Objective: To investigate the expression ofP-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) and the relationship with cell cycle profiles in ovarian cancer SK-OV-3ip1 multicellular aggregates. Methods: Liquid overlaysystem was employed to obtain multicellular aggregates. Expression of P-gp and MRP was detected with flowcytometry (FCM). Outer, intermediate and inner cellsfrom multicellular aggregates were collected bylayer-trypsinized method. Cell cycle profiles were also analyzed by FCM. Results: Compared with control cells, no expression of P-gp and MRP was detected inmonolyer cells (P=0.128 and P=0.604), but expression of P-gp and MRP in aggregate cells was significantlyelevated (P<0.01). P-gp expression in every layer cellswas also obviously increased (P<0.01). Furthermore,P-gp expression in every layer cells was also obviously increased (P=0.071). Tendency to increased G0-G1 phase and reduced S phase cells existed from outer throughintermediate to inner layers in multicellular aggregates but with no statistical difference. Cell percentages inG2-M phase also had no difference. However, compared with monolayer cells, cells in G0-G1 phase increased and cells in S and G2-M phases lowered significantly inevery layer and in the whole multicellular aggregates. Expression elevation of P-gp and MRP was consistent with increased G0-G1 percentage in aggregate cells.Conclusion: Expression of P-gp and MRP increases in cells of SK-OV-3ip1 multicellular aggregates and isconsistent with increased G0-G1 percentage, which implies the possible relationship between them and the possible role in multicellular-mediated drug resistance. Objective: To investigate the expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) and the relationship with cell cycle profiles in ovarian cancer SK-OV-3ip1 multicellular aggregates. Methods: Liquid overlay system was employed to obtain multicellular Aggregates. Expression of P-gp and MRP was detected with flowcytometry (FCM). Outer, intermediate and inner cells from multicellular aggregates were collected by layer-trypsinized method. Cell cycle profiles were also analyzed by FCM. Results: Compared with control cells, no expression P-gp and MRP was detected in monolyer cells (P=0.128 and P=0.604), but expression of P-gp and MRP in aggregate cells was significantlyelevated (P<0.01). P-gp expression in every layer cells was also significantly increased. (P<0.01).,P-gp expression in every layer cells was also significantly increased (P=0.071). Tendency to increased G0-G1 phase and reduced S phase cells existed from outer throughintermediate to inner layer s in multicellular aggregates but with no influx difference. Cell percentages inG2-M phase also had no difference. However, compared with monolayer cells, cells in G0-G1 phase increased and cells in S and G2-M phases decreased significantly inevery layer and in The whole multicellular aggregates. Expression elevation of P-gp and MRP was consistently with increased G0-G1 percentage in aggregate cells.Conclusion: Expression of P-gp and MRP increases in cells of SK-OV-3ip1 multicellular aggregates and isconsistent with increased G0 -G1 percentage, which implies the possible relationship between them and the possible role in multicellular-mediated drug resistance.