OBJECTIVETo explore the effect of RNA interference of human I2PP2A gene on the proliferation and apoptosis of retinoic acid-resistant human acute promyelocytic leukemia (APL) cell line NB4-R1.

METHODSDesigned and constructed a RNA interference lentiviral vector I2PP2A-shRNA which targeted against I2PP2A gene, then transfected it into NB4-R1 via polybrene mediation. The I2PP2A expression levels before and after transfection were detected by qRT-PCR and Western blot, respectively. Meanwhile, the proliferation and apoptosis rates of each group were determined by CCK-8 and flow cytometry assay. The protein expressions of caspase-8 and PARP were detected by Western blot.

RESULTSBoth qRT-PCR and Western blot data showed the I2PP2A expression level was significantly downregulated in the transfection group. The I2PP2A mRNA expression level decreased by (70.0 ± 9.6)% and (64.0 ± 6.2)% respectively, compared with blank control and negative control group, and the I2PP2A protein expression level showed a consistent trend. CCK-8 proliferation assay indicated the NB4-R1 cell proliferation rate in I2PP2A-shRNA transfection group significantly reduced compared to blank control group (P<0.05). Flow cytometry results showed that NB4-R1 apoptosis rate in I2PP2A-shRNA transfection group increased by (6.30 ± 0.67) times and (6.04 ± 0.56) times, respectively (P<0.01). After inhibition of I2PP2A, the total caspase-8 and total PARP expressions decreased by (44.0 ± 3.1)% and (57.0 ± 4.0)%, respectively; Meanwhile, the cleaved caspase-8 (p43) and cleaved PARP (p89) increased by (36.0 ± 2.5)% and (45.0 ± 4.8)%, respectively compared with blank control group (P<0.05).

CONCLUSIONI2PP2A gene silenced by RNA interference could inhibit the proliferation and promote the apoptosis of NB4-R1, which may be regulated through caspase-8-induced exogenous apoptosis pathway.