Doxycycline induces apoptosis via ER stress selectively to cells with a cancer stem cell-like properties: importance of stem cell plasticity

a Immunofluorescence staining of CD44v9 and E-cadherin in monolayer and sphere-forming PC-3 cells. Scale bar？=？10？μm. b CD44v8-10 and CD44s mRNA expression in monolayer and sphere-forming cells were performed by RT-PCR. c Immunoblotting analysis of E-cadherin, c-MYC, Bcl-xL and β-tubulin protein in the change of monolayer cells (3 days) to sphere-forming cells (3 days). M indicates monolayer, S indicates sphere-forming. d Relative mRNA expression of CSC marker in the change of monolayer (3 days) to sphere forming cells (3 days). Data were normalized to the expression level in monolayer for each RNA species. M indicates monolayer cells, S indicates sphere-forming cells. Data shows the mean？±？SD of triplicates. *p？<？0.05. e Relative cell number using MTS assay for monolayer and sphere-forming cells treated with 100？nM paclitaxel and 10？nM docetaxel for 3 days. Data were normalized to the absorbance level in monolayer for each species. Data shows the mean？±？SD of triplicates. **p？<？0.01. f OCR was measured using the Seahorse XF24 analyzer for monolayer and sphere-forming cell. Oligomycin, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), rotenone, and antimycin A (AA) were added at the same time point for each experiment. Data shows the mean？±？SD of quadruplicates. *p？<？0.0