A rapid system for static cytofluorometry enabling the simultaneous determination of nuclear size and DNA content

NASA/American Cancer Society High-Resolution Flow Cytometry Project-I

BACKGROUND

The NASA/American Cancer Society (ACS) flow cytometer can simultaneously analyze the electronic nuclear volume (ENV) and DNA content of cells. This study describes the schematics, resolution, reproducibility, and sensitivity of biological standards analyzed on this unit.

METHODS

Calibrated beads and biological standards (lymphocytes, trout erythrocytes [TRBC], calf thymocytes, and tumor cells) were analyzed for ENV versus DNA content. Parallel data (forward scatter versus DNA) from a conventional flow cytometer were obtained.

RESULTS

ENV linearity studies yielded an R value of 0.999. TRBC had a coefficient of variation (CV) of 1.18 +/- 0.13. DNA indexes as low as 1.02 were detectable. DNA content of lymphocytes from 42 females was 1.9% greater than that for 60 males, with a noninstrumental variability in total DNA content of 0.5%. The ENV/DNA ratio was constant in 15 normal human tissue samples, but differed in the four animal species tested. The ENV/DNA ratio for a hypodiploid breast carcinoma was 2.3 times greater than that for normal breast tissue.

CONCLUSIONS

The high-resolution ENV versus DNA analyses are highly reliable, sensitive, and can be used for the detection of near-diploid tumor cells that are difficult to identify with conventional cytometers. ENV/DNA ratio may be a useful parameter for detection of aneuploid populations.

Cytophotometric DNA-analysis of bone-tumors. A new method for preparing formalin-fixed tissue and the regarding of DNA-malignancy grade and its prognostic value

78 benign and malign, formalin-fixed bone or bone-associated tumors of different origin were prepared for image-cytophotometric measuring with a new method of preparing. The DNA-content of the tumors and the so resulting malignancy-grade were determined and compared with the corresponding measurements of unprepared fresh tumors respectively paraffin-embedded tissue sections. Regarding the comparison of the fresh material with the formalin-fixed material, no significant difference (p < or = 0.01) of the data could be found. There was also no significant difference (p < or = 0.01) concerning the comparison of the data obtained from the formalin-fixed material and the data from the tissue sections. The criterium aneuploidy showed a sensitivity of 86% and a specificity of 100% in regards to identifying a malignant tumor, irrespective of the preparation method. A strong correlation could be found (p < 0.001) between the DNA-malignancy grade and the survival rate of the patients.

Intraepithelial neoplasia, surrogate endpoint biomarkers, and cancer chemoprevention

Neoplasia is a progression of molecular, cellular, and tissue changes starting with a critical cell mutation and advancing by clonal evolution, involving further multiple mutations and expanding mutated clones. This process is characterized by five general stages: latency, focal growth of normal-appearing but disorganized cells, abnormal-appearing cells (dysplasia), microinvasion, and finally, metastasis. The two driving forces of neoplastic progression in an epithelium are mutagenesis and mitogenesis. These forces frequently occur concurrently, produced by exposure of the epithelium to environmental and endogenous mutagens and mitogens. The major strategy of chemoprevention is to block the effects of both mutagens and mitogens during the early stages of predysplasia and dysplasia. Surrogate endpoint biomarkers (SEBs) are tissue, cellular, and molecular changes that correlate with the later development of cancer. Because of the savings in cost, labor, and time, SEBs are urgently needed to replace the use of cancer incidence reduction as the endpoint for chemopreventive agent clinical trials. The advent of computer-assisted cytometry allows each of the seven basic criteria of dysplasia to be individually assayed as an SEB. Since the dysplastic changes that characterize intraepithelial neoplasia are embodied in the causal pathway to invasive neoplasia, they are already validated as predictors of cancer incidence. More attention should be paid to the quality control of SEB assays, including control of variation in cell composition of tissue samples, assay protocol, instrumentation used, and observer performance. The dose-response relationship between a known chemopreventive agent and the SEB should also be evaluated. The Division of Cancer Prevention and Control, National Cancer Institute, has begun a program to test chemopreventive agents in short-term Phase II clinical trials using dysplasia-based SEBs. The SEBs are assayed, when possible, by computerized cytometry. Trials are being conducted for oral leukoplakia, cutaneous actinic keratosis, superficial bladder cancer, pulmonary metaplasia/dysplasia, cervical dysplasia (CIN III), and adenomatous colonic polyps.

Variations in Feulgen stainability of epithelial parenchymal cells extracted from paraffin-embedded salivary gland specimens

The variations of Feulgen stainability of cells extracted from paraffin-embedded archival specimens for DNA assessment by means of image cytometry (ICM) were investigated in normal salivary gland parenchyma. The Feulgen stainability of the deparaffinized, rehydrated, and disaggregated preparations was found to exhibit variations of up to 300%, expressed by the mean of integrated optical density (IOD), when a routine procedure was applied to a first series of Cytospin preparations of disaggregated specimens. When measured in nondisaggregated tissue sections, only negligible variations were observed. After minimization of the mechanical strains to the cellular material in the Cytospin preparations in a second series, the variations in Feulgen stainability were found to be considerably lower. The findings indicate that the main reason for variations in the Feulgen stainability of extracted cells is, most likely, the disaggregation procedure itself. Factors such as initial treatment of the specimens, duration and kind of formalin fixation, and length of storage time periods seem to be of minor importance. Retrospective studies on paraffin-embedded specimens require a carefully controlled tissue type-adapted disaggregation procedure. In addition, we concluded that the interpretation of histograms, obtained by means of ICM DNA assessments in Cytospin preparations of archival material, requires a well-defined internal specific standard.