In this latter case, it has become increasingly clear that FKBP12 plays an important role in tumor genesis; for example, the expression of FKBP12 is the rate limiting factor that determines the responsiveness of a cell line or tissue to the anticancer drug rapamycin [13] and in general to FKBP12 inhibitors [14]. Here, FKBP1A is linked to neoplasm.