Biomedical subjects

George D Wilson

Publications and source records attributed to George D Wilson.

25 records · Page 2Linked to original sources

PubMed2003

In vivo cell kinetic measurements in a randomized trial of continuous hyperfractionated accelerated radiotherapy with or without mitomycin C in head-and-neck cancer.

PURPOSE: Tumor cell repopulation is still considered to be a major cause of failure in radiotherapy. In this study, we investigated the influence of cell kinetic parameters on the outcome of patients treated in a randomized trial of accelerated fractionation, with or without mitomycin C, vs. conventional fractionation. METHODS AND MATERIALS: Sixty-two patients were studied using administration of bromodeoxyuridine (BrdUrd), and cell kinetic parameters were measured using flow cytometry. The patients were treated with either 70 Gy for 7 weeks or 55.3 Gy for 17 continuous days (V-CHART) with or without 20 mg/m(2) mitomycin C on day 5. RESULTS: The potential doubling time (Tpot) and labeling index (LI) failed to provide any prognostic information with regard to local control or survival. However, the duration of the S phase (Ts) revealed patients whose tumors had a long Ts had significantly worse local control (p = 0.028) and survival (p = 0.034) irrespective of treatment. A similar trend was evident within the different treatment arms particularly associated with overall survival. CONCLUSIONS: The Ts values of head-and-neck squamous cell cancers provided prognostic information that predicted clinical outcome irrespective of treatment schedule in this study. This neglected parameter of the Tpot method might provide information related to redistribution of cells during fractionated radiotherapy.

Analysis of Variance↗

PubMed2003

An image analysis-based approach for automated counting of cancer cell nuclei in tissue sections.

BACKGROUND: Semiquantitative evaluation and manual cell counting are the commonly used procedures to assess positive staining of molecular markers in tissue sections. Manual counting is also a laborious task in which consistent objectivity is difficult to achieve. Recently, image analysis has been explored, but the studies reported were limited to histological images acquired at high magnification and containing uniformly stained cells. METHODS: The analyzed material consisted of histological sections from different squamous cell cancers that had stained for proliferation using Ki-67 and cyclin A detection. The first step of the method was based on detecting the overall number of cells irrespective to their stain, using second-order edge detection methodology. Then proliferating cells were located using principal component analysis (PCA) of the color image, combined with histogram thresholding. RESULTS: The algorithms' performances were validated on tissue section images encountered in routine clinical practice by comparison with objective measures of performance and manual cell identification. The algorithms correlated closely with manual counting of all cells (r(2) = 0.96-0.97) and stained cells (4-7% cell count error). CONCLUSIONS: Cell counting in complex large-scale histological images could be applied in routine practice using edge and color information. The proposed technique provides several benefits, such as speed of analysis, consistency, and automation. Moreover, it is faster than human observation and could replace the laborious task of manual cell counting.

Algorithms↗

PubMed2003

Effect of imidazole on the solubility of a his-tagged antibody fragment.

A number of studies have demonstrated the limited solubility of single-chain Fv antibody fragments and its improvement by genetic engineering. This limits the stability of recombinant protein upon storage and the efficiency of chemical modification. The RAFT3 scFv used in the present work is specific for melanoma-associated proteoglycan and an attractive candidate for clinical radioimaging studies because of its unusual radiolabelling properties. However, when expressed with a c-terminal his(6) IMAC purification tag, the recombinant protein starts to precipitate after column elution and dialysis against PBS and reaches a concentration of soluble protein of approximately 150 microg/mL within a few days upon storage at 4 degrees C. We tested several commonly used buffer modifications (addition of detergents, high salt, amino acids) to improve the solubility and stability of the protein but without any major improvement. However, we found that, when the final dialysis step was omitted and the protein left in IMAC column elution buffer (PBS containing imidazole), it remained soluble. Furthermore, several months old and precipitated protein could be redissolved in this buffer without loss of antigen binding. This observation and the largely pH-independent nature of protein solubility suggest that neither salt bridges formed by the his(6) tail nor cross-linking of his(6) tails mediated by metal ions leached from the column during elution are responsible for the limited solubility of the protein in the absence of imidazole. The presence of imidazole did not interfere with radiolabelling and in vivo tumor targeting in a mouse model. The solubilizing and stabilizing effect of imidazole could be of use for his(6) tagged and poorly soluble recombinant proteins other than scFvs.

Animals↗

PubMed2003

Proliferation rates in human malignant melanoma: relationship to clinicopathological features and outcome.

This prospective study investigated the clinical significance of cell kinetics, measured using bromodeoxyuridine injection and flow cytometry, in primary and metastatic cutaneous malignant melanoma. The findings illustrate that melanoma is a relatively slowly proliferating tumour, with a median potential doubling time (T(pot)) of 8.6 days. There were no significant differences in cell kinetics between primary and secondary disease. Both the duration of the S phase (T(s)) and T(pot), but not the labelling index (LI), showed a correlation with some of the main clinicopathological features in primary disease, including Breslow thickness. On univariate analysis, a short T(pot) and a high LI were associated with shorter disease-free intervals and overall survival for metastatic but not primary lesions. On multivariate analysis, these parameters retained significance when analysed separately with the main clinicopathological variables. These findings suggest that assessment of proliferation in melanoma is able to refine the available prognostic information and identify patients with a poor clinical outcome.

Aged↗

PubMed2003

Use of oncogene expression as an independent prognostic marker for primary melanoma.

For 25 years, the Breslow depth of primary tumors has remained the most accurate prognostic test of survival for primary melanoma. However a number of studies have indicated that outcome for intermediate-thickness melanomas (0.75-2.49 mm) is often at variance with that predicted by the Breslow depth. This study investigated c-myc oncogene expression in 92 primary tumors of intermediate thickness using flow cytometry. Oncoprotein expression was detected in 87 tumors (95%) with a median positivity of 48% (range, 0%-96%). Survival analysis performed using the Kaplan-Meier method revealed a significant association between oncoprotein positivity and clinical outcome (p < 0.01, log-rank test). Multifactorial analysis of survival using Cox's proportional hazards model revealed c-myc oncoprotein to be an independent prognostic marker more accurate than all other clinicopathological parameters including the Breslow depth (chi(2) = 9.68, p< 0.01). Estimation of c-myc oncoprotein is therefore recommended as a powerful prognostic marker for intermediate-thickness primary melanoma.

Biomarkers, Tumor↗

PubMed2002

Tumor hypoxia and blood vessel detection: an image analysis technique for simultaneous tumor hypoxia grading and blood vessel detection in tissue sections.

We have developed a multistage image analysis technique for the simultaneous segmentation of blood vessels and hypoxic regions in dual-stained tumor tissue sections. The algorithm, which is integrated in a task-oriented image analysis system developed on-site, initially uses the K-nearest neighbor classification rule in order to label the image pixels. Classification is based on a training set selected from manually drawn regions corresponding to the areas of interest. If the output image contains a significant number of misclassified pixels, the user has the option to apply a series of specific problem-designed routines (texture analysis, fuzzy c-means clustering, and edge detection) in order to improve the final segmentation result. Validation experiments indicate that the algorithm can robustly detect these biological features, even in tissue sections with a very low quality of staining. This approach has also been combined with other image analysis based procedures in order to objectively obtain quantitative measurements of potential clinical interest.

Algorithms↗

PubMedDate not supplied

Radiation and the cell cycle, revisited.

The cell cycle has been inextricably linked to the cellular response to radiation for many years. However, it is only in the past decade that the concept of a coordinated DNA damage response integrating damage recognition, cell cycle checkpoints and DNA repair has begun to be elucidated. The ATM protein is emerging as a key orchestrator of the damage response activating a wide variety of effectors involved in cell cycle arrest and DNA repair to elicit a concerted effort to prevent genome instability caused by unwanted changes in DNA sequence. The key proteins involved in cell cycle checkpoints in different phases of the cell cycle, and their interaction, is a fertile and rapidly developing area of research. This review summarizes the current state of knowledge of cellular checkpoints in response to radiation-induced double-strand breaks in mammalian cells and how this impacts on radiosensitivity.

Animals↗