On the limits of enhancement in human gene transfer: drawing the line

Enhancement-line human genetic engineering has recurrently been targeted for bioethical discussion and is usually (if not always) illustrated by examples alluding to a genetic technology that is far beyond our current possibilities. By discussing an ambitious project related to solid tumor cancers--multidrug resistance (MDR)--the present paper places the question on a more realistic plane and draws bioethical conclusions to serve as guidelines in the field. The paper also establishes the inadequacy of the prevalent concept of genetic medicine as one of substitution.