Moreover, a dual function of CCAT2 in regulating tumorigenesis and cancer cell stemness in luminal breast cancer was determined in the current study, in which the cytoplasmic CCAT2 interacted with miRNA 221/222 to interfere with p27-dependent cell proliferation, while CCAT2 accumulation in the nucleus interacted with a pseudogene of OCT4 (OCT4-PG1) to induce cancer stem cells. This evidence concerns the gene POU5F1 and breast cancer.