Key Points: Dnmt3a ablation in HSCs predisposes mice to develop a spectrum of myeloid and lymphoid malignancies. Dnmt3a-KO-derived myeloid malignancies and T-cell acute lymphocytic leukemia/lymphoma show distinct methylation aberrations.

Anaplastic lymphoma kinase (ALK) constitutes a part of the oncogenic fusion proteins nucleophosmin-ALK and echinoderm microtubule-associated protein like 4-ALK, which are aberrantly expressed in a subset of T-cell anaplastic large-cell lymphoma and non-small-cell lung cancer, respectively. The expression of mutated, constitutively active ALK also occurs in a subset of neuroblastoma tumors. ALK is believed to play an important role in promoting tumor survival. Nevertheless, the mechanisms underlying the expression of ALK in cancer cells are not completely known. MicroRNA (miR) has been implicated in the regulation of the expression of both oncogenes and tumor suppressor genes. We tested the hypothesis that the expression of ALK could be regulated by miR. Three Internet-based algorithms identified miR-96 to potentially bind with the ALK 3'-untranslated region. Notably, miR-96 levels were markedly decreased in ALK-expressing cancer cell lines and primary human tumors compared with their normal cellular and tissue counterparts. Transfection of the cell lines with miR-96 decreased levels of the different forms of ALK protein, without significant effects on ALK mRNA. Furthermore, miR-96 decreased the phosphorylation of ALK target proteins, including Akt, STAT3, JNK, and type I insulin-like growth factor receptor, and it down-regulated JunB. These effects were associated with reduced proliferation, colony formation, and migration of ALK-expressing cancer cells. These data provide novel evidence that decreases in miR-96 could represent a mechanism underlying the aberrant expression of ALK in cancer cells. (Am J Pathol 2012, 180:1772-1780; DOI: 10.1016/j.ajpath.2012.01.008)

Table 1. Clinicopathologic features of patients with lineage-switching leukemia. Case # Sex Age at acute #1 Dx of acute #1 Tx of acute #1 Dz status of acute #1 at dx of acute #2 Dx of acute #2 Interval from acute #1 to #2 Tx of acute