S100A6 and neoplasm: Additional reasons for the age effects of MEPT on tumor development may include changes in estradiol, progesterone, and other reproductive hormone levels, their receptor expression (i.e., the loss of the higher PRA expression in aged MEPT mice, Figure 6D), and other age-related reproductive changes, such as in estrous cycling and fecundity, which may be occurring before 8.6 months.