Abstract: Objective To assess the effect of small interfering RNA (siRNA)-mediated suppression of CDK6 expression on the
proliferation and cell cycles of nasopharyngeal carcinoma (NPC) cells in vitro. Methods QRT-PCR was used to examine the
differential expression of CDK6 in 30 NPC tissues and 18 normal nasopharyngeal tissues. A siRNA targeting CDK6 was
transfected in NPC CNE2 cells, and MTT assay and flow cytometry were used to analyze the changes in cell proliferation and
cell cycle distribution. Western blotting was used to examine the expressions of the cell cycle-related factors. Results
Compared with normal nasopharyngeal tissues, NPC tissues showed an increased expression of CDK6 mRNA. Knocking
down CDK6 expression obviously inhibited tumor cell growth and cell cycle transition from G1 to S phase and caused reduced
expressions of CDK4, CCND1, and E2F1 and enhanced expression of the tumor suppressor p21. Conclusion NPC tissues
overexpress CDK6. Knocking down CDK6 expression inhibits the growth and cell cycle transition of NPC cells in vitro by
inhibiting the expressions of CDK4, CCND1, and E2F1 and upregulating tumor suppressor p21 expression.