Gene Expression Signature of Acute Myeloid Leukemia (AML) with T(8;16)(P11;P13) and MYST3-CREBBPRearrangement: A Microarray Study Validated by Multiple Real-Time PCR.

AML with t(8;16)(p11;p13) is an infrequent leukemia subtype with characteristic clinical-biological features. The t(8;16)(p11;p13) translocation leads to the fusion of MYST3and CREBBPgenes, probably resulting in a disturbed transcriptional program of a myelo-monocytic precursor. In this study, the genetic signature of MYST3-CREBBPAML was compared with other well-defined AML subtypes. Genotypic analyses using oligonucleotide U133A arrays (Affymetrix) were performed on RNA of 23 AML patients, including three MYST3-CREBBPcases, PML-RARa(n=3), RUNX1-CBF2T1(n=3), CBFβ-MYH11(n=3), t(9;11)/AF9-MLL(n=1), monocytic AML (FAB M4/M5), n=8, and two cases of AML with multilineage dysplasia. Forty-six genes differentially expressed in MYST3-CREBBPcases were analyzed by multiple real-time RT-PCR using low-density arrays in an additional series of 40 patients, which included 7 MYST3-CREBBPcases, 18 AML samples with well characterized rearrangements (PML-RARa,n=3; RUNX1-CBF2T1,n=3; CBFβ-MYH11,n=3, MLL-rearranged AML, n=9), and 15 patients with normal karyotype AML. After unsupervised analysis, MYST3-CREBBPcases clustered together, displaying a distinctive expression signature. The analysis by RT-PCR confirmed the gene expression pattern found in the high-density array study. Thus, overexpressed genes included oncogene RET, several homeobox (HOXA9, HOXA10), genes involved in apoptosis (DAP)and prolactingene. In contrast, cyclinD2, STAT5A, STAT5Band WT1were underexpressed. Interestingly, MYST3-CREBBPcases showed up-regulation of a subgroup of genes (HOXA9, MEIS1, AKR7A2, CHD3, FLT3and APBA2)that were also found overexpressed in MLL-rearranged leukemias. In summary, this study showed the distinctive genetic signature of MYST3-CREBBPAML, which harbours some similarities with MLL-rearranged AML. In addition, the low-density array methodology validated the results of the microarray analysis and allowed to study a larger series of patients, including samples not suitable for microarray analysis.