Epithelial cell enrichment and defined dose–response curve patterns. Epithelial cell enrichment by density gradient centrifugation. (A) Crude cells from ascites taken from a patient with peritonitis carcinomatosa. (B) Epithelial cells were enriched by density gradient centrifugation. Six different drug dose–response curve patterns (C): The left top panel represents a logistic curve where sample cell growth is dominantly regulated by the drug concentration. The middle top panel represents a hyperbolic curve in which the drug does not suppress cell growth at all practical drug concentrations. Horizontal and vertical axes represent drug concentration and cell viability, respectively.