Flow Cytometry in the Diagnosis of Brain Tumors

Application of flow cytometry in pediatric hematology-oncology

Applications of flow cytometry in pediatric cancers have expanded substantially in recent years. In acute leukemias, the commonest childhood cancer, flow cytometry can now define complex antigenic profiles that are associated with specific cytogenetic/molecular defects and can also directly identify BCR-ABL fusion protein. Flow cytometry based scoring system has been described for diagnosis of myelodysplastic syndromes. In solid tumors, flow cytometry was previously used mainly to determine DNA content for prognosis; however, recent studies in children with neuroblastoma and Ewing sarcoma have identified its diagnostic utility. In this review, we will discuss the current and future applications of flow cytometry in pediatric hematology-oncology.

Flow-cytometric DNA analysis of intracranial tumors in children

The objective of this study was to investigate flow-cytometric DNA values of pediatric intracranial tumors, and to establish DNA analysis as a potential prognostic parameter. Twenty-nine brain tumor specimens from 26 pediatric patients were cryo-preserved within a 3-year period. The DNA content was measured by flow cytometry. Six of the tumor specimens had aneuploid DNA patterns. The median of the proliferation index was lower in the survivor group compared with the non-survivor group (36.4% and 47.5%, respectively). Ten of the 26 patients are still alive, eight were lost to follow up, and eight died. Flow-cytometric DNA analysis may be a helpful tool for examining brain tumors in children. The small size of this study could not establish flow cytometry as a definite prognostic factor, but further prospective multicenter studies will evaluate the prognostic significance of flow-cytometric DNA analysis.

The use of flow cytometry in assessing malignancy in bone and soft tissue tumors

Since 1982, the orthopaedic research laboratories at the authors' hospital has done flow cytometric and more recently cytofluorometric deoxyribonucleic ploidic analyses of samples of bone and soft tissue tumors. The current authors attempt to define the value of such studies in distinguishing benign from malignant tumors, in conforming to stage of the tumors, and in helping to predict metastasis and death. The series consists of 1134 patients in whom the disease was verified and the survival data were available as a result of a questionnaire study. Statistically, the ploidic analyses were of remarkable value in defining malignancy and in correlating with the stage of the lesion. They were of less value in predicting survival, particularly for patients with osteosarcoma and chondrosarcoma, but seemed to predict survival effectively for patients with soft tissue sarcomas.

DNA ploidy and cell-cycle analysis in intracranial meningiomas and hemangiopericytomas: a study with high-resolution DNA flow cytometry

Although various DNA flow-cytometric studies have been performed on meningiomas, the role of DNA ploidy and the S-phase fraction (SPF) in predicting biological tumor behavior remains unresolved. Discrepant results in earlier studies might be due to different preparing, staining and measuring techniques; different quality standards; and lack of sophisticated computer software. In this study, high-resolution DNA flow cytometry using the DNA-specific dye DAPI (4', 6'-diamidino-2-phenylindol) was performed on stored frozen tissue from 128 microsurgically resected meningiomas and 7 hemangiopericytomas, including 17 recurrent meningiomas and 4 recurrent hemangiopericytomas. The computer software Multicycle 2.5 was used to determine the ploidy level and to perform cell-cycle analysis. DNA aneuploidy and SPF were significantly higher in atypical, anaplastic and recurrent meningiomas and correlated well with histopathological features such as focal necrosis, infiltration of dura mater and mitotic activity. Among 128 meningiomas, 42 had additional DNA aneuploid stem lines. No association between hypo- and hyperploidy and either histological subtype or clinical outcome was found. In 7 hemangiopericytomas, SPF was significantly higher compared to the benign meningioma group, while only 1 tumor was aneuploid. In all 42 DNA aneuploid tumors, cell-cycle analysis was performed separately for the euploid and aneuploid stem lines. The proliferation parameters (SPF, G2/M phase) were significantly higher in the DNA aneuploid stem lines. DNA ploidy and SPF are thus useful indicators of different biological behavior within identical histological subgroups in meningiomas.

Molecular characterization of glioblastoma cell differentiation

OBJECTIVE

Induction of cellular differentiation continues to be an attractive therapeutic strategy for malignant glioma. The purpose of this study was to develop a convenient in vitro model system for glioblastoma differentiation and to then characterize it using conventional techniques and flow cytometry.

METHODS

A subline of U138 MG cells ("U138B") was treated with 0 to 4 mmol/L sodium butyrate (or serum deprivation) for up to 96 hours. Cells were initially studied for effects on proliferation, morphology, and glial fibrillary acidic protein (GFAP) staining. Northern blot and immunoblot analyses of c-myc expression were performed. Multiparameter flow cytometry was then used to analyze GFAP, c-myc protein, and total cellular protein fluorescence and to relate them to changes in cell cycle distribution.

RESULTS

Butyrate treatment produced a dose-dependent inhibition of cellular proliferation and changes in morphology, GFAP staining, and c-myc expression consistent with a differentiation response. Detailed flow cytometric studies, including subpopulation analysis, showed that during 72 hours of treatment with 2 mmol/L butyrate, mean GFAP fluorescence increased to 420%, whereas c-myc protein decreased to 45 +/- 13% and total cellular protein increased to 181 +/- 17%. The effects of butyrate were distinct from those of serum deprivation and were not simply the result of cells shifting into Gzero/G1.

CONCLUSION

The butyrate-induced responses of the U138B cell line provide a convenient model system for studying the molecular events accompanying the differentiation of glioblastoma cells. Multiparameter flow cytometry is a useful technique for characterizing such differentiation.

Primary intracerebral small lymphocytic non-Hodgkin's lymphoma with plasmacytoid differentiation, associated with prominent extracellular proteinaceous deposits

A case of primary intracerebral non-Hodgkin's lymphoma in a 67-yr-old immunocompetent female is presented. The histopathological diagnosis was supported by immunohistochemical, flow cytometric and electron microscopic findings, and by clinical staging. This tumor is unusual in its morphological features of a low grade, small lymphocytic lymphoma with plasmacytoid differentiation (Working Formulation Classification), and its association with extensive, local, extracellular, proteinaceous deposits. Primary central nervous system non-Hodgkin's lymphomas are briefly discussed and it is postulated that the extracellular proteinaceous deposits in this case originated from immunoglobulins secreted by the neoplastic cells. To our knowledge the massive degree of local immunoglobulin deposition present in this primary central nervous system lymphoma has not been previously reported in the literature.

Purification of cell populations from human fetal brain using flow cytometric techniques

We recently established primary cultures from dissociated second trimester human fetal brains using a novel spin seeding method and characterized cellular populations with distinct phenotypes in these cultures. Here, we report that these neural cultures can be dissociated to single-cell suspensions, sorted by size using flow cytometry and re-seeded to yield cultures selectively enriched for the neuronal and glial cell populations. Sorted neurons were highly homogeneous, viable and extended processes, by one day after re-seeding. These neurons expressed immunoreactivity for neurofilament protein, retained their GABAergic phenotype and were electrically excitable. Re-seeded astrocytes proliferated in culture and expressed glial fibrillary acidic protein. We describe the conditions required for the flow cytometric sorting and tissue culture assays as well as the morphological, immunocytochemical and electrophysiological characteristics of the sorted neuronal population.