Anaphase-promoting complex/cyclosome (APC/C) is a key E3 ubiquitin ligase in cell division, which catalyses ubiquitination of cell-cycle regulators. Studying this complex could reveal important information regarding its application in cancer research and therapy. In this study, 4 synthesized small interfering RNAs (siRNAs) were transfected into HEK293T cells to suppress messenger RNA (mRNA) of Apc11; 2 of these reduced the amount of Apc11 mRNA by over 50%. Further experiments showed that rather than causing apoptosis, siRNA transfection led to cell-cycle distributions characterized by less time spent in G2/M phase and more time spent in G1 phase. This phenomenon was specifically induced by Apc11 silencing, as co-transfection of siRNA and an Apc11 plasmid could reverse this distribution bias. Our results suggested that siRNA targeted against Apc11 could hamper entry into G2/M phase. Current efforts are focused on elucidating the function and utility of the APC complex for clinical applications.