In order to exclude the OCT4-pg4 expression and verify that the OCT4 protein expression is due to OCT4 gene expression, reverse-transcription polymerase chain reaction (RT-PCR) was performed to examine the expression levels of OCT4 gene and OCT4-pg4 in breast cancer tissue with positive OCT4 protein expression detected by IHC. The gene discussed is POU5F1; the disease is breast cancer.