Biomedical subjects

G B Snow

Publications and source records attributed to G B Snow.

At least 37 records · Page 2Linked to original sources

PubMed2000

Targeting of a hydrophilic photosensitizer by use of internalizing monoclonal antibodies: A new possibility for use in photodynamic therapy.

Coupling of photosensitizers to tumor-selective monoclonal antibodies (MAbs) is an attractive option for improving the selectivity of photodynamic therapy (PDT). For this purpose, hydrophilic sensitizers would be most suitable because of their solubility in water. However, such sensitizers are known to be ineffective in PDT, probably because they cannot readily pass the cell membrane and reach the critical intracellular target. We used the model compound TrisMPyP-PhiCO(2)H, a hydrophilic porphyrin derivative, to test the hypothesis that hydrophilic photosensitizers might become of therapeutic value when directed into the tumor cell by use of internalizing MAbs. TrisMPyP-PhiCO(2)H was conjugated using a labile ester. Conjugates showed no impairment of integrity on SDS-PAGE, full stability in serum in vitro, and optimal immunoreactivity when the sensitizer:MAb ratio was </=3. At higher molar ratios, the solubility of the conjugates decreased. In vitro internalization experiments showed that TrisMPyP-PhiCONH-(125)I-cMAb U36 and TrisMPyPPhiCONH-(125)I-mMAb 425 conjugates were internalized by A431 cells, in contrast to TrisMPyP-PhiCONH-(125)I-mMAb E48 conjugates. Data on the in vitro efficacy of PDT with MAb-conjugated TrisMPyP-PhiCO(2)H showed that the internalizing cMAb U36 and mMAb 425 conjugates were phototoxic to A431 cells, while the non-internalizing E48 conjugate and the unconjugated sensitizer were not. Biodistribution data of conjugates with sensitizer:(125)I-cMAb U36 ratios varying from 1:1 to 3:1 in tumor-bearing nude mice revealed selective accumulation in the tumor. Conjugates with higher molar ratios were cleared more rapidly from the blood than the unconjugated (125)I-cMAb U36, resulting in lower tumor uptake but similar tumor-to-blood ratios. Our data suggest that hydrophilic photosensitizers might have therapeutic value when targeted to tumors by internalizing MAbs.

Animals↗

PubMed2000

p53 immunoexpression in non-malignant oral mucosa adjacent to oral squamous cell carcinoma: potential consequences for clinical management.

p53 is a tumour suppressor gene encoding a protein whose function is impaired in a very large proportion of human cancers. The objectives of this study were to determine the natural history of p53 alterations during stages of oral carcinogenesis, by comparing p53 immunoexpression in oral squamous cell carcinomas (OSCCs), their non-malignant adjacent mucosa, and respective metastases; and to define the potential practical consequences for clinical management of p53 staining in the non-malignant adjacent mucosa. Forty-two samples of non-malignant mucosa adjacent to OSCCs, the respective carcinomas, and six lymph node metastases derived from six of the OSCCs were investigated for p53 protein expression by immunohistochemistry. Seven out of 42 (17%) non-malignant mucosal samples immediately adjacent to OSCC showed suprabasal p53 staining and this was significantly associated with moderate/severe dysplasia (p=0.02). In six of these cases (86%), the respective carcinoma showed p53 immunoexpression in more than 50% of the neoplastic cells and in the remaining case, p53 immunoexpression was found in more than 25% of the neoplastic cells. In all p53-negative carcinomas that showed p53 immunoexpression in the non-malignant adjacent mucosa, p53 staining was never detected above the basal cell layer. Lymph node metastases showed the same patterns of p53 immunoexpression as the carcinomas from which they were derived. When suprabasal p53 staining is present in non-malignant mucosa immediately adjacent to OSCCs, this suggests stable p53 alterations which are maintained upon progression to overt malignancy. The immunostaining in non-malignant mucosa of the resection margins of OSCCs might be a valuable predictor for local recurrences and may therefore have implications for the management of patients who have received surgical treatment for OSCC.

Adult↗

PubMed2000

Squamous cell carcinoma of maxillary sinus.

BACKGROUND: Medical records of 43 patients with histologically proved diagnosis of squamous cell carcinoma who were treated between the years 1975 and 1994 at the department of Otolaryngology Head Neck Surgery, VU Amsterdam were examined. METHODS: Tumors were restaged according to UICC classification 1997. Thirty-eight patients were treated for cure, nine were treated with chemotherapy followed by external beam radiotherapy, and 28 patients were treated with surgery followed by postoperative radiotherapy. No patient was lost to follow-up. Data with respect to survival were analyzed. RESULTS: Eighty-three percent of the tumours were in stage III or stage IV at the time of first presentation. Five-year survival after surgery and postoperative radiotherapy for all patients was 64%. For stages II, III, and IV it was 83%, 49%, and 37%, respectively. Cervical nodal metastases were present in 4.1% at the time of presentation. Thirty-seven percent of the patients survived 2 years after chemotherapy followed by radiotherapy. CONCLUSIONS: Squamous cell carcinoma continues to be diagnosed late. Surgery followed by radiotherapy remains the treatment of choice. Mandibulotomy should be considered for better clearance of retromaxillary space in T3 -T4 tumors. The eye should be preserved whenever it is oncologically safe to do so.

Adult↗

PubMed2000

Positive surgical margins in neck dissection specimens in patients with head and neck squamous cell carcinoma and the effect of radiotherapy.

BACKGROUND: To evaluate the outcome after surgery and radiotherapy for extensive nodal disease in patients with primary head and neck cancer. METHODS: Between 1973 and 1995, 77 from a total of 1398 patients had histopathologic evidence of positive margins in 85 neck dissection specimens for squamous cell carcinoma of the oral cavity, oropharynx, larynx, or hypopharynx. Postoperative radiotherapy with a curative dose was given to 50 necks. Ipsilateral neck recurrence was defined as the relevant event, and cumulative survival distributions were estimated by the Kaplan-Meier method. Differences between groups were analyzed with the log rank test. RESULTS: Disease-free survival was 24.9% at 2 years, and disease-specific survival was 33.6% at 2 years. After restriction of the 50 patients who received postoperative curative radiotherapy, the time to neck recurrence was stratified according to irradiation dosage, with 62.5 Gy as the cutoff point. A statistically significant difference was found for patients treated with 62.5 Gy or more, with a regional control rate of 75.6% at 2 years (p <.036). CONCLUSIONS: The overall outcome after neck dissection with positive surgical margins is poor. Considerable improvement is achieved by postoperative radiotherapy treatment with dosages of 62.5 Gy or more.

Adult↗

PubMed2000

Lymphoscintigraphy and ultrasound-guided fine needle aspiration cytology of sentinel lymph nodes in head and neck cancer patients.

Accurate staging of the regional lymph nodes is crucial for the appropriate management of patients with squamous cell carcinoma of the head and neck (HNSCC). However, the current diagnostic modalities have low accuracy for N0 neck, and even the most optimal procedure, ultrasound-guided fine needle aspiration cytology (USgFNAC), still has a sensitivity of only 42%-73%. In this study we evaluated whether the identification of the sentinel node might improve the selection of lymph nodes for USgFNAC. Twelve HNSCC patients received 3-4 peritumoral injections of 10-30 MBq 99mTc-labeled colloidal albumin, and the sentinel node was identified by dynamic scintigraphy and marked on the skin using a handheld probe, and/or by scintillation counting of the aspirates. After sentinel node identification USgFNAC was performed. Correct aspiration of the identified sentinel node(s) was confirmed by scintillation counting. In 11 out of 12 cases the sentinel node(s) could be visualized by dynamic planar imaging. In one case the sentinel node(s) were identified by scintillation counting only. In a number of patients different or supplementary lymph nodes were aspirated on the basis of sentinel node identification. These initial data strongly suggest that sentinel node identification might improve the staging of the neck by USgFNAC.

Biopsy, Needle↗

PubMed2000

Molecular diagnosis of head and neck cancer.

Patients with advanced stages of head and neck cancer frequently develop locoregional recurrence as well as distant metastases. These data indicate that traditional diagnostic methods such as histopathology and radiology are not sensitive enough to detect the small numbers of tumor cells which are left behind, defined as minimal residual disease (MRD). Sensitive diagnostic assays based on molecular markers appear to be powerful tools to improve the staging of these patients. At the DNA level, tumor-specific p53 mutations seem to have great potential for the detection of "occult" tumor cells at surgical margins and lymph nodes. At the RNA level HNSCC associated antigens like the E48 antigen, allow the detection of rare HNSCC cells in blood and bone marrow and, it is hoped, also in lymph nodes and lymph node aspirates. However, the molecular assays which are used to detect MRD are subject to certain (technical) problems which affect their sensitivity and specificity. In this paper we will present examples of molecular assays such as the plaque assay using p53 mutations and the E48 RT-PCR, and show their use for MRD detection in cervical lymph nodes. In addition, we will discuss the problems and pitfalls associated with these sensitive techniques.

Artifacts↗

PubMed2000

Advanced squamous cell carcinoma of the base of the tongue treated with surgery and post-operative radiotherapy.

BACKGROUND: Early stage squamous cell carcinoma of the base of the tongue has been successfully treated with radiotherapy and brachytherapy. However, the vast majority of these tumours seen in Western Europe are already at an advanced stage. Medical records of 79 patients with squamous cell carcinoma of the base of the tongue treated between 1980 and 1994 were examined. METHODS: Eighty-three per cent of the primary tumours were stage T3 or T4. Fifty-nine patients were treated with surgery and post-operative radiotherapy. Quality of life assessment amongst the survivors was performed by means of a questionnaire. RESULTS: Five year disease free survival in patients undergoing excision for T3-T4 tumours was 59%. Patients with T2-T3 tumours undergoing partial excision of the tongue base had a 3 year recurrence free survival rate of 68%. Distant metastasis occurred in 16%. Seventy-eight per cent of the patients judged their quality of life to be near normal. CONCLUSION: Surgery and post-operative radiotherapy offer a reasonably good survival in advanced carcinoma of the base of the tongue with preservation of quality of life.

Carcinoma, Squamous Cell↗

PubMed2000

Screening for distant metastases in patients with head and neck cancer.

OBJECTIVES: The detection of distant metastases at initial evaluation may alter the selection of therapy in patients with head and neck squamous cell carcinoma (HNSCC). In this study the value of screening for distant metastases is evaluated. STUDY DESIGN: Retrospective analysis. METHODS: The results of screening for distant metastases were retrospectively analyzed in 101 consecutive HNSCC patients with high-risk factors who were scheduled for major surgery. All patients had computed tomography (CT) scan of the thorax, bone scintigraphy, examination of the liver by ultrasound and/or CT scan, and blood tests. RESULTS: Distant metastases were found in 17% of the patients. Patients with four or more clinical lymph node metastases or low jugular lymph node metastases had the highest incidence of distant metastases (33%). CT scan of the thorax detected in 12 patients, lung metastases; in 4, mediastinal lymph node metastases; and in 2, primary lung tumors. Bone scintigraphy detected in four patients bone metastases; in all four patients lung or mediastinal lymph node metastases were also found. Ultrasound and/or CT scan of the liver revealed one patient with metastases. Blood tests did not show any significant difference between patients with or without bone or liver metastases. CONCLUSIONS: Screening in patients with three or more lymph node metastases, bilateral lymph node metastases, lymph nodes of 6 cm or larger, low jugular lymph node metastases, locoregional tumor recurrence, and second primary tumors revealed distant metastases in 10% or more. CT scan of the thorax is currently the single most important diagnostic technique for screening of distant metastases.

Adult↗

PubMed2000

Neck dissection for advanced lymph node metastasis before definitive radiotherapy for primary carcinoma of the head and neck.

OBJECTIVE: To evaluate the outcome of neck dissection for advanced metastasis and subsequent planned radiotherapy to the neck and primary tumor. STUDY DESIGN: Single-center, retrospective case series. METHODS: From 1988 to 1998, 37 previously untreated patients were included into the study protocol. Two had a single tumor-positive neck node and the remaining 35 had multiple tumor-positive neck nodes (mean number, 6.0). Extranodal spread was reported in 35 cases (95%); mean nodal size was 5.7 cm (SD, 2.4 cm). Five patients (14%) were not irradiated or were irradiated with palliative intention. Of the remaining patients, 30 received irradiation of 60 Gy or more to the neck and the primary tumor (mean dose, 66.9 Gy; SD, 4.2 Gy). Cumulative survival distributions were estimated by the Kaplan-Meier method, and differences between groups were analyzed with the log-rank test. RESULTS: Treatment-related mortality was observed in three patients (8%). Disease-specific survival was 49% at 2 years and the overall locoregional control rate was 43% at 2 years. Patients with T1 to T2 primary lesions were compared with those with advanced primary disease, and the 2-year local control rates were 76% and 47%, respectively (P = .056). The following prognostic factors were identified for distant metastasis: three or more positive nodes (P = .037), positive surgical margins in the neck dissection specimen (P = .004), and time from diagnosis until neck dissection of 23 days or more (P = .043). The influence of distant metastasis on disease-specific survival was evident (P = .0003). CONCLUSION: Patients with low-T-stage tumors have a better local control rate with this regimen and survival depends on the status of the neck.

Adult↗

PubMed2000

Mutagen sensitivity as a biomarker for second primary tumors after head and neck squamous cell carcinoma.

The occurrence of second primary tumors after curative treatment of early stage head and neck squamous cell carcinoma negatively influences the overall survival. Our aim was to prospectively evaluate whether mutagen sensitivity (mean number of chromatid breaks per cell in cultured lymphocytes exposed to bleomycin) could be used as a biomarker to predict which patients will develop second malignancies in the respiratory or upper digestive tract. Patients treated for head and neck squamous cell carcinoma (n = 218) were followed for approximately 6 years. Nineteen patients developed a second primary tumor, and each of these patients was matched on age, gender, cumulative smoking, tumor site, and tumor stage to two patients who did not develop any second malignancy. No difference between the groups was found with respect to mutagen sensitivity. Smoking at the time of the index tumor had a significant influence on the occurrence of second primary tumors (log-rank, P = 0.019). There was a significantly (P = 0.005) higher mean breaks-per-cell value in those patients who had developed their second primary tumor > or = 3 years after the first tumor (0.97 +/- 0.24; n = 10) compared with early second primary tumor patients (0.69 +/- 0.09; n = 9). Conditional on a more than 3-year second primary tumor-free survival (n = 38), there is a significantly (log-rank, P = 0.036) higher probability of a second primary tumor for mutagen-sensitive patients [relative risk, 7.8 (95% confidence interval, 0.99-61.74; P = 0.05)]. Mutagen sensitivity is a potential biomarker for the occurrence of 'late' second malignancies (> 3 years between tumors), and additional studies on the inclusion of this biomarker in chemoprevention trials is commendable because it would greatly improve their efficiency.

Aged↗

PubMed2000

Safety and biodistribution of 99mTechnetium-labeled anti-CD44v6 monoclonal antibody BIWA 1 in head and neck cancer patients.

The CD44 protein family consists of isoforms, encoded by standard exons and up to nine alternatively spliced variant exons (v2-v10), which are expressed in a tissue-specific way. Expression of v6-containing variants (CD44v6) has been related to aggressive behavior of various tumor types and was shown to be particularly high in squamous cell carcinoma (SCC). Therefore, CD44v6 might be a suitable target for radioimmunoscintigraphy (RIS) and therapy. The present study evaluates the novel high-affinity murine anti-CD44v6 monoclonal antibody (MAb) BIWA 1 for its safety and targeting potential in patients with SCC of the head and neck (HNSCC). Twelve HNSCC patients, who had planned to undergo resection of the primary tumor and neck dissection, were included. Preoperatively, 2, 12, or 52 mg of 99nTc-labeled MAb BIWA 1 was administered. RIS results obtained 21 h after injection were compared with palpation, computed tomography, and magnetic resonance imaging, with histopathology as the gold standard. Moreover, biodistribution of BIWA 1 was evaluated by radioactivity measurement in blood and bone marrow and in biopsies from the surgical specimen obtained 40 h after injection. The distribution of BIWA 1 in tumor biopsies was analyzed by immunohistochemistry. BIWA 1 integrity in the blood was assessed by high-performance liquid chromatography and related to soluble CD44v6 levels in serum samples. No drug-related adverse events were observed. Human antimouse antibody responses were observed in 11 patients. The diagnostic efficacy of RIS appeared to be comparable for the three BIWA 1 dose levels and for the four diagnostic methods. Besides activity uptake in tumor tissue, minimal accumulation of activity was observed in mouth, lungs, spleen, kidney, bone marrow, and scrotal area. Analysis of tissue biopsies revealed high uptake in tumors, with a mean value of 14.2+/-8.4% of the injected dose/kg tumor tissue and a mean tumor:blood ratio of 2.0+/-1.4 at 40 h after injection. Differences among the three dose groups were not statistically significant, although a trend toward lower uptake in the highest dose group was noted. Distribution of BIWA 1 throughout the tumor was heterogeneous for all dose groups, which might be related to the high affinity of the MAb. The mean biological half-life in blood (34.5+/-6.1 h) was not dose dependent. Extensive complex formation of BIWA 1 was observed in the 2-mg group, most probably with soluble CD44v6 present in the blood, and complex formation relatively diminished upon increase of the MAb dose. BIWA 1 is a promising MAb for targeting HNSCC because it can be safely administered to HNSCC patients, while it shows high and selective tumor uptake. However, BIWA 1 is immunogenic, and therefore a chimerized or humanized derivative of BIWA 1 with intermediate affinity will be used in future clinical trials.

Adult↗

PubMed2000

Molecular assays for the diagnosis of minimal residual head-and-neck cancer: methods, reliability, pitfalls, and solutions.

The prognosis of cancer patients is determined by the radicalness of treatment: residual tumor cells will grow out and develop in manifest local recurrences, regional recurrences, and distant metastases. Classical diagnostic methods such as radiology and histopathology have limited sensitivities, and only by molecular techniques can minimal residual disease be detected. In tissue samples containing the normal tissue counterpart of a tumor, only tumor-specific markers can be exploited, whereas in other samples, tissue-specific markers can be used. At present, there are two main methodologies in use, one based on antigen-antibody interaction and the other based on amplified nucleic acids. The most commonly used nucleic acid markers are mutations or alterations in tumor DNA (tumor-specific markers) or differentially expressed mRNA (tissue-specific markers). Many reports and reviews have been published on the assessment of minimal residual disease by molecular markers, showing either positive or negative clinical correlations. One of the main reasons for these contradictory findings is the technical difficulty in finding the small numbers of tumor cells in the large number of normal cells, which necessitates sensitivities of the assays up to 1 tumor cell in 2 x 10(7) normal cells. These assays often are complex, demand considerable experience, and usually are laborious. In this review, we will address a number of the technical issues related to molecular assays for tumor cell detection that make use of nucleic acids as markers. Many difficulties in data interpretation are at least in part because of technical details that might have been solved by the incorporation of one or more appropriate controls. We hope that this review clarifies a number of these issues and help clinicians and investigators interested in this field to understand and weigh the contradictory findings in the published studies. This will help move the field forward and facilitate clinical implementation.

Biomarkers, Tumor↗

PubMed2000

Phase I therapy study of 186Re-labeled chimeric monoclonal antibody U36 in patients with squamous cell carcinoma of the head and neck.

UNLABELLED: A phase I therapy study was conducted to determine the safety, maximum tolerated dose (MTD), pharmacokinetics, dosimetry, immunogenicity, and therapeutic potential of 186Re-labeled anti-CD44v6 chimeric monoclonal antibody (cMAb) U36 in patients with squamous cell carcinoma of the head and neck (HNSCC). The potential of a diagnostic study with 99mTc-cMAb U36 to predict the biodistribution of 186Re-cMAb U36 was evaluated. METHODS: Thirteen patients with recurrent or metastatic HNSCC were given 750 MBq 99mTc-cMAb U36 (2 mg) followed 1 wk later by a single dose of 186Re-cMAb U36 (12 or 52 mg) in radiation dose-escalating steps of 0.4, 1.0, and 1.5 GBq/m2. After each administration, planar and SPECT images were obtained, and the pharmacokinetics and development of human antimurine as well as anti-cMAb responses were determined. Radiation absorbed doses to tumor, red marrow, and organs were calculated. RESULTS: Administration was well tolerated, and excellent targeting of tumor lesions was seen in all patients. Dose-limiting myelotoxicity (thrombocytopenia being most prominent) was the only toxicity observed, resulting in grade 4 myelotoxicity in 2 patients treated with 1.5 GBq/m2. The MTD was established at 1.0 GBq/m2, at which a transient grade 3 thrombocytopenia was seen in 1 patient. One patient showed stable disease for 6 mo after treatment at the MTD. The 2 patients with dose-limiting myelotoxicity showed a marked reduction in tumor size. The reduction was of short duration and, therefore, not considered an objective response. Tumor absorbed doses at MTD ranged from 3.0 to 18.1 Gy. Red marrow doses ranged from 20 to 112 cGy (mean, 51 +/- 16 cGy/GBq) and correlated with platelet nadir (r = 0.8; P < 0.01). Pharmacokinetics varied between patients treated at the same dose level and were accurately predicted by the diagnostic procedure. Five patients experienced a human anti-cMAb response, 1 of which was a human antimouse antibody response. CONCLUSION: This study shows that 186Re-cMAb U36 can be safely administered, with dose-limiting myelotoxicity at 41 mCi/m2. The use of cMAb U36 instead of its murine counterpart did not decrease the induction of human antibody responses. The availability of a 99mTc-labeled diagnostic study that can predict the pharmacokinetics of 186Re-cMAb U36 offers the possibility of using such a study for selection of a safe radioimmunotherapy dose.

Aged↗

PubMed1999

Characterization of CD44v6 isoforms in head-and-neck squamous-cell carcinoma.

CD44 splice variants, especially those containing the v6 domain, are assumed to play a critical role in the malignant progression of many human tumors. This concept was based on (i) the aberrant expression of CD44v6 in malignant cells, often encoded by alternatively spliced transcripts, and (ii) the absence of CD44v6 expression in corresponding normal tissues. Remarkably, data on CD44v6 expression in squamous cells do not support this hypothesis: the v6 domain is highly expressed in normal squamous tissues and down-regulation has been described in the majority of squamous-cell carcinomas of the head and neck (HNSCC). In this study, we have compared the expression of v6 in normal oral mucosa and HNSCC in a qualitative and quantitative way. Immuno-histochemistry was performed with 3 different anti-v6 antibodies (U36, U39 and VFF18) on a large panel of HNSCC cell lines and tumors. The v6-encoding splice variants were characterized by screening a cDNA library of a human HNSCC cell line and by RT-PCR on HNSCC cell lines, microdissected normal mucosa and primary as well as metastatic HNSCC tissue. The results revealed that there is no, or only marginal, down-regulation of CD44v6 in HNSCC. About 97% of the primary HNSCC tumors exhibited a high and homogeneous staining pattern (U36, 270/277; U39, 268/277 tumors with more than 50% positive cells). Furthermore, the v6-containing CD44 splice variants present in HNSCC primary tumors and metastases were identical to those expressed in normal mucosa. Our data indicate that v6-containing CD44 splice variants do not play a role in the malignant progression of HNSCC.

Alternative Splicing↗

PubMed1999

The impact of nutritional status on the prognoses of patients with advanced head and neck cancer.

BACKGROUND: Malnutrition has been recognized as a poor prognostic indicator for cancer treatment-related morbidity and mortality in general, and it is reported to affect 30-50% of all patients with head and neck cancer. In this study, the correlation of nutritional status with 3-year survival was studied prospectively in 64 patients with T2-T4 carcinomas of the head and neck who were treated surgically with curative intent; the surgery was often followed by radiotherapy. METHODS: All patients underwent nutritional screening according to six different parameters on the day prior to surgery. Overall and disease specific survival analyses were performed with a follow-up period of at least 3 years. Survival analyses were performed with the log rank test and the Cox proportional hazards model. RESULTS: Lymph node stage, nonradical resection margins, and occurrence of major postoperative complications were demonstrated to affect disease specific survival for the group as a whole. None of the investigated nutritional parameters were correlated with survival. When men and women were analyzed separately, however, a preoperative weight loss of >5% did have a prognostic value for men. The combination of male gender, preoperative weight loss, and major postoperative complications were related to early death. CONCLUSIONS: Apart from the well-known prognostic parameters lymph node status (T classification) and status of surgical margins, preoperative weight loss and occurrence of major postoperative complications were also found to have a negative effect on the survival of male patients undergoing surgery for advanced head and neck cancer.

Analysis of Variance↗

PubMed1999

Inherited susceptibility to bleomycin-induced chromatid breaks in cultured peripheral blood lymphocytes.

BACKGROUND: Susceptibility to bleomycin-induced chromatid breaks in cultured peripheral blood lymphocytes may reflect the way a person deals with carcinogenic challenges. This susceptibility (also referred to as mutagen sensitivity) has been found to be increased in patients with environmentally related cancers, including cancers of the head and neck, lung, and colon, and, in combination with carcinogenic exposure, this susceptibility can greatly influence cancer risk. The purpose of this study was to assess the heritability of mutagen sensitivity. METHODS: Heritability was determined by use of a maximum likelihood method that employed the FISHER package of pedigree analysis. Bleomycin-induced breaks per cell values for 135 healthy volunteers without cancer were determined. These individuals were from 53 different pedigrees and included 25 monozygotic twin pairs (n = 50), 14 pairs of dizygotes (twin pairs and siblings, n = 28), and 14 families selected on the basis of a first-degree relative who was successfully treated for head and neck cancer and who had no sign of recurrence for at least 1 year. All data were analyzed simultaneously, and different models of familial resemblance were fitted to the data. All P values are two-sided. RESULTS: Our results showed no evidence for the influence of a shared family environment on bleomycin-induced chromatid breaks. Genetic influences, however, were statistically significant (P =. 036) and accounted for 75% of the total variance. CONCLUSIONS: The high heritability estimate of the susceptibility to bleomycin-induced chromatid breaks indicates a clear genetic basis. The findings of this study support the notion that a common genetic susceptibility to DNA damage--and thereby a susceptibility to cancer--may exist in the general population.

Antimetabolites, Antineoplastic↗

PubMed1999

Considerations for in vitro retinoid experiments: importance of protein interaction.

Retinoids, natural and synthetic substances structurally related to vitamin A, are important modulators of cell proliferation and differentiation, and have proven activity in cancer therapy. Experiments to reveal the mechanism of action of retinoids are routinely performed in in vitro models. As retinoids are relatively hydrophobic and unstable, we hypothesized that the composition of culture media is of critical importance for the stability and bioavailability of these compounds. Various culture media were incubated with all-trans-, 13-cis- and 9-cis-retinoic acid (RA). Without fetal calf serum (FCS) or bovine serum albumin (BSA) in the medium, the concentration of these retinoids was found to decrease to considerably low levels. This excessive loss of retinoids was due to absorption to culture plates, reaction tubes and pipet tips. Binding of retinoids to BSA was demonstrated to have attenuating effects on uptake and metabolism of all-trans-RA, as studied in oral keratinocytes and head and neck cancer cells, indicating that a balance exists between the bioavailability and the aspecific loss of retinoids. In this study we demonstrate that the type of culture medium and especially the presence of protein in the medium is of paramount importance to perform reproducible experiments with retinoids.

Culture Media↗

PubMed1999

Development of meta-tetrahydroxyphenylchlorin-monoclonal antibody conjugates for photoimmunotherapy.

A limitation of photodynamic therapy is the lack of tumor selectivity of the photosensitizer. To overcome this problem, a protocol was developed for coupling of meta-tetrahydroxyphenylchlorin (mTHPC), one of the most promising photosensitizers, to tumor-selective monoclonal antibodies (MAbs). mTHPC was radiolabeled with 131I to facilitate the assessment of the in vitro and in vivo behavior. After the modification to 131I-mTHPC-(CH2COOH)4, thus increasing the water solubility and creating a functional moiety suitable for coupling, conjugation was performed using a labile ester. Insoluble aggregates were not formed when mTHPC-MAb conjugates with a molar ratio of up to 4 were prepared. These conjugates showed a minimal impairment of the integrity on SDS-PAGE, full stability in serum in vitro, and an optimal immunoreactivity. To test the in vivo behavior of the mTHPC-MAb conjugates, the head and neck squamous cell carcinoma-selective chimeric MAb U36 was used in head and neck squamous cell carcinoma-bearing nude mice. Biodistribution data showed that the tumor selectivity of cMAb U36-conjugated mTHPC was increased in comparison with free mTHPC, despite the fact that conjugates with a higher mTHPC:MAb ratio were more rapidly cleared from the blood. Preliminary results on the in vitro efficacy of photodynamic therapy with MAb-conjugated mTHPC showed that mTHPC coupled to the internalizing murine MAb 425 exhibited more phototoxicity than when coupled to the noninternalizing chimeric MAb U36.

Animals↗