Overexpression of HHEX in Acute Myeloid Leukemia with t(8;21)(q22;q22) Translocation

The hematopoietically expressed homeobox (HHEX) is widely expressed in hematopoietic stem cells and is an essential transcription factor in embryonic development; however its role in hematopoiesis and leukemogenesis is poorly understood. We are thus exploring the association of HHEX and acute myeloid leukemia (AML).

The study included 56 AML patients and 12 normal bone marrows (NBMs). Real-time quantitative polymerase chain reaction (Q-PCR) was used to assess HHEX expression. The functional consequences of this gene were explored in the Kasumi-1 cell-line following dampened expression of HHEX. This was done by transfecting small interfering RNA (siRNA).

Expression levels of HHEX in AML were similar to that found in controls (0.094±0.103 vs. 0.078±0.112; p=0.203), but AML with t(8;21) was more prevalent than other types of AMLs (p<0.01) or controls (p<0.05). Expression levels of HHEX in AML (non-M3) did not significantly affect overall survival (p=0.555). In vitro studies carried out in Kasumi-1 cells suggest that after decreasing HHEX, cell viability at 48 and 72 h were significantly reduced compared to controls (p<0.05). The apoptotic rate was also significantly increased at 48 and 72 h compared to controls (p<0.05).

HHEX is expressed in multiple types of AML, with the highest levels seen in t(8;21) AML. HHEX was essential for Kasumi-1 cell proliferation and may represent a potential therapeutic target enabling against AML.