Abstract: The failure of many anticancer drugs to control growth of solid cancers may stem in part from inadequate delivery to tumor regions distant from vasculature. However, extricating the effect of tissue penetration from the many other factors that affect a drug's efficacy in tumors with distance from vasculature is generally not possible. The present invention relates to an effect-based assay which employs a multilayered cell culture (MCC), a tissue-engineered disc grown from tumor cells on a permeable membrane. One side of the culture may be exposed to a drug or other test substance while the other side is temporarily sealed off. Cells adjacent both the exposed side and the sealed side, of the MCC may then be compared since they have similar rates of proliferation and other biochemical properties. For example, the effect of the drug or other the test substance may be evaluated by immunohistochemical or other labeling techniques.