The growth effects of PIP on human OSCC cell lines. (a) After transfection with control vector, PIP vector or siRNA‐PIP, the image of 500 cells were severally plated in a six‐well plate for 12 days; the average colony number of per well. All data were shown as mean ± SD. *p < 0.05, **p < 0.01. (b) At 24, 48, and 72 hr after transfection with control, PIP vector or siRNA‐PIP, cell proliferation was examined by the MTT assay. All data were shown as mean ± SD. *p < 0.05, **p < 0.01. (c) The relative proportion of SCC15 and SCC25 cell cycle, after transfection with control vector and PIP vector. All data were shown as mean ± SD. *p < 0.05, **p < 0.01. MTT: 3‐(4,5‐Dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide; OSCC: oral squamous cell carcinoma; PIP: prolactin‐inducible protein; SD: standard deviation; siRNA: small interfering RNA [Color figure can be viewed at wileyonlinelibrary.com]