The prognostic value of DNA content analysis in patients with squamous cell lung cancer treated surgically

Revisiting tumour aneuploidy - the place of ploidy assessment in the molecular era

Chromosome instability (CIN) is gaining increasing interest as a central process in cancer. CIN, either past or present, is indicated whenever tumour cells harbour an abnormal quantity of DNA, termed 'aneuploidy'. At present, the most widely used approach to detecting aneuploidy is DNA cytometry - a well-known research assay that involves staining of DNA in the nuclei of cells from a tissue sample, followed by analysis using quantitative flow cytometry or microscopic imaging. Aneuploidy in cancer tissue has been implicated as a predictor of a poor prognosis. In this Review, we have explored this hypothesis by surveying the current landscape of peer-reviewed research in which DNA cytometry has been applied in studies with disease-appropriate clinical follow up. This area of research is broad, however, and we restricted our survey to results published since 2000 relating to seven common epithelial cancers (those of the breast; endometrium, ovary, and uterine cervix; oesophagus; colon and rectum; lung; prostate; and bladder). We placed particular emphasis on results from multivariate analyses to pinpoint situations in which the prognostic value of aneuploidy as a biomarker is strong compared with that of existing indicators, such as clinical stage, histological grade, and specific molecular markers. We summarize the implications of our findings for the prognostic use of ploidy analysis in the clinic and for the theoretical understanding of the role of CIN in carcinogenesis.

Fluorescent stains for quantification of DNA by confocal laser scanning microscopy in 3-D

Confocal microscopy requires the use of fluorophores to visualize structures of interest within a specimen. To perform reliable measurements of the intensity of fluorescence, the stain should be specific, penetrate well into tissue sections, and bind stoichiometrically. Furthermore, emission must be linear with respect to DNA content and brightness, and fluorescence should be stable. Confocal microscopy is used to determine DNA ploidy and to analyze texture of nuclei, which is accomplished in three dimensions, because nuclei can be measured within the original tissue context. For this purpose the sample must be stained with a DNA binding fluorophore with the properties described above. Stains with different properties have been developed for different applications. We review here the advantages and disadvantages of these different stains for analyzing DNA ploidy and nuclear texture using three-dimensional microscopy. We conclude that SYBR green I and TO-PRO-3 are the most suitable stains for this purpose at present.

Prognostic value of DNA ploidy: 5-year follow-up of patients with resectable squamous cell carcinoma (SCC) of the lung

This study was designed to show the relation between DNA-ploidy in patients with resectable lung cancers and their 5-year survival rate. The results are compared with those from our 2-year follow-up study of the same group of patients published in 2000. The group of 80 patients with SCC who underwent lung resection between 1995 and 96 were re-analyzed. For the statistical analysis the hazard Cox model and an exponential multiple regression model were used. The survival curves were drawn using the Kaplan-Meier method. DNA-aneuploidy was found in 45% of cancer tumors. There was no statistically significant correlation between aneuploidy and gender, age, cancer staging or grading. In the 3-year follow-up the survival rate in patients with aneuploid type tumors was significantly lower than in those with the diploid type. However, this difference was not found after 5 years of follow-up. Tumor ploidy was an independent prognostic factor only in patients between 55 and 60 years of age. The mortality rate in patients with aneuploid tumors was mainly the result of distant metastases while, in patients with diploid tumors, local recurrence was the main reason for death. In the first three years after surgical resection patients with aneuploid tumors are at higher risk of distant metastases than patients with the diploid type. Tumor ploidy can be recognized as an independent prognostic factor in younger (55-60) patients. Aneuploidy promoted the occurrence of early distant metastases while the diploid type was associated with late (after 3 years) local tumor recurrence.

Interpretation with hindsight

In his 1965 paper 'DNA content of tumours: cytophotometric measurements', Sandritter was for the first time able to relate tumour DNA content to the pathology and progression of a small number of tumours. In subsequent publications, these observations were extended to the progression of a much more comprehensive range of tumours. The interpretation of Sandritter's paper below follows the increasing sophistication of methodologies for tumour DNA content through the existing publications and evaluates the conclusions and hypotheses Sandritter proposed in the light of the contemporary account.