Flow-Cytometry in Clinical Cancer-Research

The prognosis of patients with cancer is largely determined by the specific histolÃ3gica! diagnosis, tumor mass stage, and host performance status. The management of neoplastic disease with the currently available treatment armamentarium may be further advanced if individual patients' risk factors could be better de fined. Some of the determinants of tumor response seem to be expressed at the cellular level in terms of degree of tumor cell differentiation, growth kinetics, and hormone receptor expres sion, which are not readily appreciated by descriptive morphol ogy. Quantitative cytology in the form of flow cytometry has greatly advanced the objective elucidation of tumor cell hetero geneity by using probes that discriminate tumor and normal cells and assess differentiate as well as proliferative tumor cell properties. Abnormal nuclear DMA content is a conclusive marker of malignancy and is found with increasing frequency in leukemia (23% among 793 patients), in lymphoma (53% among 360 patients), and in myeloma (76% among 177 patients), as well as in solid tumors (75% among 3611 patients), for an overall inci dence of 67% in 4941 patients. The degree of DNA content abnormality varies according to disease type, with a predominant excess of 10 to 20% in the hematological cancers, whereas ploidy levels in solid-tissue neoplasms span the entire range from almost haploid to hyperoctaploid abnormalities, with near-triploid mean and median DNA content values. The proportion of cells in the S phase of the cell cycle increases with increasing DNA excess in a number of different solid tumors and in acute leukemia. This cytokinetic parameter permits discrimination of lowand high-grade malignant lymphomas. Several reports dem onstrate increasing morphological immaturity to be associated with increasing DNA content abnormality and increasing S per centage, all of which adversely affect prognosis. Among phenotypic tumor cell markers, surface membrane antigens have been extensively studied in lymphoid and myeloid neoplasms by the use of hybridoma-generated monoclonal antibodies, which have recently also found in vitro and in vivo therapeutic application. Cellular RNA content is useful for the objective discrimination of acute leukemias and of multiple myeloma. Newer applications of flow cytometry concern studies in the areas of cytoenzymology and cellular pharmacology. Current research is dedicated to the identification of neoplastic marker probes for DNA-diploid dis ease (e.g., nucleolar antigen) and additional phenotypic (e.g., hormone receptors) and cytokinetic (e.g., cycle traverse rate, growth fraction) parameters. From a patient management perspective, a role for flow cytom1Supported in part by Grants CA16672, CA28153, and CA28771 from the National Cancer Institute, NIH, Bethesda, Maryland 20205. 2To whom requests for reprints should be addressed. Received May 24, 1982; accepted June 8,1983. etry is emerging as a tool for diagnosis of cancer (abnormal DNA content), specific histopathological diagnosis (RNA for hemato logical cancers; surface markers for lymphoid and myeloid neo plasms), prognosis (adverse impact of aneuploidy and high S percentage), and treatment (cytokinetically oriented, monoclonal antibodies, drug pharmacology). The pace of past progress justifies the hope that cytometry may soon provide "fingerprinttype" information of an individual patient's tumor which, if proven prognostically relevant, may provide the basis for treatment selection in the future. Presently, our understanding of neoplastic disease is mainly descriptive. Thus, we still know very little about the factor(s) initiating neoplastic growth, nor can we diagnose the incipient stages of subclinical disease with certainty. Even once macro scopic cancer is established, histopathological description is semiquantitative, not allowing a definitive discrimination, cell by cell, of the malignant versus the normal state within the usually heterogeneous cell population constituting a tumor mass lesion. It is this cellular heterogeneity that, at least in part, may account for the diverse clinical course of comparably staged and treated patients. Recognizing the inadequacy of descriptive morphology for the assessment of tumor cell heterogeneity, several groups have developed automated instruments that are capable of objective and quantitative cell analysis (81, 96,175,183). FCM3 allows high-speed analysis and sorting (1000 cells/sec) according to morphological, molecular, biophysical, and functional cellular features, which can be correlated with each other in multiparameter computer-assisted instruments (51). Essential to all FCM investigation is cell monodispersion, quantitative cell staining, and high-resolution analysis (50). A major requirement for FCM to probe effectively the heterogeneity of human cancer is the unequivocal discrimination of tumor from normal cells, so that the phenotypic diversity of tumor cells and the interaction with neighboring normal cells can be investigated. This report will address the current status of FCM as a tool to unravel the heterogeneity of human neoplastic disease. This will be accomplished by reviewing cellular parameters suitable for cytometric investigation and pertinent to biological features of potential prognostic importance such as cytogenetics (12), dif ferentiation (2,144), and proliferation (13, 20, 35, 52, 57, 67, 87, 115,131). We will provide the reader with a critical evaluation of established and promising new neoplastic, phenotypic, and cy tokinetic FCM markers and point to their potential in the context of cancer biology, diagnosis, prognosis, and therapy. 3The abbreviations used are: FCM, flow cytometry; MSKCC, Memorial Sloan Kettering Cancer Center; ALL, acute lymphoblastic leukemia; MDAH, M. D. Ander son Hospital and Tumor Institute; AML, acute myeloid leukemia; FlTC, fluorescein isothiocyanate; ER, estrogen receptor; DAP), 4'-6-diamidino-2 phenyimdole. 3982 CANCER RESEARCH VOL. 43 on April 13, 2017. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from PCM in Clinical Cancer Research