A Flow Cytometric Cell-cycle Assay Using Methyl Green.

Abstract Methyl green (MG), a conventional, low-cost histological stain, was used to design a flow cytometric cell-cycle/DNA-ploidy assay. On fluorometry, MG absorbed maximally at 633-nm, showed negligible fluorescence in free-state, but emitted brightly when bound to DNA. Optimal dye and cell concentrations for staining and effects of time and photobleaching on stained cells were determined for a lyse-permeabilize-stain protocol. Linearity of DNA-binding, coefficients-of-variation of G0/G1-peaks and minimal carryover were confirmed. Assay results correlated highly with a propidium iodide-based kit in 29 acute lymphoblastic leukemia specimens. The MG-based DNA-ploidy assay represented an accurate and inexpensive alternative to conventional PI-based assays.