Recurrent 8q24 rearrangement in BPDCN: association with immunoblastoid cytomorphology, MYC expression, and drug response (CAL1 vs PMDC05)

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare skin-tropic hematological malignancy of uncertain pathogenesis and poor prognosis. We examined 118 BPDCN cases for cytomorphology, MYC locus rearrangement, and MYC expression. Sixty-two (53%) and 41 (35%) showed the classic and immunoblastoid cytomorphology, respectively. Forty-one (38%) MYC+BPDCN (positive for rearrangement and expression) and 59 (54%) MYC-BPDCN (both negative) cases were identified. Immunoblastoid cytomorphology was significantly associated with MYC+BPDCN. All examined MYC+BPDCNs were negative for MYB/MYBL1 rearrangement (0/36). Clinically, MYC+BPDCN showed older onset, poorer outcome, and localized skin tumors more commonly than MYC-BPDCN. MYC was demonstrated by expression profiling as one of the clearest discriminators between CAL-1 (MYC+BPDCN) and PMDC05 (MYC-BPDCN) cell lines, and its shRNA knockdown suppressed CAL-1 viability. Inhibitors for bromodomain and extraterminal protein (BETis) and aurora kinases (AKis) inhibited CAL-1 growth more effectively than PMDC05. We further showed that a BCL2 inhibitor was effective in both CAL-1 and PMDC05, indicating that this inhibitor can be used to treat MYC-BPDCN, to which BETis and AKis are probably less effective. Our data will provide a rationale for the development of new treatment strategies for patients with BPDCN in accordance with precision medicine.

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Sakamoto K, Katayama R, Asaka R, Sakata S, Baba S, Nakasone H, Koike S, Tsuyama N, Dobashi A, Sasaki M, Ichinohasama R, Takakuwa E, Yamazaki R, Takizawa J, Maeda T, Narita M, Izutsu K, Kanda Y, Ohshima K, Takeuchi K