Many anti‐cancer drugs work by inducing DNA damage in rapidly dividing cancer cells.28 Phosphorylated H2AX (γ‐H2AX), a phosphorylated variant of histone 2A, is a well‐known biomarker of DNA double‐strand breaks, which initiate the DNA damage response in mammalian cells.29 With DNA damage, formation of γ‐H2AX foci increases in the nucleus. The gene discussed is H2AX; the disease is cancer.