Telomere length, telomerase activity and telomerase RNA expression in human esophageal cancer cells: correlation with cell proliferation, differentiation and chemosensitivity to anticancer drugs

The telomere and the enzyme telomerase in esophageal cancer have been poorly investigated. We present here aspects of the telomere and telomerase in esophageal cancer in relation to cell proliferation, differentiation and chemosensitivity to anticancer drugs. The telomere length (mean length of telomere restriction fragments; TRF), telomerase activity (TA), and human telomerase RNA (hTR) expression in a panel of 13 human esophageal cancer cell lines, squamous in origin, was examined by Southern blotting, the telomeric repeat amplification protocol (TRAP), and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Cell proliferation expressed by the doubling time, cell differentiation determined by the keratin 13 and/or 14 expression, and chemosensitivity to cisplatin (CDDP) and 5-fluorouracil (5-FU) were compared with telomere-related factors. TRF shortening, the up-regulation of TA, and hTR expression was seen in all 13 cell lines. The TA correlated positively with the telomere length and negatively with the hTR expression. The doubling times of the cell lines and the telomere-related factors did not show any significant relation. The TA in the keratin 13/14-negative cell lines was significantly higher than that of the keratin 13-positive cell lines. The cells with short telomere tended to be resistant to CDDP whereas the cells with higher TA tended to be more sensitive to CDDP; 5-FU showed no relation to any telomere-related factors. Therefore, the activation of TA in esophageal squamous cell carcinoma is regulated by cell differentiation but not by cell proliferation, cells with high TA are more sensitive to CDDP, and cells with short telomere require a CDDP dose escalation.

Role of p53 in hematopoietic recovery after cytotoxic treatment

Prompt reconstitution of hematopoiesis after cytoreductive therapy is essential for patient recovery and may have a positive impact on long-term prognosis. We examined the role of the p53 tumor suppressor gene in hematopoietic recovery in vivo after treatment with the cytotoxic drug 5-fluorouracil (5-FU). We used p53 knock-out (p53-/-) and wild-type (p53+/+) mice injected with 5-FU as the experimental model. Analysis of the repopulation ability and clonogenic activity of hematopoietic stem cells (HSCs) and their lineage-committed descendants showed a greater number of HSCs responsible for reconstitution of lethally irradiated recipients in p53-/- bone marrow cells (BMCs) recovering after 5-FU treatment than in the corresponding p53+/+ BMCs. In post-5-FU recovering BMCs, the percentage of HSC-enriched Lin- Sca-1(+) c-Kit+ cells was about threefold higher in p53-/- than in p53+/+ cells. Although the percentage of the most primitive HSCs (Lin- Sca-1(+) c-Kit+ CD34(low/-)) did not depend on p53, the percentage of multipotential HSCs and committed progenitors (Lin- Sca-1(+) c-Kit+ CD34(high/+)) was almost fourfold higher in post-5-FU recovering p53-/- BMCs than in their p53+/+ counterparts. The pool of HSCs from 5-FU-treated p53-/- BMCs was exhausted more slowly than that from the p53+/+ population as shown in vivo using pre-spleen colony-forming unit (CFU-S) assay and in vitro using long-term culture-initiating cells (LTC-ICs) and methylcellulose replating assays. Clonogenic activity of various lineage-specific descendants was significantly higher in post-5-FU regenerating p53-/- BMCs than in p53+/+ BMCs, probably because of their increased sensitivity to growth factors. Despite all these changes and the dramatic difference in sensitivity of p53-/- and p53+/+ BMCs to 5-FU-induced apoptosis, lineage commitment and differentiation of hematopoietic progenitors appeared to be independent of p53 status. These studies suggest that suppression of p53 function facilitates hematopoietic reconstitution after cytoreductive therapy by: (1) delaying the exhaustion of the most primitive HSC pool, (2) stimulating the production of multipotential HSCs, (3) increasing the sensitivity of hematopoietic cells to growth factors, and (4) decreasing the sensitivity to apoptosis.

Chemosensitivity of advanced larynx carcinoma cells in vitro and significance of multidrug resistance markers in these tumors

Thirty cases of previously untreated advanced larynx carcinoma were checked for in vitro chemosensitivity and presence of the resistance markers viz. P-glycoprotein (P-gp) glutathione-S-transferase-pi (GST-pi) and protein kinase C (PKC) overexpression. The cytotoxicity testing was done using MTT assay and the resistance markers were checked by immunohistochemical methods using monoclonal antibodies. The drug combinations employed in MIT assay were 5FU* + MTX*, 5FU + cisPt*, 5FU + Mito*, cisPt + Mito and MTX + Mito (*5FU = 5Fluorouracil, MTX-methotrexate, cisPt-cisplatin and Mito = mitomycin C). No statistically significant correlation was observed between resistance to the above drug combinations and presence of the resistance markers under consideration. A statistically significant correlation was observed between node positivity and expression of resistance markers which indicates that presence of one or more of these markers in these tumors may be considered as a negative prognosis marker. CisPt-Mito was found to be the most effective drug combination in vitro, in the cases studied.

Regulation of the PepT1 peptide transporter in the rat small intestine in response to 5-fluorouracil-induced injury

BACKGROUND & AIMS

The oligopeptide transport system of the small intestine is resistant to mucosal injury. The mechanism of this resistance was investigated by examining the activity level and expression of the peptide transporter PepT1 in the intestine of rats treated with 5-fluorouracil.

METHODS

The expression and localization of PepT1 were examined by immunoblot analysis of brush border membrane vesicles and immunohistochemical analysis of intestinal sections with PepT1-specific rabbit polyclonal antibodies. Also, Northern blot analysis was used for the expression of PepT1 messenger RNA (mRNA).

RESULTS

Although the amounts of sucrase and an Na+-dependent glucose transporter protein in intestinal vesicles decreased markedly after 5-fluorouracil treatment, the amount of PepT1 protein remained largely unaffected. Immunohistochemical analysis also showed that the PepT1 immunoreactivity level was preserved in the brush border membrane of the remaining villi of 5-fluorouracil-treated rats. Levels of amino acid, glucose, and phosphate transporter mRNAs were profoundly depressed in 5-fluorouracil-treated animals, whereas the level of PepT1 mRNA conversely increased.

CONCLUSIONS

The resistance of intestinal peptide transport to tissue injury may be attributable to increased synthesis of PepT1 rather than to a change in the kinetic properties of the residual absorbing cells.

[Sequential therapy with methotrexate and 5-fluorouracil in patients with advanced colorectal cancer pretreated with 5-fluorouracil plus folinic acid]

PURPOSE

To evaluate the efficacy and toxicity of a sequential low-dose methotrexate (MTX) and 5-fluorouracil (5FU) regimen in the palliative treatment of patients with advanced colorectal cancer.

PATIENTS AND METHODS

Enrolled in the study were patients with advanced colorectal cancer, refractory to 5FU + FA. Patients were treated with MTX 40 mg/m2 i.v. bolus d 1 and 8, 5FU 700 mg/m2 i.v. bolus d 2 and 9 (24 hours after MTX bolus). The cycle was repeated every 4 weeks.

RESULTS

48 patients entered the study, and 45 are evaluable. The overall response rate was 15% with 1 complete response and 6 partial responses. Eight patients obtained disease stabilization. Median time to progression was 9 months. Toxicity was mild. Grade 3 stomatitis was observed in 7 (15%) patients.

CONCLUSIONS

Sequential MTX/5FU is a well tolerated regimen with mild antitumor activity in refractory advanced colorectal patients.

A comparison of the in vivo and in vitro response of rat embryos to 5-fluorouracil

This study serves to further define the capabilities of the whole embryo culture system using the well-known teratogen, 5-fluorouracil (5-FU), an antineoplastic agent. An initial in vivo study was performed whereby pregnant rats were injected intraperitoneally with 10-30 mg/kg 5-FU on day 9 of gestation. On day 20 of gestation, the effects of this drug on the growth and development of embryos were evaluated. The number of externally malformed fetuses increased in a dose-related manner, and the most common defect was micro-/anophthalmos in fetuses of dams treated with 5-FU. Growth retardation was also noted in the 5-FU treated groups. An in vitro study was performed in which drug concentrations were varied (0.15-0.30 microg/ml). Externally abnormal embryos were observed in whole embryo culture system from embryonic day 9 to 11. The most common defect was hypoplastic optic vesicles. In the whole embryo culture system, crown-rump length, somite number, protein contents, and morphological score were decreased in a dose-dependent fashion. Finally, histological evaluation and observation of the pattern of cell death of the optic vesicle of 11-day-old embryos in in vivo and in vitro were performed. These parameters revealed no differences in response between in vivo and in vitro embryos treated with 5-FU, suggesting that the whole embryo culture system was an appropriate model for developmental toxicity studies of 5-FU.

Combined-modality therapy for esophageal cancer: phase I trial of escalating doses of paclitaxel in combination with cisplatin, 5-fluorouracil, and high-dose radiation before esophagectomy

Several recent reports support administering preoperative chemotherapy and radiotherapy to improve the outcome of patients with resectable esophageal malignancies. Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), 5-fluorouracil (5-FU), and cisplatin are known radiosensitizers, and paclitaxel has demonstrated single-agent activity in patients with metastatic esophageal cancer. This study sought to define the maximum tolerated dose of paclitaxel given with 5-FU, cisplatin, and 60 Gy radiotherapy before esophagectomy to patients with potentially resectable lesions. Seventeen patients so treated underwent esophagectomy. Three patients with metastatic disease, treated to obtain more information about the toxicity of the combined-modality regimen, did not undergo surgery. Over 6 weeks, 60 Gy radiation was administered in 2-Gy fractions. During radiation treatment, continuous intravenous infusions of 5-FU 225 mg/m2/d were administered, with paclitaxel given weekly as a 1-hour intravenous infusion immediately preceding a 1-hour cisplatin infusion. Surgery was performed 4 to 6 weeks after the completion of radiotherapy. The 27 patients, one of whom was a woman, had a median age of 58 years and an Eastern Cooperative Oncology Group performance status of 0 (10 patients) or 1. Three patients had a squamous cell histology, while 22 had adenocarcinoma; two had other histologies. The paclitaxel dose levels were 25 mg/m2 in four patients, 40 mg/m2 in five patients, 60 mg/m2 in nine patients, and paclitaxel 50 mg/m2 with 5-FU reduced to 200 mg/m2 in nine patients. The latter proved to be the maximum tolerated dose combination, with cisplatin held constant at 25 mg/m2. This level represents weekly dose intensities of 9.6 Gy radiation, 48 mg/m2 paclitaxel, 24 mg/m2 cisplatin, and 192 mg/m2 5-FU. Diarrhea in four patients, mucositis and dehydration in seven, electrolyte wasting in two, gram-positive catheter-related infection in three, and neuropathy in one proved dose limiting. Hematologic toxicity was relatively mild, with three episodes of nonneutropenic bacteremia, one of which was fatal. Postoperative chemotherapy consisting of four cycles of paclitaxel 175 mg/m2 over 3 hours and cisplatin 75 mg/m2 over 1 hour every 3 weeks was planned but rarely feasible due to postoperative morbidity and poor tolerability of postoperative chemotherapy. Therefore, the use of two induction cycles of this regimen given before the combined-modality study regimen is currently being investigated. Of 17 patients whose surgical specimens were assessed pathologically, three had complete remissions and 14 had partial remissions, five of which were characterized as very good, showing only microscopic foci and marked radiation effects. The median follow-up of the 17 patients who underwent surgery is 50 weeks (range, 5 to 111 weeks). Three relapses occurred at 26, 33, and 43 weeks. We conclude that this is an intense combined-modality preoperative regimen for patients with esophageal cancer. Determining the efficacy of this regimen will require further follow-up and the performance of phase II trials.

Chemotherapy for relapsed head and neck cancer: paclitaxel, cisplatin, and 5-fluorouracil in chemotherapy-naive patients. A dose-finding study

The aim of this trial was to identify the maximum tolerated dose of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) administered via a 3-hour infusion day 1, together with cisplatin 20 mg/m2/d days 1 to 3 and 5-fluorouracil 200 mg/m2/d bolus days 1 to 3 every 21 days. The prophylactic administration of colony-stimulating factors was not allowed. Twenty-three patients with relapsed and/or metastatic squamous cell carcinoma of the head and neck previously treated with surgery and/or radiotherapy were accrued. None had received chemotherapy previously. No grade 3/4 hematologic toxicity at nadir or other limiting toxicities were recorded with paclitaxel at 100 to 135 mg/m2 (six patients, 26 courses). Seven patients (six evaluable, 22 courses) were treated with 160 mg/m2. Grade 4 neutropenia at nadir with fever lasting 3 days was observed in one patient. Nonhematologic toxicities, including temporary peripheral neuropathy, asthenia, myalgias, vomiting, and mucositis were generally mild. Three patients were treated with 180 mg/m2 (eight courses). Grade 4 neutropenia at nadir was recorded in all patients and was febrile in two. Seven patients (six evaluable, 23 courses) were treated with paclitaxel 160 mg/m2, cisplatin 25 mg/m2/d, and 5-fluorouracil 250 mg/m2/d. Grade 4 febrile neutropenia at nadir was recorded in one patient. One episode of grade 4 mucositis and two episodes of grade 3 diarrhea were also recorded. Overall, eight responses (38%) were observed. In conclusion, the combination of paclitaxel 160 mg/m2, cisplatin 25 mg/m2/d, and 5-fluorouracil 250 mg/m2/d for 3 consecutive days can be administered safely without growth factor support. This regimen merits further investigation in a phase II trial.

Paclitaxel and weekly 24-hour infusion of 5-fluorouracil/folinic acid in advanced gastric cancer

The current phase II study evaluates the safety and efficacy of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) and 5-fluorouracil (5-FU) plus folinic acid in patients with advanced gastric cancer. Paclitaxel 175 mg/m2 was given intravenously over 3 hours on days 1 and 22; folinic acid 500 mg/m2 given intravenously over 2 hours followed by 5-FU 2,000 mg/m2 given intravenously over 24 hours was administered on days 1, 8, 15, 22, 29, and 36. Six weeks of treatment were considered one cycle, and each cycle was followed by 2 weeks off treatment. Twenty-two patients (six women and 16 men) with advanced/metastatic gastric cancer were entered on trial. All patients are evaluable for response and toxicity. None had received prior chemotherapy. Radiologically metastatic sites included gastric lymph nodes (64%), liver (36%), lungs (18%), peritoneum (18%), bone (9%), and skin (5%). No complete responses were observed. Seven patients (32%; 95% confidence interval, 12% to 52%) had a partial response. Sites of partial responses included the lungs, skin, lymph nodes, and locally advanced tumor. Twelve patients (55%) had stable disease and three (14%) had disease progression. At a median follow-up of 12 months (range, 1 to 17+ months), the median overall survival for all patients was 11 months (range, 1 to 17+ months; 95% confidence interval, 6.8 to 18.2) and the median progression-free interval was 8 months (range, 1 to 13+ months; 95% confidence interval, 4.7 to 9.8). Severe nonhematologic toxicities were alopecia (45%), fever/infection (9%), diarrhea (5%), and nausea/vomiting (5%). Grade 3/4 neutropenia occurred in three patients (14%). In summary, paclitaxel given every 3 weeks in combination with once-weekly, 24-hour continuous infusions of 5-FU/folinic acid is active in advanced gastric cancer and appears to achieve response rates comparable to regimens like etoposide/folinic acid/5-FU or 5-FU/doxorubicin/methotrexate. The toxicity of this new combination is moderate and allows treatment in an outpatient setting. Ongoing studies are evaluating the activity of paclitaxel combined with weekly continuous infusions of 5-FU/folinic acid with or without cisplatin.

Paclitaxel, cisplatin, and 5-fluorouracil in patients with advanced or recurrent squamous cell carcinoma of the head and neck: a preliminary report

The combination of 5-fluorouracil (5-FU) and cisplatin is considered the most active chemotherapy for patients with recurrent squamous cell carcinoma of the head and neck (SCCHN), with an overall response rate of 30%. Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has demonstrated activity in SCCHN and synergy with cisplatin. To augment the activity of the combination of 5-FU and cisplatin, a pilot study was designed to determine the feasibility of combining 3-hour infusional paclitaxel with 5-FU and cisplatin. To be eligible, patients had to have recurrent or advanced SCCHN with measurable or evaluable disease and no prior chemotherapy. A minimum of three courses had to be delivered to determine cumulative toxicity. The starting dose level consisted of paclitaxel 135 mg/m2 on day 1, cisplatin 75 mg/m2 on day 2, and 5-FU 1 g/m2 on days 2 through 6. The first treated patient developed grade 4 mucositis, which resulted in reducing dose level 1 of 5-FU to 800 mg/m2/d on days 2 through 6 (seven patients); subsequently, the 5-FU dose was adjusted to 1 g/m2/d on days 2 through 5 (nine patients). To date, 17 patients have been enrolled, with a median age of 62 years (range, 48 to 75 years). Of the 17 patients, nine had recurrent disease following prior surgery and/or radiotherapy and eight had previously untreated advanced SCCHN. Major toxicities were neutropenia and mucositis. There were four early deaths (two treatment-related and two cancer-related). Forty-seven courses of therapy were delivered, with a median of two (range, one to five). The overall response rate in 14 response-evaluable patients was 71% (10 of 14 patients; eight partial and two complete responses). Five of seven response-evaluable patients with recurrent disease had major responses (one complete and four partial responses). At the current dose, the combination of paclitaxel/5-FU/cisplatin is feasible and shows very encouraging activity, particularly in patients with recurrent SCCHN.

Paclitaxel, carboplatin, and long-term continuous 5-fluorouracil infusion in the treatment of upper aerodigestive malignancies: preliminary results of phase II trial

We evaluated the efficacy and toxicity of a novel chemotherapy regimen that included paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), carboplatin, and long-term, continuous-infusion 5-fluorouracil in the treatment of cancers of the upper aerodigestive tract. In the preoperative treatment of patients with localized esophageal cancer, we administered this regimen concurrently with radiation therapy. Thirty-eight patients with biopsy-proven cancers of the head and neck or esophagus entered this trial between January 1996 and November 1996. Patients with head and neck cancers considered curable with local treatment modalities were excluded. All patients received the following chemotherapy regimen: paclitaxel 200 mg/m2 via 1-hour intravenous infusion on days 1 and 21, carboplatin at an area under the concentration-time curve of 6.0 intravenously on days 1 and 21, and 5-fluorouracil 225 mg/m2/d via continuous infusion on days 1 to 42. Patients with localized esophageal cancer also received radiation therapy beginning on day 1 (1.8 Gy/d; total dose, 45 Gy). Patients were re-evaluated at week 6; responding patients received a repeat course of treatment, except for those with localized esophageal cancer, who underwent resection at week 10. Twenty-five of 29 evaluable patients had major responses to treatment. Four of five patients with locally advanced head and neck cancer had complete clinical responses, while eight of 11 patients with metastatic disease responded. All 13 evaluable patients with localized esophageal cancer underwent resection, and nine (69%) had a pathologic complete response. Toxicity was moderate, with brief grade 3/4 leukopenia occurring in 19 patients (66%). Esophagitis occurred in five of 13 patients receiving concurrent chemotherapy and radiation therapy, but was reversible and generally occurred during the last week of radiation therapy. Other grade 3/4 toxicity was uncommon. This novel regimen of paclitaxel, carboplatin, and long-term 5-fluorouracil infusion is feasible and highly active in patients with cancers of the upper aerodigestive tract. It can be used concurrently with radiation therapy before resection for localized esophageal cancer. The high overall response rates, and particularly the high pathologic complete response rates in resected patients with esophageal cancer, are encouraging and warrant further evaluation of this regimen.

[Lethal drug interactions of the new antiviral, sorivudine, with anticancer prodrugs of 5-fluorouracil]

In 1993 eighteen Japanese patients with cancer and herpes zoster, a viral disease, died from interactions of the new oral antiviral drug, sorivudine (SRV: 1-beta-D-arabinofuranosyl-(E)-5-(2-bromovinyl)uracil), with oral anticancer prodrugs of 5-fluorouracil (5-FU) within 40 d after SRV was approved by the Japanese government and began to be used clinically. Before the death, most of these patients had severe symptoms of toxicity, including diarrhea with bloody flux and marked decreases in white blood cell and platelet counts. All of these patients received SRV daily for several days while being administered long-term anticancer chemotherapy with one of the oral 5-FU prodrugs. There was no acute toxic symptom in patients who received SRV alone or SRV and the other types of anticancer drugs. A toxicokinetic study was carried out using rats to investigate the mechanism of the acute death in the patients caused by drug interactions between SRV and 5-FU prodrugs. Rats were orally coadministered SRV with tegafur (FT: 1-(2-tetrahydrofuryl)-5-fluorouracil), a 5-FU prodrug that most of the patients were considered to receive before the death. All the rats receiving SRV and FT once daily showed extremely elevated levels of 5-FU in the plasma and tissues, including bone marrow and small intestines, and died within 10 d, while the animals given the same repeated dose of SRV or FT alone were still alive over 20 d without any appreciable toxic symptom. Before their death, there were a marked damage of bone marrow, a marked atrophy of intestinal membrane mucosa, marked decreases in white blood cells and platelets, diarrhea with bloody flux, and severe anorexia as reported for the patients. Data obtained by in vivo and in vitro studies indicated that (E)-5-(2-bromovinyl)uracil (BVU), generated from SRV by the gut flora and absorbed through the intestinal membrane, was reduced in the presence of NADPH to a reactive form by hepatic dihydropyrimidine dehydrogenase (DPD), a key enzyme regulating the tissue 5-FU levels from FT, bound covalently to DPD as a suicide inhibitor, and markedly retarded the catabolism of 5-FU. An irreversible inactivation by BVU of rat and human DPDs, expressed in E. coli for the latter, was observed in the presence of NADPH with their purified preparations in a manner reciprocal to radiolabelling of the enzyme proteins with [14C]BVU. SRV showed no inhibitory effect on the rat and human DPDs in the presence of NADPH.

In vivo selective gene expression and therapy mediated by adenoviral vectors for human carcinoembryonic antigen-producing gastric carcinoma

Previously, we reported that adenoviral vectors carrying the carcinoembryonic antigen (CEA) promoter sequences to direct the Echerichia coli beta-galactosidase gene (AdCEA-lacZ) or cytosine deaminase (CD) gene (AdCEA-CD) confer selective gene expression on a CEA-positive gastric cancer cell line (MKN45) in vitro. Here, adenovirus-mediated tumor-specific gene therapy for CEA-positive gastric carcinoma in vivo was investigated. Using an animal model with i.p. disseminated MKN45 tumors, adenovirus-mediated tumor-specific transgene expression and therapeutic efficacy were analyzed. After an i.p. injection of AdCEA-lacZ, beta-galactosidase activity was confined to tumor xenografts. Moreover, CD mRNA was expressed exclusively in MKN45 tumor xenografts after infection with AdCEA-CD, despite the fact that an adenovirus-mediated transfer of CD DNA was detected in all tissues tested. In contrast, CD mRNA was detected not only in tumor xenografts but also in other organs of mice infected with AdCA-CD, in which CD gene expression is governed by an ubiquitous promoter. Suppression of tumor growth and prolongation of survival were noted in tumor-bearing mice treated with AdCEA-CD and 5-fluorocytosine (5FC) without observable adverse effects. In contrast, significant hepatic toxicity was noted in animals treated with AdCA-CD. These results reveal that the CEA promoter restricts CD gene expression to CEA-positive tumor cells in the adenoviral context in vivo, along with the beneficial therapeutic effects of 5FC treatment, suggesting the i.p. AdCEA-CD/5FC system may provide a novel approach to treatment of i.p. disseminated gastric cancer.

Preferential cytotoxicity to tumor cells of 3,5-diprenyl-4-hydroxycinnamic acid (artepillin C) isolated from propolis

A tumoricidal substance was isolated from Brazilian propolis as guided by cytotoxicity assay on HuH 13 (human hepatocellular carcinoma) cell and was characterized to be 3-[4-hydroxy-3,5-bis (3-methyl-2-butenyl) phenyl]-2-propenoic acid (3,5-diprenyl-4-hydroxycinnamic acid (artepillin C)). It exhibited preferential cytotoxicity to tumor cells cultured in vitro. The cytotoxicity observed seemed to be partly attributable to apoptosis-like DNA fragmentation. The compound showed anti-tumor activity more effective than that of 5-fluorouracil to transplantable human tumor cell lines when tested on histoculture drug response assay system.

Optimal scheduling of interleukin 12 and chemotherapy in the murine MB-49 bladder carcinoma and B16 melanoma

The antitumor activity of interleukin (IL)-12, a naturally occurring cytokine, has been demonstrated in several murine solid tumors. Animals bearing established B16 melanoma or MB-49 bladder carcinoma were used to study the most effective scheduling of recombinant murine IL-12 (rmIL-12), along with systemic chemotherapy. rmIL-12 (0. 45, 4.5, or 45 microgram/kg) was more effective as a single agent when administered to mice bearing the MB-49 bladder carcinoma at the highest dose for 11 doses rather than for 5 doses. In combination with chemotherapy (Adriamycin, cyclophosphamide, or 5-fluorouracil), rmIL-12 administration did not increase the toxicity of the chemotherapy, and there was increased antitumor activity with each rmIL-12-drug combination. Administering rmIL-12 (45 microgram/kg) on days 4-14, along with Adriamycin, cyclophosphamide, or 5-fluorouracil on days 7-11, resulted in 2.2-2.7-fold increases in tumor growth delay, compared with the chemotherapy alone against the primary tumor, and a marked decrease in the number of lung metastases on day 20. Because the B16 melanoma grows more slowly than the MB-49 bladder carcinoma, allowing multiple courses of chemotherapy, cyclophosphamide could be administered. The rmIL-12 (45 microgram/kg)-cyclophosphamide combination regimen that was most effective overlapped 2 days with the terminal portion of the chemotherapy treatment. There was a parallel increase in the response of the primary tumor and metastatic disease to the lungs. Administration of rmIL-12 to animals bearing the MB-49 bladder carcinoma or the B16 melanoma was compatible with coadministration of chemotherapy at full dose without additional toxicity.

Nucleoside-mediated mitigation of 5-fluorouracil-induced toxicity in synchronized murine erythroleukemic cells

5-Fluorouracil (5-FU) is a chemotherapeutic agent known to retard embryonic growth and induce cleft palate and limb deformities. The predominant mechanism underlying its toxic action is thought to be inhibition of thymidylate synthetase (TS), and hence thymidine triphosphate (dTTP) synthesis, resulting in alteration of the balance of deoxynucleotide (dNTP) pools and disruption of DNA synthesis. Indeed, previously we demonstrated retarded cell-cycle progression concurrent with a 60% decrease in TS activity in rat whole embryos following maternal exposure to 40 mg/kg 5-FU on Gestational Day 14 and in the murine erythroleukemic cell (MELC) suspension culture following exposure to 5-25 microM 5-FU for 2 hr. In the study described herein, we used high-performance liquid chromatography (HPLC) to demonstrate in both of these model systems that 5-FU exposure results in similar patterns of dNTP perturbations: a prolonged decrease in dTTP and dGTP levels and an increase in dCTP and dATP. In addition, we used centrifugal elutriation to synchronize MELC in the phases of the cell cycle (G0/G1 and early S) most sensitive to 5-FU to investigate the ability of nucleoside supplementation to mitigate 5-FU-induced toxicity. Our data indicate that following a 2-hr exposure to 5-25 microM 5-FU, supplementation with 1-10 microM thymidine (TdR) for 24 hr partially reverses 5-FU-induced toxicity as evidenced by increased cellular proliferation and cell-cycle progression and amelioration of 5-FU-induced perturbations of protein synthesis and cellular membrane permeability compared to unsupplemented 5-FU-exposed cells. However, TdR concentrations >/=100 microM inhibited growth or were cytotoxic. In comparison, supplementation with 10 microM-10 mM of deoxycytidine (CdR) was not toxic, but effected a dose-dependent recovery from 5-FU-induced toxicity. At 1-100 microM, neither deoxyadenosine nor deoxyguanosine supplementation reduced 5-FU-induced toxicity; at higher concentrations, both purine nucleotides inhibited cell growth. Although these results support the hypothesis that 5-FU disrupts the MELC cell cycle by depleting dTTP (a perturbation that is reversible by TdR supplementation), they also indicate that CdR supplementation offers an additional recovery pathway.

Combination therapy with 5-fluorouracil and IFN-alpha2a induces a nonrandom increase in DNA fragments of less than 3 megabases in HT29 colon carcinoma cells

We have used pulsed-field gel electrophoresis to examine 5-fluorouracil (5FU)-induced DNA double-strand breaks (DSBs), both with and without modulation by IFN-alpha2a (IFNalpha), in HT29 human colon adenocarcinoma cells. Although 24-h treatment with either 10 microM 5FU or 500 units/ml IFNalpha did not result in significant DNA fragmentation, the combination of 5FU + IFNalpha resulted in a significant increase in DNA DSBs versus either drug alone (P < 0.05). The pattern of fragmentation induced by treatment with 5FU + IFNalpha was compared to that induced by gamma-radiation, which generates lesions at random sites, digestion with NotI restriction endonuclease, which cleaves at the specific sequence 5' ellipsis GCGGCCGCellipsis 3', and HhaI restriction endonuclease, which cleaves at the specific sequence 5'ellipsis GCGCellipsis 3'. 5FU + IFNalpha resulted in a specific pattern characterized by the accumulation of fragments of <3 Mb in the absence of fragments of >3 Mb, which differed from that of gamma-radiation and restriction endonuclease digestion. Because neither morphological nor DNA fragmentation characteristic of apoptosis was observed after 5FU + IFNalpha treatment, the nonrandom pattern of DSBs that was observed did not appear to be the result of the initiation of programmed cell death within these cells.

[Determination of dihydropyrimidine dehydrogenase in the prediction of toxic side effects of 5-fluorouracil]

In the chemotherapy of colorectal cancers the most frequently given drug is 5-fluorouracil, which in certain cases reduces or delays the appearance of the local recurrence or metastasis. It is well known that the patient's response to 5-fluorouracil is very different concerning both, effects and side effects. More than 80% of the infused drug is catabolised in the first 20 minutes after the treatment. The first and rate limiting enzyme of the catabolism is dihydropyrimidine dehydrogenase, which has the highest activity in the liver and lymphocytes. The activity of this enzyme shows correlation with the blood level of 5-fluorouracil. The deficiency of this enzyme caused severe, in some cases lethal toxicity, its congenital deficiency is responsible for familial pyrimidinaemia. Authors intended to collect data about the dihydropyrimidine dehydrogenase activity of colorectal cancer patients, in order to screen enzyme deficiency or very low enzyme activity, which might be in connection with the appearance of severe side effects, moreover to determine the optimal dose of 5-fluorouracil before the treatment. Dihydropyrimidine dehydrogenase activity was determined in the lymphocytes of 48 colorectal cancer patients, treated by 5-fluorouracil, at the beginning of each cytostatic cycle. The enzyme activity of the patients was between 1.2 and 24.4 pmol/min/10(6) lymphocyte. The value of the enzyme activity fluctuated in a range, characteristic for the individual patients and this value was not modified by the 5-fluorouracil treatment. Dividing the patients in two groups, low (lower than 5 pmol/min 10(6) lymphocyte) and high (higher than 15 pmol/min 10(6) lymphocyte) dihydropirimidine dehydrogenase activity, we found that decrease in the white blood cell number and appearance of the side effects occurred with much higher frequency in the low activity group which resulted in the reduction of the dose or in more serious cases interruption of the treatment. Authors conclude that the determination of the dihydropyrimidine dehydrogenase activity in the lymphocytes is a valuable method in the prediction of the toxic side effects of 5-fluorouracil, in the screening of the congenital enzyme deficiency and in the individualization of the 5-fluorouracil dosage.

Simple detection of chemical mutagens by the alkaline single-cell gel electrophoresis (Comet) assay in multiple mouse organs (liver, lung, spleen, kidney, and bone marrow)

Recently, we designed a fast and simple method to obtain nuclei for the alkaline SCG assay and we tested it with mouse liver, lung, kidney, spleen, and bone marrow. Instead of isolating organ cells by trypsinization, we homogenized tissue and isolated the nuclei. Each organ was minced, and the mince was suspended in chilled homogenizing buffer containing NaCl and Na2EDTA, homogenized gently using a Potter-type homogenizer set in ice, and then centrifuged. The nuclei from the precipitate were used for the assay. To evaluate the validity of this method, we tested the genotoxicity in mouse organs of 11 chemical mutagens with different modes of action. Mice were sacrificed 3 and 24 h after administration of each mutagen. Treatment with three alkylating agents (MMS, EMS, and MNNG), a DNA crosslinking agent (MMC), two aromatic amines (2-AAF and phenacetin), a polycyclic aromatic hydrocarbon (B[a]P), and two inorganic chemicals (KBrO3 and K2CrO4) increased migration of the DNA from mouse organs. 5-FU (a base analog) and colchicine (a spindle poison) treatment produced negative results in all organ studied. Considering that the alkaline SCG assay detects genotoxicity as DNA fragments derived from DNA single-strand breaks and alkali-labile damage, our results showed that the SCG assay using our homogenization technique detected chemical mutagens as a function of their modes of action.

[The cytotoxicity of Chamaenerium angustifolium (L.) Scop. and Hippophae rhamnoides L. tannins and their effect on mitochondrial respiration]

The cytotoxic activity of complexes of hydrolysable tannins of Chamaenerium angustifolium L. Scop. and Hippophae rhamnoides L. was compared with that of the antineoplastic drugs vinoblastin (VLB), methotrexate (MT), and 5-fluorouracil (5-FU). The tannins yield to VLB and MT in activity but resemble 5-Fu in their active concentration. They inhibited succinate oxidation by the rat liver mitochondria and their cytotoxicity was displayed in much lower concentrations than their inhibitory effect on mitochondrial respiration. It is concluded that tannins inhibit the respiratory chain at the third point of conjugation in the transfer of electrons from cytochrome c to oxygen.

Disruptions of the hypothalamo-pituitary-adrenal axis increase anticancer drug lethality in the rat

We have previously shown that toxicity of the anticancer agent hydroxyurea (HU) in the rat is markedly increased by hypophysectomy or adrenalectomy. In this study, we investigated whether increased toxicity in ablated animals is a unique feature of HU or it is shared with other anticancer agents; the toxic effects of five such drugs have been compared in intact, hypophysectomized (HYX) and adrenalectomized (ADX) rats. Bis-chloroethyl-nitrosourea (BCNU, 5-10 mg/kg), busulfan (0.1-10 mg/kg), cyclophosphamide (25-125 mg/kg), 5-fluorouracil (15-75 mg/kg) and vindesine (0.1-0.5 mg/kg) were given to intact and endocrine-ablated rats, and lethality was recorded over 3 weeks. It was found that mortality was low or absent in intact rats, whereas (with the exception of HYX rats receiving the highest dose of busulfan) it was dramatically increased by both hypophysectomy and adrenalectomy. However, replacement treatments with long-acting tetracosactrin and corticosterone to HYX and ADX rats respectively afforded significant protection against BCNU toxicity only. We conclude that the integrity of the hypothalamo-pituitary-adrenal axis is needed to tolerate the toxicity of various anticancer drugs, although complex mechanisms appear to underlie such protective effect.