Transplantability of human head and neck squamous cell carcinomas in athymic nude mice

Tumor material from 91 patients with squamous cell carcinoma of the head and neck was transplanted subcutaneously in athymic nude mice. In the first (man to mouse) passage, the calculated mean probability of tumor take in a single mouse was 11%. The probability of growth in the first passage was significantly better for moderately and poorly differentiated tumors than for well-differentiated tumors. Also, the implantation of lymph node material resulted in a significantly better tumor take rate than material taken from a primary tumor. Transplantability was not dependent on the following characteristics: localization, T or N stage of the tumor, or the sex of the patients. Once growth was established, all variables studied had no influence on the probability of growth in the subsequent mouse passages. A relationship between tumor growth in nude mice and patient prognosis could not be found. When transplanting head and neck squamous cell carcinoma in nude mice, it has to be recognized that some tumor characteristics will influence the success of tumor growth.     

A genetic progression model of oral cancer: current evidence and clinical implications

Based on recent genetic studies, we propose a progression model for the development of oral squamous cell carcinoma. In the initial phase, a stem cell acquires a genetic alteration; subsequently a patch is formed, a clonal unit consisting of the stem cell with its daughter cells that all share the DNA alteration. The next critical step is the conversion of a patch into an expanding field as a result of additional genetic alterations. This mucosal field replaces the normal epithelium and in the oral cavity such fields have been detected with dimensions of over 7 cm in diameter. Sometimes these fields are visible as leukoplakia. Ultimately, clonal selection leads to the development of carcinoma within this contiguous field of pre-neoplastic cells. An important clinical implication of this model is that fields often remain after surgery of the primary tumor and may lead to new cancers, presently designated by clinicians as second primary tumors or local recurrences.     

Cytomorphometric parameters in exfoliated cells as biomarkers in head and neck cancer chemoprevention

Quantitative DNA analysis has often been proposed as a potential tool capable of detecting preneoplastic tissue and as such to function as an intermediate endpoint in cancer chemoprevention trials. The first aim of this study was to test whether cytomorphometric parameters could be used to detect field cancerization characteristics in cytological preparations of oral mucosa. Cytomorphometric parameters in exfoliated cells of apparently normal oral mucosa of head and neck cancer patients were compared with those of healthy controls. The second aim was to assess the value of these parameters subsequently as intermediate endpoint biomarkers in the mucosa of 70 patients receiving N-acetylcysteine and/or retinyl-palmitate as chemopreventive drugs. No differences were detected between 'high risk' and healthy mucosa, nor were differences observed before and after treatment.     

Antitumor activity of prolonged as compared with bolus administration of 2′,2′-difluorodeoxycytidine in vivo against murine colon tumors

2′,2′-Difluorodeoxycytidine (gemcitabine) is a cytidine analogue with established antitumor activity against several experimental tumor types and against human ovarian and non-small-cell lung cancer. Both preclinical studies and most clinical trials involving patients with solid tumors have focused on short-term administration schedules; however, mechanistic studies indicate that a continuous-infusion schedule may be more effective. We determined the maximal tolerated dose (MTD) of gemcitabine in mice using various schedules. At these MTDs we observed considerably better antitumor activity of gemcitabine in two of three murine colon carcinoma lines using a prolonged administration as compared with a standard bolus protocol (i.p. 120?mg/kg q3d×4). On the latter schedule, Colon 26–10 grown in BALB/c mice was the most sensitive tumor line, showing a growth-delay factor (GDF, number of doubling times gained by the treatment) of 6.7, whereas Colon 38 (grown in C57/B16 mice) was the least sensitive tumor, displaying a GDF of 0.9. Prolonged treatment (q3d×6) of Colon 26–10 at a lower dose (100?mg/kg) enhanced the antitumor activity (GDF 9.6) while producing similar toxicity. A similar weight loss was found following the continuous infusion (c.i.) of gemcitabine using Alzet osmotic pumps s.c. for 3 or 7 days (2?mg/kg), but the GDF increased to 2.4 in Colon 38 (C57/B16) as compared with that provided by the bolus injections. Continuous infusion of gemcitabine at 15?mg/kg per 24?h q7d×2 i.v. via the tail vein was more effective than bolus injection against Colon 26–10, with the GDF being >17.7 and 73% of the tumors regressing completely. However, against Colon 38 tumors this schedule was not effective (GDF 0.4), even with a 25% higher dose. The plasma pharmacokinetics of gemcitabine was determined after one bolus dose (120?mg/kg). The peak concentration of gemcitabine was 225?μM and that of the deaminated catabolite 2′,2′-difluorodeoxyuridine (dFdU) was 79?μM. The elimination of gemcitabine was much faster than that of dFdU, with the t _1/2ß values being 15?min and 8?h, respectively. For the c.i. schedules, plasma concentrations were below the detection limit of the assay (<0.5?μM). Our results suggest that prolonged infusion of gemcitabine can give a better antitumor activity than bolus injections and shows promise of being active in clinical trials.     

In vitro antitumour activity of cis- and trans-5-fluoro-5,6-dihydro-6-alkoxy-uracils; effects on thymidylate synthesis.

A class of new 5-fluorouracil (FU) analogues, the 5-fluoro-5,6-dihydro-6- alkoxy-uracils was synthesised with a modification at the 6-position of the pyrimidine ring. At this position the analogues have a hydroxy or alkoxy group of different chain lengths either in the cis- or trans-configuration. The antiproliferative effect of these compounds was tested on five cell lines of different origin. Generally, the analogues with a cis-configuration had a higher activity than those with a trans-configuration. The growth inhibitory effect of the compounds decreased with increasing alkoxy chain length, but the compound with a hydroxy group had the lowest growth inhibitory effect. One analogue, cis-5-F-5,6-dihydro-6-methoxy-uracil had a higher antiproliferative effect than FU in one of the cell lines. Effects on thymidylate synthase (TS), the possible target of these analogues, were evaluated by thymidine rescue of growth inhibition and incorporation of tritiated deoxyuridine (3H-UdR) into DNA. In solid tumour cell lines addition of TdR reversed the antiproliferative effect. Inhibition of TS in intact cells was determined by measuring 3H-UdR incorporation in two cell lines. The effect of cis-5-F-5,6-dihydro-6-methoxy-uracil on incorporation of 3H-UdR was 2- to 5-fold stronger than that of FU in both cell lines. All other compounds produced a higher 3H-UdR incorporation than FU both at equimolar and equi-toxic concentration. Concluding from these results we regard cis-5-F-5,6-dihydro-6-methoxy-uracil as the most promising FU analogue of this series, because of its higher antiproliferative activity than FU and marked inhibition of TS in intact cells.     

Inflammation increases vulnerability to hypoxia in newborn piglets: effect of reoxygenation with 21% and 100% O2

OBJECTIVE: The purpose of this study was to assess whether inflammation increases vulnerability to hypoxia, and influences the effect of 100% O(2) and 21% O 2 reoxygenation on brain. STUDY DESIGN: Newborn piglets (n = 31) were randomized to 4 interventional groups: pretreatment with saline or endotoxin. After hypoxia they were reoxygenated with 21% or 100% oxygen for 30 minutes, followed by 21% oxygen for all groups. To assess brain injury we measured extracellular brain tissue glucose, glycerol, and lactate/pyruvate by microdialysis, brain tissue oxygen tension, and laser Doppler flow. RESULTS: Administration of endotoxin reduced the time to reach base excess (BE) -20 mmol/L by median 32 minutes compared with saline ( P < .05). We found no differences in changes in biochemical markers, brain tissue microcirculation, or oxygen tension between piglets in the 4 groups. CONCLUSION: Endotoxin and hypoxia acted synergistically in inducing metabolic acidosis. In the presence of experimental inflammation, 21% oxygen seems as effective as 100% O(2) in reoxygenating piglets.     

Comparison of bleomycin and radiation in the G2 assay of chromatid breaks

PURPOSE: To compare bleomycin with radiation in the G2 chromatid break assay. Controversy exists in the literature about whether G2 bleomycin chromatid-break sensitivity links with cancer predisposition in the same way as the G2 chromatid radiosensitivity test (the so-called 'G2 assay'). Although bleomycin is referred to as a 'radiomimetic' agent, it differs from radiation in the way the damage is induced. MATERIALS AND METHODS: Epstein-Barr virus-immortalized lymphoblastoid cell lines from two head and neck squamous cell carcinoma patients, two breast cancer patients, two ataxia-telangiectasia patients and two normal control persons were used. Chromosomal damage was determined in cells exposed to 0.3-Gy radiation or 5 mU ml(-1) bleomycin. The numbers of chromatid breaks per cell and of aberrations per cell (i.e. breaks and gaps) were determined. RESULTS: A strong positive correlation was found between the two different damage inducers (r=0.99; p<0.001). This correlation was similar for both the breaks per cell and the total aberrations per cell. Inclusion of gaps in the scoring of chromatid breaks was associated with a higher variability of the data, but this did not influence the outcome of this study. CONCLUSIONS: Both bleomycin and radiation give the same sensitivity phenotypes as determined by the G2 assay of chromatid breaks. Thus, when no radiation facility is present, bleomycin seems to be a good alternative to radiation for this type of assay.     

A genetic explanation of Slaughter's concept of field cancerization: evidence and clinical implications

The concept of "field cancerization" was first introduced by Slaughter et al. [D. P, Slaughter et al., Cancer (Phila.), 6: 963-968, 1953] in 1953 when studying the presence of histologically abnormal tissue surrounding oral squamous cell carcinoma. It was proposed to explain the development of multiple primary tumors and locally recurrent cancer. Organ systems in which field cancerization has been described since then are: head and neck (oral cavity, oropharynx, and larynx), lung, vulva, esophagus, cervix, breast, skin, colon, and bladder. Recent molecular findings support the carcinogenesis model in which the development of a field with genetically altered cells plays a central role. In the initial phase, a stem cell acquires genetic alterations and forms a "patch," a clonal unit of altered daughter cells. These patches can be recognized on the basis of mutations in TP53, and have been reported for head and neck, lung, skin, and breast cancer. The conversion of a patch into an expanding field is the next logical and critical step in epithelial carcinogenesis. Additional genetic alterations are required for this step, and by virtue of its growth advantage, a proliferating field gradually displaces the normal mucosa. In the mucosa of the head and neck, as well as the esophagus, such fields have been detected with dimensions of >7 cm in diameter, whereas they are usually not detected by routine diagnostic techniques. Ultimately, clonal divergence leads to the development of one or more tumors within a contiguous field of preneoplastic cells. An important clinical implication is that fields often remain after surgery of the primary tumor and may lead to new cancers, designated presently by clinicians as "a second primary tumor" or "local recurrence," depending on the exact site and time interval. In conclusion, the development of an expanding preneoplastic field appears to be a critical step in epithelial carcinogenesis with important clinical consequences. Diagnosis and treatment of epithelial cancers should not only be focused on the tumor but also on the field from which it developed.