Low expression of GFI-1 Gene is associated with Panobinostat-resistance in acute myeloid leukemia through influencing the level of HO-1

To improve the treatment outcomes of acute myeloid leukemia (AML), epigenetic modification has been widely tested and used in recent years. However, drug-resistance is still a choke point to cure the malignancy. The growth factor independent 1 transcriptional repressor (GFI-1), as a zinc-finger transcriptional repressor, can bind histone deacetylases to allow the transcriptional repression. According to the finding of our study, AML patients with low level of GFI-1 not only implicated poor prognosis but also caused Panobinostat-resistance. In our prevent study revealed that heme oxygenase-1(HO-1) was one of the main factors leading to chemotherapy sensitivity to AML. Thus, this study tried to test the correlation between GFI-1 and HO-1. Our study discovered that AML patients with lower expression of GFI-1 had higher level of HO-1, HDAC1, HDAC2 and HDAC3, which resulted in poor prognosis in AML. The results of the in vitro study were the same. Panobinostat is a promising new class of anti-cancer drugs in AML. However, knocking down GFI-1 by siRNA could eliminate the Panobinostat-induced cell apoptosis. Subsequently, we utilized ZnPP to down regulate the level of HO-1, finding that the Panobinostat-resistance between the low level of GFI-1 and empty vector had eased. After further exploring the mechanism, it could be found that with knock down GFI-1, the phosphorylation of Akt and PI3K could be activated. Subsequently, Akt pathway and HO-1 inhibitor were utilized respectively and the resistance was reversed. It suggested that the resistance of Panobinostat to AML cells at low level of GFI-1 was mainly due to up-regulated level of HO-1 through the PI3K-Akt pathway.