Biomedical subjects

G Milano

Publications and source records attributed to G Milano.

At least 73 records · Page 4Linked to original sources

PubMed2000

Impact of UFT on tumoral TS and DPD levels in colorectal cancer.

This was an open lable, pilot translational clinical pharmacology study of a brief (7 day) course of UFT, 300 mg/m2/day, in combination with leucovorin, 90 mg/day, in six patients with newly diagnosed advanced colorectal cancer. The primary objectives of the study were to examine the impact of this treatment course on the UFT targets which are thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD). The rate of tumoral TS inhibition after the 7-day UFT treatment sequence varied from 5% up to 31%. UFT treatment induced a constant and variable decrease in tumor DPD activity ranging from 13% to 60%. UFT treatment induced a constant increase in uracil concentrations both in plasma and tumors. FT, 5-FU and the metabolite fluoro-beta-alanine (FBAL) were found in plasma and tumors at variable concentrations; the highest drug concentrations were those of FBAL in plasma. The present translational clinical study provides data related to the in vivo pharmacological effects of UFT with a description of its impact on cellular targets.

Administration, Oral↗

PubMed1999

Cytosine deaminase/5-fluorocytosine-based vaccination against liver tumors: evidence of distant bystander effect.

BACKGROUND: The cytosine deaminase gene of Escherichia coli converts the nontoxic compound 5-fluorocytosine into 5-fluorouracil (5-FU), thereby acting as a suicide gene when introduced into cancer cells, killing the cells when they are exposed to 5-fluorocytosine. We analyzed the efficacy of using cytosine deaminase-bearing cancer cells as an autologous tumor vaccine in a rat model that mimics liver metastasis from colon carcinoma. METHODS: We introduced a plasmid vector containing the E. coli cytosine deaminase gene into a BDIX rat colon carcinoma cell line. Intrahepatic injection of the modified cells in syngeneic animals generates a single experimental liver "suicide tumor." We then analyzed the effect of 5-fluorocytosine treatment in terms of regression of cytosine deaminase-expressing cells in vivo as well as protection against wild-type cancer cells. RESULTS: Treatment with 5-fluorocytosine induced regression of cytosine deaminase-expressing (CD+) tumors, with seven of 11 treated animals being tumor free at the end of 30 days and a statistically significant difference in tumor volumes between treated and control animals (two-sided P<.0001). Intrahepatic injection of CD+ cells followed by 5-fluorocytosine treatment rendered the treated animals resistant to challenge with wild-type tumor cells, with no (zero of seven) treated animals developing wild-type tumors in contrast to all (four of four) control animals. Moreover, in animals with established wild-type liver tumors, injection of CD+ tumor cells followed by 5-fluorocytosine treatment produced a statistically significant increase in survival time (two-sided P<.0001). In vivo immunodepletion and immunohistologic analysis of experimental tumors indicate that natural killer cells are the major immune component involved in this antitumor effect. CONCLUSIONS AND IMPLICATIONS: Taken together, these results suggest the potential use of suicide gene-modified tumor cells as therapeutic vaccines against liver metastasis from colon carcinoma.

Animals↗

PubMed1999

Dihydropyrimidine dehydrogenase deficiency and fluorouracil-related toxicity.

Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism. We report lymphocytic DPD data concerning a group of 53 patients (23 men, 30 women, mean age 58, range 36-73), treated by 5-FU-based chemotherapy in different French institutions and who developed unanticipated 5-FU-related toxicity. Lymphocyte samples (standard collection procedure) were sent to us for DPD determination (biochemical method). Among the whole group of 53 patients, 19 had a significant DPD deficiency (DD; below 150 fmol min(-1) mg(-1) protein, i.e. less than 70% of the mean value observed from previous population study). There was a greater majority of women in the DD group (15 out of 19, 79%) compared with the remaining 34 patients (15 out of 34, 44%, P<0.014). Toxicity was often severe, leading to patient death in two cases (both women). The toxicity score (sum of WHO grading, theoretical range 0-20) was twice as high in patients with marked DD (below 100 pmol min(-1) mg(-1) protein, n = 11, mean score = 13.2) compared with patients with moderate DD (between 150 and 100 pmol min(-1) mg(-1) protein, n = 8, mean score = 6.8), P = 0.008. In the DD group, there was a high frequency of neurotoxic syndromes (7 out of 19, 37%). The two deceased patients both had severe neurotoxicity. The occurrence of cardiac toxicity was relatively rare (1 out of 19, 5%). These data suggest that women are particularly prone to DPD deficiency and allow a more precise definition of the DD toxicity profile.

Adult↗

PubMed1999

A multifactorial approach including tumoural epidermal growth factor receptor, p53, thymidylate synthase and dihydropyrimidine dehydrogenase to predict treatment outcome in head and neck cancer patients receiving 5-fluorouracil.

The prognostic value of tumoural epidermal growth factor receptor (EGFR), p53, thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) was analysed on 82 advanced head and neck cancer patients (71 men, 11 women; mean age 59). Induction treatment was cisplatin-5-FU +/- folinic acid (61 patients, Chem group) or concomitant cisplatin-5-FU-radiotherapy (21 patients, RChem group). EGFR (binding assay), p53 protein (Sangtec immunoluminometric assay), TS and DPD activities (radioenzymatic assays) were measured on biopsies obtained at time of diagnosis. Significant positive correlation was demonstrated between p53 and EGFR. In the RChem group, p53 was higher in non-complete responders (median 1.03 ng mg(-1)) than in complete responders (median 0.08 ng mg(-1)) (P = 0.057). Univariate Cox analyses stratified on treatment group showed that specific survival (33 events) was significantly related to T staging, p53 taken as continuous or categorial (below vs over 0.80 ng mg(-1)) variable, and EGFR (below vs over 220 fmol mg(-1)); survival increased when EGFR and p53 were below thresholds. Multivariate stepwise analysis including T staging, EGFR and p53 revealed that T staging and EGFR were independent predictors of survival; relative risks were 3.68 for T staging and 2.65 for EGFR. Overall, EGFR remained an independent prognostic factor when response to treatment and T staging were considered in the multivariate analysis.

Adult↗

PubMed1999

Cytotoxic effects of two gamma linoleic salts (lithium gammalinolenate or meglumine gammalinolenate) alone or associated with a nitrosourea: an experimental study on human glioblastoma cell lines.

Gamma linoleic acid (GLA) salts may exert a direct antiproliferative activity on tumor cells. The cytotoxicity is linked to the generation of conjugated dienes, peroxyl radicals and superoxide radicals. Lithium gammalinolenate (LiGLA) and meglumine gammalinolenate (MeGLA) have been recently developed for enhancing the water solubility of these compounds. MeGLA or LiGLA (10(-5) to 10(-4) mol/l) and fotemustine (Fote) (2 x 10(-6) to 2 x 10(-4) mol/l) were applied, alone or in combination, for up to 9 days to two human glioblastoma cell lines A172 and U373MG. Fote was applied first followed by LiGLA and/or MeGLA. Cytotoxicity was evaluated by the MTT test, and the effects of drug combinations were analyzed by the isobolographic representation according to the Chou and Talalay method (combination indexes). For both GLA salts, cytotoxicity was manifested after 4 days of cell exposure and with very sharp dose-response curves. Comparison of IC50 values indicated that MeGLA was more active than LiGLA. There was a constant reduction in IC50 values following an increase in exposure time for A172 cells: between 4 and 9 days of cell exposure, IC50 changed from 73 to 46 microM for LiGLA and from 49 to 31 microM for MeGLA (p<0.05). With U373MG cells, there was no influence of exposure duration on IC50 values. Combination index values indicated that association between Fote and GLA salts globally resulted in slightly antagonistic effects. These results may be useful for further development of GLA salts at the clinical level.

Antineoplastic Agents↗

PubMed1999

Variable intrinsic sensitivity of human tumor cell lines to raltitrexed (Tomudex) and folylpolyglutamate synthetase activity.

The cytotoxic effects of Tomudex (TX) were investigated on a panel of 15 human tumor cell lines expressing a spontaneous sensitivity to the tested agent. We determined the basal cellular amount of relevant cellular factors potentially related to the cytotoxic efficacy of or resistance to TX. We selected thymidylate synthase (TS) as the target for TX, basal reduced folates (RF), because RF may compete with TX for a common site on the TS molecule. We also tested folylpolyglutamate synthetase (FPGS) because this is the enzyme which transforms the drug into its active polyglutamated form. Results were as follows. There was a wide inter-cell line variability in IC50 values for TX and there were marked differences between cell lines for all tested biochemical parameters. No link was observed between basal cellular TS activity and TX cytotoxic efficacy. There was an inverse relationship between reduced folate cellular content and TX IC50 values; this relationship did not, however, reach statistical significance. The only significant relationship was found between basal cellular FPGS activity and TX IC50r = -0.56, p = 0.03. Tumor cells with a relatively high FPGS activity were more sensitive to TX cytotoxic effects and vice versa. Along with previous results which showed that acquired resistance to TX is accompanied by a decrease in FPGS activity, the present data are strongly indicative of a prominent role played by FPGS activity in the intrinsic sensitivity to TX. Means to up-regulate FPGS activity with pharmacological or tumor-specific genetic approaches are recommended so as to optimize TX antitumor activity.

Animals↗

PubMed1999

Modulation of 5-fluorouracil by 5-ethyl-2'-deoxyuridine on cell lines expressing different dihydropyrimidine dehydrogenase activities.

The purpose of the present study was to clarify the significance of the inhibition of dihydropyrimidine dehydrogenase (DPD) in the modulation of 5-fluorouracil (5-FU) action by 5-ethyl-2'-deoxyuridine (EUdR). Four human cell lines, which differed in their susceptibility to 5-FU and in their DPD activity, were selected as biological objects. Several other enzymes of pyrimidine metabolism, i.e. thymidylate synthase (TS), thymidine kinase (TK) and pyrimidine nucleoside phosphorylase (PNP), which might be involved in the 5-FU action were also studied to elucidate their potential role in the modulation of 5-FU cytotoxicity. Two out of the four cell lines, i.e. COLO1 and SW620, showed low (57 and 28 pmol/min/mg protein) and the other two cell lines, i.e. CAL51 and CAL33, showed high (235 and 184 pmol/min/mg protein) DPD activity, respectively. In our study, contrary to our expectation, no correlation between the DPD and TS activity of the cell lines and their 5-FU sensitivity could be observed. EUdR alone was cytotoxic only on CAL33 cells in a concentration below 1 mM (IC50=194 microM) which might be due to the high TK activity (857 pmol/min/mg protein) measured in this cell line, favoring the formation of the phosphorylated nucleotides EdUMP and EdUTP indispensable for the inhibition of TS and DNA polymerase, respectively. Surprisingly, although EUdR by metabolizing to EUra was able to reduce the high activity of DPD in CAL33 and CAL51 cells by 47 and 55%, respectively, no potentiation of the 5-FU action occurred on these cell lines. On the contrary, enhancement of the 5-FU cytotoxicity was demonstrated on COLO1 and SW620 cells with low DPD activity. Our findings suggest that the 5-FU modulatory action of EUdR may be directed on other molecular targets than DPD as well, i.e. the augmentation of TS inhibition by EdUMP as demonstrated on SW620 cells might be one of these mechanisms.

Antimetabolites, Antineoplastic↗

PubMed1999

Time-schedule dependency of S 16020, a new topoisomerase II inhibitor.

S 16020 is a new olivacine derivative which has been shown to intercalate into DNA and to stabilize the cleavable complex formed by DNA and purified topoisomerase II. The aim of the present study was to estimate the impact of time exposure on the in vitro activity of S 16020. This was done on seven cancer cell lines of human origin (head and neck, kidney, and ovary). Doxorubicin was used as a reference drug. The cytotoxic activity of S 16020 remained stable during at least 3 h. A loss of activity of about 30% was apparent after 6 or 24 h preincubation. This relative loss of activity reached about 50% after 72 h preincubation. Considering all tested cell lines, the average IC50 decrease was 89+/-8% for S 16020 with incubation times between 1 and 72 h. An exposure index (El) was calculated to evaluate the effect of time on the cytotoxic efficacy. The reference time was 1 h exposure. The El values were corrected to take into account the loss of drug activity. For the majority of cell lines EI values were greater than 1 for both drugs, particularly after a 6 h exposure time. This means that, in this case as compared to the shorter exposure (1 h), increasing time has a relative detrimental effect on drug efficacy. For the two cancer cell lines of ovarian origin, El values remained close to 1 for both drugs whatever the total exposure time. This means that, in this case, time and concentration have symmetrical effects on cell survival. The pharmacological information provided by the present study may be useful in designing future clinical trials on this potentially interesting new topoisomerase II inhibitor. As a consequence of these data, 1 and 3 h drug administration schedules are currently tested during phase I trials.

Animals↗

PubMed1999

Differential depression of myocardial function and metabolism by lactate and H+.

The effects of both high blood H+ concentration ([H+]) and high blood lactate concentration ([lactate]) under ischemia-reperfusion conditions are receiving attention, but little is known about their effects in nonischemic hearts. Isolated rat hearts were Langendorff perfused at constant flow with media at two pH values (7.4 and 7.0) and two [lactate] (0 and 20 mM) in various sequences (n = 6/group). Coronary flow and arterial O2 content were kept constant at levels that allowed hearts to function without O2 supply limitation. We measured contractility, O2 uptake, diastolic pressure, and at the end of the protocol, tissue [lactate] and pH. Perfusion with high [lactate] raised tissue [lactate] from 5.5 +/- 0.1 to 17.5 +/- 2.6 micromol/heart (P < 0.0001), whereas decreasing the pH of the medium decreased tissue pH from 6.94 +/- 0.02 to 6.81 +/- 0.06 (P = 0.002). Heart rate was not affected by high [lactate] but was reversibly depressed by high [H+] (P = 0.004). Developed pressure declined by 20% in response to high [lactate], high [H+], and high [lactate] + high [H+] (P = 0.002). After the high-[lactate] challenge was withdrawn, pressure continued to decline. In contrast, withdrawing the high [H+] challenge allowed partial recovery. The behavior of diastolic pressure mirrored that of developed pressure. Although unaffected by high [lactate], the O2 uptake was reversibly depressed by high [H+]. This suggests higher O2 cost per contraction in the presence of high [lactate]. We conclude that for similar acute contractility depression, high [lactate] induces irreversible damage, likely at some point in the pathway of O2 utilization. In contrast, the effect of high [H+] appears reversible. These differential behaviors may have implications for heart function during heavy exercise and ischemia-reperfusion events.

Animals↗

PubMed1999

[The topical therapy of ulcerative colitis. A multicenter study with beclomethasone dipropionate foam].

BACKGROUND AND AIMS: The use of steroids was recently extended to the various forms of ulcerative rectocolitis by the introduction of topical formulations, above all steroids with an hepatic "first pass" devoid of systemic interference. The aim of this study was to evaluate the efficacy and tolerability of Beclomethasone dipropionate (BDP) in a rectal foam formulation, in the treatment of patients suffering from ulcerative colitis. METHODS: The experimental protocol took the form of a 28-day open prospective trial using BDP rectal foam in patients suffering from ulcerative colitis. Endoscopic, histological, clinical and tolerability parameters were evaluated. The centres taking part in the trial collected data for 60 cases out of a total of 80 patients enrolled in the study, of both sexes and aged between 20 and 81 years old, suffering from proctosigmoiditis (46.7%) and ulcerative rectocolitis (53.3%). RESULTS: Endoscopic parameters showed an improvement after 28 days of treatment in 74.5% of patients; a clinical improvement was achieved in 65.2% of cases. In percentage terms of the mean value of all the improved parameters, histological parameters were altered in 56.9% of patients. With regard to tolerability 82% of patients judged the treatment to be good/excellent. CONCLUSIONS: In conclusion, in line with recent reports regarding other pharmaceutical forms of BDP, including the use of rectal foam, these data confirm the efficacy and tolerability of this molecule and emphasise the validity of its use in the treatment of ulcerative colitis and proctosigmoiditis.

Administration, Topical↗

PubMed1999

[Topical beclomethasone dipropionate (BDP) in intestinal inflammatory diseases: the results of a multicentre trial].

The authors assessed the efficacy and tolerability of BDP in an open protocol using rectal enemas and suppositories and in a double-blind protocol vs mesalazine using rectal enemas. A total of 47 patients suffering from ulcerous rectocolitis were enrolled in the study and treated for 42 days while undergoing endoscopic, histologic and clinical controls. In conclusion, the authors affirm that BDP may represent a useful new therapeutic instrument in the treatment of slight to moderately severe forms of inflammatory intestinal disease.

English Abstract↗

PubMed1998

Combination of irinotecan (CPT11) and 5-fluorouracil with an analysis of cellular determinants of drug activity.

We evaluated the combination SN38 (7-ethyl-10-hydroxycamptothecin) -5fluorouracil (5FU) +/- folinic acid (FA) on six human colon cancer cell lines expressing spontaneous sensitivity to both drugs. Tumoral parameters potentially related to drug sensitivity were investigated: topoisomerase I (topo I) cleavable complexes formed with SN38, thymidylate synthase (TS) activity, folylpolyglutamate synthetase activity and dihydropyrimidine dehydrogenase activity. Drugs (SN38 and/or 5FU +/- FA) were applied for 72 hr, either sequentially or together. The concentration ratio between SN38 and 5FU was 100. Cytotoxicity (MTT [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide] test), DNA flow cytometry and isobologram analysis (Chou and Talatay) were performed. Based on 5FU IC50 values and isobologram analyses, the most cytotoxic schedule was SN38 followed by 5FU - FA, with high synergistic effects. Flow cytometry indicated that SN38 induced a more or less marked S-G2 block in all cell lines. Sensitivity to SN38, 5FU +/- FA, or combinations were not linked to the potential above-cited tumoral parameters. Interestingly, an inverse correlation was demonstrated between TS activity and topo I cleavable complexes (r2 = 0.78, P = 0.019). These data emphasize the critical importance of the irinotecan-5FU schedule and strongly support this association for the treatment of potentially 5FU-sensitive tumors.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1998

Concomitant b.i.d. radiotherapy and chemotherapy with cisplatin and 5-fluorouracil in unresectable squamous-cell carcinoma of the pharynx: clinical and pharmacological data of a French multicenter phase II study.

PURPOSE: The aim of this phase II study conducted on unresectable squamous cell carcinoma (USCC) of the oro- and hypopharynx was to associate twice-a-day (b.i.d.) continuous nonaccelerated radiotherapy with concomitant cisplatin (CP)-5-fluorouracil (5-FU) chemotherapy, both given at full dose. Feasibility, efficacy, survival, and pharmacokinetic-pharmacodynamic relationships were analyzed. METHODS AND MATERIALS: Fifty-four consecutive patients with strictly USCC of oro- and/or hypopharynx received continuous b.i.d. radiotherapy (RT) (2 daily fractions of 1.2 Gy, 5 days a week, with a 6-h minimal interval between fractions). Total RT dose was 80.4 Gy on the oropharynx and 75.6 Gy on the hypopharynx. Three chemotherapy (CT) courses of CP-5-FU were given during RT at 21-day intervals (third not delivered after the end of RT). CP dose was 100 mg/m2 (day 1) and 5-FU was given as 5-day continuous infusion (day 2-day 6: 750 mg/m2/day cycle 1, 750 mg total dose/day cycle 2 and 3). Pharmacokinetics was performed for 5-FU (105 h follow-up) and CP (single sample at 16 h). Special attention was paid to supportive care. RESULTS: Good feasibility of RT was observed (85.2% of patients with total dose > 75 Gy). Five patients received 1 CT cycle, 34: 2 cycles, and 15: 3 cycles. The most frequent and severe acute toxicities were mucositis with grade 3-4 occurring in 28% at cycle 1 and 86% at cycle 2, as well as neutropenia (43% at cycle 2). Locoregional control at 6 months was observed in 66.7% of patients. No late toxicity above grade 2 RTOG was noticed. CP dose and 5-FU AUC(0-105h) were significantly linked to grade 3-4 neutropenia (cycle 2). Cumulative total platinum (Pt) concentration and Karnofsky index were the only independent predictors of locoregional control at 6 months. Finally, total RT dose and total Pt concentration were the only independent predictors of specific survival. CONCLUSION: This protocol showed good locoregional response with an acceptable toxicity profile. Pharmacokinetic survey is probably an effective approach to further reduce toxicity and improve efficacy. A multicentric randomized phase III study, now underway, should confirm these encouraging results.

Adult↗

PubMed1998

Arthroscopic treatment of malunited and nonunited avulsion fractures of the anterior tibial spine.

Ten patients, presenting with a 10 degrees to 25 degrees deficit of knee extension after an avulsion fracture of the anterior tibial spine, were arthroscopically treated with debridement and abrasion of the anterior spine. Notchplasty was also performed in five cases where there was a more severe deficit of extension. At follow-up (mean: 39.4 months) eight patients had recovered the full articular range of motion of the knee whereas two had a slight residual deficit of extension of between 3 degrees and 5 degrees. In no case was ligament stability compromised as compared with preoperative assessment.

Adolescent↗

PubMed1998

Co-variables influencing 5-fluorouracil clearance during continuous venous infusion. A NONMEM analysis.

The objective of this study was to attempt to identify patient co-variables which could influence interpatient variability in 5-fluorouracil (5-FU) clearance during a 5-day continuous venous infusion (CVI, cisplatin 100 mg/m2 day 1 then 5-FU 1 g/m2/day days 2-6). The analysis was performed using a NONMEM program according to a linear one-compartment model. A total of 186 cycles (2 samples per day, 8 a.m. and 5 p.m.) were analysed from 104 patients with various cancers (the majority of head and neck and oesophagus). The study co-variables were age, sex, body surface area, hepatic metastases, peripheral mononuclear cell dihydropyrimidine dehydrogenase activity (PMNC-DPD), liver enzymes, clock-time (8 a.m. versus 5 p.m.), elapsed time during CVI. The data showed that 5-FU clearance was significantly reduced by increased age, low PMNC-DPD, high serum alkaline phosphatase and elapsed time during infusion. These data may be useful for improving knowledge of predictive factors which can influence 5-FU exposure and thus predispose to toxic manifestations.

Adult↗

PubMed1998

A clinically applicable assay for tumoral thymidylate synthase combining reverse transcriptase-PCR and high-performance liquid chromatography.

The main clinically relevant cellular target of 5-fluorouracil (5-FU) is the enzyme thymidylate synthase (TS). Both preclinical data and clinical data in digestive tract cancer indicate that an increased amount of TS in tumours can predict for 5-FU resistance. We developed an automated method combining the principle of RT-PCR coupled with HPLC separation and quantification. The RT-PCR HPLC method was applied to TS determination in tumoral biopsies from patients with colorectal cancer. The PCR samples were separated and quantified using a polystyrene divinylbenzene C 18 column. Within 22 min, it was possible to elute 18 peaks representing DNA sizes ranging from 34 to 622 bp. Both separation and quantification of beta 2 microglobulin (beta 2m, internal standard) and TS PCR products were achieved in approximately 10 min per sample. Validation of the RT-PCR HPLC method was established by comparing RT-PCR quantification of TS after electrophoresis and HPLC and by comparing the RT-PCR quantification of TS after HPLC with the classical biochemical method. The proposed HPLC method offers a 10-50 fold sensitivity advantage over electrophoresis. In addition, this RT-PCR HPLC procedure allows not only the quantification of TS expression but also the direct collection of unaltered amplified DNA sequence which could be useful for sequencing analysis, since TS mutations have been described. The present RT-PCR HPLC method for determining TS expression in tumoral biopsies is a valuable analytical approach as it is specific, sensitive and clinically applicable.

Adult↗

PubMed1998

Thymidylate synthase expression and activity: relation to S-phase parameters and 5-fluorouracil sensitivity.

Six human cancer cell lines exhibiting a large range of sensitivity to 5-fluorouracil (5-FU) were evaluated for thymidylate synthase (TS) and p53 gene expression, TS and dihydropyrimidine dehydrogenase (DPD) activity, as well as cell cycle parameters, S-phase fraction (SPF), bromodeoxyuridine labelling index (LI) and S-phase duration (SPD). All these parameters were investigated for 7 days in asynchronously growing cell populations and compared with the cell sensitivity to 5-FU. No significant correlation was found between S-phase parameters and TS gene expression and/or activity. TS activity was higher in proliferating cells; however, it was not significantly higher in rapidly growing cell lines with short SPD. Neither TS gene expression nor activity was found to correlate with 5-FU sensitivity. On the another hand, a statistically significant correlation (P < 0.0001) was observed between LI and SPD and 5-FU sensitivity. The present results suggest that cell cycle parameters such as SPD and/or LI could be better parameters for 5-FU sensitivity prediction than TS gene expression and/or activity. This could be especially informative in cases of concomitant radio-chemotherapy as S-phase parameters are already proposed for hyperfractionated radiotherapy planning.

Antimetabolites, Antineoplastic↗

PubMed1998

Comparison between short or long exposure to 5-fluorouracil in human gastric and colon cancer cell lines: biochemical mechanism of resistance.

Recent preclinical and clinical data indicate that the main mechanisms of 5-fluorouracil (5-FU) cytotoxicity depend on the mode of administration. To gather further insight into the major causes of acquired 5-FU resistance, drug-sensitive human gastric (M2), colon (HT29) and breast (MCF7) cancer cell lines were repeatedly exposed to a fixed concentration of 5-FU given either for 1 or 24 h. Although equieffective doses (IC50) of 5-FU were used, resistance to a 1 h exposure of 5-FU developed faster in all models than to a 24 h exposure. Cell lines with acquired resistance to a 1 h application of 5-FU were only partly cross-resistant to a 24 h exposure, whereas lines with resistance to protracted application of 5-FU displayed significant cross-resistance to the 1 h schedule. Resistance to methotrexate was only seen in cell lines with acquired resistance to 24 h of 5-FU. All 5-FU-resistant cell lines showed reduced incorporation of 5-FU into cellular RNA. Furthermore, elevations of thymidylate synthase were seen in all cell lines with resistance to 24 h of 5-FU but also in one cell line with resistance to a bolus schedule. No alterations in folylpolyglutamate synthase developed in the resistant cell lines. These data support the concept that the main mechanisms of 5-FU cytotoxicity depend on the mode of application. Incorporation of fluorouridine triphosphate into RNA appears to be the most important mechanism of action for 5-FU bolus schedules, whereas inhibition of thymidylate synthase becomes more important as the infusion time is prolonged. These data could have implications on the interaction of 5-FU given at different schedules with various other cytostatic agents.

Adenocarcinoma↗