Effects of DHEA and DHEA8354 on the cell cycle. (a-c) Cell cycle distribution in MNU-induced mammary tumor of a control animal (a) and in an animal treated with dehydroepiandrosterone (DHEA) (b,c). Control tumors showed a low level of S-phase cells and a lack of cells with hypodiploid values of DNA. DHEA treatment induced an increase in apoptotic cells (b, arrow) and a decrease in G2M phase. A cell population is identified with DNA values after the G1/G0 peak (c, arrow), suggesting DNA abnormalities typical for senescent cells from another mammary tumor from an animal treated with DHEA. (d) DHEA induced both apoptosis and senescence (a small area after the G1/G0 peak (arrow), indicative of senescence.