Fig. 1.

An MHCC-97H cell line stably overexpressing miR-21 was selected and cultured in the presence of puromycin (magnification, ×200). a, b Negative control (NC) cultures and cultures stably transfected with miR-21 were mock-transfected in the absence of retroviral particles. c, d Transfected cells were grown for 2 weeks in DMEM containing 1 μg/ml puromycin without other antibiotics. e, f The two cell lines were cultured for 2 months in DMEM containing 500 ng/ml puromycin without other antibiotics. g Relative expression of miR-21 was determined by RT-PCR. *p < 0.05, compared with NC