Objective      To investigate the effect of mitochondrial ribosomal protein S5 (MRPS5) on proliferation and stemness of human bladder cancer cells.       Methods      The expression of MRPS5 protein in human bladder cancer tissues and adjacent normal tissues was detected by Western blotting. Lentiviral vector targeting MRPS5 was constructed to infect bladder cancer cell line T24

and lentiviral vector with scramble sequence was used as control. The MRPS5 interference efficiency was analyzed by Weste

rn blotting. The cell proliferation was detected by cell viability assay. Cell cycle was measured by flow cytometry. Sphere forming ability was observed by sphere formation experiment. The expression of cancer stem cell related transcription factors (Nanog

Oct4

c-Myc and Sox2) was detected by Western blotting. Subcutaneous transplantation tumor experiment of NOD/SCID mice was used to reflect in vivo tumorigenicity.       Results      The expression of MRPS5 protein in the bladder cancer tissues was higher than that in the adjacent normal tissues. Lentiviral vector PLKO.1-shMRPS5 was effective for interference to MRPS5 expression. After interference

T24 cell proliferation was decreased (P0.05)

and the cell cycle was arrested in S phase. Meanwhile

the expression of Nanog

Oct4

c-Myc and Sox2 proteins was all decreased

and the sphere forming ability was not changed (P0.05)

but the sphere sizes were significantly decreased. In addition

the in vivo tumor volume (0.784±0.278 vs 0.500±0.245 cm

3

P0.05) and weight (0.862±0.372 vs 0.412±0.248 g

P0.05) were decreased.       Conclusion      MRPS5 protein is highly expressed in bladder cancer tissues

and the interference to MRPS5 expression can inhibit the proliferation and stemness of T24 cells.