miR-17-92 cluster-BTG2 axis regulates B-cell receptor signaling in mantle cell lymphoma.

B-cell receptor (BCR) signaling is critically activated and stable for mantle cell lymphoma (MCL), but the underlying mechanism of the activated BCR signaling pathway is not clear. The pathogenic basis of miR-17-92 cluster remains unclear although the oncogenic microRNA (miRNA) miR-17-92 cluster is highly expressed in patients with MCL. We revealed that miR-17-92 cluster overexpression is partly dependent on SOX11 expression and chromatin acetylation of MIR17HG enhancer regions. Moreover, miR-17-92 cluster regulates not only cell proliferation but BCR signaling activation in MCL cell lines. To comprehensively identify miR-17-92 cluster target genes, we performed pulldown-seq, where target RNA of miRNA was captured using the biotinylated miRNA mimics and magnetic bead-coated streptavidin, and quantified using next-generation sequencing. The pulldown-seq identified novel miRNA target genes, including tumor suppressors such as BTG2 (miR-19b), CDKN2A (miR-17), SYNE1 (miR-20a), TET2 (miR-18, miR-19b, and miR-92a), TNFRSF10A (miR-92a), and TRAF3 (miR-17). Notably, the gene expression profile data of patients with MCL revealed that BTG2 expression was negatively associated with that of BCR signature genes, and low BTG2 expression was associated with poor overall survival. Moreover, BTG2 silencing in MCL cell lines significantly induced BCR signaling overactivation and cell proliferation. Our results suggest an oncogenic role of miR-17-92 cluster-activating BCR signaling throughout BTG2 deregulation in MCL. Furthermore, this may contribute to the prediction of the therapeutic efficacy and improved outcomes of MCL.

Triple targeting of RSK, AKT, and S6K as pivotal downstream effectors of PDPK1 by TAS0612 in B-cell lymphomas.

B-cell lymphomas (BCLs) are the most common disease entity among hematological malignancies and have various genetically and molecularly distinct subtypes. In this study, we revealed that the blockade of phosphoinositide-dependent kinase-1 (PDPK1), the master kinase of AGC kinases, induces a growth inhibition via cell cycle arrest and the induction of apoptosis in all eight BCL-derived cell lines examined, including those from activated B-cell-like diffuse large B-cell lymphoma (DLBCL), double expressor DLBCL, Burkitt lymphoma, and follicular lymphoma. We also demonstrated that, in these cell lines, RSK2, AKT, and S6K, but not PLK1, SGK, or PKC, are the major downstream therapeutic target molecules of PDPK1 and that RSK2 plays a central role and AKT and S6K play subsidiary functional roles as the downstream effectors of PDPK1 in cell survival and proliferation. Following these results, we confirmed the antilymphoma efficacy of TAS0612, a triple inhibitor for total RSK, including RSK2, AKT, and S6K, not only in these cell lines, regardless of disease subtypes, but also in all 25 patient-derived B lymphoma cells of various disease subtypes. At the molecular level, TAS0612 caused significant downregulation of MYC and mTOR target genes while inducing the tumor suppressor TP53INP1 protein in these cell lines. These results prove that the simultaneous blockade of RSK2, AKT, and S6K, which are the pivotal downstream substrates of PDPK1, is a novel therapeutic target for the various disease subtypes of BCLs and line up TAS0612 as an attractive candidate agent for BCLs for future clinical development.

[Agranulocytosis during therapy of chronic myeloid leukemia lymphoid blast crisis with dasatinib].

A 61-year-old female was diagnosed with a lymphoid crisis of chronic myeloid leukemia (CML) in February 201X and started chemotherapy combined with dasatinib (DAS). After 1 month of initiating second consolidation therapy, the neutrophils decreased to 1%, bone marrow examination revealed large granular lymphocytes (LGL) at 13%, and complete cytogenetic remission was attained (CCyR). Suspecting DAS-induced agranulocytosis, DAS was discontinued. After 2 weeks, LGL disappeared and neutrophils recovered. In this case, CCyR was attained for the first time when LGL increased. We considered that the expansion of LGL correlated with the clinical efficacy, and agranulocytosis was an off-target effect of DAS.

[Possible contribution of disseminated Mycobacterium shigaense infection to development of splenic marginal zone lymphoma].

A 73-year-old male who underwent splenectomy was diagnosed with splenic non-caseating granuloma in May 201X, and sarcoidosis was disregarded from the differential diagnosis. Owing to the persisting inflammation, the patient was carefully followed up with no treatment. Four months post splenectomy, the patient was hospitalized due to progressive dyspnea. Chest computed tomography revealed an encapsulated pleural effusion and lymphocytic infiltration in the left lower lung, with subclavian and mediastinal lymphadenopathy. Although the patient was treated with antibiotics, his condition showed no improvement; therefore, prednisolone 40 mg was administered, resulting in lung lesion improvement. A re-examination of the tissue obtained from the previously removed spleen revealed splenic marginal zone lymphoma (SMZL), a specific low-grade, small B-cell lymphoma. As a result, the patient was treated with rituximab combined with chemotherapy. During the fifth course of the chemotherapy, a subcutaneous abscess appeared in the cervical region, and Mycobacterium shigaense was isolated from the pus discharge, suggesting that the splenic granulomatous lesion formed due to M.shigaense, and dissemination of the Mycobacterium infection occurred following splenectomy and chemotherapy, when the patient was immunosuppressed. Overall, we consider that SMZL developed because of chronic inflammation resulting from a nontuberculous mycobacterial infection.