An improved sum-of-normals technique for cell cycle distribution analysis of flow cytometric DNA histograms

An improved method for determining the fraction of cells in the G1, S and G2 + M phases of the life cycle, from DNA distributions of S phase rich cultures, is presented. Picolinic acid synchronized cell cultures were used to demonstrate the usefulness of the technique for the cell cycle distribution analysis. The algorithm presented quantifies DNA histograms from FCM analyses using an extension of the previously reported 'sum of discrete normal curves' technique. It alleviates problems encountered with earlier methods by extending the contribution of the S phase cells to the distribution under the G1 and G2 + M peaks; at the same time it allows more of the descriptive parameters to be determined from the individual histograms. The fractions of cells in the G1, S, and G2 + M phases of the life cycle obtained by this method compare favourably with autoradiographic analyses and other analytical results.