Gene Expression Signature of Acute Myeloid Leukemia (AML) with T(8;16)(P11;P13) and MYST3-CREBBP Rearrangement: 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 MYST3 and CREBBP genes, probably resulting in a disturbed transcriptional program of a myelo-monocytic precursor. In this study, the genetic signature of MYST3-CREBBP AML 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-CREBBP cases, 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-CREBBP cases were analyzed by multiple real-time RT-PCR using low-density arrays in an additional series of 40 patients, which included 7 MYST3-CREBBP cases, 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-CREBBP cases 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 prolactin gene. In contrast, cyclinD2, STAT5A, STAT5B and WT1 were underexpressed. Interestingly, MYST3-CREBBP cases showed up-regulation of a subgroup of genes (HOXA9, MEIS1, AKR7A2, CHD3, FLT3 and APBA2) that were also found overexpressed in MLL-rearranged leukemias. In summary, this study showed the distinctive genetic signature of MYST3-CREBBP AML, 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.