FIGURE 3 from Metronomic Administration of Topotecan Alone and in Combination with Docetaxel Inhibits Epithelial–mesenchymal Transition in Aggressive Variant Prostate Cancers
Metronomic topotecan in combination with DTX showed potency against prostate cancer subtypes, ARLow/mCRPC/NEPC (PC-3, PC-3M, DU145) and ARLow/mCSPC/NEPCtaxane resistant (DUTXR) cells. Cytotoxicity: In vitro effect of metronomic and conventional administration of topotecan on prostate cancer cell lines was assessed. A, MTT assay: Cytotoxicity was measured following 72 hours of CONV-TOPO, CONV-DTX, METRO-TOPO, and the combination of CONV-DTX+METRO-TOPO treatment in PC-3, PC-3M, DU145, DUTXR cell lines using mitochondrial activity [3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] or the MTT assay. In all cell lines, METRO-TOPO (lower dose) reduced cell growth more compared with CONV (high dose) treatment at IC50/2. The greatest reduction in cell growth was observed following CONV-DTX + METRO-TOPO combination treatment in all prostate cancer cell lines tested (*, P ≤ 0.05). B, Apoptosis (caspase 3/7 assay): Levels of caspase 3/7 enzyme (a marker of apoptosis) activities measured followed CONV-TOPO, CONV-DTX, METRO-TOPO, and the combination of CONV-DTX + METRO-TOPO 72 hours treatment. Results showed significant increases in caspase 3/7 activity following each treatment compared with control. Results confirmed significantly greater treatment-induced apoptosis was observed for post-METRO-TOPO treatment compared with CONV-TOPO and DTX. The highest treatment-induced apoptosis was observed in combination with CONV-DTX+METRO-TOPO in all cell lines (*, P ≤ 0.05). C, Microscope images (Cytation5): Cell morphologic study reported micrographs of prostate cancer cells exposed to all dosing regimens showed decreases in cell density compared with control cells. Results showed that METRO-TOPO reduces higher cell density compared with CONV-TOPO and CONV-DTX. Highest cell death observed in CONV-DTX+METRO-TOPO combination treatment compared with CONV-TOPO, CONV-DTX, and METRO-TOPO single-drug treatment (*, P ≤ 0.05).