In the study, the canonical Hist2h2ac was found only in undifferentiated/proliferating cells; Hist2h2ac mRNA was induced by MEK1/2 or PI3-K activation in HC11 and EpH4 mammary epithelial cells and in MC4-L2 and T47-D breast cancer cells. The gene discussed is PIK3CA; the disease is breast carcinoma.