RRM2 and infection: We interfered with the endogenous RRM2 expression by infection with RRM2 shRNA lentivirus, and quantitative (q) reverse transcription polymerase chain reaction (RT-PCR) results showed that the RRM2 expression was significantly downregulated in RRM2 shRNA lentivirus-infected MH7A cells compared to that of control shRNA lentivirus-infected cells (**p<0.01, Fig 2C).