Regarding the effect of TMPRSS4 on cancer cell cycle, our results showed that TMPRSS4 silencing in MDA-MB-468 breast cancer promotes the cell cycle arrest in G2/M phase associated to the reduction of the cell cycle arrest in S phase while induction of the TMPRSS4 overexpression in MCF-7 breast cancer cell has no significant effect on cell cycle process. The gene discussed is TMPRSS4; the disease is cancer.