Description:
AbstractThe aims of this study were to develop a protocol for the identification and enrichment of cancer cells from sputum obtained from patients with adenocarcinoma of the lung (n = 6) and large‐cell undifferentiated carcinoma of the lung (n = 2), and to compare these findings with the results from our previous studies on other cell types from lung cancer. The hypotheses tested were: (1) Cancer cells in sputum can be preserved following flow sorting. (2) Enrichment for cancer cells from acridine orange (AO)‐stained specimens can be achieved. (3) Discrimination of cancer cells from noncancer cells is by AO green fluorescence and discrimination of lymphocytes from other cell types is by AO red fluorescence. (4) Cancer cells are consistently enriched in the AO high green and red fluorescence region, although, for a given cell type, maximal enrichment is patient‐dependent. (5) Finally, cancer cell enrichment and lymphocyte exclusion can be done simultaneously.Cells from sputum were initially fixed, stained with AO, sorted on a dual parameter flow sorter, and classified into six groups corresponding to two ranges of green and three ranges of red fluorescence intensities. Cells of each region were stained by the method of Papanicolaou and differential counts were performed to determine the relative frequencies (i.e., purities) of leukocytes, macrophages and unsorted (i.e., control) samples.The average purity of leukocytes (81%), macrophages (6%), squamous cells (11%), and cancer cells (2%) varied markedly from sample to sample. However, the largest enrichment values (i.e., ratio of purity of a cell type in a sorted sample to its purity in the unsorted control sample) achieved for cancer cells consistently occurred for each patient sample in the region corresponding to high green and high red fluorescence intensities. Experimentally, a cancer cell average enrichment of sixteen‐fold was obtained by this method. Additionally, fluorescence intensity ranges which increased the enrichment for macrophages by cell sorting typically excluded leukocytes and squamous cells, and vice versa. Finally, red fluorescence intensity was the primary discriminatory parameter for all cell types studied, although the additional use of green fluorescence intensity significantly increased cancer cell enrichment rates.In conclusion, sputum samples can be enriched for atypical and malignant cells, cells from these samples can be well preserved following machine processing, and sputum samples from patients with adenocarcinoma of the lung and large‐cell undifferentiated carcinoma have similar enrichment and preservation results to samples obtained from other types of lung cancer.