PPM1F and hepatocellular carcinoma: To elucidate the reason of PPM1F upregulation in HCC tissues, we investigated the alterations of PPM1F in genetic or epigenetic levels, and found little evidence about the dysregulation of PPM1F at the genetic (Additional file 2: Figure S1A and B) and methylation levels (Additional file 2: Figure S1C), indicating that genetic alterations and methylation modification could not account for the upregulation of PPM1F in HCC.