The loss of miR-21 expression by anti-miR-21 transfection resulted in decreased expression of VEGF, CD44, EpCAM, and decreased CSC self-renewal capacity in PC cells derived CSC-like sphere-forming cells under hypoxic conditions, which clearly suggest that hypoxia-induced miR-21 expression may play a pivotal role within the tumor microenvironment, contributing to the promotion of tumor aggressiveness. The gene discussed is CD44; the disease is neoplasm.