The type of histogram data and its analysis discussed in Chapter 8 can yield the proportions of cells in the various cell-cycle phases and the relative durations of the phases only if there is exponential growth and all the cells are within the division cycle. This is not kinetic information, even though some publications might lead one to believe that it is. Kinetic information can be obtained only when a perturbing event or second marker is introduced into the steady state and where the effects thereof are followed temporally. Analysis of the decay of the introduced event with time yields the kinetic information. There are two basic types of such perturbed DNA histogram. The first is due to an alteration in the steady-state age distribution with partial synchrony of the population. The second is more subtle, where a specific marker for S phase is introduced without altering the steady-state age distribution of the population.

Stathmokinetic techniques

An alteration of the steady state of growth may be induced by addition of drugs or radiation which block or delay the population in a specific phase of the cell cycle. Addition of colcemid, which depolymerises tubulin in microtubules, induces metaphase arrest as cells cannot proceed to anaphase. Figure 9.1 shows DNA histograms of a human breast cancer–cell line before (panel A) and after (panel B) treatment with colcemid, where the accumulation of cells in G2+M is obvious.