N,N-bis(2-chloroethylamino)benzoyl)distamy cin A (FCE 24517) is a novel cytotoxic and antitumor agent shortly to be investigated in phase I clinical trials. It was equally effective in inhibiting the growth of the murine L1210 line and of a subline (L1210/PAM) resistant to nitrogen mustards, whereas distamycin A was virtually inactive. The cellular uptake and retention of FCE 24517 and distamycin A were similar, thus excluding the possibility that this marked variation in cytotoxic activity was due to different intracellular concentrations of the two compounds. FCE 24517 did not appear to act as an inhibitor of macromolecule synthesis. As shown by radioactively labeled precursor incorporation only 24 h after drug treatment a significant inhibition of DNA synthesis was observed in L1210 or in L1210/PAM, when a marked proportion of cells was arrested in premitotic phase. FCE 24517 did not cause DNA breaks, DNA interstrand cross-links, or DNA-protein cross-links in L1210 cells exposed to active drug concentrations. A very low amount of radioactivity was found to be bound irreversibly to DNA in L1210 cells exposed for 1 h to [14C]FCE 24517. Using plasmid pBr322 DNA fragments in a modified version of the Maxam and Gilbert DNA sequencing technique we found no detectable binding of FCE 24517 to N-7-guanine (the major site of alkylation for classical alkylating agents), whereas some alkylations to adenine (presumably to N-3-adenine) were demonstrated. Thus it appears that FCE 24517 is a novel antitumor agent with a mode of action different from that of the drugs currently used in the clinic. In summary it is suggested that FCE 24517 acts by causing a few selective alkylations to adenines in the minor groove of DNA, although the precise base sequence necessary has yet to be elucidated.

Alkylating Agents↗

PubMed1991

Influence of lipophilicity on cytotoxicity of anthracyclines in LoVo and LoVo/Dx human cell lines.

Quantitative structure-activity relationship studies aimed at improving drug activity profiles require the determination of the physicochemical properties possibly involved in biological action. The lipophilic character of selected anthracyclines has been measured by means of reverse-phase high performance liquid chromatography, selecting appropriate experimental conditions. The capacity coefficients at zero percentage of the organic phase (log K0), which are retention indexes, have been used as lipophilicity descriptors in a QSAR study, involving as biological data the cytotoxicity of anthracyclines in a doxorubicin-sensitive (LoVo) and in a doxorubicin-resistant (LoVo/Dx) human cell lines. The results obtained in these in vitro models indicate that lipophilicity plays a role in anthracycline activity, influencing drug availability at the site of action.

Antibiotics, Antineoplastic↗

PubMed1990

Comparative effects of doxorubicin and 4'-epi-doxorubicin on nucleic acid metabolism and cytotoxicity in a human tumor cell line.

The effects of 4'-epi-doxorubicin (4'E-Dx) and doxorubicin (Dx) on cell survival were investigated after treatments for 1 or 24 h. It was found that after short-term exposure, 4'E-Dx causes a higher level of killing than Dx, whereas a similar cytotoxic response is detectable after 24 h. Under the same experimental conditions (treatment for 1 or 24 h) at equimolar concentrations, the two anthracyclines were equally inhibitory to DNA or RNA synthesis. Both the degree and the rate of induction of DNA strand breakage over a 1-h drug exposure were higher for 4'E-Dx than for Dx. These data were related to results of experiments carried out to investigate the rates of uptake and egress of the anthracyclines. From this study we concluded that no relationship can be established between the cytotoxicity of 4'E-Dx and Dx and their ability to inhibit DNA and RNA synthesis. In addition, the different DNA-damaging action of the two drugs does not appear to be solely dependent on the different rates of cellular uptake.

Cell Survival↗

PubMed1990

New biosynthetic anthracyclines related to barminomycins incorporating barbiturates in their moiety.

Three new anthracyclines, FCE 21424 (2), FCE 24366 (3) and FCE 24367 (4), were isolated from culture broths of Streptomyces peucetius and its mutant strains after addition of sodium barbiturates during the fermentation. Structural assignment, achieved through spectroscopic and degradative studies, that the new anthracyclines had a common barminomycin-like structure incorporating different barbiturate moieties. The new anthracyclines were found to display outstanding cytotoxicity and remarkable potency "in vivo" against P388 ascitic leukemia.

Animals↗

PubMed1989

Comparison of intracellular drug retention, DNA damage and cytotoxicity of derivatives of doxorubicin and daunorubicin in a human colon adenocarcinoma cell line (LoVo).

Formation of DNA single strand breaks (SSB) was assayed by alkaline elution in LoVo cells treated with doxorubicin, daunorubicin and six derivatives of these drugs modified either in the chromophore or the sugar. Seven compounds showed a biphasic relationship (initial increase and then a decrease) for the formation of DNA-SSB over the concentration range 0.05-10 micrograms/ml. At a drug concentration in the range causing an increase of DNA damage very fast repair of DNA-SSB was observed for 4'-deoxydoxorubicin and 4-demethoxydaunorubicin; the kinetics of DNA-SSB investigated after drug removal at a drug concentration reducing DNA-SSB showed a time dependent increase of DNA damage for both drugs although with different patterns. 4'-Deoxydoxorubicin reduced the effect of radiations on the rate of elution of DNA in a way resembling the formation of DNA interstrand cross links (ISC) at concentrations at which DNA-SSB were reduced. DNA-ISC were not produced by chemical reactions occurring during sample processing for alkaline elution and this derivative was not metabolized by LoVo cells. The IC50 of the anthracyclines were on a several log range, though for most of the derivatives the cytotoxicity curve showed a plateau at growth inhibition of about 15-30% at increasing intracellular drug levels. A relationship between DNA damage and cytotoxicity was observed only in a very small range of DNA-SSB. It is likely that the different effects of these anthracyclines on the formation of DNA-SSB depend on a qualitatively different interaction between drug-DNA and topoisomerase II when the drug concentration is raised.

Adenocarcinoma↗

PubMed1989

Cellular and molecular pharmacology of 4'-epidoxorubicin in HeLa cells. Comparison with its parent drug, doxorubicin.

The effects on cellular DNA and cytotoxicity produced by doxorubicin (Dx) and its epimer 4'-epidoxorubicin (4'E-Dx) were investigated in cultured HeLa cells. 4'E-Dx was 2.3 times more cytotoxic than Dx after 1 h of treatment, but the two anthracyclines were equally cytotoxic on longer-term (24 h) drug exposure. The different kinetics of cell lethality were related to pharmacodynamic differences between the two drugs. In fact, cellular uptake and efflux rates of 4'E-Dx were faster than those of Dx on 1 h of drug exposure but similar after 24 h of treatment. 4'E-Dx caused more protein-concealed strand breaks in DNA (single and double) than did Dx, despite a lower potency for free-radical formation. The degree of strand breakage by 4'E-Dx was not a linear function of exposure time and, in fact, the rate of strand-break induction declined continuously with time. In contrast, Dx caused an almost linear increase in DNA single-strand breaks with time during 1 h of drug exposure; this was apparently due to its slower uptake. There was little repair of the DNA single-strand breaks produced by Dx upon postincubation for 5 h in a drug-free medium, whereas DNA lesions caused by 4'E-Dx were removed with a t1/2 of about 1.7 h. These findings underline the importance of the cellular pharmacokinetics of anthracyclines in relation to their cytotoxic and DNA-damaging effects.

DNA Damage↗

PubMed1989

Synthesis, DNA-binding properties, and antitumor activity of novel distamycin derivatives.

A group of potential alkylating agents have been synthesized that are structurally related to the oligopeptide antiviral antibiotic distamycin. All derivatives form complexes with native calf-thymus DNA but compounds 2, 3, and 6 give rise to covalent adducts. Cytostatic activity against both human and murine tumor cell lines in vitro is displayed by the new compounds. Compounds 3 and 4 are active on melphalan-resistant L1210 leukemia in mice.

Alkylating Agents↗

PubMed1988

Intracellular doxorubicin concentrations and drug-induced DNA damage in a human colon adenocarcinoma cell line and in a drug-resistant subline.

The mechanisms of resistance to doxorubicin (DX) were investigated using a human colon adenocarcinoma cell line (LoVo) and a subline approximately 30 times less sensitive to doxorubicin. LoVo and LoVo/DX were similar in terms of DNA and protein content, cell volume, duration of S phase and the generation time, and proportion of cycling cells. LoVo/DX showed cross-resistance to other anthracyclines, to vinca alkaloids, epipodophyllotoxin derivatives, 4'-(9-acridinylamino-methanesulfon-m-aniside) and actinomycin D. LoVo/DX was equally sensitive to melphalan and showed collateral sensitivity to cis-platinum and 1-beta-D-arabinofuranosylcytosine. On exposing LoVo and LoVo/DX to 1.25 and 40 micrograms/ml DX respectively, for 4 hr, similar DX intracellular concentrations were reached in the two cell lines. In these treatment conditions protein associated DNA-single strand breaks or DNA-double strand breaks, assessed by alkaline elution methods were only slightly less in LoVo/DX than in LoVo cells. In LoVo/DX cells, however, DNA breaks disappeared very quickly after drug removal whereas they persisted longer in LoVo cells. This persistance is probably related to the much slower DX efflux from LoVo than LoVo/DX. When verapamil was combined with DX it inhibited the rapid DX efflux from LoVo/DX and reversed the resistance in this cell line, but it had no significant activity on LoVo cells. Verapamil also increased DX-induced DNA-single strand breaks and DNA-double strand breaks in LoVo/DX cells, but not in LoVo cells.

Adenocarcinoma↗

PubMed1988

Adenosine deaminase inhibitors. Synthesis and biological activity of deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine.

Two new deaza analogues of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, 1), 7-deaza-EHNA (6) and 1,3-dideaza-EHNA (11), were synthesized and evaluated for adenosine deaminase (ADA) inhibitory activity and compared with EHNA, 1-deaza-EHNA (2), and 3-deaza-EHNA (3). Substitution of a methine group for a nitrogen atom in the 7-position of the purine moiety of EHNA produces a dramatic drop in the inhibitory activity (Ki = 4 X 10(-4) M) whereas compounds 2 and 3 are still good inhibitors (Ki = 1.2 X 10(-7) M and 6.3 X 10(-9) M respectively). EHNA and its deaza analogues so far synthesized were also tested in vitro for their antiviral and antitumor activity in a range of cellular systems. EHNA and 1-deaza-EHNA are equiactive as inhibitors of human respiratory syncytial virus (HRSV) replication (MIC = 6.25 micrograms/mL) while the other compounds are inactive. On the other hand, all the examined compounds displayed an antitumor activity comparable to that of the reference compound 1-beta-D-arabinofuranosyladenine (ara-A), 7-deaza-EHNA being the most active of all. The results obtained showed that there is no correlation between adenosine deaminase inhibition and antiviral or antitumor activity in this series of compounds. 3-Deaza-EHNA, the most active inhibitor of ADA among the EHNA deaza analogues, greatly potentiates the antitumor activity of ara-A in vitro. In vivo activity was observed only when the two compounds were used in combination.

Adenine↗

PubMed1988

Studies of anthracycline--DNA complexes by circular dichroism.

A series of doxorubicin and daunorubicin analogues have been investigated in aqueous solution and as DNA-bound forms by means of circular dichroism (c.d.) spectroscopy. The structural variants comprise modifications on the amino sugar, on the aliphatic ring and the side chain of the aglycone moiety, and of the substitution pattern of the anthraquinone chromophore. Results with compounds having conformational constraints interfering with optimal fitting to DNA indicate that stereochemistry and conformation of the aliphatic ring predominantly affect c.d. spectra of anthracyclines in DNA-bound as well as in free form. Conformational correspondence with the known structure of the daunorubicin-oligonucleotide complex is inferred from the spectra of derivatives with modifications at position 6 or 11 in the anthraquinone chromophore. On the other hand, a different binding geometry is postulated for compounds either lacking the 4-methoxy group of daunorubicin (idarubicin and derivatives) or having a phenolic function in its place (carminomycin and derivatives). A possible relation with cytotoxic activity is discussed at a speculative level.

Antibiotics, Antineoplastic↗

PubMed1987

Chemical and biological characterization of 4'-iodo-4'-deoxydoxorubicin.

4'-Iodo-4'-deoxydoxorubicin is a doxorubicin (DXR) analogue with greater lipophilicity and reduced basicity of the amino group. In vitro 4'-iodo-4'-deoxydoxorubicin is more cytotoxic than DXR against a panel of human and murine cell lines and is characterized by a higher and faster uptake. In vivo, the spectrum of activity of 4'-iodo-4'-deoxydoxorubicin is comparable to that of DXR, but the new compound has higher activity against murine P388 leukemia resistant to DXR and against pulmonary metastases from Lewis lung carcinoma. Moreover, the new analogue exhibits antitumor activity also after p.o. administration and shows no cardiotoxicity in experimental systems.

Administration, Oral↗

PubMed1987

Improved synthesis and antitumor activity of 1-deazaadenosine.

A more convenient synthetic route to 1-deazaadenosine (1) by reduction of the new nucleoside 7-nitro-3-beta-D-ribofuranosyl-3H-imidazo[4,5-b]pyridine (6) is reported. Compound 6 was obtained by reaction of 7-nitroimidazo-[4,5-b]pyridine with 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose in the presence of stannic chloride followed by treatment with methanolic ammonia. 1-Deazaadenosine (1) showed good activity in vitro as inhibitor of HeLa, KB, P388, and L1210 leukemia cell line growth, with ID50 values ranging from 0.34 microM (KB) to 1.8 microM (P388). The nitro derivative 6 demonstrated moderate activity against the same cell lines.

Animals↗