CXCR4 and cancer: Thus, treatment with miR-139 inhibitor (anti-miR-139) in pLKO-miR-139-transduced MD-MBA-231 cancer cells restored their stemness characteristics, such as spheroid cell aggregation, colony formation in soft agar, and cell attachment behavior; these features indicating increased stemness were abrogated on silencing the CXCR4 gene (shCXCR4) (Figure 5A).