Blastic plasmacytoid dendritic cell neoplasm: genomics mark epigenetic dysregulation as a primary therapeutic target

Blastic Plasmacytoid Dendritic Cell Neoplasm is a rare and aggressive hematological malignancy currently lacking an effective therapy. To possibly identify genetic alterations useful for a new treatment design, we analyzed by whole-exome sequencing fourteen Blastic Plasmacytoid Dendritic Cell Neoplasm patients and the patient-derived CAL-1 cell line. The functional enrichment analysis of mutational data reported the epigenetic regulatory program as the most significantly undermined (P<.0001). In particular, twenty-five epigenetic-modifiers were found mutated (e.g., ASXL1, TET2, SUZ12, ARID1A, PHF2, CHD8); ASXL1 was the most frequently affected (28.6% of cases). To evaluate the impact of the identified epigenetic mutations at the gene-expression and Histone H3 lysine 27 trimethylation/acetylation levels, we performed additional RNA and Pathology tissue-chromatin immunoprecipitation sequencing experiments; the patients displayed enrichment in gene-signatures regulated by methylation and modifiable by Decitabine administration, shared common H3K27-acetylated regions and featured a set of cell-cycle genes aberrantly up-regulated and marked by promoter acetylation. Collectively, the integration of sequencing data showed the potential of a therapy based on epigenetic agents. Through the adoption of a preclinical Blastic Plasmacytoid Dendritic Cell Neoplasm mouse model, established by the CAL-1 cell line xenografting, we demonstrated the efficacy of the combination of the epigenetic drugs 5'-Azacytidine and Decitabine in controlling the disease progression in vivo.